ML19261B191

LER 79-001/03L-0 on 790104:during Monthly Operability Test, Inlet Air Heater on a Standby Gas Treatment Sys Was Found Inoperable.Caused by Setpoint Drift of Flow Switch 1/2-7541-8A

ML19261B191
Person / Time
Site:	Quad Cities
Issue date:	01/25/1979
From:	Kooi M COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19261B184	List: ML19261B183 ML19261B191
References
LER-79-001-03L-01, LER-79-1-3L-1, NUDOCS 7902140151
Download: ML19261B191 (2)

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EVENT DESCRIPTION AND PRO 3ABLE CONSEQUENCES h '

O 2 While performing monthly operability test, procedure QOS 7500-5, it was discovered l

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42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i o l The cause of the failure was due to setpoint dri f t of flow switch 1/2-7541-8A. This I i i switch actuates the heater when flow is present in the SBGT train. The flow swi tch I was calibrated and the "A" SBGT was tested satisfactorily. The heater itself was [

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1. LER NUMBER: LER/R0 79-01/03L-0 ll. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station 111. FACILITY NAME: Unit Two IV. DOCKET NUMBER: 050-265 V. EVENT DESCRIPTION:

On January 4, 1979, at 10:30 a.m. , while performing the monthly operability test, procedure QOS 7500-5, it was discovered that the inlet air heater on "A" Standby Gas Treatment (SBGT)

System was r.ot operating. The "A" SBGT System was immediately declarcJ inoperable. Since the operability test on "B" SBGT System had been completed just prior to this event, the require-ments of Technical Specification 3.7.B.I.a. were satisfied.

Immediate investigation of the failure revealed that temperature switch 1/2-7541-11A in the heater control circuit had tripped.

The switch was reset and the operability test on "A" SBGT System was successfully completed. At 1:00 p.m. the next day, "A" SBGT System was put on and the heater again failed to operate. An operability test on "B" SBGT System was subsequently completed and an investigation of the failure was begun.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

Both SBGT Systems had been proven operable on December 4, 1978. The redundant "B" SBGT System was operable during this occurrence. Also, the filters, demister, fan, and dampers for the "A" SBGT train were operable. Consequently no adverse safety implications were presented by this event.

Vll. CAUSE The cause of the failure was due to setpoint drif t of flow switch 1/2-7541-8A. This switch actuates the "A" SBGT system heater when flow is present in the SBGT train. The flow switch had failed in the closed position, thus energizing the heater. Since no cooling flow was available, temperature switch 1/2-7541-11A then tripped the heater when the 200 F0 setpoint temperature was reached. When the temperature switch was reset and flow was initiated, the heater remained on until the air flow ceased and the temperature switch again tripped the heater due to high temperature. Flow switch 1/2-7541-8A is model number DA-5333 manufactured by Mercold Corp.

Vill. CORRECTIVE ACTION:

The flow switch was calibrated and the "A" SBGT was tested satisfactorily. Since this is the first failure of this type, thus corrective action is considered sufficient.