,Q1 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A high-pressure steam boiler operates at 850 psig with a feedwater temperature of
220°F. The blowdown rate is 5% of the feedwater flow. If the boiler water total
dissolved solids (TDS) concentration is 3500 ppm and the maximum allowable
TDS for the boiler is 3000 ppm, what is the minimum required blowdown rate (as a
percentage of feedwater flow) to maintain the TDS at or below the limit? Assume
steady-state and no other losses.
A. 3.5%
B. 4.0%
C. 5.0%
D. 6.0% CORRECT
RATIONALE: Using the mass balance: Feedwater TDS (assume negligible) plus blowdown TDS
equals dissolved solids in. For steady-state, blowdown rate % = (Feedwater TDS / (Boiler TDS
limit - Feedwater TDS)) * 100. If feedwater TDS is 150 ppm, then required blowdown =
(150/(3000-150))*100 = 5.26%, so 6.0% is the minimum among options. At 5%, TDS would rise
above 3000 ppm. Lower rates are insufficient, and 3.5% and 4.0% are too low.
Q2 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A low-water cutoff device on a steam boiler is being tested. The boiler is operating
at 150 psig. According to ASME CSD-1 and modern practice, what is the correct
procedure for testing a low-water cutoff with a blowdown valve?
A. Blowdown the cutoff while the burner is firing to ensure it trips under load.
B. Close the steam stop valve, drain the boiler to just below the cutoff level, and confirm the
burner shuts off.
C. Open the blowdown valve to simulate low water, confirm the burner shuts off, then close the
valve and verify the burner restarts automatically. CORRECT
D. Isolate the cutoff, test the electrical continuity, and replace the device if it fails.
RATIONALE: ASME CSD-1 requires testing low-water cutoff by blowing down the device while
the boiler is in normal operation; the burner should shut off and then restart after the water level
is restored. Option A is incorrect because the burner should not be firing during the test to avoid
damage. Option B is too drastic and not the standard test. Option D only tests electrical
continuity, not the actual water level sensing function.
Page 2
,Q3 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler operator notices that the stack temperature has increased by 75°F over a
week while the steam load has remained constant. Which of the following is the
most likely cause?
A. Decreased excess air causing incomplete combustion
B. Scale buildup on the waterside of the boiler tubes CORRECT
C. A leak in the economizer allowing flue gas to bypass
D. An increase in ambient air temperature
RATIONALE: Scale on the waterside acts as an insulator, reducing heat transfer and causing
higher flue gas exit temperatures. Decreased excess air would lower stack temperature (more
complete combustion). An economizer leak would likely cause a drop in stack temperature due to
heat absorption. Ambient temperature changes affect the stack temperature but not to the extent
of a 75°F rise with constant load.
Q4 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
When performing a hydrostatic test on a high-pressure boiler, what is the
minimum test pressure required by ASME Code?
A. 1.25 times the maximum allowable working pressure (MAWP)
B. 1.5 times the maximum allowable working pressure (MAWP) CORRECT
C. The maximum allowable working pressure (MAWP)
D. 1.1 times the maximum allowable working pressure (MAWP)
RATIONALE: ASME Boiler and Pressure Vessel Code Section I requires hydrostatic test
pressure to be at least 1.5 times the MAWP for power boilers. Option A (1.25) is for pressure
vessels in Section VIII. Option C is not sufficient. Option D is not a standard factor.
Page 3
, Q5 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler burns natural gas with 15% excess air. The flue gas analysis shows 3%
O2. If the burner is adjusted to reduce excess air to 10%, what will happen to the
O2 level in the flue gas?
A. It will increase to about 4%
B. It will decrease to about 2% CORRECT
C. It will remain at 3%
D. It will decrease to about 1%
RATIONALE: O2 in flue gas is directly related to excess air. For natural gas, 15% excess air
yields about 3% O2. Reducing excess air to 10% reduces O2 to roughly 2%. The relationship is
approximately linear: O2% (excess air %)*0.2 for typical fuels. Thus, 10% excess air gives about
2% O2. Option A is opposite, C is no change, D too low.
Q6 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler operator is preparing to take a boiler out of service for an extended
period. What is the recommended method for wet storage?
A. Fill the boiler completely with deaerated water and maintain a slight positive pressure.
B. Drain the boiler completely and leave it open to the atmosphere.
C. Fill with water containing excess sulfite and maintain pH above 11. CORRECT
D. Store dry with desiccant and seal all openings.
RATIONALE: Wet storage involves filling the boiler with treated water containing excess sulfite to
scavenge oxygen and maintaining high pH to prevent corrosion. Option A lacks chemical
treatment. Option B is dry storage, not wet. Option D is dry storage with desiccant.
Page 4
COMBUSTION AND REDUCE LOSSES
A high-pressure steam boiler operates at 850 psig with a feedwater temperature of
220°F. The blowdown rate is 5% of the feedwater flow. If the boiler water total
dissolved solids (TDS) concentration is 3500 ppm and the maximum allowable
TDS for the boiler is 3000 ppm, what is the minimum required blowdown rate (as a
percentage of feedwater flow) to maintain the TDS at or below the limit? Assume
steady-state and no other losses.
A. 3.5%
B. 4.0%
C. 5.0%
D. 6.0% CORRECT
RATIONALE: Using the mass balance: Feedwater TDS (assume negligible) plus blowdown TDS
equals dissolved solids in. For steady-state, blowdown rate % = (Feedwater TDS / (Boiler TDS
limit - Feedwater TDS)) * 100. If feedwater TDS is 150 ppm, then required blowdown =
(150/(3000-150))*100 = 5.26%, so 6.0% is the minimum among options. At 5%, TDS would rise
above 3000 ppm. Lower rates are insufficient, and 3.5% and 4.0% are too low.
Q2 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A low-water cutoff device on a steam boiler is being tested. The boiler is operating
at 150 psig. According to ASME CSD-1 and modern practice, what is the correct
procedure for testing a low-water cutoff with a blowdown valve?
A. Blowdown the cutoff while the burner is firing to ensure it trips under load.
B. Close the steam stop valve, drain the boiler to just below the cutoff level, and confirm the
burner shuts off.
C. Open the blowdown valve to simulate low water, confirm the burner shuts off, then close the
valve and verify the burner restarts automatically. CORRECT
D. Isolate the cutoff, test the electrical continuity, and replace the device if it fails.
RATIONALE: ASME CSD-1 requires testing low-water cutoff by blowing down the device while
the boiler is in normal operation; the burner should shut off and then restart after the water level
is restored. Option A is incorrect because the burner should not be firing during the test to avoid
damage. Option B is too drastic and not the standard test. Option D only tests electrical
continuity, not the actual water level sensing function.
Page 2
,Q3 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler operator notices that the stack temperature has increased by 75°F over a
week while the steam load has remained constant. Which of the following is the
most likely cause?
A. Decreased excess air causing incomplete combustion
B. Scale buildup on the waterside of the boiler tubes CORRECT
C. A leak in the economizer allowing flue gas to bypass
D. An increase in ambient air temperature
RATIONALE: Scale on the waterside acts as an insulator, reducing heat transfer and causing
higher flue gas exit temperatures. Decreased excess air would lower stack temperature (more
complete combustion). An economizer leak would likely cause a drop in stack temperature due to
heat absorption. Ambient temperature changes affect the stack temperature but not to the extent
of a 75°F rise with constant load.
Q4 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
When performing a hydrostatic test on a high-pressure boiler, what is the
minimum test pressure required by ASME Code?
A. 1.25 times the maximum allowable working pressure (MAWP)
B. 1.5 times the maximum allowable working pressure (MAWP) CORRECT
C. The maximum allowable working pressure (MAWP)
D. 1.1 times the maximum allowable working pressure (MAWP)
RATIONALE: ASME Boiler and Pressure Vessel Code Section I requires hydrostatic test
pressure to be at least 1.5 times the MAWP for power boilers. Option A (1.25) is for pressure
vessels in Section VIII. Option C is not sufficient. Option D is not a standard factor.
Page 3
, Q5 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler burns natural gas with 15% excess air. The flue gas analysis shows 3%
O2. If the burner is adjusted to reduce excess air to 10%, what will happen to the
O2 level in the flue gas?
A. It will increase to about 4%
B. It will decrease to about 2% CORRECT
C. It will remain at 3%
D. It will decrease to about 1%
RATIONALE: O2 in flue gas is directly related to excess air. For natural gas, 15% excess air
yields about 3% O2. Reducing excess air to 10% reduces O2 to roughly 2%. The relationship is
approximately linear: O2% (excess air %)*0.2 for typical fuels. Thus, 10% excess air gives about
2% O2. Option A is opposite, C is no change, D too low.
Q6 ANALYZE BOILER EFFICIENCY AND HEAT TRANSFER PRINCIPLES TO OPTIMIZE
COMBUSTION AND REDUCE LOSSES
A boiler operator is preparing to take a boiler out of service for an extended
period. What is the recommended method for wet storage?
A. Fill the boiler completely with deaerated water and maintain a slight positive pressure.
B. Drain the boiler completely and leave it open to the atmosphere.
C. Fill with water containing excess sulfite and maintain pH above 11. CORRECT
D. Store dry with desiccant and seal all openings.
RATIONALE: Wet storage involves filling the boiler with treated water containing excess sulfite to
scavenge oxygen and maintaining high pH to prevent corrosion. Option A lacks chemical
treatment. Option B is dry storage, not wet. Option D is dry storage with desiccant.
Page 4
