Power Engineering 4th Class - A12
Questions and Answers
Natural draft is produced in a boiler furnace when:
a. Hot flue gases condense
b. Gases in the stack have more mass than an equal column of outside air
c. Gases in the stack have less mass than an equal column of outside air
A
d. Hot flue gases contract so that each cubic meter has more mass - ANS c
VI
If the power is cut off to an automatic gas valve, the valve will:
a. Open widely
TU
b. De-pressurize the gas train
c. Close immediately
d. Close slowly - ANS c
IS
When draft is produced by natural means:
a. Cooler air surrounding the boiler increases draft
OM
b. The diameter of the stack will improve the draft
c. A short stack is preferred over a tall one
d. Fans control the flue gas flow - ANS a
The Hartford loop will:
NA
a. Replace the feedwater check valve
b. Prevent boiler water level from going below the lowest safe water level
c. Ensure continuous circulation of a hot water system
JP
d. Only be installed on multiple-boiler systems - ANS b
In a float type low water fuel cutoff, the main purpose of the mercury switch is to:
a. Open the burner circuit when the level is low
b. Activate a low water alarm
c. Close the burner circuit when the level is low
d. Open the burner circuit when the level is high - ANS a
,When an oil burner is not in use, it should be removed from the furnace; otherwise the
heat may cause:
a. Carbon to accumulate in the burner
b. The rotary cup to slow down
c. The burner to corrode
d. The fuel to evaporate - ANS a
Gas burners for heating boilers can be divided into two general classes:
A
a. Pre and after mix
b. In-shot and up-shot
VI
c. Refractory and ribbon-type
d. Mixing and non-mixing - ANS a
TU
Blowoff valves are used to:
a. Reduce the steam pressure on the boiler
b. Drain or remove sediment from the continuous blowdown
IS
c. Drain or remove sediment from the bottom of the boiler
d. Drain or remove sediment from the bottom of the steam drum - ANS c
OM
On a boiler blowoff system, a valve that requires at least five 360° turns of the operating
mechanism to change from fully open to fully closed is known as:
a. an isolating valve
b. a slow opening valve
NA
c. a non-return valve
d. a quick opening valve - ANS b
A solenoid type fuel valve;
JP
a. Closes slowly
b. Always opens rapidly
c. Is held closed by electrical current
d. Is held closed by gas action - ANS d
Single element feed water control systems are very efficient in maintaining the boiler
water level when:
, a. Load demands are low
b. Steady or slowly fluctuating steam demand
c. The boiler is a fire tube boiler
d. The boiler has a large water capacity - ANS b
The result of a condensate receiver that is too small could be:
a. High boiler water level
b. Overflowing of the condensate receiver
c. Loss of make-up water
A
d. Low make-up water flow rates - ANS b
VI
In an atmospheric fluidized bed boiler, the combustion air pressure is typically 2.5 kPa
at the FD fan, 1.6 kPa of water at the base of the active bed and _____ at the top of the
combustion mass:
TU
a. Atmospheric pressure
b. Negative pressure
c. Boiler pressure
IS
d. Negative 16 cm of water - ANS a
A common continuous blowdown rate on many boilers is approximately:
OM
a. 10% of steaming rate
b. 5% of steaming rate
c. 1% of steaming rate
d. 3% of steaming rate - ANS c
NA
One way to increase natural draft is to:
a. Decrease the amount of excess air
b. Install a higher chimney
JP
c. Increase the primary air flow
d. Incorporate a forced draft fan - ANS b
During combustion in a boiler furnace, black smoke may be caused by:
a. Insufficient combustion air
b. Flyash in the flue gas
c. Too much nitrogen in the air
Questions and Answers
Natural draft is produced in a boiler furnace when:
a. Hot flue gases condense
b. Gases in the stack have more mass than an equal column of outside air
c. Gases in the stack have less mass than an equal column of outside air
A
d. Hot flue gases contract so that each cubic meter has more mass - ANS c
VI
If the power is cut off to an automatic gas valve, the valve will:
a. Open widely
TU
b. De-pressurize the gas train
c. Close immediately
d. Close slowly - ANS c
IS
When draft is produced by natural means:
a. Cooler air surrounding the boiler increases draft
OM
b. The diameter of the stack will improve the draft
c. A short stack is preferred over a tall one
d. Fans control the flue gas flow - ANS a
The Hartford loop will:
NA
a. Replace the feedwater check valve
b. Prevent boiler water level from going below the lowest safe water level
c. Ensure continuous circulation of a hot water system
JP
d. Only be installed on multiple-boiler systems - ANS b
In a float type low water fuel cutoff, the main purpose of the mercury switch is to:
a. Open the burner circuit when the level is low
b. Activate a low water alarm
c. Close the burner circuit when the level is low
d. Open the burner circuit when the level is high - ANS a
,When an oil burner is not in use, it should be removed from the furnace; otherwise the
heat may cause:
a. Carbon to accumulate in the burner
b. The rotary cup to slow down
c. The burner to corrode
d. The fuel to evaporate - ANS a
Gas burners for heating boilers can be divided into two general classes:
A
a. Pre and after mix
b. In-shot and up-shot
VI
c. Refractory and ribbon-type
d. Mixing and non-mixing - ANS a
TU
Blowoff valves are used to:
a. Reduce the steam pressure on the boiler
b. Drain or remove sediment from the continuous blowdown
IS
c. Drain or remove sediment from the bottom of the boiler
d. Drain or remove sediment from the bottom of the steam drum - ANS c
OM
On a boiler blowoff system, a valve that requires at least five 360° turns of the operating
mechanism to change from fully open to fully closed is known as:
a. an isolating valve
b. a slow opening valve
NA
c. a non-return valve
d. a quick opening valve - ANS b
A solenoid type fuel valve;
JP
a. Closes slowly
b. Always opens rapidly
c. Is held closed by electrical current
d. Is held closed by gas action - ANS d
Single element feed water control systems are very efficient in maintaining the boiler
water level when:
, a. Load demands are low
b. Steady or slowly fluctuating steam demand
c. The boiler is a fire tube boiler
d. The boiler has a large water capacity - ANS b
The result of a condensate receiver that is too small could be:
a. High boiler water level
b. Overflowing of the condensate receiver
c. Loss of make-up water
A
d. Low make-up water flow rates - ANS b
VI
In an atmospheric fluidized bed boiler, the combustion air pressure is typically 2.5 kPa
at the FD fan, 1.6 kPa of water at the base of the active bed and _____ at the top of the
combustion mass:
TU
a. Atmospheric pressure
b. Negative pressure
c. Boiler pressure
IS
d. Negative 16 cm of water - ANS a
A common continuous blowdown rate on many boilers is approximately:
OM
a. 10% of steaming rate
b. 5% of steaming rate
c. 1% of steaming rate
d. 3% of steaming rate - ANS c
NA
One way to increase natural draft is to:
a. Decrease the amount of excess air
b. Install a higher chimney
JP
c. Increase the primary air flow
d. Incorporate a forced draft fan - ANS b
During combustion in a boiler furnace, black smoke may be caused by:
a. Insufficient combustion air
b. Flyash in the flue gas
c. Too much nitrogen in the air
