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Exams > 2020 Q65 — Fire Pump Start on Loss of AC

2020 Q65 — Fire Pump Start on Loss of AC

⚠️ DRAFT
Q65 — Fire Pump Start on Loss of AC 086000A1.05 (2.9)
Given:
  • Unit 2 is at 100% Power.

The following sequence of events occurs:
  • OHA A-15, FIRE PMP 1/2 RUN in alarm
  • OHA A-23, FIRE PUMP 1/2 TRBL in alarm.
  • BOTH Fire Pumps are running.
  • NO other Fire Protection System alarms are present.
  • Fire protection reports NO fire system actuations.
  • Fire main header pressure is 135 psig and stable.

Which ONE of the following describes the cause for the above conditions?
A. Fire Protection Jockey Pump tripped.
B. Major Fire Protection System pipe rupture.
C. Loss of Normal AC power to BOTH Fire Pump Battery Chargers.
D. A momentary (1 second) drop in Fire Protection header pressure to 70 psig.
▶ Show Answer & Explanation
✓ C. Correct. The diesel driven fire pumps are normally aligned in standby and normally start on low header pressure signals of <85# and time delayed <75# respectively. But the system configuration also includes an independent battery that will automatically start the fire pumps during a loss of normal AC power.
✗ A. Plausible because the Jockey Pump normally maintains fire protection header pressure between 110-120 psig and the candidate may believe that the trip of the jockey pump is an automatic start signal for the fire pumps.
✗ B. Plausible in that since the fire pumps start at <85# and <70# with a time delay that a large pipe rupture could have caused system pressure to lower to the start setpoints, but that the pumps were presently able to maintain 135# based on the size of the leak.
✗ D. Plausible in that since the fire pumps start at <85# and <70# with a time delay that a large pipe rupture could have caused system pressure to lower to the start setpoints. Incorrect as the start for the #2 Fire Pump includes a time delay and therefore a momentary (1 sec) pressure drop would not have started both pumps.
Ref: NOS05FIRPRO-09, Fire Protection System; S2.OP-AB.FP-0001(Q), Fire Protection System Malfunction | LO: ELO 7 | Source: Bank – Salem Vision Database | Cognitive: Comprehension

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