Essential Steam Boilers Objective Questions For Gate Exam Part – 2
1.Boiler H.P. is defined as the
steam evaporation rate per kg of fuel fired
work done in evaporating 1 kg of steam per hour from and at 100�C into dry saturated steam
the evaporation of 15.65 kg of water per hour from and at 100�C into dry saturated steam
work done by 1 kg of steam at saturation condition
heat consumed in evaporating 1 kg water at 0�C to steam at 100�C and 1.033 kg/cm pressure.
ANSWER : : the evaporation of 15.65 kg of water per hour from and at 100�C into dry saturated steam
2.Size of boiler tubes is specified by
mean diameter and thickness
inside diameter and thickness
outside diameter and thickness
outside diameter and inside diameter
outside diameter alone.
ANSWER : : outside diameter and thickness
3.The heat loss in a boiler takes place in the form of
heat carried away by flue gases
heat carried away by ash
moisture present in fuel and steam formed by combustion of hydrogen in fuel
radiation
all of the above.
ANSWER : : all of the above.
4.In forced recirculation type boiler,
heating takes place at bottom and the water supplied at bottom gets con-verted into the mixture of steam bubbles and hot water which rise to drum
water is supplied in drum and through down-comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam
feed pump is employed to supplement natural circulation in water wall type furnace
water is converted into steam in one pass without any recirculation
heating of water takes place in stages.
ANSWER : : feed pump is employed to supplement natural circulation in water wall type furnace
5.With increase in load, radiant superheater has
drooping characteristic
lihear characterisstic
rising characteristic
flat characteristic
none of the above.
ANSWER : : drooping characteristic
6.The overall efficiency of thermal power plant is
boiler efficiency, turhine efficiecny, generator efficiency
all the three above plus gas cycle ef-ficiency
carnot cycle efficiency
regenerative cycle efficiency
rankine cycle efficiency.
ANSWER : : boiler efficiency, turhine efficiecny, generator efficiency
7.Fusible plug for boilers is made of fusible metal containing tin, lead, and
bismuth
copper
aluminum
nickel
iron.
ANSWER : : bismuth
8.The number of drums in Benson steam generator is
one
two
one steam drum and one water drum
no drum
none of the above.
ANSWER : : no drum
9.The major axis of elliptical manholes on the shell should be provided
longitudinally
circumferentially
on dished end
anywhere
vertically.
ANSWER : : circumferentially
10.With increase in load, convection superheater has
drooping characteristic
linear characterisstic
rising characteristic
flat characteristic
opt 5
ANSWER : 3 none of the above.
11.Which type of boiler can meet rapid changes of load
vertical fire tube type
horizontal fire tube type
horizontal water tube type
vertical water tube type
forced circulation type.
ANSWER : : forced circulation type.
12.The fusible plug in small boilers is located
in the drum
in the fire tubes
above steam dome
over the combustion chamber
at the inlet of chimney.
ANSWER : : over the combustion chamber
13.Thermal efficiency of well maintained boiler will be of the order
20%
40%
50%
75%
90%.
ANSWER : : 90%.
14.Thermal efficiency of a thermal power plant is of the order of
15%
20%
30%
45%
opt 5
ANSWER : ) 60%.
15.In a recuperative air preheater, the heat is transferred
from a metal wall from one medium to another
from heating an itermediate material and then heating the air from this material
by direct mixing ,
heat is transferred by bleeding some gases from furnace
none of the above.
ANSWER : : from a metal wall from one medium to another
16.The diameter of fire tubes in Cochran boiler is of the order of
2 cm
6 Cm ,
cm
12 cm
15 cm.
ANSWER : : 6 Cm ,
17.In forced circulation type boiler
heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum
water is supplied in drum and through down-comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam
feed pump is employed to supplement natural circulation in water wall type furnace
water is converted into steam in one pass without any recirculation
water is heated in a large number of tubes.
ANSWER : : water is converted into steam in one pass without any recirculation
18.The ratio of heat utilised to produce steam and the heat liberated in furnace is known as
boiler effectiveness
boiler evaporative capacity
factor of evaporation
equivalent evaporation
boiler efficiency.
ANSWER : : boiler efficiency.
19.It is required to produce large amount of steam at low pressure. Which boiler should be used ?
pulverised fuel fired boiler
cochran boiler
lancashire boiler
babcock and wilcox boiler
stoker fired boiler.
ANSWER : : lancashire boiler
20.Steam in water tube boiler as compared to fire tube boiler
can be raised rapidly
is raised at slower rate
is raised at same rate
could be raised at fast/slow rate depending on design
none of the above is true.
ANSWER : : can be raised rapidly
21.A fusible plug is fitted in small boilers in order to
avoid excessive build up of pressure
avoid explosion
extinguish fire if water level in the boiler falls below alarming limit
control steam dome
remove molten ASL.
ANSWER : : extinguish fire if water level in the boiler falls below alarming limit
22.Boiler stays are used to
prevent flat surfaces under pressure from tearing apart
take care of failure in shear
take care of failure in compression
provide support for boiler
provide foundation of boiler.
ANSWER : : prevent flat surfaces under pressure from tearing apart
23.In which of the following boilers, the draught in furnace is increased by utilizing exhaust steam from engine
lancashire boiler
locomotive boiler
babcock and wilcox boiler
cochran boiler
benson boiler.
ANSWER : : locomotive boiler
24.The radius of a dished head is taken approximately as
one-fourth
half
one
two
three.
ANSWER : : one
25.The function of injector used in small capacity boilers is to
create vacuum
inject chemical solution in feed pump
pump water, similar to boiler feed pump
add make up water in the system
none of the above.
ANSWER : : pump water, similar to boiler feed pump
26.An economizer in a boiler
increases steam pressure
increases steam flow
decreases fuel consumption
decreases steam pressure
increases life of boiler.
ANSWER : : decreases fuel consumption
27.The economiser is used in boilers to
increase thermal efficiency of boiler
economise on fuel
extract heat from the exhaust flue gases
increase flue gas temperature
to heat feed water by bled steam.
ANSWER : : increase thermal efficiency of boiler
28.In regenerative air preheater, the heat is transferred
from a metal wall from one medium to another
from heating an intermediateanaterial and then heating the air from this material
by direct mixing
heat is transferred by bleeding some gas from furnace
none of the above.
ANSWER : : from heating an intermediateanaterial and then heating the air from this material
29.The pressure of reheat steam after passing through reheated compared to inlet condition is
more
less
equal
may be more or less depending on capacity of reheated
none of the above.
ANSWER : : less
30.Ultimate analysis of fuel is determination of percentage of
carbon, hydrogen, nitrogen, sulphur, moisture
fixed carbon, ash, volatile matter, moisture
higher calorific value
lower calorific value
best analysis.
ANSWER : : carbon, hydrogen, nitrogen, sulphur, moisture
31.Spontaneous combustion is a phenomenon in which
all the fuel burns instantaneously producing high energy release
fuel burns with less air
coal bursts into flame without any external ignition source but by itself due to gradual increase in temperature as a result of heat released by combination of oxygen with coal
explosion in furnace
none of the above.
ANSWER : : coal bursts into flame without any external ignition source but by itself due to gradual increase in temperature as a result of heat released by combination of oxygen with coal
32.The safety valve at superheater as compared to drum safety valve setting is set at
higher value
lower value
same value
any value
none of the above.
ANSWER : : lower value
33.For combutsion of a fuel, following is essential
correct fuel air ratio
proper ignition temperature
02 to support combustion
all the three above
none of the above.
ANSWER : : all the three above
34.Steam exhaust from high pressure turbine is reheated in
boiler drum
superheater tubes
economiser
a separate coil
a separate coil located in convection path.
ANSWER : : a separate coil located in convection path.
35.The height of chimney in a power plant is governed by
the draft to be created
limitation of construction facilities
control of pollution
quantity of flue gases to be handled
all of the above.
ANSWER : : control of pollution
36.Reheating of steam under ideal conditions takes place at constant
entropy
enthalpy
pressure
temperature
all of the above.
ANSWER : : temperature
37.Which device is used in thermal power plants to reduce level of pollution
induced draft fan
smoke meter
chimney
precipitator
pulveriser.
ANSWER : : precipitator
38.Expanding steam to a very low pressure (high vacuum) in steam engines is
desirable
economical
essential
optional
uneconomical.
ANSWER : : uneconomical.
39 content in atmospheric air on weight basis is
21%
23%
30%
40%
opt 5
ANSWER : ) 70%.
40.Bomb calorimeter is used to determine
Higher calorific value at constant volume
Lower calorific value at constant volume ,
Higher calorific value at constant pressure
Lower calorific value at constant pres�sure
None of the above.
ANSWER : : Higher calorific value at constant volume
41.The maximum discharge through a chimney occurs when the height of chimney is
infinitely long
around 200 meters
equal to the height of the hot gas column producing drought
outside temperature is very low
more than the tallest building nearby.
ANSWER : : equal to the height of the hot gas column producing drought
42.Proximate analysis of fuel is determination of percentage of
carbon, hydrogen, nitrogen, sulphur, moisture
fixed carbon, ash, volatile matter, moisture
higher calorific value
lower calorific value
rough analysis.
ANSWER : : fixed carbon, ash, volatile matter, moisture
43.Vacuum for reciprocating steam engines compared to steam turbines is
more
equal
less
could be more or less depending on the size of plant
none of the above.
ANSWER : : less
44.Primary air is the air used to
provide air around burners for obtaining optimum combustion
transport and dry the coal
convert CO (formed in lower zone of furnace) into C02 at higher zone
air delivered by forced draft fan
none of the above.
ANSWER : : transport and dry the coal
45 content in atmospheric air on volume basis is
21%
23%
30%
40%
70%.
ANSWER : : 21%
46.In locomotives, the drought is produced by
chimney
induced draft fan
both combined (a) and (b)
steam jet drought
none of the above.
ANSWER : : steam jet drought
47.In designing air preheater, the important design consideration is that
approach temperature should be as low as possible
handling and maintenance should be easier
heat transfer area should be optimum
stack gases should not be cooled to the dew point
none of the above.
ANSWER : : stack gases should not be cooled to the dew point
48.The temperature of flue gases at air heater outlet should be
100�C
above dew-point temperature of flue gases
below dew-point temperature of flue gases
less than wet bulb temperature of flue gases
above wet bulb temperature of flue gases.
ANSWER : : above dew-point temperature of flue gases
49.The safety valve on boiler drum compared to safety valve on superheated is set ai
same value
higher value
lower value
lower/higher depending on steam flow
unpredictable.
ANSWER : : higher value
50.The ultimate analysis of fuel lists
various chemical constituents, carbon, hydrogen, oxygen etc, plus ash as per-cents by volume
various chemical constituents, carbon, hydrogen, oxygen, etc, plus ash as per-cents by weight
fuel constituents as percents by volume of moisture, volatile, fixed carbon and ash
fuel constituents as percents by weight of moisture, volatile, fixed carbon and ash
moisture and ash free heating value.
ANSWER : : various chemical constituents, carbon, hydrogen, oxygen, etc, plus ash as per-cents by weight
51.Secondary air is the used to
provide air around burners for obtaining optimum combustion
transport and dry the coal
convert CO (formed in lower zone of furnace) into C02 at higher zone
air delivered by induced draft fan
air fed to pulverizes.
ANSWER : : provide air around burners for obtaining optimum combustion
52.Which is not correct statement about the function of furnace
to provide proper conditions for continuous complete combustion
mix fuel with air and ignite
separate ash from coal
maintain heat supply to prepare and ignite the incoming fuel
to minimize radiation losses.
ANSWER : : separate ash from coal
53.Water and sediment in fuel oil can be removed by
heating the oil in the settling tanks
cooling the oil in the settling tanks
burning the oil
suspension
filtering.
ANSWER : : heating the oil in the settling tanks
54.Pulverized fuel is used for
better burning
more calorific value
less radiation loss
medium sized units
stoker fired boilers.
ANSWER : : better burning
55.Sulphur in coal results in
causing clinkering and slagging
corroding air heaters
spontaneous combustion during coal storage
facilitating ash precipitation
all of the above.
ANSWER : : all of the above.
56.Pour point of fuel oil is the
lowest temperature at which oil will flow under set condition
storage temperature
temperature at which fuel is pumped through burners
temperature at which oil is transported
none of the above.
ANSWER : : lowest temperature at which oil will flow under set condition
57.Calorific value of coal is of the order of
200-400 kcal/kg
800-1200 kcal/kg
2000-4000 kcal/kg
5000-8000 kcal/kg
8000-10,000 kcal/kg.
ANSWER : : 2000-4000 kcal/kg
58.Tertiary air is the air used to
provide air around burners for obtaining optimum combustion
transport and dry the coal
cool the scanners
supply air for seigniors
convert CO (formed in lower zone of furnace) into C02 at higher zone.
ANSWER : : convert CO (formed in lower zone of furnace) into C02 at higher zone.
59.Green coal, in order to be burnt, must be
heated sufficiently
burnt in excess air
heated to its ignition point
burnt as powder
burnt as lumps.
ANSWER : : heated to its ignition point
60.Incomplete combustion can be best judged by
smoky chimney exit
excess air in flue gases
measuring carbon mono-oxide in flue gases
measuring temperature of flue gases at exit of furnace
measuring oxygen in flue gases.
ANSWER : : measuring carbon mono-oxide in flue gases
61.Presence of moisture in fuel oil would
keep the burner tips cool
aid in proper combustion
cause sputtering, possibly extinguish�ing flame
clean the nozzles
reduce flame length.
ANSWER : : cause sputtering, possibly extinguish�ing flame
62.The three “Ts” for good combustion are
temperature, time, and turbulence
total air, true fuel, and turbulence
thorough mixing, total air, and temperature
total air, time, and temperature
none of the above.
ANSWER : : temperature, time, and turbulence
63.Which is not correct statement about pulverized fuel firing
high burning rate is possible
heat release can be easily controlled
fuel burns economically
it is the best technique for burning high ash content fuel having low fusion ash
separate mills are required to powder the coal.
ANSWER : : it is the best technique for burning high ash content fuel having low fusion ash
64.Pick up wrong statement about desired properties of a good fuel
high calorific value
produce minimum smoke and gases
ease in storing
high ignition point
economical
ANSWER : : high ignition point
65.Gradually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of
higher effectiveness of boiler
high calorific value coal being burnt
fouling of heat transfer surfaces
raising of steam temperature
leakage of air.
ANSWER : : fouling of heat transfer surfaces
66.Gusset stays in a boiler are provided to
prevent the bulging of flat surfaces
avoid explosion in furnace
prevent leakage of hot flue gases
support furnace freely from top
prevent atmospheric air leaking into furnace.
ANSWER : : prevent the bulging of flat surfaces
67.The behavior of coal in a furnace is determined by
the content of sulfur
the content of ash and heating value
the proximate analysis
the exact analysis
its type.
ANSWER : : the proximate analysis
68.Heating value of fuel used is as on fired basis. If it is reported for dry or moisture free fuel, then latter should be multiplied by the following factor to correct for as fired value
(1- moisture content)
(1 + moisture content)
1 + moisture content
1 – moisture content
opt 5
ANSWER : : (1- moisture content)
69.Which is not correct statement about effect of sulfur in fuel
it has heating value
it helps in electrostatic precipitation of ash in flue-gases
it leads to corrosion of air heaters, ducting, etc. if flue gas exit temperature is low
it erodes furnace walls
none of the above.
ANSWER : : it erodes furnace walls
70.Caking coals are those which
form lumps or masses of coke
burn freely
show little or no fusing action
burn completely
do not form ash.
ANSWER : : form lumps or masses of coke
71.The capacity of induced draft fan compared to forced draft fan in a boiler is
same
more
less
less or more depending on size of boiler
unpredictable.
ANSWER : : more
72.The proximate analysis of fuel lists
various chemical constituents, carbon, hydrogen, oxygen etc, plus ash as per-cents by volume
various chemical constituents, carbon, hydrogen, oxygen, etc, plus ash as per-cents by weight
fuel constituents as percents by volume of moisture, volatile, fixed carbon and ash
fuel constituents as percents by weight of moisture, volatile, fixed carbon and ash
moisture and ash free heating value.
ANSWER : : fuel constituents as percents by weight of moisture, volatile, fixed carbon and ash
73.The basic job of feed water treatment in boilers is to overcome the problem of
corrosion
scale
carryover
embitterment
all of the above.
ANSWER : : all of the above.
74.For the same diameter and thickness of tube, a water tube boiler compared to a fire tube boiler has
more heating surface
less heating surface
equal heating surface
heating surface depends on other parameters
none of the above.
ANSWER : : more heating surface
75.Fire tube boilers are limited to a maximum design working pressure of
1 kg/cm
6 kg/cm
17 kg/cm2
100 kg/cm2
250 kg/cm2.
ANSWER : : 17 kg/cm2
76.Boiler parameters are expressed by
tonnes/hr. of steam
pressure of steam in kg/cm2
temperature of steam in �C
all of the above
none of the above.
ANSWER : : all of the above
77.A super critical boiler is one that operates above the pressure and temperature of following values
100 kg/cm2 and 540�C
1 kg/cm2 and 100�C
218 kg/cm2 abs and 373�C
218 kg/cm2 abs and 540�C
100 kg/cm2 abs and 373�C
ANSWER : : 218 kg/cm2 abs and 373�C
78.Maximum energy loss in a boiler occurs due to
unburnt carbon in ash
incomplete combustion
ash content
flue gases
radiation losses.
ANSWER : : flue gases
79.The relative heat absorption for successively added equal areas of boiler convection heating surfaces
increases
decreases
remains unaffected
first increases and then decreases
first decreases and then increases.
ANSWER : : decreases
80.Overtire burning is the phenomenon of
supply of excess, air
supply of excess coal
burning CO and unburnt in upper zone of furnace by supplying more air
fuel bed firing
none of the above.
ANSWER : : burning CO and unburnt in upper zone of furnace by supplying more air
81.Feed water conditioning in thermal power plants in done to
reduce hardness and for removal of solids
increase efficiency-of thermal power plant
increase heat transfer rate
increase steam parameters
all of the above.
ANSWER : : reduce hardness and for removal of solids
82.Natural water circulation, by convection in water tube boilers, with increase in pressure of boiler
increases
decreases
remains unaffected
first increases and then decreases
first decreases and then increases.
ANSWER : : decreases
83.Which is not the correct statement about moisture in coal
inherent moisture and surface moisture are different things
in some coals moisture may be present upto 40%
some moisture in coal helps in better burning which is not possible with completely dry coal
it increases thermal efficiency
moisture in coal is removed before firing by heating it with hot air.
ANSWER : : it increases thermal efficiency
84.Film boiling occurs at
very low pressure
atmospheric pressures
medium pressures
very high pressures
none of the above.
ANSWER : : very high pressures
85.Relative percentage of heat absorbed through the heat transfer of (i) furnace water wall, (ii) boiler bank, (Hi) superheated, (iv) economizer, (v) air heater of a typical boiler of 200 MW capacity would be of the order of
48:20:15:7:10
10:7:15:20:48
20:48:7:15:10
7:15:20:10:48
48:15:10:7:20.
ANSWER : : 48:20:15:7:10
86.The size of a boiler drum in pulverized fuel fired boiler,as its size and capacity, (steam pressure and flow ratings) increase
increases
decreases
remains unchanged
increases/decreases depending on steam temperature requirements
unpredictable.
ANSWER : : decreases
87.The condition of steam in boiler drum is always
dry
wet
saturated
supersaturated
superheated.
ANSWER : : wet
88.In water wall furnace, the heat is transferred to the water-walls by
convection
radiation
conduction
radiation and conduction
radiation and convection.
ANSWER : : radiation
89.In ordered obtain superheated steam, a superheater is added in an existing boiler. As as result, furnace vacuum will
remain unaffected
improve
worsen
may improve/worsen depending on size
unpredictable.
ANSWER : : worsen
90.The balanced draft furnace is one using
induced draft fan and chimney
induced draft fan and forced draft fan
forced draft fan and chimney
any one of the above
none of the above.
ANSWER : s: b
91.De aeration of feed water is carried out because it reduces
cavitation of .boiler feed pumps
corrosion caused by oxygen
heat transfer coefficient
pH value of water
weight of water to be handled.
ANSWER : : corrosion caused by oxygen
92.The feed check valve is used in order to
regulate flow of boiler water
check level of water in boiler drum
recirculate unwanted feed water
allow high pressure feed water to flow to drum and not allow reverse flow to take place
none of the above.
ANSWER : : allow high pressure feed water to flow to drum and not allow reverse flow to take place
93.During storage, the heating value of coal
increases
decreases
remains constant
may increase or decrease depending upon the method of storage
none of the above.
ANSWER : : decreases
94.The steam temperature with increase in load in case of a boiler fitted with radiation superheated
increases
decreases
remains unaffected
first increases and then decreases
unpredictable.
ANSWER : : decreases