Question 1. Do You Know In Flight, How Many Attempts Will The Autostart Perform?

Answer :The autostart will make continuous start attempts until the engine either starts or the pilot
aborts the start attempt. FCOM 1 70.20.7

Question 2. Tell Me Who Is A Power Plant Operator?

Answer :A power plant operator is a person who operates a power plant. He has got to be good at
the technical skills of using the power plant and must be equally talented in distributing the work
to the other workers who are working with the power plant.

Question 3. Tell Me When Is The Auto-relight Function Activated?

Answer :When ever an engine is at or below idle with the fuel control switch in RUN. FCOM 1
70.20.8

Question 4. Tell Me What Can You Do To Drive The Blades Of The Turbine Faster And
Preventing The Damage Of The Blades?
Answer :Steam should be heated to the temperature it is before making it to enter the turbine
because superheated steam produces a lot of energy and also prevents the blades from rusting or
damaging.

Question 5. Tell Me What Things Are Missing From A Natural Gas Power Plant To A Coal
Power Plant?
Answer :CHP & stock yard, crushers, coal conveyors, wet or dry ash disposal, ash slurry disposal
units, ash pond, LDO HFO oil elevations.

Question 6. Explain What Are The Primary Engine Parameters Displayed On Eicas?
Answer :EPR, N1 and EGT. FCOM 1 70.20.1

Question 7. Explain When Is A Crossbleed Start Indication Displayed Next To The N3

Indication?
Answer :If the airspeed is below that recommended for a windmilling start. FCOM 1 70.20.7

Question 8. Do You Know What Are The Secondary Engine Parameters?

Answer :N2, N3, fuel flow, oil pressure, oil temperature, oil quantity and engine vibration. FCOM
1 70.20.1

Question 9. Do You Know How Many Ignitors Are Used For In Flight Starting?
Answer :Dual ignitors are always used for in flight starts. FCOM 1 70.20.8

Question 10. Tell Me Have You Ever Come Across A Situation When The Plant Went Into
Some Technical Issues, How Did You Manage That?
Answer :Technical issues are very common in a plant, give an example from your past experience
where you successfully managed to overcome a technical issue.

Question 11. Tell Me After The Production Of Electricity, Why Do We Increase The Voltage
Before Sending It To The Grid?
Answer :To avoid the transmission losses.
Question 12. Tell Me Which Eicas Message Indicates That Actual Thrust Is Significantly
Less Than The Commanded Thrust?
Answer :ENG THRUST (L or R). FCOM 1 70.20.16

Question 13. Tell Me What Is The Amount Of Energy Out Of The Total Energy Produced
That Is Taken Away By The Boiler Feed Pump?
Answer :A boiler feed pump takes away one third part of the energy generated by the power plant.

Question 14. A Grate, In A Boiler, Is A Place In The Combustion Chamber Upon Which
Fuel (wood Or Coal) Is Burnt.
Answer :
True
Question 15. Explain What Will You Do When Your Timed Schedule Or Jobs Assigned To
The Plant Fail To Meet Due To Some Unforeseen Forecast Conditions?
Answer :This happens generally on every other day in this profession, but the key is not to stay
back but move on. I will take some preventive measures to avoid loss of resources.

Question 16. In Water Tube Boilers Are?

Answer :water passes through the tubes which are surrounded by flames and hot gases

Question 17. Explain And Convince Me That You Can Adapt To A Wide Variety Of People,
Situations And Environments?
Answer :Swithching from oil to propane.

Question 18. Do You Know And Can You Comment Why Some Cooling Towers Are 300
Feet Tall And Others Are Like 30x30 Cubicle On Top Of A Building?
Answer :It depends on the type of plant and the application the tower has to deal with it.

Question 19. Tell Me Which Rotor Vibration Is Most Likely To Cause Tactile Vibration?
Answer :N1. FCOM 1 70.2016

Question 20. Explain Why Is A Block Of Coal Crushed Into Powder Before Burn?
Answer :A block of coal takes a lot of time to burn and give out the energy, but the powdered coal
burns uniformly faster and since it is in its powdered form the entire coal burns and there is no
waste of coal which leads in achieving greater calorific value.

Question 21. Do You Know What Is Lock Out Tag Out?

Answer :It is a procedure that is used for the protection of the workers and the equipments during
the maintenance or repair of the power plant.

Question 22. Explain When Will The Engine Fail Message Appear On The Pfd?
Answer :If actual thrust is less than commanded thrust during takeoff with airspeed between 65kts
and V1-6kts. FCOM 1 70.20.16

Question 23. Tell Me What Do You Feel Is An Acceptable Work Attendance Record?
Answer :Safety driven and self directed, I can and do work with minimal supervision and always
put my plant and co- workers safety above all else.

Question 24. The Object Of Producing Draught In A Boiler Is?

Answer :to provide an adequate supply of air for the fuel combustion
to exhaust the gases of combustion from the combustion chamber
to discharge the gases of combustion to the atmosphere through the chimney

Question 25. Explain What Is The Difference Between An Induced Draft And Forced Draft?
Answer :Forced draft installed to force the air inside the plant while the induced draft fetches and
pulls the air inside the air.

Question 26. Explain How Important Is Safety To You?

Answer :Safety in this profession is very important for every worker working inside the plant. A
small mistake can lead to a big hazard and hence every minor chance of a mistake should be taken
seriously.

Question 27. Explain The Abilities You Have In Order To Work With Us As A Boiler
Operator?
Answer :I'm familiar with the boiler operation, I was trained to fix and install boiler. I am a good
trouble shooter and a good operator.

1. Gauge glass is used for to see how much water is in the

boiler.( True )

2. What is the purpose of a safety relief valve on the boiler?

Ans. safety relief valve is used to relieve the boiler pressure when it
exceeds the MAWP (maximum allowable working pressure) and there

3. What is an induced draft?

Ans: when the fan on the exhaust side of boiler pulling air through the
boiler.
4. A steam trap is a device used to release condensation and
hold steam in a radiator or return line. (True)
5. State that it is true or false when a pressure relief valve open
when the MAWP is exceeded by 6%?
Ans .Yes
6. A boiler operator operating a boiler that he knows is unsafe
may, or may NOT have his license officially canceled. (False)
7. Which type of material is used for boiler gaskets?
Ans.: Asbestos or Neoprene
8. The main purpose of draining the glass gauge is to verify that
the pipes to the gauge are clean and open. (True)
9. Water is changed to steam by:
Ans. The application of heat.
10. A safety device used to cut fuel to the boiler when the water
level falls below a safe level.
Ans. Low-water cut-off (fusible plug)
11. The three most common fuels used in boilers are:
Ans.: Coal, gas and oil and biomass also.
12. A high-pressure steam boiler operates at a pressure above
15 psi. (True)
13. In a fire tube boiler the heat and gases of combustion pass
through the tubes. (True)
14. State the resin behind why cold start up of boiler takes
slowly?
Ans.: To allow the boiler to expand uniformly (thermal expansion) under
the action of the increasing pressure.
15. Regardless of the type of fuel being used, before lighting a
boiler during a cold start-up, the operator must first:
Ans. Check for the correct water level inside the drum level.
16. As boiler steam pressure increases, there is a corresponding
increase in the:
Ans: Temperature
17. Incomplete combustion can be caused by:
Ans.: insufficient air supply to the fuel as it is being burned.
18. with the respect to the law of Boiler regulation Any operator
foundoperating a boiler without a certificate issued by the Boiler
Inspection Division, or operating a boiler knowing it to be
defective shall:
Ans: Have his license officially canceled at once
19. The three types of drafts are:
Ans: Induced, Forced and Natural
20. In a water tube boiler, the heat and gases of combustion
pass around the tubes.(True)
“You are reading article (top 50 boiler information booster
question answers) on website www.askpowerplant.com”
21. What is the name of valve which is installed between the
boiler and the return pump?
Ans.: Check Valve NRV (Non Return Valve)
22. What is the function of the check valve?
Ans: To prevent the water from returning to the condensation tank from
the boiler after the pump shuts off.
23. What are the four main safety features required on the
steam boiler are:
Ans: Safety relief valve, blow-down valve, low water cut-off, and pressure
gauge
24. Safety relief valves should be set by:
Ans: Qualified safety valve technician/firm
25. Which pressure is considered to be that of a low-pressure
boiler?
Ans: 0 – 15 PSI MAWP (maximum allowable working pressure)
26. What happen when a steam valve is opened quickly?
Ans: Water could be siphoned out of the boiler causing damage to boiler
and steam lines.
27. Why is steam lines insulated?
Ans: To prevent loss of heat during steam transfer.
28. What operating pressure indicates a high-pressure boiler?
Ans: 16 PSI and above
29. A steam valve should be opened slowly.( True )
30. Improper mixtures of gas and air cause soot in boiler flues.
(True )
31. A low-water cut-off device does not affect the fuel to the
boiler when the water level drops.
Ans: False
32. Valves on the water column to check the accuracy of glass
gauge and determine the water level in a boiler, when glass
gauge is suddenly broken are called:
Ans: Gauge cocks
33. You cannot check a safety relief valve by opening it at full
working pressure.
Ans: False
34. A boiler is used for what purpose?
Ans: To produce steam or hot water for heat
35. The three most common fuels for firing boilers are coal, gas
and oil. (True )
36. The parts of a high-pressure boiler containing pressure (not
fitting or appliances) are made out of:
Ans: Steel
37. The primary function of a boiler is to:
Ans: Produce steam
38. Water will boil and turn to steam at 212º degrees F at
atmosphere pressure.(True )
39. Main two types of boilers are:
Ans: Fire tube and water tube
40. The three requirements for combustion are:
Ans: Fuel, heat and oxygen
41. What is a water injector (feed pump)?
Ans: A mechanical device for forcing water into a boiler against high
pressures. Injector pump is used into super critical boilers
42. What is the purpose of a baffle wall in a boiler?
Ans: To distribute flame evenly
43. If a boiler is not kept clean internally, scales will form and
cause the boiler not to blister. (False )
45. Water boilers at what temperature?
Ans: 212ºF (100 deg.C)
47. If you went into a boiler room and the fire was on, and there
was not water in the boiler, you should immediately add water
to the boiler. (False)
48. In a fire tube boiler the water flows through the tubes.
(False)
49. In a water tube boiler the fire passes through the tubes.
(False)
50. What are the two basic types of boilers?
Ans: Fire Tube: – In fire tube hot flue gases are kept inside the tube and
water kept outside the tube .fire tube boiler are small in capacity And in
water tube boiler water inside the tube and hot flue gases are outside the
tube. Water tube boilers are large in capacity.

Question 1. What Is The Function Of A Boiler?

Answer :A Boiler supplies dry and saturated steam at the required pressure.

Question 2. Briefly Explain The Boiler Mounting, And Name Its Classifications?
Answer :A particular apparatus or equipment is placed on the boiler to improve its safety,
maintenance convenience and steam supply, is known as Boiler mounting. Following are the
different Boiler mountings,
Water level
Supply valves
Pressure gauge
Stop valve
Feed check valve
Blow off cock
Anti printing pipe
Fusible plugs etc

Question 3. What Is A Valve?

Answer :A valve is used to control the flow of fluid inside the pipeline.

Question 4. Discuss The Function Of Safety, Stop, And Feed Check Valves?
Answer :Safety valve. This type of valve is used to keep the boiler safe by controlling the working
pressure in the boiler and resist the blasting due to the high pressure; the valve is mounted with
boiler.
Stop valve. This type of valve is used to control the flow of steam from the boiler to the engine.
Feed Check valve. This type of valve is used to control the supply of feed water to the boiler. The
water level always remains constant when it works.

Question 5. What Is Meant By A Piston And Cylinder?

Answer :A piston is a cylinder piece of metal. It is moved within a hollow cylinder by the pressure
of fluid (liquid, steam or gas).Pistons are easy fit in the cylinder and piston rings are used to prevent
the leakage in between piston and cylinder.

Question 6. Name The Different Types Of Materials Used To Made Pistons?

Answer :Pistons are made by different materials such as cast iron, cast steel, aluminium ,bronze,
forged steel, brass etc.
Question 7. What Is A Locomotive Piston?
Answer :Locomotive pistons are of disc type which are generally made of cast iron or steel. Its
piston rings are made of cast iron and are located by dowels.

Question 8. What Is The Difference Between Plunger Piston And Bucket Piston?
Answer :Plunger piston is suitable when the fluid pressure is acting on one side of the piston only.
Bucket piston has one or more valves which permit the fluid to pass one side to the other.

Question 9. What Is A Buck Piston?

Answer :It is also known as trunk piston which is open ended and is generally made longer. Cross
head or piston rod is not necessary for it.

Question 10. What Are Piston Rod And Piston Valve Of Steam Engine?
Answer :Piston rod is fitted inside the piston. The diameter of this rod is inside the piston is reduced
to about 3/4th of its diameter. Piston valve is tightened by a nut and locked out by a pin.
Question 11. Write A Short Note On Steam Engine Piston?
Answer :Generally box type or hollow type steam engine pistons are used. These are generally
made of cast iron. Box type pistons are cast in one piece with hollow core. This piston is secured
by a nut to the piston rod. To prevent the leakage of the steam two piston rings are provided with
the piston. In the modern reciprocating steam engines the piston made of cast steel and of conical
shape is used. The piston made of cast steel is costly than that of cast iron.

Question 12. What Is A Cross Head Of A Steam Engine?

Answer :Cross head is used to connect the connecting rod and the piston rod. It is generally made
of cast iron, cast steel or forged steel. The piston rod may be fastened to the cross head either by a
screw or by a cotter pin.

Question 13. Explain About A Crankshaft?

Answer :The crankshaft converts the rectilinear reciprocating motion into circular motion and vice
versa. When the crankshaft moves through 180 degree, the crank travels over a semicircular path
of the diameter. The crank travels one complete revolution and piston completes two strokes
backwards and forwards, when the crankshaft moves through 360 degree.

Question 14. What Is A Crank?

Answer :A Crank is a simple lever which receives the thrust of the piston through the connecting
rod. Generally crank disc, eccentric crank, overhung crank, bell crank etc. are used.

Question 15. Name The Different Types Of Packings Used In Steam Engine?
Answer :Soft packing. Used for general purposes. It is not suitable for high pressures and
temperatures.
Metallic packing. It is generally used where high pressures and temperatures exist because it is
more desirable for this purpose.
Semi-metallic packing. It is used where medium pressures and temperatures exist.
Question 16. Write The Procedure For Starting The Power Pump?
Answer :Clean the pump.
Check the correct quantity of the recommended grade of oil to the pump.
Check the drive rotation.
Check grease or oil to the coupling if necessary.
Turn the pump by hand(it should run freely)
Open the suction, vent, bypass and discharge valves.
Start the pump.

Question 17. Explain Briefly The Metering Pumps?

Answer :Generally these types of reciprocating pumps are relatively small and light in weight.
Small reciprocating pumps are fixed on a light structural frame and other pumps have metal base
bolted with the floor. Tank mounted pumps need no foundation but the tank is to be fixed.

Question 18. Name Different Types Of Reciprocating Pumps?

Answer :Steam pumps, Power pumps, Metering pumps, Axial piston pumps and Sucker rod
pumps.

Question 19. Write The Operational Steps Of A Steam Pump?

Answer :Make sure that all the suction, discharge, steam and exhaust lines are open.
Open steam end drain valves.
Prime by opening air cock on liquid cylinder cap.
Crack steam valve to warm the pump.
Open the steam valve until the piston begins to move slowly.
Close the drain valve and open the steam valve until the pump comes up to the working speed.
To stop the pump close the steam valve first and then close exhaust, suction and discharge valves.
Question 20. What Are The Reasons When Piping Vibrates In Power Pumps?
Answer :In a power pump the piping vibrates when discharge pipe is undersize or suction pipe is
undersize.

Question 21. Why A Centrifugal Pump Will Not Start?

Answer :It is due to,
Impellers locked or not adjusted properly
Trash in casing
Faulty motor.
Too much bearing friction.

Question 22. Explain About Hydraulic Ram?

Answer :It is an automatic pump. It is generally used to lift a water falling through a small height.
i.e, water falling in large quantity through a small height is lifted to a greater height in small
quantity. The automatic action of the ram takes place due to the inertia force.

Question 23. Name Different Types Of Rotary Pumps?

Answer :External gear pumps, Internal gear pumps, Sanitary type pumps, External screw pumps,
Three screw pumps, Swinging and sliding vane pumps and Flexible rotor pumps.
Question 24. Why A Centrifugal Pump Does Not Deliver Liquid?
Answer :The centrifugal pump does not deliver liquid due to:
Wrong rotation
Pump not primed
Speed too low.

Question 25. What Are The Causes Of Reduced Capacity Or Pressure In Axial And Radial
Piston Pumps?
Answer :Clogged or leaking suction.
Oil is too thick.
Relief valve troubles.
Liquid lever is too low.

Question 26. Name Different Types Centrifugal Pumps?

Answer :Multistage pumps, Process type pumps, Chemical process pumps, Canned motor pumps,
Paper stroke pumps and Deepwell turbine pumps.

Question 27. What Is The Main Reason Of Steam Pump Breakdown?

Answer :Steam pump stops due to valve trouble. i.e, incorrectly set or worn steam valves may stop
the steam pump.

Question 28. Why A Steam Pump Does Not Discharge?

Answer :It is due to ,
Suction air bound
Suction lift too high
Obstruction in suction line
Pump not primed.

Question 41. Define Static Electricity?

Answer :When a glass rod is rubbed with a silk cloth, it becomes positive charge and when a
ebonite rod is rubbed with a woolen cloth, it becomes a negative charge. The change produced in
glass or ebonite rod is known as Static electricity. There is no movement of electrons in this
electricity.

Question 42. What Is Current Electricity?

Answer :The electrons move and flow along the conductor in this electricity. If direction of flow
electrons is always the same, it is known as Direct Current (D.C). If the direction of flow of
electrons is changed constantly, it is known as Alternative Current (A.C).

Question 43. Define Volt?

Answer :Volt is the force which causes an electron flow of one ampere through a resistance of one
ohm.

Question 44. What Are The Advantages Of A.c Over D.c?

Answer :A.C is produced much more as compared to D.C.
An alternative voltage can be increased to a desired limit by a transformer while D.C can not be
increased.
A.C is less expensive than that of D.C.
A.C induction motors are more useful for constant speed as compared to D.C motors.
A.C motors require less maintenance as compared to D.C motors.
A.C generators can be made in large size which can run at high speed also than that of D.C
generators.

Question 45. Define Ampere?

Answer :It is the amount of electron flow in the current . In one ampere 6.28*10/18 electrons has
a given point in the conductor within a period of one second.

Question 46. Write A Short Note About Fuse?

Answer :A fuse is a small piece of wire which is normally used in the circuit. It protects against
the bad effects of short circuiting. When a current in the circuit rises above its desired limit, the
fuse will be heated and melt which causes the circuit “Open” and saves the components and
appliances from the possible damage.

Question 47. What Do You Meant By A Short Circuit?

Answer :It has not resistor. It causes a high current flow which may heat up the wire. It may cause
fire and damage the electrical appliances in the circuit.

Question 48. What Are The Effects Of Electric Current?

Answer :Heating effect. When a current flows in a wire and generators heat like filament lamp,
electric heater, furnace etc. is called electric effect.
Chemical Effect. When electricity passes through a chemical solution , it can make chemical like
cells, batteries, electroplating etc. it is called chemical effect.
Magnetic effect. When a current flows in a coil ,it makes a magnetic field like bell, motor,
generator, transformer, tape recorder etc. called magnetic effect.

Question 49. What Is The Difference Between Conductors And Insulators?

Answer :Conductors. When a material allows electrons to flow through it known as conductors.
Eg. Copper ,aluminium ,iron ,tin, gold .
Insulators. The materials which prevent the flow of electrons are known as insulators. Eg: Rubber
,asbestos ,plastics, mica.

Question 50. What Are The Advantages Of D.c?

Answer :It is suitable for traction work.
It is suitable for charging batteries.
It is suitable for variable speed motors used in printing machines.
It is useful lamps used in projectors.

1. What are the specifications of TS-II Boiler?

Tower type, Water tube, Single Drum, Single stage oil firing , Two stage tangential firing,
Suspended Lignite firing, Non-Steaming Economizer, Balanced Draught system with AP blading
fans, Dry bottom furnace, ESP with wet ash disposal system, Top hanging , 210 MW, 210 T of
lignite/ hr, Sub critical operating pressure.

3. Why tower type boiler is used in TS – II?

Ø As the Lignite used in TS – II is high erosive in nature due its coarse shape, so that we have to
minimize the flue gas velocity to 10 m / sec to minimize the eroding of tubes. When the flue gas
is moves it has to travel against the gravity so its velocity should be reduced due to the height of
the boiler.
Ø To enhance the natural circulation by increasing the height of the down comers and up risers.

4. What is the circulation number?

It is defined as “the ratio by weight of water entering in to the steam generating circuit to the weight
of steam generated”. i.e., number of times the unit weight of water circulated in the tube to get
completely converted in to steam.

5.What are the factors which affect the Natural circulation?

i) Height of the downcomer and Water wall tubes
ii) Density difference of water and steam

6.What are the effects when circulation number increases or decreases?

If circulation number increases:
Ø Chance of scale formation is less
Ø Occurrence of DNB will less
Ø Boiler size become increases
Ø Efficiency become lower
Ø No chance of overheating of tubes
If circulation number decreases:
Ø Chance of scale formation is more
Ø Occurrence of DNB will be high
Ø Boiler size become small
Ø Efficiency will be higher
Ø Chance of overheating of tubes ( due to starvation)

7. What is Natural circulation? How it takes place?

It is defined as the movement of fluid in the water wall tubes without any external pumping
device.It occurs due to difference in densities in contents of fluids in down comers from the drum
and the uprisers in the furnace is used to effect the movement of fluid .

8. What is Forced circulation?

The water is pumped through water wall circuit using circulating pump is placed near the bottom
header and its suction from downcomer. Water is pumped under pressure through tubes ensuring
positive circulation.

9. Why once through boilers are having circulation ratio of only one?
Once through boilers operate at a pressure above critical point at that pressure water flashed in to
steam directly without actually boiling. In such cases water need not be circulated more than once
for converting the water in to steam.

10. Which type of Economiser is used in TS-II? Why so?

Non steaming type of economiser is used in TS-II. Because to make natural circulation effective,
the outlet of economiser should contain only saturated water. But if steaming type is used, due
latent heat addition, it leads to formation of steam + water mixture which may affect natural
circulation.

11. What is RAPH & SCAPH and their functions?

Regenerative air preheater (RAPH) is mainly used for preheating the FD fan outlet air by utilising
the outgoing flue gas temperature for making the combustion a rapid and efficient one.

Steam coil air preheater (SCAPH) is employed mainly during start up. As during start up, the
fluegas temperature at the inlet of RAPH will be less. If the air extracts more heat from the flue
gas, the flue gas temperature falls below 140°C and it leads to cold end corrosion. So to avoid this
air is preheated by SCAPH to that steam supplied from the AST header. So that heat transfer rate
in RAPH can be reduced without allowing fluegas temperature to fall below 140°C. The SCAPH
is located after FD fan outlet and before RAPH.

12. What is the condition of charging the SCAPH?

I ) During initial start up when flue gas temperature at RAPH is floating around acid due point or
below it.
ii) Before LSHS firing taken in to service.
iii) When boiler is at low load i.e., oil is used for stabilizing the flame.

13. When RAPH comes into service?

Before starting the ID fan and FD fan , the RAPH should be taken in to service in order to avoid
the starting load of the RAPH motor.

14. Is the RAPH discharge directly connected to ID fan?

No, RAPH discharge is connected to ID fan via ESP.

15.What is cold end corrosion? When it occurs?

During Cold Start up, flue gas temperature may go below acid dew point as a result sulphur- di-
oxide react with moisture content in flue gas and leads to formations of Sulphuric Acid. When acid
comes in contact with tubes it leads to acid attack of tubes. This is meant by cold End Corrosion.
To avoid this, during cold start up lignite with low sulphur content to be used.

16. What leads to phase change in boiler?

When the latent heat is added to saturated water from drum, phase change occurs.

17. What is the difference between steaming type and Non steaming type Economiser?
Steaming type: Sensible heat and partial latent heat is added to the feed water in the steaming
type economizer to obtain steam and water mixture.
Non steaming type: Sensible heat is alone added to the feed water in the Non steaming type
economiser to obtain only water with its temperature is maintained well below the saturation
temperature .

18. Which economizer is best one and Why it so ?

Non steaming type economizer is the best one .
Ø It enhance the natural circulation
Ø Effective utilization of heat carried away by the flue gas is recovered for preheating the air in
RAPH
Ø Efficiency of the boiler will increase

19. Why economiser is kept at the top of the boiler?

In Non steaming economiser, the sensible heat is alone added to the feed water. So that steam free
water is produced. To keep up this condition, economiser is kept at the top of boiler i.e. over all
the pressure parts. So that the flue gas temperature at the top of boiler i.e., near the economiser
will be able to add only sensible heat.

20. Why there are two economizers

Ø To provide uniform heating of feed water
Ø To avoid overheating of tubes or starvation during start up

21. What is the type of super heater – 1 and where it is located?

Super heater – 1 is counter flow type. It is located at 40.8 meter level.

22. Why SH - 1 is starting from 40 mL?

Ø SH – 1 is placed at 40 mL, because most of the heat available below the SH – 1 is sufficient
enough to add sensible and latent heat to water wall tubes for producing steam and water mixture.
Otherwise if SH – 1 is placed below 40 mL, SH – 1 also takes up the heat and heat transfer to the
water wall tubes reduced.
Ø If SH – 1 is below 40 mL, it may be exposed directly to firing of high temperature which the
SH – 1 tubes can’t withstand ie., metal constraint

23. Why SH – 2 is placed over SH – 3?

The maximum temperature we are maintaining in SH – 3 only. If we arranged in ascending order
means there may be a chance of cooling in SH – 3 compared to SH – 2 due to temp difference in
flue gas. To avoid such problem, SH – 2 is placed over SH – 3.

24. What are the sources for De super heaters?

For super heater attemperation the source is taken before Feed control station and for Reheater
attemperation source is taken from BFP III stage.

25. What are the steam parameters in TS – II?

Temperature - 540°C
Pressure - 157 Ksc
Flow rate - 690 T/hr

26. What are the sources for AST header ?

1) Main steam line
2) CRH line
3) Package boiler ( if any )
4) Inter connected line from other units

27. What is the balanced draft system and why it is adapted here?
Balanced Draft System is a combination of Induced and Forced Draught Systems. The forced
Draught Fan forces the air in to the furnace for combustion and the induced draught fan sucks in
gases from boilers side and discharges them in to the chimney.
This System is used to create and maintain vaccum inside the furnace

28. What is the difference between FD and ID fan?

FD fan ID fan
a) It handles only atmospheric air It handles dust laden gases
b) Speed of rotation is more Speed of rotation is less
c) As it handles atm. air the blades As it handles flue gas, the blades are
are comparatively thin. antierosive and comparatively thick.
d) It is not provided with any cooling It is having a separate cooling air arrangement
of shaft, blades fan
e) Discharge Pressure : 500-510 mm of WC Discharge Pressure = 398s mm of WC

29. Can the blades of FD fan be replaced by the ID fan blades ?

Yes, but the power consumption will increase and motor will be unnecessarily overloaded.

30. What is the function of pitch control mechanism?

To vary the blade angle of FD and ID fan , in order to vary the quantity of air flow across the fan
by means of hydraulic servomotor.

31.For what purpose dampers are used and where these are located ?
a) Dampers are used to start the FD and ID fan at no load condition
b) During maintenance to keep it is isolate condition
c) During only FD - A and ID - A fan running condition to avoid the reverse flow through the
ID - B fan Via the chimney.
In the air path, air damper is located after FD fan and before RAPH
In the flue gas path, gas dampers are located before RAPH and after ID fan

33. Why Dm Plant is used?

To remove the suspended and dissolved impurities present in the raw water.

34. What are the salts present in the raw water

Calcium Chloride (Cacl2)
Magnesium Chloride
Calcium Sulphate
Magnesium Sulphate
Calcium Bicarbonate
Magnesium Bicarbonate
Silicic acid

35. Where the salts are removed?

Weak Acid Cation Bed – Temporary hardness causing salts in water are removed such as Calcium
Bicarbonate, Magnesium Bicarbonate.
Strong Acid Cation - Permanent hardness causing salts in the raw water are removed. The salts are
Calcium Chloride (Cacl2)
Magnesium Chloride, Calcium Sulphate, Magnesium Sulphate

36. What are all the other places where the salt is removed?
Mixed Bed Unit
Boiler drum by CBD

37. What is meant by Ion Exchange process?

The process in which Hydrogen and Hydroxyl ions in the resin exchange with cations and anions
present in the water respectively is called as Ion Exchange process

38. What is the unit of Solubility?

1. Parts per million (ppm)
2. Milligrams per litre (mg/litre)

39. What is the maximum solubility in water?

Silica content <=0.02 ppm

40. What is TDS?

TDS is meant by Total Dissolved salts
It is calculated by using the formula
TDS= 0.65(solubility)

41. What are the various chemical treatments in Boiler?

Trisodium Phosphate -HP dosing done in the boiler drum
Hydrazine – LP Dosing – Done at outlet of Deareator /Suction of BFP-To remove dissolved
oxygen if feed water to avoid corrosion.

42. Where the salt concentration increases and How?

The salt concentration increases in boiler drum.
Reason: As the Steam donot have the tendency to carry with it the salts. And during Steam
separation salts are left back in the drum itself leading to increase in salt concentration in Drum.

Q.(A).What is the affect of sulfur in coal when used in boiler?

Sulfur will get oxidized to SO2 and fraction of SO3 and will react with water to form sulfuric acid
and this occurs at a temperature called the acid dew point which normally is about 120 oC. The
sulfuric acid so formed corrodes the steel when it comes in contact with it
Q.(B).What do you mean by IBR steam boiler.
IBR Steam Boilers means any closed vessel exceeding 22.75 liters in capacity and which is used
expressively for generating steam under pressure and includes any mounting or other fitting
attached to such vessel, which is wholly or partly under pressure when the steam is shut
off.

Q (B.1)What do you understand by ‘water tube boilers’ and ‘fire tube boilers’?
In water tube boilers the water passes through the tubes and the hot gases passes out side the tubes
whereas in case of fire tube boiler the hot gases passes through the tubes and the water passes over
the tubes

Q(C).What are the parameters required to estimate the boiler efficiency by ‘direct method’?
1. a) Steam flow rate
2. b) GCV of fuel
3. c) Fuel flow rate
4. d) Steam conditions ( pressure and temperature)
5. e) Feed water temperature

Q (D).Why boiler blow-down is required?

As the feed water evaporate into steam, dissolved solids concentrate in the boiler. Above certain
level of concentration, these solids encourage carryover of water into steam. This leads to scale
formation inside the boiler, resulting in localized over heating and ending finally in tube
failure. Hence blow-down is very much required for boilers.

Q (E).What is the principle of mechanical deaeration (pressure

type) of boiler feed water?
The pressure-type de-aerators operates by allowing steam into the feed water through a pressure
control valve to maintain the desired operating pressure, and hence temperature at a minimum of
105 °C. The steam raises the water temperature causing the release of O2 and CO2 gases that are
then vented from the system. This type can reduce the oxygen content to 0.005 mg/litre.

Q (F).What is the effect of boiler loading on boiler efficiency?

The maximum efficiency of the boiler does not occur at full load, but at abou ttwo-thirds of the
full load. If the load on the boiler decreases further, efficiency also tends to decrease. As the load
falls, so does the value of the mass flow rate of the flue gases through the tubes. This reduction in
flow rate for the same heat transfer area, reduced the exit flue gas temperatures by a small extent,
reducing the sensible heat loss. Below half load, most combustion appliances need more excess
air to burn the fuel completely. This increases the sensible heat loss.

Q (G).What are the principle heat losses that occur in a boiler?

The principle heat losses that occur in a boiler are:
• Loss of heat due to dry flue gas
• Loss of heat due to moisture in fuel and combustion air
• Loss of heat due to combustion of hydrogen
• Loss of heat due to radiation
• Loss of heat due to unburnt fuel

Q (H).What do you meant by tangential firing with respect to pulverized coal fired boiler?
The method of firing used for coal firing in pulverized fuel fired boiler is the tangential firing. In
this type of firing four burners are used at the corner to corner to create a fire ball at the center of
the furnace.

Q (I).What are the disadvantages of ‘direct method’ of boiler efficiency evaluation over
‘indirect method’?
Direct method
a) Do not give clues to the operator as to why efficiency of system is lower
1. b) Do not calculate various losses accountable for various efficiency levels
J.List out the data required for calculation of boiler efficiency using
‘indirect method’.
The data required for calculation of boiler efficiency using indirect
method are: Ultimate analysis of fuel (H2, O2, S, C, moisture content, ash content)
Percentage of Oxygen or CO2 in the flue gas
Flue gas temperature in 0C (Tf)
Ambient temperature in 0C (Ta) & humidity of air in kg/kg of dry air. GCV of fuel in kcal/kg
Percentage combustible in ash (in case of solid fuels)
GCV of ash in kcal/kg (in case of solid fuels)

Q (K).Explain the different external water treatment methods.

External treatment is used to remove suspended solids, dissolved solids (particularly the Calcium
and Magnesium ions which is a major cause of scale formation) and dissolved gases (oxygen and
carbon dioxide). The techniques include Precipitation processes, in which chemicals are added to
precipitate calcium and magnesium as compounds of low solubility. The lime-soda process is
typical of this class, but other precipitating agents such as caustic soda and sodium phosphate can
be used when the composition of the raw water permits. Ion-exchange progresses, in which the
hardness is removed as the water passes through bed of natural zeolite or synthetic resin and
without the formation of any precipitate. Ion exchange processes can be used for almost total
demineralization if required, as is the case in large electric power plant boilers. De-aeration, in
which gases are expelled by preheating the water before entering the boiler system. Water normally
contains approximately 10mg/1 of dissolved oxygen at ambient temperature Filtration, to remove
suspended solids

Q( L).What are the salient features of a ‘packaged boiler’?

The features of package boilers are:
• Small combustion space and high heat release rate resulting in faster evaporation.
• Large number of small diameter tubes leading to good convective heat transfer.
• Forced or induced draft systems resulting in good combustion efficiency.
• Number of passes resulting in better overall heat transfer.
• Higher thermal efficiency at lower capacity (say below 1 ton) levels compared with other boilers.

Q (M).What are the two main classification of a stoker fired

boiler?
1. Chain grate or travelling grate stoker
2. Spreader stoker

Q (N).Briefly explain the principle involved in ‘reverse

osmosis’?
When solutions of differing concentrations are separated by a semipermeable membrane, water
from less concentrated solution passes through the membrane to dilute the liquid of high
concentration. If the solution of high concentration is pressurized, the process is reversed and the
water from the solution of high concentration flows to the weaker solution

Q (O).What are the various methods available to control the

‘excess air’ in a boiler?
Various methods are available to control the excess air:
• Portable oxygen analysers and draft gauges can be used to make periodic readings to guide the
operator to manually adjust the flow of air for optimum operation. Excess air reduction up to 20%
is feasible.
• The most common method is the continuous oxygen analyzer with a local readout mounted draft
gauge, by which the operator can adjust air flow. A further reduction of 10-15% can be achieved
over the previous system.
• The same continuous oxygen analyzer can have a remote controlled pneumatic damper
positioner, by which the readouts are available in a control room. This enables an operator to
remotely control a number of firing systems simultaneously.

Q (P).Describe ‘chain grate’ and ‘spreader stoker’ type boiler.

Chain-Grate or Travelling-Grate Stoker Boiler Coal is fed onto one end of a moving steel grate.
As grate moves along the length of the furnace, the coal burns before dropping off at the end as
ash. Some degree of skill is required, particularly when setting up the grate, air dampers and
baffles, to ensure clean combustion leaving the minimum of unburnt carbon in the ash. The
coal-feed hopper runs along the entire coal-feed end of the furnace. A coal grate is used to control
the rate at which coal is fed into the furnace by controlling the thickness of the fuel bed. Coal must
be uniform in size as large lumps will not burn out completely by the time they reach the end of
the grate Spreader Stoker Boiler Spreader stokers utilize a combination of suspension burning and
grate burning. The coal is continually fed into the furnace above a burning bed of coal. The coal
fines are burned in suspension; the larger particles fall to the grate, where they are burned in a thin,
fast-burning coal bed. This method of firing provides good flexibility to meet load fluctuations,
since ignition is almost instantaneous when firing rate is increased. Hence, the spreader stoker is
favoured over other types of stokers in many industrial applications.

Q (Q).Write short notes on ‘intermittent blow down’ and ‘continuous blow down’ with
respect to boilers.
The ‘intermittent blown down’ is given by manually operating a valve fitted to discharge pipe at
the lowest point of boiler shell to reduce parameters (TDS or conductivity, pH, Silica and
Phosphates concentration) within prescribed limits so that steam quality is not likelyto be affected.
In intermittent blowdown, a large diameter line is opened for a short period of time, the time being
based on a thumb rule such as “once a shift for 2 minutes”. ‘Intermittent blow down’ requires large
short-term increases in the amount of feed water put into the boiler, and
hence may necessitate larger feed water pumps than if continuous blow down is used. Also, TDS
level will be varying, thereby causing fluctuations of the water level in the boiler due to changes
in steam bubble size and distribution which accompany changes in concentration of solids. Also
substantial amount of heat energy is lost with intermittent blow down. ‘Continuous Blowdown’:
There is a steady and constant dispatch of small stream of concentrated boiler water, and
replacement by steady and constant inflow of feed water. This ensures constant TDS and steam
purity at given steam load. Once blow down valve is set for a given conditions, there is no need
for regular operator intervention. Even though large quantities of heat are wasted, opportunity exits
for recovering this heat by blowing into a flash tank and generating flash steam. This flash steam
can be used for preheating boiler feed water or for any other purpose. This type of blow down is
common in high-pressure boilers

Q (R).Explain the reasons for carrying out “blow down” in a boiler?

Water contains certain percentage of dissolved solids. The percentage of impurities found in boiler
water depends on the untreated feed water quality, the treatment process used and the boiler
operating procedures. As a general rule, the higher the boiler operating pressure, the greater will
be the sensitivity to impurities. As the feed water materials evaporate into steam, dissolved solids
concentrate in the boiler either in a dissolved or suspended state. Above a certain level of
concentration, these solids encourage foaming and cause carryover of water into the steam. This
leads to scale formation inside the boiler, resulting in localized overheating and ending finally in
tube failure.It is therefore necessary to control the level of concentration of the solids and this is
achieved by the process of ‘blowing down’, where a certain volume of
water is blown off and is automatically replaced by feed water – thus