ML18153D377
| ML18153D377 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/29/1993 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 93-206, NUDOCS 9307080128 | |
| Download: ML18153D377 (12) | |
Text
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 June 29, 1993 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 INSERVICE TESTING PROGRAM RELIEF REQUEST CLARIFICATION Serial No.
NO/ETS Docket Nos.
License Nos.93-206 RO 50-280 50-281 DPR-32 DPR-37 The NRC Safety Evaluation Report (SER) for Surry Power Station's ASME Section XI lnservice Testing (1ST) Program Plan was received by letter dated March 22, 1993.
Although the NRC SER did not identify any issues that require a specific response, there was one issue concerning the development of head curves for the emergency service water pumps that needs to be further addressed. Separately in an earlier NRC SER dated August 27, 1990, the NRC approved the use of minimum vibration reference values for pump vibration analysis. However, the use of these minimum vibration reference values for pump vibration analysis was only granted until either the industry revised the appropriate standard or for three years, whichever occurred sooner. The three years will expire in August of 1993. Both of these issues are discussed below.
Relief Request P-11 (attached) for the emergency service water pumps describes the difficulty of performing the quarterly ASME test for these pumps. The hydraulic test loop is a fixed resistance system which is affected by tide level. To eliminate waiting for the proper tidal conditions, use of a pump curve based on the changing tidal conditions has been developed. The NRC evaluation concluded that the use of a pump curve is acceptable, provided that certain elements are incorporated into the 1ST Program. One of these elements required by the SER was that the curves be based on an adequate number of points, with a minimum of five. If defining the whole pump curve were required, we would agree that at least five points would be necessary to adequately establish the pump curve. However, the portion of the pump curve affected by the change in tide level is small. A maximum change of +/-3 feet in tide level produces approximately a 1000 gpm change in flow. The reference value is approximately 17,000 gpm. This portion of the pump curve can be adequately represented by three points instead of five.
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e Requiring that the pump curve be regenerated with a minimum of five points after every major maintenance activity would be an unnecessary burden because the curve cannot be generated during one test as with most pumps.
High and low tides occur approximately eleven hours apart.
- Not only must the high and low tide points be determined, but points in between must also be generated over a long period of time.
Given the small portion of the pump curve affected and the difficulty in gathering the data, three data points would be more then adequate to develop the pump curve.
Based on this additional information, Surry Power Station requests concurrence from the NRC to use three points to develop the appropriate portion of the pump curve for the emergency service water pumps. Relief Request P-11 applies only to Surry Unit 1.
Relief Request P-1 (attached) contains a note that establishes a minimum of 0.05 in/sec for vibration velocity reference values. In the SER dated August 27, 1990, the NRC evaluation states that, "This issue is being considered by the ASME O&M Working Group on Pumps. It is expected that, within two or three years, a permanent change will be made to OM-6 to address this issue. Therefore, the proposed alternative may be used for a period of three years. Before the end of this period, this relief request must either be modified to reflect the code changes on this issue or be withdrawn." The issue of using a minimum velocity reference value is still active with the O&M working group.
However, a permanent change to OM-6 is not expected in the near future. Therefore, Surry Power Station requests an extension on the use of a minimum reference value for a period of three years beyond August 1993 or until OM-6 is changed, whichever occurs sooner. Relief Request P-1 applies to Surry Units 1 and 2.
Should you have any additional questions or require additional information, please contact us.
Very truly yours, Jtf@A--
- w. L. Stewart Senior Vice President - Nuclear Attachments cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Surry Power Station Unit 1 1ST Relief Request e
RELIEF REQUEST P-1 Systems: Various Pump(s): IWP Program Pumps. See PUMP INSERVICE TEST TABLE.
Class :
Section XI Code Requirements For Which Relief Is Reguested 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.
RELIEF REQUEST P-1 (Cont.)
- 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.
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 (Part 6), An American National Standard In-Service Testing of Pumps.
RELIEF REQUEST P-1 (cont.)
RANGES OF TEST PARAMETERS (1)
PUMP PUMP TEST ACCEPTABLE ALERT lYPE SPEED PARAMETER RANGE R,lll\\!?E Centrifugal
<600 rpm vd
.s.2.5 Vr
>2.5V r to 6V r And Vertical but not > 10.5 mils Line Shaft
~600 rpm Vv
.s_2.5 V r(2)
>2.5 Vrto 6Vr but not >0.325 in/sec Reciprocating VdorVv
.s.2.5 Vr 2.5 VrtO 6Vr Note:
(1) Vr is the vibration reference value in the selected units Vd is vibration displacement measured peak-to-peak, unfiltered Vv is vibration velocity measured peak, unfiltered REQUIRED ACTION RANGE
>6 Vr but not >22 mils
>6 Vr but not >0.70 in/sec
>6 Vr (2)
Small values for Vr will produce small acceptable ranges for pump operation. Based on a small acceptable range, an adequately and smoothly running pump could be subject to corrective action. To avoid this situation, a minimum value for Vr of 0.05 in/sec has been established for velocity 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. Use of a minimum value for Vr is allowed for a three year period which ends in August, 1996. This interim period is discussed in the Surry Safety Evaluation Report received in August of 1990 (Serial No.90-546).
3-1 5 Rev.5 March 19, 1992
System : Service Water Pump(s):
Class : 3 1-SW-P-1A 1-SW-P-18 1-SW-P-1C Section XI Code Requirements For Which Relief Is Requested RELIEF REQUEST P-11 Measure inlet pressure and differential pressure.
ASME Section XI, Subarticle IWP-311 O requires reference values to be one or more fixed set of measured values. All subsequent test results shall be compared to these reference values.
Basis For Reguest No installed inlet pressure instrumentation exists. Inlet pressure will be calculated from the tide level and subtracted from the discharge pressure to yield differential pressure.
The emergency service water pumps take suction from the James river and discharge into the intake cannel. The James river near the plant is subject to a tide level variation of approximately five feet. Therefore, the total static head for the system can vary from test to test. There are no valves in the lines to throttle flow and to compensate for the change in system static head. The only way to duplicate flow and differential pressure from test to test is to perform the test at the same tide level each time. Trying to perform this test within a small enough tide level range to produce repeatable results has proven impractical. To compensate for the change in total system head, a pump reference curve will be prepared based on test results taken at different tide levels.
Tests will be conducted within the tide level limits of the curve, and results will be compared to acceptance criteria based on the reference curve and the ranges given in Table IWP-3100-2.
Alternate Testing Proposed Inlet pressure will be calculated from the tide level and subtracted from the discharge pressure to yield differential pressure. Tests will be conducted within the tide level limits of the pump reference curve, and results will be compared to acceptance criteria based on the reference curve and the ranges given in Table IWP-3100-2.
Surry Power Station Unit 2 1ST Relief Request
e RELIEF REQUEST P-1 Systems: Various Pump(s): IWP Program Pumps. See PUMP INSERVICE TEST TABLE.
Class :
Section XI Code Requirements For Which Relief Is Reguested Measure pump bearing temperatures and vibration in mils.
Basis For Reguest 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 i$ 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.
L
~~--
RELIEF REQUEST P-1 (cont.)
RANGES OF TEST PARAMETERS (1)
PUMP PUMP TEST ACCEPTABLE ALERT 1YF£ Sf:133)
P.ARAMETER R/INGE FW\\GE Centrifugal
<600 rpm vd
.s,2.5 Vr
>2.5V r to 6V r And Vertical but not >10.5 mils Line Shaft
~600 rpm Vv s.2.5 Vr(2)
>2.5 Vrto 6Vr but not >0.325 in/sec Reciprocating Vd orVv s.2.5 Vr 2.5 VrtO 6Vr Note:
(1) Vr is the vibration reference value in the selected units Vd is vibration displacement measured peak-to-peak, unfiltered Vv is vibration velocity measured peak, unfiltered
\\,
REQUIRED ACTION RANGE
>6 Vr but not >22 mils
>6 Vr but not >0.70 in/sec
>6 Vr (2)
Small values for Vr will produce small acceptable ranges for pump operation. Based on a small acceptable range, an adequately and smoothly running pump could be subject to corrective action. To avoid this situation, a minimum value for Vr of 0.05 in/sec has been established for velocity 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. Use of a minimum value for V r is allowed for a three year period which ends in August, 1996. This interim period is discussed in the Surry Safety Evaluation Report received in August of 1990 (Serial No.90-546).
3-1 5 Rev.3 March 19, 1992
RELIEF REQUEST P-1 (Cont.)
- 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.
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 (Part 6), An American National Standard In-Service Testing of Pumps.
RELIEF REQUEST P-1 (cont.)
RANGES OF TEST PARAMETERS (1)
PUMP PUMP lYR:
SPffJ)
Centrifugal
<600 rpm And Vertical Line Shaft
~600 rpm Reciprocating TEST PARAMETER ACCEPTABLE RPNGE s.2.5 Vr
.s,2.5 Vr(2) s.2.5 Vr Note:
(1) Vr is the vibration reference value in the selected units Vd is vibration displacement measured peak-to-peak, unfiltered Vv is vibration velocity measured peak, unfiltered ALERT FW"l?E
>2.5Vr to 6Vr but not >10.5 mils
>2.5 Vrto 6Vr but not >0.325 in/sec REQUIRED ACTION RANGE
>6Vr but not >22 mils
>6 Vr but not >0.70 in/sec (2)
Small values for Vr will produce small acceptable ranges for pump operation. Based on a small acceptable range, an adequately and smoothly running pump could be subject to corrective action. To avoid this situation, a minimum value for Vr of 0.05 in/sec has been established for velocity 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. Use of a minimum value for V r is allowed for a three year period which ends in August, 1993. This interim period is discussed in the Surry Safety Evaluation Report received in August of 1990 (Serial No.90-546).
3-1 5 Rev.3 March 19, 1992
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