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1. A boiler has an MAWP of 150 psi and a safety valve set at 100 psi with a 3" valve
disc. What is the total force needed to open the safety valve against opposing
spring force?
A. 500 lbs
B. 708 lbs
C. 900 lbs
D. 1,200 lbs
Rationale: Using TF = PSI × (diameter × diameter) × 0.7854: 100 × (3 × 3) × 0.7854
= 706.86 ≈ 708 lbs.
2. What is the function of a dry pipe in a boiler?
A. To increase steam pressure
B. To remove moisture from a steam drum
C. To regulate feedwater flow
D. To measure water level
Rationale: A dry pipe collects steam from multiple points across the drum and
helps separate/remove entrained moisture before steam exits the boiler.
3. A safety valve nameplate shows an orifice opening of 1.5 inches with a set
pressure of 98 psig. What is the total force acting on the valve?
,A. 100 lbs
B. 173 lbs
C. 220 lbs
D. 300 lbs
Rationale: TF = 98 × (1.5 × 1.5) × 0.7854 ≈ 173 lbs.
4. True or False: The steam pressure on a safety valve acts upon the upper side of
the valve disc, which is held down on the seat by a spring that pushes down.
A. True
B. False
Rationale: Steam pressure actually acts on the underside of the valve disc, pushing
upward against the downward force of the spring — the reverse of the statement
given.
5. As the firing rate increases in a boiler equipped with a convection-type
superheater, the steam temperature:
A. Decreases
B. Increases
C. Remains unchanged
D. Fluctuates unpredictably
Rationale: A convection superheater's heat transfer depends on hot gas flow past
the tubes; higher firing rates increase gas flow/temperature, raising the
superheated steam temperature.
6. On a steam boiler, what device must activate to prevent the generation of
steam pressure greater than the maximum working pressure?
,A. The feedwater regulator
B. The high steam pressure limit control
C. The low water fuel cutoff
D. The blowdown valve
Rationale: The high steam pressure limit control specifically shuts down firing
when pressure approaches the maximum allowable working pressure, serving as a
key safety control.
7. How often should safety valves on a power boiler be test blown?
A. Once a year
B. At least once a month
C. Once a week
D. Once every 6 months
Rationale: Regular monthly testing ensures safety valves remain functional and
haven't become stuck or fouled, which is critical for boiler safety.
8. Before a hydrostatic test is performed on a boiler, each safety valve should be:
A. Removed completely from the boiler
B. Held to its seat by means of a testing clamp
C. Left in normal operating condition
D. Set to a lower pressure than normal
Rationale: Clamping the safety valve prevents it from lifting during the hydrostatic
test, which uses pressures exceeding the valve's normal set point.
9. A boiler produces 500 psi steam at 625°F. Normal saturated steam condition at
this pressure is 467°F. What is the degree of superheat?
, A. 100°F
B. 158°F
C. 200°F
D. 467°F
Rationale: Degree of superheat = actual temperature − saturation temperature =
625°F − 467°F = 158°F.
10. Steam at 100 psi and 400°F would be considered:
A. Saturated steam
B. Superheated steam
C. Wet steam
D. Subcooled liquid
Rationale: Since saturated steam at 100 psi corresponds to 338°F, steam at 400°F
(above saturation temperature) at the same pressure is superheated.
11. What type of boiler should never be subjected to an accumulation test?
A. A boiler with a low water cutoff
B. A boiler equipped with a superheater
C. A firetube boiler
D. A boiler with multiple safety valves
Rationale: Accumulation tests involve blocking normal steam outlets to test safety
valve capacity, which risks overheating and damaging superheater tubes if steam
flow through them is interrupted.
12. Water hammer (or other fluid hammer) is a dangerous condition that could
result in: