ANAND INSTITUTE OF HIGHER TECHNOLOGY

KAZHIPATTUR

ELECTRONICS AND INSTRUMENTATION DEPARTMENT

EI2021 POWER PLANT INSTRUMENTATION

STAFF NAME: R.UMASHANKARI, M.SURYA SUBJECT CODE:EI2021

DESIGNATION: LECTURER CLASS: IV YEAR EIE

QUESTION BANK

OVERVIEW OF POWER GENERATION

Unit – I

Part A– Questions

1. Quote two examples of cogeneration systems.( AU/Dec –2007)

In industries, such as rayon, pulp and paper, chemical processing and

textile which require simultaneous steam and power, it is possible to meet

either part or full heat and power requirements using steam turbine, gas

turbine with heat recovery boiler.

Cement kilns and brick kilns require a large amount of high temperature

process heat. The gas turbine exhaust, with or without supplementary

firing, can supply this heat and produce electric power for the factory.

In glass melting furnaces, heat from the exhaust gases can be recovered in

waste heat boiler to produce steam. The steam can be expanded in steam

turbines to produce electrical power.

2. Mention the four significant need of instrumentation in power

generation. (AU/Dec – 2007)

Instruments used in power plants furnish accurate information for guidance

to safe, continuous and proper plant operation.

The information given by the recording units from the control room helps to

direct its operation so as to achieve the best performance and furnish data

for calculation so that results may be compared from time to time. There

may be used to check on the internal condition of equipment and indicate

when and where maintenance or repair is needed.

The function of instrumentation is to measure the pressure and temperature

of steam and feed water.

Instrumentation is needed for flow, drum level measurement and air floe

recording etc.,

3. What does SAMA stand for in SAMA diagram for boiler control

process? (AU/ Dec –

2006)

4. What is SAMA diagram for boiler control process? (AU/May- 2008)

5. What is enriched Uranium? (AU/Dec- 2008)

Enriched uranium is uranium that has had its U-235 isotope content elevated above

what it would be when we refine natural uranium after recovering the metal from

ore. U-235 is the desired fissionable isotope of uranium, but it is the isotope U-238

that is present in over 99% of all the naturally occurring uranium. We have to put

the uranium through a process to separate the U-235 from the U-238. As these two

isotopes are chemically identical, it takes a mechanical process to separate them.

After running the uranium through a process designed to take advantage of the

difference in the mass of the two atoms, the industry will recover uranium with a

very high percentage of the U-235 isotope, and this is called enriched uranium.

6. Define the role of boiler control. (AU/Dec- 2008)

The role of boiler control is,

Through the boiler control system, the boiler energy and mass

balances are managed.

All the boiler major energy and mass inputs must be regulated in

order to achieve the desired output conditions.

7. What is meant by the term cogeneration? (AU/Dec- 2008)

Cogeneration is an energy conservation technology. It is defined as the sequential

production of electricity and steam energy from the same fuel source. It is

employed to capture the heat energy availability which would otherwise be lost in

the normal operation of a traditional power plant or an industrial process. For

instance, heat from the exhaust gases of a gas turbine power plant could be made

use of in the waste heat recovery boiler to produce process steam.

8. What are the basic factors to be considered during the design of a

nuclear power reactor? (AU/Jun- 2006)

The reactor is a source of intense radio activity. These radiations are very harmful

to human life. It requires strong control to ensure that this radio activity is not

released into the atmosphere to avoid atmospheric pollution. A thick concrete

shielding and a pressure vessel are provided to prevent the escape of these

radiations to atmosphere.

9. Mention the parameters on which depends the power output from a

hydro-electric power plant. (AU/Jun- 2006)

The quantity of water available and head is equally important in the generation

of power. The available head depends upon the selection of site for hydraulic

power plant. The quantity of water available at the selected site depends upon the

hydrological cycle of nature. As the availability of water depends on the natural

phenomenon of rain, the maximum capacity of hydraulic generating plant is

fixed on the basis of minimum quantity of water available.

10. What does fission mean? (AU/Jun- 2007)

Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei)

often producing free neutrons and other smaller nuclei, which may eventually

produce photons (in the form of gamma rays). Fission of heavy elements is an

exothermic reaction which can release large amounts of energy both as

electromagnetic radiation and as kinetic energy of the fragments (heating the bulk

material where fission takes place). Fission is a form of elemental transmutation

because the resulting fragments are not the same element as the original atom.

11. What is once through boiler? (AU/Jun- 2007)

In the once-through boiler design, all feed water entering the once-through

system is warmed up, evaporated, and superheated in a once-through mode

(Benson principle). The location of the endpoint of evaporation is not fixed like

in the drum-type boiler design. It automatically moves between one or more

heating surfaces in such a way that, depending on the load, fouling of the heating

surfaces and the amount of excess air, the main steam temperature always

remains constant. The once-through principle can be adopted for subcritical and

supercritical steam conditions, even far above the critical pressure of 3206 psia

(221 bar).

12. Specify the typical power generation mix of India. (AU/Dec- 2008)

Thermal power plant

Wind power plant

Hydro power plant

13. Mention the importance of Instrumentation system in power plants.

(AU/Dec- 2008)

Instruments used in power plants furnish accurate information for guidance

to safe, continuous and proper plant operation.

The information given by the recording units from the control room helps to

direct its operation so as to achieve the best performance and furnish data

for calculation so that results may be compared from time to time. There

may be used to check on the internal condition of equipment and indicate

when and where maintenance or repair is needed.

The function of instrumentation is to measure the pressure and temperature

of steam and feed water.

Instrumentation is needed for flow, drum level measurement and air flow

recording etc.,

14. Name the commonly used moderators in nuclear power plants.

(AU/Jun- 2006)

Commonly used moderators include

Regular (light) water (roughly 75% of the world's reactors)

Solid graphite (20% of reactors)

Heavy water (5% of reactors)

Beryllium has also been used in some experimental types

Hydrocarbons have been suggested as another possibility.

15. Mention 3 materials used for insulation of steam pipes. (AU/Jun- 2006)

Calcium silicate is used to insulate high-temperature pipes

Coal

Water, solar, wind

16. What is pulverized coal? (AU/May- 2008)

For use in thermal power plants, coal is ground into dust using a device

called a powdered coal mill. The resulting product, called powdered

coal or pulverized coal, is then generally used in a fossil fuel power

plant for electricity generation. Pulverized coal is a significant dust

explosion hazard, as large quantities are suspended in air for transfer from

the mill to the powerplant.

17. Name any two building blocks of wind power generation. (AU/May-

2008)

Aero turbine

Rotor

Generator

18. What are different methods of power generations? (AU/May- 2008)

Thermal Power Generation

Wind Power Generation

Solar Power Generation

Nuclear Power Generation

Hydro-electric Power Generation

19. What are the thermal power plant (Steam) circuits?(May2011)

Coal and ash circuit,

Air and gas circuit,

Feed water and steam circuit,

Cooling water circuit

20. Write working principle of photovoltaic cell?(2012)

Photovoltaic (PV) cells are made up of at least 2 semi-conductor layers. One layer

containing a positive charge, the other a negative charge. Sunlight consists of little

particles of solar energy called photons. As a PV cell is exposed to this sunlight, many

of the photons are reflected, pass right through, or absorbed by the solar cell. Solar cell

can connected in series and parallel in form of array on panel to get the desired rating

of voltage and current.

21. Define the role of boiler control. (2012)

Boilers are often the principal steam or hot-water generators in industrial plants.

Consequently, they must be designed to operate efficiently and safely while responding

rapidly to demand changes. Burner-management systems must be equally adaptive.

Control techniques are capable of reducing operating costs while providing greater

flexibility in plant management and control. Tools for burner combustion control

generally include regulation of excess air, oxygen trim, burner modulation; air/fuel

cross-limiting and total heal control. The better burner control systems include all of

these elements.

22. What are the two major advantages of thermal power plant?(Nov/Dec-2009)

(i) The power generation is not dependent on nature’s mercy

(ii) Transmission cost and transmission loss is less.

23. What do you understand by water hammer?

When there is sudden increase of pressure in the penstock due to sudden back

flow of Water, the load on the turbine is reduced. The sudden rise of pressure in the

penstock Known as water hammer.

24. State any two major advantages of hydro power plant.

(i) No air pollution (ii) water is the cheapest source of energy and it is renewable.

23. What are the components of nuclear l power plant?

(i) Nuclear reactor (ii) Steam generator (iii) Condenser (iv) Turbine (v) Power generator.

24. Explain the term nuclear fission.

The U235

exists in the isotope form and it is unstable. When a neutron enters the nuclear

of U235

the nuclear splits into two equal fragments and releases 2.5 fast moving neutrons

with a velocity of 1.5X107 m/sec and also large amount of energy. This is called nuclear

fission.

25. What is the function of moderator and give examples?

The moderator is to reduce the energy of neutrons evolved during fission in order to

maintain the chain reaction. Example. Heavy water and ordinary water

26. What is the use of regenerator?

In the regenerator the heat of the hot exhaust gases of high pressure turbines. It is placed

in between high pressure and low pressure turbines.

27. Write principle of Solar cell?

Solar cells directly convert solar energy to D.C. power. These cells are made of

Semiconductors that generate electricity when they absorb light. The silicon cell consists

of a single crystal of silicon into which a doping material is diffused to form a

semiconductor.

28. Write some nuclear fuels.

Fuel of nuclear reactor should be fissionable material which can be defined as an

element of isotope whose nuclei can be caused to undergo nuclear fission by nuclear

bombardment and produce a fission chain reaction. U233,

U235

and Pu239

.

29. What is a function of surge tank?

Surge tank is a reservoir fitted to the penstock at a point near to the turbine. When the

load on the turbine decreases the gates of the turbine are closed partly by the governor to

adjust the rate of flow of water in order to maintain constant speed of the runner. When

the gates are closed the water is moving to the turbine has to move backward. This

backward moving water is stored in the surge tank. Similarly when the load on the turbine

increases the turbine gates are opened by the governor and increased demand of water is

partly met by the water stored in the surge tank. Thus the surge tank controls the water

when the load on the turbine decreases and supplies water when the load on the turbine

increases.

30. What is a function of super heater?

The steam produced in the boiler is nearly saturated. This steam as such should not be

Used in the turbine because the dryness fraction of the steam leaving boiler will be low.

This results in presence of moisture, which causes corrosion of turbine blades. To raise the

temperature of steam super heater is used.

31. What is a function of Reheater?

The steam produced in the boiler is nearly saturated this steam as such should not be used

in the turbine because the dryness fraction of the steam leaving boiler will be low. This

results in presence of moisture, which causes corrosion of turbine blades. To raise the

temperature of steam more the steam from the super heater is again heated the reheater.

32. What is a function of Penstock?

Penstock is a closed pipe or tunnel which is used to carry water from the dam or forebay

to the turbine. It is desirable that the penstock should be sloping towards the power house

and it’s made up of steel, reinforced concrete and wood.

33. What is an isotope? Give example.

The same atomic number but with different mass numbers ie different number of neutrons

known as isotopes. The isotope may be stable or radioactive. Example: deuterium, tritium

34. What is a function of Economizer?

In order to utilizing the heat accompanying combustion gases leaving the furnace, the

gases are passed through the heat recovery equipment such as economizer and air pre

heater. Economizer is a device intended for heating the feed water by means of flue gases

from the boiler.

35. What is a function of Control rods?

Control rods in the cylindrical or sheet form are made of boron or cadmium. These rods

can be moved in and out of the holes in the reactor core assembly. Their insertion absorbs

more neutrons and damps down the reaction and their withdrawal absorbs less neutrons.

Thus shifting control rods this may be done manually or automatically controls power of

reaction.

36. What is cogeneration?

The steam which is fed to the turbine is taken out of it before the turbine exhaust. It is

called extracted or bleeds steam. Exhaust steam or bleed steam is used for space heating,

refrigeration and process heat i.e. can be used for other power generation plants.

37. What is fission? Give some fission materials.

Nuclear materials that will undergo a division of the atomic nucleus into two or more

fission fragments with an accompanying release of large amounts of energy and more

neutrons are called fissile materials. Fission is usually triggered by the capture of neutron,

but some atoms undergo spontaneous fission. Example Pu239, U233.

38. What are the types of solar energy collectors?

(i)Flat plate (ii) Concentrating (iii)Line focusing (iv)Point Focusing

Part –B Questions

1. Compare the various methods of power generation and present the

summary in a table from various factors. (AU / Dec – 2007) (AU / June –

2006)

2. Draw the overall layout of thermal power plant and present the four major

cycles of operation involved. (AU / Dec – 2007)

3. Explain the boiler process. (AU / Dec – 2007)

4. With a neat sketch explain the process of electric power generation in a

nuclear power plant. (AU / Dec– 2006) (AU / Dec – 2008) (AU / May –

2008)

5. With neat sketch, explain in detail the constructional feature and operation

of thermal power plant. (AU / Dec– 2006) (AU / June – 2006) (AU / May

– 2008)

6. With a block diagram, explain operation of thermal power plant and

mention the important (AU / May – 2008) parameters to be monitored in

each blocks. (AU / May – 2008)

7. Draw and mention the function of piping and Instrumentation diagram of

a boiler system in a power plant. (AU / May – 2008)

8. Write short note on cogeneration.(AU / June – 2006) (AU / June – 2007)

(AU / May – 2008)

9. with neat sketches explain the process of converting solar energy into

electrical energy. (AU / June – 2007)

10. Write notes on harnessing the wind. (AU / June – 2007) (AU / May –

2008)

11. What is meant by cogeneration? Also explain the topping and bottoming

cycle operation of cogeneration system. (AU / Dec – 2008)

12. Briefly explain the importance of instrumentation in power generation.

(AU / June – 2006)

13. Describe the different types of steam generators. (AU / May – 2008)

14. Briefly explain about once through boiler. (AU / May – 2008)

15. Briefly explain about solar cells. (AU / May – 2008)

16. with a block diagram, explain in details the operation of nuclear power plants and

also mention the important parameters to be monitored in each block.(2012)

17. List the various parameters to be measured and monitored in thermal power plant.

Also mention its locations.(2012)

MEASUREMENTS IN POWER PLANTS

Unit – 2

Part –A Questions

1. Why is drum level measurement very important? How is it taken care of?

(AU/Dec- 2007)

Fluid approaching the object starts losing its velocity till directly in front of the

body where the velocity is zero. This point is known as stagnation point. It is an

obstruction type primary element, used for fluid flow measurement. It produces large

differential pressure with low pressure loss.

2. How is the correction factor for temperature accounted during

measurement of steam flow? (AU/Dec- 2007)

Float density less than the fluid density, level increases float moves up, resistance

connected float varies, so output varies. Voltage output is proportional to the density of

the fluid.

3. What is Dall tube? (AU/Dec- 2006)

It is an obstruction type primary element, used for fluid flow measurement. It

produces large differential pressure with low pressure loss.

4. What are the two scales used for temperature measurements in power

plants? (AU/Dec- 2008)

good accuracy

can be easily applied to automatic liquid batching system

good repeatability

moderate cost

5. Specify the device used for current and voltage measurement in power

plant. (AU/Dec- 2008)

high cost

subject to leakage

problems created by dirty particle

high maintenance cost

restricted to moderate flow rates

6. Why float type level measurement is not suitable for boiler drum level

measurement? (AU/Dec- 2008)

(i) Wet meter- manometer which is calibrated with mercury

(ii) Dry meter- manometer which is calibrated with mercury

7. How can following parameters be measured energy, resistance, current

and power? (AU/Jun- 2006)

It is an example of variable area flow meter. When fluid enters lopped moves

from the bottom to top. Distance is proportional to the flow rate.

8. What are the methods adopted to monitor fine particle emissions? (AU/Jun- 2006)

They can become plugged with sediment and that the pressure difference

sensed may not be large enough to give the desired accuracy for the flow rate under

consideration. Fluid approaching the object starts losing its velocity till directly in

front of the body where the velocity is zero. This point is known as stagnation point.

9. What is the application of Geiger counter in power plants? (AU/Jun- 2006)

Reciprocating piston type

Rotating vane type

Lobed impeller type

Oscillating piston type

10. Mention the application of Ringlemann chart? (AU/Jun- 2006)

o high cost

o subject to leakage

o problems created by dirty particle

o high maintenance cost

o restricted to moderate flow rates

11. What is an ever clean window? (AU/Jun- 2007)

Float density less than the fluid density, level increases float moves up, resistance

connected float varies, so output varies. Voltage output is proportional to the density of

the fluid.

12. What is the need of connecting thermocouples in series and parallel

during temperature measurement? (AU/Dec- 2008)

It has low pressure drop

It can be used as bi-directional meter

Available in large pipe size & capacities.

13. List the various methods of flow measurement for feed water flow in

power plant. (AU/Dec- 2008)

available in small size

suitable for clean fluids

14. What is the thermal efficiency of Carnot cycle? (AU/Jun- 2006)

It is a flow meter mainly used to measure the flow rate of the fluid. Flow

rate is measured by the difference between the upstream pressure and

downstream pressure.

15. Write the principle of ionization chamber or ionization smoke detectors.

(AU/Nov-2009)

Ionization chamber: it works on the principle that electrically charging the air with

an open detector chamber; the charged air being electronically measurable and can be

monitored. It consists of a small radioactive source, which irradiates the space between the

electrodes with alpha particles, thus creating ions of both signs whose movement towards

respective electrodes constitutes a minute electric current.

16.Write the principle of fire alert ionizing chamber.

The principle operation of fire alert ionization chamber detector is basically simple

series resistance, capacitance (RC) circuit. The charging current to charge the capacitor (C)

is supplied by the ionizing air in the sample chamber, which constitutes the resistance (R).

The charge carriers are a mixture of electrons and positive ions produced by high velocity

alpha particles. The positive ions enter the sample chamber. The circuit resistance varies

according to the conditions whether it is at normal or firing.

17. What are primary measurements of power plant?

(i) Pressure measurement of steam, feed water, turbine bleeds, heater steam

and deaerator, drafts an very low pressures.

(ii) Temperature measurement of superheated steam, feed water and gas temperature.

(iii) Flow measurement of super heated steam feed water , fuel and air blow.

(iv) Level measurement of boiler drum water level.

18. What is the difficulty in slight glass technique in boiler level measurement?

The measurement of drum level is difficult by manual mode, so, we are adapting

slight glass technique. The difficulty in slight glass technique is parallax error.

19. How to measure frequency of the electrical signal?

The output of electrical signal is pure sine waveform in case of AC signal. It can be

measured by amplitude and time division pre second. The measuring device can be an

CRO. F=1/T

20. What do you mean by shrinking effect of boiler drum level?

When the boiler load is reduced, the concentration of steam bubbles in the mixture,

average density of the mixture increases, and volume of the steam-water mass decreases.

The effect is an immediate reduction in the drum level although the mass of water and

steam hasn’t changed. This effect of a sudden reduction in drum water level on a decrease

in steaming rate is called shrink.

21. What is the principle of Electro dynamometer?

By taking up a permanent magnet moving coil, it would have a torque in one direction

during one half of the cycle and an equal effect in other direction. In electrodynamometer

instruments the field can be made to reverse simultaneously with the current in the

movable coil if the field coil is connected in series with the movable coil.

22. What is the principle of smoke density measurement?

Smoke meter works on the principle of passing a focused light beam through the duct

or Chimney on a photocell and the variations in the signal of the photocell circuit will be a

measure of the variation of the obstruction of the light source due to the smoke and dust in

the gases.

23. What is the principle of radiation detector?

Radiation always consists of charged particles such as alpha and beta rays and the

detector materials are chosen so that charged particles i.e. ions are produced as the

radiation is absorbed or passes through the detector. The charged particles are collected

on an electrode in the detector, resulting in a measurable electric signal.

24. What do you mean by swelling effect of boiler drum level?

Swell: when the boiler load is increased, the concentration of steam bubbles under

the water surface increases, the result is that the volumetric proportions in the water

steam mixture changes and average density of the mixture decreases, and volume of the

volume of the steam-water mass increases. This causes an immediate increase in the

drum level even though additional water has not been added. This effect of a sudden

increase in drum water level as the steaming rate is increased is known as well.

25. What are the types of radiation detectors?

Ion chamber, Geiger-Muller, Semiconductor, Fission chamber, Scintillation crystal.

26. What are the instruments used to measure feed water temperature?

These temperatures are frequently recorded and are measured by thermometers with

pressure filled thermal expansion elements. Resistance or thermocouple type elements are

also used.

27. What are the different methods of power factor measurement?

i) Electro dynamic instruments

ii) Ferro dynamic instruments.

28. What are secondary power plant measurements?

Measurement of smoke density, pH and electrical conductivity of boiler water and

feed water, speed of turbine.

29. What are parameters involved in measuring electrical measurements in power

plants?

Current and voltage: moving coil & moving iron meters.

Power: electro dynamometer, induction type instruments.

Power factor: Electro dynamic instruments & Ferro dynamic instruments.

30. Why drum level measurement is critical?

Since, the drum is kept at higher level from the ground level, it is not possible to measure

the level of the drum by manually, and so slight glass technique is used for measurement.

31. What is the use of dust monitor?

The central electricity research laboratory collects the sample of grit and dust on a glass

plate and measures the obstruction caused by deposition using optical means. This

instrument particularly gives a warning of an emission likely to cause a nuisance.

32. What is the difficulty in slight glass technique in boiler level measurement?

The measurement of drum level is difficult by manual mode, so, we are adapting slight

glass technique. the difficulty in slight glass technique is parallax error .

33. How to measure frequency of the electrical signal?

The output of electrical signal is pure sine waveform in case of AC signal. It can be

measured by amplitude and time division pre second. The measuring device can be an

CRO. F=1/T

34. What do you mean by shrinking effect of boiler drum level?

When the boiler load is reduced, the concentration of steam bubbles in the mixture,

average density of the mixture increases, and volume of the steam-water mass decreases.

The effect is an immediate reduction in the drum level although the mass of water and

steam hasn’t changed. This effect of a sudden reduction in drum water level on a decrease

in steaming rate is called shrink.

35. What is the principle of Electro dynamometer?

By taking up a permanent magnet moving coil, it would have a torque in one direction

during one half of the cycle and an equal effect in other direction In electrodynamometer

instruments the field can be made to reverse simultaneously with the current in the

movable coil if the field coil is connected in series with the movable coil.

36.Why float type level measurement is not suitable boiler drum level measurement?

(Nov-2012)

Boiler steam drum water level is one of the most important power plant parameters to both

measure and control. Control of the proper water level in the boiler is critical for safe

operation of the boiler. If the level is too low, boiler tubes will be damaged by overheating.

If the level is too high, steam separators will not function properly, temperature control

will be difficult, and the super heater tubes and turbine could be damaged by moisture or

water treatment chemical carryover. In addition, poor level control will also adversely

affect the drum pressure control.

37.What is a surge tank?( Nov-2012)

A surge tank is a small reservoir in which the water level rises or falls to reduce the

pressure swings during opening and closing of inlet valve. The surge tank is not required

for run off plants and medium head plants.

Part –B Questions

1.Which of the electrical parameters so you think is a must to be measured in

power plants? Why? Explain any two. (AU/Dec- 2007)

2.Explain how is a radiation detector useful for measurement in power plant?

(AU/Dec- 2007)

3.Explain how moisture is eliminated from saturated steam with relevant sketches

of the equipment in a steam power plant. (AU/Dec- 2006)

4.Explain how a U- tube mercury manometer can be used for measuring steam

pressure. Which device is suitable for high pressure? Explain the operation of the

same. (AU/Dec- 2006)

5.Explain a primary and secondary element each in the measurement of feedwater

flow. (AU/Dec- 2006)

6.What is the principle behind vortex flow meter. (AU/Dec- 2006)

7.Specify the need of drum level measurement. Also explain the differenetial

pressure method to measure the drum level in high pressure boiler. (AU/Dec-

2008)

8.List all the major temperature measurement points in a thermal power plant and

also suggest suitable sensor for each points. (AU/Dec- 2008)

9. Explain how real tower and reactive power can be measured. (AU/Jun- 2006)

10.Discuss about the ocrretion factor for temperature. (AU/Jun- 2006)

11.What are the emissions from a coal fired power plant? Give their

classification.(AU/Jun- 2006)

12.Explain the different methods of measuring power frequency with relevant

sketches. (AU/Jun- 2007)

13.What is a boiler drum? Explain in detail measurement of drum level. (AU/Jun-

2007)

14.Classify the transducers based on low, medium and high temperature

applications. Also list the major temperature measurement points and suggest

suitable sensors. (AU/Dec- 2008)

15.List the various types of radiation detector. Also explain the method of

measuring dissolved oxygen content. (AU/Dec- 2008)

16.Explain an unbonded stain gauge pressure transducer. (AU/May- 2008)

17.Which device is used for high-pressure measurement in power plants? Explain

the operation of the same. (AU/May- 2008)

18.Explain with neat sketches capsule and below gauges. (AU/May- 2008)

19.What is meant by Dall tubes? Discuss. (AU/May- 2008)

20.Name the type of differential pressure flow meter used in a feed water line of a

boiler. Explain its principle of operation with a neat diagram. (AU/May- 2008)

21.Write short notes on smoke density measurement. (AU/May- 2008)

22.Describe the three element boiler drum level measurement. (AU/May- 2008)

23.classify the transducers based on low, medium and high temperature

application. Also list the major temperature measurement points and suggest

suitable temperature sensors. (NOV/DEC-2012)

24.Explain the methods of measuring smoke density in thermal power plant with

a conceptual diagram. (NOV/DEC-2012)

ANALYZERS IN POWER PLANTS

Unit – 3

Part –A Questions

1. What should be the temperature of exit flue gas into the atmosphere and

why? (AU/Dec- 2007)

1.photographic region

2.very near IR region(overtone region)

3.near IR region(vibration rotation region)

4.far IR region(rotation region)

2. Where is pH measurement adopted in power plants? and how? (AU/Dec-

2007)

Thermal conductivity detector

Flame ionization detector

Thermionic emission detector

Electron capture detector

Flame photometer detector

Photo ionization detector

Electrolytic conduction type of detection

3. What does HMPA stand for in a chromatographic analyzer? (AU/Dec-

2006) (AU/May- 2008)

The column acts as the heart of a gas chromatography, where the fundamental

Process of separation takes place. Its action is based on the fact that when a sample of gas

or vapour is introduced into the column, it spreads by molecular diffusion to give a

concentration profile. As the sample moves through the column, additional spreading

takes place. But, the band maintains the general shape, which is detected and recorded as

a chromatographic peak.

4. What is the pH value of pure water? It is acidic or basic? (AU/Dec- 2006)

Chromatography is defined as the physical and chemical method of separation

between various components of a mixture into pure fractions or bands of each component.

5. Specify the sensors used for the measurement of oxygen in flue gas.

(AU/Dec- 2007)

Pyrolysis is an accepted method of handling solid samples. It extends gas

chromatographic analysis to compounds such as rubber, soil, textiles, coals,

resins, polymers, paint films etc. The method lends itself to studies on heat

stability and thermal decomposition. It is also called as controlled thermal

fragmentation.

6. Mention the principle of ionization smoke detectors. (AU/Dec- 2008)

When a gas or vapour comes in contact with an adsorbent, certain amount of it get

adsorbed on the solid surface. This takes place according to a phenomenon called

Langmuir phenomenon given by

X/m = k1c+k2c

Where,

k1,k2- constants

x - mass of gas or vapour adsorbed

m- mass of adsorbent

c - vapour concentration in gas phase

7. List the functions of equipments in ‘gas loop’. (AU/Jun- 2006)

Good accuracy and precision

High sensitivity

Apparatus cost is cheaper than liquid chromatography

Shorter time of analysis

8. What is the common pollution monitoring system in coal fired plants.

(AU/Jun- 2006)

If the vapour or gas comes in contact with a liquid, a fixed amount of it gets

dissolved in the liquid. This takes place according to Henry’ s law is given by

x /m =kc

Where,

m - mass of liquid used

c- vapour concentration in the gas phase

x- mass of gas

k - constant .

9. What is the need of fuel analysis in coal power plant? (AU/Dec- 2008)

Good accuracy and precision

High sensitivity

Apparatus cost is cheaper than liquid chromatography

Shorter time of analysis

Longer life of the instrument

10. Mention the principle used in oxygen analysis by physical methods.

(AU/Dec- 2008)

Sample injection system

Chromatographic column

Thermostat

Detector

Recorder

11. Why flue gas analysis is used in power plants? (AU/Jun- 2006)

o It should be very cheap

o It should have high thermal conductivity

o It should be inert

o The carrier gas should be selected according to the type of detector used.

12.Name the two corrosion accelerators in feed water? How can they be

detected and measurement? (AU/Jun- 2006)

Its action is based on the fact that when a sample of gas or vapour is

introduced into the column, it spreads by molecular diffusion to give a

concentration profile. As the sample moves through the column, additional

spreading takes place.

13. What is gas thermometer? (AU/May- 2008) (AU/Jun- 2007)

Good sensitivity

Better selectivity

The detector must be able to operate in the presence of background signal

The response time of the detector must be compactable with chromatography.

14.Why flue gas has to be measured?

The complete combustion of fuel and the analysis of flue gas to find it out is very

important thing in thermal power stations. The amount of heat developed when a fuel is

burnt depends upon the completeness of combustion. The indication of incomplete

combustion can be obtained by detection of carbon monoxide in flue gas.

15. What is the principle of Thermal Conductivity analyzer?(AU/Nov-2009)

It works on the principle that thermal conductivity of the gases is compared with the

reference gas. It consists of chambers forming a Wheatstone bridge the change in thermal

conductivity changes the resistance of the one arm of the Wheatstone bridge. The change

in resistance causes unbalance voltage. The voltage across the diagonal is the proportional

to the gas being analyzed.

16. What is the principle of steam purity meter?(AU/Jun-2010)

Sodium flame photometer is used to measure the steam purity. The sample is mixed with

the gas at controlled pressure and then it is ignited to burn wit broad flame. The light from

the flame is collected and focused on a photocell. The intensity of the emitted light is

proportional to the sodium content in the sample.

17. What is the principle of paramagnetic analyzer

The instrument makes use of the magnetic properties of gases for its operation. Gases that

are paramagnetic seek the strongest part of the field. Oxygen is strongly para magnetic.

Paramagnetic susceptibility decreases as oxygen becomes nitric oxide and nitrogen oxide

in that order. Where the properties of the carrier gas do not vary within too wide limits and

the gas mixture does not contain appreciable amount of nitric oxide. This magnetic

phenomenon can be used in determination of percentage of oxygen to a high degree of

accuracy.

18. What is the principle of chromatography

Chromatography is a physical measurement method which allows the continuous

measurement of the amounts of each constituent in a complex vapour or gas mixture. It is

the method which physically separates and quantitatively identifies two or more

components of a mixture.

19. What is the effect of variation of feed water PH?

Corrosion resulting from low PH will lead to pitting and eventual failure of tubes. A

high PH will lead to unwanted precipitation of scale forming components.

20. What is the effect of high electrical conductivity in boiler water?

High electrical conductivity in boiler water is indicative of the presence of

considerable solids. These results in foaming in the drums excessive carry over and

scaling of super heater tubes and turbine blades.

21. What is fuel analyzer?

For a fuel composition CO2 record can be related to total air and an index of

combustion conditions is obtained. Where the carbon hydrogen ratio of a fuel varies or

the percentage of fuels in a multi fuel installation changes the required CO2 at each

condition must be supplied from the operators knowledge.

22. What are the different types of chromatography?

Gas chromatography

i) Gas/ liquid (Partition) ii) Gas /solid (Adsorption)

Liquid Chromatography

Paper - Liquid / liquid (Partition)

Column - Liquid/Solid (Adsorption)

Thin layer - Gel permeation

Ion Exchange

23. What is the different section of gas chromatography?

Analysis section: It consists of valves, columns, detectors etc.

Control section: It consists of programmer, recorder, stream selector, peak-picker memory

unit and other auxiliary units.

24. What are the different methods of gas analysis?

Paramagnetic oxygen analyzers, Thermal conductivity analyzer, Infrared absorption

analyzers Selective light absorption, Electrical conductivity, Depolarization

25. What are the limitations of liquid chromatography?

The choice correct column/solvent combination for a given separation is both time

Consuming and costly

The life span for liquid chromatography column (dependent on many variables) is

of

The order of 800 injections

The minor amount of impurities in the process accumulate on the column and

Change its characteristics and thus affect the analysis.

The accuracy is +1% but its sensitivity is less.

Lack of universal detector and stable one

Availability of reliable control valves to operate at high pressures and resistant to

the effect of common organic solvent poses some problems.

16. What are the limitations of gas chromatography?

The efficiency depends on the size, composition and mode of injection of the

sample ,

type and rate of flow carrier column length, area and packing material column

temperature.

Analyzer housing should be suitably designed for hazardous areas, provide a

temperature

controlled enclosure and provide protection against physical abuse.

General precautions are to be made to achieve sensitivity.

17. Define PH

The important property of aqueous solution is their acidity or alkalinity. Acidity or

Alkalinity of an aqueous solution can be expressed in terms of hydrogen ion or

Hydroxyl ion concentration. Hydrogen ion concentration in terms of hydrogen ion

Exponent pH which is logarithm of the reciprocal of the Hydrogen ion concentration

and mathematically expressed as pH= -log10[H+] = log 1/[H+].

18. Why we need pollution monitoring instruments?

It is necessary to monitor changes taking place in the quality of the environment

for initiating efforts to control it. Pollution monitoring is thus complex task which

involves systematic collection and evaluation of physical, chemical, biological, and

related information pertaining to environmental quality and effluent discharges.

19. How the hydrocarbon enter into the atmosphere?

The hydrocarbon enter into the atmosphere from variety of sources like

Petroleum refining process

Incomplete combustion of organic fuels

Evaporation of fuels and solvents

Gasoline is the major source of their emission from IC engine since they exhaust unburned

and partially burnt hydrocarbon. Methane is the major component of hydrocarbon

emission.

20. Why do we need to analyze oxygen content in flue gas?

The absence of O2 in flue gas increase the combustion rate. Hence heat transfer rate and

combustion efficiency also high .

21. What do you mean by deaerated water?

Before the water is feed into the boiler the entrained of dissolved gases such as carbon

dioxide

and oxygen should be eliminated. Otherwise corrode the heat exchangers and boiler tubes.

22. What is the indication of incomplete combustion in boiler?

The indication of incomplete combustion in boiler is the large amount of CO present in

the flue gas and it will reduce the heat.

23. How the carbon monoxide emitted into the atmosphere?

The carbon monoxide emitted into the atmosphere due to incomplete oxidation of fission

fuels takes place. Automatic exhaust and deep mining operation

23. Name any two instruments to find CO in flue gas?

Non-dispersive infrared analyzer. Gas chromatography

24.Write advantages of grating monochromators. (2012)

The main goal of a monochromator is to separate and transmit a narrow portion of the

optical signal chosen from a wider range of wavelengths available at the input.. In the

simplest case the monochromator is composed from two slits (entrance and exit) and a

dispersion element (prism or diffraction grating). In both these elements, one takes

advantage of the dependence of the refraction angle (prism) or the reflection angle

(grating) on the radiation wavelength. In the case of prism, the larger the photon energy

(shorter wavelength) the smaller is the refraction angle. The main goal of the entrance slit

is to define the geometric properties of the investigated irradiation.

25.what is meant by pyrolysis? (2012)

Pyrolysis is a thermo chemical decomposition of organic material at elevated temperatures

in the absence of oxygen (or any halogen). It involves the simultaneous change of chemical

composition and physical phase, and is irreversible. The word is coined from the Greek-

derived elements pyro "fire" and lysis "separating"

.

Part –B Questions

1. Name the important instruments used in pollution monitoring. Explain any one

type in detail. (AU/Dec- 2007) (AU/Jun- 2007) (AU/Jun- 2008)

2. Give a descriptive note on chromatography and its role in power plants.

(AU/Dec- 2007)

3. Write short notes on fuel analyzer and its significance. (AU/Dec- 2007)

4. Write short notes on analysis of impurities in feed water and water treatment.

(AU/Dec- 2007)

5. Why is flue gas oxygen analysis performed and what are the methods adopted?

Explain the control loop where % oxygen is used as individual control index.

(AU/Dec- 2006)

6. Explain with a neat sketch a chromatography apparatus and its application.

(AU/Dec- 2006) (AU/Dec- 2008) (AU/May- 2008)

7. What are dust monitors? And explain with neat sketch. (AU/May- 2008)

(AU/Dec- 2006)

8. List the various parameters to be monitor in feed water. Also explain the

method of measuring pH value and dissolved oxygen content. (AU/Dec- 2008)

9. Write short notes on pH meter and fuel analyzer. (AU/Jun- 2006)

10. Describe in details about the flue gas oxygen analyzer. (AU/Jun- 2006)

(AU/May- 2008) (AU/Jun- 2008) (AU/Jun- 2007)

11. Explain the working of Katharometer dissolved oxygen meter.

(AU/May- 2008) (AU/Jun- 2007)

12. What are the impurities in feed water and steam? How can their presence be

detected? Explain the schemes in short. (AU/May- 2008)

13. With a neat sketch explain the ever clean window. Explain how it is useful.

(AU/May- 2008)

14. Define pH. What should be the pH of the pure water? Describe a method to

measure pH.(NOV/DEC-2012)

15.List the various parameters to be monitored in feed water. Also explain the

methods of measuring dissolved oxygen content. (NOV/DEC-2012)

CONTROL LOOPS IN BOILER

Unit – 4

Part – A Question

1. Define stoichoimeteric ratio. (AU/Dec- 2007, AU/Dec- 2008)

The path taken by the roots of the open loop transfer function when the loop gain

is varied from 0 to α are called root loci.

2. What is the function of deaerator? (AU/Dec- 2007)

The function of deaerator is that, the hygroscopic material absorbs humidity and

starts dissociating. The dissociation will depend on the absorption of moisture and

will be measured by the change in the resistance between the two wires. The

accuracy of this instrument is quite good and the response time is with in 3 to 5

min.

3. State the role of attemperators. (AU/Dec- 2007) (AU/Dec- 2008)

The main root locus technique is used for stability analysis.

Using root locus technique the range of values of K, for as table system can be

determined.

4. Which is the predominant factor in setting of automatic controllers for

optimum combustion efficiency? (AU/Dec- 2006)

A system consists of a number of components connected together to perform a

specific function. In a system when the output quantity is controlled by varying

the input quantity then the system is called control system.

5. What is TT firing? (AU/Dec- 2006)

The control system in which the output quantity has no effect upon the input

quantity are called open loop control system. This means that the output is not

feedback to the input for correction.

6. What does DCS mean? (AU/Dec- 2006)

The control system in which the output has an effect upon the input quantity

so as to maintain the desired output value are called closed loop control

system.

7. List the parameter to be measured in Deaeartor control. (AU/Dec- 2008)

Liquid-liquid chromatography

Liquid-solid chromatography

Ion exchange chromatography or Bonded phase chromatography

Exclusion chromatography

8.Which are the methods of measurement of combustion air flow? (AU/Jun- 2006)

The control system in which the output has an effect upon the input quantity so as to

maintain the desired output value are called closed loop control system. The

components of feedback control system are plant, feedback path elements, error

detector and controller.

9. Where are interlocks employed in boiler operation? Why? (AU/Jun- 2006)

(AU/May- 2008)

The T.F of a system is defined as the ratio of the laplace transform of output to laplace

transform of input with zero initial conditions.

10.What is stoichoimetric condition of combustion in fuel? (AU/Jun- 2007)

A block diagram of a system is a pictorial representation of the functions performed by

each component of the system and shows the flow of signals. The basic elements of

block diagram a raw block, branch point and summing point.

11.What is induced draft? (AU/Jun- 2007) (AU/Dec- 2008)

The servomechanism is a feedback control system in which the output is mechanical

position (or time derivatives of position velocity and acceleration,).The order of a

system is the order of the differential equation governing the system. The order of the

system can be obtained from the transfer function of the given system.

12.What is deaerator? (AU/Jun- 2007) (AU/Dec- 2008)

o Inaccurate

o Simple and economical

o The changes in output due to external disturbance are not corrected

o They are generally stable.

13.List the parameter to be monitored in Deaerator control. (AU/Dec- 2008)

Being non destructive ,the column effulent can be passed through a

TCD and then into a second detector

The sensitivity is 0.3 ng/ml .

The linearty is between 104 to 105

It is particularly suitable for fraction correction and

preparative gas chromatography .

14.What is tracking control mode of boiler systems? (AU/Jun- 2006)

The control system in which the output quantity has no effect upon the input quantity are

called open loop control system. This means that the output is not feedback to the input for

correction.

15. Why monitoring of shell temperature is so important?(AU/Nov-2009)

The boiler is fitted with various mounting and accessories. The hot water and steam

rise up through the uptake header into the boiler shell where steam separates from the

water and collects in steam space. Variations in shell temp. Affect the production of steam.

16. Where is the steam pressure measured?(AU/Jun-2010)

It is measured at the drum in the main stream header, and frequently in turbine throttle

17. What is the necessity of steam temperature control?

It is used to obtain a constant superheat temperature at all boiler loads; the Primary benefit

is to improve the economy conversion of heat to mechanical power.

18. What is the effect of high electrical conductivity in boiler water?

It is an indicative of the presence of considerable solids. These result in foaming in drums

excessive carry over and scaling of super heater tubes and turbine blades.

19. What is the difference between forced draft and induced draft fans?

A fan or air blower that takes suction from the atmosphere and forces combustion air

through the system is called forced draft fan. A fan at the end of the boiler flow system

path that takes its suction from the boiler flue gas stream and discharges the flue gas to the

stack is called induced draft fan.

20. What is reheat control?

The reheat consists of gas bypass for its primary section and spray water injection between

the primary and final reheat section. When the gas bypass dampers closes. Maximum heat

transfer to reheat primary section takes place to boost the reheat temperature particularly at

low loads. The spray water injection is used to balance this heating effect by tending to

cool the steam that is to buck the reheat temperature

21. What is ratio control?

Ratio control consists of a feedback controller whose set pt. is in direct proportional to an

uncontrolled variable. If the load falls suddenly there is a temporary rise in steam pressure

because of the fixed relationship between fuel flow and airflow, there is a resultant

reduction in fuel input.

22. What is the necessity of superheated steam flow measurements?

Regulating firing rate may depend on steam pressure. In some installations a constant

stream flow may be required for one or more boilers in combination, while other boilers

connected to the same header are used for controlling steam pressure.

23. What is furnace implosion?

A hazard to boiler that was rarely experienced is furnace implosion. Under certain

conditions, the negative pressure on the walls of the furnace, boiler and ductwork can

create forces great enough that these walls cave inward, doing considerable damage and

extensive unit outrage. This hazard is usually experienced only on electric utility boilers.

24. What is furnace draft control?

The simplest form of the furnace draft control loop uses a simple feedback control loop. In

this case the control of airflow is usually assigned to the forced draft with the furnace draft

control regulating the level of induced draft. it is most desirable to measure airflow on the

forced draft side of the furnace. Assigning airflow control to forced draft tends to reduce

interaction between the airflow and the furnace draft loops. The airflow capacity is

changed by modulating the forced draft. The resulting change in furnace draft feeds back

to the controller ,causing a series change to the induced draft.

25. What is desuperheater?

To control the temp. of steam a desuperheater is used. Some quantity of cold water is

injected into or around the pipe carrying the steam. This causes the evaporation of water so

injected and thus the temp. Of steam is lowered.

26. What is deaeration?

Before the water is put into the boiler, entrained or dissolved gases such as CO2 and O2

Should be eliminated. Eliminating the entrained or dissolved gases before they can enter

the boiler is called deaeration and is done by a deaerating heater.

27. What is attemperator?

Attemperator is shell and tube heat exchanger and is used to control the steam temp.

Steam is cooled or to remove a variable amount of the heat in heat exchanger.

28. What are the types of feed water control?

Single element, two elements, three elements

29. What are the waterside control mechanisms in steam temperature control?

(i) Spray mechanism

(ii) Steam temp control using a control valve to divert of steam

(iii) Use of shell and tube heat exchanger in the saturated steam line between the boiler

and the super heater.

30. What are the types of super heater?

(i) Convective super heater

(ii) Radiant super heater

According to location (i) over deck (ii) inter deck (iii) inter tube (iv) interbank.

31. What are the requirements to be considered for firing due to load change?

When considering changes of steam pressure, the steam pressure does not change

immediately on load change or in proportional to load change. so pressure drop cannot

resorted without over firing for the load being carried. The reverse occurs on a rise in

pressure, when boiler must be under fired so that the excess energy is used for steam

production. Therefore, the time constant of boiler is large when compared with other

possibly short time constants of a control system. This must be taken into consideration

when setting up an automatic boiler control system.

32. What are the methods used for steam temperature control?

i) heat exchanger type deheater, (ii) spray type deheater, iii) Tilting burners or burner

pattern, (iv) super heater gas by pass control and fire control mechanism.

33. What are the methods used for drum level measurement?

(i)sight gage glass technique(ii) drum level transmitter(iii) probe type(iv)tube expansion

type.

34. What are the functions of super heater and reheater?

The steam produced in the boiler is nearly saturated. This steam as such should not be

used in the turbine because the dryness fraction of the steam leaving boiler will be low.

This results in presence of moisture, which causes corrosion of turbine blades.

35. What are the feed water control objectives?

*control the drum level to a set pt.

*minimize the interaction with the combustion control system.

*make smooth changes in the boiler water inventory as boiler load changes

* Properly balance the boiler steam output with feed water input.

36. What are the effects of feed water pressure variation?

The performance is seriously degraded by variations in feed water pressure. Such feed

water pressure variations change the relationship between steam flow and feed water flow.

Boiler drum level is then forced to develop an offset from the set pt. in order to bring the

steam flow and feed water flow into unbalance.

37. What are the effects of feed water pressure variation in drum level control?

The desired control objective cannot be obtained because it has serious draw backs if

the feed water control valve pressure is differential and thus the control valve flow

characteristics are not always same. The performance is seriously degraded by variations in

feed water pressure. Such feed water pressure change the relationship between the steam

flow and feed water flow

38. What are the drawbacks of single element feed water control?

(i) If the controller were proportional, a greater drum level offset would occur as boiler

load is changed.

(ii) The basic reason for drum level variations around the set pt. represents a specific

quantity of water over the entire boiler range.

39.What is the effect of excess air in combustion? (Nov-2012)

Incorrect amount of air in fuel combustion accounts for the largest losses in combustion

systems. This environmental and health threat of stack gas is one more reason to reduce

energy consumption per unit of product output.

40. List of various type of draft control in furnace of boiler. (Nov-2012)

Natural Draft, Mechanical Draft, Balanced Draft, Induced Draft, Forced Draft.

Part B Questions

1. Define draft. What are the types of draft established in boiler system, where and

how? (AU / Dec –2007) (AU / May –2008)

2. Explain the furnace draft control systems (AU / Dec–2007) (AU / Dec –2006)

3. Describe the features adopted in main steam, reheat steam and super heater

temperature control. (AU / Dec –2007) (AU / May –2006) (AU / May –2008)

4. Explain interlocks in boiler. (AU / Dec –2006) (AU / Dec –2008) (AU / Jun –2006)

5. With a SAMA diagram, explain a simple feedback control in a process. Assume a

proportional plus integral control function. (AU / Dec –2006) (AU / May–2008)

6. With a block diagram, describe the function of a distributed control system of a

power plant. (AU / Dec –2008) (AU / May –2006)

7. What is meant by the term oxygen limit control in boiler operation? How it is

performed? (AU / Dec –2008)

8. Explain with SAMA or ISA diagrams three- element drum level control. (AU /

May –2008)

9. What are the fireside and waterside control mechanisms for control steam

temperature in boilers? (AU / May –2008) (AU / Jun –2007)

10. Write notes on use of attemperators in system temperature control. (AU / Jun –

2006)

11. Discuss about air/fuel ratio control. (AU / Jun –2006)

12. Draw the diagram of five element feed water control system and explain its

working. (AU / May –2008)

13. What is meant by the term oxygen trim control in boiler? Also explain the method

of controlling the combustion by oxygen trim control.(Nov/Dec-2012)

14. Explain the methods of controlling feed water in boiler by three element control

method. Also specify the limitation of feed water control by two element control

methods.( Nov/Dec-2012)

TURBINE-MONITORING AND CONTROL

Unit – 5

Part – A Questions

1. How is vibration is turbine system monitored? Why is vibration control given

importance? (AU / Dec–2007) (AU / May –2008)

The manometer is the simplest measuring instrument used for measuring

low pressure ranges by balancing the pressure against the weight of a column of

liquid. The action of all manometers depends on the effect of pressure exerted by

a fluid at a depth.

2. List the uses of accelerometer. (AU / Dec–2006) (AU / May –2008)

Pressure measurement helps in determining the liquid level in tanks and

containers. Pressure measurement helps in determining the density of

liquids. Used in many flow meters. Eg. Venturi meter, Orifice meter

etc.,

Pressure measurement is also required in day-to-day situations such as

maintaining optimal pressure in tubes of vehicles tyres.

3. Define the term vibration displacement. (AU / Dec–2008)

The bellows element is cylindrical in shape and the wall of this cylinder

is thin and corrugated. The wall of this bellow is about 0.1mm thick and is

made of some springy material such as stainless steel, brass or phosphor

bronze. This bellows element is open at one end to receive the applied pressure

and is closed at its other end. This other end is usually attached with a rod. In

many cases a spring is placed inside the bellows to regain its original shape

when the applied pressure is relieved.

4. What are the digital methods of speed measurement? (AU / Dec–2008)

Ionization is the process of knocking off an electron from an atom and thus

producing a free electron and a positively charged ion. The laboratory standard of

pressure is a dead weight tester and it is very often used to calibrate Bourdon

gauges.

5. Define critical pressure in water steam cycle. (AU / Jun–2006)

Water steam cycle operates by taking in a sample volume of gas from a vacuum

chamber, and then compressing it by tilting, and infilling with mercury. The pressure in

this smaller volume is then measured by a mercury manometer, and then knowing the

compression ratio, the pressure of the original vacuum can be determined.

6. Define thermal efficiency. What is its value for a coal fixed power plant? (AU /

Jun–2006)

Pirani gauge

Thermocouple type conductivity gauge

Ionization gauge

7. Mention the various cooling methods for Turbo Generator. (AU / Dec–2008)

The most common fluids used in manometers are water, red oil, and

mercury. To minimize the effects of freezing and evaporation, kerosene or anti-

freeze may be used.

8. What are the transducers used for shaft vibration measurement? (AU / Dec–

2008)

It follows Boyle’s law, which is at constant temperature, the ratio of pressure

of two gauges is equal to the ratio of two densities.

9. How is turbine casing movement measured? (AU / Jun–2006)

A system consists of a number of components connected together to

perform a specific function. In a system when the output quantity is controlled by

varying the input quantity then the system is called control system.

10. Mention the forms of cooling apparatus employed in power plants. (AU / Jun–

2006)

Float type level indicator

Displacer type detector

Sight glass type.

11. What are steam and water turbines? (AU / May–2008)

Pressure measurement helps in determining the liquid level in tanks and

containers. Pressure measurement helps in determining the density of liquids.

Used in many flow meters. Eg. Venturi meter, Orifice meter etc.,

12. Which sensor is used for the measurement of lubrication oil temperature? (AU

/ May–2008)

RTD

Thermocouple

Both sensors are used to measure the temperature of the lubricating oil.

13. Enlist the various components of cooling system(AU/Jun-2009)

i) Condenser, ii) Cooling towers, iii) Pumps and pipes

14. How steam temperature affects efficiency of boiler?(AU/Jun-2009)

The boiler steam temp is also affected by the cleanliness factor, the fuel being

fired. The imbalance between fuel input and steam output and excess combustion

air. Variation in steam temperature causes latent heat loss of water vapour in the

flue gas. Therefore affects boiler efficiency.

15.How to measure speed of turbine?(AU/Jun-2010)

Vibrating reed tachometer, Stroboscope, clock type tachometer and revolution

counter are various instruments used for measuring speed.

16.Why do we need to measure vibration of turbine blades?

The balancing of large rotating steam turbine is a critical component in ensuring

the reliable operation of the plant. Most large steam turbines have sensors

installed to measure the movement of the shaft in their bearing.

17. Name the sensors used in measuring vibration?

i) Vibration pickups

ii) Vibrometers

iii) Electrical vibration pickups

iv) Mechano-electrical absolute vibration

18. What do you mean by high pressure and low pressure turbine?

In typical large power stations the steam turbines are split into three separate stages

the first being the high pressure, the second the intermediate pressure and third the

low pressure. After the steam has passed through HP stage it is returned to the

boiler to be reheated to its original temperature. The reheated steam then passes

through the IP stages and finally to the LP stage of the turbine.

19. What is the use of auxiliary steam?

Auxiliary steam extracted from turbine at various points (ie extracted pressure) can

be used for cogeneration.

20. What are turbine losses?

Steam turbine losses include exhaust, mechanical, generator, radiaton

Mechanical losses include bearing losses, oil pump losses and generator

losses.

Generator losses include electrical and mechanical losses.

Exhaust losses include the kinetic energy of the steam as it leaves the last

stage and pressure drop from the exit of last stage to the condenser stage.

21. List the methods to control the steam pressure.

(i) On-off control (ii) proportional plus integral feedback control (iii) feed forward

plus feedback.

22. Why do we need to control lubricant oil?

High pressure oil is injected into the bearing to provide lubrication. The oil is

carefully filtered to remove solid particles. Specially designed centrifuges remove

any water from the oil. The centrifuges were approaching an expensive overhaul;

high speed centrifuges can damage the additive package of oil.

23. Define turbine efficiency.

It is defined as the ratio of net output of the turbine to the power that should be

ideally produced by the turbine. Network output of the turbine is always less than

ideal output.

24. How superheat and reheat steam temperature is measured?

This is critical from the standpoint of safety and efficiency. It is commonly the

source of regulation for final steam temperature control to prevent damage to

turbine. These temperature are commonly measured by electrical instruments which

employ resistance elements or thermocouples and electronic amplification.

25. What are the advantages and disadvantages of wet cooling?

i) This type of cooling system is used is therefore heavily influenced by the location

of the plant and on the

availability (sea, large rivers, and lakes) of water suitable for cooling purposes.

ii) High efficiency

iii) One of the problem with wet towers is that in cold and humid climates the

towers plume can create fog.

26. What are the advantages and disadvantages of dry cooling?

Dry cooing systems are used where there is insufficient water or where the

water is too expensive to be used in an evaporative system.

Dry cooing systems are least used systems as they a much higher capital

cost, higher operating temperature and lower efficiency than wet cooling.

27. What is the use of alarm and annunciators?(AU/Nov-2012)

An alarm in which interruption of electric current to a relay, caused, for example,

by the breaking of a metallic tape placed at an entrance to a building, de energizes

the relay and causes the relay contacts to operate the alarm indicator. Also known

as intrusion alarm. An annunciator indicative of the current status of the application

is then provided, if required. A menu screen with a listing of all items (e.g., missed

calls, recorded voice memos, recorded messages, or data calls) may be displayed

when requested and additional information for a selected item may also be provided

if requested. The annunciator is cleared if all items are cleared.

28.Why hydrogen cooling is the preferred method of cooling for large size

alternators? (AU/Nov-2012)

A hydrogen-cooled turbo generator is a turbo generator with gaseous hydrogen as a

coolant. Hydrogen-cooled turbo generators are designed to provide a low-drag atmosphere

and cooling for single-shaft and combined-cycle applications in combination with steam

turbines. Because of the high thermal conductivity and other favourable properties of

hydrogen gas this is the most common type in its field today.

Part – B Questions

1. Why should the pressure of steam be raised in the boiler and turbine. (AU / Dec–

2007)

2. Discuss in brief on the turbine – boiler monitoring and control schemes. (AU /

Dec–2007)

3. Write in brief about the cooling system. (AU / Dec–2007)

4. Write in brief about the shell temperature monitoring and control. (AU/Dec–2006)

(AU / Dec–2007)

5. Explain with suitable diagrams two non contact type speed measurement methods.

(AU / Dec–2006)

6. How is steam temperature monitored in power plant? (AU / Dec–2006)

7. Why does steam pressure change and how it is controlled in steam plant? (AU /

Dec–2006) (AU / Jun–2006)

8. List the various parameters need for turbine supervisory control system. Also

explain the technique for the measurements of the parameters. (AU / Dec–2008)

9. Why is vibration measurements essential in turbine control? Also explain the

method vibration measurement in steam turbine. (AU / May–2008) (AU / Dec–

2008)

10. Explain the lubricant oil temperature control scheme in brief. (AU / Jun–2006)

11. How are speed and vibration monitored in power plants. (AU / Jun–2007)

12. Explain various methods of measuring steam pressure. (AU / Jun–2007)

13. Discuss the various parameter to be monitored for smooth running of turbine? Also

explain the operation of differential expansion detector. (AU / Dec–2008)

14. Why temperature needs to be measured at various stages of turbine? Also mention

the method of monitoring and control of temperature in turbine. (AU / Dec–2008)

15. Write notes on steam pressure control. (AU / Jun–2006)

16. Write short notes on steam temperature and pressure monitoring in power plants.

(AU / May–2008)

17. Discuss the need of shell temperature monitoring and control. Also explain the

methods of shell temperature measurement.(Nov/Dec 2012)

18. List the various parameters needed for turbine supervisory control system. Also

explain the techniques for vibration measurement.(Nov/Dec-2012)