ML18153B612

Forwards Revised Relief Request P-1 from ASME Section XI Inservice Pump Testing Vibration Velocity Ref Values.Min Value of 0.05 Inches Per Second for Vibration Velocity Ref Values Proposed

ML18153B612
Person / Time
Site:	Surry
Issue date:	02/22/1989
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-084, 89-84, NUDOCS 8903010071
Download: ML18153B612 (5)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 W. R. CARTWRIGHT VxcE PRESIDENT February 22, 1989 NUCLEAR U. S. Nuclear Regulatory Commission Serial No.89-084 Attn: Document Control Desk PES/ISI/DJF: vl h Washington, D. C. 20555 Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 ASME SECTION XI INSERVICE PUMP TESTING VIBRATION VELOCITY REFERENCE VALUES On September 30, 1988, Virginia Electric and Power Company submitted new revisions to the Inservice Testing Program for Pumps and Valves for Surry Units 1 and 2. In these submittals are relief requests (Relief Request P-1 for both units) that describe the use of pump vibration velocity measurements instead of vibration displacement measurements as required by the Code. Surry Power Station proposes to revise Relief Request P-1 with a minimum value for vibration velocity reference values. The revised Relief Request P-1 is attached. The technical basis for the revision is given below.

During the process of determining the vibration velocity reference values, a problem arose. Approximately half of the reference values (45 out of 96) are 0.04 in/sec or below as shown in the attachment. Sixteen reference values are 0.01 in/sec. Applying the 2.5 multiplier given in Relief Request P-1 yields a very small operating range for these pumps (as low as 0.025 in/sec) according to the acceptance criteria. Note that the acceptance criteria were taken from ANSI/ASME OM-6-July 1987, Draft 11, 11 An American Standard for In-Service Testing of Pumps. 11 We propose establishing a minimum value of 0.05 in/sec for the vibration velocity reference values. This value yields an acceptable operating range up to and including 0.125 in/sec. As shown by Surry Station operating experience and existing literature, centrifugal pumps operating at or below 0.125 in/sec, are considered to be in good running condition. The attachment is a technical paper from PMC/BETA Corporation which includes a severity chart. The chart indicates centrifugal pumps operating below 0.2 in/sec are considered to be in good running condition.

If you have any questions regarding this revision to our Relief Request, please contact us.

Attachments cc: U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. W. E. Holland NRC Senior Resident Inspector Surry Power Station

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RELIEF REQUEST P-1 Systems: Various Pump(s): IWP Program Pumps. See PUMP INSERVICE TEST TABLE.

ClassSection XI Code Requirements For Which Relief Is Requested Measure pump bearing temperatures and vibration in mils.

Basis For Request Pump vibration and bearing temperature measurements are used to detect changes in the mechanical characteristics of a pump. Regular testing should detect developing problems, thus repairs can be initiated prior to a pump becoming inoperable. The ASME Section XI minimum standards require measurements of the vibration amplitude displacement in mils every three. months and bearing temperatures once per year.

Our proposed program is based on vibration readings in velocity units rather than vibration amplitude in mils displacement. This technique is an industry accepted method which is more sensitive to small changes that are indicative of developing mechanical problems and hence more meaningful. Velocity measurements detect not only high amplitude vibrations that indicate a major mechanical problem, but also the equally harmful low amplitude high frequency vibrations due to misalignment in balance, or bearing wear that usually go undetected by simple displacement measurements.

In addition, these readings go far beyond the capabilities of a bearing temperature monitoring program. A bearing will be seriously degraded prior to the detection of increased heat at the bearing housing. Quarterly vibration velocity readings should achieve a much higher probability of detecting developing problems than the once per year reading of bearing temperatures.

Bearing temperature tests present problems which include the following:

1. Certain systems have no recirculation test loops and a limited source of water. An enforced thirty minute run time would deplete the source.

2. The lubrication fluid for some pumps is taken from the process water, which can change temperature depending on ambient conditions. Data trending for these cases is not meaningful.

Therefore, the detection of possible bearing failure by a yearly temperature measurement is extremely unlikely. The small probability of detection of a bearing failure by temperature measurement does not justify the additional pump operating time required to obtain the measurements. In addition, it is impractical to measure bearing temperatures on many pumps.

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e RELIEF REQUEST P-1 (CONT'D)

Alternate Testing Proposed Pump vibration measurements will be taken in vibration velocity (in/sec). The evaluation of the readings will be per the attached table. The ranges of Test parameters given in the attached table were taken from ANSI/ASME OM-6-July 1987, Draft 11," An American National Standard In-Service Testing of Pumps.

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RELIEF REQUEST P-1 (cont'd)

RANGES OF TEST PARAMETERS (1)

PUMP PUMP TEST ACCEPTABLE ALERT REQUIRED TYPE SPEED PARAMETER RANGE RANGE ACTION RANGE e

Centrifugal <600 rpm vd s2.5 V )2.5V to 6V )6 V r r r r And Vertical Line Shaft but not )10.5 mils but not > 22 mils

~600 rpm VV S2.5 V (2) )2.5 V to 6V r r

)6 V r

r but not )0.325 in/sec but not )0.70 in/sec Reciprocating s2.5 V >2.5 V to 6V >6 Vr r r r orV V

Note: (1) V is the vibration reference value in the selected units Vr is vibration displacement measured peak-to-peak, unfiltered Vd is vibration velocity measured peak, unfiltered V

(2) Small values for' V will produce small acceptable ranges for pump operation. Based on a small acceptable range, an idequately and smoothly running pump could be subject to corrective action.

To avoid this situation, a minimum value for V of 0.05 in/sec has been established for velocity r

measurements. Pumps with a measured reference value below 0.05 in/sec shall have subsequent test results compared to an acceptable range based on 0.05 in/sec.

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