LOUISIANA (NEW ORLEANS) SECOND CLASS STATIONARY BOILERS
661-LA EXAM STUDY GUIDE: TROUBLESHOOTING & FAULT DIAGNOSIS
100% CORRECT!!
TABLE OF CONTENT
Subtopic 1: Pressure Fluctuations and Control Hunting (Questions 1-6)
Subtopic 2: Flame Failures and Ignition Faults (Questions 7-12)
Subtopic 3: Scaling, Water Treatment Failures, and Heat (Questions 13-18)
Transfer Issues
Subtopic 4: Mechanical Faults, Pumps, and Valve (Questions 19-24)
Malfunctions
Subtopic 5: Control System Errors, Interlocks, and (Questions 25-30)
Electrical Failures
Subtopic 1: Pressure Fluctuations and Control Hunting
Question 1
An operator observes that a natural gas-fired steam boiler's pressure gauge swings
rapidly up and down by 15 psi, and the burner continuously modulates back and forth
between high and low fire without ever stabilizing. What is the most likely cause of this
control "hunting"?
A. The pressure control differential or proportional band is set too narrow, or the sensing
line has a slight restriction or trapped condensate.
B. The boiler is operating at absolute peak efficiency.
C. The bottom blowdown valves are left wide open.
,D. The stack damper is permanently stuck open.
Correct Answer: A. The pressure control differential or proportional band is set too
narrow, or the sensing line has a slight restriction or trapped condensate.
Rationale: When pressure controls have too narrow a deadband or differential, the
controller over-responds to minor pressure changes, causing constant oscillation
(hunting). Restricted sensing lines also delay signal transmission, causing control
instability.
Question 2
During high steam demand, a boiler's operating pressure drops precipitously despite the
burner firing at 100% capacity, and the water level in the gauge glass surges upward
dramatically. What phenomenon is occurring, and how should it be diagnosed?
A. The boiler is experiencing severe priming or foaming caused by high total dissolved
solids (TDS), which tricks the operator into seeing a false high water level while steam
pressure collapses.
B. The safety valves are stuck in the closed position.
C. The fuel gas meter has frozen solid.
D. The combustion blower is running in reverse.
Correct Answer: A. The boiler is experiencing severe priming or foaming caused by high
total dissolved solids (TDS), which tricks the operator into seeing a false high water
level while steam pressure collapses.
Rationale: High TDS causes foaming and surging. The bubbles displace water and
create a false high level in the glass, while the actual water mass carries over into the
steam lines, collapsing system pressure and risking equipment damage.
Question 3
An operator notices that steam pressure creeps slowly upward past the high-limit
operating setpoint, yet the burner continues to fire instead of shutting down. What
troubleshooting step should be taken immediately?
A. Manually trip the burner using the emergency fuel shutoff switch, then test and
inspect the pressure control switches and microswitches for electrical welding or failure.
, B. Open all chemical feed valves wide.
C. Open the gauge glass drain valve.
D. Close the main steam stop valve completely.
Correct Answer: A. Manually trip the burner using the emergency fuel shutoff switch,
then test and inspect the pressure control switches and microswitches for electrical
welding or failure.
Rationale: When primary and secondary pressure controls fail to stop firing, manual
intervention is mandatory to prevent an overpressure event. Control contacts can weld
shut over time, requiring replacement.
Question 4
A boiler system experiences sudden, wide pressure spikes whenever a large auxiliary
steam load valves open downstream in the plant. What is the proper diagnosis of this
issue?
A. The boiler capacity is lagging behind instantaneous load changes, or the pressure
control modulation rate is adjusted too slowly to anticipate large demand spikes.
B. The feedwater pump check valve is installed backward.
C. The room ventilation louvers are closed too tight.
D. The low-water cutoff float is stuck in position.
Correct Answer: A. The boiler capacity is lagging behind instantaneous load changes,
or the pressure control modulation rate is adjusted too slowly to anticipate large demand
spikes.
Rationale: Sudden load increases draw steam faster than the boiler can generate it,
causing pressure drops followed by over-correction spikes if tuning parameters (PID)
are improperly set.
Question 5
661-LA EXAM STUDY GUIDE: TROUBLESHOOTING & FAULT DIAGNOSIS
100% CORRECT!!
TABLE OF CONTENT
Subtopic 1: Pressure Fluctuations and Control Hunting (Questions 1-6)
Subtopic 2: Flame Failures and Ignition Faults (Questions 7-12)
Subtopic 3: Scaling, Water Treatment Failures, and Heat (Questions 13-18)
Transfer Issues
Subtopic 4: Mechanical Faults, Pumps, and Valve (Questions 19-24)
Malfunctions
Subtopic 5: Control System Errors, Interlocks, and (Questions 25-30)
Electrical Failures
Subtopic 1: Pressure Fluctuations and Control Hunting
Question 1
An operator observes that a natural gas-fired steam boiler's pressure gauge swings
rapidly up and down by 15 psi, and the burner continuously modulates back and forth
between high and low fire without ever stabilizing. What is the most likely cause of this
control "hunting"?
A. The pressure control differential or proportional band is set too narrow, or the sensing
line has a slight restriction or trapped condensate.
B. The boiler is operating at absolute peak efficiency.
C. The bottom blowdown valves are left wide open.
,D. The stack damper is permanently stuck open.
Correct Answer: A. The pressure control differential or proportional band is set too
narrow, or the sensing line has a slight restriction or trapped condensate.
Rationale: When pressure controls have too narrow a deadband or differential, the
controller over-responds to minor pressure changes, causing constant oscillation
(hunting). Restricted sensing lines also delay signal transmission, causing control
instability.
Question 2
During high steam demand, a boiler's operating pressure drops precipitously despite the
burner firing at 100% capacity, and the water level in the gauge glass surges upward
dramatically. What phenomenon is occurring, and how should it be diagnosed?
A. The boiler is experiencing severe priming or foaming caused by high total dissolved
solids (TDS), which tricks the operator into seeing a false high water level while steam
pressure collapses.
B. The safety valves are stuck in the closed position.
C. The fuel gas meter has frozen solid.
D. The combustion blower is running in reverse.
Correct Answer: A. The boiler is experiencing severe priming or foaming caused by high
total dissolved solids (TDS), which tricks the operator into seeing a false high water
level while steam pressure collapses.
Rationale: High TDS causes foaming and surging. The bubbles displace water and
create a false high level in the glass, while the actual water mass carries over into the
steam lines, collapsing system pressure and risking equipment damage.
Question 3
An operator notices that steam pressure creeps slowly upward past the high-limit
operating setpoint, yet the burner continues to fire instead of shutting down. What
troubleshooting step should be taken immediately?
A. Manually trip the burner using the emergency fuel shutoff switch, then test and
inspect the pressure control switches and microswitches for electrical welding or failure.
, B. Open all chemical feed valves wide.
C. Open the gauge glass drain valve.
D. Close the main steam stop valve completely.
Correct Answer: A. Manually trip the burner using the emergency fuel shutoff switch,
then test and inspect the pressure control switches and microswitches for electrical
welding or failure.
Rationale: When primary and secondary pressure controls fail to stop firing, manual
intervention is mandatory to prevent an overpressure event. Control contacts can weld
shut over time, requiring replacement.
Question 4
A boiler system experiences sudden, wide pressure spikes whenever a large auxiliary
steam load valves open downstream in the plant. What is the proper diagnosis of this
issue?
A. The boiler capacity is lagging behind instantaneous load changes, or the pressure
control modulation rate is adjusted too slowly to anticipate large demand spikes.
B. The feedwater pump check valve is installed backward.
C. The room ventilation louvers are closed too tight.
D. The low-water cutoff float is stuck in position.
Correct Answer: A. The boiler capacity is lagging behind instantaneous load changes,
or the pressure control modulation rate is adjusted too slowly to anticipate large demand
spikes.
Rationale: Sudden load increases draw steam faster than the boiler can generate it,
causing pressure drops followed by over-correction spikes if tuning parameters (PID)
are improperly set.
Question 5
