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CHE 324CHE 324PROCESS PLANT OPERATIONS & MAINTENANCE

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An Overview Of Facilities An Overview Of Facilities Service Function & Service Function & RegulationsRegulationsEnvironmental Quality Act, 1974 Malaysia has had environmentally-related legislation

since the early 1920s (table 4). But the legislation is limited in scope and inadequate for handling complex emerging environmental problems. So through EQA, 1974, a more comprehensive form of legislation and an agency to control pollution was established.

EQA is an enabling piece of legislation for preventing, abating and controlling pollution, and enhancing the environment, or for other related purposes. Pollution, as declared in EQA, includes the direct or indirect alteration of any quality of the environment or any part of it by means of a positive act or act of omission.

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Pollution is ‘controlled’ through the mechanism of licences issued by the Department of Environment. The mode of control is by prescribing, by means of a ministerial regulation, that licences are mandatory for:- The use and occupation of prescribed premises;

- Discharging or emitting wastes exceeding acceptable conditions into the atmosphere, as well as noise pollution, polluting or causing the pollution of any soil or surface of any land; - Emitting, discharging or depositing any wastes or oil, in excess of acceptable conditions, into inland waters or Malaysian waters.

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Environmental laws and Environmental laws and regulationsregulations One of the three strategies embodied in

EQA, 1974, is for the regulation of pollution. The other two strategies are for preventing and abating any form of pollution. To bring the law and other environmentally-related laws into effect, the laws and regulations listed below have been introduced and are strictly enforced by the Department of Environment.

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Occupational Safety and Occupational Safety and Health Act 1994 Health Act 1994 The Department of Occupational Safety and Health

(DOSH), under the Ministry of Human Resources, has been assigned the responsibility of administrating and enforcing legislation related to occupational safety and health (osh) to ensure that safety, health and welfare of people at work as well as others are protected from hazards resulting from occupational activities in the various sectors which include manufacturing; mining and quarrying; construction; agriculture, forestry and fishing; utilities (gas, electricity, water and sanitary services); transport, storage and communication; wholesale and retail trades; hotels and restaurants; finance, insurance, real estate and business services; public services and statutory authorities.

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Chapter 2Chapter 2

Prime movers Pumps Steam turbines Gas turbine

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Pumps Pumps

Pump Application and Classification Refineries and chemical plant use pumps to

move liquid. Pumps can be classified as dynamic and

positive displacement. Both classes are designed to transfer liquids,

but the way the transfer is accomplished is different.

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Dynamic PumpsDynamic Pumps Dynamic pumps accelerate liquids axially (in

a straight line) or centrifugally (in circles) They are operated at high speeds to

generate large flow rate at low discharge pressures.

Pressures moves the liquid through the piping and equipment system.

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Positive Displacement (PD)Positive Displacement (PD) Transfer liquids by using a rotary or

reciprocating motion that displaces liquid on each rotation or stroke.

They are used in processes that require specific amounts of fluid to be delivered.

They transfer specific amounts of fluid no matter what the discharge pressure is, whereas the amount of fluid transferred by dynamic pumps is greatly affected by discharge pressure.

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Rotary pumps deliver a specific amount of fluid with each rotation of screws, gears, vanes or similar elements.

Reciprocating pumps move fluids by drawing them into a chamber on the intake stroke and pushing them out of the chamber with a piston, diaphragm or plunger on the discharge stroke.

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Dynamic

Axial

Centrifugal

Vertical

Multistage

Single- stage

Horizontal

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Positive Displacement

Reciprocating

Rotary

Diaphragm

Plunger

Piston

Flexible vane

Sliding Vane

Internal Gear

External Gear

Screw Pump

Lobe Pump

Single Progressive Cavity

Multiple

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Steam Turbines/ engineSteam Turbines/ engineA turbine is a rotary engine that extracts energy from a fluid flow. A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work.A conventional steam electric power plant/power station converts fossil fuels - coal, gas or oil - into electric energy. Fuel burned in the boiler releases heat, which boils water and converts it into high-pressure superheated steam.The steam enters a turbine where it expands and pushes against blades to turn the generator shaft to create electric current. After the steam passes through the turbine, condensers convert it to water, which is then returned by pumps to the boiler to repeat the cycle.Combustion gases exit through the stack.

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Steam Turbine

16A rotor of a modern steam turbine, used in a power plant

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Classification Of Steam Classification Of Steam TurbinesTurbines1. Condensing Exhaust steam flows into a heat exchanger called

surface condenser that cools and condenses the steam.

The condensate is sent to the boiler, where it is converted back to steam.

Operate at vacuum pressure The most efficient type because they extract the

maximum amount of energy from the steam.

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Classification Of Steam Classification Of Steam TurbinesTurbines2. Noncondensing Exhaust gas is utilized in low- pressure

steams application.

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Classification Of Steam Classification Of Steam TurbinesTurbines3. Reaction Steam is discharged from a nozzle mounted

on the rotor. Movement is a reactive response to the

release of steam from an internal source.

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Classification Of Steam Classification Of Steam TurbinesTurbines. 4. Impulse Steam from an external source acts on the

rotor to create movement.

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Operating principlesOperating principles

The primary operating principle of a turbine is to convert steam energy into mechanical energy that can be used to drive rotating equipment.

A steam turbine is a device (driver) that converts kinetic energy (steam energy of movement) to mechanical energy.

Steam turbines have a specially designed rotor that rotates as steam strikes it.

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Operating principlesOperating principles

As high-pressure steam enters a turbine, it passes through a device called a nozzle.

Nozzles restrict the flow and increase the velocity of the steam.

The nozzle directs this high-velocity steam against the blades of a paddle-wheel, causing it to rotate.

As the steam passes through alternate sets of fixed and revolving blades, it constantly expands as it moves along.

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Moving Blade Impuls

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Operating principlesOperating principles

The rotating paddlewheel is attached to a shaft, and the blading and shaft together make up the rotor.

Impulse or reaction movement occurs as the steam strikes the rotor, converting the steam energy into mechanical energy.

The amount of steam energy needed to perform useful work depends on the pressure range through which the steam expands.

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Operating principlesOperating principles

The steam used to operate a steam turbine is produced in a boiler.

Boilers produce steam that can enter a turbine at temperature as high as 538oC (average 1 000 to 1 050oF) and pressure as high as 3 500 psi inlet and 200 psi outlet. (steam turbines can also run under a vacuum.)

High pressure steam is admitted slowly into a turbine to warm it up and remove condensate (moisture produced by condensation)

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Steam turbines are used to drive the electric generators in modern power plants.

Modern turbine technology includes 50 or more stages linked along a horizontal shaft.

Each stage consists of a set of moving or stationary blades.

The curved blades of each stage are designed so that the spaces between the blades act as nozzles and increase steam velocity.

Operating principlesOperating principles

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Operating principlesOperating principles

As the steam zigzags between the stationary and moving blades, it begins to expand as much as 1000 times its original volume.

Modern turbine design increases the size of each stage, giving the turbine a conical shape.

Figure 6.1 pg 137

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Impulse turbine & reactive steam turbines Have a blading design that causes rotation of

the blade- and –shaft assembly, or rotor, when high- velocity steam pushes on the blades.

The kinetic steam source is external Reactive movement occurs when steam

escapes from a fixed nozzle attached to the rotor, propelling the rotor.

The kinetic steam source is internal.

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Basic Components of a Steam turbineFour grouping Rotor Fixed parts Governing mechanism Lubrication system

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Basic Components of a Steam turbineRotor The assembly consisting of the shaft and the

rotating blades. Statically and dynamically balanced to

ensure smooth operation.

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Rotor

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Fixed parts

The principal stationary parts in a steam turbine are the :

a) fixed bladesb) Throttle valvec) Steamtight casingd) Steam cheste) Nozzlef) Bearingsg) Ringsh) seals

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Fixed blades

Made of durable stainless steel that has been rolled and drawn.

Half- moon – shaped ring located in the lower section of the turbine, sandwiched between the moving blades.

When fixed and rotating blades are aligned in the correct position, steam passages are formed across the wheel of the turbine.

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Diaphragm

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Casing

Composed of a base and covering made of carbon steel or turbine iron.

The base and the covering are designed to form steamtight joints.

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Steam Chest

Houses the governor valve and steam strainer ( a mechanical device that removes impurities from steam)

Composed of carbon steel or iron and is bolted to the lower casing.

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Nozzle

Constitute a precision instrument fabricated from a solid block of high-tensile carbon silicon steel that directs high-velocity steam against the rotor.

Nozzle blocks are bolted to the steam chest. Has overlapping exits that allow the steam

jets to converge before being directed against the buckets of the rotor.

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Nozzle

                                                                                                                                      

                   

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Bearing

Provide radial and axial support for the shaft of a steam turbine.

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Steam Turbine Problems

Vibration

- vibration-sensing equipment is used to monitor turbine performance.

-

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Advantages of steam turbines

High efficiency at high speed. Far fewer moving parts, hence potentially greater

reliability. Conventional piston steam locomotives give a

varying, sinusoidal torque, making wheelslip much more likely when starting.

The side rods and valve gear of conventional steam locomotives create horizontal forces that cannot be fully balanced without substantially increasing the vertical forces on the track, known as hammer blow.

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Disadvantages of steam turbines High efficiency is ordinarily obtained only at high speed (though

some Swedish and UK locomotives were designed and built to operate with an efficiency equal to or better than that of piston engines under customary operating conditions). Gas turbine locomotives had similar problems, together with a range of other difficulties.

Peak efficiency can be reached only if the turbine exhausts into a near vacuum, generated by a surface condenser. These devices are heavy and cumbersome.

Turbines can rotate in only one direction. A reverse turbine must also be fitted for a direct-drive steam turbine locomotive to be able to move backwards.

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Task 2

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Gas Turbine

A gas turbine is a rotary machine, similar in principle to a steam turbine.

It consists of three main components - a compressor, a combustion chamber and a turbine

A gas turbine extracts energy from a flow of hot gas produced by combustion of gas or fuel oil in a stream of compressed air.

It has an upstream air compressor (radial or axial flow) mechanically coupled to a downstream turbine and a combustion chamber in between.

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Theory of operation

Gas turbines are described thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.

The air after being compressed into the compressor is heated either by directly burning fuel in it or by burning fuel externally in a heat exchanger.

The heated air with or without products of combustion is expanded in a turbine resulting in work output, a substantial part, about two-thirds, of which is used to drive the compressor. The rest, about one-third, is available as useful work output.

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Energy is released when compressed air is mixed with fuel and ignited in the combustor. The resulting gases are directed over the turbine's blades, spinning the turbine, and mechanically powering the compressor. Finally, the gases are passed through a nozzle, generating additional thrust by accelerating the hot exhaust gases by expansion back to atmospheric pressure.

Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft, trains, ships, electrical generators, and even tanks.

http://www.howstuffworks.com/turbine.htmhttp://videos.howstuffworks.com/science

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