Power Plant Interview Questions & Answers

We wrote a Power Plant Interview Questions & Answers post that covers the fundamentals of power plant operation.

Power Plant Interview Questions & Answers

1. Name the four major circuits in the steam power plant.

• Coal and ash circuit
• Air and flue gas circuit
• Feedwater and steam circuit
• Cooling water circuit

2. What consists of an air and flue gas circuit?

Forced draught fan, air preheater, boiler, furnace, superheater, economizer, dust collector, induced draught fan, and chimney make up the air and flue gas circuit.

3. What consists of feed water and steam flow circuit in steam power?

Feed pump, economizer boiler drum superheater, turbine, and condenser make up the feed water and steam flow circuit.

4. What consists of a cooling water circuit and coal & ash circuit in a steam power plant?

A pump, condenser, and cooling tower make up the cooling water circuit. Coal supply, coal preparation, coal handling to the boiler furnace, ash handling, and ash storage are all part of the coal and ash circuit.

5. What is the main purpose of the reservoir?

The main aim of a reservoir is to retain water collected from catchment regions during rainy seasons and to deliver it during dry seasons.

6. What is the main purpose of the dam?

The dam’s main aim is to raise the water level and improve the hydraulic power plant’s working head.

7. Why trash rack is used?

The garbage rack is intended to keep waste out of the turbine runners, which could damage them and clog up the nozzle of the impulse turbine.

8. What is the use of a surge tank?

The surge tank is used to improve the system’s water pressure regulation. When the load on the turbine drops, the surge tank controls the water flow and feeds water when the load on the turbine increases. As a result, the surge tank prevents water hammers by controlling pressure differences caused by fast changes in water flow in the penstock.

9. What is the function of Forebay?

The forebay is regarded as a naturally occurring surge tank. It serves as temporary water storage when the plant’s load is reduced and as an initial increment when the load is increased.

10. Explain about penstock?

Penstock is the conduit that connects the surge tank to the primary mover. It’s made to resist a lot of pressure. Reinforced concrete was used to construct it. The penstock is buried in extremely cold places to prevent ice accumulation and reduce expansion joints.

11. What is the use of spill Ways?

The spillway functions similarly to a dam’s safety valve. It releases a large flood without causing damage to the dam. It keeps the reservoir at a lower level than the maximum allowable.

12. Write about prime movers?

To generate electrical energy, the prime mover converts the kinetic energy of water into mechanical energy. Prime movers in hydraulic power plants include the Pelton wheel, turbine, Francis turbine, Kaplan turbine, and Propeller turbine.

13. What are the uses of air filters and superchargers in diesel engine power plants?

The objective of an air filter is to remove dust and other suspended particles from the air. The goal of a supercharger is to boost the engine’s pressure in order to increase its power.

14. What is the use of a draft tube?

The draught tube is used to recover the kinetic energy of the water that exits the reaction turbine. It allows the reaction turbine to be installed above the tailrace.

15. What is the function of the cooling system in a Diesel power plant?

The cooling system’s purpose is to remove heat from the engine cylinder in order to maintain the cylinder temperature low and increase engine life.

16. What consists of a lubrication system in a diesel engine power plant?

Oil pumps, oil tanks, filters, coolers, and connecting pipes make up the lubrication system. Lubrication is used to reduce friction between moving parts and pipes, as well as to reduce wear and tear on moving parts.

17. What is the purpose of an intercooler in a gas turbine power plant?

Because the power required to compress the air in an isothermal process is lower, it is necessary to keep the temperature of the air as constant as feasible. As a result, air exiting the L.P. compressor is cooled by the intercooler before being delivered to the H.P. compressor.

18. Name two combined power cycles?

• Gas turbine and steam power plant in a combined cycle.
• Gas turbine and diesel power plant in a combined cycle.

19. Define turbocharging in combined gas turbine and diesel cycles?

The exhaust gas from the diesel engine is enlarged in the turbine, which is connected to a compressor that delivers compressed air to the diesel engine in the combined cycle. This boosts the output of diesel engines. Turbocharging is the term for this setup.

20. What is the main purpose of high-pressure boilers?

The high-pressure boilers are utilized to improve the plant’s efficiency and lower the cost of energy generation.

21. State important advantages of high-pressure boilers?

• Because the velocity of water through pipes is higher, the amount of scale formation is reduced.
• There is no risk of overheating because all portions of the system are heated evenly.

22. Name important high-pressure boilers?

• La Mont boiler
• Benson boiler
• Loeffler boiler
• Velox boiler.

23. Write about La Mont boiler? What is the major disadvantage of La Mont boiler?

The La Mont boiler is a high-pressure water tube boiler with forced circulation.

The production of bubbles, salt, and silt on the inner surfaces of the heating surfaces is a serious disadvantage. Heat flow and steam generation are reduced as a result.

24. Write about Benson boiler? State some important advantages of Benson boiler?

The Benson boiler is a vertical fire-tube boiler with high pressure. This boiler does not have a drum and is designed to run at 225 bar of critical pressure. There is no drum on the Benson boiler.

As a result, when compared to conventional boilers, the total weight of the Benson boiler is lowered by 20%. The installation of a Benson boiler is simple and rapid.

25. Write about the Loeffler boiler?

The accumulation of salt and silt on the inner surface of the water tubes is the main disadvantage of the La Mont boiler. It reduces heat transfer and, as a result, the capacity to generate steam.

This difficulty is overcome in a Loeffler boiler by stopping water from flowing through the boiler tubes. Outside the tubes, steam is produced.

26. Explain the Reheat cycle?

Corrosion and erosion of turbine blades occur when the dryness fraction of steam leaving the turbine is less than 0.88. Reheat is utilized to avoid this issue.

The reheat cycle involves the expansion of steam in one (or more) turbines. Steam is enlarged first in the HP turbine, then reheated. The reheated steam is injected into the LP turbine once more.

27. What are the important advantages of Reheating?

• The network done rises as a result of reheating.
• The amount of heat available increases.
• Thermodynamic efficiency improves
• Reheating enhances the turbine’s exit dryness fraction, which reduces moisture and reduces blade wear, extending the turbine’s life.

28. Name different methods of reheating?

• Gas Reheating
• Live steam reheating
• Combined gas live steam reheater.

29. Define bleeding in a steam power plant?

Assume that the turbine expands 1 kilogram of steam. Some steam (m kg) is taken before the entire amount of steam is expanded. Bleeding is the process of extracting steam from a turbine before it is exhausted. The supply water is heated with this bleed steam.

30. Explain the term Regeneration?

Steam from the turbine is used to heat the feed water during regeneration. Before exhaust, the steam is exhausted (bled) from the turbine and delivered to the regenerator (feedwater heater) to heat the feed water.

31. State some advantages of the Regeneration cycle?

• The amount of heat delivered to the boiler is lowered.
• The average temperature of heat added to the cycle is increased, increasing thermal efficiency.
• The erosion of the turbine caused by moisture is minimized due to bleeding in the turbine.

32. Name different methods used to extract steam for heating the feedwater?

• Direct contact heater
• Drain pump method
• All drains to hot well
• Cascade system

33. Define the term waste heat recovery?

Waste heat is heat that is not utilized at all and is ejected as a waste product. In most cases, waste heat comes from industry in the form of high-temperature process steam and water.

In many sectors, waste heat is also emitted with exhaust gases. This heat can be recovered and put to good use. Waste heat recovery is the name for this procedure.

34. What are the waste materials, which can be used for fuel for power generation?

• Municipal waste
• Industrial waste
• Paper waste
• Rubber waste.

35 Write about waste heat boilers?

Waste heat boilers employ waste heat in high-temperature gases emitted by diesel engines and gas turbines (or) use waste as a fuel in incineration.

For electricity generation, some boilers employ industrial filthy gases.

36. Write about fluidized bed boilers?

When a high-velocity gas passes over a packed bed of finely divided solid particles, the particles get suspended in the gas stream, transforming the packed bed into a fluidized bed. When the gas velocity is extremely high, the fluidized bed becomes turbulent, resulting in rapid particle mixing. The behavior of a mixture of solid particles and gas eventually becomes fluid. The combustion of a fuel in such a way

37. State some advantages of fluidized bed boilers?

• In the FBC system, any sort of fuel, whether solid, liquid, or gaseous, as well as residential and industrial waste, can be employed. By altering elements like size, air velocity, and feed rate, any form of flammable debris can be burned.
• Because solid mixing is exceedingly conceivable, a high heat transmission rate to the surfaces immersed in the bed is achievable.
• High efficiency of combustion.
• The solid fuel does not have to be pulverized.

38. Name the two types of coal handling?

• Out plant handling
• In-plant handling.

39. Write about our plant handling?

Out plant, handling includes the handling of coalmine to the thermal power plant. These handlings are outside the plant in the following ways.

• Transportation by sea (or) river
• Transportation by rail
• Transportation by road
• Transportation of coal by pipeline.

40. Write about inplant handling of coal?

Some mechanical handling methods are offered for smooth, easy, and better-controlled operation of huge quantities of coal inside the plant. The coal handling in plants is separated into the following groups.

• Coal unloading
• Coal preparation
• Coal transfer
• Coal storage

41. Why the preparation of coal is necessary?

The coal from the coal nines cannot be fed into the furnace directly. Before feeding coal into the furnace, it should be properly prepared. Coal passes through a variety of equipment in the coal preparation process, including 1. crushers. 2. Measurers Driers and Magnetic Separators are the third and fourth items on the list.

42. Name the different types of coal transforming equipment?

1. Belt conveyors
2. Screw conveyors
3. Bucket elevators
4. Grab bucket elevators
5. Skip hoists
6. Flight conveyors.

43. What is the use of belt conveyors?

Belt conveyors are commonly used to transport big amounts of coal across long distances. An endless belt is supported by a series of rollers at regular intervals and runs over a pair of end drums and pulleys.

44. Can you write about screw and bucket conveyors?

The 9haft of screw conveyor is fitted with an endless helicoid screw. The driving mechanism is installed on one end of the shaft, while the other end is supported by a ball bearing. The coal is moved from one end to the other while the screw is moving.

Vertical lifts are provided via bucket conveyors. In the bucket conveyor, coal is loaded at the bottom and discharged at the top.

45. Define draught, what is the use of draught in thermal power plants?

Draught is described as a minor pressure difference between the fuel bed (furnace) and outside air required to maintain a steady flow of air and discharge gases to the atmosphere through the chimney. A chimney, fan, steam jet (or) air jet (or) a combination of these can be used to create a draught.

46. Write about the classification of draught?

49. Write about the forced draught system?

The blower (forced draught fan) is situated near the grate at the bottom of the boiler with this design. By using a forced fan, air is forced into the furnace, and flue gases are forced into the chimney by using an economizer and an air preheater.

50. What are the advantages of forced draught system

• Because the fan is used to circulate cold air, it is smaller and requires less power.
• Because the air being handled is cold, there is no need for water-cooled bearings, and the pressure throughout the system is higher than atmospheric pressure, reducing air leakage into the furnace.

Also Read: What is a Hydraulic Actuator?

51. How the induced draught is working?

A blower (induced draught fan) is situated near (or) at the base of the chimney in an induced draught system. The fan draws the flue gas out of the furnace, resulting in a partial vacuum inside. As a result, ambient air is forced into the furnace to aid in the combustion of fuel. The flue gases pulled by the fan are released into the atmosphere via the chimney.

52. Why the balanced draught system is preferred to another system?

When the furnace is opened for firing in an induced draught system, cold air enters the furnace and dilates the combustion. When the furnace is opened for firing in a forced draught system, the high-pressure air will try to blow out unexpectedly, causing the furnace to stop.

As a result, in both systems, the furnace cannot be opened for firing (q) examination.

53. What is the difference between stocker firing and pulverized fuel firing?

The stocker firing method is used for firing solid coal whereas pulverized firing method is used for firing pulverized coal.

54. What are the different types of stockers?

1. Overfeed stockers

• Traveling grate stockers
• Spread stockers

2. Under feed stockers

• Single retort stocker
• Multi retort stocker

55. What is the use of pulverizer and name different types of pulverizing mills?

The pulverizer is used to pulverize the coal in order to increase surface exposure. Pulverized coal enables rapid combustion.

The different types of pulverizing mills are

1. Ball mill
2. Hammermill
3. Ball and race mill.

56. Name the two methods of pulverized fuel firing system?

1. Unit (or) direct system
2. Bin (or) central system.

57. What are the advantages of the unit (or) direct system of pulverized fuel firing?

1. The layout is simple and economical
2. It gives direct control of combustion
3. The coal transportation system is simple
4.  Maintenance cost is less

58. How the ash handling system is classified?

1. Mechanical handling system
2. Hydraulic system
3. Pneumatic system
4. Steam jet system

59. Why ash handling system is needed?

1. To empty the ash hopper from the furnace
2. To convey the ashes from the ash hopper in the furnace to a storage location.
3. To get rid of the ashes in the storage

60. Name different types of dust collectors?

1. Mechanical Dust collector

• Gravitational separators
• Baghouse dust collector

There are three types of baghouse dust collector

• Open pressure type
• Closed pressure type
• Closed suction type

2. Cyclone. Separators

3. Elector Static Precipitator (ESP)

61. What is the main purpose of chimneys?

The main purpose of chimneys is to emit flue gases at a considerable height to avoid nuisance to the surrounding people.

62. What are the different types of load that act on the chimney?

There are two types of loads acting on the chimney namely.

Its own weight, which is a single vertical force operating through the centroid, and wind pressure, which is a horizontal force acting on the centroid of the vertical projected area.

63. Name different types of chimneys?

1. Steel chimney
2. Site constructed chimney
3. Plastic chimney

64. Define forced draft and induced draft cooling towers

Forced draught cooling towers are those in which the fan is situated at the bottom of the tower and air is blasted up through the descending water by the fan.

Induced draught occurs when a fan is situated at the top of a tower and air enters through louvers on the tower’s side, is dragged up, and discharged through the fan casing.

65. What are the advantages of the induced draft cooling tower over the forced draft cooling tower?

1. The driest water is exposed to the driest air, whereas the warmest water is exposed to the most humid air.
2. Re-circulation is rarely an issue.
3. Because pump power consumption is reduced, the first cost is minimal.

66. What are the advantages of hyperbolic natural-draft cooling towers?

• Because no fans are utilized, the cost of electricity and auxiliary equipment is decreased.
• Even when there is no wind, the hyperbolic tower chimney provides its own draught.
• Hyperbolic towers avoid ground fogging and warm air recirculation.
• The building is, for the most part, self-supporting.
• 67. What are the factors that affect the evaporation of water in cooling towers?
• The relative velocity of air passing over the droplets
• The RH of air
• The direction of airflow relative to water.

68. What is the working principle of Cooling Towers?

The hot water is sprayed from the tower’s top, and the air is forced to flow from the bottom to the top. The heated water in the cooling tower is cooled by this air. A little proportion of water is vaporized by air, which cools the remaining water.

The hot air rises to the top of the tower, while the cooled water falls to the bottom and is recirculated to the condenser.

69. Name different types of cooling towers?

The cooling towers are classified as follows.

(a) According to the construction of the material

1. Timber for a small tower
2. Ferroconcrete for large capacity stations.
3. Multideck concrete towers for large steam stations
4. Metallic

(b) According to the nature of air draught

1. Atmospheric (or) Natural draught cooling system
2. Mechanical draught cooling tower.

70. How the atmospheric (or) natural draught cooling towers are classified?

In atmospheric (or) natural cooling towers, the natural air provides the required cooling without the use of fans.

This is classified into three types.

1. Natural draft spray filled towers
2. Natural draft packed type towers.’
3. Hyperbolic cooling towers.

71. How mechanical draft cooling towers are classified?

A mechanical draft cooling tower is classified into three types

1. Forced draft tower.
2. Induced draft counterflow tower
3. Induced draft crossflow tower.

72. How the dry types of cooling towers are classified?

The dry-type cooling towers are classified into two types as follows.

1. Indirect dry type (or) Heller cooling system
2. Direct dry type-cooling system

73. What are the methods to reduce the effects of particulates?

The effects of particulates can be reduced by the following methods.

• Coal cleaning
• Using improved electrostatic precipitator design
• Controlling the dust within the allowable limit. This can be done by increasing the height of the chimney thereby reducing the concentration

74. What are the equipment used for ash collection?

• Electrostatic precipitator
• Fly ash scrubbers
• Cinder catcher
• Cyclone dust collector

75. What is meant by ‘Desulphurization’ and name the methods adopted for desulphurization?

Desulphurization of fuel is the process of reducing the sulfur content in the fuel. The following methods are adopted for desulphurization.

1. Chemical treatment
2. Forth flotation
3. Magnetic separation

76. What are the methods adopted to remove’ S02 flue gases?

1. Wet scrubbing
2. Solid absorbent
3. Catalytic oxidation

77. Write about C02 recorders?

It is vital to keep the concentration of CO2 as low as feasible in thermal power plants. A continuous recording of C02 concentrations is required to do this.

The three different principles that these recorders are founded on are listed below.

• Cell for measuring thermal conductivity
• Cell for chemical absorption
• Density equilibrium

78. Name some of the automatic controlling methods for feedwater?

1. 1. Single element pilot operated system
   2. Single element self-operated system
   3. Two element pilot operated system
   4. Three element pilot operated system

79. What is the purpose of automatic, combustion c61ritrol?

The main goal of the automatic combustion control system is to keep the load on demand, prevent smoke, boost boiler house efficiency, perform routine adjustments, and provide interlocking safety measures.

80. What are the appliances known as boiler accessories?

The appliances used to increase the efficiency of the boiler are known as boiler accessories.

The important boiler accessories are

1. Economizer
2. Superheater
3. Air preheater
4. Feed pump
5. Injector

81. What are the methods adopted to remove SO2 from due gases?

1. Wet scrubbing
2. Solid absorbent
3. Catalytic oxidation

82. Write about C02 recorders?

The concentration of CO2 in thermal power plants must be kept as low as feasible.

To do so, a continuous recording of CO2 concentration is required.

The three different principles that these recorders are founded on are listed below.

• Cell for measuring thermal conductivity
• Cell for chemical absorption
• Density equilibrium

83. What is the necessity of Automatic controls for feedwater?

The electrical load on the power plant fluctuates erratically. At a steam power plant, the automatic man control successfully meets the changeable load. Because feedwater supply is dependent on plant load, automatic feedwater control is required.

84. Name some of the automatic controlling methods for feedwater?

• A single element pilot operated system
• Single element self-operated system
• Two element pilot operated system
• Three element pilot operated system

85. What is the purpose of automatic combustion control?

The primary goal of the automatic combustion control system is to maintain load adjust demand, avoid smoke, improve boiler house efficiency, perform routine adjustments, and provide interlocking safe measures.

86 What is the use of an air preheater?

The purpose of an air preheater is to transfer heat from flue gases to air before it enters the furnace for burning. Between the economizer and the chimney, it is located. By using an air preheater, the plant’s overall efficiency can be boosted by 10%.

87. Write about boiler mountings?

The devices are used for efficient operation, proper maintenance, and safe operation of boiler mountings.

The different boiler mountings are

1. Water gauge (or) water level indicator
2. Pressure gauge (or) steam gauge
3. Safety valves
4. Fusible plug
5. Stop valve
6. Blow off cock
7. Feed check valve.

88. What is meant by boiler trial?

Steam is produced in boilers under specific feed water conditions and remains as steam while a specified amount of fuel is burned.

Some experiments are carried out to evaluate the performance of boilers by operating the boiler for a set period of time and documenting the results. Boiler trial is the term for this technique.

89. State the objective of the boiler trial?

• To determine the boiler’s thermal efficiency when operating at a specific pressure.
• To check the boiler’s operation, a heat balance sheet must be created.

90. Define demand factor?

• The ratio of maximum demand to connected load is known as the demand factor.
• The sum of the kW ratings of equipment installed in the consumer’s premises is referred to as connected load.
• The maximum load that a consumer can use at any given time is known as maximum demand.

Also Read: What is an Orifice Meter?

91. Define load curve?

The load curve is a graph that shows the relationship between load in kW and time in hours. It depicts the load variation at the power facility. The energy generated in a given period is represented by the area under the load curve.

92. Define load factor?

The ratio of average load to peak load (or maximum demand) is known as the load factor.

93. What includes fixed cost?

Fixed cost includes the following cost.

1. Cost of land
2. Cost of building
3. Cost of equipment
4. Cost of installation
5.  Interest
6. Depreciation cost
7. Insurance
8. Management cost

94. What includes operating costs?

Operating cost includes the following cost.

1. Cost of fuel
2. Cost of operating labor,
3. Cost of maintenance labor and materials.
4. Cost of supplier like

Water for feeding boilers, for the condenser, and for general use.

• Lubrication oil and, grease.
• Water treatment chemicals.

95. What is the need for depreciation cost?

The amount set aside each year from the plant’s profits to cover depreciation caused by the age of service, wear and tear of the machinery and equipment is known as depreciation cost. Every year, the depreciation amount received aids in the replacement and repair of equipment.

96. Write about atomic numbers?

Protons and neutrons make up the nucleus. An atomic number is a number of protons in a certain atom (Z). H has an atomic number of 1 and He has an atomic number of 2.

97. Write about isotopes of an element?

• Some elements have the same number of protons but varying numbers of neutrons in their nuclei.
• As a result, whereas these elements have the same atomic number, their mass numbers are different.
• Isotopes of an element are types of atoms that have the same atomic number – the same number of protons – and chemical characteristics but distinct mass numbers due to differing quantities of neutrons.

98. What are the requirements to sustain the fission process?

• The energy of the blasted neutrons must be adequate to initiate fission.
• The number of neutrons produced must be sufficient to maintain the fission rate.
• The fission process must produce energy in order to work.
• Controlling the fission process is essential.

99. Define the multiplication factor of a fission process.

k =number of neutrons of any one generation/number of neutrons of the immediately preceding generation.

100. Define fertile materials and breeding in reactors

Although some materials, such as U235 and Th232, are not fissile, they can be made fissile by bombarding them with neutrons. Fertile materials are those that are rich in nutrients.

Breeding is the process of transforming more fertile material into fissile material in a reaction.

101. What are the desirable properties of a good moderator?

• It has to be the lightest possible. It needs to slow the neutron down as quickly as feasible.
• It must be corrosion-resistant.
• It must be easily machinable.
• It must have a high melting point and strong conductivity.

102. What are the desirable properties of a coolant?

• • It should not absorb a neutron
  • Have high chemical and radiation stability
  • Non-corrosive
  • Have a high boiling point
  • Non-toxic

103. List a few different types of reactors.

Fast reactors, thermal reactors, natural fuel reactors, enriched uranium reactors, water-moderated reactors, heavy water-moderated reactors, graphite-moderated reactors, gas-cooled reactors, and sodium-cooled reactors are some of the several types of reactors.

104. What are the advantages of using CO2 as a coolant?

• The structural materials do not react chemically with gases.
• For a given pressure, gas may reach any temperature.
• They don’t take in neutrons.
• The reactivity is unaffected by gas leaking.
• The best neutron economy is provided by the gas coolant.

105. What are the advantages of breeder reactors?

• It gives high power density than any other reactor
• High breeding is possible
• High burn-up of fuel is achievable
• The operation of the reactor is not limited by Xe poisoning.

106. What are the demerits of the breeder reactor?

• Highly enriched fuel is required
• Control is difficult and expensive
• Safety must be provided against meltdown
• Handling of sodium is a major problem

107. What are the advantages of Sodium in fast-breeder reactors?

• The cross-sectional area of sodium absorption is very small.
• It has excellent heat transmission qualities at both high and low temperatures and pressures.
• It doesn’t react with any of the primary circuit’s structural materials.

108. Name the different types of MHD generators

• • Open cycle MHD
  • Closed cycle MHD
  • Closed cycle MHD with liquid metal

109. What is the working principle of a magnetohydrodynamic power plant?

MHD operates on the same concept as a dynamo. High-temperature plasma is passed through the magnetic field at sonic speed instead of solid conductors. Current is induced when gas is passed through a magnetic field. This generated current is collected via electrodes.

110. What is the purpose of control rods?

The control rods are used to start the chain reaction, maintain it at the required level, and shut down the reactor in the event of an emergency.