WAR SHIPPING ADMINISTRATIONTRAINING ORGANIZATION

GENERAL NEEDS OF SHIP'S PLANT PAGE 3FUNDAMENTALS OF ENGINEERING PAGE 5  HEAT PAGE 5  STEAM PAGE 7  STEAM AND WATER CYCLE PAGE 7  CONDENSER PAGE 10  FILTERTANK AND HOTWELL PAGE 10  FEED PUMP PAGE 11  FEED CHECK VALVE PAGE 11  AUXILIARY STEAM AND WATER CYCLE PAGE 13  AUXILIARY CONDENSER PAGE 14  CONSERVATION OF HEAT AND FUEL PAGE 16  FEED WATER HEATERS    OPEN TYPE PAGE 16    CLOSED TYPE PAGE 17  ECONOMIZERS PAGE 18  AIR PREHEATERS PAGE 18  GREASE AND OIL IN BOILERS PAGE 19    OBSERVATION TANK PAGE 19    FILTER BOX PAGE 19    GREASE EXTRACTOR PAGE 20  SEA WATER IN BOILERS PAGE 20    FOAMING PAGE 20    SCALE PAGE 20  FRESH WATER IN BOILERS PAGE 21  SCALE PAGE 21  WATER TREATMENT PAGE 21

  RESERVE FEED (EXTRA FEED) PAGE 21BOILERS PAGE 22  SIMPLE TYPE PAGE 22  SCOTCH MARINE PAGE 22  WATERTUBE PAGE 29DRAFT PAGE 38FUELS PAGE 40  COAL PAGE 40

 

    FUEL OIL PAGE 40OIL-BURNING INSTALLATION PAGE 42BURNING FUEL OIL PAGE 46SMOKE PREVENTION PAGE 52FIRE EXTINGUISHERS IN FIREROOM PAGE 53RAISING STEAM PAGE 54DUTIES OF A FIREMAN PAGE 55DUTIES OF A WATERTENDER PAGE 57THE WIPER'S JOB PAGE 58RECIPROCATING STEAM ENGINES PAGE 59  THRUST BEARINGS PAGE 72  LUBRICATION PAGE 73STEAM TURBINES PAGE 81  TYPES PAGE 82  REDUCTION GEARS PAGE 84  LUBRICATION PAGE 86DUTIES OF AN OILER PAGE 88PUMPS PAGE 89PUMPING SYSTEMS PAGE 97ELECTRICITY PAGE 99DECK MACHINERY PAGE 103STEERING ENGINES PAGE 105  TELEMOTOR PAGE 106PIPING SYSTEMS PAGE 107  STEAM TRAP PAGE 110  VALVES PAGE 110REFRIGERATION PAGE 113SAFETY PRECAUTIONS PAGE 115GLOSSARY OF ENGINE ROOM TERMS PAGE 116

ADAPTED IN PART FROM PUBLICATIONS OF THE CORNELL MARITIME PRESS

THE FOLLOWING PHOTOGRAPHS ARE SHOWN

THROUGH THE COURTESY OF

BABCOCK AND WILCOX COMPANY PAGES 30, 32COMBUSTION ENGINEERING COMPANY PAGE 36BAILEY METER COMPANY PAGE 37THE HAYS CORPORATION PAGE 39TODD SHIPYARDS CORPORATION PAGES 50, 51UNITED STATES METALLIC PACKING COMPANY PAGE 62KINGSBURY MACHINE WORKS PAGE 72GENERAL ELECTRIC COMPANY PAGE 81WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY PAGE 83AMERICAN HOIST AND DERRICK COMPANY PAGE 103AMERICAN ENGINEERING COMPANY PAGE 106

ALL OTHERS UNITED STATES MARITIME COMMISSION PHOTOS  

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GENERAL NEEDS OF SHIP'S PLANTS  

The first sight of a ship's power plant in operation is apt to be a fascinating spectacle of large whirling cranks; gleaming piston rods, sliding in and out of huge lofty cylinders, and of roaring fires in the furnaces. The maze of pipe lines and smaller machinery gives the impression of a complicated assembly requiring much time to understand. Nothing could be further from the truth, for the principles of operation are simple if followed step by step. In this manual the story of the ship's power plant unfolds in simple language.

The safety of the ship is dependent to a considerable degree on you Firemen, Watertenders and Oilers, for one of the most important needs of a ship's power plant is a well trained and competent engine room crew. The best machinery is no better than the men who operate it and care for it.

The members of the Engine Department with brief mention of their duties are listed according to their rank and authority.

LICENSED OFFICERS

  Watertender-Maintains proper water level in boilers and has charge of firemen. Stands watch in fireroom.

Fireman-Operates oil burning system to generate steam in boilers and on small and medium sized vessels also acts as watertender. Stands watch in fireroom.

UNLICENSED AND UNQUALIFIED MEMBER OF THE CREW

Wiper-Performs manual labor in engine department, such as cleaning and painting and assists in repair work. Works day work.

UNLICENSED MEMBERS CARRIED ON SOME VESSELS IN ADDITION TO

ABOVE

Machinist-Performs necessary machine repair work. Works day work.

Refrigerating Engineer-Operates and maintains refrigeration systems on refrigerator vessels.

Electrician-Carried on vessels which have

Chief Engineer-In charge of and responsible for all of the machinery aboard ship.

First Assistant Engineer-In charge of maintaining machinery in fireroom and engine room. Stands 4-8 watch.

Second Assistant Engineer-Responsible for fuel oil, fresh water and care of the boilers. Stands 12-4 watch.

Third Assistant Engineer-Maintains electrical equipment and auxiliaries under direction of the first assistant. Stands 8-12 watch.

Junior Engineer- (May or may not be licensed.) Stands engine room or fireroom watch under regular watch engineer on larger ships.

UNLICENSED QUALIFIED MEMBERS OF THE CREW

Deck Engineer-Keeps in repair all deck machinery, such as cargo winches, anchor windlass, etc. Works day work.

Oiler-Oils the bearings of the main engine and auxiliaries. Stands watch in engine room.

considerable electrical equipment.

Pumpman-Always carried on tanker vessels. Operates and maintains cargo pumps and valves.

Storekeeper-Keeps check on supplies and spare parts on large vessels.

The importance of the duties of each member of the crew cannot be overemphasized.

Should the fireman through neglect or ignorance allow the water level in the boilers to drop below the lowest safe point, serious damage may occur with resultant loss of use of the boilers and stoppage of the ship's engine.

Likewise, should the oiler burn up a bearing on the engine, the engine may have to be stopped for repairs.

These events are serious in that the stopped vessel would have to drop out of convoy making it easy prey for attack. A smoking stack may give away your position to the enemy and bring on attack.

It is therefore evident that these duties must be carried out by men who know their business. No one in training can afford to waste a single moment of the time, for your life may depend

 

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on what you know. Close attention should be paid to all lectures and practical work. The manual should be thoroughly read and understood and kept with you for reference when you go aboard ship.

The prompt execution of orders is an absolute necessity for safety of the vessel and crew. Delay in the closing or opening of a valve for example can result in serious damage.

  turn it. Various smaller machines are necessary for the operation of the main engine. If a steam engine is used, boilers will be required to furnish the steam for the engine. Fuel and a place to store a sufficient amount for a long journey is also required. Tools and spare parts for the various machinery must be aboard. Sufficient fresh water for the crew and plant's needs and a place to store it is necessary. It must be remembered that a ship is a virtual floating

MACHINERY AND EQUIPMENT

To propel the ship through the water a propeller is used at the stern. It must have an engine, either steam or internal combustion to

city which must be able to maintain itself and effect necessary repairs independent of any outside help for considerable periods of time.

 

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THE SUN IS THE SOURCE OF ALL ENERGY

FUNDAMENTALS OF ENGINEERING  

EXPLANATION OF HEAT

In operating the ship's power plant you will constantly be working with heat, in making it by burning coal or oil and in tending the engines wherein the heat made is turned into work. So it is important that the following simple facts and habits of heat be understood.

Heat is the source of all energy. Going further we find that energy is the ability to do work. Therefore all engines are heat engines because heat must be supplied before energy can be produced to turn the engine so that it can do useful work, such as turning the propeller of a ship.

The heat may be produced by burning fuel such as coal or oil. The larger and hotter the fire the more energy produced and the more

  principle, assume that the boiler is like a steel barrel in a horizontal position. Fuel is burned just below the boiler and the heat given off radiates against the outside of the boiler, and is conducted through the steel walls into the water. The heat then circulates throughout the boiler by convection currents until such time as the water has absorbed so much of the heat that it begins to boil and a vapor called steam is given off. Some of the heat from the fire is now in the steam, which is led to the cylinder of the engine through a pipe line. The heat in the steam produces in the cylinder the energy that pushes the piston downward and through a mechanical hook-up revolves the crankshaft in the same manner as the internal combustion engine. This method of supplying heat is known as external combustion. Temperature-The degree of heat is called temperature and is the number of degrees

work accomplished. To control the power of the engine we regulate the amount of fuel being burned. The burning of fuel is known as combustion.

Internal Combustion-In an internal combustion engine such as the gasoline or diesel engine the fuel in the form of light oil is burned directly inside the cylinder of the engine. The energy derived from the heat of the burning oil pushes the piston downward and through a mechanical hook-up revolves the crankshaft which in turn spins the propeller. This method of supplying heat to the engine is known as internal combustion.

External Combustion-In steam engines the heat is developed by the burning of the fuel in a boiler, separate from the engine.

The boiler is a closed steel vessel partially filled with water. To illustrate the

Fahrenheit of the steam or other substance considered. Fahrenheit is a graduated temperature scale widely used in this country. It is measured by a thermometer. The thermometer consists of a small glass tube one end of which opens into a glass bulb filled with mercury. If the bulb is placed in hot water or steam the mercury becomes heated and expands upward in the glass tube. The hotter the water or steam the higher the column of mercury will go, so that by reading the degree graduation on the frame along the mercury column, the temperature of the water or steam can be measured. Thermometers are located at various points in the fireroom and engine room and one of the duties of the firemen, watertenders

 

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and oilers is to interpret the meaning of the readings several times a watch. For high temperatures, such as the fire box of a boiler or smokestack, a pyrometer is used. A pyrometer works on the principle of expanding metal pushing against a hand on a recording dial.

  bent into an elliptical shape. A single tube Bourdon pressure gage is shown.

This consists of a single curved brass tube (A), one end of which is secured to the base of the casing (E), the other end being free to move. When pressure is admitted into the tube through connection (F), it tends to straighten out, causing the free end to move. This movement pulls on the lever (C), which turns the geared quadrant (B), through an arc of a circle. The quadrant meshes with a pinion on the pointer shaft, and moves the pointer (D) over a graduated scale showing the pressure acting in the tube. The greater the pressure the more the tube will straighten out, causing the pointer to indicate to a higher pressure reading on the graduated scale. The fireman reads the pressure in front of the pointer.

FAHRENHEIT THERMOMETER

Pressure-When dealing with the temperature of steam we must consider pressure, for when the temperature of steam increases or decreases so does the pressure. Pressure is a force of energy and is recorded in pounds per square inch. If a boiler is said to have a pressure of 200 pounds it means that a force of 200 pounds is pushing outward on every square inch of the inside boiler surface. Pressure is exerted equally in all directions throughout the steam and water spaces of the boiler. The pressure of a boiler is determined by the steam pressure gage.

PRESSURE GAGE

Steam pressures are usually measured by an instrument known as the Bourdon pressure gage, which consists of one or two brass tubes

BOURDON PRESSURE GAGE

Atmospheric Pressure-That pressure normally existing in the air. It is all around us pressing upon our bodies. At sea level, atmospheric pressure is 14.7 pounds per square inch, and is created by the weight of a column of air one inch square resting upon the earth. On the top of a high mountain the atmospheric pressure would be less, due to the column of air being shorter.

 

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Gage Pressure-The pressure registered on a pressure gage is above atmospheric pressure. For example if the gage pointer points to 10 pounds, the pressure in the boiler is 10 pounds greater than the atmospheric pressure, and is the kind of pressure always spoken of aboard ship.

Absolute Pressure-Gage pressure plus atmospheric pressure. In the above example if we add the gage pressure of 10 pounds to atmospheric pressure 14.7 pounds, we get 24.7 pounds absolute pressure in the boiler. This kind of pressure is rarely referred to aboard ship.

Vacuum-When atmospheric pressure is

  fuel oil is burned in nearly all American marine boilers today. A lesser weight of fuel oil will be required for a voyage than coal, making more room for cargo.

Boiling Temperature of Water-The temperature at which water will boil depends upon the pressure resting upon the surface of the water. At sea level with 14.7 pounds per square inch atmospheric pressure against the surface of the water, it will boil at 212° F., but if we were on top of the mountain it would boil at a lower temperature, perhaps 180° F. If we place the surface of the water under a greater pressure than atmospheric, a higher temperature will be required before the water will boil and give off steam. As an

removed from a closed vessel, such as a steel tank, a vacuum is left. The more atmospheric pressure removed, the greater the vacuum. A perfect vacuum is attained only when all atmospheric pressure is exhausted, and is practically impossible to achieve. The amount of vacuum is registered on the vacuum gage which operates on the same principle as a pressure gage except that the face is graduated in inches instead of pounds. Each two inches of graduation being equal to one pound absolute pressure, 29 inches of vacuum would be a nearly perfect vacuum.

British Thermal Unit-"B. T. U."-Heat has a unit of measure just as liquids are measured by quarts or gallons. The heat unit known as the British Thermal Unit or "B. T. U." is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit. It is also equal to 778 foot pounds of work. Different kinds of fuel do not contain the same amount of heat. For instance, a pound of coal may contain 14,000 "B. T. U.s" while a pound of oil contains 19,000 "B. T. U.s". A pound of oil then will make more steam than a pound of coal. This is one of the reasons why

example: A boiler containing a pressure of 450 pounds per square inch would require a temperature of approximately 460° F. before the water would boil.

Saturated Steam-Steam that is in direct contact with and has the same temperature as the water from which it was formed. It is steam which at a given temperature always has a given pressure. Saturated steam can be either wet (moisture particles in it) or dry (containing no moisture).

Superheated Steam-Saturated steam that has been passed through a superheater which increases its temperature but not its pressure. This steam contains more heat than saturated steam and therefore can do more work. It contains no moisture particles and is used in modern reciprocating and turbine engines.

THE STEAM AND WATER CYCLE

The flow of the steam and water through the various pieces of machinery that make up the main engine power plant is known as the steam and water cycle.

The operation of a steam power plant depends upon water for conversion into steam by applying heat. A simple method would be to assume,

SIMPLE CYCLE-USING SEA WATER  

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in the first figure, that the boiler is filled with sea water to its proper level. As the fuel burns

  having the ability to force water into the boiler against the boiler pressure. In this

beneath the boiler, the water inside is heated until it boils and gives off steam which accumulates in the upper part of the boiler. The steam leaves the boiler at the top through the main stop valve and then flows through the main steam line to the throttle valve on the engine. When the throttle valve is opened the steam flows into the cylinders of the engine, causing it to do work. When the steam has done its work in the engine it must exhaust from the cylinders to make room for more live steam to enter. In this particular cycle the steam exhausts to the atmosphere and is lost. As the water in the boiler is changed into steam, it must be replaced or the boiler will run dry. This is done by means of a feed pump, which is a mechanical device

particular cycle the pump takes its suction from the water surrounding the ship. This would not do for ocean-going power plants due to the impurities in sea water which would damage the boiler. Where this cycle can be used, it has the advantage of requiring a minimum amount of machinery. In the next figure, it can be seen that a fresh water storage tank has been added to the cycle. With this hook-up the feed pump is pumping nothing but fresh water into the boiler to replace the water being boiled away. This cycle is an improvement over the first, however, it has certain disadvantages which make it unfit for ocean-going vessels. As fresh water is being continually pumped into the boiler, an

SIMPLE CYCLE-USING FRESH WATER WITH CONDENSER  

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enormous supply of fresh water would be required aboard the ship when starting on a long journey. Otherwise, it would be necessary to make fresh water from sea water, which is a very costly process and usually only resorted to in an emergency. Also, raw fresh water contains various solids in varying degree which accumulate in the boiler when the water is boiled off, and in time will harm the boiler unless carefully treated and cleaned. Small craft, such as Harbor Towboats, quite often use this type of system because they never venture far from shore and can refill their fresh water storage tanks at frequent intervals. The third figure is the steam and water cycle actually found aboard ocean-going vessels. The steam is produced from fresh water and flows to the main engine in the same manner. When the steam exhausts from the engine, however, it enters a condenser, where the exhaust steam is condensed back into fresh water. This fresh water is known as condensate and is removed from the condenser along with any air present, by the air and condensate pump. This pump then discharges the condensate into the feed and filter tank, where any lubricating oil which may have entered the condensate through lubrication of the main engine is removed, as

  far as possible. This tank also serves as a small storage tank for the feed pump. The feed pump takes the condensate (now known as feedwater) from the feed and filter tank and discharges it through a grease extractor, and a feedwater heater back into the boiler. The purpose of the grease extractor is to remove any oil from the feedwater which may have succeeded in passing through the filter tank. It is extremely important, as will be pointed out later, that no oil be allowed to enter the boiler. The feedwater heater increases the temperature of the water entering the boiler considerably, thereby effecting a considerable saving in fuel. It will also be noted that the feedwater passes through a feed check valve and feed stop valve just before entering the boiler. The check valve is a one-way valve allowing the feedwater to enter the boiler, but preventing its return. It also regulates the amount of water entering the boiler. It can be seen that with this system, the fresh water leaving the boiler in the form of steam returns in the form of water after the heat in the steam has done its work in the engine. If there were no loss of water from the system, it would never be necessary to add any raw fresh water, but in actual practice there is always some loss due to leaks, etc. It is, therefore, necessary from

SURFACE CONDENSER

 

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time to time to add fresh water from the ship's storage tanks. One great advantage of this cycle is, of course, the ability to use the same water over and over, effecting an enormous saving of fresh water. Another advantage is that the condensate is practically the same as distilled water and contains no solids to harm the boiler. The heat in the exhaust steam, which was lost entirely in the other cycles due to the engine exhausting into the atmosphere, is in small part returned to the boiler with the condensate. The disadvantage of this system is that it requires more machinery than those where the engine exhausted to the atmosphere, but the great saving in fresh water and considerable saving in fuel and more trouble-free boiler operation far outweighs the cost of the additional equipment.

CONTINUATION OF CYCLE

Condenser-The condenser was included in the cycle for the purpose of changing the steam, exhausting from the engine, back into water. There are three types of condensers: jet, keel and surface.

In jet condensers fresh water is sprayed into the exhaust steam, thereby condensing it. As fresh water must be plentiful for this kind of operation, jet condensers are used only on ships sailing fresh water lakes or rivers.

A keel condenser consists of piping beneath the ship's bottom, into which the exhaust steam passes. The water flowing around the outside of the pipes cools them and condenses the steam inside. This condenser is not used on ocean-going ships.

The surface condenser is the type generally found in marine power plants and is shown in cross section. The condenser is constructed in the form of a cylinder, being round or elliptical shaped, with flat heads at each end.

  The tubes are kept cold by pumping sea water through them continuously. The sea water enters the condenser through the inlet into the lower half of the divided water box and then flows through the lower bank of tubes into the water box on the opposite end. It then flows upward as indicated by the arrow, and enters the upper bank of tubes through which it passes into the upper half of the divided water box. The sea water then leaves the condenser through the outlet and is discharged overboard.

The temperature of the sea water leaving the condenser will be higher than when entering, as some of the heat in the exhaust steam is picked up by the sea water in passing through the tubes. This type of surface condenser is known as a "two-pass" because the sea water flows in two directions, being reversed in its travel through the tubes.

The tubes are made of either admiralty metal or brass and are secured tightly in the tube sheets at each end. This prevents the sea water from entering the fresh water space. Should the tubes leak, sea water will enter the fresh water side and contaminate the condensate.

The shell is generally made of cast iron or steel plate, the water boxes of cast iron.

Condensate Pump-The condensate is removed through the bottom by means of a pump known as the condensate pump. A pump is a mechanical device having the ability to transfer liquids or gases from place to place. It may be operated from the main engine or it may be of a type which operates by itself, but at any rate it must be able to operate continuously while the plant is in service, so as to remove the condensate from the condenser as fast as formed. The condensate is discharged from the pump into the combined filter tank and hotwell, which is

As for size, the outside measurement might be 7 feet long by 4 feet 6 inches diameter. The exhaust steam enters the condenser through the top of the shell where it strikes the steam baffle plate which spreads the exhaust steam throughout the condenser. As the exhaust steam passes downwards around the hundreds of small tubes, it is condensed into water by coming in contact with the cold tubes. This works on the same principle as steam vapor striking against a windowpane on a cold day. The condensate, being heavier than the exhaust steam, falls to the bottom of the condenser and is removed through the condensate pump suction.

also known as feed and filter tank.

Hotwell-In the cross-sectional side view of a common type filter tank and hotwell, section (L) is the hotwell. The condensate enters at (A), and after passing through the filter box, spills over into the hotwell (L). The hotwell serves as a small storage tank from which the feed pump takes its suction. The condensate is removed from the bottom of the hotwell by the feed pump through the opening (M).

The problem is to regulate the speed of the feed pump so that it will remove the water from the hotwell at exactly the same speed as it enters from the condensate pump. This is accomplished by means of the float control (N). As the water level rises and falls in the hotwell (L), the float (N) floats up and down on the surface

 

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FILTER TANK AND HOTWELL  

of the water like a rubber ball. The float is fastened to an arm which has a counterbalance weight (O) on the opposite end. This arm pivots like a see-saw at (P). As the arm moves up and down it moves the vertical rod which is fastened to the steam valve that controls the speed of the feed

  the feedwater from the filter tank and hotwell to the boiler, a feed pump must be able to force the feedwater into the boiler against the boiler pressure, which in some boilers is several hundred pounds per square inch. At least two feed pumps, known as the main and auxiliary, respectively, are required; one

pump. In this way, when a large amount of water suddenly enters the hot-well, such as when the engine is speeded up, the float control automatically speeds up the feed pump, removing the water more rapidly from the hotwell, preventing its overflowing. Should condensate stop entering the hotwell, as when the engine is stopped, then the float will drop down, shutting off the steam to the feed pump, stopping it and preventing the hotwell from being pumped dry.

The level of the water in the hotwell can be seen by looking at the water gage glass (Q).

The temperature of the condensate may be determined by reading the thermometer (R).

In case the hotwell should for any reason become full, it will overflow through the pipe line (S) which leads to one of the ship's fresh water storage tanks.

The filter tank and hotwell is usually a rectangular shaped box made of steel plate having a removable cover (U) to permit cleaning. When cleaning becomes necessary, all the water may be drained into the bilge by opening the drain valve (T).

(V) is an open vent pipe.

Feed Pump-In addition to being able to move

being in use while the other stands by, ready for instant service.

It is important that there always be a feed pump in operation while the boiler is in service, otherwise the water level in the boiler will quickly drop below the lowest safe point, resulting in overheating of the boiler metal unless it is immediately removed from service.

Feed pumps may be of the steam reciprocating type or centrifugal type. The latter may be driven by a steam turbine or electric motor.

Upon being discharged from the feed pump, the feedwater passes along the feed line through the grease extractor, feedwater heater, feed check valve, feed stop valve and into the boiler.

Feed Check Valve And Its Relation To Boilers In Battery-The feed check valve is located in the feed line near the boiler, between the feedwater heater and the feed stop valve. It is a one-way valve, and one of its purposes is to prevent the feedwater from returning through the feed line once it has entered the boiler.

The cross-sectional view is of a simple feed check valve of a type used aboard ship. The body (G) of the valve is made of bronze or cast steel. The feedwater enters the valve through the feed line from the feedwater heater at (A)

 

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and flows downward and then turns up against the bottom of the movable disc (B) which acts as a plug to close the opening. When the pressure of the entering feedwater against the bottom of the disc becomes greater than the pressure within the boiler pushing downward on the top, the disc lifts. This leaves an opening through which the feedwater flows to discharge at (D) to the stop

  If the hand wheel is turned counterclockwise (to the left), the valve stem is screwed upward, leaving a space between the top of the disc and the bottom of the valve stem. This is the open position, as the disc is free to open and close with the incoming water.

valve and boiler. When the incoming pressure drops below the boiler pressure, the pressure on the top of the disc becomes greater, causing the disc to drop, close the opening and prevent the water in the boiler from flowing backwards into the feed line.

FEED CHECK VALVE

The bottom end of the valve stem (C), which is threaded in the valve yoke (F), is not attached to the disc (B). When the valve wheel (E) is turned clockwise (to the right) the stem screws downward until the bottom end of the valve stem is against the top of the disc. With the stem in this position the disc cannot be raised by the incoming water pressure, due to the valve stem holding it on its seat. This is closed position; no water can enter boiler.

BOILERS IN BATTERY

Another purpose of the check valve is to control the amount of water entering each boiler. As all ocean-going ships have more than one boiler, it is necessary to have a check valve in the branch feed line to each boiler. In this figure, three boilers are being operated in battery (together). Feed pump (A) pumps feed-water to all the boilers, the feedwater traveling through the feed line branching off to each boiler.

The water level in all three boilers must be kept as nearly equal as possible, even though at times the fires in the different boilers do not give off the same amount of heat. With the check valve on each boiler wide open, the water level in the boiler with the least fire would rise, as less water in the form of steam is leaving that boiler. For example: Suppose that No. 1 boiler has a less fire than boilers No. 2 and 3. With all check valves wide open, No. 1 boiler would soon become flooded. This is prevented by closing in on the check valve on No. 1 boiler, which consists of screwing down on the valve stem. This allows the valve disc to raise a small amount to allow just enough water to enter the boiler to maintain the proper water level. The remainder of the feedwater enters boilers 2 and 3 through the wide open check valves.

As the firing conditions in the boilers vary from time to time during the watch, it is necessary for the watertender to frequently adjust the check valve on each boiler in maintaining proper water level.

At least one check valve must be left open at all times, otherwise excess pressure will build up and damage the feed pump or feed line when the feed pump continues to operate with no opening for the feedwater to

discharge through.

On the larger ships the check valves are adjusted by the watertenders, while on medium and small-sized ships the fireman quite often tends the water.

 

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The feed stop valve (C) for each boiler is located in the feed line between the check valve (B) and the boiler. A stop valve is of the same general construction as a check valve except that the disc is fastened to the bottom of the valve stem, and when the valve stem is screwed upward the disc moves with it and is held open until the valve stem is screwed down by hand.

The purpose of the stop valve is to prevent the water in the boiler from backing out the feed line in the event the check valve should fail. This valve is ordinarily open at all times when the boiler is operating, except in the event of failure of the check valve, when it would be closed by hand.

When the boiler is shut down the stop valve is closed and is left closed until such time as the boiler is returned to service.

THE AUXILIARY STEAM AND WATER CYCLE

Before the main steam and water cycle can operate, a number of smaller pieces of machinery must be provided. Also additional machines are necessary to make the ship livable and to make possible the many other operations carried on, such as loading and unloading of cargo. These machines are known as auxiliaries and the manner in which steam is supplied to them is known as the auxiliary cycle.

The upper drawing on page 15 shows the auxiliary steam lines (broken lines) running from the boilers to the various steam-driven

 

BACK PRESSURE SYSTEM

Back pressure is the pressure of the steam in the auxiliary exhaust line. This auxiliary exhaust steam has exhausted from the various auxiliary steam engines driving pumps, electric generators, steering engine, winches, etc. It flows through the auxiliary exhaust line to the feedwater heater, condenser and atmosphere valve. Instead of allowing all of it to enter the condenser, wasting the heat it contains, the steam enters the feedwater heater. Here the heat in the exhaust steam is transferred to the feedwater before it enters

auxiliary machines in the fireroom and engine room of a Liberty Ship. It will be noted that beside the auxiliary stop valve connection on each boiler, there is an auxiliary steam line connection from the rear of each boiler. These connections are to supply superheated steam to the auxiliaries, instead of saturated, should it be desired.

The lower drawing shows the auxiliary exhaust steam lines (dotted lines) in the Liberty Ship fireroom and engine room.

The steam leaves the boiler through the auxiliary stop valves and flows through the auxiliary steam line to all parts of the ship, branching off to the various auxiliaries.

The steam-driven fan supplies air to the fire boxes of the boilers so that the fuel may burn.

The fuel service pumps pump the fuel oil under pressure to the oil burners in the boilers.

The fuel oil heaters are where the heavy fuel oil is heated to thin it so that it will burn.

The fire pump is required on every ship to pump sea water for fire-fighting purposes.

the boiler, thereby saving fuel.

The temperature of steam depends upon its pressure. To heat the feedwater to the highest practical temperature, the pressure of the auxiliary exhaust steam must be kept between 15 and 20 pounds. This pressure is controlled by the back pressure valve restricting the flow of exhaust steam into the condenser. The valve must be adjusted from time to time during a watch to maintain the desired back pressure.

 

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The sanitary pump is used to pump sea water to the various toilets.

The fresh water pump is used to pump fresh water to the crew's quarters, galley, etc.

The electric generators are where electricity for lighting and power is produced.

The refrigerating system is for the purpose of maintaining the perishable food of the ship.

The steering engine (not shown) steers the ship.

  condenser cannot be used when the main engine is idle, such as in port. Then the auxiliary condenser is operated and the exhaust steam enters through the back pressure valve and stop valve. The hand-operated back pressure valve on the main condenser would then be closed to prevent the auxiliary exhaust from entering.

Auxiliary Condenser-The construction of the auxiliary condenser is the same as the main condenser outlined on page 9, except that it is considerably smaller, as the amount of steam exhausting from the auxiliaries is

The anchor windlass (not shown) raises the ship's anchor when getting underway.

There are several cargo winches (not shown) for loading and unloading cargo.

The steam-driven combination circulating and condensate pump supplies sea water to the auxiliary condenser for cooling and removes the condensed steam and air from the condenser, leaving a vacuum.

The main circulating pump pumps the sea water through the main condenser for the purpose of condensing the exhaust steam.

The feed pumps pump the feedwater into the boilers.

The single dotted lines represent the auxiliary exhaust line which conducts the exhaust steam from the auxiliaries to the feedwater heater, the main condenser, the auxiliary condenser and the atmosphere valve.

It will be noted that the steering engine has a separate exhaust line leading direct to the main condenser. The reason for this will be taken up later.

As previously mentioned, the purpose of the feedwater heater is to increase the temperature of the feedwater before it enters the boiler. This is accomplished in the heater by transferring the heat in the auxiliary exhaust steam to the feedwater.

A pressure of from 15 to 20 pounds is maintained in the auxiliary exhaust line and feed-water heater. This is known as back pressure and is regulated by the automatic back pressure regulating valve. When the amount of auxiliary exhaust becomes sufficient to increase the back pressure above 20 pounds, the back pressure valve automatically opens, allowing the excess exhaust steam to flow into either the main condenser or auxiliary condenser, depending upon which one is in service. When the

not as great as that from the main engine.

The auxiliary condenser can be used only for condensing the exhaust steam from the auxiliaries. In other words, in the event of failure of the main condenser the main engine could not exhaust into the auxiliary condenser.

The auxiliary condenser has its own independent steam-driven circulating pump which continuously pumps sea water through the tubes. It also has its own condensate pump which continuously removes the condensate from the condenser and discharges it into the feed and filter tank. The pumps are located in a horizontal position below the auxiliary condenser. To operate the pumps a steam cylinder with piston is located between them. The piston of each pump is connected to the steam piston by piston rods. When steam is admitted to the steam cylinder, the moving piston operates both pumps.

The auxiliary condenser is ordinarily only operated in port, because at sea the main condenser is sufficiently large to take care of both the main engine and auxiliary exhaust. The usual practice is to place the auxiliary condenser in operation when approaching the pilot station or anchorage of the port at which the ship is to tie up. The reason for this is that the main condenser on many ships becomes at least semi-inoperative when the main engine is stopped for intervals, such as to pick up the pilot and maneuvering the engine when docking. As soon as the ship is tied up and the main engine is secured, the main condenser is shut down, as there will then be no exhaust steam entering it. The auxiliary condenser continues to operate while in port and until the ship is again at sea, when the main engine may be expected to operate continuously. Then the exhaust from the auxiliaries will be directed into the main condenser by opening the back pressure valve, and the auxiliary condenser will be

auxiliary exhaust enters the main condenser, it is condensed along with the exhaust from the main engine, and is returned to the boilers through the feed and filter tank, feed pumps, and feedwater heater as in the simple cycle shown on page 8.

In many marine power plants the main

secured.

Should the auxiliary condenser fail in port, the auxiliary exhaust may be discharged into

 

15 

 

16 

the atmosphere (air) at a point aft of the smoke-stack by opening the atmosphere valve. This arrangement is used when the ship is in dry dock as there is then no sea water surrounding the ship for cooling the auxiliary condenser.

CONSERVATION OF HEAT AND FUEL

Operation-As ocean-going ships must in many instances travel thousands of miles between ports, a considerable amount of fuel must be stored aboard, as ordinarily no additional fuel can be secured at sea. Today, under war-time conditions, the securing of fuel in foreign ports is sometimes uncertain, so that ships may have to carry sufficient fuel to return to their home port without refueling en route. The ship may have to go considerably out of its way to effect a rescue. Stormy weather with heavy seas and head winds results in an increased amount of fuel burned. Any of these occurrences means the burning of more fuel than anticipated. It is evident then that the ship cannot afford to waste fuel if it is to be in a position to meet all emergencies and still make port. In view of this the conservation of fuel becomes an important matter and is constantly in the minds of the engineers and crew members.

The fireman has a large control over the amount of fuel burned. A competent wide-awake fireman who cleans the oil burners regularly, maintains the proper amount of draft and keeps the fuel oil temperature at the degree most efficient for burning, has made sure that he has done his part in burning the least amount of fuel possible. On the other hand, an ignorant or careless fireman will be the direct cause of consuming many barrels of additional fuel each day. The watertender can likewise cause the unnecessary burning of fuel by the improper handling of the feed check valves, allowing feed-water to enter the boilers in large amounts rather than keeping

  general types of feedwater heaters, open and closed.

OPEN TYPE DEAERATING FEEDWATER HEATER

Open Type-The open type is used with power plants of higher pressures employing turbine engines. As the name suggests, the heater is open to the atmosphere, and therefore must be located in the cycle between the condensate pump and the feed pump, as there is no pressure in the cycle at this point.

The cross-sectional view is of a deaerating type open feedwater heater. In addition to increasing the temperature of the feedwater, this type open heater removes any air which may be present in the feedwater. Air contains oxygen, which if allowed to enter the boiler in any quantity, will cause a rapid wasting of the metal surfaces. Modern high pressure boilers are especially susceptible to this and for this reason the deaerating type of open feedwater heater is regularly used with high pressure systems.

This type heater may be made of cast iron or steel.

Feedwater from the condensate pump enters through the water inlet (A) where it is led to the center of the heater and sprayed upward from a nozzle in a fine spray. Steam at low pressure enters the heater through the steam

the water level steady by frequent and small adjustments of the check valves.

Keeping the boiler tubes free of soot accumulation is another insurance against the burning of unnecessary fuel.

Feedwater Heaters-The purpose of all feed-water heaters is to raise the temperature of the feedwater as high as possible before entering the boilers, so that less fuel will be required to make the water boil. In addition, cold water entering a boiler places a strain upon the metal parts, which must be avoided. There are two

inlet (B) and is also led to the center of the heater, where it is allowed to shoot out into and mix with the spray. This produces a scrubbing action which separates the air from the water and increases the temperature of the water. The water then falls to the bottom of the heater where it flows to the feed pump. The air and any other gases which may have been liberated from the feedwater, escape to the atmosphere through air outlet (C) on the vent condenser. The vent condenser is merely a small surface condenser in which steam vapors seeking to escape through the air outlet are condensed

 

17 

upon coming in contact with the tubes, made relatively cold by the incoming feedwater which flows through them.

The feedwater temperature in this type heater cannot be increased above the normal boiling point of water which is 212° F. In actual operation the temperature of the feedwater leaving the heater will probably not exceed 200° F.

Closed Type-Closed feedwater heaters are installed in practically all marine power plants and are located in the cycle between the feed pump and the boiler. As this portion of the cycle must be under a pressure greater than the boiler pressure, the heater must be closed, otherwise the feedwater would shoot out into the fireroom.

This cross-sectional view is of a closed feed-water heater of popular modern design, with control valves.

The feedwater enters the heater from the feed

  pump through feed line (A) and inlet valve (B) into water chamber (C). The feedwater then flows through the copper coils (D) , discharging into the water chamber (E). It then flows upward and enters the upper group of copper coils (F). After flowing through these coils the feed-water exits into the water chamber (G) and then proceeds to leave the heater through outlet valve (H) and continues on its way to the boiler through the feed line (I).

The temperature of the feedwater leaving the heater should be about 100° F. higher than when it entered. For example: The inlet temperature might be 140° F. while the outlet temperature then should be about 240° F. Now let us see what caused the increase in temperature.

As the feedwater was flowing through the copper coils, exhaust steam from the auxiliary exhaust line was entering the top of the heater through opening (K), at about 20 pounds back

CLOSED TYPE FEEDWATER HEATER  

18 

pressure and traveling downward, completely surrounding the coils. The heat in the exhaust steam was conducted through the walls of the copper coils into the feedwater, increasing its temperature about 100° F. in its travel through the coils.

The temperature of the feedwater before entering the heater may be found by looking at the thermometer on the hotwell and, after being heated, by the thermometer on the feed line between the heater and the boiler.

The purpose of the back pressure valve should now be clear.

As the heat is removed from the steam, the steam condenses and falls to the bottom of the heater (0) where it is drained as rapidly as formed through drain (L) which leads to the

  on the front of the heater may be removed and the broken coil replaced with a new one. The heater may then be closed up and returned to service.

While this is going on, the fireman on watch has found it necessary to burn considerably more oil in order to hold the desired steam pressure while the heater was out of service.

Economizers-In modern high pressure marine power plants the temperature of the feedwater is raised still higher before entering the boiler proper by passing the feedwater through an economizer after it leaves the closed feedwater heater. An economizer consists of a number of small steel tubes which are located in the uptake from the boiler.

filter tank and hotwell by gravity. To prevent the exhaust steam from blowing out the drain with the condensate and being wasted, a steam trap is installed in the drain line. The construction of this device will be discussed later.

The shell (N) of a heater of this type is made of steel.

A relief valve adjusted to open at about 25 or 30 pounds per square inch pressure is installed at the top of the steam space to prevent the back pressure from rising above that pressure.

The level of the condensate collected in the steam space surrounding the coils can be determined by looking at the gage glass (M).

Occasionally one or more of the copper coils will crack or break off while in service, being especially likely to happen when the coils have seen considerable service or when the feed pump is allowed to slam while operating. When a coil breaks, the feedwater immediately shoots out into the steam space surrounding the coils and if allowed to continue would completely fill this part of the heater and flood the auxiliary exhaust line. As soon as a coil breaks, the feed pump speeds up tremendously as it no longer is pushing against the boiler pressure. This is immediately noticeable and the pump must be stopped. To resume pumping water into the boiler the feedwater heater by-pass valve (J) is opened and the heater inlet valve (B) and outlet valve (H) are closed. The feed pump is then started up and the feedwater will flow from the pump through the feed line (A) and then turn upward, passing through the by-pass valve (J) and on into the feed line (I) to the boiler. When the shut-off valve in the auxiliary exhaust line entrance (K) to the heater is closed, the heater will be entirely isolated and the inspection door

ECONOMIZER

This cross-section view is of a single economizer tube in an uptake. In a boiler where a steam pressure of 450 pounds per square inch is carried, the temperature of the gases leaving the boiler on their way to the stack would probably be around 600° F. and if allowed to escape up the stack all of this heat would be wasted. By placing an economizer in the path of the gases a portion of the heat is returned to the boiler. This is accomplished by passing the feed-water through the economizer tubes which are surrounded by the hot flowing gases. Some of the heat in the gases is conducted through the walls of the steel tubes into the feedwater with which it is carried into the boiler.

The feedwater enters the tube through the inlet header (A) and then flows through the tube (B) discharging into the outlet header (C) from whence the feedwater discharges into the boiler through the check and stop valves at a considerably higher temperature than when it entered.

Economizers are not warranted on lower pressure boilers, meaning around the pressure of 250 pounds per square inch or lower, as the temperature of the escaping gases is not sufficiently high.

Air Preheaters-As a further conservation of fuel in high pressure boilers, air preheaters

 

19

  are sometimes installed. They also consist of a number of steel tubes located in the uptake, being just above the economizer tubes. The air from the blower to the fire box passes through the tubes, picking up some of the heat of the gases which escaped the economizer and carrying it into the fire box. The blowing of hot air into a fire box generally results in better burning of the fuel than cold air.

High pressure boilers equipped with economizers and air preheaters are found to be very efficient in operation. By efficiency is meant, a large portion of the heat produced by the burning fuel is turned into steam and only a small portion is lost up the stack.

FEEDWATER-GREASE AND OIL IN THE WATER SIDE OF BOILERS

Results-Even a small amount of grease or oil in the feedwater is very apt to cause overheating if it enters the boiler, as it is apt to circulate with the water and may adhere to a tube or plate located near the fire.

When steel is exposed to fire it cannot retain its strength unless the plate or tube is cooled by water on the opposite side. As boilers are made of steel, it is vitally important that the water side be kept free of any substance which might prevent the heat entering the steel from passing through into the water.

Grease and oil are very poor at transferring heat and even a thin coating in a water tube is sufficient to cause the steel to overheat, losing its strength, which allows the boiler pressure to bulge the area until it bursts like an inflated toy balloon.

Overheating from grease or oil can also cause steel furnaces to collapse and tubes and seams to leak where joined.

At best it means a boiler shut down for repairs, which in most cases are lengthy and expensive. At worst the overheating may result in a boiler explosion, which is very

  and the cylinder walls and to the piston rods which travel in and out of the cylinders. As the oil is in direct contact with the steam, some of it, especially if an excessive amount is used, travels along with the steam into the main condenser and then on with the condensate through the condensate pump into the feed and filter tank.

Another possible source of oil entry into the feedwater is through the fuel oil heaters. In these, live steam is used to increase the temperature of the oil and should a leak occur between the oil and steam side of the heaters, the fuel oil will enter the steam side and return through the drain line to the feed and filter tank with the condensed steam. As a safeguard against this, an observation tank is provided in most installations.

Observation Tank-Usually consists of a small square steel tank open to the atmosphere, located in the fuel oil heater condensate drain line, between the heater and the filter tank. The condensate entering the observation tank from the heaters is easily visible through a glass port, and at the first sign of fuel oil the condensate is drained to the bilge instead of the filter tank until repairs are made.

Fuel oil may also enter the feedwater through leaky heating coils located in the fuel oil storage tanks. The condensed steam from these also passes through the observation tank.

Filter Box-To remove the grease and oil from the feedwater, the filter tank portion of the combined filter tank and hotwell is provided. In the drawing on page 11, the condensate from the main engine enters the filter tank at (A) while the condensate from the observation tank enters at (W). In compartment (B) the condensate travels downward, passing beneath the vertical baffle and then rises upward through (C), where it overflows into compartment (D) and passes downward through a perforated steel plate

disastrous, resulting in probable loss of life and ship.

Constant care must be exercised to prevent the entry of oil into the boiler. Notify the engineer immediately at the first sign of grease or oil floating on the surface of the water in the water gage glass. Steps can be taken to remove the oil or neutralize its effects if detected in time.

Entry-The greatest danger of oil entry exists in marine power plants using reciprocating type main engines and auxiliaries. With these, lubricating oil must be supplied to the cylinders to provide lubrication between the moving pistons

into compartment (E) which is filled with a filtering material.

Several kinds of filter material can be used-one of the most popular being loofa sponges, which are secured from the inside of gourds. When dry, they are flat and about the size of a man's hand, but when immersed in water they swell up considerably. Turkish toweling and coke may also be used to remove oil from water. In operation, the grease and oil clings to the filter material while water passes through, and if the material is renewed or cleaned before it becomes saturated with oil, no oil will reach the boilers. It is, therefore, important that the

 

20 

filtering material be carefully watched and replaced as it becomes necessary.

Continuing with the flow of water through the filter tank, it passes downward into compartment (F) and then upward between the vertical baffles overflowing into compartment (H), where it passes downward through (I), which is another compartment filled with filtering material, and then down into (J) and up through (K) where it overflows into the hot-well (L).

The top of the shaded area represents the water level in the filter tank.

As oil tends to float on the surface of water, a large portion of the oil is trapped on the surface in compartments (B), (D) and (H), and can be skimmed off by hand as it collects.

Grease Extractor-To catch any oil in the feed-water which may have passed through the filter tank, a grease extractor is installed in the feed line between the feed pump and the feedwater heater.

The filtering material most generally used is

  silicates. When sea water is boiled the impurities remain in the boiler.

In the boiler water the salt remains in solution, becoming more concentrated as sea water is continually added, until the concentration reaches the point where foaming will occur.

Foaming is a violent agitation of the surface of the boiler water, causing various sized amounts of water to leap upward into the steam space. The water may travel over with the steam into the machinery, causing damage.

Foaming is immediately noticeable by the water level in the gage glass surging up and down.

The remaining impurities for the most part tend to adhere and bake fast to the hot steel surfaces of the boiler, and in time will build up to such thickness as to insulate and cause overheating of the metal. This build-up is known as scale.

Watertube marine boilers, with which modern

turkish toweling. The grease or oil in the feed-water passing through the toweling clings to it, and if the toweling is renewed before it becomes saturated, oil will have been prevented from entering the boiler. Here again vigilance is required to make sure the filtering material is always renewed in time.

One type of grease extractor uses two sets of toweling, the feedwater passing through one set while the other is being renewed.

Another type has only one set of toweling and it becomes necessary to divert the feedwater through a by-pass line around the extractor when the toweling is to be replaced, leaving a short interval of time when the feedwater does not pass through the grease extractor.

Grease extractors are sometimes provided with pressure gages at the inlet and outlet sides to give a comparison of pressures on each side of the toweling. If the toweling is clean the feedwater will flow through freely and the pressures will be equal. With grease soaked toweling, the pressure on the inlet side will be greater due to the feedwater having difficulty in passing through.

FEEDWATER-SEA WATER IN THE WATER SIDE OF BOILERS

Effect-Sea water contains impurities in solution, in the form of sodium chloride (salt), carbonate of lime (chalk), sulphate of lime (plaster of paris), magnesium chloride (magnesium) and small amounts of other impurities, such as

American ships are equipped, are not able to use sea water as feed for the reasons listed above.

Firetube Scotch marine boilers are able to operate with sea water, although it is not a desirable condition.

The engine department crew is constantly on the alert to prevent leakage of sea water into the boilers.

Entry-The condensers are the most likely place for this leakage to occur, for when in operation a vacuum is maintained in the fresh water side of the condenser. Should a leak develop in one or more of the tubes, the sea water will be sucked through into the fresh water side where it will mix with the condensate, making it more or less salty, according to the size of the leak. If the leak is not promptly detected and repaired, it will cause a concentration of sea water impurities in the boilers with damaging results already mentioned.

A sample of the condensate leaving the condenser and a sample of water from each boiler are usually tested each watch for the presence of sea water. Should any be detected, an immediate search for the leak is started and if the leak is not sufficiently large to permit a serious amount of sea water to enter the boilers before port is reached it may be let go till then, when the leaky condenser tube may be plugged or renewed. A bad leak can sometimes be plugged at sea by pumping sawdust into the cooling water entering the condenser. The vacuum will pull particles of sawdust into the crack, where they will swell up, temporarily sealing the leak.

 

21 

As the fresh water for reserve boiler feed is usually stored in the double-bottom tanks beneath the fire and engine rooms, a leak in the hull will allow sea water to flow in and

  fresh water from the storage tanks is fed into the system. Most ships have a pipe line connection from the storage tanks to the main condenser. When extra feed is needed the

contaminate it. If not detected, this contaminated water would in time be fed to the boilers as make-up feed. It is a good policy to test the water in each storage tank regularly.

FEEDWATER-FRESH WATER IN BOILERS

Most fresh water contains various impurities, depending upon the soil structure of the earth where the water is secured. While fresh water from some ports contains only a slight amount of impurities, making good boiler water, the water in other ports will be very poor for boiler use, as most of the impurities tend to form scale.

With modern boiler water treatment, however, scale formation from most fresh water can be kept to a minimum. When testing boiler water a sample from each boiler is chemically analyzed by the engineers each day to determine the amount of impurities present and the amount of chemicals needed to counteract them. Trisodium phosphate and soda ash are among the chemicals injected into the boilers for this purpose. They act upon the impurities to keep them in solution, preventing their forming scale. A number of so-called boiler compounds are also available for this purpose.

Usually the engineer will blow a small portion of the boiler water overboard each day through the bottom blow-off valve, the purpose being to remove some of the collected impurities before they build up and cause foaming.

Reserve Feed (Extra Feed)-As water is lost from the steam and water cycle through leaks, etc., the water level in the boiler gage glasses will gradually drop. To replace this loss reserve

extra feed valve near the condenser is opened. The vacuum in the condenser causes the extra feed to rush up into the condenser from the storage tanks. The extra feed, of course, travels along with the condensate to the boilers. When the main condenser is not in service the reserve feed is pumped from the storage tanks to the hotwell.

It is much better to take on extra feed slowly over a good part of the watch than to open the extra feed valve wide and bring the boiler water level up quickly. Learn to anticipate the amount of extra feed the boilers will need.

Storage-Fresh water for boiler use is usually stored in the double-bottom tanks beneath the fire and engine rooms, and in the forepeak and afterpeak tanks.

It is important when filling the storage tanks to make certain that nothing but fresh water is admitted, for there have been instances where ships' storage tanks were filled with sea water by mistake. Also ships have left port only to find after a few days out that most of the tanks had not been filled at all. These acts of carelessness are serious and inexcusable.

The fresh water used for drinking and cooking purposes is stored in separate tanks, known as domestic tanks, which are located inside of the ship's Mill.

All fresh water tanks should be sounded daily to determine the amount and a sample of water from each tested.

Fresh water is a precious commodity aboard ship and must be guarded against wastage with unfailing care. Do not let shower baths run unnecessarily. Report fresh water leaks.

 

22 

BOILERS  

SIMPLE BOILER

Principle-A boiler is a closed vessel in which steam is generated from water by the application of heat.

The simple boiler is like a barrel, consisting of a cylindrical steel shell, with the ends closed by flat steel heads. It is partly filled with water and then sealed, after which a fire is started beneath it. The fire and hot gases rise around the lower outside of the shell, the heat being conducted through the steel into the water. This heats the water on the bottom of the boiler first. Hot water being lighter than cold water, it rises, while the colder water in the upper part, being heavier, sinks down to replace it and is in turn heated. These are convection currents, and the process is known as circulation, which goes on continually while a boiler is in service. Circulation is good in some boilers and poor in others, depending upon the design. This is important as will be pointed out later.

The water gradually reaches the temperature where steam is given off, which accumulates in the space above the water known as the steam space. As the steam accumulates, a pressure is built up which would create a very dangerous

SIMPLE BOILER AND SIMPLE FIRETUBE BOILER

condition with the simple boiler. As pressure is exerted in every direction, the flat heads would bulge outward because a flat surface

  boiler due to the small heating area. An improvement is made to allow more surface area of the boiler to come in contact with the hot gases of the fire by making some of the stay-rods hollow and directing the hot gases through them after passing along the bottom of the shell. The water surrounding them is heated.

These hollow stayrods are called tubes and as the fire passes through them they are called firetubes, hence the name, firetube boiler. The tubes are all located below the water level so that they are protected from the heat.

SCOTCH BOILERS UNDER CONSTRUCTION

SCOTCH MARINE BOILER

The only type firetube boiler used aboard ocean-going ships is the Scotch marine. It is a famous boiler, the first one having been installed in a ship in about 1862 and up until around 1900 was practically the only type boiler found aboard merchant or Navy ships. At that time watertube boilers began to come into use but for a number of years the Scotch marine still remained the dominant boiler. With the advent of modern high pressure power plants the watertube boiler became a necessity. However, there are still a considerable number of older American ships

cannot support itself. The boiler would hold very little pressure and would be useless.

The first thing that has to be done with this boiler is brace the flat heads in order to keep them from being pushed out by the pressure. This is accomplished by placing heavy steel rods, called stayrods, from head to head as shown in the next view of the simple boiler, thereby tying the heads together.

The boiler can now safely carry more pressure, but it would still be an unsatisfactory

with Scotch boilers.

Shells and Heads-In the cross-section side view of a Scotch boiler it can be seen that the boiler has a cylindrical steel shell and flat heads the same as the simple firetube boiler. Also the upper portion of the heads are braced with stayrods in the same manner. A further study, however, reveals that something has been added to the simple boiler.

Furnaces-The fuel in the Scotch boiler is burned in a cylindrical steel furnace located

 

23 

SIDE VIEW SCOTCH MARINE BOILER  

inside the water space of the boiler. The furnace is secured by rivets to the front head and is corrugated for strength to resist the crushing effect of the boiler pressure in the water which surrounds it. The number of

  From the rear sheet of the combustion chamber they extend through the water to the rear head of the boiler. In this manner the lower portion of the rear head is also supported against being pushed outward.

furnaces depends on the size of the boiler, there usually being three or four.

Combustion Chamber-The furnace opens into a combustion chamber which is simply a rectangular steel box standing on end and surrounded with water.

In the combustion chamber the unburned gases, given off from the burning fuel in the furnace, mix with air and burn.

The flat sides and top of the combustion chamber must be supported the same as the flat heads of the boiler or they will bulge inward from the surrounding boiler pressure. Small stayrods, called staybolts are used for the rear and side sheets and sometimes for the bottom. They are threaded into the sheets and in some cases have nuts at the outer ends.

From the side sheets the staybolts extend through the water to the shell of the boiler or the side sheet of an adjoining combustion chamber. The bottoms of combustion chambers are usually curved to make them self-supporting in which case staybolts would not be needed as shown. The front or tube sheet is supported by the firetubes which extend through the water space of the boiler to the front head. The top sheet or roof is known as the crown sheet and is supported by crown bars and crown bolts. The crown bar acts as a bridge span from which the crown bolts hold up the crown sheet. The crown sheet is the highest heating surface in this type boiler and the water level must be kept above it at all times or it will become overheated.

 

24 

It is the usual practice to have a separate combustion chamber for each furnace, although Scotch boilers have been built with all the furnaces opening into one large common combustion chamber. There are also double-ended Scotch boilers where separate furnaces from each end of the boiler enter into one combustion chamber.

Tubes-The tubes are made of seamless drawn steel, a popular size being 3 1/4 inch outside diameter which is the way all boiler tubes are measured.

When tubes are installed they are pushed in through the holes in the front head which are slightly larger than the outside of the tubes, and back through the water space and through the corresponding tube holes in the combustion chamber tube sheet. The tubes are made tight in the holes by rolling them around the inside at each end, with a tube expander which works on the principle of a wedge. This squeezes the tube outward tight against the inside of the hole. If properly expanded the joint will not leak unless the

  upward through the smoke box, uptake and stack, from which they are lost overboard.

Circulation-The circulation in a Scotch boiler is poor which necessitates care when starting up cold. The arrows pointing upward in the sketch on page 25, indicate the rise of the water being heated around the furnaces, combustion chamber and tubes. As can be seen, this leaves very little space for the cold water at the top to work its way down. This confliction of currents slows down the circulation.

When firing up a cold Scotch boiler, the water below the furnaces tends to lie there and remain cold. If this is not prevented the water in the upper part of the boiler will be boiling while the bottom will still be cold. This condition places a strain on the boiler, causing leaks at the joints. To prevent this, a small fire is lighted in one furnace. After ten or fifteen minutes it is shut down and a fire lighted in another furnace and so on. This shifting of the fire tends to heat up the entire boiler evenly

tube is overheated, or is disturbed by improper warming up of the boiler or becomes thin with age and wear. After the tubes are expanded, the projecting ends are bent outward and back against the tube sheet. This is called beading and is done to protect the ends from being burned off due to the heat of the fire. The beading also prevents the tubes from pulling out of the holes in the event they should loosen up.

As the number of tubes in a boiler is large, they provide by far the largest amount of heating surface.

Staytubes-A small proportion of the tubes, scattered among the firetubes, are staytubes. They are heavier tubes and are threaded into the tube sheets to give added support to the flat tube sheets and heads.

Operation-The oil burner and air registers are located in the front end of the furnace. The oil is sprayed into the furnace, mixes with the air and burns. In operation some of the heat of the burning fuel passes through the furnace walls into the water. The remainder is carried by the draft into the combustion chamber, where more of it passes through the sides into the surrounding water. The gases, still at a high temperature, next pass into the tubes where the greatest portion of the heat enters the water. The gases still containing some heat flow out the front ends of the tubes and turn

and start the water circulating.

Dangerous Water Level-When the water level drops out of sight in the water gage glass there is no way of knowing where the water level is in the boiler.

Never assume that because the water level was in sight a few seconds before it could not have dropped far enough in the boiler to uncover the crown sheet.

Never try to bring the water level back into sight by opening the feed check valve wide, allowing water to rush into the boiler. If the crown sheet is overheated, the incoming water striking it may cause it to crack or fail, resulting in a disastrous boiler explosion.

Always shut off the oil burners immediately upon discovering a low water condition and notify the engineer.

Advantages-The Scotch boiler has certain advantages over the watertube boiler.

Due to the much larger amount of water contained in the Scotch boiler, there is a much larger amount of heat stored up which makes for steadier steaming pressure and water level.

The Scotch boiler is somewhat cheaper to build and it can use dirtier water, even sea water if necessary.

The Scotch boiler generally requires less repairs than the watertube due to there being no brickwork in the firebox to keep in repair.

Disadvantages-The disadvantages of the Scotch boiler are such as to have caused its replacement with the watertube boiler in new

 

25 

construction of American ships for a number of years.

  BOILER FITTINGS AND ATTACHMENTS

Its large size and weight prevents carrying as much cargo as with watertube boilers.

Due to the large amount of water and poor circulation, steam cannot be raised quickly.

All of the stored-up heat energy being contained in one large shell makes for a greater possibility of boiler explosion.

There being a limit on the thickness of steel plate that can be shaped, Scotch boilers cannot be constructed for working pressures much higher than 250 pounds per square inch which prohibits their use with modern turbine plants.

Generally speaking Scotch boilers are not as efficient to operate as watertube.

All boilers, regardless of their type or design, require a number of fittings and attachments in order to render them safe to operate. The relative position of these fittings and attachments is shown in the front view sketch of a Scotch boiler.

The fittings and attachments and their purposes are:

Water Gage Glass-As it is impossible to see the amount of water inside the boiler, a small glass tube about 12 inches long, known as a gage glass, is installed outside the boiler, in a vertical position.

The top end of the glass is connected to the top of the steam space of the boiler by a pipe

FRONT VIEW OF SCOTCH BOILER WITH FITTINGS ATTACHED  

26

  line while the bottom end of the glass is connected to the water space in the same manner. When the water level rises in the boiler, water will flow in through the bottom connection and rise up in the glass to the same level as the water in the boiler.

The fireman and watertender can determine the water level in the boiler by looking at the gage glass.

The position of the gage glass is such that when the water level is at the lowest visible part of the glass there will still be a few inches of water above the top of the crown sheet or in other types of boilers, the highest heating surface.

The water level should never be allowed to drop out of sight in the gage glass. If this should occur at any time, all fires should be shut down at once, and the engineer immediately notified.

The top of the gage glass is considered the high water level point in a boiler where danger of water carry-over with steam appears.

On most ships the water level should be carried at the center of the glass, however, the correct water level should be determined upon going aboard each ship.

The rolling of a ship has an influence upon the water level to be carried.

Shutoff valves which are operated from the fireroom deck plates by small brass chains are located at the top and bottom of the gage glass. When a glass breaks in service these valves are closed by pulling down on the right-hand chain. This stops the steam and water from blowing out into the fireroom.

A new gage glass can then be installed by backing off the gland nuts, removing the glands and soft rubber packing washers along with any remaining pieces of broken gage

  glass, especially the bottom one, a drain valve is provided from the bottom of the glass. A drain pipe from the valve usually leads to the bilge. At least once each watch the fireman or watertender opens the drain valve for a few seconds, which allows a small stream of steam and water to blow into the bilge where it is easily heard. This is known as blowing down the gage glass, and is a very important duty which must not be neglected if a true water level reading is always to be had. When the drain valve is closed, the water level should immediately return to the glass. A slow return is an indication of at least a partial obstruction in the connections between the boiler and gage glass and should be immediately reported to the engineer.

To make definitely certain that the top and bottom connections are clear, the following procedure is in order. When blowing down the glass, first the top shutoff valve is closed. If the blowing noise is heard from the drain it is evident the bottom connection is clear. The top valve is then opened and the bottom is closed. If the blowing noise is still heard, it is certain that the top connection is also clear. The bottom shutoff valve is then opened and the drain closed.

The plain round gage glass will break upon becoming thinned from the scouring action of the steam from many blowdowns.

The prismatic type gage glass with which most new boilers are equipped is very unlikely to break and is much easier to read, as the water appears black in the glass while the steam is white.

The water gage glass must be looked at regularly every few seconds, as the water level can change quickly, especially in watertube boilers.

At least one gage glass is required on each boiler. If only one is provided, three try cocks will be required; but if two gage glasses are installed, try cocks will not be required,

glass. A new gage glass complete with new washers is installed and the gland nuts carefully tightened. Care must be exercised to make sure the bottom end of the glass does not rest against the bottom fitting, otherwise the glass will crack and break when the steam and water enter the glass.

When the new glass has been installed, the left-hand control chain is pulled down. This opens the top and bottom shutoff valves and the water and steam rush into the glass, again showing the water level.

To remove mud and sediment accumulation which would in time plug the connection to the

although some boilers may have them also.

Try Cocks-Another method of checking the water level in the boiler is by "try cocks" shown in the cross-sectional sketch of a water column.

Try cocks are small valves on the outside of the boiler. The lowest of the three is placed on the boiler at a point two inches above the lowest visible part of the gage glass, the center try cock at the center of the glass, and the top one at a point about level with the top of the

 

27 

gage glass. By opening the try cocks one at a time and noting which ones water or steam squirts out of, the water level is determined.

Water Column-Used when gage glass is not connected directly to the boiler.

Consists of a vertical steel cylinder, the top

  being connected to the steam space and the bottom to the water space.

The gage glass and try cocks connect into the column at the proper level.

Pressure Gage (I)-To show the pressure in the boiler at all times, a pressure gage is installed. This does not have to be mounted on the boiler proper, but should be located at a point in the fireroom that is well illuminated and easily visible to the fireman.

Some pressure gages are equipped with a stationary red hand which points to the desired operating pressure. The pressure hand or pointer should ordinarily not be allowed to go above this, as to do so may cause the safety valves to lift.

The operation of a pressure gage was explained on page 6.

Safety Valves (D)-If the pressure in a boiler were allowed to increase without restriction, it would become so great that with even the strongest boilers, an explosion would occur. To prevent this happening, safety valves set to

GAGE GLASS-WATER COLUMN-TRY COCKS

open at a pressure far below the bursting pressure of a boiler are required.

SIMPLE SAFETY VALVE

The cross-section sketch is of a simple safety valve to show the principle of operation.

The safety valve is attached to the top of the boiler shell (F). The steam under pressure from the boiler pushes upward against the bottom of the valve disc (A). The tension in a coil spring (B) pushes down on the top of the disc holding it on its seat which plugs the opening.

 

28 

When the pressure in the boiler pushing against the bottom of the disc becomes greater than the tension of the spring, the disc lifts, leaving an opening through which the steam escapes to the open air. As long as the pressure in the boiler is kept at this point, the valve will stay open permitting the steam to rush out of the boiler as fast as it is made.

  return. This prevents the possibility of steam entering the boiler through the main steam line from another boiler when it is idle.

It is very important that care be exercised when opening a main stop valve or any other stop valve on a boiler. When opening, the valve wheel should be turned to the left just

This, of course, prevents the pressure from building up any higher.

When the pressure within the boiler drops, the valve spring is then stronger than the boiler pressure and pushes the valve down on its seat, which closes the opening, stopping the flow of steam from the boiler.

The pressure at which the safety valve will open is determined by adjusting the spring tension with the adjusting nut (C). The greater the tension on the spring, the higher will be the boiler pressure before the valve opens and vice versa.

To permit opening of the safety valve by hand at any pressure, a hand-relieving gear is provided. A steel cable leads from the relieving gear on the safety valve to within easy reach of the fireman on the fireroom deck plates so that in an emergency, the safety valves may be opened by simply pulling down these cables by turning the wheel screw (E).

No one should ever tamper with a safety valve. It is set by the boiler inspectors and is the only insurance against excess boiler pressure.

Safety valves have been known to stick in the closed position which in some cases resulted in a boiler explosion. To prevent this, two safety valves are required by law, being commonly built in one valve body and are known as duplex safety valves. One valve opens a few pounds before the other.

The modern safety valve is somewhat more complex than the simple one shown, although its principle of operation remains the same. By adding a pop chamber and blow-down ring the modern safety valve is able to remain open until the pressure in the boiler has dropped a few pounds. This prevents chattering of the valve due to repeated openings and closings.

Main Stop Valve-To control the flow of

enough to raise the disc slightly from its seat. The minute the steam starts to flow through, it can be heard. This is known as cracking a stop. Leave the valve in this position until sufficient steam has passed through to build up a pressure in the cold line. The stop valve may then be opened slowly to full open position.

Carelessness in opening these valves may cause some of the water in the boiler to carry over with the steam into the line, causing water hammer, which is a severe hammering action in the pipe line. If severe enough, it can cause a sudden and disastrous failure of the steam line.

Auxiliary Stop Valve-To control the flow of steam into the auxiliary steam line, the auxiliary stop valve is located on the top of the boiler. It is of the same general design as the main stop valve except that it is smaller.

When opening, the same procedure should be followed.

Dry Pipe-Located inside of the boiler at the very top of the steam space is the dry pipe. A simple type commonly used consists of a steel pipe about six inches in diameter in a horizontal position with each end closed. Many small holes are drilled along the top of the pipe. The main stop valve, auxiliary stop valve and safety valves are connected into the dry pipe. The steam leaving the boiler through any of these valves must first pass through the small holes which tends to remove water which might be traveling with the steam. This makes drier steam, hence the word "dry pipe." They will not remove large amounts of water.

Air Cock--To allow the air to escape when filling the boiler and getting up steam and to let air into the boiler when draining, the air cock is installed on the top of the boiler. It may be either a small valve or a cock.

Feed Lines-Two ways of supplying water to a boiler are required and are known as the main

steam into the main steam line leading to the main engine. It is located on top of the boiler and is usually of the non-return angle globe type shown.

When this type valve is in the open position, steam can flow from the boiler but cannot

and auxiliary feed lines. They are identical, the main feed line being regularly used, with the auxiliary as a stand by ready to go into instant service if trouble should develop with the main feed line.

Usually both lines are equipped with internal  

29 

feed pipes which discharge the water away from the heating surface.

Main Feed Stop and Check Valves-Located in the main feed line with the stop valve next to the boiler. The operation of these valves is explained on page 12. Reach rods are provided on the check valve so that it may be adjusted from the fireroom floor plates.

Auxiliary Feed Stop and Check Valves-Located in auxiliary feed line in same position as in main feed line. Same construction as those in main feed line.

Surface Blowoff Valve-In boiler operation, certain impurities in the boiler water tend to collect and float on the surface of the water. To remove these a surface blowoff valve is installed on the side of the boiler. It is usually an angle type globe valve and is provided with an internal line and scum pan as shown.

When the valve is opened, the pressure in the boiler sweeps the floating scum with the water through the scum pan, internal line, surface blowoff valve, external blowoff line, and overboard through the skin valve.

Bottom Blowoff Valve-To remove the heavier loose impurities which accumulate on the bottom of the boiler, the bottom blowoff valve is installed near the bottom of the boiler. Blow-off valves may be of the angle globe type or of a type especially designed for blowoff service. In the Scotch boiler, it is provided with an internal line as shown.

  for testing boiler water for salt.

Belly Plug-A small metal plug threaded from the outside into a hole in the bottom of the shell of a Scotch marine boiler.

Removed when cleaning boiler, to allow small amount of water lying on bottom of boiler to drain into bilge.

Never attempt to tighten if leakage should occur when in service. The threads may be worn causing the plug to blow out, allowing scalding water to blow out.

Hydrokineter-In some Scotch boilers hydrokineters are installed near the bottom to aid the circulation when starting up a cold boiler. Steam from shore or another boiler is fed to the hydrokineter which consists of a series of nozzles inside the water space. The steam picks up velocity passing through the nozzles into the water. This pushes the water ahead of it from beneath the furnaces as shown. Steam can be raised much quicker on a boiler so equipped.

Fusible Plug-To give warning of low water condition in Scotch boilers fusible plugs are required. They are made of bronze, being round about one inch in diameter and three inches long. A tapered hole in the center extending from end to end is filled with tin which has a melting temperature of about 450° F.

A fusible plug is threaded into a hole in the crown sheet of each combustion chamber

When the valve is opened the pressure in the boiler blows the sediment through the internal line, bottom blowoff valve, external blowoff line, skin valve and overboard.

Skin Valve-Although not attached directly to the boiler, the skin valve must be considered, as it is used in conjunction with the surface and bottom blowoff valves. The blowoff lines from all boilers lead to the skin valve. It is always of the globe type. It is attached directly to the inside of the ship's hull, hence the name skin valve.

When blowing down a boiler, the skin valve is opened first and closed last. Its purpose is to prevent flooding of the ship in the event the external blowoff piping between the boilers and the ship's hull should break.

Salinometer Cock-Located on the boiler below the water level for removing small amounts of boiler water for testing purposes. Derived its name from the Salinometer, a crude device for determining the amount of salt in water, which at one time was the most widely used method

from the fire side. Should the boiler water level drop below the crown sheet, the fusible plug will be unprotected by water and the banca tin will melt, leaving a hole through which steam will blow into the combustion chamber and furnace, giving warning to the fireman.

Should a fusible plug melt on you, shut the

fires off immediately and notify the engineer. Fusible plugs are ordinarily renewed once each year.

WATERTUBE TYPE BOILERS

Due to the many disadvantages of the -Scotch boiler, marine engineers began to develop the watertube boiler for marine use, starting around the year 1900. As watertube boilers re quire much purer feedwater than Scotch boilers, their general acceptance was slow for a time due to lack of water-treating knowledge in those days. Many watertube boilers were installed in American ships during the large ship construction program of the first World War and since

 

30 

B & W (BABCOCK AND WILCOX) STRAIGHT TUBE, CROSS DRUM WATERTUBE BOILER

  that time the majority of boilers installed in American ships have been watertube.

The principle of operation of a watertube boiler is the opposite of a firetube in that the water and steam are inside the tubes while the fire flows around the outside.

There are several different types of marine watertube boilers depending upon the pressure desired, amount of steam needed and the type of ship. A type that is very popular, having been installed in most of the older ships having watertube boilers, and in practically all of the new Liberty Ships and many others, is the B & W "straight tube, cross drum." The cross

  sectional sketches are of this type. The steam and water drum consists of a cylindrical steel shell about 42 inches in diameter and several feet long, the ends being closed with dished steel heads. Downtake nipples (short tubes)-lead from the bottom of the drum into the top of the front headers. Hundreds of tubes in an inclined position lead from the after side of the front headers to the forward side of the rear headers. The top of the rear headers is connected to the after side of the steam and water drum by the return tubes. Below the tubes is located the firebox which consists of four brick walls and a brick floor.

 

31 

 

32

 

VICTORY SHIP BOILER  

This type of boiler is used in all Victory ships.

Two such units are used in each installation. The boiler is of the sinuous header type and is equipped with an interdeck superheater. Other apparatus includes a stud tube economizer, a desuperheater to supply low temperature steam for auxiliaries; and water cooled walls.

This type of boiler operates at a pressure of about 450 lbs. per square inch and at 750° F. steam temperature.

 

33

 

STEAM AND WATER DRUM  

The oil burners are located in the front wall of the firebox.

The boiler is filled through the steam and water drum. As the water enters, it flows downward through the downtake nipples, gradually filling up the headers and tubes. Water is allowed to enter until the drum is half filled.

When the oil burner is placed in operation, the fire and hot gases produced in the firebox pass upward around the rear portion of the tubes as shown by the arrows, being directed in their travel by the baffles which are nothing more than partitions between the tubes. The hot gases pass to the top, around the superheater tubes and then turn down passing around the center portion of the tubes. The gases upon striking the top of the horizontal baffle resting on the top of the bottom row of tubes, turn under the bottom of the second vertical baffle and then flow upward around the front portion of the tubes, from there passing into the uptake and smokestack.

This is known as a three-pass boiler, as the hot gases pass in three different directions

  outside of the tubes much of their heat is conducted through the walls of the tubes into the water inside.

As the water in the inclined tubes is heated it becomes lighter and rises, flowing into the rear headers where it rises to the top and flows to the steam and water drum through the return tubes.

In the meantime the cold water in the drum being heavier sinks down the downtake nipples into the front headers from where it flows into the tubes replacing the water heated. This cold water is in turn heated and rises. This circulation goes on continually while the boiler is in service. As the water is all flowing in one direction the circulation in a watertube boiler is good.

Tubes-The tubes are known as generating or evaporating tubes and are made of seamless drawn steel. Although their size varies in different boilers, the majority are 4-inch diameter in the bottom row and 2-inch for all others. Some of the newest of this type boiler, however, have very small tubes, 1-inch or 1 1/4-inch diameter, being installed very close together, which slows down the speed of the

over the tubes causing the gases to slow down, giving the water in the tubes more time to extract their heat.

As the fire and hot gases pass around the

rising gases, making it possible to operate efficiently without baffles. The tubes are expanded for tightness in the tube holes of the headers in the same

 

34 

manner as the firetube boiler. The projecting ends, however, are flared or belled outward instead of beaded as the ends are in water and not exposed to fire. The flaring prevents the tubes from pulling out of the headers in event of loosening up.

Headers-The headers are of the sectional type, being sinuous from top to bottom. This permits staggering the position of the tubes vertically which aids in slowing down the flow of fire and gases. The headers are made of forged steel, their cross section being square. Opposite the tube ends are handholes to permit tube cleaning and repairs.

Muddrum-Attached to the bottom of the front headers by short nipples is the muddrum which is a small square box of forged steel extending entirely across the boiler beneath the headers. This being the lowest point in the boiler circulation, the mud and sediment settle into the muddrum and to protect the box from over-heating, brickwork is installed between it and the firebox. Attached to the bottom of the muddrum at one end is the bottom blowoff valve and to the top the salinometer cock.

Steam and Water Drum-On page 33 a cross-sectional view of the steam and water drum shows the various valves and fittings. The dished heads at each end are secured to the ends of the shell plate by fusion welding in all modern boilers. In the center of each head is an elliptical shaped manhole opening, about 11 inches by 16 inches in size, which is sufficiently large for the average sized man to enter the drum for cleaning and repair work. The left-hand head has the manhole plate in

  stop valves and safety valve connecting into it. A few of the small holes through which the steam enters along the top can be seen.

The small perforated pipe line running along the center of the drum is the surface blowoff scum pipe which takes the place of the scum pan. The surface blowoff valve shown attached in the center of the pipe is actually on the outside of the drum.

The main feed check valve and stop valve are on the outside of the drum near the left end. The check valve is provided with a reach rod to permit its adjustment from the floor plates by the fireman. The feedwater passes into the perforated internal feed line which extends the length of the drum to permit the feedwater to be discharged downward into all the downtake nipples. The auxiliary feed check and stop valves not shown, connect onto the right-hand end of the same internal feed line.

One of the water gage glasses complete with its top and bottom connection shutoff valves, is shown near the right-hand end of the drum. In most of the boilers the water level should be carried midway of the glass.

The downtake nipples lead out of the bottom entirely across the drum, each nipple discharging into the top of a separate front header. Only three of these are shown.

Superheater-The convection type superheater shown at the top rear of the boiler consists of a number of 2-inch tubes bent in the shape of the letter U, which allows the tubes to expand and contract at will. The saturated steam from the steam and water drum passes through the

place with a gasket between it and the head for tightness. The gaskets are the ring type generally of woven asbestos. When installing they should be well coated with a mixture of flake graphite and steam engine cylinder oil, to prevent the gasket from burning fast to the plate and head. Never enter an empty boiler until positive that all valves are closed, sign on front of boiler stating that there is a man inside, and the engineer knows you are entering. Men have been scalded to death from steam or boiling water entering through an open valve from another live boiler.

Attached to the top of the drum are the pipe line to the pressure gage, the main stop valve, auxiliary stop valve, duplex safety valves and air cock.

Inside of the drum the dry pipe may be seen running along the top with the main and auxiliary

steam line into the superheater inlet header, then through the U tubes into the outlet header from which it passes into the main steam line. The steam passing through the U tubes picks up considerable heat from the hot gases flowing around the outside of the tubes. This added heat gives the steam more energy without increasing its pressure. At the superheater outlet a main and auxiliary steam stop valve and a thermometer and pressure gage connection are provided. (See page 31.)

Other type superheaters are interdeck, installed about midway between the banks of boiler generating tubes; and radiant located near the radiant heat of the firebox. The nearer to the fire the superheater is installed, the hotter will be the superheated steam.

When firing up a cold watertube boiler care must be exercised not to put too large a fire in the firebox, otherwise the superheater tubes will

 

35 

be damaged from overheating due to the fact that there is no steam to flow through the tubes to protect them until steam is formed in the boiler.

Firebox-The firebox walls are of high temperature firebrick to resist and hold inside the 2000° F. or more temperature of the burning fuel. The front wall around the oil burners is formed with special cone-shaped high temperature refractory material. Unless the brickwork is treated properly it will soon crack, crumble and begin to tumble down. This means repair work for the crew in port. Even slight flare-backs (combustion explosions) from careless handling of the oil burners can cause damage to the brickwork. Allowing cold air to blow in on the hot brickwork when shutting down a boiler will also cause damage.

When this type boiler is built to operate at

  long pipe extending through one side wall of the boiler, between two rows of tubes nearly to the opposite side wall. Holes are located all along one side of the pipe. Dry steam is admitted from the boiler through the sootblower control valve on the end of the pipe outside the boiler side wall. As the pipe is slowly turned from the outside, the steam escapes through the holes, blowing the soot from the outside of the tubes. An excessive amount of forced draft is used during this operation to carry the loosened soot through the passes and up the stack overboard.

When operating it must be made certain that dry steam is used, as wet steam will mix with the soot, setting up a condition that will cause rapid corrosion of the tubes.

Sootblowers must be kept in adjustment, otherwise the escaping steam may rapidly cut

high pressures it is necessary to protect the firebox brickwork from the increased firebox temperatures. This is accomplished by installing waterwall tubes. These tubes are of the same general type as the generating tubes but are located either in an inclined or vertical position in front of or within the firebox brick walls. The tubes are connected into the circulation of the boiler and installed very close together. In this manner practically the entire brickwork is protected from the heat by a wall of water. The heated water in the tubes rises to the steam and water drum and returns to the tubes from the drum by an outside pipe connection. Besides protecting the brickwork, the waterwall tubes provide additional heating surface, making it possible for the boiler to produce more steam.

Baffles-Act as partitions between the tubes to slow down the hot gases and direct them over all of the tube heating surface. Those near the firebox are made of high temperature refractory material to withstand the heat while those between the tubes may be of cast iron.

Baffles can also be damaged by slight flare-backs.

Sootblowers-With the best combustion, burning fuel oil produces some soot, which travels with the hot gases and lodges on the outside of the tubes. Ordinarily this should be removed each day, otherwise the heat has difficulty getting to the tubes, resulting in fuel wastage. Today practically all oil burning boilers are equipped with sootblowers which make an easy job of removing the soot. Four sootblower elements are usually installed in the straight tube cross drum type watertube boiler shown in the two views. A sootblower element consists of a

holes in the tubes.

During wartime sootblowers must only be used when authorized, due to the danger of smoke being seen by the enemy.

Scale and Oil-One of the most important things in successful, trouble-free, watertube boiler operation is to keep the water side of the boiler clean. Any appreciable formation of scale or mud in a tube directly over the fire is almost certain to cause overheating with resultant tube failure. Modern methods of treating the water in the boiler practically eliminate this possibility if the treatment is properly kept up.

Oil and grease are almost certain to cause tube failure, especially if the boiler is being forced.

Dangerous Water Level-As in all boilers, the water level in a watertube boiler must not be allowed to drop below the bottom of the gage glass. To do so may leave some of the boiler tubes dry, resulting in their overheating. Although the danger of disastrous explosion may not be as great as in a Scotch boiler, terrific damage has been done to both men and property by a bursting boiler tube. The most important job of a fireman and watertender is to keep the water level in sight and at its proper steaming level.

Advantages-Due to the diameter of the drums being relatively small, watertube boilers may be constructed for very high pressures, at least one boiler having been built for 2,000 pounds per square inch. Since they are smaller and lighter than the Scotch boiler, it is possible for the ships to carry more cargo.

Steam may be raised quickly on a cold boiler. If necessary it may be safely done in an hour with most boilers.

 

36 

C-E MARINE TWO-DRUM WATERTUBE BOILER  

This modern type, high pressure, bent tube boiler, is also known as "D" type. It is installed on some of the high speed tankers and cargo vessels.

Its construction is compact, fitting nicely into the ship's hull.

The oil burners are located in the front of the firebox at the left side. The firebox walls are lined with waterwall tubes, the top ends of which enter the steam and water drum. The bottom ends are expanded info a header, which is connected to the muddrum by floor tubes.

The superheater tubes are of the radiant type, located near the firebox, between the vertical generating tubes.

The economizer tubes are at the lower right-hand corner and above them the air preheater tubes.

In operation the fire and hot gases pass upward around the waterwall tubes and generating

tubes nearest the firebox. A vertical baffle directs the hot gases downward around the right-hand section of generating tubes. From here they turn upward passing around the economizer and air preheater tubes to the uptake and stack.

The hottest gases are in the firebox, causing the water in the tubes surrounding it to rise upward from the muddrum to the steam drum. From there it settles down the cooler generating tubes at the right side.

 

37 

Watertube boilers may be forced without harming them.

The water and steam being separated into relatively small sections reduces the possibility of a disastrous explosion.

Watertube boilers may be assembled in the ship, making for easier installation in many cases.

Disadvantages-Due to the small amount of water contained and steam stored it is more difficult to maintain a steady steam pressure and water level, especially when the main engine is being maneuvered. The fireman must act quickly at this time, when lighting off and shutting down burners and adjusting feed check valves.

Watertube boilers must have better water than the Scotch marine.

Watertube boilers cost more to build.

Due to the firebox being constructed of brickwork there is apt to be more repair work.

AUTOMATIC BOILER FEEDWATER REGULATORS

Most modern marine boilers operating from pressure of 400 lbs. upward are equipped with automatic feedwater regulators which maintain a proper water level without the necessity of manual regulation of the feed check valves. Each boiler has its own

  by a larger metal tube. The upper end of the inner tube is connected to the steam space of the boiler. The lower end of the inner metal tube is connected to the water space of the boiler. The outer is connected by copper tube to a metal bellows in the feedwater regulator valve. The space between the inner and outer tubes is filled with water. The steam in the inner tube causes the water surrounding it

BAILEY AUTOMATIC FEEDWATER REGULATOR

to flash into steam, building up a pressure which forces the water down the copper tube into the bellows. This pressure causes the

regulator located in the main feedline just before the feed check and stop valves. Although most regulators satisfactorily maintain the proper water level always remember that, as a mechanical device, it should not be trusted. The water gage glass should be watched as closely as though the feedwater was being regulated by hand.

One type of automatic regulator works on the principle of a float on the surface of the water in the steam and water drum. As the float rises and falls it operates, through a lever arrangement, a regulator valve in the feedline. When the float drops, the regulator valve opens, allowing feedwater to enter the boiler. As the water level rises so does the float which, by closing the regulator valve, decreases the amount of water entering the boiler.

Shown in the cross-sectional sketch is another type of feedwater regulator, known as the Bailey Thermo-Hydraulic Feedwater Regulator, which operates on the thermo-hydraulic principle. This consists essentially of a pressure generator and a feedwater regulator valve. The generator is a metal tube which is surrounded

metal bellows to expand, forcing the feedwater regulator valve open against the tension of the coil spring. When the water level rises in the boiler it also rises in the inner tube taking the place of the steam. As this water is relatively cool from having been trapped in the U-leg, it lowers the temperature of the water between the inner and outer tubes. Contraction of the water in the bellows permits the coil spring to close the regulator valve.

To remove any accumulation of sediment in the water leg, the blowdown valve should be opened once each twenty-four hours.

 

38 

DRAFT  

To make steam, fuel must be burned, but before fuel can burn oxygen must be supplied to it as it is the oxygen combining with the carbon in the fuel that results in combustion. Air contains oxygen, so air must be supplied to the furnace or firebox of a boiler and the method of doing this is called draft.

NATURAL DRAFT

The only type of draft known for many years was natural draft. When a fire burns in the open, such as a bonfire, natural draft occurs. What happens is that the hot gases given off

  the entire fireroom, including the fireman, under pressure. The furnace fronts around the oil burners are left open, allowing the air to rush into the furnaces. When entering or leaving a fireroom of this type it is necessary to pass through an air lock, otherwise the air pressure would rush out when the door is opened.

Induced Draft-Still another type is induced draft. With this the blower is located in the uptake leading from the boiler to the stack. The blower creates a small vacuum in the furnace, causing the fresh air in the fireroom

by the burning fuel are lighter than the surrounding air and rise upward. The colder surrounding air being heavier sinks down and flows into the fire.

In a boiler the hot gases rise up the stack and the relatively cold air in the fireroom sinks down and flows into the front of the furnace. The hotter the gases in the stack and the colder the air outside, the better will be the draft. The direction and strength of the wind and the ship's course and speed also have an influence on natural draft. It is evident then that the amount of natural draft is for the most part dependent upon several uncontrollable factors, which limit the amount of fuel that may be burned in a boiler. This in turn limits the amount of steam that can be produced. When a greater quantity of steam is necessary some other means of supplying air must be provided. This is known as forced draft.

FORCED DRAFT

Forced draft is used entirely with oil-burning marine boilers and to a considerable extent with coal. There are several types of forced draft, the most popular type being where a large steel-bladed fan known as a blower is used. The fan takes air from the fireroom or engine room and blows it through a sheet metal duct (trunk) to the furnace front which is sealed from the fire-room to prevent natural draft from entering. By controlling the speed of the fan the exact amount of air needed for proper burning of the fuel can be supplied at all times. The blower is driven by a steam engine or an electric motor.

Closed Fireroom-In a few large passenger ships a type of forced draft known as closed fireroom is used. With this type the fireroom is sealed and the blower, which is located above it, forces the air directly into the fireroom, placing

to rush in through the open furnace fronts. Another method of producing induced draft, no longer used, is a steam jet pointing upward in the stack. The velocity of the escaping steam leaving the nozzle creates a vacuum which causes the air to rush into the furnace. The large waste of heat and water prohibits its use.

MANOMETER (DRAFT GAGE)

DRAFT GAGE

Draft pressure is so slight that it cannot be measured with an ordinary pressure gage so a glass U tube known as a manometer is used. One end of the tube is connected by a small pipe line to the duct through which the air is being blown to the furnace or to another part of the

 

39

  boiler or uptake. Between the legs of the tube is a scale graduated in inches. The U tube is half filled with colored water. When the blower is started up, the air pressure in the duct becomes greater than the atmosphere and travels down the pipe pushing the water down somewhat in that leg of the U tube. This causes the water to rise up a corresponding amount on the open leg. The distance in inches between the water levels in the two legs is the pressure of draft. When the blower is speeded up the number of inches between the water levels becomes greater. When slowed down they become less. Draft then is measured in inches of water, one inch being equal to about .036 of a pound pressure.

CROSS SECTION HAYS GAGE

Modern marine power plants quite often use the Hays leather diaphragm type gage, which operates on an entirely different principle. In this gage the air pressure enters through a connection from the duct or furnace and pushes

  against the side of a slack leather diaphragm. This pushes the diaphragm in and through a series of connected levers, links and springs the pointer is moved over a graduated scale marked in inches. To determine the amount of draft the fireman merely has to note the particular number of inches in front of the pointer.

Draft gages are usually located in the fire-room at a point easily visible to the fireman.

Draft pressure drops rapidly as it flows along a duct or passes through the boiler. In modern boilers draft gages are connected to several points in the boiler and uptakes so that the draft pressure all through the boiler may be known at all times.

HAYS DRAFT GAGE

In wartime it is especially important that the proper amount of draft be carried at all times to prevent a smoking stack. In the daytime a little too much draft is better than too little. At night excess draft may cause sparks to fly from the stack.

 

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FUELS  

Anything that will burn may be called a fuel. The only kinds used in marine boilers are coal and fuel oil.

COAL

Up until the first world war, bituminous (soft) coal was about the only fuel used in marine boilers, but at that time fuel oil began replacing coal in American ships until today nearly all burn oil. There are, however, a few coal burners left which necessitates a brief discussion of coal and its burning.

Bituminous coal contains on the average about 14,500 B.T.U.'s per pound, and upon analyzing the coal we find that it contains more than half carbon, about a third volatile matter and a small ash and sulphur content. It is the carbon in the coal uniting -with the oxygen in the air that produces the fire.

Handling and Firing Coal-All coal burning marine boilers are hand fired, which means that more firemen are required than when oil fuel is used, and in addition, several coal passers.

Greater time and expense are required to load coal and more space is required for its storage, resulting in less cargo space than with oil fuel. The coal is stored in bunkers (compartments) adjacent to the fireroom, from whence it is removed in buckets or wheelbarrows by the coal passers who pile it on the fireroom deck plates as needed. The firemen, using scoops, shovel it into the furnaces.

The best firing results, with least smoke, are usually obtained by carrying a thin fire. This requires that the fireman shovel in coal in small amounts and often, rather than large amounts less often. This procedure will depend somewhat upon the quality of the

  also breaks up the fuel bed sufficiently to permit air to pass through.

The presence of dark spots in the ash pit indicates that clinkers have formed in the fuel bed. These must be removed, as they reduce the heat of the fire. To do this requires that the fire be cleaned frequently.

To clean a fire, one side of the fire is allowed to burn down until only the clinkers and ashes are left. These are pulled out the furnace front onto the deck plates by the fireman, using a long-handled hoe. The heat of the clinkers falling on the deck plates is quenched by sea water from a hose in the hands of the coal passer. The clinkers and ashes are placed in steel buckets, hauled topside and dumped overboard, unless an automatic ash ejector is provided.

When the one side of the fire has been cleaned, the best part of the uncleaned side is thrown over on the clean grates with a slice bar, and a little green coal is then spread lightly over this new fire. The clinkers and ashes are then hoed out of the unclean side. By the time this is completed, the first side cleaned is burning up brightly and may be spread evenly over the entire grate surface. It is sometimes necessary to take a scoopful or two of burning coal from another furnace. A fire must be cleaned very quickly, as cold air is rushing into the furnace while the door is open, chilling the boiler.

Removable ash pit doors are used to cut down the natural draft, should it become too strong. Also to control the draft, adjustable dampers are installed in the uptakes.

Only through experience is a good coal burning fireman made. No amount of theory can teach him the proper handling of the scoop, hoe and slice bar, upon which depends

coal; however, it is generally found to be the best firing method.

In most cases it is best to spread the coal evenly over one-half of the fire at a time rather than to cover the entire fire with green coal. This alternate firing makes for steadier steaming and less smoke.

As the coal burns, ash and clinkers form within the fuel bed next to the grate bars and must be removed. To remove the ashes, the slice bar is pushed inward beneath the fire on the top of the grate bars. This causes the ash to drop through the grates into the ash pit. This

entirely the efficient burning of the fuel and steady steam pressure.

FUEL OIL

Fuel oil has a number of advantages over coal as a fuel for marine use. Being in liquid form, it is brought aboard through a hose, eliminating much hand labor. It is stored in spaces of the ship not possible with coal, such as the double-bottoms, which means more space available for cargo. Less firemen are required in the handling and burning of coal. The problem of ash

 

41 

disposal is eliminated. The engine compartment and the ship in general can be kept much cleaner. The steam pressure can be kept steadier than with coal. When burning oil it is not necessary to continually open and close the furnace doors, doing away with large amounts of cold air rushing into the furnace and chilling the boiler which often results in leaky tubes.

Although the price of oil is usually higher than coal its many advantages make it more economical to burn in the long run.

Fuel oil is a heavy-bodied oil that is the residue left from crude oil after the various grades of gasoline, kerosene and lubricating oils have been removed at the refinery.

It consists of about 85% carbon and the remaining 15% consists of hydrogen, oxygen, nitrogen, sulphur, sand and water.

The principal measures of the properties of fuel oil are:

Flash Point-The temperature at which the oil gives off vapors that will ignite but will not burn steadily. The oil becomes dangerous at

  point at which the oil gives off vapors that burn continuously.

The flash point and fire point may be determined by heating oil in an open dish in which is placed a thermometer. An open flame is held above the oil. When spurts of flame occur the temperature of the oil is noted. This is the flash point. When the vapors given off burn steadily the temperature is again noted. This is the fire point.

The temperature of the fuel oil at the burners must be sufficient to permit the oil to atomize thoroughly.

Viscosity-is a measure of the oil's body, which means its rate of flow. A heavy-bodied oil flows more slowly than a light-bodied one.

Temperature affects the viscosity. When an oil is cold the viscosity increases, when hot it decreases.

The viscosity of an oil is determined by passing a sample of the oil to be tested through a viscosimeter. Briefly, a viscosimeter consists of an open dish in which 60 c.c. of the oil to be tested is poured. It is

this point, as explosions can occur. When handling and storing, fuel oil must be kept below this temperature for safety's sake. Rules and regulations require that marine fuel oil shall not have a flash point below 150° F. This is to prevent inflammable vapors from forming in the storage tanks under ordinary atmospheric conditions. The flash points of fuel oils vary according to the body of the oil. It can only be determined by test.

Fire Point-is a temperature above the flash

heated to a standard temperature of 70° F. When 70° F. has been reached the oil is allowed to run out the bottom of the dish through a standard-sized opening. The number of seconds it takes for the oil to run through is the Saybolt second viscosity of the oil. The heavier the oil the longer it will take for it to run through and the higher will be its viscosity. The lighter the oil the quicker it will run through and the lower will be its Saybolt second viscosity.

 

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OIL BURNING INSTALLATION  

The simple principle of burning fuel oil is to reduce the viscosity to the proper point and place it under pressure so that the oil burner can break it up into many small particles like a mist, in which form it sprays into the firebox or furnace. This permits the thorough mixing of air with the oil, necessary for good combustion, and is known as atomization.

Several pieces of equipment, which are known as the Oil Burning Installation are required for the storing, handling and heating of the oil. The sketch shows the relative location of the various pieces of equipment in a typical mechanical pressure type oil burning system.

STORAGE TANKS

Storage tanks are located in the ship's double-bottoms beneath the cargo holds and wing tanks on the ship's side. Several pieces of equipment are required to be fitted to the tanks.

For filling the tanks a filling line which branches off to each tank is installed from

  go above this may cause inflammable vapors to be given off.

Entering the top of each tank is a fire smothering pipe line equipped with control valve. CO2 (carbon dioxide) is the most popular agent used on modern ships for fighting fire. Previously live steam was used. In the event of fire in the tank the smothering valve is opened allowing the CO2 to flow into the storage tank and extinguish the fire.

A manhole is provided in the top of each tank to permit entrance for cleaning and repairs. A fuel oil tank should never be entered until it has been gas freed and tested for sufficient oxygen. Never enter without a safety line attached and someone tending it on the outside. Men have lost their lives by being careless in this respect. The breathing of oil vapors or the lack of sufficient oxygen will cause a man to be overcome very quickly.

Fuel oil is sold by volume, making it necessary to consider the temperature when purchasing.

topside. The branch lines are equipped with shutoff valves to control the flow of oil to each tank. The filling line enters the top of the tanks and must extend downward to discharge within 6 inches of the bottom of the tank or be equipped with a gooseneck to discharge the oil upward. When taking fuel aboard constant vigilance must be maintained to prevent one or more of the tanks from being overflowed. Besides wasting the fuel, it is difficult to clean up. If fuel oil should spill into the harbor the ship may be heavily fined by the port authorities.

A vent pipe leading from the top of the tank is required to permit air and any inflammable vapors to escape to a safe point above the ship. The discharge end of the vent pipe is provided with a gooseneck and must be covered with a flame screen. The flame screen is made of wire gauze and its purpose is to prevent flame from burning vapors on the outside traveling down the vent into the tank. The screen must be kept in good condition, never painted and always in place.

Steam heating coils are necessary along the bottom of the tank so that the heavy oil may be heated to lower its viscosity so that it may be pumped. This is especially necessary when the ship is in cold water. The fuel in the tanks should never be heated higher than 150° F. To

Storage tanks are not filled more than 90% full, allowing room for expansion in the event the oil should become warmer after being stored.

TRANSFER PUMP

Transfer pump removes the oil from the storage tanks through the suction valve and line, and discharges it through the discharge line into the settling tanks.

SETTLING TANKS

Settling tanks are located in the fireroom, usually one on each side. Here any water that may have come aboard in the oil is allowed to settle to the bottom. Also there is always the possibility of sea water entering the storage tanks through leaks in the ship's hull.

If water reaches the burners in any quantity the fires will go out. A slight amount will cause the fires to sputter.

The water that accumulates on the bottom of the settling tanks is pumped out through the low suction valve and discharged either overboard or into a disposal tank while the oil for the fires is usually removed through the high suction.

It will, be noted that internal gate type shutoff valves with extension control rods to

 

43 

Oil Burning Installation  

44 

topside are provided at the high and low suctions. This is required by Rules and Regulations, to prevent flooding of the fireroom with fuel oil in the event of an emergency, such as a fire in the fireroom.

Settling tanks are provided with internal filling line, heating coils, vent pipe, and a smothering system the same as the storage tanks. After the oil passes through the external high or low suction shutoff valves it passes through the duplex suction strainers.

  AIR CHAMBER

An air chamber is located in the system on the discharge side of the service pumps, acting as a cushion to reduce pressure fluctuation caused by the operation of the pump.

OIL HEATERS

In the oil heaters, the oil is heated to the proper temperature to reduce its viscosity to the point where it will atomize best. This

DUPLEX SUCTION STRAINERS

Duplex suction strainers are a basket type strainer of coarse mesh to prevent stones or other good-sized foreign matter in the oil from entering and damaging the fuel oil service pumps. Only one strainer is used at a time, the other being cleaned and kept as a standby. The strainers must be changed and cleaned each watch, otherwise they may become clogged with dirt preventing the flow of oil to the pumps.

FUEL OIL SERVICE PUMPS

Fuel oil service pumps take the oil from the settling tanks and discharge it under pressure to the fuel oil heaters and burners.

At least two pumps are required, one being a spare ready for instant service in the event of trouble with the other.

Regulation of the speed of the pump varies the pressure of the oil and controls the amount of oil being burned. The desired oil pressure for best atomization in most modern burner systems is from 100 to 250 pounds per square inch.

The steam line supplying steam to operate the pumps is provided with a shutoff valve having an extension rod leading to the topside, preferably the boat deck. This makes possible the stopping of the pump from outside the fire-room in an emergency.

METER

The oil leaving the pump under the desired pressure passes through a meter which registers the amount of oil flowing to the burners in gallons. The meter is read at the beginning and end of each watch by the engineer or fireman to determine the amount of fuel burned during the watch. Readings are entered in the engine room logbook. The meter is equipped with a by-pass line in the event of trouble.

temperature will depend upon the grade of oil being used, and is usually posted in the fireroom.

All fuel oil heaters use steam as the heating agent.

One type heater is a closed steel vessel through which a number of steel coils pass vertically from head to head. As the fuel oil flows upward through the coils, which are surrounded by live steam piped from the boilers, the heat in the steam is conducted through the walls of the coils into the fuel. Since the temperature is regulated by the amount of steam allowed to enter the heater, to increase the temperature open the steam valve wider which allows more steam to flow in around the coils. To reduce the temperature, close in on the steam valve and reduce the amount of steam entering. Remember that when the amount of oil flowing through the heater changes, the amount of steam for heating must be changed.

Generally temperature is regulated by the fireman but some heaters are equipped with automatic temperature regulators which admit just the right amount of steam at all times to maintain the proper temperature.

Another type heater uses just the opposite type principle, in which steam passes through the coils while the oil surrounds them. The temperature is controlled in the same manner.

If the oil temperature is allowed to become excessively high in the heaters the fuel will carbonize in the coils and its heating ability will be reduced. This will also make it necessary to clean the coils.

Excessive temperature also causes the oil to vaporize resulting in the fires pulsating.

At least two heaters are required, one being a stand-by while the other is in service. In most systems both heaters may be used

simultaneously if necessary.

The steam line leading to the heaters also has a shutoff valve with control rod reaching to topside for emergency shutoff outside the fireroom.  

45 

THERMOMETER

Thermometer is installed in the oil line on the discharge side of the heater so that the temperature of the oil is visible at all times to the fireman on watch.

DUPLEX DISCHARGE STRAINERS

Duplex discharge strainers, through which the oil next flows are of the same general construction as the suction strainers except that they are smaller in size.

As the hot oil is thin (low viscosity) it is possible for it to pass through fine mesh strainers which remove fine particles of foreign matter such as sand, which would interfere with the atomization of the oil in the burners. It is important that strainers be changed over each watch and the dirty one cleaned and left ready for the next change.

  MASTER VALVE

Located in the branch oil line to each boiler is a master shutoff valve. By closing them the flow of oil to all burners is stopped. Used in an emergency or when a boiler is out of service.

BURNER VALVES

Two shutoff valves are installed in the branch line to each burner providing double insurance against leakage of oil into the firebox when the burner is shut off.

RECIRCULATING VALVE

When starting up a cold oil burning system the recirculating valve at the end of the oil line is opened permitting the cold oil to return through the recirculating line back to the suction side of the service pump. When hot oil reaches the burners this valve is closed and the burners lighted.

 

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BURNING FUEL OIL  

To burn well, fuel oil must be sprayed into the firebox in the form of a mist. This is known as atomization and is accomplished by the oil burner, a cross section of which is shown. The oil enters through the atomizer

  enters the firebox around the atomizer through the air register openings (B). The air scoops (C) direct the air into the firebox in the proper direction to mix thoroughly with the atomized oil.

(A) which is the heart of the burner. The air In the enlarged cross-sectional view of the atomizer the fuel oil enters the atomizer from the fuel oil line after passing through the two

LIBERTY SHIP FIREROOM

This view of the Liberty Ship fireroom shows the front of the number 2 (starboard) boiler. The fuel oil line (1) is across the front of the boiler with two shutoff valves in the branch line to each burner. Directly below (3) is the fuel oil thermometer and master valve. One of the fuel oil service pumps is on the forward bulkhead at (4) while a feed check valve adjustment wheel is overhead at (5).

 

47 

 

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FIREROOM WORKBENCH AND GAGE BOARD

This is a view of the fireroom burner bench and gage board of a Liberty Ship, showing the fireman on the left cleaning oil burner atomizers while the engineer on the right reads the various gages. A complete atomizer lies in the center of the bench with the atomizing end toward the fireman. Spare, clean atomizers with the connection ends up are in the rack at the left end of the bench. The non-adjustable vise for holding the atomizer when taking apart for cleaning is located at the right front corner of the bench.

On the gage board the pressure in the port and starboard boilers is read on the large gages at the bottom of the board. The pointers are on 220 lbs. per sq. inch. The two smaller gages above these indicate the pressure of the feedwater in the main feed line. The two black faced gages at the top corners are temperature gages which show the temperature of the superheated steam from each boiler. The pointers indicate about 440°. The HAYS gages in the top center are draft gages which at that particular moment read slightly less than I inch. The stack temperature of each boiler can be determined by turning the switch pointer at bottom center to the position on the dial for the desired stack and then reading the gage directly above it.   burner shutoff valves, and the burner connection made tight by the quickly removable yoke. Traveling down the inside of the atomizer extension piece the oil comes to the nozzle body through which four drilled holes lead the oil to the outer ends of the tangential slots in the sprayer plate. The oil

  into the conical center chamber, in such a manner as to give the oil a whirling motion with which it passes through the orifice in the sprayer plate to the firebox in the form of a hollow cone of mist. The sprayer plate is held in place by a tip nut which is threaded to the nozzle body.

rushes down these slots  

49 

The successful operation of the atomizer depends upon the oil being at the proper viscosity (controlled by the oil temperature) and the oil being under pressure (controlled by pressure regulator on the fuel oil service pumps). Also the sprayer plate and nozzle body must be kept free of all dirt or foreign matter. This necessitates the atomizer in each burner being removed and cleaned each watch by the fireman. To do this both burner shutoff valves and the air register are closed. This stops the oil from entering the atomizer and prevents unnecessary cold air from blowing into the firebox while the burner is shut down. The yoke is then slacked off and the complete atomizer drawn out of the burner barrel first allowing the small amount of fuel oil in the atomizer to drain into the drip pan hanging beneath the burner. A spare cleaned atomizer is then installed by sliding it into position in the burner barrel and connected to the oil line by tightening the yoke. Make sure this yoke is tight otherwise hot oil will spray out into the fireroom when the burner valves are opened. A torch consisting of a steel handle about three feet long with a small ball of braided asbestos soaked in kerosene at one end is lighted. This is inserted through an opening in the front of the burner to permit the flaming torch to be directly in front of the sprayer plate. The burner valves are then opened, permitting the oil to rush through the atomizer emerging in a fine mist where it is ignited by the torch. The air register is then opened wide permitting air from the forced draft blower to enter and mix with the atomized oil. When the burner is operating the air register is always in the wide open position. When shut down it is fully closed. There is no intermediate adjustment.

  permanently distort the atomizer, ruining it for further use. Back off the tip nut with the burner wrench. The sprayer plate is then lifted off with the fingers and washed in kerosene. Never use anything but a pointed stick or a copper wire for removing carbon or other sticky substance. A knife or steel nail will scratch the metal surface and enlarge the orifice which destroys the effectiveness of the atomizing action. Remember the sprayer plate is an accurately machined part which must remain that way to atomize the oil. After the four holes in the nozzle body have been cleaned the sprayer plate is replaced and the tip nut screwed on and tightened with the burner wrench. The B. & W. oil burner has a small fine mesh strainer in the entering end of the atomizer which must also be removed and cleaned each watch.

Sprayer plates are made in sets, each set having a different sized orifice. The larger the orifice the more atomized oil can enter the firebox, so when the oil pressure is at its highest permissible working pressure and more steam is needed, the burners will have to be shut down one at a time and sprayer plates with a larger sized orifice installed in the atomizers. Size numbers are stamped on the outside face of all sprayer plates, the engineer determines what size sprayer plates are to be used.

In the burning of atomized fuel oil the proper amount of air must be supplied at all times. Not enough air will cause incomplete burning of the fuel which causes black smoke to pour out of the stack. Too much air causes a chilling of the fire, with white smoke coming from the stack. In peacetime smoke is a sign of fuel being wasted. In wartime it can easily result in an attack by the enemy, for smoke rising into the air can be seen for many miles by a prowling enemy submarine. It is most important that the fires be carefully tended to eliminate all smoke.

BURNER TORCH

Always stand to one side of the burner when lighting of and do not look into the firebox. Should a flareback occur flame may shoot out in your face.

To clean the dirty atomizer it is placed in a special non-adjustable vise secured to the fire-room work bench. If it should ever be necessary to place the atomizer in an adjustable jaw vise do not squeeze it too tightly as to do so will

VARIABLE CAPACITY BURNER

Oil Burners in General-Modern burners have two basic parts: the fuel oil atomizer which breaks up the solid oil stream into spray and the air register which controls the air admitted for combustion and directs the flow of air into and around the oil spray. Most burners have changeable tips to provide for changes of load; the variable capacity burner uses one tip for all loads.

 

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Variable Capacity Atomizer and detail sketch of sprayer plate.  

Variable Capacity Burner-This type of   from the orifice plate into the furnace in a

burner is designed primarily for boilers using forced or induced draft. The oil supply is constantly recirculated as indicated by the arrows on the enlarged drawing of the atomizer. The oil enters the large supply tube and flows toward the tip. The oil supply pressure is kept constant. The orifice plate and the sprayer plate change this pressure to velocity and give the oil a swirling action. Some of the oil is now forced into the smaller outside passages and will return to the day tank if the oil return line valves are open. The oil which is not returned will emerge

hollow conical shaped spray of very small particles of atomized fuel oil.

Closing the return oil line shutoff valves stops the flow of oil away from the burner. This increases the amount of oil sprayed into the furnace and, if the mixture of air and oil is proper for good combustion, the capacity of the burner can 'be increased for hard steaming.

When the shutoff valves in the return line are opened, oil flows out of the burner and the air is cut down, reducing the size of the flame. In this manner the burner can be adjusted for any load without changing the burner tip or the pressure on the service pump.  

51 

Sketch showing oil flow to and from burner.

All burners on one furnace can be controlled by one Return Control Valve as shown above.    

52 

REMEMBER-A SMOKING STACK INVITES ATTACK SMOKE PREVENTION

  In wartime a smoking stack is to be avoided at all costs, for information secured from the enemy reveals that large convoys have been attacked when their position was given away by smoke from a single ship in the convoy. This can be easily understood when it is realized that under the best of conditions a ship can be seen by a submarine from a distance of not more than 12 miles. Under ideal conditions smoke is visible 30 or more miles. To keep the ship from smoking requires

  from the stack. Oil pressure should not be exceeded one way or the other. When this becomes necessary, change to larger or smaller sprayer plates. Don't fail to clean the burners regularly, for one dirty atomizer can make smoke. Keep a close eye on the draft, for too little will positively result in black smoke. In the daytime it is better to carry a little more draft than necessary than not enough. At night excessive draft may blow sparks into the air above the ship so keep the draft where it should be.

constant alertness on the part of the engine room crew. When burning coal, thin fires should be carried, the coal being shoveled in the furnaces in relatively small amounts. With oil fuel, the temperature of the oil must be kept at the proper degree, for if it drops below any considerable amount, black smoke is sure to pour

The sootblowers must not be used except when authorized by the engineer as the ship is bound to smoke while this is going on.

Remember-keep a clear stack.

 

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FIRE EXTINGUISHERS IN FIREROOM  

In all firerooms of oil burning vessels this fire-fighting apparatus is required by law:

Sand-A minimum of ten cubic feet, contained in a metal receptacle, and provided with a scoop. This receptacle should be kept full at all times with sand and the scoop never used for anything except fire fighting.

Hand System-Either of the following: Two 2 1/2-gallon foamite extinguishers or two 15-pound carbon dioxide extinguishers.

Portable System-Either of the following: One 40-gallon foamite extinguisher or one 100-pound carbon dioxide extinguisher.

Permanent System-This consists of perforated piping running under the floorplates through which the fire extinguishing agent passes. This agent may be steam (although steam is now losing its rank among agents), carbon dioxide, or foamite. The fire extinguishing agent is released from some point outside the fireroom; before it is released, all persons

  should be warned to leave the fireroom. After such a system has been used, no one should enter the fireroom until it has been found that there is enough oxygen for human existence.

It is the generally accepted theory that water is not good for oil fires. Nor is it good, if played on the fire under pressure and in the form of a powerful stream from a nozzle. However, there is on the market, and has been accepted, a special nozzle which sprays the water in a fine mist in the fireroom. Now, as long as this special nozzle is used water is accepted as an oil fire extinguishing agent. Some vessels use this as their portable system.

When a fire is discovered act quickly, for a small blaze may be easily extinguished by throwing sand on it or using a hand extinguisher whereas a few moments' indecision may result in a conflagration beyond all control. Remember the ship is your world until you are back on land, so take care of it.

 

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RAISING STEAM  

In preparing to raise steam on a dead boiler it is necessary that the following accessories and valves be closed: Bottom blow valveSurface blow valveBelly plug, Scotch boilersAll feed stops and checksSalinometer cock

Drain on gage glass or water columnAll steam stopsWhistle valveAll manholesAll handholes

The following valves should be opened:

The air cockSafety valve

Top and bottom connections to gage glass and water columnValve to steam pressure gage

If there is no water in the boiler, it is put in

  above the proper temperature will cause carbon deposits in the fuel oil heaters, waste steam, and will cause the burners to pulsate. Whenever the oil is at the proper temperature and pressure, the burners may be cut in.

The burner nearest the center of the boiler is lighted first. A torch is lighted, the air register closed, the torch inserted into the furnace, the oil turned on, and then the air register is opened again.

The boiler should never be forced, and the burners which are lit should be shifted from center to wing to opposite wing, etc., so as to heat the boiler evenly throughout. Steam should never be raised too quickly in any boiler. In Scotch boilers this tends to distort the entire boiler shell, causing ruptures of the tubes,

through the main feed line, if possible, until the water just shows in the gage glass. Then water is put in through the auxiliary feed line to be sure this line is operating properly. After the water is at the proper level the feed stops and checks are all closed again.

Before lighting off an installation of oil burners, the boiler furnaces should be blown through with air to drive out the gases or vapors from the oil which may have accumulated there. This is done by opening the air doors in the registers of several of the burners. Atomizers must be clean, and all valves on pipes leading to the individual burners should be closed. The oil is circulated through the recirculating line until the oil right up to the burner is at its proper temperature, and pressure.

If the temperature of the oil is not high enough to maintain the proper low viscosity, it will be difficult to atomize the oil properly resulting in smoke conditions and carbon deposits in the furnaces. Excessive heating of the oil

furnaces, or the shell itself. In watertube boilers, raising steam too quickly is not injurious to the boiler itself, but the rapid temperature changes cause furnace brickwork troubles. The bricks tend to buckle and the walls will soon tumble down.

Never in any event, for any reason, should the fires be lit in any boiler without using a torch to light them. It is imperative never to attempt to light fires from hot brickwork. The results of such practice always lead to flare-backs which, although they may not be serious enough to cause injury to the fireroom personnel, will still cause extensive damage to the furnace walls.

When steam blows out of the air cock it should be closed. Likewise the safety valves. Pressure should start to show on the pressure gage very shortly thereafter. Bring the steam pressure up slowly until equal with the live boilers and cut in on the line by carefully opening the auxiliary steam stop valve.

 

55 

REMEMBER-ALWAYS USE A TORCH TO LIGHT A BURNER DUTIES OF A FIREMAN

 

The fireroom watches are of four hours each. This means that in 24 hours there are six watches; the 12-4, 4-8, and 8-12 A.M. and P.M. A fireman stands an A.M. and a P.M. watch, with eight hours off in between.

The oiler on watch rings "two bells" on the engine room bell at ten minutes before the relieving hour. The relieving fireman enters the fireroom at this time and begins his inspection of the plant.

The first and most important thing that the fireman must do on entering is to look at the boiler gage glasses. Make certain that the water in the boiler is at its proper level. If the fireman is responsible for tending the water in the boiler, blow the glasses down to ascertain the accuracy of the water level. The fireman works under the direction of the watertender if one is on watch.

The fireman then makes an inspection of the fires and the burners. Take note of the condition of the tile cone around the burner front to see if there is any carbon built up in front of the atomizer upon which the oil will impinge. Look for oil leaks at the connections of the oil lines and burners. Inspect the fireroom and the tank tops below the floor plates for oil drippings that may cause fires. Make sure that all spots of oil are wiped up on the floorplates and in the pans below the burners. Take note of the pressure gage readings at various points in the oil line to ascertain the conditions of the oil strainers. Check the oil heaters by looking at the thermometer on the oil line to see if the proper temperature is being maintained. Look in the fireroom bilges to see that they are

  empty, check the pressure of the oil in line at the gage nearest to the burners, and then the steam pressure of the boilers. After everything is apparently all right ask the fireman who is going off watch if he has had any trouble during his watch, and if there are any special orders for you from the engineer. If all is found to be as it should be, take over the watch, relieving the fireman on duty of all responsibility. 55

The fireman should never be lax or late in his inspection when relieving a watch. Always remember that when you relieve the other man, the full responsibility for the maintenance of the fireroom is yours for the next four hours. Whatever conditions may exist, regardless of who is to blame, the responsibility will be yours alone.

Always allow yourself enough time to make your complete inspection before eight bells ring in the engine room. This marks the beginning and ending of the watches. Never make a man you are relieving remain below after his watch is over unless you find something wrong due to his negligence while he has been on watch. In this case do not relieve him until he has remedied the condition.

After taking over the watch, the next problem is to make sure that everything goes smoothly during your watch. Change over the suction and discharge strainers and clean the ones that have been in use, replacing them in the body of the strainer, and leave the strainer and floor plates around the strainers clean for the next watch.

Next change all burners. These are changed

 

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alternately from boiler to boiler and never more than one in a boiler at a time. While a burner is being changed it is out of use for the few minutes that it takes to complete the operation. During these few minutes, there is the same amount of water entering the boiler

  on the tubes of the boiler causing considerable loss of efficiency and a lot of work.

The fireman must watch his plant at all times just as the engineer watches his.

as before but there is less steam being made. Therefore an excess amount of water accumulates, raising the level in the boiler. After the burners have been changed and cleaned, the strainers changed and cleaned, and the watch is running smoothly, the fireman's duty is to make an inspection of the plant at definite intervals. Don't just sit down and wait for your relief. Trouble is a thing that will come quickly to the lazy fireman. A small speck of dirt the size of a pin point can stop up a burner to the extent that the direction of the oil spray can be diverted enough to strike the brickwork of the furnace. This oil does not burn but cokes and forms carbon on the brickwork. This carbon continues to build up and in the short period of a half-hour a piece of carbon large enough to completely block the burner opening can form. This will cause improper combustion in the furnace and soot will form

Each fireman is responsible for keeping a part of the fireroom in a neat and tidy condition. The particular part being known as your station. The painting, shining of bright-work, etc., connected with this station is done by the fireman while he is on watch. However, this work is never in such a part of the fireroom that at any time the performance of these duties interferes with the safe operation of the boilers. At all times, the fireman should be at a point where his water gage and steam pressure gage are visible.

A fireman should do everything possible to maintain the boilers in a safe operating condition at all times with a maximum of efficiency. You should be familiar with the pipe lines and auxiliary machinery in the fireroom and know how to prevent and combat fires that may start at any time.

Keep a close watch on the stack for smoke, either by looking at the top of the stack itself or through the smoke density indicator.

 

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DUTIES OF A WATERTENDER  

The watertender is carried aboard ships which have several boilers and where the

  affects the water level in the boiler, the water-tender must direct the fireman ill his duties. He

tending of the water in the boilers requires constant attendance. Some boilers, such as the Scotch boiler, although they require constant attention do not require that a change in the setting of the check valves be made often. Other boilers require frequent change in the setting of the check valves in order to maintain the proper water level in the boilers.

The duties of the watertender include the following: Be thoroughly familiar with the construction of the boilers, the accessories connected with them, and know their purpose and operation. These accessories include the external and internal feedwater lines, and the stop and check valves that control the feeding of the water to the boiler, the safety valves, the main and auxiliary steam stop valves, the steam pressure gage, the water column and gage glasses, the injector, the feed pumps, try cocks, bottom and surface blowdown valves and piping connected with blowing down the boiler, the hand release on the safety valve, superheater drains and connections, air cock, all valves used in conveying steam from the boiler to all parts of the ship, sootblowers, etc. The watertender must at all times be aware of the hazards incurred from low water and maintain a safe level in the boilers.

Because the firing of the boiler directly

oversees the fireman and as a rule, is responsible for maintaining a steady steam pressure in the boiler.

When the boilers are supplied with automatic feedwater regulators, the watertender should be familiar with their operation, and should never rely entirely on their operation, but still maintain a constant surveillance of the water level.

The watertender must have a thorough knowledge of the engine and fireroom firefighting equipment.

The watertender should be thoroughly familiar with the safe handling and burning of fuel oil. He must be able to properly operate the fuel oil system from the tanks to the burners. This requires a thorough knowledge of all the oil burning equipment including the transfer lines and pumps, valves, manifolds, etc., strainers, service pumps, heaters, control valves, atomizers, and regulating valves.

He should have a good working knowledge of draft, and the particular draft equipment on the vessel on which he is employed, for it is his duty to minimize smoke conditions at the stack, and maintain good furnace conditions.

In short, the watertender should be able to operate and maintain the fireroom watch with as little assistance from the engineer as possible.  

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THE WIPER'S JOB  

The wiper is not a qualified member of the engine room in the true sense of the position. He is an all-around worker in the Engine Department of an oil-fired vessel. His is the only position open in that department for beginners and others not qualified in the more responsible ratings. The wiper washes paintwork, chips, scrapes, paints, and performs all those various duties tending to maintain the machinery spaces in a clean condition.

Generally he is a day worker, and is not assigned to a watch. He should, as quickly as possible, familiarize himself with the hazards of using oil fuels, and operating pressure vessels.

Since he is first, last, and always a seaman, he should be familiar with nautical terms. He should realize the importance of emergency drills, know his stations in each, and be able to fulfill his part should the necessity arise to combat fire or abandon ship. As an engine department worker he should have an interest in mechanics, and be familiar with the names and the purposes of all the units in the power plant of the vessel.

Where overhauling and repair work of boilers

  and machinery is carried on, the wiper helps in various ways, and it is through the knowledge that he gains while doing this work that he prepares himself for advancement.

The records of all successful men show that they were not afraid to assume additional duties. They were not hesitant about asking questions-nor did they begrudge a small portion of their leisure time for study.

This applies to any line of endeavor and even if the job is temporary, the knowledge gained will always be useful.

Duties aboard ship, particularly in the engine room, are unique in the large number of opportunities available.

The operation of a ship's engine room covers many subjects. There is much to learn that is both interesting and profitable-get as much as you can, make the most of your opportunities. Help the oiler, the fireman, the water-tender, learn the other fellow's job and don't hesitate to do a little extra work. Use at least part of your leisure time every day to read about the equipment around you. Every Chief Engineer was once a wiper who took advantage of his opportunities.

 

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RECIPROCATING STEAM ENGINES  

Reciprocating type main engines have been used to propel ships, since Robert Fulton first installed one in the Clermont in 1810. The Clermont's engine was a small single cylinder affair which turned paddle wheels on the side of the ship. The boiler was only able to supply steam to the engine at a few pounds pressure. Since that time the reciprocating engine has been gradually developed into a much larger and more powerful engine of several cylinders, some having been built as large as 12,000 horsepower. Turbine type main engines being much smaller and more powerful were rapidly replacing reciprocating engines, when the present emergency made it necessary to return to the installation of reciprocating engines in a large portion of the new ships due to the great demand for turbines. It is one of the most durable and reliable type engines, providing it has proper care and lubrication.

Its principle of operation consists essentially of a cylinder in which a close fitting piston is pushed back and forth or up and down according to the position of the cylinder. If steam is admitted to the top of the cylinder, it will expand and push the piston ahead of it to the bottom. Then if steam is admitted to the bottom of the cylinder it will push the piston back up. This continual back and forth movement of the piston is called reciprocating motion, hence the name, reciprocating engine. To turn the propeller the motion must be changed to a rotary one. This is accomplished by adding a piston rod, crosshead, connecting rod, crank and crankshaft. When the piston goes up and down it pushes the piston rod up and down with it. This through the crosshead pushes the connecting rod, the bottom end of which is attached to the crank. The crank is

 to be effective the piston rod must travel in a straight line and not move from side to side. This is accomplished by the guide and slipper shown in the drawing.

SIMPLE ENGINE(Valve and valve gear not shown)

The slipper or shoe, as it is known, is attached to the crosshead and as it travels up and down the slipper is pushed by the angularity of the connecting rod against the guide which is a flat

merely an arm, one end of which is fastened to a round shaft (crankshaft) free to revolve in a fixed bearing and the other end to the connecting rod. As the connecting rod is pushed up and down it pushes the crank around in a circle the hub of which is the crankshaft. A propeller attached to the end of the crankshaft will revolve at the same speed as the crankshaft.

The hole in the center of the lower cylinder head through which the piston rod passes must be sealed otherwise steam will blow out. Packing is installed around the piston rod in the stuffing box for this purpose. For the packing

lubricated metal surface in line with the cylinder. Thus it is impossible for the piston rod to move sideways in its travel.

 

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TRIPLE EXPANSION RECIPROCATING STEAM ENGINE FOR EC-2 (LIBERTY) SHIP 1. BEDPLATE2. COLUMNS3. CYLINDERS4. GUIDE5. PISTON ROD6. PISTON ROD PACKING7. CROSSHEAD

8. CONNECTING ROD9. CRANKSHAFT COUPLING10. JACKING ENGINE AND GEAR11. AIR PUMP BEAM12. DEPENDENT AIR PUMP13. REVERSING ENGINE14. THROTTLE.

 

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The alternate entry of steam to the top and bottom of the cylinder is made possible by an automatic valve (C) shown in the side view of a simple engine.

As shown in the sketch steam from the boiler enters the steam chest through the steam line (A) completely filling the chest (B). The slide valve, which is somewhat in the form of the letter D is in the down position, uncovering

SIMPLE ENGINE-CRANK ON TOP CENTER

In the above sketch the crank is shown in the top center position. The arrows indicate the direction of force and the movement of the piston. The valve will move up to cut off flow of steam to top of piston.

 the top steam port (hole between the steam chest and cylinder) which allows the steam to flow into the top of the cylinder. When the piston has been pushed downward a short way the valve moves up, covering the top port, stopping the steam from entering. The steam in the cylinder expands pushing the piston ahead of it to the bottom of the cylinder. As the steam expands its temperature and pressure drop due

SIMPLE ENGINE-CRANK ON BOTTOM CENTER

The above sketch shows the crank on bottom center and the arrows below the piston indicate the upward force of the steam. In this case the valve will move down to cut off the flow of steam.

 

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to its energy being converted into mechanical work. When the piston reaches the bottom of the cylinder the valve in the steam chest moves up still further, uncovering the bottom port which permits steam to flow into the bottom of the cylinder where it expands and pushes the piston back up in the same manner.

The steam which pushed the piston down is exhausted from the cylinder through the top cylinder port to the hollow underside of the valve where it is directed into the exhaust chamber and exhaust pipe. The steam exhausting from the bottom of the cylinder passes out the bottom port to the underside of the valve to the exhaust chamber and pipe in the same manner.

The slide valve is moved up and down on its seat by the eccentric on the crankshaft. The eccentric is merely an off center or eccentric wheel keyed onto the crankshaft. As the crankshaft is revolved, the eccentric turns, pushing the eccentric rod up and down in the same manner as a crank. The top of the eccentric rod is connected to the slide valve by the valve stem.

This type valve is used in nearly all marine reciprocating engines.

With engines having more than one cylinder, each cylinder has its own steam chest and valve. The valves must be kept in proper adjustment, otherwise one cylinder would be doing more work than the other resulting in loss of power and fuel wasted.

CYLINDERS

Cylinders are made of cast iron, the top head being readily removable. The cylinders are supported in position by the columns. Steam engines may have one or more cylinders, a popular size installed in cargo vessels having three.

 are used in practically all main engines today especially in high pressure cylinders. These employ a separate spring to provide the tension for holding the piston ring out against the cylinder wall. By adjusting the tension of the spring the tightness of the ring is determined. If the rings are not kept properly adjusted steam will blow by the piston, resulting in loss of power and steam wasted. This can usually be detected by the readings of the cylinder pressure gages.

Lubrication must be provided between the piston rings and cylinder wall.

PISTON ROD

The piston rod is round, made of steel, the top end is secured to the piston, the bottom end to the crosshead. To prevent steam from blowing out of the cylinder around the rod, metallic type packing is installed around the rod in the stuffing box.

PISTONS

A piston is made of cast iron and acts as a sliding round plug inside of the cylinder. It is secured to the piston rod by a nut.

PISTON RINGS

To prevent the steam from flowing through the clearance between the piston and cylinder walls piston rings are installed. They are constructed of fine grade cast iron and have a sliding fit in a groove around the outside of the piston. The plain snap type piston ring is made oversize and is held out tight against the cylinder wall by the tension in the ring, set up by its having to be compressed when installed. Improved piston rings of several different designs

METALLIC PACKING

METALLIC PACKING

The cut-away view of a set of one type of metallic packing in place on a piston rod shows that the two metal rings (6) are the only parts  

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in contact with the rod. The metal used in this type packing is relatively soft, being a form of babbitt. The coil springs (10) provide the tension to hold the rings tight around the rod. The piston rod sliding through the metal rings must be lubricated otherwise the friction will cause overheating.

CROSSHEAD

A crosshead is a square steel block rigidly fastened to the bottom end of the piston rod. On the forward and after side of the block is a round steel pin known as the crosshead pin, around which the crosshead bearings fit. These bearings are rigidly fastened to the top of the connecting rod fork and in operation the

  CRANKSHAFT

The crankshaft is a large round steel shaft to which the cranks are attached. Those portions of the shaft which revolve in the main bearings are known as journals. Mounted on the shaft are the eccentrics.

ECCENTRICS

The eccentrics which move the engine valves up and down are merely an off center or eccentric wheel secured around and keyed to the outside of the crankshaft. Two are required for each valve, one being for ahead motion and one for astern. The motion of the moving eccentric is transmitted to the eccentric rod by

bearings revolve back and forth around the pins and must be lubricated.

To the back side of the crosshead a slipper is attached.

SLIPPER

A slipper is made of cast iron with the flat bearing face being coated with babbitt metal. Some engines have one slipper and some two depending on whether it is a single or double guide engine. The great proportion of engines being built today being of single guide construction, the text will deal with that type.

GUIDES

The ahead guide is a flat face made of cast iron and bolted against the column. The astern guide consists of two cast iron side bars which fit around the outside of the slipper preventing it from being pulled away from the guide when the engine is turning in the astern motion. Lubrication must be provided between the sliding metal faces of the slipper and guides.

Guides are usually cooled by sea water passing through a core in the back of the ahead guide face.

CONNECTING ROD

The connecting rod is made of steel, the top end usually being forked in large engines and attached to the crosshead with bearings so that the crankpin is free to turn as the crank goes around. The crankpin bearing must be lubricated also.

CRANK

The crank is constructed of steel and consists of the following parts. Webs which are the two side pieces connecting the crankshaft with the crankpin. Crankpin which is a round steel pin between the outer ends of the crank webs, around which the crankpin bearing is fitted.

the eccentric strap which extends entirely around the outside of the eccentric, the eccentric turning inside of it. The inside surface of the strap which bears on the eccentric is either lined with babbitt metal or bronze. Lubrication must be provided between the strap and eccentric.

COLUMNS

The columns are made of hollow cast iron, box construction and are used to hold the cylinders and steam chests in position, two columns supporting each cylinder and chest. The columns stand on and are bolted to the bedplate.

BEDPLATE

The bedplate is securely fastened to the ship's hull forming a true surface for the main bearings and columns. In assembling, the bedplate must be true and ridged, otherwise the engine will be thrown out of line.

MAIN BEARINGS

The main bearings support the crankshaft, one being required on each side of every crank.

The bottom halves are fitted into a recess in the bedplate, all bearings being in direct alignment. When the crankshaft is lowered into place, the top half of the bearings are put on and adjusted for clearance after which they are secured with bolts which extend through the bedplate.

The inside surface of the bearings is lined with babbitt metal requiring lubrication. This is supplied through oil holes leading from the top of the bearings through to the shaft. Oil grooves cut in the face of the babbitt metal enable the oil to spread evenly the length of the bearings. The revolving shaft carries the oil entirely around the bearing

 

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providing an unbroken film which keeps the metal of the bearing from coming in contact with the journal. This principle of lubrication applies to all bearings.

The lower half of main bearings on larger engines is usually cooled by sea water flowing through a core in the bearing shell.

CRANKPIN BEARING

The crankpin bearing is bolted to the bottom end of connecting rod and of same general construction as main bearings. Lubricated from oil cups on the crosshead, the oil passing down oil lines on the forward and after side of the connecting rod.

CROSSHEAD BEARINGS

The crosshead bearings are bolted to the top end of the connecting rod and may be constructed of brass or with a babbitt lining. Lubricated through an oil cup on top of the bearing.

  VALVES AND VALVE GEAR

The D-type slide valve is held on its seat by the steam pressure pushing against the back of it. This sets up considerable friction which requires a great deal of power to move the valve when high steam pressures are used. For this reason, another type of valve is used to a great extent on marine engines. This is known as a piston valve, and is, in fact, a flat slide valve developed into the form of a cylinder, presenting no flat surfaces upon which the steam may act.

STEPHENSON LINK VALVE GEAR

The piston valve consists of two pistons joined by a hollow casting as shown in the drawing. The valve slides inside two removable sleeves or liners which form a cylindrical valve seat. Steam ports communicating with the ends of the cylinder are cored into the sleeves. The valve is secured to the valve stem and is

PISTON VALVE

controlled by the eccentric the same as a flat slide valve.

 

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The steam may enter at the center of the valve, or at the ends of the valve. The exhaust piping connects just the opposite from the steam inlet. In the drawing, the steam enters at the center, and this is known as an inside valve. It is impossible to use a slide valve as an inside valve, as the steam pressure acting under the valve would force the valve from its seat. Therefore, a slide valve is always an outside valve.

If steam pressure is allowed to enter the cylinder during the full stroke of the piston, it would be a very expensive engine to run. For this reason, the steam is permitted to enter the cylinder only during part of the stroke. During the rest of the stroke, the steam expands in pushing the piston through the cylinder. Thus the expansive quality of the steam is used for

 has no up and down movement. By using this knowledge, if the link is moved from one eccentric, a short distance toward the other, the amount of steam that will be admitted to the cylinder will be less than if the valve stem were directly over the eccentric rod. By moving the link in this fashion, the valve travel will be less. With less valve travel, total distance the valve moves, the valves will close the steam port to the cylinder earlier in the stroke, cut-off is sooner. With earlier cut-off less steam is admitted to the cylinder which takes us back to the statement, that if we move the link from one eccentric a short distance toward the other, the amount of steam that will be admitted to the cylinder will be less and the amount of work accomplished is less. The amount of steam admitted will be less due to a shorter valve travel giving an earlier cut-off.

doing work.

As the marine engines must be reversible in order for the ship to be made to go ahead or astern, we must have some way to cause the reciprocating engine to run in the opposite direction. In almost all types of reciprocating engines used on board ship for propulsion, we use the type of valve mechanism shown in the drawing. This consists of two eccentrics (A) and what is known as a Stephenson link. One eccentric is set to control the valve for go-ahead motion and the other eccentric is set to control the valve for go-astern motion.

An eccentric rod (C) is run from one eccentric to one end of the link (E) and another eccentric (D) to the other end of the link. This is clearly seen in the drawing. The link is made to slide along a block (F) attached to the foot of the valve stem (G). The valve is thus moved by the eccentric whose eccentric rod is directly beneath the valve stem. This type of link is known as the Stephenson link.

The link is made to move by a reversing ram or reversing engine. The engine or ram turns a rock shaft (H), mounted on a back column, by means of a connecting rod. The rock shaft connects to the Stephenson link by means of drag links or tie rods (I) as shown in the drawing. The rock shaft in turning through a part of a revolution throws the links from ahead to astern, or from astern, to go ahead, as the case may be.

If the link is moved until the center of the link is directly under the valve stem, with the throttle open, the engine would not run. This is due to the fact that the eccentrics operate against each other and the center of the link

On marine propulsion engines, it is possible to move the links on each individual engine by the use of an individual cut-off gear which has the reversing rocker, or the rock shaft, slotted at the end. The tie rods, reaching from the Stephenson link to the reversing rocker are attached to a movable block, that is closely fitted into the slot. By means of a screw, the block may be readily moved to the right or left, thus moving the link either toward mid-gear or full gear ahead, without affecting the other links. That is, the cut-off on the H. P. and M. P. and the L. P. may each be independently adjusted with the engine stopped or with the engine in motion.

When the rock shaft is turned to its astern position, the slot in the reverse rocker arm will be vertical, and thus the cut-off gear has no influence on the astern power of the engine.

REVERSING ENGINES

On the Liberty ships a reversing engine is used to move the Stephenson links from ahead to astern or astern to ahead. This is known as "throwing the links." The reversing engine is a small single cylinder steam engine with the cylinder on the bottom and crankshaft on top as shown in the chart on page 68. The reversing engine is controlled by a lever on the H. P. front column.

As the reversing engine runs, the rotary motion of the crankshaft turns the worm which is keyed on the reversing engine crankshaft. The worm meshes with the worm wheel and causes it to turn. The pin is connected to the reversing shaft of the reverse gear by a drag

 

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rod. Half a revolution of the worm wheel causes the connecting rod to the rock shaft to turn the rock shaft sufficiently to throw the links from ahead to astern or astern to ahead

 end of the chest where it enters the right-hand end of the engine cylinder through the open port. This starts the engine rotating in a clockwise direction.

and thus change the direction of rotation of the main engine.

Differential Valve-As the reversing engine has only one eccentric, the reversing of it is made possible by using a differential valve for controlling the steam and exhaust to and from the steam chest. The differential valve is the top piston valve shown in the cross-sectional sketch.

In the first sketch the differential valve is moved to the right which allows the steam to flow by through the port to the engine steam chest, where the steam passes through the length of the hollow piston valve to the opposite

DIFFERENTIAL VALVE

In the second sketch the differential valve has been moved to the left but the engine valve is in the same position. The steam now enters the engine steam chest from the opposite end of the differential steam chest and passes around the inside of the engine valve from where it flows through the port to the left end of the engine cylinder. This starts the engine turning in the opposite direction as shown by the arrow in the circle.

While the steam is entering one end of the cylinder, the spent steam is exhausting from the opposite end through the ports and valves as shown by the arrows.

The differential valve is moved back and forth by a lever.

Differential valves are also used to reverse steering engines and winches as will be brought out later in the manual.

LINE SHAFT AND SPRING BEARINGS

Except in oil tankers and ore carriers, most vessels have their engine and boiler rooms located amidships. This means that a long steel shaft, as shown in the shaft alley illustrated on page 67, is needed to connect the revolving crankshaft with the propeller. Several bearings known as spring bearings, marked (S), support this shaft at the necessary points along its length. A tunnel, known as the shaft alley, houses the line shaft, from the after bulkhead in the engine room to the afterend of the line shaft at the stern gland. The alley provides sufficient room for the oiler to walk alongside the revolving shaft so that he may feel and oil the spring bearings. Usually only the bottom half of these bearings is lined with babbitt metal, the top half being a cast iron shell which has a relatively large clearance between it and the shaft. The lubricating oil is poured in the top after the cover has been raised, and runs down around the shaft to form a film between the babbitt metal in the bottom half and the shaft.

The C-shaped objects around the line shaft are

guards surrounding the couplings.

TAIL SHAFT AND PROPELLER

The last section of the line shaft is known as the tail shaft. It extends through the stern tube into the sea and on its end is secured  

67 

the propeller. The stern tube is fitted with lignum vitae wood bearings to support the tail shaft. The steel tail shaft is protected from the corrosive action of sea water by a bronze sleeve

SHAFT ALLEY

shrunk on around the outside of the shaft. As the bronze-covered shaft revolves in the wood bearings, sea water flowing in from the sea end of the tube acts as a lubricant. To prevent the sea from flooding the shaft alley and ship, a stuffing box packed with several turns of flax packing is provided at the forward or shaft alley end of the stern tube. When the ship is underway the gland should be slacked off just enough to permit a small stream of sea water to flow out of the stern tube into the shaft alley

 through the water, like a steel screw in wood, pushing the ship ahead of it. If revolved in the opposite direction it screws itself backward through the water, pulling the ship with it.

STERN OF LIBERTY SHIP

Propellers are usually made of bronze to resist corrosion and are secured to the end of the tailshaft with a tapered fit and large nut.

To do their best work, propellers must be designed to turn at relatively slow speeds, 100 R.P.M. or below. With the conventional type, reciprocating main engine, the propeller turns at the same speed as the engine, but with turbine engines which turn at several thousand R.P.M., it is necessary to reduce the speed between the

bilge, to insure that the bearing is being lubricated. It is very important that the outside of the stuffing box be felt by the oilers for overheating at each round, as the packing may overheat and burn up if too tight. Upon leaving dry dock, where the stuffing box has been repacked, an especially close watch should be kept.

In this picture a propeller can be seen in place on a single-screw ship in dry dock. A propeller is simply a large screw which, when revolved in one direction, will screw itself forward

turbine and the propeller.

When the ship is loaded, the propeller is well below the surface of the water, but when light it may break the surface when turning. Extreme care must be exercised when alongside the dock or when anchored that no obstructions, such as small craft, are near the propeller before moving it.

In heavy seas the propeller may frequently break water, causing the engine to race.

Also, in this picture may be seen the rudder for steering the ship and the depth markings in feet on the side of the hull.  

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69 

 

70 

 

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RECIPROCATING STEAM AND WATER CYCLE  

MULTIPLE EXPANSION ENGINES

The single cylinder reciprocating steam engine used extensively to operate ship's auxiliaries would be too inefficient for propulsion. After the steam in the cylinder has expanded and pushed the piston there is considerable heat left in the exhausting steam. It is to put this to work that additional cylinders are added.

Compound Engine-A compound engine has two cylinders, the one in which the first expansion takes place being known as the "high pressure" cylinder, the other as the "low pressure" cylinder. To provide room for the expanded steam and to develop the same amount of power in both cylinders the "low pressure" one will have to be larger than the "high pressure." Compound engines are used mainly in towboats.

Triple Expansion Engines-In ocean going ships engines with at least three cylinders are used. These are known as triple expansion because the steam expands three times.

  In the triple expansion engine used in the Liberty ship, a cross-section drawing of which is shown on page 70, the steam enters the H. P. (High Pressure) steam chest of the engine at about 220 pounds pressure where it is admitted to the cylinder by the H. P. piston type D slide valve. The steam expands in the cylinder, losing temperature, pressure dropping to about 75 pounds per square inch. It exhausts to the M. P. (Medium Pressure) valve chest and cylinder where it expands again, the pressure dropping to about 12 pounds per square inch at which pressure it exhausts into the L. P. (Low Pressure) valve chest and cylinder where it expands for the last time against the large L. P. piston. Equal power is developed in each cylinder. The steam upon exhausting from the L. P. cylinder enters the main condenser through the exhaust trunk. The vacuum of approximately 26 inches maintained in the condenser also is present in the exhaust trunk and in the L. P. cylinder on the exhaust

 

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side of the piston. This adds considerably to the power of the engine.

Other multiple expansion engines are four cylinder triple expansion in which there are two smaller L. P. cylinders instead of one big one and quadruple expansion having four cylinders in which the steam expands.

THRUST BEARINGS

The propeller screwing itself forward through the water will push the tail shaft, line shaft and crankshaft forward through the ship, wrecking the engine unless the shaft is prevented from moving endwise. When the propeller is turning astern, it tends to pull the shafting out of the ship. To prevent this, the thrust bearing is installed on the line shaft just aft of the engine and as the tremendous thrust of the propeller is held in check at this point, the ship is actually pushed here. The thousands of pounds pressure exerted by the propeller create a terrific friction in the thrust bearing requiring excellent lubrication to prevent overheating.

KINGSBURY THRUST BEARING HOUSING

Two types of thrust bearings are in service, the horseshoe or multi-collar, and the Kingsbury. The horseshoe once practically the only type used has been replaced in new construction for a number of years by the

  and horseshoe bearings. The base of the thrust bearing is filled with lubricating oil in which the shaft collars revolve carrying the oil upward between the collars and horseshoes. As the oil falls back into the base, it carries with it some of the friction heat. A sea water cooling coil running through the oil in the base carries a large portion of this heat away.

To help carry away the tremendous friction heat, sea water is pumped through the hollow shoes. The discharge side of the cooling water is open to view so that the oiler can readily see if any of the shoes should plug up. Sea water contains impurities which when heated tend to leave the water and cling to the inside of the horseshoes. By connecting a water or steam hose to the plugged shoe, it can usually be cleared. The horseshoes should be felt by the oiler at every round and the cooling water discharge from each shoe noted.

KINGSBURY THRUST BEARING

The principle of a Kingsbury thrust bearing is shown in the simple sketch. A single shaft collar pushes against several pivoted shoes which are held in place by a stationary seat fastened to the hull of the ship. When the shaft is revolved, the shoes pivot to allow the film of oil between the collar and the shoes to take the form of a wedge. The wedge of oil can

Kingsbury. In the horseshoe type, the shaft was made with several circular collars a few inches apart along the shaft. Fastened through the thrust bearing frame to the ship's hull, horseshoe shaped bearings are placed between the rotating shaft collars. As the propeller starts to thrust forward or backward, the shaft collars immediately come up against the babbitt face of the horseshoes which stop the forward or backward movement. Lubricating oil must be continually supplied between the face of the shaft collars

withstand tremendous pressure without breaking down making it possible to operate a single collar. The entire bearing is encased in a housing, as may be seen in the picture. Lubrication is supplied by the rotating collar dipping in the oil sump.

Kingsbury type thrust bearings require much less space than horseshoe and are more efficient.

 

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  LUBRICATION

Friction is, and always will be, present in every moving machine, for it cannot be entirely eliminated.

Friction is that which resists the motion of either of two bodies when in contact with each other. Friction results in wear and power losses, therefore, there is a great necessity for reducing it as much as possible through the use of lubrication.

  If two pieces of metal were polished to the highest degree possible and placed in contact, under a microscope, it would be found that the two surfaces were jagged. In the sketch is shown a journal in a bearing as it would appear greatly enlarged. In order to reduce friction between the surfaces, a lubricating oil or grease is used to separate the surfaces.

There are three kinds of friction that involve lubrication:

1. Rolling friction; the tire of an automobile on the road.

2. Sliding friction; a journal turning in a bearing.  

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3. Fluid friction; friction set up by the churning of the oil.

Lubrication problems are best understood by a thorough knowledge of its action. When good lubrication is obtained, there is formed in the bearing an oil film which separates the bearing

OILER FEELING CRANKPIN BEARING

surface and the journal of the rotating shaft. This prevents metallic contact. Then, the only friction involved is the fluid friction of the oil. This fluid friction varies with the viscosity of

  the oil, the temperature of the oil, the journal speed, and journal pressure.

The sketches of a journal in a bearing show the conditions existing under different circumstances. In (A) the journal is at rest and contacts the bearing at (T). In (B) the journal is just starting to turn and contact point moves to (S). As the journal turns, the oil film forms and lifts the journal in (C). (D) shows the position of journal in relation to bearing at full speed.

The sketches show the clearances exaggerated for simplicity.

Too much stress cannot be laid on the importance of proper lubrication of all units in any machinery plant. All rubbing surfaces should receive a steady and sufficient supply of oil of the proper quality at the proper temperatures. There is a byword around power plants that oil is cheaper than metal.

On heavy slow-speed engines, such as the reciprocating engine, the lubrication problem takes into consideration the one factor of separating the two rubbing surfaces, therefore,

OILER FEELING CRANKPIN BEARINGS

OILER FEELING ECCENTRICS

only a small amount of oil is required.

In high speed machines, such as turbines, the lubricating problem must not only consider separating rubbing surfaces, but the speed is so great that a large amount of fluid friction, caused by the churning of the oil, is created. This fluid friction generated heat must not remain in the bearing so that the heat is carried away with oil draining from the surfaces. For this reason the pressure lubricating system for turbines has been developed.

With the reciprocating engine the following bearings and sliding parts require lubrication:

Main BearingsEccentricsCrankpin BearingsCrosshead BearingsValve Gear Bearings

Link BlocksGuidesPiston RodsPiston and Valves

Lubricating oil specially compounded to readily emulsify with water is partially fed to the main bearings by wicks located in an oil box on top of each bearing. The oil box must be filled regularly and the wicks kept clean. Additional oil is supplied by hand with a squirt can. Partial lubrication is also supplied to the crankpin, crosshead bearings and guides from brass oil boxes on the side of the cylinders with syphon feed wicks and pipes leading to the oil cups on the individual bearings. Like the main bearings, the remainder of the oil is supplied by hand, the trick being to hit the moving oil cups  

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with the squirting oil from the can. The brass oil cups for the crankpin and crosshead bearings are located on the crosshead, being of good size and filled with horsehair to prevent the movement of the engine from throwing the oil out of the cup before it has a chance to run down into the bearing. The hair is held in place by small copper wire and must be cleaned frequently.

  sound in the cylinders of a moving engine is evidence of water and the drains should be opened at once.

Relief Valves-In an effort to prevent this damage, spring type relief valves are installed at the top and bottom of each cylinder. When the piston tries to compress the water between it and the head, excessive pressure is built up which opens the relief valve, allowing the

Small brass oil cups filled with horsehair are located on the eccentrics, various valve gear bearings, and air pump drag link and beam bearings. These bearings are usually oiled entirely by hand.

A metal comb attached to the bottom of the crosshead slipper dips into a trough or pan filled with oil and water at the bottom of the guide, carrying this lubrication up on the surface of the guide in addition to the gravity oil feed line.

Lubrication in the form of steam engine cylinder oil is supplied to the piston rods and valve stems by a long handled swabbing brush.

In engines using saturated steam, the particles of moisture in the steam plus what cylinder oil enters the cylinders and steam chests with the piston rods and valve stems are generally sufficient lubrication for the piston rings and valves. However, the newer type engines using superheated steam must have cylinder oil supplied to the valve chests and cylinders. A small mechanical pump forces the oil into the H. P. valve chest from where it travels with the steam through the engine to the various pistons and valves. Excessive lubrication to the cylinders greatly increases the possibility of oil entering the boilers and must be avoided.

RECIPROCATING ENGINE ATTACHMENTS

Drains for Cylinders and Steam Chests-To remove water from the steam chests and cylinders, formed when the steam comes in contact with the cold metal walls when warming up the engine, drain cocks or valves are installed on the bottom of each chest and cylinder. Reach rods are provided so that they may be opened and closed from the operating floor. The drains are piped to discharge into the main condenser where the vacuum speeds the removal of the water. Water may also carry over from the boilers

water to squirt out into the engine room. Faith must not be placed in these as they cannot take care of a very large amount of water.

Throttle Valve-To start and stop the engine and control its speed, the throttle valve is installed in the steam line just outside the H. P. valve chest. It is usually a double seated, balanced valve making it easy to operate. The valve is controlled by either a hand wheel or lever located on the cylinder column at the operating platform. For a quick emergency stop, some engines are equipped with a butterfly valve between the throttle valve and the engine. This operates on the same principle as a damper in a stove pipe and is closed by pulling a lever. In heavy seas the propeller will sometimes come out of the water at frequent intervals which removes the load from the engine, allowing it to race. To prevent its possible destruction the engine must be immediately slowed down by closing the butterfly or throttle valve. This is known as standing a throttle watch.

By-pass Valves-When warming up a reciprocating engine, it is necessary to allow steam to enter the steam chests and cylinders for an hour or so before moving the engine. Without the engine moving, the steam entering through the throttle valve will not pass further than the H. P. cylinder. To supply steam to the M. P. and L. P. a by-pass steam line around the throttle valve is provided. A valve in the bypass line to each cylinder is provided with an extension rod to the operating floor. The bypass valves are also used when maneuvering, as it sometimes becomes necessary to push the H. P. crank off dead center before the engine can be started.

Jacking Gear-When making repairs or adjustments to the engine in port, it is necessary to turn the engine to a desired position in order to place a particular crosshead or crankpin in an accessible position for working. This is done with the jacking gear which is a small single cylinder steam engine fastened usually to the L. P. Column. A worm

into the cylinders when the ship is rolling heavily or the water level in the boilers is carried too high. Water in an engine cylinder is dangerous, as it will not compress when the piston approaches the head, resulting in severe damage to the engine in some cases. A slapping

on the crankshaft of the jacking engine slowly turns a large worm

 

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wheel secured to the main engine crankshaft. The jacking engine is usually reversible which allows the main engine to be jacked in either direction. Never attempt to do any work on the engine in port unless the jacking engine is engaged. The force of the current or tide against the propeller may cause the engine to roll over, crushing you.

Before turning steam on the main engine, the jacking worm must be disengaged from the worm gear or the jacking gear will be severely damaged when the engine starts.

Revolution Counter-In order to determine the number of revolutions the main engine is making per minute, R.P.M., a revolution counter is installed, usually on one of the columns. It operates on the principle of an automobile mileage counter and is operated by a lever from one of the crossheads.

Dependent Air and Condensate Pump-With many reciprocating engines the air and condensate pump is secured to the L. P.

  chest pushing up on the bottom of the balance piston plus the vacuum sucking upward on the top combines to produce sufficient lifting force to remove a portion of the valve weight from the eccentric.

WARMING UP MAIN ENGINE

When preparing a reciprocating engine to get underway the first step is to inspect the engine carefully to make sure nothing has been left in the crankpits and that the engine is generally clear.

The jacking gear worm is next removed.

The main condenser circulating pump is then started up after opening the main injection valve and overboard discharge valve.

Steam and exhaust valves to the reversing

column and operated from the low pressure cylinder through a beam arrangement, one end of which is fastened by connecting rods, called drag links, to the L. P. crosshead and the other end in the same manner to the air pump. As the engine operates the beam acts like a see-saw pushing the pump up and down.

Balance Cylinders and Pistons-With engines having large heavy valves, a small cylinder known as a balance cylinder is quite often located on top of the steam chest covers, directly over the valves. A piston secured to the top of the valves by a short rod is fitted inside the cylinder. The top of the balance cylinder is connected by a pipe line to the main condenser. When in operation the pressure in the steam

engine are opened.

Throttle drain valve is opened.

Main stop on boiler is cracked, allowing steam to flow through main steam line to throttle valve.

Throttle valve is cracked allowing sufficient steam to enter H. P. steam chest and cylinder to warm them up but not enough to move the piston.

M. P. and L. P. by-pass valves are opened sufficiently to warm up these cylinders.

While the cylinders are being warmed the lubricating oil boxes on the various bearings should be filled to proper level and the wick feeds inserted. Lubricating oil should be poured  

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in all oil cups before the engine is moved. Likewise the level of oil in the thrust bearing should be checked and the spring bearings on the line shaft oiled. The eccentric dip pans should be filled with fresh water to proper level.

REVERSING MAIN ENGINE

In the picture the Chief Engineer is maneuvering the main engine. His left hand is controlling the reversing engine and his

  to make a full stroke until certain all water has been worked out of the cylinders. The engine may then be operated very slowly in the direction permitted by the bridge officer until it is thoroughly warmed up.

MANEUVERING MAIN ENGINE

When docking or undocking a ship or moving in congested waters the bridge officer depends upon immediate compliance with his orders as to direction and speed with which the main engine turns. Delay in reversing the engine for example may cause a serious collision. The engine direction orders are relayed from the ship's bridge to the engine room by the engine telegraph. The sketch of the telegraph is shown. The center hand is turned from the bridge to point to the desired direction the engine is to turn and also the speed. As the hand turns a bell rings loudly to attract attention. Immediately the signal is received it is answered by moving the outside handle to point to the same position as the center pointer.

right the by-pass valves. He is watching the Stephenson valve links, so that when they are in the astern position, he may stop the reversing engine. This is done by moving the differential valve control lever to center position.

The engine must not be moved until permission has been secured from the officer in charge on the bridge and the cylinders have been warmed for an hour or two. Then the main stop valve may be opened wide and the engine rocked carefully ahead and astern being careful not

The engine is then reversed, stopped or operated as indicated. The signals are known as bells and are written down usually in a bell book and rough log showing the time received using the symbols shown on opposite page.

When maneuvering, the engine drains are usually left open until underway, although it is sometimes safe to close the H. P. drains when the engine is moving.

As soon as the engine is required to operate fairly consistently the cooling water service should be turned on the thrust bearing, main bearings and guides.

 

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ENGINE ROOM WRENCHES

The following wrenches are principally used in making adjustments or repairs on the reciprocating type main engine of the EC-2 (Liberty Ship).

 

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STEAM TURBINES

PRINCIPLE In order to understand the principle upon which the steam turbine operates, let us first consider the water wheel. In the old type water wheel, the water was piped to the top of a wooden wheel containing blades or buckets. The water filled the buckets and thus turned the wheel, causing the water to spill when the buckets reached the bottom. This is known as an overshot water wheel and is shown in the sketch on the following page.

  A wheel built to make use of water flowing from a higher level, or under greater pressure, uses a nozzle directing a stream of water at high velocity against the buckets. As there was a great deal of splashing from this type, the buckets are made with a curving surface, such as is shown in the sketch. This is known as a Pelton wheel. Steam turbines use blades shaped very much like those of the water wheel. Instead of using a jet of water, steam is directed against the

MODEL OF G-E CROSS-COMPOUND GEARED MARINE STEAM TURBINE

A-H.P. TURBINEB-L.P. TURBINEC-BEARING THERMOMETERS

D-REDUCTION GEAR CASINGE-PROPELLER (LINE) SHAFT COUPLINGF-LUBE-OIL SUMP

 

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blades by a nozzle. The nozzle is so designed that it converts the pressure of the steam into velocity. The steam is usually

  in the nozzle, gives up part of its energy in pushing the row of blades (A), is redirected in the second row of moving blades by the

directed from the side of the wheel against the curved blades.

OVERSHOT WATERWHEEL

TYPES OF TURBINES

Impulse Turbines-Several nozzles are used to direct and give velocity to the steam. The blades convert the velocity of the steam into a rotary motion. This type of turbine is known as an impulse turbine due to the fact that most of the velocity of the steam is converted into rotary motion by the impact or impulse force of the steam on the blades.

PELTON WHEEL

A sketch of the impulse turbine is shown.

The sketch is a single impulse wheel with four nozzles. In the nozzles, steam expands and its pressure is converted to velocity so that the steam leaving the nozzles strikes the plates at high velocity causing the wheel to rotate.

The impulse turbine is built in single stages, as the one described, or in multi-stage, having two or more simple turbines on the same shaft.

stationary row of blades (B). The steam gives

SIMPLE IMPULSE TURBINE

up more of its velocity in the row of moving blades (C). The stationary row of blades is used to reverse the direction of the steam flow.

Reaction Turbines-Another type of turbine is shown as the reaction turbine. The third sketch represents a lawn sprinkler using the reaction principle to cause it to rotate. The water is led to the sprinkler through a hose.

The second sketch shows the position of nozzle, moving blades, stationary blades and the second row of moving blades in a Curtis stage of an impulse turbine. The steam is expanded

 

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The water flows up the vertical pipe into the two horizontal bent arms which end in nozzles. The water is discharged from each nozzle at an

REACTION

increased velocity, and as it leaves, reacts or kicks back on the nozzle, giving a rotating motion to the arms in an opposite direction to the stream of water. It is this reaction force alone that causes rotation of the sprinkler.

The reaction turbine uses a set of stationary

  The fourth sketch shows the blading of a reaction turbine showing two stages. The steam enters the stationary blades (A) which direct it into the first row of moving blades (B). The steam pressure is decreased and the velocity slightly increased in the stationary blades. Thus some impulse is used in this turbine. In the moving blades the steam expands, increases in velocity in leaving and tends to turn the blades by reaction. A second row of stationary blades (C) redirects steam into the second row of moving blades (D), etc., where the action is repeated.

Neither the impulse nor the reaction turbine is caused to rotate by one principle alone, but the impulse turbine has a small amount of reaction involved, and the reaction turbine, a small amount of impulse involved.

Some turbines consist of one rotor in one casing, in which case it is known as a complete expansion turbine. However, to reduce the size

WESTINGHOUSE TURBINE WITH TOP HALF OF CASING REMOVED

of the plant where higher pressures are used, the turbine is compounded; that is, after the steam passes through one turbine, it is led to

reaction shown on turbine

curved blades or vanes which direct the steam into a set of blades mounted on a wheel or drum. The steam expands in these blades, leaving at a higher velocity than that at which it entered, thus kicking the blades around in a rotary path. A reaction turbine contains many rows of stationary and moving blades, each set being known as a stage and the steam being expanded slightly in each row.

another turbine. The first turbine is known as the high pressure and the second as the low pressure. In most cases, the two turbines are placed side by side and are referred to as a cross-compound unit. There are some installations where expansion of the steam is done in three turbines, this being known as a triple-expansion turbine.

The sketch shows a complete expansion turbine which has been used in marine practice. The turbine blading is partly of the impulse, and partly of the reaction type. The steam

 

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COMPLETE IMPULSE-REACTION TURBINE  

enters the nozzle chamber (A) and passes through nozzles where it expands somewhat and increases velocity. It then passes through a Curtis stage at (B) consisting of two rows of moving blades separated by a row of stationary blades. After passing through these blades, the steam passes through 21 moving rows of reaction blading (C), together with the same number of stationary blades. The exhaust is taken from (F) and passes to the condenser. This action of the steam drives the rotor shaft (S) in the ahead direction.

Turbines have the distinct disadvantage in that they cannot run backwards. Because it is necessary for vessels to maneuver astern as well as ahead, there is installed a separate turbine of low power for running astern. It operates under high steam pressure, and is located in the same casing of a complete expansion turbine, or in the low pressure casing of a compounded unit.

Because it is imperative that steam is not admitted to the astern turbine while steam is on the ahead, or vice versa, some type of

  In the sketch of the complete expansion turbine the astern turbine (E) consists of a Curtis stage and takes steam from the nozzle chamber (D). The steam pressure is supplied to (D) when running astern as supplied to (A) when running ahead. Marine turbines have comparatively little backing power.

REDUCTION GEARS

There is a great deal of theory attached to the design and construction of a steam turbine, which will not be gone into at this time. However, it might be said that for theoretical reasons, it is impossible to get any form of efficiency from a slow speed turbine unless of tremendous size. So in marine practice, where the saving of space and weight is an asset, turbines are small in size and operate at very high speed, 2,500 to 6,000 R.P.M. This high speed is contrary to the requirements of a propeller for good efficiency. A propeller must turn at relatively low speeds (80-100) R.P.M., therefore, the high speed of the turbines must be reduced to the low speed of the propeller. This is done in one of two ways; either mechanically with reduction gears, or

guarding mechanism is supplied at the throttle valves so that while one is open, the other cannot be opened.

electrically. The electric

 

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method is known as turbo-electric, and in this system the turbine is directly connected to a generator and the high speed generator drives a synchronous or induction motor at low speed, which in turn drives the propeller. In the majority of installations, the speed reduction is effected mechanically, or with reduction gears.

DOUBLE REDUCTION GEARS

There is a small pinion on the turbine shaft which meshes with a larger gear to effect one speed reduction. If the speed is still sufficiently high to necessitate further reduction, there is a pinion on the shaft of this gear which meshes with another larger gear to effect a second reduction. This latter type, known as double reduction gears, is very frequently used.

The sketch shown is an arrangement of one type of double-reduction gear. Gear teeth are not cut straight across the gear, but are either

  strips through which the steam is throttled several times to greatly reduce the leakage pressure. Carbon rings around the shaft and water seals are also used.

SPEED GOVERNOR

Every turbine has a maximum safe speed limit which must not be exceeded, otherwise the blade wheels may explode from the excessive centrifugal force set up and destroy the turbine.

TURBINE LUBE-OIL PRESSURE SYSTEM

To limit the speed to a safe R.P.M., an automatic speed governor is installed on every turbine installation. It is a vitally important piece of equipment and must not be tampered with. One type of governor uses revolving

cut spirally, known as helical gear teeth, or are cut at opposing angles, known as herringbone gear teeth.

SHAFT PACKING

When the rotor extends through the end of the turbine casing, steam is prevented from leaking out and air from leaking into the casing by glands. These consist of labyrinth packing which consists of a series of rows of metallic

weights which swing out by centrifugal force from a center shaft as the speed of the turbine increases. As the weights swing out they act on a series of levers and rods which close in on the steam governor valve, which limits the steam entering the turbine and so the speed.

 

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MODERN TURBINE STEAM AND WATER CYCLE

This modern installation is typical of those used on the T-2 tankers and is similar to that used on Victory and C-type ships. The boilers operate at 450 lbs. per square inch and the steam temperature at the turbine throttle valve is about 750° F. The high efficiency of the steam generating plant is dependent in part upon the high temperature of the feedwater as it enters the boiler.

The method of feedwater heating shown here consists of bleeding high temperature steam from various extraction points on the turbine and using this steam to heat the feedwater for the boiler. Such a system is capable of more than a 10 per cent saving in fuel consumption

because the steam used to heat the feed-water has already been used to turn the turbine and move the ship.

As with all turbine propulsion plants the proper amount of vacuum must be maintained in the main condenser if full efficiency and power is to be realized. Any loss of vacuum causes the turbine rotor to slow down even though the same amount of steam is entering the turbine.  

LUBRICATION

The lubrication of turbines is usually accomplished by the circulation of oil under pressure. The oil is taken from a sump tank and through suction strainers by a lube-oil service pump. The sump tank is equipped with a float to show the level of the oil in the tank. The suction strainers are used to remove any solid particles that might damage the pump. Suction strainers are installed in duplicate, or are duplex, so one may be in service while the other is cleaned.

At least two Tube service pumps are installed

  in the system. Thus, one is a stand-by pump, while the other is in service. The lube-oil service pump discharges through duplex discharge strainers of fine mesh, where any foreign solid matter which passed through the suction strainers is removed. The oil then flows through lube-oil coolers where heat is removed from the oil by passing over coils through which sea water is circulated. The circulating water is usually taken from the discharge of the sanitary pump, although a pump to be used just for this purpose may be installed.

 

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TURBINE LUBRICATION-GRAVITY TYPE SYSTEM  

From the lube-oil coolers the oil flows to each of the bearings of the turbine and to the reduction gears. The amount of oil supplied to the bearings must be sufficient to cool as well as lubricate them. The oil supplied to the reduction gears flows to the gear shaft bearings and between the gear teeth. From the turbine bearings the oil drains out to the gear casing where the oil from the gears and the bearings drains to the sump tank to be used over again.

Some of the oil pumped from the sump is discharged through a relief valve into the lubeoil service tank, thus keeping the service tank full, the excess overflowing through the overflow line, passing down to the sump tank by way of a sight glass where the flow of oil can be observed.

A connection is made from the lube-oil service tank to the bearings and gears through a swing check valve that is kept closed by the oil pressure of the service pump. If this pressure should fail, the oil in the service tank would flow to the bearings to supply the necessary

  lubrication, until the turbine can be stopped. A low pressure alarm is installed to give warning should the oil pressure fall below a safe limit.

Pressure gages are installed on each bearing and on the lines to the gears to show the pressure of oil supplied to them.

Thermometers are installed at various points of the system to show the temperature of the oil entering the cooler, leaving the cooler, and the oil leaving each bearing.

The operating temperatures of the bearings can not be definitely stated, but in most cases should never exceed 130° F., and should never be carried below 90° F. A rise in bearing temperature above normal definitely indicates trouble, which should, of course, be found and remedied immediately.

Water, sludge, and sediment which accumulate in the oil are removed by a centrifugal oil purifier, called a centrifuge. At frequent intervals, the oil is taken from the service or sump tank, and passed through the centrifuge, from which the cleaned oil returns to the sump tank.  

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REMEMBER-A WIPED BEARING MAY STOP YOUR SHIP DUTIES OF AN OILER

  At sea the main engine usually turns at a steady speed although in convoys the speed will quite often be varied from time to time.

  The actual oiling of the machinery takes up but little of the oiler's time. However, he should have the plant under his constant surveillance.

The oiler makes regular rounds usually every half hour feeling all of the various bearings on the main engine and oiling them. He also must swab the piston rods and valve stems. He also feels of the thrust bearing and travels down the shaft alley feeling and oiling the spring bearings and feeling the stern gland and looking to see if sea water is running through. In between his regular rounds the oiler checks the engine room auxiliaries, refrigerating system and steering engine. He should know how to stop the main engine should it become necessary and the engineer were absent.

It is the oiler's duty to learn everything possible in connection with the operation of the vessel's power plant, because when opportunity comes for advancement he will be able to qualify for the position of watch engineer.

All oilers should thoroughly understand the operation of the different types of lubricating oil pressure and gravity systems for turbine lubrication.

The oiler's watch at sea is of four hours, with eight hours off in between. In port on some vessels, his duties consist of day work, while on other vessels his watch is eight hours long, with sixteen hours off in between.

During his watch, the oiler is probably called upon to do one or all of the following. Pump out the bilges, pump up fresh water or ballast tanks, keep an eye on the water level in the boilers and on the fireman, take temperatures of the stack, sea water, filter box, and feedwater for entrance into the logbook, keep oil wiped up off the floor plates and gratings, and on some ships he has a station to keep clean.

In port his work consists mainly of oiling the auxiliaries, and in assisting in the maintenance and repair of the plant. He may be called upon to oil and watch the cargo winches during the night if the cargo is being worked at that time.

His is a responsible job; his negligence may result in damage to machinery to the extent of thousands of dollars.

 

89  PUMPS   A pump, in the ordinary acceptance of the term, is a machine for the transferring of liquids.

All pumps are generally classed under the three purposes for which they may be used. The sketch below shows that pumps are classed according to their purpose, and according to their position with the fluid supply.

CLASSES OF PUMPS

Pumps are used to transfer fluids from one place to another, but for clarity, it will be assumed that water is the liquid being pumped throughout this discussion.

If the pump is located at a distance above the liquid supply it is termed a lift pump. The distance that the pump is above the liquid supply is termed the "lift" of the pump. Some pumps have very little lift, and are used to discharge large quantities of water under little pressure. In this case, the pump is classed as a circulating pump.

Where a pump is to be used for discharging smaller volumes against high head pressures, it is classed as a force pump.

First, consideration is given to the lift pump. Pumps of this class, being located some distance above the liquid supply, demand more consideration on the suction side than on the discharge side.

In order to understand the operation of this class of pump, the theory of vacuum and

  atmospheric pressure must be understood. First of all, there is no such thing as a drawing force, or sucking force as is ordinarily imagined. Flow of fluids is never caused by one pulling from the other, but always caused by one under a higher pressure pushing against the one with the lower pressure.

Atmospheric pressure is 14.7 pounds per square inch and the pressure of perfect vacuum is 0 pounds per square inch. It is impossible to obtain a perfect vacuum. Therefore, it is impossible to reduce pressure down to 0 pounds per square inch, and whenever the pressure is reduced below atmospheric pressure, but above a perfect vacuum, this is known as a partial vacuum. The pressure being above 0 pounds per square inch, then this partial vacuum has a small pressure, but a pressure nevertheless.

Now, the mercurial barometer operates under the fact the atmospheric pressure at sea level is capable of holding up a column of mercury approximately 30", and when the pressure rises, or falls, the column of mercury rises and falls. If water were substituted for the mercury, the water, being much lighter than mercury, could be held up by atmospheric pressure to a distance of 34'. This is only true if the water used is absolutely pure, and assuming that a perfect vacuum is maintained at the top of the column, and that there is no friction involved between the water and pipe.

The lift pump, when it begins operating, does not draw the water into the pump chamber, because, as has just been explained, this is not possible. The pump plunger, however, pumps the air out of its chamber, and displaces the air in the suction line, thereby reducing the pressure in the suction line below that of the atmosphere, causing the atmospheric pressure, acting on the surface of the water through the vent pipe, to push the water up through the suction pipe into the pump chamber, where it may be acted on by the pump plunger, and discharged.

Any pump, in order to lift water must be able to pump air. All pumps can not pump air, and those that can are capable of displacing anything in the pump chamber, and are known as positive displacement pumps.

 

90 

RECIPROCATING PUMPS

Simplex Type-All reciprocating pumps consist of a cylinder in which a close fitting plunger is moved back and forth. A simple type known as a lift pump is shown. This consists of a cylinder and plunger with a suction valve

LIFT PUMP

at the bottom of the cylinder and a valve in the plunger. The illustration shows the plunger on the down stroke, the suction valve is shown closed, the plunger valves are open, permitting air in the cylinder to flow above the plunger as it moves down. On the upward stroke, the plunger valves close, and the suction valve opens, permitting air in the suction line to flow

FORCE PUMP

into the cylinder. After a few strokes the air pressure in the cylinder and suction line are reduced sufficiently to allow the atmospheric pressure to force the water from the supply up the suction line into the cylinder. From here on the pump continues the same action, but moves water instead of air. This type of pump is used for lifting water only. Practically, water can be raised about 25 feet with a lift pump.

A simple sketch of a force pump is shown in

  the accompanying drawing. Water is forced up into the pump cylinder by atmospheric pressure as the pump reduces the pressure in the cylinder and suction line. Instead of admitting air or water to the top of the plunger through a valve, on the down stroke it forces the water or air through the discharge valve. The height to which the water may be forced depends upon the power applied to the plunger. Both pumps described are single acting pumps as they move water out of the cylinder only on every other stroke of the plunger.

The type of pump generally used on board vessels is a double acting pump which works the same as the force pump described, although not necessarily a force pump, except that a suction and discharge valve is provided at each end of the cylinder. Thus, while the plunger is forcing water out a discharge valve at one end of the cylinder, water is forced in the other end through the suction valve by atmospheric pressure.

The valves are not usually arranged as shown in the simple sketch but are as shown in the drawing of a double acting reciprocating pump. (A) is the steam end of the pump, (B) the water end. Suction (E) and discharge decks (F) are provided above the cylinder and the suction and discharge valves are placed on these decks. The discharge deck is placed above the suction deck, a suction chamber is between the suction deck and the cylinder. The ends of the cylinder are connected by ports to the space above the suction valves and are separated by a division plate. (C) is the pump frame between the steam and water ends.

Duplex Type-The pumps which we have spoken of so far are known as simplex pumps, due to one pump cylinder being used. The discharge from this type is irregular due to the plunger reversing its direction after each stroke. For this reason a pump having two cylinders was developed, one plunger starting stroke before the other plunger has finished its stroke. This action gives a much smoother discharge than is possible with the simplex pump.

The duplex pump requires twice the number of valves used in a simplex pump, that is, at least four suction valves and four discharge valves.

In the steam reciprocating pump, the plunger is driven directly by a steam piston through a piston rod. Steam is admitted to first one end of the steam cylinder and then to the other, moving the steam piston back and forth. The

 

91 

DOUBLE ACTING RECIPROCATING STEAM PUMP A-STEAM ENDB-WATER ENDC-PUMP FRAME

D-PUMP CYLINDERE-SUCTION VALVESF-DISCHARGE VALVES

admission of steam is controlled by a slide valve, opening ports to the cylinder for steam to flow through.

The valve is controlled in a different way in the simplex pump than in the duplex pump. In the duplex pump the slide valve for one cylinder is controlled by the piston rod of the other cylinder. Thus as one piston nears the end of its stroke it causes the slide valve of the other cylinder to slide on its seat, opening ports, admitting steam, thus starting the other piston on its stroke.

For best results, in the simplex pump an auxiliary valve is controlled by the piston rod, which admits steam to one side of an auxiliary piston in the steam chest, which in moving in a cylinder, slides the main slide valve in the proper direction to admit steam to the cylinder, starting the piston on a new stroke.

Starting Reciprocating Pumps-In starting a reciprocating pump the following operations should be followed.

1. Make sure pump is clear and free to operate.

  2. Open proper discharge valve.3. Open proper suction valve.4. Open cylinder and steam chest drains.5. Open exhaust valve.6. Crack steam valve, starting pump.7. Close drains.8. Regulate speed.9. Lubricate.

CENTRIFUGAL PUMPS

If a pail partly filled with water is whirled in a circle, the water will stay in the bottom of the pail, in fact, the water will tend to force itself through the bottom of the pail. This action is due to what is known as centrifugal force. Centrifugal force is a force set up by whirling a body in a circle, which tends to cause that body to fly off at a tangent to the circle.

Mud guards are used around wheels because of the mud and water being thrown off the wheels due to centrifugal force.

A centrifugal pump is a pump that causes the flow of a liquid due to this force. It consists essentially of a motor or impeller which is

 

92  rotated at high speed inside a casing. The water enters the center of the impeller, is rotated rapidly, and is thrown from the ends of the impeller blades at high speed due to centrifugal force. This high velocity, imparted to the liquid by the impeller, can not be used for pumping, but must be changed into pressure. This is done in one of two ways. In one case, the shape of the casing is such that, as the casing nears the discharge opening, its area becomes larger and larger, or the casing cross section has a spiral shape. This shape of the casing is called volute. This volute-shaped casing causes the liquid to slow down and build up static pressure. Thus when the liquid leaves the casing, it leaves under a pressure.

In the other case, when the water is thrown from the blades of the impeller at high speed, it is caused to flow through vanes, which are attached to rings called diffusion rings. It also changes the high velocity into pressure.

Centrifugal pumps are usually divided into two classes according to the manner in which the velocity of the water is changed into pressure. If the volute shape of the casing is used, the pump is termed a volute centrifugal pump; whereas, if diffusion rings, containing diffusion vanes are used, the pump is termed a turbine centrifugal pump.

VOLUTE CENTRIFIGAL PUMP

If there is only one impeller contained in the casing, the pump is known as a single-stage pump. A single-stage centrifugal pump of the volute type class is shown in the accompanying drawing.

  The impeller turns in the direction of the arrow. The liquid entering the center of the rotating impeller is thrown outwards by centrifugal force at high velocity. The walls of the casing form a spiral-shaped chamber which increases in area as the discharge outlet is approached. This spiral shape of the casing is called the volute. The purpose of the volute is to collect the liquid which is thrown out by the impeller blades at high velocity and, by the increase in area, reduce the velocity and increase the pressure.

In some installations, where the discharge pressure obtained is not sufficient, there may be more than one impeller contained in a casing. The first impeller discharges directly into the center of the second impeller, etc., each succeeding impeller building up more pressure. These are known as multi-stage centrifugal pumps and consist of more than one impeller connected in series. This type is used for boiler feed pumps.

In other installations, where a tremendous

CENTRIFUGAL MAIN CIRCULATING PUMP

The above picture shows centrifugal type circulating pump (I), driven by a single cylinder reciprocating steam engine (2). The pump takes its suction from the sea through the main injection valve (4), and discharges into the cooling water side of the main condenser (3).

The steam control valve to the engine is equipped with an extension rod to the topside, as is the main injection valve. This permits stopping the main circulator and closing the main injection from outside the engine room in an emergency.

The engine cylinder drain valves are also visible. (5) is the observation tank for examining the returning condensate from the fuel oil heaters for presence of fuel oil. (6) is the feed and filter tank.

 

93  volume of liquid is required, such as some fire pumps, in order to reduce the size of the pump, more than one impeller is inclosed in a casing, all of them taking suction from the same suction line, and all of them discharging into a common discharge line. These are pumps in parallel, and with little effect on the pressure, are capable of discharging large quantities of liquid.

By themselves, centrifugal pumps of both classes have the disadvantage of being unable to displace air and reduce the pressure in the suction line below that of the atmosphere. They are therefore unable to lift water from a level below the pump suction. They are the only type of pump which are not positive displacement pumps.

ROTARY PUMPS

Where a service requires the lifting of small volumes of liquids, and the delivering of it with an even flow against an appreciable head pressure, rotary pumps of the positive displacement type have, to a large extent, replaced reciprocating pumps. Their pumping action is accomplished by rotating gears, screws, or tumblers inside a casing.

There are many types and designs of rotary pumps, the most common being the gear and screw pump. A gear pump is shown here.

GEAR PUMP

Gear Type-The gear pump usually consists of two gears, meshing together, caused to rotate within a close fitting casing. One of the gears is turned by an engine or motor, and in turn,

rotates the second gear. The liquid enters at the bottom of the pump at (A), is carried between the gear teeth of each gear around the inside of the casing, and when the teeth mesh the liquid is displaced and forced out through a discharge opening, (B).

  Another form of this pump uses two rotors with lobes on each rotor. The two rotors mesh together. The lobes act in the same way as the gear teeth, carrying the liquid around the inside of the casing, displacing the liquid when a lobe on one rotor meshes between two of the lobes of the other rotor. This type of rotary pump must have meshing gears on the same shafts, or timing chains to keep the lobes of both rotors spaced so that they mesh at the

TWO LOBE CYCLOIDAL PUMP

center of the pump. In the drawing of the lobe type pump, known as a cycloidal pump, the liquid enters at the bottom and is discharged at the top as indicated by the arrows.

These pumps may contain rotors of two or three lobes, and these lobes engage with a rolling motion.

THREE LOBE CYCLOIDAL PUMP

Screw Type-Screw pumps are rotary pumps using rotating screws to create the pumping effect. They consist of two shafts, each shaft carrying a left and right-hand screw. One shaft is driven by the power unit, and imparts its motion to the other shaft through a set of gears. These gears also act as timing gears.

The screws must be contained in a close fitting casing. The liquid enters the pump at the bottom, and floods the casing. The ends of the threads cut into the liquid, trapping quantities

 

94  of it into the spaces between the threads. The meshing of the threads prevents the escape of liquid from these spaces.

The threads, being right and left-handed, move the liquid from either end towards the center of the shafts, where it is discharged from the outlet to the line.

The accompanying sketch shows the rotating parts of the screw pump enclosed in the tight fitting casing. It shows the liquid inlet at the bottom, and the discharge outlet at the top. The

SCREW PUMP

arrows showing the flow of the liquid through the pump denote that the liquid enters at the ends of the threads and is discharged at the center.

This is an excellent type of pump for services such as the fuel oil service pump.

Rotary pumps of the gear and screw types should not be used for pumping liquids containing abrasives such as sand, grit, etc., because any wear of the pump parts will materially reduce the efficiency of the pumps.

AIR PUMPS AND VACUUM

A certain amount of air and non-condensable vapor unavoidably enters the condenser. As the condenser operates at a pressure below atmospheric pressure, this air is also at a pressure below the atmosphere; and in order to remove it, some apparatus must be furnished that will compress this air to above atmospheric pressure.

There are two mechanisms in general use for removing this air; one called an air pump and the other an air ejector.

Air pumps are divided into two general classes: wet and dry. A wet air pump handles both air and condensate. A dry air pump handles air only, with a separate pump handling condensate.

Dependent Air Pump-In marine practice, the wet air pump is more commonly used than the dry. The common method of driving the pump is to attach it to the L.P. crosshead of the main engine, of the reciprocating type. The Edwards

  air pump is in general use and a sketch of this type is shown. In this particular pump all valves are dispensed with, except those for the discharge. The air and water, or condensate, which collects in the base of the pump is displaced and forced into the pump cylinder by the descending plunger. It is then caught above the plunger when it makes an up-stroke and is discharged through the discharge valves.

EDWARDS DEPENDENT AIR AND CONDENSATE PUMP WITH ATTACHED BILGE PUMPS

A-AIR PUMP BODYB-AIR PUMP LINERC-AIR PUMP BUCKETD-AIR PUMP RODE-CROSSHEAD

F-INLET CONNECTION FROM MAIN CONDENSERG-AIR PUMP SUCTION PORTSH-DISCHARGE VALVESI-STUFFING BOXESJ-BILGE PUMP CYLINDER

Independent Air Pump-This type, formerly used with turbine installations, has largely been replaced with air ejectors and condensate pumps as a means of removing air and condensate from main condensers. Independent air pumps consist of two pumps, one for removing the condensate and the other for air. In the cross-section view the wet air pump removes the condensate from the condenser and discharges it out of the top of the pump to the feed and filter tank as shown by the arrows. The dry air pump takes its suction higher up on the main condenser thereby taking only air. The air is discharged

 

95 

INDEPENDENT AIR AND CONDENSATE PUMP   out of the top of the pump to the engine room. To provide a liquid seal for the dry air pump plunger, a small amount of water is injected at the bottom end of the pump.

Independent air pumps are driven by their own steam cylinders being entirely independent of the main engine.

AIR EJECTOR

The steam jet air ejector, because of its small space, weight, and economy of operation and maintenance, has replaced the reciprocating air pump on practically all turbine-driven vessels, and in some cases is used with reciprocating engine installations.

An ejector consists essentially of a steam nozzle discharging a jet of steam at high velocity across a suction chamber. The air and non-condensable vapors enter the suction chamber, are entrained by the jet of steam, and discharged into a compression tube where the velocity is reduced and the pressure increased before discharging.

This is known as a single-stage air ejector, but, since it is necessary to discharge the air into the atmosphere, the required discharge

  TWO STAGE AIR EJECTOR  

96  pressure cannot be economically obtained by the use of just one set of steam nozzles.

To attain higher vacuums, and for increased economy, air ejectors are usually built with two or more jets in series. They are known as multi-stage ejectors.

A two-stage air ejector is shown in the accompanying sketch.

The first-stage nozzles (A) at the top of the sketch take their suction from the main con-) denser and discharge into a chamber known as an intercondenser (B) where a portion of the steam vapors are condensed. The second-stage nozzles (C) pull the remaining air and steam vapors out of the intercondenser and discharge

  them into the after condenser (D) where all vapors are condensed. The cooling water for the inter and aftercondensers is fresh water condensate from the main condenser condensate pump. The inter and aftercondensers may be of the jet or surface type. All of the condensate returns to the feed system.

When air ejectors are used, the condensate formed in the main condenser is removed by a separate pump which may be either of the reciprocating or centrifugal type. The pump discharges the condensate through the inter and aftercondenser to the open type deaerating feedwater heater. (See steam and water cycle on page 86.)

LIQUID END DOUBLE ACTING PUMP  

  The arrows indicate the flow of liquid as the plunger is moved forward. A partial vacuum is created behind the plunger. Atmospheric pressure is now sufficient to force the liquid through the suction valves, filling the spaces behind the plunger. At the same time liquid is pushed through the discharge valves by the plunger. This discharge pressure aids the springs in holding the suction valves closed and forces the discharge valve open. By following the arrows the reader can see that on the return stroke the same cycle of events takes place. The hand shown on the piston rod is representative of the steam cylinder which transmits power through the piston rod to the liquid plunger. Each stroke of a double acting pump is a power stroke and the result is a steady, unbroken flow.  

 

97 

REMEMBER-BILGE WATER OIL SLICK CAN BE TRAILED

PUMPING SYSTEMS  

For the ship's safety and operation the following pumping systems are needed. The pumps are usually located in the engine room.

Bilge System-Into the engine room bilges flows the cooling water discharging from the main bearings, guides and thrust bearing. Sea water also enters the bilge from the stern gland.

To remove this water and discharge it overboard, a pump known as the bilge pump is used. It is an independent pump usually of the steam reciprocating type. The pump takes its suction through a pipe line from wells in the forward and after ends of the engine room bilge. The fireroom bilge is likewise equipped. Around the open end of the suctions is placed a strainer in the form of a perforated steel plate, to prevent rags, etc., from entering the pipe. These are sometimes known as rose boxes. If the bilge pump refuses to remove the water, look at the rose boxes to see if they are not plugged.

Many reciprocating main engines have what are known as bilge rams on the side of the dependent air pump. These act as bilge pumps when the main engine is operating, the regular bilge pump being kept for port use.

Do not pump bilge water overboard except at authorized times. You may leave a trail of oil behind your ship that the enemy can follow.

Ballast System-When a ship is running without cargo it rides high in the water. Should heavy seas blow up, it will be necessary to bring the ship down further in the water in order to handle it. This is done by pumping sea water through pipe lines into the empty fuel oil storage tanks in the double bottoms. This is known as ballast. The pump for this purpose is known

  as the ballast pump. On the suction and discharge sides of the pump are valve manifolds, which are simply several valves in one body. Each valve wheel has a name plate, upon which is stamped the particular tank that the pump is sucking from and discharging into. By opening and closing the different valves, ballast may be pumped from any one tank to any other.

Valve manifolds are also used with other pumps, such as the fuel oil transfer pump.

Sanitary System-To supply sea water for the various toilets aboard ship a steam pump known as the sanitary pump is provided. It takes its suction directly from the sea and is usually controlled by an automatic pressure regulator so that the pressure in the sanitary line remains constant no matter how much water is being used.

Do not flush toilets in daytime. You may give away the location of your ship to the enemy.

The cooling water for the refrigerating machine is quite often taken from this line.

Fresh Water System-For washing purposes, fresh water is pumped from the fresh water storage tanks through pipe lines to the lavatories in the crew's quarters and to the showers in the washrooms.

Water for drinking and cooking is pumped from the domestic tanks to the galley and drinking fountains. In some ships a gravity tank is provided on the boat deck, in which case the drinking water would be pumped from the domestic tanks to the gravity tank, from where it

 

98  would run by gravity to the galley and fountains.

Fire Main-For fire fighting purposes a special pump known as the fire pump is provided. It takes its suction from the sea and discharges it through the fire line the length of the ship. Convenient

  fire hose connections are located along the fire line to permit a fire at any point in the ship being reached by the fire hose.

Fire pumps must be ready for instant service and the method of starting up should be thoroughly understood by the engine room crew.

 

99  ELECTRICITY   For many years American ships have been equipped with electric lights. Prior to that, oil lamps were used for running lights and illumination in crew's quarters, engine and firerooms. Electricity for these lights and to operate electric motors is produced in an electric generator which is driven by a steam engine, either reciprocating or turbine.

ELECTRO-MAGNET

The electricity produced flows to all parts of the ship requiring light and power, through copper cables in much the same manner as water flows through pipes. There is nothing complicated about the principle of electricity if it is compared with a liquid. If water is pumped through a pipe line under pressure, the amount of pressure in lbs. per sq. in. is determined by looking at the pressure gage. The pressure of electricity is known as volts and is determined by looking at the voltmeter on the switchboard.

ARMATURE

The rate of flow of a liquid may be spoken of in gallons per minute. The rate of flow of electricity is known as amperes and is determined by looking at the ammeter on the switchboard.

To find the amount of work being done by an electric current, multiply the volts by the amperes. This results in watts. A thousand watts is a kilowatt, known as K.W. On the name plate of generators is stamped the maximum K.W. capacity of the generator. This should not be exceeded.

Electricity, if allowed to flow through the human body, can easily be fatal even though the voltage is low. The amount of amperes has the greatest effect on the body. When working around electricity take every safety precaution.

 

GENERATORSElectricity is generated by the cutting of magnetic lines of force by wires in a closed circuit. The magnetic lines of force are created by field poles, which are really

electro-magnets. An electro-magnet consists of an iron core with a coil of wire around it, electricity passing through the wires of the coil.

FIELD POLES

The wires which cut the magnetic lines of force are wound on the armature of the generator. The armature is connected to the engine or turbine and is rotated between the field poles, which are stationary. As the electricity is generated in the wires of the rotating element, it must be taken from it. To do this, carbon brushes bear against a commutator to which the armature windings are connected. The commutator consists of copper segments, each one

GENERATOR

insulated from the next one, and also insulated from the armature shaft. Each coil has one end connected to one segment and the other end to a segment on the opposite side of the commutator. The brushes which bear against the commutator are arranged so that one of them will connect one end of the coil to the outside circuit, thus making a complete circuit. The brushes connect

 

100 

GENERATORS AS INSTALLED ON LIBERTY SHIP

The above picture shows three 110 volt, 20 K. W., D. C. generators (I), driven by single cylinder reciprocating steam engines (2). The switchboard is visible aft of the generators with cables leading up from it to the various parts of the ship.

It is most important that the oiler be thoroughly familiar with the lubrication of the steam engine. The lubrication of the main bearings, crankpin bearings, crosshead bearings, guides, eccentric and valve gear bearings is automatic, being supplied by an oil pump located in the

oil sump in the base of the engine frame. The pump is operated from the crosshead by a rod or chain drive from the crankshaft. The oil discharges upward through a pipe line to a gravity sight feed oil box seen on the side of the engine just below the cylinder. From here the oil flows by gravity through needle type regulating valves to each bearing. A glass window in the side of the box enables the oiler to see whether or not oil is flowing to each bearing. The level of the lubricating oil in the sump is determined by looking at the gage glass in the side of the engine base. Oil should be added from time to time to keep the proper level.

The generator shaft bearing may be either of the ring oiled type or a sealed ball bearing requiring little attention except to feel it each round.

The piston rod and valve stem are swabbed with cylinder oil each round. The packing should be kept from leaking as the escaping steam tends to travel down the valve stem and piston rod into the crankcase where it mixes with the lubricating oil, forming an emulsion. This emulsion is not a proper lubricant.

As generators must operate at a constant speed no matter what the load, a speed governor, usually of the wheel or shaft type, is provided on the engine. This type governor regulates the length of the valve travel thereby controlling the amount of steam entering the cylinder.

In the picture may also be seen the steam and exhaust valves, the larger valve wheel being the steam. Cylinder relief valves are also visible. The engine balance wheels are covered with a guard to prevent injury to crew members in event of being thrown against them.

The generator commutator must be kept dry and clean. Lubricating oil should never be used on it. To clean the commutator the generator is revolved slowly with the brushes removed, holding a clean dry rag or very fine grade of sandpaper on it.

When checking a generator, as when checking any other auxiliary machinery, any unusual noise or sound should be noted and reported at once to the engineer.

 

101  to a main switch on the switchboard, from which electrical circuits lead to the lights and motors on the ship.

A complete circuit is necessary for electrical current to flow. Therefore when no electricity is being used, there is no flow of electrical current. When lights are on or motors started, the circuit is completed and electricity flows through the circuit.

As a flow of electricity is necessary for an electromagnet to work, and as field poles are electro-magnets, electricity from the armature is led to the field coils. This creates magnetic lines of force between two poles.

When starting up a generator, the necessary magnetism is provided by that held by the iron cores of the field poles. This magnetism is known as residual magnetism.

ENGINE GENERATOR

From the main switch, the lines carry the electricity to a circuit breaker. The circuit breaker is a device which automatically opens the whole circuit in case of an overload. Thus the circuit breaker is a protective device for preventing the overloading of the generator. An overloaded generator will heat up, causing burned insulation and short circuits.

Lines from the circuit breaker connect to switches that control the individual lighting and power circuits of the ship. These lines are heavy copper bars and are known as busses or bus bars. The individual circuit switches are equipped with fuses, which melt if too much load is applied to that circuit. Thus the fuses are a protective device for preventing too high a load on any one circuit.

If the circuit breaker opens, some of the load (lights and motors) must be reduced, and the circuit breaker may then be closed by moving the handle back to closed position. If a fuse melts, or blows out, as it is called, a new fuse is placed in position after some lights or motors

  are shut off. In some types of fuses the fuse may be taken apart and a new fuse link put in place of the melted one.

The switchboard also has a voltmeter and an ammeter installed on it. The voltmeter is to show the voltage of electricity generated. In marine practice this is kept at around 120 volts. The voltage is controlled by the number of magnetic lines of force cut by the armature windings. This in turn depends upon the speed of the armature, and the current flowing through the field coils. As the speed of the armature is kept constant by the governor of the engine or turbine, the voltage must be controlled by the amount of current flowing in the field coils.

In practice the voltage is controlled by a rheostat located on the switchboard. The control wheel is turned one way to increase the voltage and the other way to decrease the voltage. The rheostat controls the amount of current flowing through the field coils, thus controlling the voltage.

The ammeter shows the amount of current that is being used by the lights and motors of the ship. The current is measured in amperes, the amount depending upon the size and number of lights and motors in use.

PROPER METHOD OF CHANGING OVER GENERATORS

Generators are ordinarily started and stopped by the engineer but it is well for the oiler and watertender to understand the procedure. They may be called upon to assist at any time.

When a ship has two generators, one is in service while the other stands by. At regular intervals, probably once a week, the stand-by is started up and the in-service one shut down for a week. This is known as changing over the generators.

To start a generator the following procedure should be followed:

1. Make sure circuit breaker and main switch on the switchboard are in the open position.

2. Make sure generator is clear by revolving it one revolution by hand.

3. Check commutator to make sure brushes are in place.

4. Check lubricating oil level in engine.

5. Open cylinder and steam chest drains.

6. Open exhaust valve.

7. Crack steam valve, allowing engine to run slowly until warmed up.

 

102  8. Check lubrication.

9. When engine is warmed sufficiently, bring up to full speed.

10. Close drains.

11. Adjust rheostat to bring voltage up to a few volts above the bus voltage.

12. Throw in circuit breaker.

13. Throw in main switch.

  The following procedure should be followed when shutting down a generator:

1. Take most of the load off the machine.

2. Trip the circuit breaker.

3. Pull out the main switch.

4. Close steam valve to engine.

5. When machine stops close exhaust.

6. Open drains.

 

103  DECK MACHINERY   To lift cargo aboard and ashore, pull in the mooring lines and raise the ship's anchors, machinery is required. As it is usually located on the open deck, it is known as deck machinery. These include cargo winches, capstans and anchor windlass, which may be driven by steam engines or electric motors.

STEAM CARGO WINCH

A-DRUMB-NIGGER HEADC-DIFFERENTIAL VALVED-STEAM CHEST

E-CYLINDERF-DIFFERENTIAL VALVE CONTROL LEVERG-CROSSHEAD

CARGO WINCH

Steam winches consist of two steam engines connected to the same crankshaft. The two cranks are at 90 degrees so that the winch will always start no matter what position it is. The crankshaft is connected to a drum by means of reduction gearing. Wire is wound on the drum, which turns at a much slower speed than the crankshaft. The other end of the wire is carried up a cargo boom and is used to transfer cargo from the hold to the dock or vice-versa. A brake is usually fitted to the drum of the winch, controlled by a foot lever so that the winch may be held with a load on it when the steam is shut off. Steam to cargo winches is controlled by an operating lever which moves a differential valve, working in the same manner as described on reversing engines. The winch is thus reversible, the differential valve controlling the speed and direction of rotation of the drum.

  A warping winch is supplied on the after deck for handling mooring lines. The winch is built on the same plan as the cargo winches but two nigger heads or gypsies are secured on the same shaft as the drum and geared down from the speed of the crankshaft. The cargo winches usually have one gypsy on the outboard side. The nigger heads are used to wind the mooring lines around so that as the heads are rotated the lines are drawn in.

The warping winch is usually made reversible, operated by a lever and differential valve. In some types a double reduction of speed is accomplished by another set of gears which may be brought into use by moving a lever. This reduces the speed of the nigger heads.

Electric winches are driven by an electric motor. The speed of the motor is reduced by gearing and the drum turns at a slower speed. The speed of the motor is controlled by a resistance box and handle.

ANCHOR WINDLASS

A-SPEED REDUCING GEARB-WILDCATC-BRAKED-BEARINGS

E-NIGGER HEADF-CYLINDERG-STEAM CHESTH-DIFFERENTIAL VALVE

ANCHOR WINDLASS

On the forecastle head an anchor windlass is situated for the purpose of hoisting anchors and handling mooring lines. The anchor windlass consists of two reciprocating engines connected

 

104 

SCREW TYPE STEERING ENGINE   to the same crankshaft, as in cargo winches. The rotation of the crankshaft is communicated by gears to two wildcats into which the anchor chain fits. The dogs on the wildcats keep the chain from slipping. Each wildcat is held on its shaft by a clutch which may be slacked off entirely or tightened up so that either or both chains and anchors may be hoisted.

The wildcats are run much slower than the crankshaft due to the number of speed reducing gears used between the crankshaft and the wildcat shaft. Each wildcat is supplied with a brake, actuated by a hand wheel, so that when it is not secured to the shaft, the brake may be used to prevent its turning.

Nigger heads are secured to the ends of a higher speed shaft, thus turning faster than the wildcats. The nigger heads run whenever the windlass is turned over. They are used for handling mooring lines.

  The windlass is the most powerful of the deck machines because not only may it be required to lift both anchors at the same time, but when the vessel is riding at anchor there are times when the full strain of the anchors and chains pull directly on the windlass. Being in the extreme bow of the vessel, it sometimes takes the brunt of the seas coming over in rough weather.

LUBRICATION

The various bearings of the winch and windlass steam engines are oiled by hand, the oil being squirted into brass oil cups filled with horse hair. The piston rods and valve stems have to be swabbed the same as any steam engine.

The winch and windlass bearings are generally lubricated by grease from grease cups on each bearing.

 

105  STEERING ENGINES   All vessels need a form of control with which to steer the ship. This consists of a rudder at the stern of the vessel, the rudder being moved by some mechanical device.

At present the two devices generally used are the steam engine, and the hydraulic ram. The steam engine usually consists of two cylinders with cranks 90 degrees apart, so that the engine will start from any position when steam is

  admitted to the cylinders. The steam to the valve chests is controlled by a differential valve, as explained under reversing engines, to allow the steering engine to run in either direction. The crankshaft of the engine is attached by gears, quadrants or screws to the rudder post so that when the engine turns, the rudder is moved to turn the heading of the ship to port or starboard.

QUADRANT TYPE STEERING ENGINE

A-TELEMOTORB-DIFFERENTIAL VALVEC-FOLLOW-UP GEAR

D-QUADRANTE-SPRINGF-TILLER ARM

G-RUDDER POSTH-HAND BRAKE

In this illustration pinion and quadrant gears are painted to afford photographic contrast.

 

106  The differential valve is controlled from the bridge of the ship by the steering wheel. This is usually done in one of two ways; by gears and shafting reaching from the bridge to the steering engine or by telemotor.

A sketch of a screw-type steering engine is given on page 104.

SCREW-TYPE STEERING ENGINE

The steam is admitted to the cylinder through the differential valve (E) which is controlled by steering wheel shaft (G). As the crankshaft (F) revolves, the worm also revolves, turning the large worm gear on the right- and left-hand screw shaft (A). The traveling nuts (B) move together or apart, depending on which way the engine is turning, and through connecting rods turn the rudder post (C).

In order for the steering engine to stop and hold the rudder when the steering wheel is stopped, the follow-up gear (D) is provided. This pushes the differential valve to the closed position, stopping the engine as soon as the man at the steering wheel stops turning it.

QUADRANT TYPE STEERING ENGINE

A very popular type on medium sized cargo vessels, consisting of a vertical two-cylinder steam engine with cranks set at 90° apart to permit starting of the engine at any point. A worm on the crankshaft meshes with a worm wheel upon a vertical shaft, upon which is a gear that meshes with the quadrant. The quadrant is connected through coil springs to the tiller arm. The springs take up some of the shock of the seas pounding against the rudder. As the engine operates in one direction or the other, the quadrant swings in an arc turning the rudder post and rudder.

The engine bearings are hand-oiled, having wick-feed gravity boxes.

The engine has a differential valve and follow-up gear the same as the screw type.

To lock the rudder in the event of one or more of the gears carrying away, a hand brake with control wheel is provided.

Steam steering engines usually exhaust direct to the main condenser instead of into the auxiliary exhaust line. In this manner there is no fluctuating back pressure for the engine to work against.

ELECTRO-HYDRAULIC TYPE STEERING ENGINE

In fast, modern ships this type is

  predominant. A typical installation is shown in the illustration. It consists of an electric motor driven reversible pump which forces light oil into either end of a hydraulic ram. As the

ram moves, it swings the tiller arm and rudder. By reversing the direction of the pump, the movement of the ram is reversed and so the rudder.

ELECTRO-HYDRAULIC STEERING GEAR

TELEMOTOR

The sketch shows the principle of the hydraulic telemotor. It consists of two cylinders connected by pipes. Each cylinder contains a close-fitting piston. The cylinders and piping are filled with a mixture of glycerine and water, or with a light oil. When one piston is moved it moves the other piston through the medium of the oil or glycerine mixture.

TELEMOTOR

One piston is attached to the steering wheel on the bridge, the other being attached to the differential valve by links, and lever arrangement. Thus, as the wheel on the bridge is turned, the piston in the steering engine room moves the differential valve, admitting steam to the engine.

 

107  PIPING SYSTEMS   The various pipe lines are the blood vessels of the power plant, for through them flow the vapors and liquids that are the life blood of the ship.

MATERIALS

Main Steam Line-The main steam line that conveys the steam from the boilers to the main engine is made of copper or steel, depending on the pressure and temperature to be carried.

The piping is made up in sections for convenient handling, being joined usually by bolted flanges, although with modern methods a certain proportion of the joints are fusion welded.

  Auxiliary Steam and Exhaust Lines are also made of copper or steel and joined together in the same manner, excepting some of the smaller sized piping, which may be joined by threaded connections.

Allowances for expansion and contraction of the piping due to temperature changes must be made, either by a slip joint or an expansion loop. Piping must also be supported by hangers at sufficient points to prevent strain on the piping.

Around the outside of all steam piping is placed asbestos insulation, usually covered with sewed canvas, to hold the heat inside the pipe line.

PIPE LINE IDENTIFICATION MARKINGS

 

108

   

109

  Fresh Water Piping-Piping carrying fresh water should preferably be made of copper or brass to resist corrosion, although galvanized steel pipe is sometimes used.

Salt Water Service-For salt water service brass or copper piping should always be used, as corrosion is severe on steel piping.

Cold water pipes are usually covered with from 1/2 inch to 1 inch of cattle hair felt to prevent condensation forming on the outside of the pipe.

Fuel Oil and Refrigeration-For fuel oil and refrigeration, steel pipe is used.

IDENTIFICATION MARKINGS

In order that the various pipe lines carrying

  different substances may be readily identified throughout the ship, a system of markings is used at intervals along the pipe lines. Some shipping companies use their own systems. The standard marking system used on most ships today is listed.

PIPE FITTINGS

Pipe is made in three wall thicknesses-standard, extra heavy, and double extra heavy. When a pipe line is installed, the straight sections of pipe must be joined together. One method is with threaded fittings of which several types are shown. The type to use depends on the combination of piping and angles to be joined. The material of the fittings should in most cases be the same as the pipe.

 

110

 

STANDARD PIPE FITTINGS  

Another method of connecting sections of pipe is with flanged joints, several different types of which are shown.

A gasket is placed between the faces of the flanges, after which the flanges are pulled tightly together with bolts.

PIPE FLANGES

STEAM TRAP

When steam travels through pipe lines for any distance, condensation will occur. When steam is admitted to a cold line, condensation is great. To automatically remove the condensate, steam traps are used.

There are several types of traps, the cross-section sketch being a trap of the float type. From a low point in the steam line a small pipe line connects to the inlet opening (A) of the trap. The condensate and steam under pressure enter the chamber. As the condensate gradually fills the chamber, the copper float (B) rises and through the float lever opens the valve. The pressure forces the condensate through the valve opening and out the discharge (C) to the hotwell. As

the condensate leaves, the float drops, closing the valve before the condensate level drops below it, preventing the steam from leaving.

Steam traps are also used in the drains from

  feedwater heaters, fuel oil heaters and in connection with any apparatus where it is desired to automatically remove condensate without wasting steam.

STEAM TRAP

VALVES

Valves are used to control the flow of fluids. There are many types of valves, but they are usually one of the following: globe, angle, gate, check, or cock. The working pressure and the kind of service determines the material, weight, size, and design of the valve to be used.

The globe valve is used to control passage of steam, water, etc. It is made up of a body, bonnet, seat and valve disc, stem, stuffing box and hand wheel. The seat may be either flat or beveled; if beveled, usually to 45°. The valve disc is fastened to the stem, which is threaded and turns in similar threads in the bonnet. The body of the valve is usually of cast steel or

 

111 

U. S. Maritime Service Training Aids Unit Chart

TYPES OF VALVES

The arrows indicate the direction of flow in the more common types of valves used in ship's piping. The check valves and relief valve shown are classified as automatic valves. The globe, angle and "Y" type valves are used where it is desirable to adjust the rate of flow. The gate valve should be either completely open or completely closed, otherwise chattering will result in excessive wear. The gate valve is used where a minimum amount of turbulence is desired since it offers very little resistance to flow. The gate valve shown has a rising stem which indicates at a glance whether the valve is open or closed.  

brass. The valve and seat are usually of composition, and if the valve is very large it has a renewable seat, usually screwed into the body casting. On most valves, two inches and over, the threaded part of the bonnet through which the stem passes will be outside or in the form of a yoke. This keeps the threads away from the action of the steam. The yoke is part of the bonnet, the stuffing box being beneath the yoke.

The angle valve uses the same type of seat and valve disc as the globe valve, the difference being that it is used to connect pipes that meet at a right angle. The construction and materials used in the angle valve are the same as those in the globe valve, the only difference being the design. One advantage of the angle valve over the globe is that it offers less resistance to flow.

  Check valves are valves that permit fluids to pass through them in one direction only, and are designed to close automatically whenever the flow of the fluid is reversed. They are made in different forms, as, vertical, horizontal and angle check valves. They are also made in

swing check valves, where the valve disc is hinged and closes the seat while still at a slight angle, and globe check valves, where a globe type valve disc is provided with guides above and below the seat to keep the disc from tilting sidewise.

Adjustable check valves are of the same type generally as the globe check valve, but the. amount that the valve can lift is governed by a stem and hand wheel. These are used frequently as the feed check valve on boilers.

A cock is a valve which is capable of being

 

112 

VALVE PARTS   quickly opened or closed. Probably the most familiar type is the pet-cock.

Blowoff valves on boilers are usually of the straightway type such as gate or "Y" valves, or of special design. Angle valves are also used for this purpose. These types of valves do not trap sediment.

Gate valves are made either as single gate valves which receive pressure on one side only, or as double gate valves, which may receive pressure on either side. Some forms of double gate valves close off the fluid passage with a solid wedge, others with a box wedge, and others with sectional gates having either parallel or wedge-shaped seats.

Gate valves are advantageous where little resistance to the flow of the liquid is desired, as they leave an unobstructed passage when fully

  open. Therefore, they are largely used on water and exhaust steam connections. When throttled, that is, when only partly open, they are hard to regulate and often chatter. In all gate valves, the discs rise into the upper part of the bonnet and leave a straight passage for the flow.

One type of gate valve has the gate threaded, and the gate screws up the stem, the hand wheel remaining at the same distance from the bonnet whether the valve is open or closed. On larger gate valves a yoke is used, the stem being threaded and fitted to threads on the hand wheel. When open, the stem extends through the wheel. This type is advantageous as the threads may be properly lubricated and also do not come in contact with the steam. Gate valves should be installed in a vertical position with the hand wheel on top, if possible.

 

113  REFRIGERATION   On American ships fresh meat, vegetables and fruits are an everyday fare for the crew even though the ship be traveling a long distance in warm climate. This is made possible by mechanical refrigeration which keeps the meat frozen in the meat box until just before it is to be cooked. The fruits and vegetables are kept in a separate box where the temperature is kept above freezing but cold enough to preserve them until used.

Mechanical refrigeration depends upon heat for operation. A typical modern refrigeration system is shown in the sketch.

In the upper part of the meat box is a steel pipe coil into which liquid, either ammonia, freon, or CO, is allowed to expand into a gas. When this occurs, heat from the surrounding air in the box is absorbed by the gas in the coil. The heat travels with the gas through the pipe line out of the box to the suction side of the compressor. This leaves the box cold. The arrows in the box indicate how the cold air around the coil settles down to the bottom of the box and the warmer air around the meat rises up to be cooled.

This particular system is for freon so that type will be discussed. Upon returning to the compressor, the freon gas is compressed by a piston in a cylinder which is driven by either a steam engine or electric motor. From here the compressed gas travels to the condenser, where the heat is taken out of the gas by sea water on the same principle as a steam condenser. With the heat removed, the gas returns to a liquid in which form it drops down to the receiver, which is a tank for storage. The liquid freon passes from the receiver up the pipe line to the expansion valve, through which it passes to become once again a gas in the box coil. By regulating the expansion valve, the amount of freon entering the coil is determined, which in turn regulates the temperature of the meat box.

The side walls, roof and floor of the box are insulated to keep the outside heat out and the inside cold in.

Two pressure gages are provided just above the compressor. One shows the pressure of the freon gas returning to the compressor usually around 5 to 10 pounds. The other shows

  the discharge pressure of the gas leaving the compressor usually around 90 pounds. These pressures vary according to the temperature of the cooling water flowing through the condenser. The hotter the cooling water, the higher the discharge pressure and vice-versa.

FREON REFRIGERATION SYSTEM

When more freon is needed in the system it is put in from the charging cylinder shown.

Previously, ammonia was widely used as the liquid for refrigeration aboard ship, but today practically all new ships are equipped with freon systems. Freon is an odorless, harmless substance, except to the eyes upon close contact. Ammonia is highly injurious to humans, if trapped in a confined space.

When checking the refrigerating system the oiler should note the suction and discharge

 

114

  MECHANICAL REFRIGERATION   pressures. An excessively high discharge pressure is a good indication that the cooling water to the condenser has stopped flowing. This can be serious if the pressure should continue to build up until an explosion results. Relief valves are installed as a safeguard against excess   pressure, but should not be depended upon. The oiler should definitely determine that the cooling water is flowing properly at each visit.

The oiler should check the lubrication of the compressor, and listen for any unusual sounds. Notify the engineer of anything unusual.

 

115  SAFETY PRECAUTIONS   Working around marine power plants, members of the crew must observe a few safety precautions if they are to escape injury.

The following rules should be thoroughly memorized and lived up to at all times:

Keep a close watch on the water level in the boilers.

Always use a torch when lighting an oil burner.

When blowing down the gage glass, look away from the glass until gage glass drain valve is closed. The glass may break and pieces fly in your eyes.

In passing up and down ladders and along gratings, keep one hand on guard rail at all times. Do not try to carry an object requiring both hands. Remember the ship may roll or pitch unexpectedly, causing you to fall to the deck or into the moving engine. The old saying, "one hand for the ship and one for yourself," is a good one.

Always use safety goggles to protect the eyes when working around flying particles, such as chipping paint or using an emery wheel. Remember you can't see with a glass eye.

  When working with tools do not lay them on the gratings. The ship may roll or someone walking along the grating may accidentally kick them off, injuring the man below by striking him on the head. Put tools away when leaving the job.

When oil is spilled, wipe it up immediately. There is nothing that can cause as quick a fall as to step on an oily steel deck plate.

Always keep your arms bare and fingers free of rings when around machinery.

Never enter any kind of an empty tank or boiler until all safety precautions have been taken.

Do not smoke in unauthorized places.

Do not fool or tamper with the machinery.

Notify the engineer of any unusual occurrence, or of anything of which you are in doubt.

Keep your mind on your job.

Know where the emergency escape ladders are. Practice using these emergency ladders frequently.

REMEMBER-CONSTANT VIGILANCE IS THE PRICE OF SAFETY.

 

116  GLOSSARY OF ENGINE ROOM TERMS   Air Cock. A valve placed on the highest point of a boiler. Opened to allow air to escape from boiler when filling or getting up steam. Also opened to allow air to enter boiler when draining.

Air Compressor. A power-driven pump by which air is placed under pressure and usually delivered to a storage tank.

Air Ejector. The unit by which air and uncondensed gases are removed from the condenser, leaving a vacuum. Generally operated by a steam jet. Usually used with power plants having turbine-type engines.

Air Register. A part of an oil burner. By adjusting the air register the amount of air entering the furnace to mix with the oil is controlled.

Appurtenance. (Boiler)-Any equipment used with or attached to a boiler.

Auxiliary. (Auxiliary feed-auxiliary steam lines)-A duplicate, generally of smaller capacity, which can be used as a substitute or used to assist.

Atmosphere Valve. A valve by which the auxiliary exhaust steam can be released to the atmosphere instead of going to the condenser. Used in the event the condenser is inoperative such as when the ship is in drydock.

Alley Well (Tunnel Well). A deep recess at the after end of the shaft tunnel where water trickling through the stern tube collects to be pumped out by the bilge pump.

Back Pressure. The pressure of the auxiliary exhaust steam. Usually about 15 lbs. per square inch.

Auxiliary Steam Stop Valve. A stop valve placed directly on top of each boiler to cut off the flow of steam from that boiler through the auxiliary steam line.

Baffle, Gas Passage. A wall or partition of heat-resisting material between the boiler tubes to conduct the flow of gases along a definite path among the boiler tubes from the furnace to the stack.

Baffle, Water. A steel plate placed in the water and steam drum of boilers to direct and improve water circulation and prevent water splashing over into the dry pipe.

Ballast Pump. A large pump located in the engine room to transfer water ballast either from one tank to another tank, or from one tank overboard. Ballast tanks are usually filled by flooding from the sea.

  Boiler. A pressure vessel used to convert water to steam by applying heat. General types: Fire-tube or Scotch boiler in which water surrounds tubes and firebox. Watertube in which water is carried in tubes which are surrounded by hot gases.

Blowdown. The difference, in lbs. per square inch, between the pressure at which a safety valve opens and the pressure at which the valve reseats, generally expressed as a percentage of the lifting pressure.

Blowdown Ring. A notched ring held in place by a setscrew which extends through the safety valve body. The amount of blowdown can be adjusted by this ring:

turn ring right-raises it and shortens blow-down. turn ring left-lowers it and lengthens blow-down.

Blow Valves. Used to remove sludge, scum, and to reduce salinity.

Bottom blow-A valve used for blowing sludge, mud, scale etc. from the lowest portion of the boiler. Surface blow-(Not required where pressure exceeds 350 lbs. per square inch.) Attached at normal water level of boiler to a pipe or pan which collects scum, grease etc. Used for blowing scum or grease from surface of water.

Blower. A power-driven fan by which air is supplied, under a slight pressure, to a furnace.

Bulkhead. A wall or partition on a ship; may or may not be watertight.

Bulkhead Deck. The deck which connects to any watertight bulkhead forming a watertight compartment.

Brickwork. The brick lining of a furnace made up of firebrick, refractory and insulating material forming walls which add to the efficiency of furnace operation.

Bulkhead Stop Valve. A valve located on the engine room side of the bulkhead separating engine and fireroom. Used to control flow of steam in main line.

Bilge. That portion of a ship's compartment between hull plates and floor plates or between tank tops and floor plates.

Bilge Pump. Any pump having the necessary connections to bilges and water bottoms (suction strainer, pipes, mudboxes, basket strainers, manifold etc.) may be attached directly to air

 

117  pump beam of the main engine or may be an independently powered pump such as the sanitary, ballast, general service or fire pump.

Circulating Pump, Condenser. A pump of large capacity used for the purpose of pumping sea water through the tubes of the condenser, thus cooling the tubes so that the exhaust steam will be condensed. This sudden reduction of volume creates a vacuum which reduces back pressure.

Combustion Chamber. A large space provided in a boiler to allow room for complete combustion to take place. Generally found in Scotch boilers, as the furnace in a watertube boiler is usually large enough to allow for complete combustion.

Condensate. This is the name given to condensed exhaust steam; it is distilled water. Condenser, Steam. A unit in which the exhaust steam from the power plant is condensed into water so as to perform two purposes: First, it reduces the back pressure on the machinery, and second, it makes possible the use of the water over again as feedwater.

Crown Sheet, Boiler. The top sheet of the combustion chamber. Usually found in marine installations using Scotch boilers.

Dampers, Uptake. A pivoted metal plate placed in the uptake or stack of a boiler for regulating draft or closing the stack or uptake. In boilers using oil for fuel, dampers are secured in the open position while the boilers are in use.

Desuperheaters, Steam. A unit by which the superheat is removed from the steam, generally consisting of a series of pipes submerged in the water in the boiler drum through which the superheated steam passes. Desuperheaters are used to protect superheaters by maintaining circulation. Also to supply steam to auxiliaries.

Draft, Stack. The flow of the hot gases from the boiler and the flow of air into the furnaces. NATURAL DRAFT is the natural flow of the cooler air into the furnaces without the aid of any mechanism; FORCED DRAFT is when the air is forced into the furnaces under a slight pressure; and INDUCED DRAFT is when the pressure in the stack is reduced to speed up the flow of air.

Dry Pipe. A perforated pipe running lengthwise in the top of the steam space of the boiler through which the steam must pass before leaving the boiler. The steam in passing through the small holes in the pipe loses most of its moisture particles which otherwise would be carried over from the boiler.

Economizer, Boiler. A feedwater heater located

  in the boiler uptakes which receives its heat from the waste gases from the boiler as they pass on their way to the stack.

Evaporators. Units in which sea water is evaporated so as to obtain distilled water or fresh water for boiler feeding, etc.

Feed and Filter Tank. Generally referred to as the Hotwell (see Hotwell). A tank into which the condensate pump discharges the condensate and in which the feedwater passes through filtering material to remove oil and grease. The filtering material generally is made up of loofa sponges.

Feedwater Heaters. A heater through which the feedwater passes between the feed pump and the boiler in which the feedwater is heated by the heat contained in the auxiliary exhaust steam. Some of the auxiliary exhaust steam instead of flowing to the condenser, is led to the heater. BACK PRESSURE is the pressure of this exhaust steam in the feedwater heater, and is the pressure against which the auxiliary machinery must operate. The BACK PRESSURE VALVE is a valve which admits the auxiliary exhaust steam to the condenser, and is the valve by which the BACK PRESSURE can be regulated.

Feed Pumps. Pumps which take suction from the feed and filter tank or the reserve feed tanks and discharge the feedwater into the boilers under pressure above boiler pressure. Generally a vertical, simplex, double-acting, reciprocating steam pump, although some vessels now use centrifugal pumps, or electric driven triplex pumps.

Feedwater, Boiler. Water which is used to make steam in the boilers. Between the feed tank and the boiler, the water is known as FEEDWATER; between the boiler and the machinery as LIVE STEAM; between the machinery and the condenser as EXHAUST STEAM; and between the condenser and the feed tank as CONDENSATE.

FEEDLINE CHECK VALVES. Valves placed in the feedwater line just before the boiler through which the water may pass in one direction only-toward the boiler. Any flow from the boiler causes the valve to close.

Feedline Stop Valve. A valve placed between the feed check valve and the boiler, attached directly to the boiler shell to out off the flow of water in either direction. Both the feed stop and the feed check valves are required by law.

Fire Pump. A pump of large capacity for supplying sea water to the fire mains. Also has, as

 

118  a rule, a bilge suction connection and a ballast suction connection.

Flareback, Furnace. A dangerous explosion in a boiler furnace due to the ignition of accumulated gases from the fuel. Caused by lighting fires without a torch, leaky burners, etc. Can cause extensive damage to the boiler and result in the death of the fireroom personnel.

Floor Plates. Steel plates which form the decking of the engine room and fireroom.

Foaming, Boiler. The creation of bubbles or froth on the surface of boiler water, caused generally by impurities in the boiler water. Causes water to be carried over from the boiler into the steam lines.

Fresh Water Pump. A pump by which fresh water is delivered from the tanks to wash bowls, showers, etc., for washing purposes.

Furnace, External. A place in which the fuel is burned to produce the heat necessary to evaporate water into steam in the boiler. External furnaces are outside of the boiler shell and generally form part of the boiler setting. Most watertube boilers have external furnaces.

Furnace, Internal. A space within the boiler shell in which the fuel is burned to produce the heat necessary to evaporate water into steam in the boiler.

Fusible Plug. A safety device used in a boiler to warn the operator of dangerously low water. The plug has a hole which tapers to a small diameter and the water side taper is filled with banca tin 99.3% pure. This tin melts before low water harms the boiler. There are two types-waterside and fireside and they are named because of the way they go in. Example: Waterside plug goes in from the waterside of crown sheet or tube.

Gag, Safety Valve. A horseshoe shaped clamp for locking a safety valve closed. Used during annual Hydrostatic test, often referred to as a clamp.

Generators, Electric. Machines which generate electricity for use on shipboard, driven by some type of power unit.

Governor, Speed Control. A device by which the speed of a piece of machinery is regulated.

Handholes. Openings for cleaning boiler. When large enough to permit passage of a man are referred to as manholes. Special plates are used to seal these holes and great care must be used when closing and tightening.

Hotwell. The name sometimes given to the feed and filter tank. It is also the name given to the reservoir at the bottom of the condenser from

  which the condensate pump takes its suction.

Hydrostatic Test. A test put on a boiler with water under a pressure from 11/4 to 11/2 times the safe allowable working pressure of the boiler. Put on by the boiler inspectors, and, while under this pressure, the boiler is inspected for ruptures and leaks.

Ice Machine. The name given to the compressor in the refrigerating system. Driven by some type of power unit.

Injector, Boiler Feedwater. A jet pump by which a jet of steam is used to force feedwater to the boiler. Simple in design, delicate in construction, the injector has been replaced by other types of pumps.

Lance, Hand, Air or Steam. A unit by which a jet of air or steam is directed into tubes of a boiler for removing soot. Operated by hand. Several safety precautions must be observed when using steam lance.

Manifold, Valve. A casting into which a number of pipe lines are led, each pipe opening controlled by a valve.

Main Steam Stop Valve. A valve connected directly to the top of the boiler shell which controls the flow of the steam from the boiler to the main steam line, which supplies only the steam to operate the main engines.

Manhole, Boiler. Generally an elliptical hole to allow the passage of a man's body so that the boiler can be entered for inspection, overhaul, or repairs. Covered from the inside with a plate known as a manhole cover, which is secured from the outside by dogs.

Muddrum, Boiler. A small drum or header located at the lowest point of the boiler into which sediment, sludge, and other impurities of the boiler water precipitate, and from which they are removed by the bottom blowdown valve.

Pressure Gage, Boiler. A gage by which the steam pressure in the boiler is registered. The pipe which connects this gage to the steam space of the boiler is fitted with a valve directly connected to the boiler shell.

Priming, Boiler. An action taking place in a boiler which causes water to be carried over into the steam lines.

Propeller, Screw. A device which, when rotated, causes a vessel to move through the water. Often referred to as the wheel or screw.

Reduction Gears, Speed. Due to the fact that some main engines, such as turbines, are most efficient at high speeds, and that the propeller is most efficient at fairly low speeds, the use of

 

119  gears to reduce speed of screw is necessary.

Refractory, Furnace. Plastic and molded heat-retarding and insulating material used mostly for furnace linings.

Reducing Valve. A valve by which a varying high steam pressure can be automatically reduced to a constant low pressure.

Retarders. Flat, twisted strips of steel usually found in the tubes of firetube boilers, feed heaters, etc. to slow down the flow of the heating agent, so that there is time for more heat to pass through the tube.

Safety Valves, Boiler. Spring loaded valves which are set to open at the safe working pressure of the boiler. Used to relieve excess pressure in the boiler so that the boiler will not explode.

Salinometer Cock. A small cock or valve by which a sample of boiler water can be taken from the boiler for test as to acidity, alkalinity, or salinity.

Sanitary Pump. A pump which delivers sea water to the "heads" for sanitary purposes.

Saturated Steam. See Steam.

Scale, Incrustation. Formations on the plates and tubes of boilers due to the impurities in the boiler water.

Skin Valve, Sea Cock. A valve at the skin or side of the vessel; generally refers to the one on the blowdown lines used to prevent sea water from backing up to the boilers.

Soot Blowers. Mechanical devices attached to the boiler casing through which a steam jet is directed against the surface for removing soot deposits.

Spring Bearings, Main Line Bearings. Those bearings which support the weight of the main propeller shaft between the thrust bearing and the stern tube. They also tend to maintain the alignment of the shaft.

Staybolts, Boiler. Solid and drilled stays which are used to support the combustion chambers in boilers.

Steam. Steam is an invisible vapor produced by the rapid evaporation of water when heat is applied. SATURATED STEAM is steam in direct contact with the water from which it was formed and has the same temperature as the water. It may contain a light amount of moisture in which case it is known as WET SATURATED STEAM, or it may be 100% dry in which case it is known as DRY SATURATED STEAM. If this steam is led to a separate unit known as a superheater, which is placed in the path of the hot gases, its temperature is

  increased above that of the water from which it is formed, and it is then called SUPERHEATED STEAM.

Steam Generators. Steam generators is the name given to the combination of the boiler, superheaters, economizers, air preheaters, de-superheaters etc.

Steering Engine. Due to its large area, it is impracticable to move the rudder by hand; instead, the rudder is turned by a power-driven unit which is known as the steering engine. Stern Gland. The stern gland is a packing gland at the inside end of the stern tube which prevents excessive flow of sea water in through the stern tube. This gland should never be tightened so much that there is no trickle of water through the stern tube, except in port, because this water trickle supplies lubrication to the stern tube.

Stern Tube. The tube or bearing through which that part of the propeller shaft (tail shaft) which contains the propeller passes through the stern of the vessel, generally lined with lignum vitae.

Superheaters, Steam. Units generally consisting of a number of tubes through which saturated steam passes, and over which the hot gases of combustion of the boiler pass so that the steam may be heated to a higher temperature.

Superheated Steam. See Steam.

Surface Blow. See Blowdown Valves.

Tail Shaft. The last portion of the propeller shaft, which passes through the stern tube, and onto which the propeller is fastened.

Telltale Holes, Staybolt. Small holes drilled in the ends of staybolts so that if the staybolt breaks or cracks, the steam and water will escape through the hole to the outside of the supported space to give warning of the break.

Throttle Valve, Main Engine. The valve by which the speed of the engine may be regulated by controlling the supply of steam flowing to the engine.

Thrust Bearing, Main Shaft. A bearing on the main shaft to prevent endwise movement of the shaft, so that the thrust of the propeller is transmitted along the shaft to the thrust bearing which transfers the thrust to the hull of the vessel.

Trap, Steam. A unit for allowing passage of condensate but preventing passage of steam.

Try Cocks, Boiler Water Level. Three small valves or cocks connected directly to the boiler shell at the water level so that the accuracy of

 

120  the gage glass can be checked. One is located above, one at, and the other below the normal steaming water level (approximately).

Turning Gear, Jacking Gear. A unit which when engaged may be used for slow turning of the engine or preventing the engine from rolling over accidentally. Never engaged while steam is on main engine.

Uptakes, Furnace. Passages through which the gases of combustion, on leaving the boiler, are led to the stack.

  Water Level Gage. A means by which the water level in the boiler is visible to the operating personnel, generally consisting of a glass tube for low pressure boilers, and a special nonshatterable glass gage for high pressure boilers.

Wet Air Pump. When the condensate and the air are both removed from the condenser by the same pump, the pump is known as a wet air pump. This system does not maintain as high a vacuum in the condenser as when the two pumps are used.