ML031410018
| ML031410018 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 05/09/2003 |
| From: | Warner M Florida Power & Light Energy Seabrook |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NYN-03039 | |
| Download: ML031410018 (16) | |
Text
FPL Energy FPL Energy Seabrook Station Seabrook Station P.O. Box 300 Seabrook, NH 03874 (603) 773-7000 May 9, 2003 NYN-03039 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Seabrook Station Inservice Test Program Relief Request PR-3 FPL Energy Seabrook, LLC hereby requests Nuclear Regulatory Commission review and approval of the enclosed Inservice Test (IST) Program Relief Request, PR-3. Seabrook Station performs IST in accordance with the 1995 Edition (including the 1996 Addenda) of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code). The enclosed relief request proposes to increase the alert range absolute limit identified in ISTB Table 5.2.1-1 from 0.325 inches per second (ips) to 0.350 ips for the outboard bearing of the Containment Building Spray (CBS) pumps in the horizontal and vertical directions.
The CBS pump design uses a wide, four-vane impeller that is susceptible to elevated vane pass vibration. This induced vibration amplitude, along with pump casing resonance near the vane pass frequency results in elevated overall vibration levels. Due to the elevated vibration levels, the vibration reference value (outboard pump bearing vertical) for CBS-P-9A is very close to the ISTB Table 5.2.1-1 absolute limit of 0.325 ips. The vibration reference value (outboard pump bearing horizontal) for CBS-P-9B exceeds the ISTB Table 5.2.1-1 absolute limit of 0.325 ips.
Strict compliance with the requirements of the ASME OM Code causes the frequency of testing of the subject pumps to be unnecessarily increased.
The NRC approved a similar relief request for the Sequoyah Nuclear Plant, Units 1 and 2 by letter dated July 16, 2002 (TAC Nos. MB4930 and MB4931). FPLE Seabrook requests the NRC to review and approve the subject relief request by November 1, 2003.
VALf
U. S. Nuclear Regulatory Commission NYN-03039/Page 2 Should you have any questions concerning this issue, please contact Mr. James M. Peschel, Regulatory Programs Manager, at (603) 773-7194.
Very truly yours, FPL Energy Seabrook, LLC Mark E. Warner Site Vice President cc: H. J. Miller, NRC Region I Administrator V. Nerses, NRC Project Manager, Project Directorate I-2 G.T. Dentel, NRC Senior Resident Inspector
Enclosure to NYN-03039 Relief request: PR-3 Pumps: CBS-P9A, CBS-P9B Code Class: 2 Function: Pumps required to perform a function in shutting down the reactor or in mitigating the consequences of an accident, and are provided with an emergency power source.
Test Requirements: ISTB Table 5.2.1-1 requires an Alert Range of >2.5Vr to 6 Vr, or > 0.325 to 0.7 in./sec for centrifugal pumps that operate at 2 600 RPM.
Basis For Relief: 1. Pump casing resonance amplification causes the CBS-P-9B pump outboard bearing vibration to exceed the ISTB Table 5.2.1-1 Alert Range absolute limit.
- 2. Pump casing resonance amplification causes the CBS-P-9A pump outboard bearing vibration to approach the ISTB Table 5.2.1-1 Alert Range absolute limit leaving very little room for test repeatability.
The cause of the vibration is well understood, and is a result of our original pump design and the sizing of our recirculation line. It is not the result of any material degradation from the original installation. A design change to update the impeller design would be required to obtain some test margin, however this design change would not fix any material degradation, or restore lost margin.
The pump casing resonance amplification issue impacts both pumps, although only the CBS-P-9B pump has gone into the ALERT condition.
The corresponding vibration levels on Containment Spray Pump CBS-P-9A have not reached the Alert Range, but are very close to the limit (the most recent reference value, Vr is 0.319 in/sec at the outboard pump bearing, vertical).
Pump casing resonance amplification results in a testing hardship due to the lack of any margin between our reference value and the ISTB Table 5.2.1-1 Alert Range absolute limit. Additional testing does not provide any compensating increase in the level of quality and safety. The pumps are infrequently run, on the order of 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> per year. Seeking a design change solely for the purposes of establishing some test repeatability margin subjects Seabrook Station to an undue burden to comply with the regulation.
Increasing the ISTB Table 5.2.1-1 ALERT Range Absolute limit from 0.325 ips to 0.350 ips for the PUMP OUTBOARD HORIZONTAL AND VERTICAL BEARING limit on both -CBS-P-9A and -CBS-P-9B, will provide adequate margin for test repeatability.
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During the last two years Seabrook Station has been monitoring the CBS Pump vibration as part of the Predictive Maintenance Monitored Equipment Program.
Containment Spray Pump (CBS) CBS-P-9B outboard pump bearing overall vibration amplitude exceeds the ASME OM Code IST ALERT limit of
>0.325 in/sec. The initial outboard pump bearing, horizontal reference value, Vr, is 0.347 in/sec. Since July 2001, the readings at this point have been between 0.311 and 0.347 in/sec.
Additional vibration data collection and analysis identified high pump vane pass spectral responses. Pump casing resonance testing identified that the pump has a resonance frequency similar to that of pump vane pass. This condition results in vibration amplitude amplification that is responsible for most of the vibration magnitude. A review of past pump history, including plant pre-operational test data identified similar pump vane pass vibration amplification.
CBS pump design uses a wide, four-vane impeller that is susceptible to elevated vane pass vibration. This induced vibration amplitude, along with casing resonance near vane pass frequency, results in elevated overall vibration levels. There are no corrective actions to minimize this condition without replacing the pump impeller.
Recent pump bearing resonance test results confirm tests performed during initial plant startup (1986). These results identify that the casing resonance contributes to the overall vibration amplitude. Continued pump operation at these levels is acceptable. Additionally, high resolution vibration data analysis has not found any indications of bearing wear or degradation.
During Refueling Outage 08 (OR08), Seabrook Station performed a disassembly and inspection of CBS-P-9B. This inspection indicated that the pump did not have to be refurbished to restore any lost margin. Inspections of the wearing ring clearances were found to be satisfactory. The clearance acceptance criteria is 0.017 inches to 0.025 inches. The inboard clearances were 0.021 to 0.023 inches and outboard clearances were 0.022 to 0.023 inches. This disassembly validated our performance monitoring programs.
Based on this test history, the OR08 CBS-P-9B disassembly, and the current vibration values, an ISTB 5.2.1-1 ALERT RANGE increase of the lower vibration limit from 0.325 inches per second to 0.350 inches per second for the pump outboard bearing vibration readings is warranted. The bases for the 0.350 inches per second is to simply provide some margin for test repeatability and to define a limit for additional actions.
Supplemental information is provided in the attached evaluation of CBS pump historical performance.
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Alternate Testing: These CBS Pumps will be subject to additional testing, trending, and diagnostic analysis as required by the Seabrook Station Predictive Maintenance Program. This program employs predictive monitoring techniques that go beyond the vibration monitoring and analysis required by ISTB. These techniques also now include oil sampling and analysis. If the measured parameters were found to be outside the normal operating range or were determined to be trending toward an unacceptable degraded state, then appropriate actions would be taken.
These actions include monitoring additional parameters, review of specific information to identify cause, and potential removal of the pump from service to perform necessary maintenance.
- Increase the ISTB Table 5.2.1-1 ALERT Range Absolute limit from 0.325 ips to 0.350 ips for the PUMP OUTBOARD HORIZONTAL AND VERTICAL BEARING limit on both -CBS-P-9A and 1-CBS-P-9B.
- Using the provisions of this relief request as an alternative to the specific requirements of ISTB Table 5.2.1-1, which have been identified as being impractical, will provide adequate indication of pump performance.
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CBS Pump Relief Request Evaluation Discussion Containment Building Spray (CBS) pumps supply the containment spray headers during a design based accident when containment building pressure exceeds the Containment Pressure-HI-3 setpoint. During normal operation, the pumps are tested using an alternate mini-flow path which is capable of 1915 to 1955 gallons per minute (gpm) flow. This is adequate to allow pump performance flow and differential pressure testing, however; this flow rate increases pump internal recirculation flow that increases pump impeller vane pass vibration response. Pump vibration is measured at the bearing housings. Since plant startup all monitored locations have consistently been elevated. On July 3, 1985, during the performance of pre-operational test, PT-12.1, pump vibration amplitude values were above acceptable levels. Additional data collection and analysis was performed and identified the major spectral vibration component of 14,300 cpm. As a result of this information no additional work was performed to reduce vibration levels and the elevated vibration condition was accepted.
Pump outboard vibration amplitude levels fluctuate above and below the ASME OM-Code, ISTB, Table 5.2.1-1, Alert limit of 0.325 inches/second Peak. This limit is the absolute limit for pumps speeds greater or equal to 600 revolutions per minute (RPMs).
This results in unnecessarily placing the CBS-P-9B pump in an Alert status. This action is inconsistent with the IST program intent. The intent is the additional monitoring is required to determine a degrading condition. In this case, the equipment will continue to function normally at these vibration levels during surveillance testing. It is expected that during a design basis condition where pump flow rates are approximately 3030 gpm that pump bearing vibration amplitudes would be less 0.325 ips Peak.
The CBS pumps are a Bingham-Willamette Company Type CD. The pump style is a double suction single discharge, single stage pump having a flooded suction. Normal suction pressure is approximately 55 psig during surveillance testing.
The pump impeller is configured with a wide flat discharge vane exiting to the discharge diffuser. This pump impeller design is prone to vane pass induced vibration. The pump vendor was contacted and regarding this design issue. The vendor stated that the present impeller design is no longer manufactured and their current replacement impeller has a modified vane exit passages to reduce vane pass excitation.
Analysis NUREG/CP-0152, (1996) Article on Nuclear Power Plant Safety Related Pump Issues, pages 4-32 and 4-33 discusses four elements that should be considered for NRC staff review when changing Code Absolute Vibration Limits. These are:
1 Pump vibration history 2 Information from the pump manufacturer, 3 Discussion of owner attempts to lower vibration, and 4 Spectral analysis of the pump-driver system.
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The following addresses each of these four elements:
- 1. Pump vibration has been programmatically recorded since 1991. Attachment 1, Table One, provides nearly 11 years of CBS Pump vibration history. This data is for the Pump Outboard Horizontal Bearing on both the CBS-P-9A and CBS-P-9B.
- 2. Information from the pump manufacturer. The original pump vendor, Bingham-Willamette Company is now part of Sulzer Pumps (US) Inc. Mr. Simon H. Daou, a Rotating Equipment Engineer and Mr. John F. Murry, National Sales Manager - Power both from Sulzer visited Seabrook Station to discuss the elevated pump vibration levels. Mr. Daou stated that Sulzer no longer supplies the single exit vane impeller style and now supplies a split exit vane impeller to reduce the induced vane pass energy. Changing the impeller with a new design would require an in-service pump performance test and is not recommended (e.g.,
design change not done to address test margin, or for degradation purposes).
Additional pump modal response vibration data was forwarded to Sulzer for their evaluation. The results of this effort is a new vendor recommended pump bearing limit of 0.35 ips Peak. See Attachment 2 Sulzer Pump vendor correspondence.
- 3. Discussion of owner attempts to lower vibration.
During refueling outage eight CBS-P-9B was disassembled to repair several bearing oil leaks and perform an internal pump inspection. The inspection did not identify any unusual conditions and the pump was returned to service.
Pump bearing housing modal testing (bump testing) was performed to determine the structure's resonance frequencies. The results identified that the pump outboard housing has broad frequency response amplification at the vane pass frequency and at two times vane pass. This means that any vibration stimulus at the vane pass frequencies is amplified. See additional information in Attachment 1 Advanced Diagnostic Report.
There are no acceptable methods to reduce pump vibration without authorizing a design change done solely to address the Code administrative limit.
- 4. Spectral Analysis of the pump-driver system.
During routine pump testing both vibration amplitude and spectral data are collected. Pump and motor spectral data are reviewed and trended over a frequency range of 5 to 1000 Hz. This data indicates that there are no pump rolling element bearing or motor bearing degrading trends. See the spectral graphic below; CBS-P-9B Pump Outboard Bearing Horizontal Vibration Spectra.
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CBS-P-9B Pump Outboard Bearing Horizontal Vibration Spectra Pump bearing housing modal testing identified broad resonance amplification peaks at the pump lx and 2x vane pass frequencies. Vibration spectral analysis shows that the pump outboard bearing horizontal location has a lx amplitude peak of 0.05 ips, while the vane pass amplitude peak is 0.065 ips and the two time vane pass amplitude is 0.084 ips.
This data supports that the elevated vibration amplitudes at the pump outboard bearing are the result of vane pass excitation energy due to resonance amplified. Data analysis has not identified any bearing distress frequencies or indications of improper rotor balance or shaft rubs.
Pump bearing housing resonance amplification problem is also present on CBS-P-9-A, but to a lesser degree. See the spectral graphic below; CBS-P-9A Pump Outboard Bearing Horizontal Vibration Spectra. Pump outboard vibration amplitudes are averaging 0.31 ips.
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CBS-P-9A Pump Outboard Bearing Horizontal Vibration Spectra During accident conditions, CBS pumps would operate in response to a containment high pressure signal. Pump operation would not be limited by the recirculation line size as full pump flow operation would exist. In this condition, pump vibration amplitudes would be reduced since internal pump recirculation would be reduced and pump forcing frequencies would also be subsequently reduced. Although full flow vibration data has not been collected it is reasonable to expect overall vibration amplitudes would be reduced as observed on other single stage pumps. Consequently, based on these modes of operation for both normal and accident conditions, the CBS pump would only experience elevated vibration from vane pass during IST Comprehensive and other routine surveillance testing.
The pump manufacturer has been involved evaluating the pump vibration data and agrees with increasing pump bearing vibration limits due to vane pass frequency phenomena.
The pump manufacturer agrees that quarterly ISTB Table 5.2.1-1 pump tests on mini-flow recirculation does not reduce pump bearing life. These tests are short duration (15-30 minutes) and bearing life is considerable based on the actual pump run time.
Pump run time for both CBS pumps is approximately 400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />.
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ISTB Section 6.2.1 states "If the measured test parameter values fall within the Alert range of Table ISTB 5.2.1-1, Table 5.2.1-2, or Table 5.2.3-1, as applicable, the frequency of testing specified in paragraph 5.1 shall be doubled until the cause of the deviation is determined and the condition is corrected". In this case, the pump outboard bearing horizontal vibration does often exceed the Alert range causing the test frequency to be increased. The cause of the pump bearing vibration amplitude deviation has been attributed to vane pass frequency amplification. The elevated vibration amplitude is not indicative of pump degradation and is not predicted to result in degraded pump performance or failure. The correction for this condition would result in replacing the pump impeller requiring head verification and/or replacing pump discharge recirculation piping. Implementing either of these two options would require substantial costs and equipment unavailability. In this circumstance, doubling the frequency unnecessarily operates a component to perform a test that does not provide any additional information and provides no additional assurance on information as to the condition of the pump or its ability to perform its safety function.
Conclusion The cause of the vibration is well understood, and is a result of our original pump design and the sizing of our recirculation line.
The issue impacts both pumps, although only the CBS-P-9B pump has gone into the ALERT condition. The corresponding vibration levels on Containment Spray Pump CBSP-9A have not reached the Alert Range, but are very close to the limit (the most recent reference value, Vr is 0.319 in/sec at the outboard pump bearing, vertical).
Casing resonance amplification results in a testing hardship due to the lack of any margin between our reference value and the ISTB Table 5.2.1-1 Alert Range absolute limit.
Additional testing does not provide any compensating increase in the level of quality and safety.
Increasing the ISTB Table 5.2.1-1 ALERT Range Absolute limit from 0.325 ips to 0.350 ips for the PUMP OUTBOARD BEARING HORIZONTAL AND VERTICAL limit on both 1-CBS-P-9A and 1-CBS-P-9B, will provide adequate margin for test repeatability.
Using the provisions of this relief request as an alternative to the specific requirements of ISTB Table 5.2.1-1, which have been identified as being impractical, will provide adequate indication of pump performance.
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Form A: Advanced Diagnostics Report Unit II System CBS ID I CBS-P-9B Status I Operable CBM File# I 01-001 l Machine Name 1-CBS-P-9B Tracking Mechanism CR 01-07360-01 Overall Condition: Operable Containment Building Spray Pump Outboard Bearing CBS-P-9B outboard pump bearing overall vibration amplitude exceeds IST limit of 0.325 ips during the comprehensive IST pump test. Actual pump outboard bearing vibration is 0.346 ips, while pump outboard vertical is 0.28 ips. Additional vibration data collection and analysis identified high pump vane pass spectral responses. Pump casing resonance testing identified that the pump has a resonance frequency similar to that of pump vane pass frequency of 14,250 cpm. This condition results in vibration amplitude amplification. A review of past pump history identified similar pump vane pass vibration amplification. No corrective actions were implemented during this time. Vibration levels have been routinely above 0.325 ips. See Figure One.
E] Continuation Sheet Suspected Cause(s): Casing Resonance with Pump Vane Pass Amplification CBS pump design uses a wide, four-vane impeller that is susceptible to elevated vane pass vibration. This induced vibration amplitude, along vith casing resonance near vane pass frequency, results in elevated overall vibration levels. There are no corrective actions to minimize this condition without replacing the pump impeller.
[L Continuation Sheet Diagnostic Recommendation(s): None Recent pump bearing resonance test results confirm tests performed during initial plant startup (1986).
See Table One, PUMP OUTBOARD HORIZONTAL HISTORICAL DATA. These results identify that the casing resonance contributes to the overall vibration amplitude. Continued pump operation at these levels is acceptable. Additional, high resolution vibration data analysis has not found any indications of bearing wear or degradation.
El Continuation Sheet Maintenance Recommendation(s): None There are no maintenance actions that can improve this condition. Impeller replacement with an improved design, e.g. split vane, would reduce pump vibration. However, this would involve a design change. This would require addition post modifications testing that would be very difficult to accomplish.
El Continuation Sheet Monitoring Summary:
PdM Technologies Vibration Lube Oil Thermography Other Last Date Monitored: 6/24/02 12/9/02 6/24/02 Current Condition: Alert Monitor Normal Monitoring Frequency: 98 weeks 24 weeks 96 weeks Post Mntc Test Req'd: N/A N/A N/A Analyzed By: Robert A. Gwinn Signature Date: / 6 Reviewed By: Joe Mayer Signature: Date:
Approved By: CBM Supervisor Signature: Date:
M' .
Figure One CBS-P-9B Pump Outboard Horizontal Resonance Test Data Review
.tiS' i ll -,.],, :;:1w !1 fi l (None) Coherence Magnitude 0 ...... ......................................................................................................... . .
W.......................................... ........................................................................
0: .................... i ii 5000 10000 15000 20000 Frequency (CPM)
(g/ Pound-Force) / 10 Accelerance Magnitude 0.15 . ~~~~~~~~~~~~~~~~~~~~~~~~~... M.
0 m.
0.05 ...
5000 10000 15000 20000 Waiting for trigger Frequency (CPM)
Frequency 14.820 KCPM Number Averages 5 Amplitude 13.386mg/Pound-Force
- - .W_~C os . oo In=1 ZomPu A comparison between the spectral and analog overall vibration amplitudes has been made. This comparison indicates a minor difference between the vibration energy in the spectral range of 300 to 60,000 cpm (5 to 1000 Hz) and the overall range of 300 to 4,500,000 cpm (5 to 75,000 Hz). As expected, the larger spectral band provides a higher number. This broad band energy as compared to the spectrum overall is insignificant and is made to show that most of the energy is below 60,000 cpm (1,000 Hz) due to pump vane pass vibration resonance amplification. There are not indications of rolling element bearing distress frequencies, e.g. ball pass, ball pass inner/outer race, or fundamental train frequencies.
Location Position 300 to 60,000 300 to 4,500,000 Change (%)
cpm cpm 1 (POH) 0.317 ips 0.346 ips 0.029 (8.38%)
2 (POV) 0.255 ips 0.275 ips 0.020 (7.27%)
3 (POA) 0.165 ips 0.191 ips 0.026 (13.61%)
4 (PIH) 0.237 ips 0.265 ips 0.028 (10.56%)
5 (PIV) 0.231 ips 0.256 ips 0.025 (9.7%)
CBS-P-9-B will continue to perform without any degraded performance based on the pump vane pass resonance amplification. There is no justification at this time that would require pump impeller replacement or pump outboard bearing housing stiffening.
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Table One Pump Outboard Horizontal Historical Data 1-CBS-P-9-B 1-CBS-P-9-A Date POH Date POH 07/07/91 0.30 5/27/91 0.32 09/15/91 0.30 9/30/91 0.3 12/20/91 0.33 11/11/91 0.3 01/28/92 0.31 2/04/92 0.28 03/17/92 0.34 4/27/92 0.3 06/08/92 0.32 7/31/92 0.3 08/31/92 0.30 9/01/92 0.28 11/05/92 0.31 10/31/92 0.29 11/23/92 0.32 1/04/93 0.24 02/15/93 0.30 3/29/93 0.3 05/13/93 0.31 6/21/93 0.28 08/02/93 0.30 9/13/93 0.31 10/15/93 0.35 12/06/93 0.28 01/18/94 0.30 2/28/94 0.29 08/01/94 0.30 7/23/94 0.28 09/26/94 0.31 8/15/94 0.28 12/19/94 0.29 11/07/94 0.3 01/13/95 0.30 1/30/95 0.3 06/05/95 0.30 4/24/95 0.28 08/28/95 0.34 6/04/95 0.28 12/06/95 0.35 7/17/95 0.27 02/13/96 0.36 10/10/95 0.3 05/07/96 0.29 1/02/96 0.29 07/29/96 0.30 3/25/96 0.3 10/21/96 0.34 6/17/96 0.28 01/13/97 0.29 9/09/96 .028 04/07/97 0.30 12/02/96 0.28 06/30/97 0.35 2/24/97 .022 09/22/97 0.31 5/01/97 0.27 12/23/97 0.38 11/04/97 0.24 03/13/98 0.318 1/07/98 0.286 03/13/98 0.314 4/20/98 0.324 07/29/98 0.335 6/22/98 0.253 10/20/98 0.273 9/10/98 0.253 03/19/99 0.304 2/25/99 0.257 06/30/99 0.318 5/20/99 0.294 12/01/00 0.331 8/12/99 0.277 07/25/01 0.337 11/04/99 0.279 07/25/01 0.347 9/07/0 1 0.304 05/31/00 0.352 5/18/02 0.312 05/31/00 0.34 8/09/02 0.277 12/01/00 0.331 7/25/01 0.346 1/09/02 0.352 5/18/02 0.334 6/24/02 0.311 12
Attachment 2 Sulzer Pumps Good day Mr. Gwinn, Further to you email below, and following a review please note "The vibration alert limit is not to exceed .35 ips".
Please advise should you require additional information.
Best regards, Simon Daou, P.E.
Rotating Equipment Engineer, Eastern Service Center Sulzer Pumps (US) Inc.
106 lberville Street Dollard-des-Ormeaux, Quebec H9B 3A9 Tel. +1 514-685-8520 Mobile phone +1 514-234-3838 Fax +1 514-684-3545 E-mail mailto:simon.daou@sulzerpumps.com Internet http://www.sulzerpumps.com
Original Message-----
From: robert gwinn@fpl.com [1]
Sent: 13 janvier, 2003 16:58 To: john.murry@sulzerpumps.com; Daou, Simon Cc: robert_mccormack@fpl.com; robert_parry(fpl.com; sean_doody(fpl.com
Subject:
Upper Pump Bearing Housing Vibration Limit Requested
Dear John and Simon,
Seabrook Station is in the process of requesting NRC regulatory relief for our containment building spray pumps. Currently, we are proposing to increase the pump vibration Alert limit to 0.4 ips Peak from the current program limit of 0.325 ips Peak. This would provide an effective pump Alert limit and still implement the intent of the In-service Test Code.
Historically, containment building spray (CBS) pumps (Bingham model "CD" Fig. B-33844, a double suction, single discharge, four vane impeller and operating at 3565 rpm) have exhibited elevated vibration levels. Vibration analysis shows that part of the elevated vibration is due the pump vane pass response and outboard bearing housing resonance. Since there can is no cost effective means to reduce this physical condition, it is recommended to establish a vendor supported upper vibration limit for the pump bearing housing vibration Alert limits.
The following graphic illustrates a typical pump outboard bearing housing horizontal vibration spectrum.
Figure I l-CBS-P-9-B Pump Outboard Bearing 13
Spectrum (Embedded image moved to file: picO5OO2.pcx)
Based on the graphic above you can clearly observe vane and 2 time vane pass frequency amplitudes. Additionally, there are raised floor vibration responses near these amplitudes that contribute to the overall vibration amplitudes. Resonance test (bump test) results show elevated response amplification at both the vane and two time vane pass frequencies. This forced vibration and the resonance testing clearly indicate that if the vane pass responses were removed, the pump bearing housing vibration levels would be well below the administrative limit of 0.325 ips Peak.
What I need close this regulatory relief request, is a document from the Vendor, you, stating that increasing the outboard bearing vibration amplitude Alert limit to 0.4 ips Peak is acceptable. This would be based on the current pump impeller vane pass response and outboard bearing resonance test results.
If you have any questions regarding this subject or need addition information please contact me at (603) 773-7056, by email Sincerely, Robert A. Gwinn.
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