ML040580121

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Fourth Ten-Year Inservice Testing (IST) Program Response to NRC RAI on Relief Request PR-03
ML040580121
Person / Time
Site: Pilgrim
Issue date: 02/10/2004
From: Bethay S
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.04.010
Download: ML040580121 (26)
v • d • e


Text

'En tergy Entergy Nuclear Operations, Inc.

Pilgrim Station 600 Rocky Hill Road Plymouth, MA 02360 February 10, 2004 U.S. Nuclear Regulatory Commission Attn: Document Control Desk 1 White Flint North 11555 Rockville Pike Rockville, MD 20852

SUBJECT:

Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station Docket No. 50-293 License No. DPR-35 Pilgrim Fourth Ten-Year Inservice Testing (IST) Program Response to NRC Request for Additional Information on Pilgrim Relief Request PR-03 LETTER NUMBER: 2.04.010

REFERENCE:

Entergy Letter No. 2.02.109, Pilgrim Fourth Ten-Year Inservice Testing

([ST) Program and Request for Approval of IST Relief Requests, dated December 6, 2002.

Dear Sir or Madam:

The attachments to this letter provide Pilgrim response to NRC Request for Additional Information (RAI) related to the IST relief request PR-03. The RAI was e-mailed to us on December 17, 2003. The attached response was discussed with the NRC staff during a telephone call on January 27, 2004.

If you have any questions or require additional information, please contact Mr. Bryan Ford, Licensing Manager, at (508) 830-8403.

Sincerely, Stephen J. Bethay Attachment 1: Pilgrim Response to NRC Request for Additional Information (4 pages)

Attachment 2: HPCI Pump IST Vibration Evaluation (19 pages) 204010 A0L( 1

Entergy Nuclear Operations, Inc. Letter Number: 2.04.010 Pilgrim Nuclear Power Station Page 2 cc: Mr. Travis Tate, Project Manager Office of Nuclear Reactor Regulation Mail Stop: 0-8B-1 U.S. Nuclear Regulatory Commission 1 White Flint North 11555 Rockville Pike Rockville, MD 20852 U.S. Nuclear Regulatory Commission Region 1 475 Allendale Road King of Prussia, PA 19406 Senior Resident Inspector Pilgrim Nuclear Power Station 204010

ATTACHMENT 1 to ENTERGY LETER NO. 2.04.010 PILGRIM RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION HIGH PRESSURE COOLANT INJECTION PUMP P-205 (MAIN/BOOSTER)

PUMP RELIEF REQUEST PR-03. TAC NO. MB8773

Reference:

Letter from Entergy Nuclear Operation, Inc, to NRC, 'Pilgrim Nuclear Power Station Fourth 10-year Inservice Testing (IST) Program," dated December 6, 2002.

NRC QUESTION 1:

In the Basis for Relief section, page 96, the licensee references an evaluation of the High Pressure Coolant Injection (HPCI) pumps done by the vendor (Byron Jackson).. Please provide a copy of the vendor's evaluation of the HPCI pump vibration characteristics and diagnosis that determined the high vibrations to be acceptable.

Response

The vibration evaluation referred to in PR-03 was performed by the licensee and includes references to information from both the pump vendor (Byron Jackson) and vibration consultant reports related to the Vermont Yankee HPCI pump. A copy of this evaluation is attached. It has been concluded based on this information that the high vibration on the HPCI Main Pump at just over 2x RPM is due primarily to a hydraulic standing wave resonance in the interconnecting piping from the Booster Pump at the pump vane-passing frequency (4x Booster Pump RPM) coinciding with structural resonance of the cross-over piping and the Main Pump pedestal when the machine is operating at the rated speed of 4000 RPM. The Main and Booster Pumps are connected via a speed reduction gear box (1.983 to 1 ratio) such that the Main Pump rated speed of 4000 RPM corresponds to a Booster Pump speed of 2017 RPM. This results in high vibration on the Main Pump bearing housings appearing at just over 2x RPM in the horizontal direction but caused by the Booster Pump excitation at 4x Booster Pump RPM, transmitted and amplified by the interconnecting cross-over piping.

It is also evident that the Main Pump has a structural resonance coinciding with 4x Booster Pump RPM. The vibration mode is the second order horizontal torsional rocking of the Main Pump pedestal. This would not ordinarily be a problem except that this resonant frequency coincides with the vane passing frequency (4x RPM) of the Booster Pump and the hydraulic resonance of the interconnecting piping. This coincidence of hydraulic excitation with both hydraulic and structural resonance results in the high vibration seen at the Main Pump but only at the discrete frequency that is just over 2x Main Pump RPM (typically at 2.017x RPM).

In addition, the first fundamental horizontal rocking mode of the Main Pump appears to coincide.

closely with 1x RPM resulting in moderately high horizontal vibration at the Main Pump 4000 RPM rated speed, particularly at the gearbox-end bearing. This structural resonance at running speed causes the Main Pump to be particularly sensitive to otherwise normal unbalance and misalignment forces.

It should be noted that the HPCI pump is a turbine-driven variable speed pump that is tested at approximately the rated speed of 4000 RPM. However, in actual design basis service for a small break LOCA the pump speed would, over a period of only a few hours, drop from the vicinity of the 4000-RPM rated speed to considerably lower speeds. At speeds significantly 204010

lower than the rated 4000 RPM the vibration resonant amplification is less with the result that the vibration due to these resonant interactions will be reduced at these lower speeds.

The purpose of the ASME OM Code for pump testing is to monitor pumps for degradation. The vibration-monitoring concept is to establish baseline values for vibration when the pump is known to be in good working condition, such as after a maintenance overhaul. From that reference point, trending is performed to monitor for degradation based on the ratio of subsequent vibration levels relative to the reference values. The OM code also establishes absolute vibration level criteria for Alert (>0.325 in/sec) and Required Action (>0.7 in/sec). In doing so, it was recognized that absolute vibration level limits (as opposed to relative change or ratio limits) are not always quantitatively linked directly with pump physical condition and the following remarks are stated in the ASME OMa Code (1996):

Vibration measurements of pumps may be foundation, driver, and piping dependent. Therefore, if initial vibration readings are high and have no obvious relationship to the pump, then vibration measurements should be taken at the driver, at the foundation, and on the piping and analyzed to ensure that the reference vibration measurements are representative of the pump and that the measured vibration levels will not prevent the pump from fulfilling its function.'

For the HPCI Pump, it has been conclusively determined that the high vibration on the Main Pump at just over 2x RPM is caused by the Booster Pump interaction with the hydraulic and structural resonance of the cross-over pipe and Main Pump pedestal when the machine is operating at the rated speed of 4000 RPM. This vibration at 4x Booster Pump RPM effectively dominates readings taken on the Main Pump such that the overall level would not reflect potentially significant changes in frequency components directly related to the operation and rotor dynamics of the Main Pump.

It has also been concluded that the vibration at 4x Booster Pump RPM is not physically detrimental to the Main Pump, the interconnecting piping, or the pump pedestal. The actual displacement associated with the vibration at 4x Booster Pump RPM (2017 RPM x 4 = 8068 RPM = 134.5 Hz) is very small (0.7 in/sec @ 134.5 Hz = 0.0017 inches peak-to-peak).

Therefore, the resulting stresses due to such deflections are correspondingly low in the crossover piping and pump pedestal. The Main Pump rotor is supported on oil film journal bearings. These bearings are very tolerant of pedestal and housing vibration at frequencies above the shaft running speed since the actual displacements are so small.

NRC QUESTION 2:

In the Basis for Relief section, second paragraph on page 97, the licensee states: 'it can be shown that the main pump vibration occurring at 4xRPM of the booster pump is not related to the condition of the main pump.' Please explain this statement in detail to support the justification.

Response

It is an important conclusion of the PNPS evaluation that the mechanical condition of the Main Pump can be adequately monitored by disregarding the single frequency component caused by the excitation at 4x Booster Pump RPM. The four-vane impeller of the Booster Pump generates the excitation force hydraulically. This small pressure pulsation force exists at the vane passing frequency (number of vanes times RPM) for all centrifugal pumps and is usually seen as a significant but not particularly troublesome component on the frequency spectrum for vibration measurements taken at the bearing housings. For the HPCI Pump, this vane passing frequency is a problem because it coincides with a hydraulic standing wave resonance in the crossover piping from the Booster Pump to the Main Pump when the machine is operating at the rated 204010

speed of 4000 RPM. That is, there is an acoustic pressure standing wave pattern, at the 4x RPM frequency, whose wavelength in water is equal to an even fraction (1/4 or 1/2) of the dimensional length inside the crossover pipe. This is the same principle on which an organ pipe generates a pure tone pneumatic pressure standing wave.

In addition, and exacerbating the problem, the Main Pump pedestal has a horizontal structural rocking mode of the pump pedestal at this same frequency when the machine is operating at the rated speed of 4000 RPM. The vibration mode is the second fundamental rocking mode, which is a torsional or twisting mode where the two end bearings move 180 degrees out of phase horizontally. The result of this coincident acoustic and structural resonance is that the Main Pump exhibits high vibration in the horizontal direction at the 4x Booster Pump RPM frequency, but it is solely due to the excitation from the Booster Pump being amplified by the coincident resonance. That is, this level of vibration at 4x Booster Pump RPM would be seen on the Main Pump bearing housings even if the Main Pump was not actually running (which is not possible to do as they are both on the same drive train).

It is proposed that, when evaluating the condition of the Main Pump, the vibration occurring at the discrete frequency component that is at exactly 4x Booster Pump RPM be disregarded. A single peak frequency component can be effectively deleted from a vibration spectrum using the mean-squared subtraction method, that is, the discrete component amplitude (in/sec peak) is squared and subtracted from the spectrum overall level squared, then the square root of that difference represents the overall vibration level that exists without the energy contributed by the deleted component. It has been found that when this method is used, the remaining vibration overall level is much more consistent, stable, and trendable.

The 4x Booster Pump RPM component has an amplitude that fluctuates significantly with very small speed and temperature changes. This is because vibration amplification is caused by the coincidence of the acoustic and structural resonance and small shifts in frequency will significantly affect such lightly damped resonant amplifications. These fluctuations due to resonant amplification effects are not due to pump degradation and therefore prevent any meaningful trending of the overall vibration level for the Main Pump. Also, the absolute vibration level criteria for the Alert and Required Action ranges is less meaningful because resonant amplification results in elevated vibration levels with otherwise normal driving forces including those due to unbalance, misalignment, and vane passing excitations.

It is proposed to remove the 4x Booster Pump RPM frequency component from the vibration spectrum of the Main Pump since its amplitude is not related to the physical condition or rotating dynamics of the Main Pump rotor or bearing system. The Main Pump vibration spectrum with this single 4x Booster Pump RPM frequency component removed has been shown to be stable and trendable and thereby more useful for monitoring actual pump condition.

NRC QUESTION 3:

In the Basis for Relief section, the description of the main and booster pump considers the pumps as separate units. For testing, the pumps are typically considered as an integral unit.

Please explain why the pumps are considered separately for purposes of this request.

Response

The Booster and Main Pumps have always been considered as separate components for vibration monitoring. They are completely separate rotor/bearing systems connected by a speed reduction gear box. The vibration is measured at each bearing housing and the same criteria is currently applied separately to all measurements. This relief request proposes to treat the Main Pump vibration points differently so that the interaction effect from the Booster Pump is 204010

effectively eliminated. This is necessary to allow meaningful trending and evaluation of the Main Pump vibration data so that it accurately reflects the physical condition of the Main Pump.

The relief request also includes raising the upper end of the Acceptable Range for the absolute vibration level applicable to both the Booster and Main Pump, which is proposed to be changed from the OM Code value of 0.325 in/sec to 0.6 in/sec. This is requested because the Booster and Main Pump overall vibration levels (minus the discrete 4x Booster Pump RPM component for the Main Pump) are normally at or above the 0.325 in/sec value such that the pumps would always be in vibration alert. The normal value of >0.7 in/sec for the Required Action Range is not proposed to be changed.

NRC QUESTION 4:

In the Alternate Testing section, Page 98, the acceptance criteria for the main and booster pumps is provided in the tables. However, the tables reference a "Note" which describes additional acceptance criteria. Please explain the apparent criteria inconsistencies in the "Note" and the tables. Please provide the detailed reasons of why the method mentioned in the Note is acceptable.

Response

The table gives the acceptance criteria that are applied to the overall vibration level. The note explains that, for the Main Pump, the frequency component at 4x Booster Pump RPM will have been removed from the overall level using the mean-squared subtraction method described above. The detailed reasons why this method is acceptable have been discussed in the previous responses. In addition to the modified criteria for the Alert overall vibration level (Alert

>0.6 in/sec to 0.7 in/sec, Required Action > 0.7 in/sec) and the normal ratios of overall levels to the reference (Alert >2.5Vr to 6 Vr, Required Action > 6 Vr), in all cases the pump vibration spectra will be reviewed and the note states that all discrete frequency components (other than 4x Booster Pump RPM) on the frequency spectra will have the amplitude of the peak compared to an Acceptable Range upper limit of 1.05 Vr and an Alert upper limit of 1.3 Vr where Vr is the reference overall vibration level (minus 4x Booster Pump RPM component for the Main Pump).

These reviews of the frequency spectrum data ensure that any significant change in the vibration signature will be noted regardless of whether the severity causes the overall level to exceed its criteria. For example, if the overall vibration level is acceptable but the 1x RPM component has increased to greater than 1.05 times the reference value overall level (Vr), then the pump will be placed in vibration alert.

204010

ATTACHMENT 2 to "PILGRIM RESPONSE TO NRC REQUESTFOR ADDITIONAL INFORMATION" HPCI PUMP IST VIBRATION EVALUATION (19 paaes) 204010

EXHIBIT 3 Sheet 1 of I RTYPE A4.17

) E SR RESPONSE MEMORANDUM To: L. _CSCHNcL-ING From: NED Doc No(s):ERMqo-44fr Date(s): 6-I7-?4 Rev. 2

SUBJECT:

ESR# 9O-f46 Date: 2-26-?o -

Rev. o TITLE: I-IPCT PUMP IST VIBRATION CONCERNS Cl INTERIM RESPONSE Reference Memo(s):e 0 FINAL RESPONSE Initial Distribution: Original to Responsible Manager I J-. L IE9

_._ Response Prepared By: PDa. HARI'I Lead Division Manager: .TP. 6;ERETY Others: ESR Prepared By: J L. A3IN i A I _

FOR INTERIM RESPONSE ONLY THIS CRM PROVIDES AN UPIVATED RSPONSE EXTPRODUCT:

To E5R 0o-146 oN 4PCI PUMP V&SRAT1oM.

TARGE TART DATE TARGET FINI DATE/

Cot4lTENTS # PAGES ESTIMATED MA\HA RESPOSE tMEMOIRANIWUM 8 A7T-ACHIMENTS i To 8 q COGNIZA NHGINEER FER ?O-146 2 ES REMARKS:

TOTA L 17 PAGES PNPS ACTION REQUIRED? %3 YES E NO NESD Review and Approval: (No distribution required)

I Reviewed: Approved UN?/ A7____

Signature NuclearVmineering ices Mgr./Date Design Change Pending?

L YES 3 NO LI UNDER REVIEW Requesting Department Review and Approval:

Rejected:

Approved: 2~2L

/

-J J ----

shn ~ure Request NqDept. Mgr.iDate Secondary Distribution: ERM Division Manager: T.1GERFTY ERM Preparer: P.-P. HARIZ7 -411

6. McCARTHY NOP84EI Rev. 5 Page 14 of 22

Response to ESR 90-146 ERM 90-445 Rev. 2 Page 2 of 8 PURPOSE To provide an updated response to the HPCI Pump IST vibration concerns as addressed in ERM 90-445 Rev. 1. The previous recommendation that PNPS replace the rotating element of the Booster Pump has been reconsidered.

SCOPE The following references on HPCI Pump vibration were reviewed:

1) Byron Jackson Tech Note No. 9112-80-018 (see Attach. 8)
2) ERM 89-311,90-265, 90-445 Rev. 1
3) NED CSJA #91-008 (LTP No. 577)
4) Vibration test report for Vermont Yankee's HPCI Pump (ARC Report dated 3-9-87).
5) Various Yankee Atomic documents related to their EDCR 88-401 HPCI Pump impeller replacement.
6) Vibration data from the PNPS-CSI database for P-205 for eight in-service tests from July 1992 to May 1994.

RESULTS FROM REVIEW OF HPCI PUMP VIBRATION Refer to Attachment 1 for information on the vibration frequencies of interest discussed below.

1) The PNPS HPCI Pump exhibits vibration characteristics that have been diagnosed by Byron Jackson as being due primarily to a hydraulic standing wave resonance in the interconnecting piping at the Booster Pump vane-passing frequency (4x RPM) coinciding with structural resonances of the piping and the Main Pump. This results in high vibration on the Main Pump bearing housings appearing at approximately 2x RPM in the horizontal direction but caused by the Booster Pump excitation at 4x RPM of the Booster Pump. Prior to Byron Jackson's Tech Note on high vibration, it was often misdiagnosed as being caused primarily by misalignment of the turbine to Main Pump which would also induce high 2x RPM vibration.

(see Attach. 2)

2) The Main Pump vibration level often exceeds 0.7 in/sec Peak at 2x RPM.

Readings as high as 1.3 in/sec Peak at 2x RPM have been recorded (29-JUL-92). It is expected that the amplitude is affected by small changes in turbine speed and condensate water temperature which affect the resonant amplification.

3) From the ARC Report to VY and the PNPS data, it is evident that the Main Pump has a structural resonance coinciding with 2x RPM. The vi6ration mode shape appears to be a horizontal torsional rocking of the pump on the four pedestals with P3 and P4 moving out-of-phase with greater motion on the P3 turbine-side bearing. This would not ordinarily be a problem except that this frequency coincides with the vane passing frequency (4x RPM)-of the Booster Pump and the hydraulic resonance of the interconnecting piping.
4) There is also moderately high vibration at 1x RPM on the Main Pump P4 bearing (gear-side) horizontally. Readings as high as 0.50 in/sec Peak

Response to ESR 90-146 ERM 90445 Rev. 2 Page 3 of 8 at lx RPM have been recorded (30-MAY-93). From the PNPS data, there is evidence that the Main Pump may also have a structural resonance near lx RPM horizontally that may be the first fundamental side-to-side lateral rocking mode of the pump with P3 and P4 moving in-phase but with greater motion on the P4 gear-side bearing. (see Attach. 3)

5) The Booster Pump shows very low vibration at lx RPM. There is a moderate level at the 4x RPM vane-passing frequency horizontally. Readings as high as 0.28 in/sec Peak at 4x RPM on P8 (30-SEP-93) have been recorded.

(see Attach. 4)

6) The vibration data taken since July 1993 on the Booster Pump shows that the integrated velocity and double-integrated displacement signals are contaminated by a periodic transient that results in unrealistically high overall levels for the spectrum. The transient causes low frequency energy to appear on the integrated velocity and displacement spectrums which greatly inflates the overall spectrum value. The Booster Pump rotor is supported on ball bearings that are capable of generating or transmitting transients that would create this effect. Potential causes for-this-include excessive end-play in the thrust bearing which is a duplex angular-contact ball bearing arrangement. The gear coupling may be locking up due to old or ineffective grease on the gear teeth thereby transmitting gear vibration to the pump. This should be further investigated to determine the actual cause. (see Attach. 5)

Re3ponse to ESR 90-146 ERM 90-445 Rev. 2 Page 4 of 8 CONCLUS IONS The Byron Jackson recommendation to replace the Booster Pump four vane impeller with a five vane impeller is not the best solution for PNPS and should not be performed. It is anticipated that the Main Pump vibration level would still be within the ASME OM Part 6 Alert Range after the Booster Pump impeller modification. The Main Pump has moderately high vibration at Ix RPM that is not related to the vane passing excitation from the Booster Pump impeller and associated resonances at 4x Booster Pump RPM.

The vibration characteristics are predominantly a function of the pump design and should be identified as such rather than attributed to pump degradation.

The high vibration has been present to the same order of magnitude since the pump was new. Additional measurements are recommended to further characterize the structural resonances that affect pump vibration.

Application of ASME Section XI and OM Part 6 The Inservice Testing (IST) of the HPCI Pump is currently done per ASME BPVC 1986 Edition,Section XI, Subsection IWP. This code uses mils P-P vibratory displacement criteria with a required action limit that is dependent on the established reference level for the pump vibration. The OM Part 6 code is the current ASME IST code that will supersede the IWP code in the next PNPS code update. The OM code also uses reference vibration values but, in addition, it places an upper ceiling value on vibration using in/sec velocity criteria.

The absolute limit is irrespective of the reference level. It is this absolute limit that was the original cause for concern regarding the HPCI pump future IST tests.

The application of absolute vibration limits and requirements for "correction" of high vibration exceeding those limits is open to interpretation. The code requires that pumps which are in the "Required Action Range" be declared inoperable until the cause of the deviation has been determined and the condition corrected. The 1986 Edition of Sec. XI (IWP-3230) allowed that:

Correction shall be either replacement or repair per IWP-31 11, or shall be an analysis to demonstrate that the condition does not Impair pump operability and that the pump will still fulfill its function.

A new set of reference values shall be established after such analysis. '

The ASME OM Part 6 requirements for pump testing includes a Required Action limit of 0.70 in/sec Peak for pump bearing housing vibration. The most recent ASME OMb-1989 Part 6 states that (Sec. 4.3):

Vibration measurements of pumps may be foundation, driver, and piping dependent. Therefore, If Initial vibration readings are high and have no obvious relationship to the pump, then vibration measurements should be taken at the driver, at the foundation, and on the piping and analyzed to ensure that the reference vibration measurements are representative of the pump and that the measured vibration levels will not prevent the pump from fulfilling its function. '

Assuming that "high" readings include those that exceed 0.70 in/sec peak, it can be shown that the Main Pump vibration occurring at 4x RPM of the Booster Pump is not related to the condition of the Main Pump. The high vibration is caused by hydraulic and structural resonances that are excited by the vane-

Response to ESR 90-146 ERM 90-445 Rev. 2 Page 5 of 8 passing frequency at 4x RPM of the Booster Pump. The actual vibration of interest for the Main Pump includes only those frequency components generated by the rotordynamics of the pump itself which include 1/2x, lx, and 2x RPM, and at the Main Pump vane-passing frequency (5x RPM) and its related harmonics.

If the vibration frequency component at 4x Booster Pump RPM is subtracted from the Main Pump vibration spectrum, then the remaining vibration which is attributed to the Main Pump is below the Part 6 Required Action Range. This corrected vibration level provides a more representative measurement of the pump condition to be used for trending.

This method of vibration level correction was applied to the historical spectrums with the results given in the attached table. The 4x Booster Pump RPM component was taken out of the calculation for the Main Pump overall vibration level. This data shows that when the 4x Booster Pump RPM component is deleted from the Main Pump vibration, the level is below the Required Action Range (>0.70 in/sec) but still within the Alert Range (>0.325 in/sec).

Response to ESR 90-146 ERM 90445 Rev. 2 Page 6 of 8 RECOMMENDATIONS Interim Use of 1986 ASME Section XI - Subsection IWP The Inservice Testing program is currently using reference value vibration displacement readings in accordance with Table IWP-3100-2 with satisfactory results. ERM 90-445, Rev. I recommended the use of "administrative" reference values of 5 mils P-P for the Main Pump and 4 mils P-P for the Booster Pump.

The current reference values are lower than these. If an IST measurement exceeds the Alert limit, the vibration data should be reviewed to determine if it is caused by the 4x Booster Pump RPM resonance effect. If this is the primary contributor, then a new reference value should be established at the higher overall level.

Future Application of ASME OM Part 6 Prepare a vibration analysis report to justify accepting the Main and Booster Pump vibration as-is with the reference level for the Main Pump based on the vibration spectrum exclusive of the 4x Booster Pump RPM component. The reference levels for both the Main and Booster Pumps will be in the Alert Range specified in Part 6 as from above 0.325 to 0.70 in/sec peak.

HPCI Pump Potential Modifications Some plants have opted to follow Byron Jackson's recommendation to replace the Booster Pump impeller. Based on the review by MED, it is recommended that PNPS instead do the following:

1) Perform additional vibration analysis of the HPCI Pump to determine acceptability and establish reference levels per ASME OM Part 6 and to characterize the vibration resonances.
2) Evaluate the feasibility of doing a stiffening modification of the Main Pump pedestals to raise the natural frequencies of the major rocking modes and thereby detune these resonances away from lx and 2x RPM of the Main Pump. Jhis may reduce the amplitude of the vibration on the Main Pump.

Booster Pump Evaluation and Maintenance The gear coupling from the Booster Pump to the gear reducer should be disassembled, thoroughly cleaned, and lubricated with an appropriate extreme pressure grease. While the coupling spacer is removed, the pump rotor end play should be measured and verified as correct per Byron Jackson (refer to Attach. 6).

Response to ESR 90-146 ERM 90-445 Rev. 2 Page 7 of 8 Vibration Data Requirements The following data is needed to complete an analysis of the HPCI Pump vibration, refer to the Attachment 7 drawing for measurement locations:

1) Non-operating impact testing to determine the natural frequencies and fundamental mode shapes for the Main Pump and Booster Pump in the horizontal direction, and the interconnecting piping horizontal and vertical.
2) Operating vibration measurements at all pump bearings (P3 to P8) and 17 points as shown on the attached drawing:

a) P3 to P8 HORZ, VERT, & AXIAL Bearing Housing Vibration Velocity Spectrum 3200 lines 0 to 1000 Hz Velocity Time History with 1024 Points for P3 & P4 Acceleration Time History with 1024 Points for P7 & P8 Note: Use analog integration for P3 & P4 and digital integration for P7 and P8 in analyzer setup.

b)P7 and P8 HORZ, VERT, & AXIAL Bearing Housing Vibration Acceleration Spectrum 3200 lines 0 to 10,000 Hz Acceleration Time History with 1024 Points c)Main Pump HORZ Locations for Operating Mode Shape 1 Point on Casing Flange Midway Between Bearings 6 Points on Pedestals Velocity Spectrum -3200 lines 0 to 1000 Hz Velocity Time History with 1024 Points d) Interconnecting Pipe HORZ & VERT Pipe Vibration -

4 Points on Flanges at Booster and Main Pump 6 Points on Crossover Pipe Velocity Spectrum 3200 lines 0 to 1000 Hz Velocity Time History with 1024 Points Note: Condensate water temperature should be recorded whenever vibration readings are taken.

Rcsponse to ESR 90-146 ERM 90-445 Rev. 2 Page 8 of 8 HPCI Main & Booster Pump Overall Vibration Velocity Levels' Measurements Per ASME OM Part 65 Horizontal Direction In/Sec Peak Overall Spectrum Level Main Pump Overall 10-1000 Hz Minus 4x BP RPM Date P3H2 P4H2 P7H2 P8H2 P3H3 P4H3 29-JUL-92 0.984 0.665 0.233 0.341 0.494 0.473 24-NOV-92 0.712 0.577 0.298 0.371 0.342 0.482 30-MAY-93 0.817 0.751 0.293 0.353 0.360 0.567 01-JUL-93 1.05 0.762 0.9565 N/A 0.339 0.482 30-SEP-93 0.889 0.667 0.5325 0.5845 0.323 0.461 06-JAN-94 0.782 0.439 0.4595 0.4315 0.343 0.383 09-MAR-94 ' 0.708 0.512 0.4135 0.3795 0.320 0.439 25-MAY-94 0.858 0.687 0.4185 0.3755 0.4034 0.5654 Notes:

1. All data Isfrom the CSI vibration database and is in terms of in/sec peak velocity.
2. Overall spectrum levels are for the entire velocity spectrum from 10 to 1000 Hz.
3. The level for the 'Main Pump Overall Minus 4x BP RPM" was calculated by deleting the 4x Booster Pump (BP) RPM frequency component from the Main Pump overall level power summation. The historical data before 25-MAY-94 did not have sufficient frequency reso-lution to separate the 4x Booster Pump RPM (corresponding to 2.01x Main Pump RPM) from the 2x Main Pump RPM on the vibration spectrum. The deleted component therefore includes both frequency components.
4. The 25-MAY-94 data was taken with maximum 3200 line frequency resolution to allow separating the 2x Main Pump RPM frequency component from the 4x Booster Pump RPM.

This results Inslightly higher Overall Minus 4x BP readings for this data.

5. These P7H & P8H readings were influenced by a periodic low frequency transient effect that contaminates the integrated velocity spectrum overall level giving a falsely high value.
6. ASME OMb-1 989 Part 6 specifies an Alert Range of >0.325 in/sec peak and a Required Action Range of >0.70 in/sec peak for overall vibration readings from a minimum of 1/3x RPM to 1000 Hz.
7. P3H = Main Pump Turbine-End Horizontal P4H = Main Pump Gear-End Horizontal P7H = Booster Pump Inboard Horizontal P8H = Booster Pump Outboard Horizootal

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[ NPD TELEPHONE CALL RECORD CD NOD TOPAT GOMUALE/ PAT TRLPHI4 DAT] E 4-7-94 TIM /600 FRom  ?>Yo1 TACKSoW SW/rp COMPY/AOFFICE L. A.

SUBJECT:

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Copies To: G. MCCA'l"H9 SIGNED ? HAOEII2I DATE 6 - ;?-

Chrono File No: 2-0.7 Subject File No: Page 1 iof BECo Form X-5104

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FRY\ ?o-445 Rev. 2 No. 9112-80-018 HPCI Pump Vibration

... Replacement of booster pump impeller reduces high pressure injection pump vibration...

PROBLEM High vibration levels have been observed on injection pump bearing housings of high pressure coolant injection (HPCI) pump sets. HPCI pumps are standby units periodically operated for approximately one-half hour in a surveillance testing mode. Observed bearing housing vibration levels may vary from test to test.

CAUSE High vibration levels on the injection pump occur at the vane passing frequency of the type DVS booster pump impeller. A HPCI pump set consists of a steam turbine drive, a type DVMX high pressure injection pump, gear reducer, a type DVS booster pump, and interconnecting piping. At operating conditions, the booster pump discharge pressure pulsations generate an acoustic resonance in the piping which, in turn, causes high vibration of the type DVMX injection pump. The injection pump support structure may also be resonant at this frequency in the horizontal direction.

SOLUTION If bearing housing vibrations exceed the ALERT limits specified in the ASME Boiler and Pressure Vessel Code, Section Xl, Subsection IWP-3000, the following actions are recommended:

  • Verify correct dynamic alignment of all shaft couplings.
  • Verify acoustic resonant condition from measured flow, RPM, water temperature, and vibration frequency.
  • Replace four vane booster pump impeller with a staggered five vane impeller.

ERA M 90-445 Rev. Z A7T,4c4MJT~r 8 Ma2 of 2 TECHNICAL The speed ratio of the injection pump to the booster pump causes the vane passing frequency of the four vane booster pump impeller to differ from the twice-per-revolution DISCUSSION frequency of the injection pump by only one-half percent. Consequently, vibrations from a resonant vane passing condition caused by the booster pump can easily be interpreted as a misalignment of the DVMX injection pump shaft.

A synchronous spectrum averaging technique must be used to detect the small difference between the two frequencies. This technique averages the bearing housing vibration data with a once-per-revolution tachometer reference signal from the DVMX. Nonsynchronous vibration components will be filtered leaving only components related to the rotational frequency of the DVMX, such as coupling misalignment. Therefore, if the original twice-per-revolution vibration is caused by a misaligned condition, it will remain. If it is caused by pressure pulsations occurring at the DVS impeller vane passing frequency, the amplitudes will be significantly reduced or eliminated. This diagnosis may be confirmed by averaging the DVMX bearing housing vibration data with a tachometer reference signal from the DVS pump. In HPCI pump sets, a resonant frequency measured on the high pressure pump but synchronous to the booster pump is usually the result of a standing wave resonance in the interconnecting piping. High vibration occurs when the standing wave resonance coincides with a structural natural frequency of the DVMX pump and base system.

Pumping systems in which the vane passing pressure pulsations form standing waves in the attached piping are not unusual, especially if the pumps have a variable speed driver.

Standing waves are highly dependent upon water temperature. Thus, measured vibration amplitudes often vary from test to test.

CORRECTIVE The following corrective actions are possible:

ACTIONS

  • Change the number of vanes in the booster pump impeller
  • Change the length of the interconnecting piping
  • Install an acoustic filter in the interconnecting pipe
  • Alter the mounted structural natural frequncy of the injection pump.

The most cost-effective solution has been to replace the existing four vane booster pump impeller with a five vane impeller to raise the vane passing frequency 25 percent above the standing wave resonant frequency.

AFFECTED This technical service bulletin applies to HPCI pump sets installed at UNITS Commonwealth Edison Dresden No. 2 & 3 Ouad Cities No. 1 & 2 Nebraska Public Power District Cooper Station Yankee Atomic Power Vermont Yankee Boston Edison Pilgrim Station N.Y. State Power Authority J.A.Fitzpatrick TVA Browns Ferry No. 1, 2, 3 Philadelphia Electric Co. Peach Bottom 2 & 3 Limerick 1 & 2 Georgia Power E.I. Hatch Public Service Electric and Gas Hope Creek 1 & 2 Pennsylvania Power and Light Susquehanna 1 & 2 Taiwan Power Chinsan 1 & 2 Contact Dr. Kent A. Huber at BWIIP International, Inc., Pump Division. for further details.

SBWIP International, Inc. 200 Long Beach Telephone fE1 Pump Division Oceangate California 213 436 os0 Boulevard 90802 Telex Suite 900 181105

ENGINEERING SERVICE REQUEST RTyp-e A4110

~

F-59 9°- i46 REOUESTING DEPARTMENT USE 4 ; E ?age I of 2 o: Nuc. Engr. Mangr. 53 From: D 1 A 4p 2 2/6/9C Requesting Dept. Mgr. Date - - NED USE 0 El Responsible Manager J .A. Seery El REV x ESR Number (in Requesting Dept) E3 Date Final Product Needed 3/26/90 90 'I(O, CPrepared By: J. L. S Fin~J1, 2 /2 6/90 Division RS&PD Cost Area OR DateR EC E ICVE .E I Tel 4 PI -L L UIMIu 4 ItI TI IiVI I IR I IId ?I l!AtR I9 -G CIO Nl cI Et PN 1i I I I'I [__SECTIONMANAGO; I D Problem Summary (Incl. Root Cause) See Attachrment L AS Lead Div. IWP Number

!_ Req. Anal. Due Date Attachments ES 0 _

F1- Suggested Solution(s) ajL Lead Div. Mangr.

TLead Div. EnFineer Altachments SMO First Product , £ Desired Engr. Product See Attachment Target Start Est ManHours /

C Plant Condition to Implement N/A W.O. No. -

- Account No.

1 Supporting Doc. & Rel. PNPS 8. 5. J.1,. Prqq Q T I7 Instructions ERM,1 89-311 Attachments YES/NO i Justification/lmpactNotPeoatisfactorv IfPNoT TrrmUnsatisfat baseline data will be used for detpermining -,grnne--

able HPCI Tcumn) nerformance. .

ESR Remarks

- Artachments YES/NO Sys. Name HPCI SsNubr 23 ComponentName:HPCI pPuTnp' - Comp. No. P-205 i Input Div. Mgr.

'Qual'nyClass Q Priority W ' Input I Div. Mgr.

Onsfte-OER, cc:

B Initial Distri ion ginal lo NED's Department Manager 1 Second Distribution: Original to the

-1 U NED Lead Div. Mgrcc:Lead Div Engr, cc: Preparer, Requesting Dept Mgr., NMSD-Braintree. Onsite-OER, NED, 'NMSDDir of O'u Other(s): at. Preoarer:

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, +,

I rt:>.IVED

i. --- I D Input Div.Engr.

ItExhi ,1t F.S.&M (C. Cr! '

1990 I

EsR 9o-146 Attachment to ESR # P oe 2 of 2 PROBLEM

SUMMARY

.HPCI pump IST vibration readings appear to be rough. ESR 89-244 was generated to evaluate the acceptability of these vibration amplitudes for continuous HPCI pump operation. The response memo to ESR 89-244 recommended that-strip charts (full spectrum data) be taken for at least 3 additional turbine/pump runs to establish consistency for reference data purposes.

Additional vibration data has been collected during 4 turbine/pump runs and the following conditions have been observed:

1. There are velocity peaks on the HPCI Main Pump Inboard bearing that should be investigated as a potential long term concern.
2. There continues to be a low frequency vibration of high amplitude that sometimes masks other meaningful peaks in the vibration spectrum.
3. The HPCI main pump displacement readings are inconsistent and require additional review for IST vibration reference value acceptability.

SUGGESTED SOLUTIONS

1. Evaluate velocity vibration for the HPCI Main Pump Inboard bearing and determine if this condition should be improved as part of long term corrective action.
2. Review and determine cause for low frequency vibration of the HPCI pump so that this condition may be appropriately assessed ana monitored.
3. With the above information, assist RS&PD in establishing acceptable HPCI pump vibration reference values.

DESIRED ENGINEERING PRODUCT

1. Evaluation of HPCI vibration data to fully assess present pump condition.
2. Assistance in establishing vibration baseline data for IST reference values.
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