ML19323F819

Final Const Deficiency Rept 5 Re Impeller Shaft Retaining Mechanism Failure in Low Presssure Safety Injection Pumps, Discovered on 780216.Exact Cause Not Known But May Be Due to Gasket Deterioration.Locking Devices Modified

ML19323F819
Person / Time
Site:	Waterford
Issue date:	05/21/1980
From:	Crnich J, Hart J, Milhiser R LOUISIANA POWER & LIGHT CO.
To:
Shared Package
ML19323F812	List: ML19323F811 ML19323F819
References
NUDOCS 8005290503
Download: ML19323F819 (3)

Text

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A V -

J LOUISIANA POWER & LIGHT COMPANY WATERFORD SES UNIT No 3 Final Repcrt of Significant Construction Deficiency No 5 -

t LPSI Pumps Impeller Shaf t Retaining Mechanism Failure Reviewed by \- -

) / O CrnicTi - Site Manager Reviewed by / #

, 4- / .

R J Milhl%er - Project Superintendent A . f Reviewed by M [4 C 2p-FD J Hpt - Project Liceryting Tngineer

/

Reviewed by '

[ d/-20 R A Hartnett - Q A Site Supervisor -

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May 21, 1980 f

8005290 703 ._ _

?INAL REPORT SIGNIFICANT CONSTRUCTION DEFICIENCY NO 5 LPSI PUMPS IMPELLER SHAFT RETAINING MECHANISM FAILURE INTRODUCTION This report is submitted pursuant to 10CFR50.55(e)(3) . It describes a /

deficiency in the Low Pressure Safety Injection Pumps "A" and "B" supplied for use in the Waterford Unit 3 Safety Injection System.

BACKGROUND By telecon dated 7-18-78, Louisiana Power & Light Company confirmed noti-fication to the NRC concerning a deficiency that had been identified during preoperational testing at Arkansas Power & Light Company's Arkansas Nucle ar One - Unit 2 in Low Pressure Safety Injection Pumps manufactured by Inger-soll Rand. This deficiency involved the pump impeller locking devices (re-taining washer, jam nut, and cap nut), which might not perform their func-tion, creating the possibility of causing damage resulting from a loose im-peller.

DESCRIPTION OF DEFICIENCY On February 16, 1978, in anticipation of initiating shutdown ecoling during preoperational testing at Arkansas !iuclear One - Unit 2, (ANO-2) the "A" LPSI Pump was started. Within a short period of time excessive noise and vibration was detected and the pump was secured. The "B" Pump was then started. Here, also, fn a short period of time excessive noise was noted and this pump was stopped. These pumps are Ingersoll Rand 8 x 20 WD Pumps.

When the spool pieces in the suction piping of both pumps were removed, it was found that hardware was missing. Each impeller is keyed to its shaft and then retained by a washer, jam nut and cap nut. These washers and nuts were no longer on the shaf ts of either pump. It was apparent that the noise experienced resulted from the washers and nuts slamming around in the suc-tion piping. The vibration in the "A" pump apparently stemmed from the re- ,

taining washers wedging between two impeller vanes. )

Subsequent inspection of the ANO-2 operating logs indicated that these pumps had been initially operated under the guidance of an Ingersoll Rand service i engineer; had been checked for correct rotation, and had significant hours j of operation. The "A" pump had at least 499 hours0.00578 days <br />0.139 hours <br />8.250661e-4 weeks <br />1.898695e-4 months <br /> of operation and the "B" I pump, 1231 hours0.0142 days <br />0.342 hours <br />0.00204 weeks <br />4.683955e-4 months <br />. It was also noted that these pumps had numerous starts I and stops while building up these hours of operation.

1 Upon complete disassembly of the pumps, it was found that contact had been I made between the impeller wear rings and the pump case wear rings. There  !

are a total of four such mating wear rings in the two pumps and scoring oc-curred in all four cases. The impellers also showed signs of peening where the loose nuts and washers apparently contacted the impeller at a suction velocity.

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The exact cause of failure is not known. The design was such that the nuts could back off and drop off. Once they fell free, so did the washers. The impellers remained keyed to their shaf ts with no indication of axial move-ment. Ingersoll Rand does not know the cause of failure, but speculates that earlier operational periods of vibration could have been the cause. Combus-tion Engineecing concurs with this. C-E further speculates that a gasketing design feature may have been a possible cause. The torque applied to the locking hardward compresses a fibrous gasket. This gasket could have dete-riorated with time, thereby relieving the torque on the locking hardware.

SAFETY IMPLICATIONS The deficiency could possibly result in damage to the engineered safeguards for pumps affected and in their failure to operate.

CORRECTIVE ACTION Ingersoll Rand developed modification kits for the pump impeller locking de-vices which provide a more positive locking design. The cap nut was deleted from the design. Only one nut is now involved. A tab washer was added and the large impeller washer was modified by the addition of a pin. The changes are such that one mating part cannot rotate with relation to the next part.

This is prevented by mechanical interference as opposed to friction as in the original design.

The original design had a flat fibrous gasket to prevent leakage between the shaft and shaft sleeve in the mechanical seal area above the impeller. This gasket was deleted. An "O" ring was incorporated and an appropriate groove was machined into the shaft sleeve. Whereas torque of the previous jam and cap nuts compressed the old gasket, now the stack up of parts is all metal to metal with relation to torquing of the impeller nut.

Field Change Request Number M-72, Revision 1 documents approval of revisions to the Ingersoll Rand Technical Manual and Drawing No P-78-1, Revision 1.

Ingersoll Rand installed the new impeller locking device modification kit on LPSI Pump "A" at their Phillipsburg, New Jersey facility. Certification dated 12-19-79 of this repair is on file at the Waterford site under Purchase Order NY-403402, Suborder CE 9101524.

Installation of the modification kit on Pump "B" was performed on site by Culf Engineering and completed 5-20-80 in accordance with the disposition of Nonconformance Report W3-983.

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