ML20064G173

Reactor Coolant Pump 3P002 Mechanical Seal Failure

ML20064G173
Person / Time
Site:	San Onofre
Issue date:	02/28/1994
From:	Gartland G, Rudolph J, Strom W SOUTHERN CALIFORNIA EDISON CO.
To:
Shared Package
ML20064G166	List: 05000362/LER-1993-006, Forwards RCE-94-002, Reactor Coolant Pump 3P002 Mechanical Seal Failure, as Committed in LER 93-006,dtd 940112 ML20064G173
References
RCE-94-002, RCE-94-2, NUDOCS 9403160050
Download: ML20064G173 (146)

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1 REACTOR COOLANT PUMP 3P002 MECHANICAL SEAL FAILURE RCE 94-002 i

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1 CLARIFICATION OF PURPOSE This report is intended to be a self-critical use of hindsight to identify all problems and the sources of those problems. The root causes identified in this report were discovered and analyzed using allinformation and results available at the time it was written. All such information was, of course, not available during the timeframe in which relevant actions were taken and decisions were made.

The purpose of using such a self-critical approach is to provide the most comprehensive analysis possible for identifying " lessons learned" as a basis for improving future performance, The use of an open, documented self-critical analysis program is imperative in the nuclear power industry and cannot be compromised or confused with a management prudency assessment.

Thus, this report does not attempt to make a balancedjudgement of the prudency or reasonableness of any of the actions or decisions that were taken by vendors, utility management, orindividual personnel based on the information that was known or available to them at the time.

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REACTOR COOLANT PUMP 3P002 MECHANICAL SEAL FAILURE RCE 94-002 l

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AUTHORED BY:

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[G. WAartland

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ISEG/ Root Cause Engineering b

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Jim Rudolph

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Station Technical Engineering II/

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REVIEWED BY:

W. W. Strom, Supervisor K. lierschthal N

Independent Safety Engineering Manager NSSS Engineering APPROVED BY:

M C. Chiu, Marpger Safety Engi ering i

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RCE 94-002 Reactcr coolant Pwnp Seal Damage, SONGS 3 Febrwry 28,1994 i

TABLE OF CONTENTS I

4 BACKGROUND......................................................

.i DESCRIPTION OF REACTOR COOLANT PUMP SEAL CARTRIDGE...............

5 DESCRIPTION OF THE MOTOR ASSEMBLY 6

FAILURE SCENARIO INVESTIG ATION....

6 i

ROOT CAUSE IDENTIFICATION 8

CORRECTIVE ACTIONS TO PREVENT RECURRENCE........................ 11 IDENTIFIC ATION OF OTHER SUSCEPTIBLE ITEMS.......................... 12 12 10CFR21 EVALU ATIO N...............

OPERATING EXPERIENCE WITH SIMILAR EVENTS.......................... 12 APPENDIX A - B&W NUCLEAR REPORT APPENDIX B - RCP MOTOR AMPS i

APPENDIX C - RCP START SEQUENCE APPENDIX D - RCP VIBRATION DATA APPENDIX E - EVALUATION OF UNIT 2 i

APPENDIX F - 3P002 MAINTENANCE HISTORY APPENDlX G - TOLERANCE STUDY APPENDIX H - VISUAL INSPECTION OF LOWER RADIAL BEARING J

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RCE 94-002 Reactor coobnt Pump Seal Damage, SONGS 3 Febnery 28,1994 EXECUTIVE

SUMMARY

EVENT DESCRIPTION On tuesday, December 7,1993, water was discovered issuing from the top of reactor coolant pump 3P002 during system hydrostatic testing of the RCS after the Unit refueling. The reactor coolant system was at 500 degrees Fahrenheit and 2300 psi.

Inspection of the pump mechanical seal revealed that damage had occurred to both the vapor stage and the thrust ring cover. The seal assembly showed indications of contact between the rotating shaft sleeve and the stationary seal sleeve in the area of the second and fourth seal stages. The "O" ring seal between the vapor stage seal gland and the secondary shaft sleeve was severely degraded. The carbon bushing in the thrust ring cover was wom and there was indication of metal to metal contact on the upper land of the cover.

Measurements of pump alignment indicated that the motor shaft was misaligned with the pump by approximately.045 inch TIR and the measured float in the lower motor bearing was

.025 inch (MO 93120582)

The seal assembly was replaced and the motor partially realigned per MO 93120582. Full motor movement to complete the realignment was not possible because of interference between the motor housing and the rabbited joint of the support structure. Total motor movement was.020 inch. NCR 93120045 was generated to document.013 inch "as left" misalignment between the motor and the pump.

On December 13,1993, the pump was started and a higher pitched whine than the other RCP's was noted by the cog engineer and an operator in the vicinity (E-mail trom J Rudolph dated 12/14/94). Rubbing between the thrust sleeve and the carbon bushing and upper land of the thrust ring cover resulted in heating of the thrust sleeve and flashing of carbon dust from the seal. The pump was tripped by operator action.

ROOT CAUSE December 7,1993 Event Prior to the December 7,1993 event the thrust ring cover outside diameter was undersized.

which allowed the cover to be installed up to.030 inch eccentric to the centerline of the pump.

This eccentricity along with a loose lower motor bearing and misalignment between motor and pump allowed contact between the thrust ring and the carbon insert in the thrust ring cover.

After the carbon bushing was worn away, there was contact between the metal ring on the cover and the thrust ring. The contact occurred on one side of the shaft which had the dynam., high spot.

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RCE 94-002 Reactor cooknt Pump Seal Damage, SONGS 3 February 28,1994 Cover ring wear as described above also allowed contact between the primary and secondary seal sleeves of the vapor stage which caused heating of the gland O-ring which resulted in the water / steam leakage.

t Visual inspection of the lower radial bearing indicated that the bearing shoe adjusting screw lock nut at the 5:00 o' clock position was loose prior to the event. A shutdown transient may have occurred at the end of the run which caused the shoe to back out increasing the clearances in the bearing.

December 12,1993 Event The swing check method used to determine the lower radial bearing clearances prior to the December 12 event used jacking screws to move the shaft against the bearing shoes. The location of the screws were such that the shaft did not contact the 5:00 o' clock shoe which had moved during the first event and the clearances were underestimated. The increased clearances, above those of the first event, more than made up for the motor movement and resulted in higher vibration amplitudes.

The vibration levels were sufficient to allow the thrust ring to contact the carbon bushing in the thrust ring. When the carbon had wom to the point where metal to metal contact was possible, a hot spot resulted and flashing of the carbon dust occurred. The pump was stopped when the carbon flashing and high (off scale) vibration was noted.

t The bearing housing support bolting was found loose with one bolt broken (MO 93121067).

This looseness, if combined with compression of the insulating material, could have allowed movement of the lower radial bearing with respect to the motor centeriine, but no definitive measurements of either the clearances or the insulating material thicknesses were taken.

CORRECTIVE ACTIONS Unit 3 Corrective actions taken include the rebuild effort on pump 3P002 and inspections of reactor coolant pumps 3P001, P003 and 3P004. MO93121339 checked the 3P001 lower radial bearing and the bolting for the bearing housing support and found all botting tight and acceptable. MO93121305 inspected the 3P003 lower bearings and found all bolts loose and 2 bolts missing. The missing bolts were replaced and all bolts were tightened to manufacturers specification of 165 ft lbs. 3P004 was checked per MO93121342 and the bearings and bolting were found to be acceptable.

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RCE 94-002 Reactor coobnt Pump SealDamage, SONGS 3 February 28,1994 Unit 2 Continuous vibration monitoring will be used to detect changes in a RCP bearing support system that could be detrimental the seal. Indications that will be monitored are shaft centerline position, displacements and phase angles. The shaft centerline position will be an effective tool that will indicate a change in the bearing support system. A change in vibration displacement could be indicative of a change in the shaft bearing support system but will most likely be an indicator only after shaft rubbing has begun to occur. A change in phase angle would indicate a change in the. shaft "high spot" position (relative to the keyphasor) that might be caused by a rub.

Inspections of the Unit 2 pumps have been planned and will be implemented at the next available outage of sufficient duration.

A RCTS item will be issued requesting the following actions:

1) Assess the need for periodic inspections and overhaul of the RCP motor bearings and bearing structure assemblies support. (STEC) i

2) Assess the need for pump motor alignments after specific maintenance activities. (STEC)

3) implement periodic maintenance changes as a result of 1 and 2. (Station Maintenance)

4) Review the need for motor bearing inspections on similar pumps. (Station Maintenance)

5) implement improved RCP thrust ring cover verifications. (Station Maintenance)

OTHER SUSCEPTIBLE ITEMS The design of the reactor coolant pumps / motors is specific to this application and other i

pumps are not considered to be susceptible to this problem.

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i RCE 94-002 Reactor coolant Pump Seal Damage, SONGS 3 February 28,1994 BACKGROUND Reactor coolant pump 3P002 was secured after 69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br /> of continuous operation on December 7,1993 after small amounts of water were observed leaking past the pump vapor stage seal. Inspections after the pump was secured revealed that rubbing had occurred between the rotating thrust sleeve (item 475) and the stationary carbon insert (item 141) in the thrust ring cover assembly (item 125). Heating of these components was evidenced by discoloration of both the thrust sleeve and the thrust ring cover. After disassembly of the seal, localized rubbing between the primary shaft sleeve (item 453) and the secondary shaft sleeve (item 435) in the vapor stage was evidenced by markings on both parts. The secondary sleeve to gland assembly (item 424) "O" ring (item 436) was heat damaged and incapable of sealing.

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The "as-found" total indicated reading (TIR) between the motor shaft and the seal adapter housing was 0.045 inch (MO 93120582). The outside diameter of the thrust ring cover was found to be.030 inch undersize which permitted it to be placed off center in the seal adapter 4

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RCE 94-002 Reactor coolant Putnp Seal Damage, SONGS 3 Febetary 28,1994 housing. This could reduce the clearance between the carbon bushing and the thrust sleeve below design values.

The thrust ring cover was replaced with a dimensionally correct part (MO 93120549) and a new mechanical seal was installed (MO 93120294). The motor was realigned (MO 93120582), however, the motor rabbited joint in the drive mount would only allow.020 inch movement and the shaft still showed.013 inch TIR misalignment. This condition was accepted by station management and approved by the pump vendor, BW/IP. NCR 93120045 was written to document the out of tolerance condition.

The pump was operated again on December 13,1993. Localized heating and carbon dust flashing were noted in the area of the thrust sleeve / thrust ring cover and the pump was secured after approximately 26 minutes of operation. All seal parameters were observed to be within normal limits except for a small staging pressure excursion after the pump was secured. Vibration levels at the time of shutdown were observed to be approximately.030 inch. Additional vibration data can be found in Appendix D.

The motor bearing shell and oil pan assembly was removed and the lower bearings were inspected (MO93121067). The "as found" diametral clearance between the motor shaft and the bearing was measured and found to be approximately.058 inch and the shaft was hard against the bearing shoe at the 9 O' clock position before the shaft could be centered. The vendor recommended diametral clearance between the shaft and bearing shoes is.010 inch.

The centerline of the lower bearing was found to be.054 inch off the theoretical motor centerline. The bearing pad at the "5 O' clock" position had a large clearance caused by its adjusting screw having loosened and backed out. The bolts that fasten the lower motor bearing housing assembly to the motor frame were all loose and one bolt was reported broken (MO 93120670).

The bearing shoes were inspected and the condition of the babbit was found to be acceptable, the motor shaft was centered and the bearing clearances were set and locked.

The motor was aligned to the pump (MO 93120875) and all measurements were found to be acceptable except the motor coupling flange runout which was.010 inch vs. 004 inch per the j

I vendor manual. NCR 93120069 documented this non-conformance and accepted the condition "as is" DESCRIPTION OF REACTOR COOLANT PUMP SEAL CARTRIDGE i

The reactor coolant pump seal cartridge consists of four face type mechanical seals; three full pressure seals mounted in tandem, and a fourth low pressure vapor seal designed to withstand system operating pressure when the pump is not operating. A controlled bleedoff flow of approximately 1.5 gallons per minute through the seal is used to cool the seals and equalize the pressure drop across each seal. The bleedoff flow is collected in the volume control tank. Leakage past the vapor seal is collected in the containment sump.

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RCE 94-002 Reactor coolant Pump Seal Damage, SONGS 3 Febnsary 28,1994 The seal cartridge is cooled by allowing controlled leakage from the RCS to flow through a heat exchanger integral with the pump case and then past the seal cartridge assembly. The seals are capable of operation for up to three minutes with no cooling water with no seal damage. Seal design accommodates full RCS operating pressure; however, the first three seals of the cartridge assembly normally operate with a differential pressure of one third of 1

system pressure, with a very small differential pressure across the vapor seal..The seal rotors are tungsten carbide operating against a graphite stator.

DESCRIPTION OF THE MOTOR ASSEMBLY The motor assembly includes the motor, air coolers, motor bearing lubrication oil lift pumps, motor shaft upper and lower radial and axial thrust bearings, flywheel, and anti-reverse rotation device. Cooling water to the motor air cooler heat exchangers and oil coolers is t

supplied by the component cooling water system. The flywheel and motor-pump rotating assembly function to improve the coastdown characteristics of the reactor coolant pumps to meet system requirements during an electricalloss of power condition.

The motor bearing support system includes a Kingsbury douule acting thrust bearing with eight tilting pad shoes above the thrust runner and eight shoes below. Two ten horsepower oil lift pumps are used to lift the rotating assembly during startup and shutdown of the pumps.

Radial shaft support is supplied by upper and lower guide bearings, each with six shoes located at the top and bottom of the motor rotor.

FAILURE SCENARIO INVESTIGATION A detailed investigation was performed by a team led by station technical engineering which included personnel from station technical, project engineering, nuclear engineering design, maintenance, maintenance engineering and nuclear oversight. Three possible root causes emerged from this investigation: motor / pump misalignment, bent motor / pump shaft, and cracked motor / pump shaft.

EVENT #1 (December 7,1993)

FACTS AND EVIDENCE:

Prior to pump shutdown, small amounts of water were seen leaking past the vapor stage of the pump seal assembly. Inspection of the seal components showed that rubbing had occurred on the inside diameter of secondary shaft sleeve in the vapor stage. The thrust ring e

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r RCE 94-002 Reactor coolant Pump SealDamage, SONGS 3 February 28,1994 cover assembly carbon insert had wear over its entire inside surface and the metal sleeve was wom approximately.050 inch at the 5:00 O' clock position. The thrust ring cover and thrust sleeve showed signs of frictional heating, estimated to between 500 and 1000 degrees Fahrenheit at the point of maximum wear. The "O" ring sealing the secondary sleeve to the gland assembly of the vapor stage was heat damaged and incapable of providing an adequate seat between the seal vapor space and atmosphere.

Measurements of the motor shaft centerline to seal adapter runout.were taken. Maximum measured runout was.045 inch TIR. The thrust ring cover outside diameter was approximately.030 inch below drawing specification. This inadequacy allowed the cover to move within the seal housing and have an additional possible eccentricity of.015 inch with the pump centerline. The total float of the shaft within the lower bearing was measured as

.024 inch.

Vibration data taken during the two days leading up to the shutdown on December 7,1993 are shown below:

Date:

Time Overall 2X 1X December 5 00:00 12.0 3.7 9.5 08:00 12.3 2.7 9.9 16:00 December 6 00.00 10.5 2.3 7.0 08.00 10.5 2.5 6.7 16:00 10.2 2.2 6.4 December 7 00:00 12.6 2.9 8.2 08:00 18.1 3.1 9.3 All values are maximum peak to peak amplitude measured in mils. A more detailed listing of vibration data can be found in Appendix D.

j Controlled Bleedoff (CBO) flow was slightly low during pressurization on December 4 at.1 l

gpm and a temperature of 180 degrees F. On December 4 the CBO temperature reached 130.5 degrees F compared to 115 degrees for the other pumps. On December 5, CBO flow dipped to.8 gpm but later recovered to 1.2 to 1.4 gpm.

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EVENT #2 (December 12, 1993) l FACTS AND EVIDENCE:

Prior to the December 12 run, the float in the lower bearings was measured as.024 inch (MO93120582) the motor was moved.020 toward the calculated centerline of the pump when it contacted the register of the pump and could not be moved further. This left the motor approximately.013 eccentric to the pump centerline. Measurements taken after the 7

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RCE 94-002 Reactor coolant Pump SealDamage, SONGS 3 Fetwuary 28,1994 i

event show that the lower bearing was offset approximately.037 inch. With the shaft moving within the clearances allowed by the lower bearing, approximately.008 inch of interference was possible between the rotating thrust sleeve and the carbon insert in the thrust sleeve cover. (see appendix G, Figure 2, tolerance study)

Vibration data taken during pump startup show that the shaft orbital plot was chaotic. The overall vibration level was 12 mills with 1X vibration at 8.4 mills at the time that the chaotic orbit was measured. Prior to shutdown the vibration levels reached 30 mils.

Measurements of the thrust ring cover show approximately.050 inch wear in the carbon bushing consistent with the direction of the misalignment. Color pattems indicate heating of the ring to between 500 and 1000 degrees F.

Disassembly of the lower motor bearing housing revealed that the pad at the 5:00 position had a loose screw with the locknut free spinning. The motor shaft could not be centered, the shaft was hard against the shoes at the 1 and 3 O' clock positions when pushed toward the center of the "B" register (B register is the theoretical centerline of the motor at the lower motor radial bearing). The bearing housing support bolting was found loose with one bolt missing (MO 93121067). This looseness, if combined with compression of the insulating material, could have allowed movement of the lower radial bearing with respect to the motor centerline, but no definitive measurements of either the clearances or the insulating material thicknesses were taken. The nominal axial clearance in the joint is.000/.001 inch.

ROOT CAUSE IDENTIFICATION SCENARIO #1 - COMBINATION OF LOOSE BEARING SHOE, THRUST COVER DIMENSION, MISALIGNMENT AND SHUTDOWN TRANSIENT - MOST LIKELY EVENT December 7,1993 Event Prior to the December 7,1993 event the thrust ring cover outside diameter was undersized which allowed the cover to be installed up to.030 inch eccentric to the centerline of the pump.

This eccentricity along with excessive clearance in the lower motor bearing and misalignment between motor and pump allowed contact between the thrust ring and the carbon insert in the thrust ring cover. After the carbon bushing was wom away, there was contact between the metal ring on the cover and the thrust ring. The contact occurred on one side of the shaft which had the dynamic high spot.

1 Cover ring wear as described above also allowed contact between the primary and secondary seal sleeves of the vapor stage which caused heating of the gland O-ring which resulted in the water / steam leakage.

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RCE 94-002 Reactor coolant Pump Seal Damage, SONGS 3 February 28,1994 Visual inspection of the lower radial bearing indicated that the bearing shoe adjusting screw lock nut at the 5:00 o' clock position was loose prior to the event. A transient during pump shutdown may have caused the shoe to back out increasing the clearances in the bearing.

The lower radial bearing support plate on them motor was also found to be loose on later inspection. The assumed transient may have moved the entire support plate which would result in additional radial bearing eccentricity.

i December 12,1993 Event The swing check method used to determine the lower radial bearing clearances prior to the December 12 event used jacking screws to move the shaft against the bearing shoes. The location of the screws were such that the shaft did not contact the 5:00 o' clock shoe which had moved during the first event and the clearances were underestimated. The increased clearances, above those of the first event, more than made up for the motor movement and resulted in higher vibration amplitudes.

Another possible scenario is that the loose lower radial bearing support plate moved at the end of the December 7 event or at the beginning of the December 12 run and the additional eccentricity resulted in higher vibration amplitudes The vibration levels were sufficient to allow the thrust ring to contact the carbon bushing in the thrust ring. When the carbon had wom to the point where metal to metal contact was possible, a hot spot resulted and flashing of the carbon dust occurred. The pump was stopped when the carbon flashing and high (off scale) vibration was noted.

Refuting Evidence: None t

SCENARIO #2 - MOTORIPUMP MISALIGNMENT - LESS LIKELY EVENT December 7,1993 Event Prior to the December 7,1993 event the thrust ring cover outside diameter was undersized which allowed the cover to be installed up to.030 inch eccentric to the centerline of the pump.

This eccentricity, when combined with the lower motor bearing being misaligned and oversized, allowed contact between the thrust ring and the carbon insert in the thrust ring-cover. After the carbon bushing was wom away, there was contact between the metal ring on the cover and the thrust ring. The contact occurred on one side of the shaft which had the dynamic high spot. The metal to metal contact caused heat to be generated which heated an area of the shaft and resulted in shaft bowing.

The eccentricity of the thrust ring cover allowed contact between the primary and secondary seal sleeves of the vapor stage. The heat generated by this contact overheated the gland o-ring which resulted in the water / steam leakage (under normal conditions the thrust ring 1

cover would protect the seal from contact). The abnormally high vibration levels recorded on 9

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RCE 94-002 Reactor coolant Pump SealDamage, SONGS 3 February 28,1994 December 5,1993 at 16:00, along with reduction of CBO flow to.8 gpm, suggest that seal l

contact occured at this time. The quenching action of the CBO water leaking past the seal is l

hypothesized to have cooled the shaft, reducing the thermal bowing. At this time, seal contact was eliminated and both CBO flow and vibration levels retumed to normal.

December 12,1993 Event Prior to the December 12 event the motor was moved to try to align the motor shaft to the pump centerline. No attempt was made to reduce the clearances in the lower radial bearing or to center the bearing in the motor housing.

This event was similar to the first event in that the first contact was probably between the thrust ring and the carbon insert. After the carbon insert was worn away, there was metal to metal contact between the thrust ring and the thrust ring cover and a " hot spot" occurred. The glow from the hot spot was seen by personnel in the area and the pump was stopped. There was no contact between the primary and secondary seal sleeves since the thrust ring cover was in tolerance and provided clearance for the seal.

REFUTING EVIDENCE The high vibration levels measured during the December 12 event indicate that this event was much more severe than previous thrust cover rub events.

SCENARIO #3 - BENT PUMP SHAFT - LESS LIKELY A bend in the pump shaft could have occurred due to uneven heating of the shaft during the first event. A hot spot on one side of the shaft, due to a bow or dogleg, would cause the hot side of the shaft to expand relative to the cold side. This expansion would cause the shaft to bow in a direction opposite the heated side. The bowing would cause even greater interference and heat generation. This is termed thermal bowing.

When a shaft has thermal bowing there is a point where the cold side of the shaft exerts enough of a restoring force against the bow that the hot side exceeds its yield strength in compression. (This can happen at temperatures as low as 350 degrees differential between the hot and cold sides). When the shaft cools down to room temperature, there is a residual stress on the previous hot side and the shaft will have a permanent set in that direction.

REFUTING EVIDENCE r

Measurements of shaft straightness were taken after the December 12 event and the shaft straightness was found to be within manufacturers specification.

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RCE 94-002 Reactor coolant Pump Seal Damage, SONGS 3 Fetwuary 28,1994 l

SCENARIO #4 - CRACKED SHAFT - LESS LIKELY A crack in the pump shaft would be indicated by high vibration levels at 1X and 2X and may j

result in high vibration at 1/2 critical speed on coastdown. The loss of shaft stiffness could j

also result in increased bowing which would be consistent with the rubbing experienced during both runs.- A cracked shaft is actually a symptom of another root cause such as excessive vibrational stresses due to misalignment or imbalance.

REFUTING EVIDENCE Since a cracked shaft is a symptom and not an actual root cause, there would have to have been a history of high vibration over an appreciable length of time prior to initiation of a crack.

l Time would also be required for the crack to progress to the point where the flexibility of the shaft was changed. Once the crack had progressed to a point where the system response was changed a change in the vibration levels would be expected.

The 1X vibration levels measured prior to the December 7 shutdown are fairly small when compared to the 2X and overall vibration levels. This is not consistent with the expected response to a crack in the shaft. Appendix A report by B&W Nuclear Technologies provides additional analysis to refute this scenario.

CORRECTIVE ACTIONS TO PREVENT RECURRENCE

- i Unit 3 Corrective actions taken include the rebuild effort on pump 3P002 and inspections of reactor coolant pumps 3P001, P003 and 3P004. MO93121339 checked the 3P001 lower radial bearing and the bolting for the bearing housing support and found all bolting tight and acceptable. MO93121305 inspected the 3P003 lower bearings and found all bolts loose and 2 bolts missing. The missing bolts were replaced and all bolts were tightened to manufacturers specification of 165 ft lbs. 3P004 was checked per MO93121342 and the bearings and bolting were found to be acceptable.

i Unit 2 Continuous vibration monitoring will be used to detect changes in a RCP bearing support system that could be detrimental the seal. Indications that will be monitored are shaft centerline position, displacements and phase angles. The shaft centerline position will be an effective tool that will indicate a change in the bearing support system. A change in vibration displacement could be indicative of a change in the shaft bearing support system but will most j

likely be an indicator only after shaft rubbing has begun to occur. A change in phase angle would indicate a change in the shaft "high spot" position (relative to the keyphasor) that might i

be caused by a rub.

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__m RCE 94-002 Reactor cooknt Pump Seal Damage, SONGS 3 February 28,1994 Inspections of the Unit 2 pumps have been planned and will be implemented at the next available outage of sufficient duration.

A RCTS item will be issued requesting the following actions:

1) Assess the need for periodic inspections and overhaul of the RCP motor bearings and bearing support structure assemblies. (STEC)

2) Assess the need for pump motor alignments after specific maintenance activities. (STEC)

3) Implement periodic maintenance changes as a result of 1 and 2. (Station Maintenance)

4) Review the need for motor bearing inspections on similar pumps. (Station Maintenance)

5) Implement improved RCP thrust ring cover verifications. (Station Maintenance)

IDENTIFICATION OF OTHER SUSCEPTIBLE ITEMS The reactor coolant pumps on both Units are susceptible to similar misalignments. All pumps on Unit 3 have been checked and inspections of the unit 2 pumps are being planned per MO's 94020196, 94020197, 94020199 and 94020200.

10CFR21 EVALUATION The root cause of the failure of 3P002 was misalignment. This cause is related to either assembly or maintenance activities and is not a design deficiency. The pump vendor was informed of the problem and participated in the investigation at SONGS. No 10CFR21 report is necessary.

OPERATING EXPERIENCE WITH SIMILAR EVENTS There have been several reactor coolant pump failures due to shaft cracking or impeller damage reported, however, there are no known failures due to motor / pump misalignment that have been reported. The following is a listing of failures of events having RCP shaft / impeller damage:

1974 Surry RCP shaft sheared 12

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9 RCE 94-002 Reactor coolant Pump Seal Damage, SONGS 3 February 28,1994 1981 Prairie Island RCP shaft cracked 1984 Palisades RCP impeller bolt failure resulted in separation of impeller from shaft 1984 Three Mile Island RCP shaft crack and impeller vane cavitation damage 1985 Goesgen RCP shaft sheared due to fatigue failure 1986 Crystal River RCP shaft sheared 1986 Davis Besse RCP shaft cracked 1989 Crystal River RCP shaft cracked 1992 ST Lucie RCP shaft cracked l

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1 RCE 94402 Reactor coolant Putnp Seal Damage, SONGS 3 W 28 I

• b APPENDIX A B&W NUCLEAR REPORT b

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ES BGWNUCLEAR E3WSERVICE COMPANY To BWNS-20553B-5(10/89)

J.D. Agar - Project Manager, SCE Customer From r File ~

H.L. Hassenpflug - Component Engineering Date Subj.

1 February 1994 SONGS, Unit 3,12-93 RCP Failure Evaluation Details of the root cause analysis and dynamic analysis are attached on the following pages. The purpose and results are summarized below:

3e following document is an evaluation of data regarding reactor coolant

Purpose:

pump 3P002 at San Onofre, Unit 3, and the events of the first weeks of December 199 Its purpose is twofold:

The first objective is to explain in detail and permanently document the initial assessment of the pump's integrity / operability made at the time of the events.

The second objective is to present and discuss the most likely sequence of events and to j

4 present analytical evidence to support that scenario.

Summary of Results:

I The likelihood of permanent damage to the pump either causing or resulting from

, i 1.

the December events is very low. It is therefore prudent for SCE to operate the pump without a major overhaul of the pump or motor.

The most likely scenario involves several factors and is described in Section 3.

2.

Dynamic analysis supporting the root cause is also presented in Section 3, and detailed in the appendices.

NOTE: Per the terms of the Purchase Order #8H123003, no independent review of the i

calculations supporting this document was performed.

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Doc. No. 12-1229402-00 Table of Contents 3

Introduction 4

1.

Record of Events j

Evaluation of the Likelihood of Permanent Shaft Damage 7 2.

9 3.

Most Likely Scenario 9

A.

Approach B.

Basis 13 C.

Results 1

22 4.

References 5.

Appendices 23 Appendix A -- Dynamic Analysis 23 A1.

Methodology 27 A2.

Documented Sample Files Appendix B -- Modeling of Failed Lower Motor Bearing 39 40 Appendix C -- Data files 40 CRTSP2 input file, SONGSRCP. CSP 42 COTRAN interface model file, PREOUTGE. MOD 44 EVENT 1A. MOD 46 EVENT 1B. MOD 48 EVENT 2. MOD 50 COTRAN load file, NORMAL. LOD 28 January 1994.

Prepared by: H.L. Hassenpflug 2

Doc. No. 12-1229402-00 y

Introduction The following document discusses the events surrounding the December 1993 operational problems associated with the San Onofre-3 RCP, 3P002.

The evaluation is divided into three major sections.

the December events are recapped to provide a In Section 1, basis for.the rationale used in the other sections.

In Section 2, the concern of the likelihood of permanent daaage is discussed.

This concern is addressed separacely from the most likely scenario because of its impact on continued operability of the plant.

In Section 3,

an analysis of the events, including key assumptions, etc.

are presented.

The results of dynamic The modeling based on the assumptions are also presented.

details of the dynamic modeling are presented in the appendices.

In Appendix A, the general methodology for the analysis is discussed.

This includes sample data files, documented in detail, to allow the user to verify assumptions.

In Appendix B, the basis for modeling of the lower guide bearing, under the pre-outage conditions and under the abnormal, as-found conditions is presented.

In Appendix C, the actual data files for the modeling are attached.

28 January 1994 Prepared by: H.L. Hassenpflug

.. - ~ _ _.

Doc. No. 12-1229402-00 p

f 1.

Record of Events Pre-outage Conditions Initially, (prior to the outage) the pump / motor appeared to run normally, with no rubbing at the seal adapter plate and no Vibration levels were in the apparent vibration problers. range of 6 mils (pk-pk) in one plane and in the other direction.

Planned Repairs / Inspections (Refueling Outage) the coupling train and seal was During the refueling outage, The motor removed for inspection of the hydrostatic bearing.re-aligned with was not removed from the driver mount nor respect to the driver mount.

However, the upper guide

bearing, the thrust bearing and the thrust runner were disassembled to facilitate the replacement of RTD's at the motor thrust bearing (top of motor).

The lower end of the motor was not disassembled.

r The coupling train runout was checked upon reassembly and found to be normal (approximately 0.004 inches).

Initial Startup/ Operation The initial startup was unusual in that the seal' temperature The 3P002 was shut off while was high and the flow rate low..

When it was re-heatup proceeded using its companion pump. approximately 6-8 started, it appeared to run normally for hours.

Event 1 After the 6-8 hours of operation, the vibration levels began to climb

rapidly, and within minutes exceeded the.

At that time, the manufacturers thirty-mil shutdown limit.

l pump was secured.

Inspections and repairs were initated.

I Post-Event 1 Inspections / Repairs Subsequent to the high vibration shutdown, inspections and the related findings were as follows:

28 January 1994 Prepared by: H.L. Hassenpflug 4

i

(

Doc. No. 12-1229402-00

[

y Visual inspection revealed that.the seal, adapter plate

~

a.

had rubbed, with the strongest indications of' rubbing opposite the discharge direction.

In addition measurements were taken when it was removed revealed that its O.D. register fit was substantially undersized.

The adapter plate is normally self-aligning. It was therefore thought that the adapter plate had been installed eccentrically, and that its rubbing (and. associated thermal shaf t bow) was the root cause of the first event.

was The seal adapter plate (and the rest of the seal)

~

removed and replaced and their alignments checked upon re-assembly.

The new seal adapter plate was known to have the proper clearance.

A swing check performed on the motor shaft showed that b.

0.025 the center of the motor shaft clearance was inches. displaced from the center of the' seal cavity or was otherwise suggesting that the motor had moved, pushed away from the discharge direction.

As a

corrective measure, the motor was moved approximately inches toward the discharge and away from.the rub L

0.010 site.

It could not be moved further because of the limits of the rabbet fit between the motor and driver mount.

Second Startup/ operation the second startup, the pump initially appeared to be At operating normally and was operated for approximately twenty minutes before any abnormalities were observed.

Event 2 an observer About twenty minutes after the startup of 3P002, in the reactor building noted that the adapter plate was once again rubbing extensively, and apparently generating heat.

At the same time, the vibrations were seen to be escalating rapidly.

The pump was promptly secured.

Post-Event 2 Inspections / Repairs Prepared by: H.L. Hassenpflug 28 January 1994 5

A "c-2-

9'o2-~

BWitMV%

v Subsequent to event 2, the coupling train and. seal components i

were once again removed and extensive inspecti'o~ns performed.

The seal plate was found to have been rubbed once again, with evidence of heating around its entire circumference, but with the most severe rubbing once again approximately opposite the discharge.

Also, the lower motor guide bearing was disassembled.

It i

wasfound that (1) the guide bearing was not concentric to the notor frame, and that (2) one pad of the six tilting pads which comprise the bearing was mispositioned (backed out).

j 2

Measurements and examinations of the pump shaft were also performed. These gave no indication ofpump shaft damage or other damage to the interior of the pump.

28 January 1994 Prepared by: H.L. Hassenpflug 6

o 12-2"o2-oo SWMM%%v l

Evaluation of the Likelihood of Permanent.Sha'ft'. Damage 2.

Permanent damage to the shaft is of primary importance'since a shaft with permanent damage has an increased probability of The following assessment shows that the recurrent failure.,

likelihood of permanent shaft damage is quite low:

I forms of permanent damage considered are permanent The two bending and shafty cracking.

Permanent bending has been eliminated as a root cause by I

A.

measurement.

Shaft cracking isd more subtle.

While nothing short cf B.

full physical inspection of the shaft can fully ensure the absence of shaft cracks, the evidence to-date gives very little indication of cracking.

b.1

First, the 2x-response prior to the outage was This evidence stable in both amplitude and phase.

is key in detecting transverse shaft cracks (like I

the Crystal River-3 failures).

b.2 Unlike transverse shaft

cracks, full.

l circumferential cracks do not generally exhibit the 2x-phase and amplitude changes which have become e

{

the classic symptom of shaft cracking.

They de, steady increase in 1x-response show a

however, This (and probably shaf t centerline displacement).

would generally develop over a period of weeks with a more-or-less uniform progression.

By comparison, 3P002 ran more-or-less steadily, then trended up very quickly.

Its centerline position and lx-vibration escelated in a matter of A key point, however is that the shaft minutes.

centerline returned to its pre-event position after indicating that the problem was the several hours, result of a thermal effect such as might result from a rub.

This did not occur in the St. Lucie

'92 failure in which the shaft was found to be severely cracked in a

nearly circumferential j

pattern.

28 January 1994 Prepared by: H.L. Hassenpflug 7

Doc. no. 12-1229402-00 BBW NUCLEAR BWSERVICE COMPANY b.3 Swing checks on the hydrostatic bearing. indicate that it has full travel.

This su'ggests that the shaft below the HSB is at least straight enough that the case wear ring does not interfere with the bearing swing check, Data suggesting other root causes is very strong.

Particularly, the finding of misaligned and failed b.4 lower motor bearing as-well as the evidence of rubbing at the seal adapter plate suggest other root causes. This data is presented in detail andexamined analytically in Section 3

of this report.

The only shaft crack

• in pumps of b.5 Historical data-(this design including the this or similar design integral heat exchanger, and the integrated impeller / hydrostatic bearing journal) was at Grand Gulf, a BWR plant.

The failure site was in the hollow portion of the shaft.

It would be highly thin-walled section unlikely that a crack in a would propagate as a full circunferential crack.

Therefore, it is reasonable to expect that if a i

crack of the type seen at Grand Gulf were present, it would be detectable by the usual 2x-amplitude and phase changes CONCLUSION In summary, the likelihood of shaft cracking is very low.

Inspections have shown that the shaft is not bent in the region which underwent contact.

• (of which the manufacturer is aware) 28 January 1994 Prepared by: H.L. Hassenpflug 8

l' B& W NUCLEAR Doc. No. 12 1229402-00 BWSERVICE COMPANY 3.

Most Likely Scenario A.

Approach This analysis considers and attempts to match operating data as well as inspections and measurements for four different instances:

1.

Pre-outage 2a.

prior to Event 1 (Event 1A) 2b.

Event 1 (Event 1B) 3.

Event 2 The scenario which fits the data well includes the following effects as critical parameters:

i misalignment of the lower guide bearing in the motor a) b)

changes in alignment of the motor-to-driver mount c) mispositioning (backing out) of one pad of the lower guide bearing d) mechanical contact and subsequent transient thermal l

bowing of the shaft NOTE: The combination of effects described in d) is commonly observed in rotating equipment in which the shaft is not immersed in liquid such as gas turbines, It is a less-common in pumps because most of the etc.

potential rub sites in pumps are internal to the pump and will not overheat even if rubbed.

e)

In addition, the concentricity of the adapter plate is not known during Event 1.

It is assumed that to be properly positioned prior to the outage and af ter Eventi.

j B.

Basis of Analysis The mechanical parameters identified above are discussed for i

f each of the four operating conditions as follows:

I 1.

Pre-outage lL Prepared by: H.L. Hassenpflug 28 January 1994 9

_____-_______________-____a

"c"-

'-2'"

2-o BWilWA%fakur While no measurements of the actual lower ~ guide bearing a) alignment were made prior to the outage, it is reasonable to assume that this did not change as a result of maintenance activities during the

outage, and is l

therefore thought to be the same as measured after Event 2.

That is, the lower guide bearing is assumed to i

be twenty-five to thirty mils displaced f_om the center of the motor frame (twenty-five used in the analysis),

displaced in a direction opposite the discharge.

The motor is assumed to be properly aligned to the driver b) mount prior to the outage (within one mil).

The bearing pads are assumed to be uniformly positioned c) at their proper clearances.

d)

There was no evidence of rubbing prior to the outage.

thermal bowing is not considered in the pre-Therefore, outage analysis.

2.

Event 1 a)

The alignment of the lower guide bearing to the motor frame is assumed to be the same as was measured subsequent to Event 2 (25 mils away from discharge).

However, the effective center of the bearing is additionally displaced from the center of the support because of the mispositioned pad.

The motor is assumed to be properly aligned to the driver b) mount.

c&d) After Event 2, one pad was found to have backed out due to a loose locknut.

The locknut is thought to have been loose prior to the outage.

The misplacement of the pad may have occured during the outage, (a time at which the bolt had no preload) and as a result of maintenance activities and associated vibrations.

It seems more likely however, that the pad was properly positioned at startup and that it vibrated loose during the period of normal operation prior to Event 1.

This would occur easily if the 1x vibration (as results from shaft bow, either permanent or temporary) were sufficient to exceed Prepared by: H.L. Hassenpflug 28 January 1994 10 l

l l

t B&WNIJCLEAR Doc. no. 12-1229402-00 BWSERVICE COMPANY that static load on the pad positioning screw. That is,

~

if the pad were alternately loaded and unloaded, it would be prone to loosening.

The details of the modeling of this failed bearing are detailed in Appendix B.

The thought here is that because of the mispositioned-adapter plate, a thermal bow was induced the vibrations from which caused the loosening of the pad. Operation of the pump with the loose pad caused severe rubbing, very high and very rapid thermal bowing of the shaft, thereby precipitating both events.

It is thought to have backed out approximately 0.020 inches.

Therefore, two conditions are considered for Event 1:

Event 1A) The inital condition, where conditions differ _from the pre-outage only in that the adapter plate is misaligned, and Event 1B) where the pad has backed out.

While the thermal bowing further compounds the vibrations seen in this scenario, that effect is not modeled.

It is also assumed that, in Event 1B, the carbon ring is moves away from the discharge direction, the presumption being that it moved in its clearance circle.

This mitigates the severity of the rub.

This may or may not have happened, but would provide a

(one of several possible) reasonable explanation as to why the rubbing damage was less severe during Event 1 than during Event 2.

3.

Event 2 a)

Adapter plate is properly aligned.

The adapter plate was replaced during maintenance activities subsequent to Event 1.

The replacement adapter plate was measured, and found to have the

't proper o.D.

Under these conditions the adapter plate is self aligning.

Prepared by: H.L. Hassenpflug 28 January 1994 11

.j Doc. No. 12-1229402-00.

g l

1 The lower guide bearing is still failed,,

b)

Problems with the lower motor bearing were not detected during the inspections subsequent to Event 1.

The bearing configuration is the same as in Event 1B.

The lower motor bearing is still misaligned to the motor c) frame.

Just as with the pad placement, the lack of lower bearing inspections meant that the alignment of bearing to motor frame was the same for Event 2 as in Event 1.

The motor frame was moved ten mils toward discharge.

d) t the overall alignment of the lower motor bearing In Event 2, to the pump is actually improved. However,-because of the bearing-to-frame misalignment and failed lower motor bearing, the effective alignment is still far from correct.

No additional thermal bow is considered for the model, e) although it is known to have occurred before the securing of the pump.

28 January 1994 Prepared by: H.L. Hassenpflug 12

.m....

B&WNUCLEAR poc. no. 12-12294o2.oo BWSERVICE COMPANY C.

Results The calculated orbits at the adapter plate is shown for the four cases described in Section 3B. Also vector plots (or interference diagrams) are shown for each of those cases.

NOTE The vector plots show the reaction forces due to contact as vectors, superimposed on the orbital diagram.

The orbits are shown as dotted lines.

The heads of the vectors are not shown to avoid cluttering the plots.

The direction is easily determined from context, since the load vectors are always shown as originating on the orbit.

The vector plots may also be viewed as a plot of contact interference.

This is accomplished by simply dividing the contact force by contact stiffness ( 50000 lb/ inch assumed).

The results for the pre-outage conditions are given in Figures 1 and 2.

The results for the period prior to Event 1 are given in Figures 3 and 4, for Event 1 (not including increased runout due to thermal bowing) in Figures 5 and 6,

and for Event 2 in Figures 7 and 8.

Observations:

o In spite of the substantial (25-mil) misalignment of the lower 1.

bearing prior to the

outage, there is virtually no interference occurs at the adapter plate.

From the EventlA simulation, rubbing could be initiated by the 2.

adapter plate misalignment (given the misaligned lower guide bearing).

This would be sufficient to start thermal bowing and to allow the wayward bearing pad to back out.

From the Event 1B simulation, failure of the lower guide 3.

bearing would also cause rubbing, even with a properly aligned adapter plate.

From the Event 2 simulation, the re-alignment of the motor' 4.

after Eventi should have mitigated the severity of Event 2.

However, with a failed lower motor bearing, and the motor misalignment, the adapter plate rubbed anyway.

, Prepared by: H.L. Hassenpflug 28 January 1994 13-

9 hh R I M ANY N.

12-1229402-00 The fact that rubbing damage was less severe.a.f_ter the first event than the second is possibly explained by slippage of the adapter plate in its (excessive) clearance during Event 1.

(This slippage is considered in the Event 1B dynamic model.)

It may also be that the malfunction was simply detected sooner during Event 1 than in Event 2.

FIGURE 1 CALCULATED ORBITAL PLOT (PRE-OUTAGE) oo SONGS ftCP #1a LC8 N S/LIGNED O.025 #4 K=Normd (PREOUTGE. MOD)

LC@ F"lLE P4CLUDES: (.004) CPLG RUNOUT +4BK RADAL+5X+ 5LB UNS.

J RUN f 2363 2"oo. _

1 7 Cn Q

l o

>- 9 c-0I Z

~

-1 oo Z.4 -

ON l

CD I

E

<C o l

I O9 f

N 3

i

-t 16.OO

-8.00

.00 8.00 16.00 n

CARBON RING X-DSP (MILS)

Prepared by: H.L. Hassenpflug 28 January 1994 14 l

Doc. No. 12-1229402-00 FIGURE 2 CALCULATED VECTOR PLOT (PRE-OUTAGE)

NOTE: NO INTERFERENCE PRESENT LtJ Oo Z 9 SONGS RCP #4.: LC8 MI5XJGNED O.025 N., K= Normal (PREOlJIGE. MOD) g INTERFERENCE SHOWN 5X ACTWL 1

RUN f 2368 LLI Lt_ o EQ_

Ltj O l-I Z

No r"

'N

\\

0o (f) to -

.t,

_ ~

C3 i

l p

o U

q' -

ZN 1

T Zo CD 9 1N i

o -t16.00

-8.00

.00 8.00 16.00 CRBN RING X-DISP / INTERFERENCE Prepared by: H.L. Hassenpflug 28 January 1994 15

N Doc. No. 12-1229402-00 CALCULATED ORBITAL PLOT (ZVENT 1A)

FIGURE 3-P OO SONGS RCP M44 LC6 MS.oLIGNED 0.025 N K=Normd (EVEt#1AMO LOAD FILE HCLUDES: (.004) CPLG RUNOUT +4.8K RAD %L+5X+ SLB RUN f 2369

~2"oQ_

1I w

Q l

o

>9 a> -

Z_.

.__1 Oo Z,4 -

ON I

CD O'

4O O9 i

N I

~

(i6.00

-8.00

.00 8.00 16.00 CARBON RING X-DSP (MILS)

L 28 January 1994 Prepared by: H.L. Hassenpflug 16

4 B& W NUCLEAR Doc. No. 12-1229402-00 1

BWSERVICE COMPANY FIGURE 4 CALCULATED VECTOR PLOT (EVENT 1A)

. ~

i I

Oo Z 9 SONGS RCP #1.: LW M!stlGNED 0.025 N K=Normd (ENDR1AMOD)

W INTERFERENCE SHOWN 5X AClV4.

1 RUN f 2369 LLJ Lt_ o ZQ_

LtJ O l-I Z

\\g

,. a-N.

CL 9 (f) e> -

CD I

8

\\

\\

O 4-1 ZN I

-T Zo 00 1N o -t16.00

-8.00

.00 8.00 16.00 j

CRBN RING X-DlSP/ INTERFERENCE Prepared by: H.L. Hassenpflug 28 January 1994 17 i

]

/

Doc. No. 12-1229402-00 y

FIGURE 5 CALCULATED ORBITAL PLOT (EVENT 1B) s O

SONGS RCP #4ALYSG: FALED/ MISALIGNED LGB.(LVDfT18. MOD)

LOAD FLE NCLUDES: (.004) CPLG RUNOUT +4.8K RADW.+5X+ SLS UNS.

RUN f 2370 2o V

O. _

cn Q

l o

>ow-Z

_E oo Z4-ON 0D I

Z<[

o O9 N-3 i

$16.00

-8.00

.00 8.00 16.00 CARBON RING X-DSP (MILS) 28 January 1994 Prepared by: H.L. Hassenpflug 18

N 12-1229402-00

. bWf AVbb M ANY j

1 FIGURE 6 CALCULATED VECTOR PLOT (EVENT 1B)

NOTE:

THIS CALCULATION DOES NOT ASSUME ANY ADDITIONAL INTERFERENCE DUE TO THERMAL BOWING LL)

Oo Z 9 SONGS RCP #4ALY5tS: FALED/ MIS /4JGNED LGS.(EVENT 19. MOD) g INTERTERENCE SHOWN SX ACTUAL 1

RUN f 2370 Ltj LL o 19_

bJ W H-I Z

-.No CL 9 (f) e> -

O I

l

.._/

\\

>o o

O.4 -

i A

ZN b

L., g M\\\\\\$$

Zo CD I

EN o 116.00

-8.00

.00 8.00 16.00 CRBN RING X-DISP / INTERFERENCE Prepared by: H.L. Hassenpflug 28 January 1994 19

I o

12-122 " o2-S WifAW% % v FIGURE 7..

CALCULATED ORBITAL PLOT (EVENT 2)

OO SONGS RCP ##4.YSIS: FAILED /MSALONED LGB (EVEfF2. MOD)

LOAD FLE NCLUDES: (.004) CPLG RUNOUT +4.SK RADW +5X+ 5LB UNS.

J_

RUN f 2366 2o u

o. -

0- T m

C3 l

oo

<o -

OI Z

1 oO Z,4 -

ON Q]

l 1<C o O9 N i

i

-t 16.00

-8.00

.00 8.00 16.00 ro CARBON RING X-DSP (MILS) l Prepared by: H.L. Hassenpflug 28 January 1994 l

BBW NUCLEAR D ** "**~

94

~*

BWSERVICE COMPANY FIGURE 8 CALCULATED VECTOR PLOT (EVENT 2)

NOTE:

THIS CALCULATION DOES NOT ASSUME ANY ADDITIONAL INTERFERENCE DUE TO THERMAL BOWING LLJ Oo Z 9 SCRJGS RCP #4/4Y515: FAILED /M'fAJGt4ED LGS (EVENT 2. MOD)

Ltj mgrcaner shaws 5x ecut g

g to Lt o 1Q_

LLJ O l-I Z_

No e'

CL o r'

(f) d-O I

b I

\\ggf"%e#

ZN I

Zo CD 9 i

m pj i

O 116.00

-8.00

.00 8.00 16.00 CRBN RING X-DISP / INTERFERENCE 28 January 1994 Prepared by: H.L. Hassenpflug 21

4 Doc. No. 12-1229402-00 yy 4.

References 1.

Li, D.F.,

E.J.

Gunter, and P.E.

Allaire,

' Undamped Critical speed analysis of Dual-Level Rotor Systems',

University of Virginia Report No. UVA/634092/MAE81/126, Dacember 1981.

2.

Nicholas, J.C., E.J. Gunter, and P.E. Allaire, ' Tilt Pad The Five Pad Bearing',

Characteristics Bearing University of Virginia Report No. UVA/643092/MAE81/135, February 1978.

' Transient Analysis Hassenpflug, H.L., and L.E. Barrett, 3.

of Coupled Rotor-Structure Systems', University of June 1988.

Virginia Report No. UVA/643092/MAE88/378, 4.

H.L. Hassenpflug, BWNT Doc. No. 32-1201091-01,' COTRAN QA

- vs 2.3',

12-91.

G l

28 January 1994 Prepared by: H.L. Hassenpflug 22

I B&WNUCLEAR coc. No. 12-1229402-00 BWSERVICE COMPANY Appendix A -- Dynamic Analysis A1.

Modeling Methodology The modeling of the RC Pump is done using a time integration Unlike more traditional linear analysis methods, this method.

approach directly addresses abnormalties such as misalignment and rubbing.

Its primary disadvantage is that it is computationally intensive compared to the more common methods.

The advent of very fast personal computers has made this approach much more practical-than it was even when the software was written (mid 1980's).

This analysis is performed using COTRAN/COGRAF as the primary integration code.

Two other codes, CRTSP2 and PADFEMPRO are used in generating inputs for COTRAN.

A flowchart for the analysis using COTRAN is presented on the following page.

COTRAN allows that interfaces between major structural components such as bearings or rub sites may exhibit non-linear behavior.

It assumes, however, that the structures themselves, such as the pump / motor rotating assembly, will themselves respond as linear elastic structures.

It is also possible to directly model shaft cracking with a NOTE:

time integration

method, but this technology has not been implemented with COTRAN at this time.

l l

i Prepared by: H.L. Hassenpflug 28 January 1994 23 I

J PSIEDBBWNUCLEAR poo, no. 12 122gao2-oo IDWSERVICE COMPANY l

f l

5 Figure Al Flow Chart for the Dynamic Modeling using COTRAN bearing geometry SONGSRCP. CSP model j

---

shaf t structural model (w/o supports) 1 PADFEMPRO (2)

CRTSP2 (1)

~'

(modal solver) i tilt pad brg. coefficients 1

1 MODEL LOAD 2

TAPE 97 l

other

- interf ace elements unsupported

- ------------ external loads, shaft modes time step, etc.

COTRAN [3,4)

TAPE 77 (time integration (run serial no.)

code)

---

control file Bearing and interface --

for COGRAF load time histories Displacement tiJne histories TAPE 14 i

TAPE 11 TAPE 17 I

i COGRAF (graphics) plots i

28 January 1994 Prepared by: H.L. Hassenpflug 24

i I

B&W NUCLEAR po"' ya' 12-1229ao2_oo BWSERVICE COMPANY W

Description of Input Data for COTRAN Figure A2 X

X ------ Bearing (model file)

---

Unsupported shaft: weights and stiffnesses (tape 97) li Gyroscopic terms (model file) i Unbalance (load file)

L_l Rub (model file) l X

X ----- Misaligned bearing (model file) 28 January 1994 Prepared by: H.L. Hassenpflug 25 i

T Doc. No. 12-1229402-00 g

l 3P002 Sample Input files A2.

This section provides detailed description of various components of the pump-motor model used to represent 3P002 and the events which it underwent.

The assumptions and rationale were explained in This section provides Section 3 of the main body of the document.

sample files typical of the' inputs to CRTSP2 and COTRAN with extensive documentation added to explain to the reader the information used in the models. The actual files for the four model cases are are provided in Appendix C.

three key aspects of the model are the shaft model, the For each of these aspects, The a

interface model, and the load model.

(in italics) for sample file is provided with documentation added reader edification.

A2.1 Shaft Model on the following pages, the model of the shaft used for analytical modeling is described.

The model described is input to CRTSP2 which calculates its unsupported mode shapes and natural The modal description of the shaft is subsequently frequencies.

used as input to COTRAN.

Dimensional Approximation l

The model was developed at site during December 1993.

Dimensions and weights in this model are approximate and are Since in some cases based on components of similar design.

the-objective of the model is to achieve an understanding of the December events and trends which might be observed in the i

and not to perform any sort of I

operation of the equipment, design modification to the pump, these approximations are reasonable. Therefore, there is little value added in further and the model is presented without refinement of the model, modification.

1 28 January 1994 Prepared by: H.L.-Hassenpflug 26

o 2-12 2"o -oo S W # n W afa b y CRTSP2 Input file for Unsupported Shaft (titling information)

Allis-Chalmers RCP Pump Motor Shaft Model for CRTSP2 (free-free modes)

Prepared by H. L. Hassenpflug from A-C Drawings 12-20-93 (control entries) (see CRTSP2 manual for details) 50 3

1 50 1

3 2

2 0

1 1

08

-1

-3 1

.9

-1 1

0 0

(bearing stiffness entries)

... for rotor 1 (pump-motor shaft)

These values are infinitesimal compared the size of the rotor.

This allows the approximate calculation of unsupported modes.

NOTE:

1.2 E3 0

50.2 E3 0

for dummy rotor (not used)

The dummy rotor is rigidly attached to ground and is itself very rigid so of the range of interest.

NOTE:any modes associated with it will be out that

.l 1 5.000E+07 0

i 3 5.000E+07 0

\\

(shaft section data) w-ext length od id ipolar itrans ymod dens 0.000 15.000 10.250 7.875 0.000 0.000 30.000 0.283 4070.000 11.062 10.250 7.875 251823.9 176760.1 30.000 0.283 impeller....

.... hydrostatic bearing....

312.370 7.250 10.250 0.000 30080.91 16633.6 30.000 0.283 311.523 4.375 7.748 0.000 32015.91 17696.7 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283

.... coupling spool....

450.000 12.250 10.750 8.750 0.000 0.000 30.000 0.283 0 000 12.250 10.750 8.750 0.000 0.000 30.000 0.283

)

28 Jama2 y lW Prepared by: H.L.

Hassenpflug 27

B&W NUCLEAR poo no. 12 122gao2.oo BWSERLilCE COMPANY 0.000 12.500 10.750 8.750 0.000 0.000 30.000-0.283 450.000 12.500 10.750 8.750 0.000 0.000

~30.000 0.283 0.000 11.000 9.500 0.000 0.000 0.000 30.000 0.283 0.000 4.333 9.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 3.112 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283

.... lower guide bearing....

0 1.463 9.5 0

0 0

30.

0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.200 14.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.300 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 1435.000 6.600 22.468 0.000 6.05E+05 3.11E+05 30.000 0.215 1435.000 2.902 22.468 0.000 6.05E+05 3.11E+05 30.000 0.215 0.000 4.698 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 1617.330 5.000 22.468 0.000 7.58E+05 3.70E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 34 11E+05 30.000 0.215 1336,667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 '3.11E+05 30.000 0.215 1617.330 4.775 22.468 0.000 7.58E+05 3.70E+05 30.000 0.215 0.000 4.934 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 0.000 4.934 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 3895.000 4.934 22.468 0.000 2.13E+06 1.18E+06 30.000 0.215 3895.000 3.722 22.468 0.000 2.13E+06 1.18E+06

'30.000 0.215 0.000 6.146 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.934 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.800 11.772 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283

.... upper guide bearing....

0 3.858 11.5 0

0 00 30.000 0.283

?

0.000 0.675 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 1520.000 5.200 11.500 0.000 1.17E+05 2.53E+05 30.000 0.283 thrust runner....

0.000 5.450 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.450 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.200 9.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.320 8.304 0.000 0.00B+00 0.00E+00 30.000 0.283 696.000 8.304 0.000 4.01E+04 2.81E+04 30.000 0.283

.... backstop....

0.000 10.942 7.900 0.000 0.000 0.000 30.000 0.283 1

100.000 3.808 7.900 0.000 0.0 0.000 30.000 0.283 0.000 4.130 7.900 0.000 0.000 0.000 30.000 0.283

\\

speeds used for modal analysis) Gyroscopic effects are not included in the (shaft NOTE:

Therefare, all shait speeds are set to zero.

0.

O.

1 28 January 1994 Prepared by: H.L. Hassenpflug 28

2 12294a2.ao B&WNUCLEAR poc' no* '

BWSERVICE COMPANY O.

O.

considered in searching for~eigenvalues)

(range of frequencies (cpm) 01.000 5000.

25.

e 28 January 1994 Prepared by: H.L. Hassenpflug 29

_ _ _ _ _ _ _ _ - - _ _. _ _ _ _ _ _ _ _ _ _ _ ~. _

Doc. No. 12-1229402-00 f

hg Interface model Key points to note -- The discharge direction is chosen to be The discharge load.

1.the positive Y-direction in the COTRAN model.

therefore acts in the negative Y-direction.

Misaligned bearings (or those for which the alignment is a-parameter) are treated as non-linear stif fness interface elements.

Mechanical contact is also treated as a non-linear element.

i i

'~

Typical COTRAN 'MODEL' file On the following page, a sample COTRAN 'MODEL' interface file is It is intended not presented with considerable annotation added.

but the COTRAN inputs only to describe the conditions simulated, and how they are used to accomplish the nodeling of those conditions. The data from the file itself is shown in bold, i

comments which describe the COTRAN requirements are shown in italics and description of the conditions related to 3P002 are shown in normal text.

A similarly annotated ' LOAD' input file is

'MODEL' file.

presented.immediately following the NOTE that these are simply sample files, and that the actual files are located in Appendix C.

'CPR',BJ/A-C SONGS RCP ANALYSIS: LGB DISPLACED 0.030 IN., Normal stiffness These entries are ior the input af connents.

The TAPE 10.

The CPR comments are also echoed to the COTRAN record file,'MODEL' file appears first 'CPR' entry in the (unless modified in postprocessing).

line in the graphical output

'CPR', Rotor only

'CPR',12-22-93

' RTR',9 7,0., ' (Crtsp2 model) '

' RTR' This identifies the file.from which the modal The.first parameter indicates, in this basis for rotors is read.

case, that the modal basis is to be read from ' TAPE 97'. The second 28 January 1994 Prepared by: H.L. Hassenpflug 30 t

92kEIIB&WNUCLEAR oce, no. 12 12294o2 oo IDMSERVICE COMPANY parameter is the percentage structural damping considered.for the The last entry is for the edification of' the user only.

structure.

The structure identified on the first 'RTR' entry will be treated as rotor 1

'COM'RTR',98,0.,' PUMP SHAFT (finite element model)'

'COM' The

'coM' entry simply allows a method for documentation cf the input file.

Data on a

'COM' card is not echoed, or even read into COTRAN.

'COM'

'BRG',1,43,0,1,0,' UPPER MOTOR BEARING'

'COM'XXX',.659E5,-5400.,8800.,.1412E6,1200.

'CXX',.1461E5,217.,-200.7,.1468ES,1200.

1 linear bearing data set entry marks the beginning of a set of bearing data t

The 'BRG'

'BRG' are irl,ist1,ir2,ist2 the first four entries following the where irl is' the rotor number of the first node being connected, isti is the station (or node) number of the first

\\

node, ir2 is the rotor number of the second node being and so on.

In this case, the non-rotating

\\

connected, components to which the shaf t is actually connected are not modeled as structures (i.e. treated as stationary and rigid).

In this case ir2 is 0,

and ist2 is arbitrary (may be any

}

j positive integer).

l The fif th entry on the 'BRG' line is a flag which indicates whether (for plotting, printing, etc.).

bearing forces are to be retained The final entry is descriptive and has no use except to prevent confusion.

The lines which follow the 'BRG' line are coefficient sets.

These are typical of linearized hearing models. The 'KXX' lines each allow the input of bearing stiffness coefficients coupling the nodes in the preceding 'BRG' entry.

Similarly, the 'CXX' lines The data on the 'KXX' allow the input of damping coefficients.

line is 'KXX',kxx,kxyrkyx,kyy, rpm where the kij are typical bearing stiffness coefficients, and rpm is the shaft speed (in RPM) for which the coefficient is 28 January 1994 Prepared by: H.L. Hassenpflug 31 i

B&W NUCLEAR Doc. No. 12-1229402-00 SWSERVICE COMPANY l

valid.

The CXX input is analogous.

When only _a single set of coefficients is input, rpm is ignored.

~

'NLB ',1,43,0,1,1,1,0, ' UPPER GDE BRG STIFFNESS, misignant allowed '

.659E5,.1412E6,0.,0.001,0.001,0.001,.000 The 'NLB' line signifies the beginning of a non-linear hearing or interface data set. The first four entries on the 'NLB' line are the same as for the 'BRG' entry, and specify connectivity.

The fifth entry defines whether the interface connects translational or of freedom (1

for translational, 2

for degrees rotational The sixth entry gives the non-linear element type.

rotational).

Type 1 is a flexibly supported annular gap element with friction, otherwise known as a rub element.

The sixth entry is the flag for and the last entry is descriptive data.

plot output, The line following the 'NLB' line will ha difforent for various non-linear element types.

For the rub element, the entries are kxx = contact stiffness in the x-direction) 1.

kyy = contact stiffness in the y-direction) 2.

3.

ds

= rotating component diameter

= stationary component diameter 4.

db

= coefficient of sliding friction on contact 5.

u.

6.

xm

= x-misalignment 7.

ym

= y-misalignment COTRAN only uses the difference between these instances where only the clearance is known it is Note 1:

diameters.

input as above, with ds=0 Note 2:

The misalignments are given as the x-and y-relative to the center coordinates of the UNDEFLECTED SHAFT, of the annulus of contact.

This convention can become confusing!

Note 3:

The rub element is used to model misalignment in normal bearings where the cross-coupling is not significant, as is the case with tilting pad bearings and hydrostatic bearings.

This is done by setting the clearance to an insignificant value and setting the coefficient of friction to zero. The rub element then replaces the 'KXX' line of the normal bearing model.

28 January 1994 hreparedby: H.L. Hassenpflug 32

. ~

Doc. No. 12-1229402-00 p

'COM'

'BRG',1,18,0,1,0,' NOMINAL LOWER MOTOR BEARING #-

+

'C;M'KXX',.3641E6,3740.,.1464ES,.1068E7,1200.

'CXX',.1150E5,194.5,4.7,.1565ES,1200.

'NLB',1,18,0,1,1,1,0,'LGB Stiffness (misalignment allowed)

O.,0.,0.,0,001,0.001,0.001,.030

'NLB',1,18,0,1,1,1,1,' LOWER GUIDE BRG CONTACT MODEL 1.00E6,1.00E6,0.,0.020,0.250,0,001,.030

'COM'

'BRG',1,1,0,1,0,' case wear ring stiffness and damping' NORMAL (PER B-J)

'KXX',.1257ES,.1559E5,.1705ES,.1541ES,1200.

'CXX',200.6,-26.4 -25.56,200.8,1200.

NORMAL (PER B-J)

'NLB',1,1,0,1,1,1,1,' CASE WEAR RING RUB 2.E7,2.E7,0.,.120,.35,0.,0.

'COM'

'NLB',1,3,0,1,1,1,1,'HSB RUB MODEL (bottom edge)'

.2.E6,2.E6,0.,.060,0.35,.0001,

.000

'NLB',1,3,0,1,1,1,0,'ESB MODEL (bottom edge)'

.250E6,.250E6,0.,.0001,0,00,.0001,.000

'NLD',1,4,0,1,1,1,0,'HSB STIFFNESS MODEL (TOP edge)'

.250E6,.250E6,0.,.0001,0.00,.0001,.000

'COM'

'NLB',1,12,0,1,1,1,1,' CARBON RING RUB MODEL' (MISALIGNED) 50000.,50000.,0.,.040,.25,.001,0.010

1. COM'

'BRG',1,4,0,1,0,' HYDROSTATIC PUMP BEARING (TOP)'

'KTT',3.E6,0.,0.,3.E6,1200.

'CXX',050.,0.,0.,050.,1200.

'COM'

'COM', MAGNETIC PULL MODEL

'COM'

'BRG',1,28,0,1,0,' MAGNETIC PULL MODEL'

'KXX',0.,0.,0.,-500000.,1200.

'COM',

GYROSCOPIC DECLARATIONS

'GYR ' lines....

lines include the polar noments of inertia of the shaft The 'GYF' These give rise to all gyroscopic effects seen in the elenents.

These effects may be included in the eigenvalue analysis by specifying a non-zero shaft speed in CRTSP2, but doing so restricts pump.

the subsequent COTRAN analysis to the shaft speed specified in the CRTSP2 analysis.

Most COTRAN models are vith the gyroscopic effects included in the interface model for generality.

Prepared by: H.L. Hassenpflug 28 January 1994 33

--,=_

" c

'- 2 " < o2-~

BWilFMtfaimr

\\

The data enties on the 'GYR' line are:

'GYR',ir,ist,ip where ir = rotor number ist = station number ip = (weight) polar moment of inertia lb-in*2 for the shaft element at the specified node

'GYR',1,2,252000.

'GYR',1,3,30080.

'GYR',1,4,32015.

'GYR',1,22,6.05e5

'GYR*,1,23,6.05e5

'GYR',1,25,7.58e5

'GYR',1,26,6.15e5

'GYR',1,27,6.15e5

'GYR',1,28,6.15e5

'GYR',1,29,6.15e5

'GYR',1,30,6.15e5

' GYR ',1,31,7. 5 8 e 5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1.17e5

'GYR',1,50,4.01e4 MST and SLV lines

'COM' MASTER AND SLAVE DOF DECLARATIONS

'MST', ir,ist,kor and

'SLV',

ir ist,kor r

l where ir = rotor number ist = station number _

2 for rotational dof kor = 1 for translational dof, These lines spacify the master and slave degrees of freedom. The dynamic response is calculated directly during integration at master dof's and indirectly at slaves. It is not calculated at all.

for other dof's.

Other entries, such as interface elements connected to a particular degree of freedom vill cause those l

degrees of freedom to automatically become slaves unless an 'MST' line is used to supercede that declaration.

28 January 1994 Prepared by: H.L. Hassenpflug 34 l

1

l I

S&W NUCLEAR ooc. no. 12-1229402-00 BW' SERVICECOMPANY r

As a matter of practice, the specific degrees of freedom selected as masters are not of critical importance.

Selbcting master degrees of freedom for which output is sought will improve computatione'

'iciency but will have little etfect otherwise.

i However, the k aER of master degrees of freedom will be the same as the number of modes used in the time integration solution and is quite important to the results.

As a matter of practice, enough modes should be used so that the highest frequency mode is at least five times operating speed.

For RC pumps, this typically requires masters were declared in this analysis.

five to ten modes.

Elf In short, it is importas...o declare an adequate number of masters.

Declaring them to be points where there are interface elements, etc. Will improve efficiency, but is otherwise unimportant.

The declaration of slave elements is done automatically by other parts of the software.

The declaration of slave elements is largely r

superfulous.

'MST',1,2,1

'MST',1,4,1

1. MST',1,9,1 i

'SLV',1,10,1

'MST',1,12,1 l

'MST',1,18,1

'MST',1,25,1 l

'MST',1,31,1

-l

'MST',1,43,1

'SLV',1,50,1

'SLV',1,12,2

'l In this case, eight masters are declared, and three slaves.

Note l

that the number of masters cannot exceed the number of modes i

available in the CRTSP2 input file.

'END' mandatory file terminator I

i i

Prepared by: H.L. Hassenpflug 28 January 1994 35

.=,

\\

j B&W NUCLEAR ooc, uo. 12 122g4o2.oo BWSERVICE COMPANY I

I Typical COTRAN ' LOAD' file

'COM', SONGS (A-C Motor) RCP TRANSIENT ANALYSIS the first 'CPR' line in the load file becomes the second title line in the graphical output

'CPR', LOAD FILE INCL: (.004) CPLG RUNOUT +4.8K RADIAL +5X+5LB UNB.

'CPR', WEAR RING RESPONSE

'PLX ' lines.....

~

request output of displacement time histories for postprocessing The parameters are iri ist,jx,!:or ir = rotor number ist = station (Dode) number jx = 1 for x displacement 2 for y displacement kor =1 for translational motion 2 for rotational motion

'PLX',1,1,1,1

'PLX',1,1,2,1

'CPR', HYDROSTATIC BEARING IOCATION (BOTTOM)

'PLX',1,3,1,1

'PLX',1,3,2,1

'CPR', HYDROSTATIC BEARING LOCATION (TOP)

'PLX',1,4,1,1

'PLX',1,4,2,1

'CPR', PROBE (PUMP) LOCATION

'PLX',1,9,1,1

'PLX',1,9,2,1

'CPR', LOWER GUIDE BEARING LOCATION

'PLX',1,18,1,1

'PLX',1,18,2,1

'COM' DUMMY VELOCITY OUTPUT

'PLV',1,9,2,1

'CPR',

BENDING MOMENT AT ELEMENT 6, NODE 1 specifies time dependent rotational speed

'RSG'....

'RSG#,1,1200.

28 January 1994 Prepared by: H.L. Hassenpflug 36

B&W/ NUCLEAR Doc. No. 12-1229402-o0 BWSER / ICE COMPANY the parameters on the 'RSG' line are iri n0 ir= rotor number n0= initial speed (rpm) 20.,1200.

the parameters on subsequent cards are t, n (t) where t is a time for which a speed is specified(interpolation between time n (t) is the speed at that time

..... terminates a set of time dependent speeds.....

_\\

' SET'

'COM' l

'COM'

'COM', LOADS AT 1X TO SIMULATE COUPLING TR71N RUNOUT

'COM'

'COM'

'COM',

TOP OF COUPLING

'COM'

'HF1'.... SPECIFIES A HARMONIC FORCE or MOMENT.....

In this application, the harmonic force is used to replicate 3

the effects of coupling train runout

'HF1',1,12,2,-2.0E4,20.,0.,0.

'HF1',1,12,2,-2.0E4,20.,270.,90.

The parameters of the 'HF1' line are ir ist kor,fmag,ffreq, phase, theta 1

r i

where i

j ir = rotor no.

ist = station no.

kor = 1 for lateral force, 2 for moment loading imag = force magnitude in lbs, (lb-inches for moments) ffreq = force frequency (bz)

(dogrees) phase = initial phasetheta = angle of application 0= x-direction, 90 = y-dire 28 January 1994 Prepared by: H.L. Hassenpflug 37

~

Doc. No. 12-1229402-00 f

y i

I i

l

'UNB' Specifies applied unbalance.

In this case a j

'COM' balance weight

'UNB',1,10,400.,0.

The parameters of the 'UNB' line are ir,ist,umag,uphase where ir = rotor number ist= station number umag = unbalance magnitude in oz-inches uphase = initial orientation of unbalance (degrees)

'HF1',1,2,1,1200.,20.,0.,0.

'HF1',1,2,1,1200.,20.,270.,90.

'CCM'

'HF1',1,1,1,1000.,100.,0.,90.

(5X IMPELLER LOAD)

'HF1',1,1,1,1000.,100.,270.,135.

'HF1',1,1,1,200.,200.,0.,90.

(10% IMPELLER LOAD)

'HF1',1,1,1,200.,200.,330.,180.

'COM',

RADIAL LOAD

'HF1',1,2,1,4800.,000.,0.,270.

(DISCRARGE LOAD) specifies upper time limit on integration

'TMx',2.000 (seconds) l

'DTM',.00005

.... specifies integration time step (seconds)

.... suppresses the option to review problem setup I

'DAT' before beginning the numerical integration

^

(

'END'

.... mandatory file terminator l

P l

l Prepared by: H.L. Hassenpflug 28 January 1994 38

5 Bay / NUCLEAR Doc. No. 12-1229402-00 BWSERllCE COMPANY APPENDIX B -- LOWER MOTOR BEARING MODELING Normal Bearing -- For the pre-outage case and the Event 1A B1.

case the lower motor bearing is assumed to have all of its pads in their proper positions, but that the entire bearing is displaced with respect to the motor frame.

This misalignment preloads the bearing and therefore increases its stiffness beyond the value which would normally be expected for the loaded direction.

Stiffness in the loaded direction for this bearing is normally in the range of 1 million 1b/ inch.

Failed Bearing -- The failed bearing model is based on B2.

the following assumptions:

a.

The shaft 'follows' the displaced pad, since it is the primary load bearing pad.

It remains heavily preloaded, The pad opposite the displaced pad becomes totally b.

ineffective, thereby reducing the total bearing stiffness by a factor of 1/2, compared.

c.

The loaded pad and its ' partner' are sufficiently far apart that there is a region over which neither pad contributes materially to supporting the shaft.

l d.

The four ' side' pads have no substantial change in

~i stiffness.

l i

Prepared by: H.L. Hassenpflug 28 January 1994 39

Doc. No. 12-1229402-00 y

APPENDIX C -- DATA FILES Allis-Chalmers RCP Pump Motor Shaft Model for CRTSP2 (free-free modes)

L. Hassenpflug from A-C Drawings (SONGSRCP. CSP)

Prepared by H.

12-12-93 50 3

1 50 1

3 2

2 0

1 1

08

-1

-1 1

.9

-1 1

0 0

1.2 E3 0

50.2 E3 0

1 5.000E+07 0

3 5.000E+07 0

0.000 15.000 10.250 7.875 0.000 0.000 30.000 0.283 4070.000 11.062 10.250 7.875 251823.9 176760.1 30.000 0.283 312.370 7.250 10.250 0.000 30080.91 16633.6 30.000 0.283 311.523 4.375 7.748 0.000 32015.91 17696.7 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0,000 30.000 0.283 0.000 8.000 7.638 0.000 0.000 0.000 30.000 0.283 450.000 12.250 10.750 8.750 0.000 0.000 30.000 0.283 0 000 12.250 10.750 8.750 0.000 0.000 30.000 0.283 0.000 12.500 10.750 8.750 0.000 0.000 30.000 0.283 450.000 12.500 10.750 8.750 0.000 0.000 30.000 0.283 0.000 11.000 9.500 0.000 0.000 0.000 30.000 0.283 0.000 4.333 9.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 3.112 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283' O

1.463 9.5 0

0 0

30.

0.283 0.000 4.575 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.200 14.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.300 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 1435.000 6.600 22.468 0.000 6.05E+05 3.11E+05 30.000 0.215 1435.000 2.902 22.468 0.000 6.05E+05 3.11E+05 30.000 0.215 0.000 4.698 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 1617.330 5.000 22.468 0.000 7.58E+05 3.70E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000-0.215 1336.667 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1336.6G7 5.000 22.468 0.000 6.15E+05 3.11E+05 30.000 0.215 1617.330 4.775 22.468 0.000 7.58E+05 3.70E+05 30.000 0.215

'O.000 4.934 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 0.000 4.934 22.468 0.000 0.00E+00 0.00E+00 30.000 0.215 3895.000 4.934 22.468 0.000 2.13E+06 1.18E+06 30.000 0.215 3895.000 3.722 22.468 0.000 2.13E+06 1.18E+06 30.000 0.215 0.000 6.146 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.934 12.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.800 11.772 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500-0.000 0.00E+00 0.00E+00 30.000 0.283 O.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 4.867 11.500 0.000 0.00E+00 0.00E+00 30.000 0.283 28 January 1994 Prepared by: H.L. Hassenpflug 40

B&WNUCLEAR poc* no' 12 12294o2-o0 BWSERVICE COMPANY O

3.858 11.5 0

0 0

30, 0.283 0.000 0.675 11.500 0.000 0.00E+00 0.00E+00 - # -30.000 0.283 1520.000 5.200 11.500 0.000 1.17E+05 2.53E+05 30.000 0.283 0.000 5.450 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.450 9.500 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.200 9.000 0.000 0.00E+00 0.00E+00 30.000 0.283 0.000 5.320 8.304 0.000 0.00E+00 0.00E+00 30.000 0.283 696.000 8.304 0.000 4.01E+04 2.81E+04' 30.000 0.283 0.000 10.942 7.900 0.000 0.000 0.000 30.000 0.283 100.000 3.808 7.900 0.000 0.0 0.000 30.000 0.283 0.000 4.130 7.900 0.000 0.000 0.000 30.000 0.283 0.

O.

O.

O.

01.000 5000.

25.

e i

t 28 January 1994 Prepared by: H.L. Hassenpflug 41

B&W NUCLEAR poc* no* 12-12294o2 o0 BWSERWCE COMPANY i

l

~

LGB MISALIGNED 0.025 IN., K= Normal (PREOUTGE. MOD)

'CPR', SONGS RCP AN.

B-J PUMP

'CPR',SIEMENS MOTOR (MODEL ADAPTED FROM ANO-1),

'CPR'

'CPR',

Rotor Only

'CPR',12-22-93

• RTR',97,O.,*from CRTSP2,(SONGSRCP. CSP)'

e

'COM'

'BRG',1,43,0,1,0,'

NOMINAL UPPER MOTOR BEARING'

'COM'XXX',.659E6,-5400.,8800.,1.412E6,1200.

'CXX',.1461ES,217.,-200.7,.1468E5,1200.

'NLB',1,43,0,1,1,1,0,'

MISALIGNED UPPER MOTOR BEARING '

.659E6, 1412E7,0.,0.002,0.001,0.001,.000

'COM'

'BRG',1,18,0,1,0,'

NOMINAL LOWER MOTOR BEARING'

'COM'KXX',.3641E6,3740.,.1464E5,.1068E7,1200.

• CXX',.1150E5,194.5,4.7,.1565E5,1200.

'NLB',1,18,0,1,1,1,0,'

MISALIGNED LOWER GUIDE BEARING O.3641E6,2.10E6,0.,0.001,0,001,0.001,.025

'NLB',1,18,0,1,1,1,1,'

LOWER GUIDE BRG CONTACT MODEL '

1.00E6,1.00E6,0.,0.020,0.250,0.001,.025

'COM'

'BRG',1,1,0,1,0,' case wear ring' NORMAL (PER B-J)

'XXX',.1257E5,.1559E5,.170SE5,.1541E5,1200.

NORMAL (PER B-J)

'CXX',200.6,-26.4 -25.56,200.8,1200.

'NLB',1,1,0,1,1,1,1,*

CASE WEAR RING CONTACT MODEL '

2.E7,2.E7,0., 120,.35,0.,0.

'COM'

'NLB',1,3,0,1,1,1,1,'

HSB CONTACT MODEL (bottom edge)'

2.E6,2.E6,0.,.060,0.35,.0001,.000

'NLB',1,3,0,1,1,1,0,'

HSB MODEL (bottom edge)'

.250E6,.250E6,0.,.0001,0.00,.0001,.000

'NLB',1,4,0,1,1,1,0,*

HSB MODEL (TOP edge)'

.250E6,.250E6,0.,.0001,0.00,.0001,.000

'COM' DAMPING AND ROTATIONAL STIFFNESS *

'BRG',1,4,0,1,0,*

NOMINAL HSB,

'KTT',3.E6,0.,0.,3.E6,1200.

'CXX',050

,0.,0

,050.,1200.

'COM'

'NLB',1,9,0,1,1,1,1,' CARBON RING RUB MODEL' 50000.,50000.,0., 040,.25,.001,0.001 (PROPERLY ALIGNED)

'COM'

'BRG',1,28,0,1,0,'

MAGNETIC PULL MODEL'

• KXX',-500000.,0.,0.,-500000.,1200.

• COM'

'COM',

GYROSCOPIC DECLARATIONS

'GYR',1,2,252000.

'GYR',1,22,6.05e5-

'GYR',1,23,6.05e5

'GYR',1,25,7.58e5

'GYR',1,26,6.15e5

'GYR*,1,27,6.15e5

'GYR',1,28,6.15e5 28 January 1994 Prepared by: H.L. Hassenpflug 42

o c- "

12 -12 2 " o 2 - ~

BWifBMEMamv

'GYR*,1,29,6.15e5

'GYR',1,30,6.15e5

'GYR',1,31,7.58e5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1,17e5

'COM'

'COM' MASTER AND SLAVE DOF DECLARATIONS

'COM'

'KST*,1,2,1

'MST',1,4,1

'MST',1,9,1

'SLV',1,10,1

'MST',1,12,1

'MST',1,18,1

'MST',1,25,1

'MST',1,31,1

'MST',1,43,1

'SLV',1,50,1

'SLV',1,12,2

'END' c

Prepared by: H.L. Hassenpflug 28 January 1994 43

BBWNUCLEAR poc' no' 12-1229ao2-oo BWSERVICE COMPANY

'CPR*, SONGS RCP AN.

LGB MISALIGNED O.025 IN.,

K= Normal (EVENT 1A. MOD)-

B-J PUMP-

'CPR',SIEMENS MOTOR (MODEL ADAPTED FROM ANO-1),

'CPR'

'CPR', Rotor only

'CPR',12-22-93

'RTR',97,0.,'from CRTSP2,(SONGSRCP. CSP)*

'COM' NOMINAL UPPER MOTOR BEARING'

'BRG',1,43,0,1,0,'

'COM'KXX', 659E6,-5400.,8800.,1.412E6,1200.

"CXX',.1461E5,217.,-200.7,.1468E5,1200.

'NLB',1,43,0,1,1,1,0,'

MISALIGNED UPPER MOTOR BEARING

.659E6,.1412E7,0.,0.002,0,001,0.001,.000

'COM' NOMINAL LOWER MOTOR BEARING'

'BRG',1,18,0,1,0,'

'COM'KXX',.3641E6,3740.,.1464E5,.106BE7,1200.

'CXX',.1150E5,194.5,4.7,.1565E5,1200.

'NLB',1,18,0,1,1,1,0,'

MISALIGNED LOWER GUIDE BEARING O.3641E6,2.10E6,0.,0.001,0.001,0,001,.025

'NLB',1,18,0,1,1,1,1,'

LOWER GUIDE BRG CONTACT MODEL '

1.00E6,1.00EE,0.,0.020,0.250,0.001,.025

'COM'

'BRG',1,1,0,1,0,' ease wear ring' NORMAL (PER B-J)

'KXX',.1257E5,.1559E5,.1705ES,.1541E5,1200.

NORMAL (PER B-J)

'CXX',200.6,-26.4 -25.56,200.8,1200.

CASE WEAR RING CONTACT MODEL *

'NLB',1,1,0,1,1,1,1,'

2.E7,2.E7,0.,.120,.35,0

,0.

'COM'

'NLB',1,3,0,1,1,1,1,'

HSB CONTACT MODEL (bottom edge)'

2.E6,2.E6,0.,.060,0.35,.0001,.000

'NL3',1,3,0,1,1,1,0,'

MISALIGNED MSB MODEL (bottom edge)'

.250E6,.250E6,0.,.0001,0.00,.0001,.000

'NLB',1,4,0,1,1,1,0,'

MISALIGNED HSB MODEL (TOP edge)'

.250E6,.250E6,0.,.0001,0.00,.0001,.000 l

NOMINAL HSB, DAMPING AND ROTATIONAL STIFFNESS'

'COM'

'BRG',1,4,0,1,0,'

'KTT',3.E6,0.,0.,3.E6,1200.

' CXX ',0 5 0.,0.,0.,0 7,0.,12 00.

'COM'

'NLB',1,9,0,1,1,1,1,' CARBON RING RUB MODEL'

.005 TOWARD DISCRARGE) 50000.,50000.,0.,.040,.25,.001,-0.005 (MISALIGNED

'COM'

'BRG',1,28,0,1,0,'

MAGNETIC PULL MODEL'

'KXX',-500000.,0.,0.,-500000.,1200.

'COM'

'COM', GYROSCOPIC DECLARATIONS

'GYR',1,2,252000.

'GYR*,1,22,6.05e5

'GYR',1,23,6.05e5

'GYR',1,25,7.58e5

'GYR',1,26,6.15e5 l

l

'GYR',1,- ' 6.15e5

'GYR*,1,28,6.15e5

'GYR',1,29,6.15e5

'GYR*,1,30,6.15e5 28 January 1994 Prepared by: H.L. Hassenpflug 44 I

Doc. No. 12-1229402-00 y

'GYR',1,31,7.5Se5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1.17e5

'COM'

'COM' MASTER AND SLAVE DOF DECLARATIONS

'COM'

'KST*,1,2,1

• MST',1,4,I

'MST',1,9,1

'SLV',1,10,1

'MST',1,12,1

'MST*,1,18,1

'MST',1,25,1

'MST',1,31,1

'MST',1,43,1

'SLV',1,50,1 e

'SLV',1,12,2

'END*

l 28 January 1994 Prepared by: H.L. Hassenpflug 45

.l i

J T -

BBWNUCLEAR Doc' NO* 12-1229402-00 BWSER\\flCE COMPANY

• CPR', SONGS RCP ANALYSIS: FAILED / MISALIGNED LGB.(EVENTIB. MOD)~~

FROM ANO-1), B-J PUMP

'CPR',SIEhENS MOTOR (MODEL ADAPTED

'CPR'

'CPR*, Rotor Only

'CPR', 1-24-94

'RTR',97,0.,'from CRTSP2,(SONGSRCP. CSP)'

'COM' NOMINAL UPPER MOTOR BEARING'

'BRG',1,43,0,1,0,'

'COM'KXX',.659E6,-5400.,8800.,1.412E6,1200.

'CXX',.1461ES,217.,-200.7,.1468E5,1200. PROPERLY LLIGNED UPPER MOTOR BEARING

'NLB',1,43,0,1,1,1,0,'

.659E6,.1412E7,0.,0,001,0.001,0.001,.000

'COM'

'~

'BRG',1,18,0,1,0,'

NOMINAL LOWER MOTOR BEARING (damping only)'

'COM'KXX',.3641E6,3740.,.1464E5,.1068E7,1200.

'CXX',.1150ES,194.5,4.7,.1565E5,1200.

LOWER MOTOR BEARING W/ MISALIGNMENT

'COM' PADS

'COM', THIS MODEL REPRESENTS THE CONTRIBUTION OF THE FOUR ' SIDE'

'NLB',1,18,0,1,1,1,0,'

MISALIGNED LOWER GUIDE BEARING (off-load dir.)'

O.3641E6,0.12E6,0.,0.001,0,001,0.001,.025

'COM' DISPLACED PAD & OPPOSITE

'COM*, THIS MODEL GIVES THE CONTRIBUTION OF

'NLB',1,18,0,1,1,1,0,'

MISALIGNED LOWER CUIDE BEARING (load dir.)'

O.,1.05E6,0.,0.020,0,001,0.001,.035

'COM'

'NLB',1,18,0,1,1,1,1,'

LOWER GUIDE BRG CONTACT MODEL 1.00E6,1.00E6,0.,0.020,0.250,0.001,.025

'COM*

'BRG',1,1,0,1,0,' case wear ring' NORMAL (PER B-J)

"KXX',.1257E5,.1559E5,.1705ES,.1541E5,1200.

NORMAL (PER B-J)

'CXX',200.6,-26.4 -25.56,200,8,1200.

• NLB',1,1,0,1,1,1,1,'

CASE WEAR RING CONTACT MODEL '

2.E7,2.E7,0.,.120,.35,0.,0.

• COM'

'NLB',1,3,0,1,1,1,1,'

HSB CONTACT MODEL (bottom edge)'

2.E6,2.E6,0.,.060,0.35,.0001,.000

'NLB',1,3,0,1,1,1,0,'

MISALIGNED HSB MODEL (bottom edge)'

.250E6,.250E6,0.,.0001,0,00,.0001,.000

' NI.B ',1, 4,0,1,1,1, 0, '

MISALIGNED HSB MODEL (TOP edge)'

.250E6,.250E6,0.,.0001,0,00,.0001,.000

'COM' DAMPING AND ROTATIONAL STIFFNESS'

'BRG',1,4,0,1,0,'

NOMINAL HSB,

'KTT',3.E6,0.,0.,3.E6,1200.

'CXX',050.,O.,O.,050.,1200.

'COM'

'NLB',1,9,0,1,1,1,1,' CARBON RING RUB MODEL' 50000.,50000.,0.,.040,.25,.001,0.005 (ring is 0.005 opposite discharge)

'COM'

'NLB',1,28,0,1,1,1,0,'

MAGNETIC PULL MODEL (moves w/ motor frame)'

-500000.,-500000.,0.,.001,0.,.001,0.000

'COM'

'COM', GYROSCOPIC DECLARATIONS

'GYR',1,2,252000.

'GYR',1,22,6.05e5 28 January 1994 Prepared by: H.L. Hassenpflug 46

Doc. No. 12-1229402-00 gy

'GYR',1,23,6.05e5

^

'GYR',1,25,7.58e5

'GYR',1,26,6.15e5

'GYR',1,27,6.15e5

'GYR',1,28,6.15e5

'GYR',1,29,6.15e5

• GYR*,1,30,6.15e5

'GYR',1,31,7.58e5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1.17e5

'COM' MASTER AND SLAVE DOF DECLARATIONS

'COM' i

'COM*

'MST*,1,2,1

'MST',1,4,1

'MST',1,9,1

'SLV',1,10,1

• MST',1a12,1

'MST',1,18,1

'MST*,1,25,1

'MST',1,31,1

'MST*,1,43,1

'SLV',1,50,1

'SLV',1,12,2

'END' i

28 January 1994 Prepared by: H.L. Hassenpflug 47

. _.~.

Doc. NO. 12-1229402-00 p

'CPR', SONGS RCP ANALYSIS: FAILED / MISALIGNED LGB (EVENT 2. MOD). '

B-J PUMP'

'CPR',SIEMENS MOTOR (MODEL ADAPTED FROM ANO-1),

'CPR'

'CPR', Rotor only

'CPR',12-22-93

'RTR',97,0.,'from CRTSP2,(SONGSRCP. CSP)'

• COM' NOMINAL UPPER MOTOR BEARING'

'BRG',1,43,0,1,0,'

'COM'KXX',.659E6,-5400.,8800.,1.412E6,1200.

'CXX*,.1461E5,217.,-200.7,.1468ES,1200. MISALIGNED UPPER MOTOR BEARING

'NLB',1,43,0,1,1,1,0,'

659E6,.1412E7,0.,0.002,0.001,0.001,.010

'COM' NOMINAL LOWER MOTOR BEARING (damping)'

'BRG',1,18,0,1,0,'

'COM'KXX',.3641E6,3740.,.1464E5,.1068E7,1200.

'CXX',.1150ES,194.5,4.7,.1565E5,1200.

' SIDE' PADS THIS MODEL REPRESENTS THE CONTRIBUTION OF THE FOUR

'COM',

MISALIGNED LOWER GUIDE BEARING

'NLB',1,18,0,1,1,1,0,'

O.3641E6,0.12E6,0.,0.001,0.001,0.001,.015

'COM' DISPLACED PAD & OPPOSITE

'COM' THIS MODEL GIVES THE CONTRIBUTION OF

'NLB',1,18,0,1,1,1,0,'

MISALIGNED LOWER CUIDE BEARING O.,1.0E6,0.,0.0200,0.001,0.001,.025

'COM' LOWER GUIDE BRG CONTACT MODEL

'NLB',1,18,0,1,1,1,1,'

1.00E6,1.00E6,0.,0,020,0.250,0.001,.015

• COM*

'BRG',1,1,0,1,0,' case wear ring' NORMAL (PER B-J)

'KXX',,1257ES,.1559ES,.1705ES,.1541E5,1200.

NORMAL (PER B-J)

'CXX',200.6,-26.4 -25.56,200.8,1200. CASE WEAR RING CONTACT MODEL '

'NLB',1,1,0,1,1,1,1,'

2.E7,2.E7,0.,.120,.35,0

,0.

• COM' HSB CONTACT MODEL (bottom edge)'

'NLB',1,3,0,1,1,1,1,'

2.E6,2.E6,0.,.060,0.35,.0001,.000 MODEL (bottom edge)'

l

'NLB',1,3,0,1,1,1,0,'

MISALIGNED HSB

.250E6,.250E6,0.,.0001,0.00,.0001,.000 MODEL (TOP edge)'

'NLB',1,4,0,1,1,1,0,'

MISALIGNED HSB

.250E6,.250E6,0,.0001,0.00,.0001,.000

\\

NOMINAL HSB, DAMPING AND ROTATIONAL STIFFNESS'

'COM'

'DRG',1,4,0,1,0,'

'KTT',3.E6,0,0.,3.E6,1200.

• CXX*,050.,O.,O.,050.,1200.

• COM'

'NLB',1,9,0,1,1,1,1,' CARBON RING RUB MODEL' 50000.,50000.,O.,.040,.25,.001,O.0010 (PROPERLY ALIGNED)

'COM' MAGNETIC PULL MODEL(MOVES W/ HOTOR FRAME)'

'NLB',1,28,0,1,1,1,0,'

-500000.,-500000.,0.,.001,0,001,0.001,.010

• COM'

'COM', GYROSCOPIC DECLARATIONS.

'GYR*,1,2,252000.

'GYR',1,22,6.05e5

'GYR',1,23,6.05e5 28 January 1994 Prepared by: H.L. Hassenpflug 48

)

Doc. No. 12-1229402-00

'GYR',1,25,7.58e5

'GYR',1,26,6.15e5

'GYR',1,27,6.15e5

'GYR',1,28,6.15e5

'GYR',1,29,6.15e5

'GYR*,1,30,6.15e5

'GYR',1,31,7.58e5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1.17e5-

'cOM' MASTER AND SLAVE DOF DECLARATIONS

^

'COM'

'COM'

'MST*,1,2,1

'MST',1,4,1

'MST',1,9,1

'SLV',1,10,1

'MST',1,12,1

'HST',1,18,1

'MST',1,25,1

• MST',1,31,1

'MST',1,43,1

'SLV',1,50,1

'SLV',1,12,2

'END' I

28 January 1994 Prepared by: H.L. Hassenpflug 49 1

^^ ^ - - - - - - - - - - - - - -

1 I

P3fHs&W NUCLEAR DOC. NO. 12-1229402-00 EDwSERWCE COMPANY (A-C Motor) RCP TRANSIENT ANALYSIS (NORMAL. LOD),,

'COM', SONGS

'CPR', LOAD FILE INCLUDES: (.004) CPLG RUNOUT +4.8K RADIAL +5X+'SLB UNB.

'CPR', WEAR RING RESPONSE

'PLX',1,1,1,1

'PLX',1,1,2,1

'CPR', HYDROSTATIC BEARING LOCATION (BOTTOM)

' PLX ',1, 3,'1,1

'PLX',1,3,2,1

'CPR', HYDROSTATIC BEARING LOCATION (TOP)

'PLX',1,4,1,1 l

'PLX',1,4,2,1

• CPR', PROBE (PUMP) LOCATION

'PLX',1,9,1,1

'PLX',1,9,2,1

'CPR', LOWER GUIDE BEARING LOCATION

'PLX',1,18,1,1

'PLX',1,18,2,1

'COM' DUMMY VELOCITY OUTFUT --

1. PLV',1,9,2,1

'CPR',

BENDING MOMENT AT ELEMENT 6, NODE 1

'RSG',1,1200.

20.,1200.

' SET *

• COM*

'COM' 2X load to simulate shaft keys

'COM'

'HF1',1,9,1,100.,40.,0.,0.

'HF1',1,9,1,100.,40.,270.,90.

'COM'

'COM', LOADS AT 1X TO SIMULATE COUPLING TRAIN RUNOUT

• COM'

'COM'

• COM', TOP OF COUPLING

'COM'

'HF1',1,12,2,-2.0E4,20.,0.,0.

'HF1',1,12,2,-2.0E4,20.,270.,90.

• COM'

'UNB',1,10,400.,0.

'HF1',1,2,1,1200.,20.,0.,0.

'HF1',1,2,1,1200.,20.,270.,90.

'COM'

'HF1',1,1,1,1000.,100.,O.,90.

(5X IMPELLER LOAD)

'HF1',1,1,1,1000.,200.,270.,135.

'HF1',1,1,1,200.,200.,0.,90.

(10X IMPELLER LOAD)

'HF1',1,1,1,200.,200.,330.,180.

'COM',

RADIAL LOAD

'HF1',1,2,1,4800.,000.,0.,270.

(DISCHARGE LOAD)

TMX ',. 5

'DTM',.00005

' BAT'

'END' 28 January 1994 Prepared by: H.L. Hassenpflug 50

BRUiNUCLEAR

• • • • " * *~

940 ~00 BWSERllCE COMPANY i

1 e

28 January 1994 Prepared by: H.L. Hassenpflug 51 7

B&WNUCLEAR BWSERVICE COMPANY To BWNS-20553D-5(10/89)

J.D. Agar - Project Manager, SCE Customer From r File -

H.L. Hassenpflug - Component Engineering Date 1 February 1994 Subj.

SONGS, Unit 2&3, Irose RCPM Lower Bearing Evaluation Details of the dynamic analysis are attached on the following pages. The pur summarized below:

Purpose:

The following is an evaluation of Observability of Loose Lower Guide bearing f in the SONGS Reactor Coolant Pump Motors. It is based on a numerical The analysis uses a time integration a pump / motor with a loose bearing support.

approach.

The purpose of this calculation is to provide an evaluation of those pa may be monitored on an ongoing basis, and which will give prior warn motor bearing support.

Summary of Results:

1xose guide bolts will should be observable when the total bolting loa of the design load. When such a loss of preload occurs, the first and m Gross changes in dynamic indication will be a shift of shaft centerline position.

performance (as monitored with proximity probes at the lower end will probably not be seen unless the bolted joint is entirely relaxed.

Per the terms of the Purchase Order #8H123003, no independent review NOTE:

calculations supporting this document was performed.

i

r DRAFT 12-1229406-00 hf pgy Table of Contents 3

1.

Initiation of Slippage 4

2.

Dynamic Modeling 8

3.

Analysis 9

4.

Results 16 5.

Recommendations 17 6.

References 18 7.

Appendix A 1

28 January 1994 Prepared by:

H.L. Hassenpflug 2

12-1229406-00 h

h gy Initiation of Slippage 1.

The present model addresses the conditions of gross slippage There may be more subtle effects of the bolted joint.

caused by the loss of stress stiffening in the bolted.

but any attempt to structure' prior to gross slippage, address that consideration is beyond the scope of this effort.

The required force to initiate slippage is calculated as follows:

For a single fastener, T = kFD, where T = bolt torque k = bolting constant F = clanping. force D = nominal bolt diameter The clamping force is F=T/kD, and for multiple fasteners, the total clamping force is F, = N T / ( k D).

The slip force is therefore 0:

F, =p N T / ( k D), where p is the coefficient of static friction.

In the present case, the nominal values are p = 0.2 (assumed, low for conservatism)

N = 12 T =195 lb-ft

= 2340 lb-inches k = 0.2 (assumed)

D = 0.75 inches Based on these assumptions, the force required to initiate slippage on a fully loaded joint is i

l F, = 0. 2

• 12

• 2340/ (0.2

• 0.75)

= 37440 lbs.

By comparison, the magnitude of the dynamic load caused by a 10-lb balance weight applied at a 6 inch radius is 28 January 1994

.hreparedby: H.L. Hassenpflug 3

.-~

12-1229406-00 gy 2

F, = U W

' ~

2

= 10lb

• 61n * [ (1200*n/ 30) 1/ sec)2 j 386.4 in/sec

= 2452 lb, less than 10 % of the required load for slippage. Therefore, it is reasonable to expect that gross slippage will not be observable until joint is close to fully relaxed.

There is however, a transition which is the subject of the following dynamic analysis.

2.

Dynamic Modeling A.

Shaft Model The attached analysis draws heavily on the modeling methodology detailed in Task 1 of this contract (Root cause analysis).

The rotor dynamics nodel differs from that used in Task 1 in that the alignment of the motor frame, guide and pump are assumed correct.

In addition, the

bearings, lower motor guide bearing is modeled as a linear bearing in series with a sliding joint.

The COTRAN interface model for a typical condition is attached in Appendix A.

Bearing Model The bearing is assumed to exhibit the normal stiffness for the loaded direction, in this case for both directions.

The load-deflection curve for the loose joint is shown in Figure 1 for loading.

This loading curve will also be valid i

for unloading as long as the dynamic loading is sufficiently small (compared to the magnetic and discharge loads) that the joint does not slide in the reverse direction.

The actual unloading curve is shown in Figure 2.

It is initially assumed for this analysis that the-loading curve remains valid.

This assumption is then validated after the fact.

The model for the_ loading curve is constructed using existing annular gap elements in COTRAN.

The build-up of the model is shown graphically in Figure 3.

Prepared by: H.L. Hassenpflug 28 January 1994 4

l

l i

12-1229406-00 Load vs. Deflection for a Bearing with Partially Figure 1 --

Relaxed Support Fasteners NOTE: Present analysis assumes loading and unloading curves are equivalent -- no backsliding l 570 P 1

2aldd A

llO-SL tP e-SLI P zoas-zons R' i

e l

f/,p

)

loa d 5

g I

l l

SLIP l> PLEtft & $ )

DEPLkcTiot/ f f )

1 28 January 1994 Prepared by: H.L. Hassenpflug 5

h 12-1229406-00 g

gy Figure 2 --

Load vs. Deflection for a Bearing with Partially Relaxed Support Fasteners (actual r.eturn behavior

'~

shown)

{

I R A-(D LcAo G

g sroe 2018 l

l N

l WO-SL IP t-SU P l

20^JE EONG ?

I 4

s S/ p

~~

~

~T

/

loa d 5

g 7

?

l SLII; ScF(ErffMh) 3

/

DSNLEWlO l

l i

i Prepared by: H.L. Hassenpflug 28 January 1994 6

i

\\

B W l l W is"c W M a u r 12-o'os-oo l

i Figure 3 --

Build-up of Bearing Stiffness Model Using Gapped Annular Stiffness Elements D) l P

V t

-+

I

/

ki i

0+@

9 l

P t

}

r._

s l

~

k i

j i

h bs I

5

-R, E

1 (Wh F

P Y

i

=

l f

i f,

Prepared by:

H.L. Hassenpflug 28 January 1994 7

12-1229406-00 hf g

3.

Analysis The initial parameter study is based on three cases:

1.

No slippage 2.

1000 lb slip load, 0.001 in = 6,,

(2.6% preload) 3.

No clamping force

'no-slippage' case covers the majority of The first, operation and assumes that the available frictional force in the bolted joint is greater than the maximum bearing load.

The second case considers is typical of cases where a substantial frictional load is maintained, but where that load is insufficient to prevent slippage of the bolted joint.

The third, or 'no clamping force' case assumes complete relaxation of the bolted joint and that the lower motor bearing is effectively absent.

Results of these three cases are discussed and presented in the following section.

Several other cases were also examined, but are not formally presented here.

In thoso cases the lower guide bearing was misaligned relative to the motor frame.

The results of these cases are also discussed in the following section.

1 i

Prepared by: H.L. Hassenpflug 28 January 1994 8

12-1229406-00 h

h gy 4.

Results The results of the computer simulations described in Section The

'no-slip' 3 are presented graphically in Figures 4-9.

case is shown in Figures 4 and 5, the '1000-lb slip load' case in Figures 6 and 7, and the 'no-clamping force' case in Figures 8 and 9.

Figures 4, 6, and 8 show the orbit as would be observed at proximity probes, while Figures 5, 7, and 9 show the shaft trajectory at the lower motor bearing.

OBSERVATIONS:

The most obvious result is that the orbital shape which 1.

one might expect to observe at the proximity probes does not change substantially from conditions of full support to complete loss of the bolted joint.

However, the 'mean' position of the shaft orbit shifts substantially from a fully constrained bearing to one with no support.

It is important to note that with full loss of the lower guide bearing, position of the orbit continues to precess.

4-By comparison, when a 1000-lb slip load is maintained, 2.

the orbit shifts from one equilibrium position to another, but does not move thereafter.

In the cases where alignment was changed, it was found 3.

but that the trends are the same as discussed above, that movement of the orbit will begin at substantially higher clamping loads.

28 January 1994

, Prepared by: H.L. Hassenpflug 9

.. ~..

gggggCg 12-1229406-00 Figure 4 --

Shaft orbit at Putnp-end of Spool Piece: No-Slip Case J

'I I

mO O (f)

_a m

- F)

SONGS RCP #4.: TASK 2: NO BREAKMfAY (NCSLP. MOD)

}

LOC FLE NCLUDES: (004) CPLG RUNOUT -+4.8K RADVL+5X+ SLB UNS.

)

RUN f 2358 Q_ o (f) 9_

N ON Lt.J O

.l o

LLI o. _

_Q"

._J O

^

Oo x

Q. W

}

o-(f)

N

)

O' LtJ

~

38 O c6 i

i i

J -432.00

-22.00

-12.00

-2.00 8.00 LOWER SPOOL PIECE DISP (MILS)

Prepared by: H.L. Hassenpflug 28 January 1994 10

9 12-1229406-00 Figure 5 --

Shaft Orbit at Lower Motor Bearing: No-Slip Case a9 N

F)

SONCS RCP #4.: TASK 2: NO BREMAWAY (NCSUP. MOD)

LOAD FLE RJCLUDES: (.004) CPLG RUNOUT +4.8K RADVL+5X+ SLB Ute.

RUN f 2358 mw8 d ei-2N v

Q_ 8 m

a~ -

l>-

a CD o _

2 ni

_.J oa od --

1 I

I J32.00

-22.00

-12.00

-2.00 8.00 LMB X-DISP (MILS)

Prepared by: H.L. Hassenpflug 28 January 1994

12-1229406-00 gy Shaft Orbit at Pump-end of Spool Piece: 1000-lb Figure 6 --

Slip Load 0

FMW 9

__J N

BREMAWAY AT 1 MILS (1MLMOD)

SONGS RCP #4.: 7A5K2:

LOAD FLE INCLUDES: (.004) CPLG RUNOUT +4M RIOVL+3X+ SLB UNS M

]

RUN f 2362 O_ o 9 h-a~

LtJUo Ltj o 0"

_J O

~

Oo

- \\

Q_ o --

)

wd 38 i

i i

O cd l

432.C0

-22.00

-12.00

-2.00 8.00 LOWER SPOOL PIECE DISP (MILS) 28 January 1994 Prepared by: H.L. Hassenpflug 12

(

4 12-1229406-00 y

Shaft orbit at Lower Motor Bearing: 1000-lb Slip Figure 7 --

Load o9 N

SONGS RCP M.: TASK 2: BREAKMY AT 1 MLS (1ML. MOD)

F)

LCM FLE t-4CLUDES: (.004) CPLG RUtOJT +4 BK PJO%L+5X+ SLB UNS.

RUN f 2352 mm8 a s-5m v

PA 8 N

~

N 5 d-I>-

o 0] o_

2d

_J oooj 1

1 I

-132.00

-22.00

-12.00

-2.00 8.00 LMB X-DjSP (MILS) 28 January 1994 Prepared by.

H.L. Hassenpflug

.i 12-1229406-00 gy Figure 8 --

Shaft Orbit at Pump-end of Spool Piece: No-Load Case l

n o W9

_J N

-- M SONGS RCP AN.: TASK 2: BREN(AWAY AT 0 MLS (NCL(%D. MOD)

]

LOO FLE NCLUDES: (.004) CPLG RUtOJT +4.8K RAD %L+5X+ SLD UtE.

RUN f 2357 CL o 9 N-C3 N LU O

o Ld o E N-c

_J k>

l O

~

~

f Oo (w

Q_ q -

WN n

b3: 8 os i

i Jo 432.00

-22.00

-12.00

-2.00 8.00 LOWER SPOOL PIECE DISP (MILS)

Prepared by: H.L. Hassenpflug 28 January 1994 14

.. =.

12-1229406-00 g

pgy Figuro 9 --

Shaft Orbit at Lower Motor Bearing: No-Load Case O9m M

SONGS RCP #L: TASK 2: BREAKAWAY AT O MLS (NOLCAD. MOD)

LCM FLE NCLUDES: (.004) CPLG RUNOUT +4.8K R/CVL+5X+ LLB UNS.

RUN f 2357 m

m 8. _

_j

-N 1 ca v

Q_ 8 m

a~

r i

.i O

CO-2W 3

_J l

OO l

d I

i i

432.00

-22.00

-12.00

-2.00 8.00 LMB X-DISP (MILS 1

/

l l

m Prepared by: H.L. Hassenpflug 28 January 1994 15 l

l l

1 DRAFT

- PS111BGWNUCLEAR 1*_1* *zo'_

• E3wSERVICE COMPANY 5.

Recommendations 1.

Shaft centerline 'mean' position should be monitored and trended to detect gross novement which could be indicative of changes in bearing position.

l l

Prepared by: H.L. Hassenpflug 28 January 1994 16 i

2-122940e-oo BWL'# M PBay 6.

References 1.

BWNT Document No. 12-1229402-00, ' SONGS RCP Failure Root Cause Analysis',

H.L. Hassenpflug, 1-94.

l i

l i

l l

l I

i l

28 January 1994 Prepared by: H.L. Hassenpflug 17

12-1229406-00 g

Appendix A -- COTRAN Interface model file (1 MIL. MOD) 7.

'CPR', SONGS RCP AN.: TASK 2: BREAKAWAY AT 1 MILS (1 MIL. MOD) ~ -

'CPR', SIEMENS MOTOR (MODEL ADAPTED FROM Ah0-1), B-J PUMP

'CPR*

'CPR',

Rotor only

'CPR',1-28-94

'RTR',97,0.,'from CRTSP2,(SONGSRCP. CSP)'

• COM'

'BRG',1,43,0,1,0,'

NOMINAL UPPER MOTOR BEARING'

'COM'KXX',.659E6,-5400.,8800.,1.412E6,1200.

'CXX',.1461E5,217.,-200.7,.1468ES,1200.

'NLB',1,43,0,1,1,1,0,'

MISALIGNED UPPER MOTOR BEARING

.659E6,.1412E7,0.,0.002,0.001,0.001,.000

'COM'

'BRG',1,18,0,1,1,'

LOWER MOTOR GUIDE BEARING damping'

'COM'KXX',.3641E6,3740.,.1464ES,.1068E7,1200.

'CXX',.1150E5,194.5,4.7,.1565ES,1200.

'COM'

'NLB',1,18,0,1,1,1,1,'

LOWER GUIDE BEARING 1.LOE6,1.00E6,O.,O.0001,O.0001,O.0001,.00

'NLB',1,18,0,1,1,1,1,'

LOWER GUIDE BEARING

-1.00E6,-1.00E6,0.,0.0020,0.0001,0.0001,.00

'NLB',1,18,0,1,1,1,1,'

LMB Hard Stop

• 1.00E6,1.00E6,0.,0.040,0,000,0.0001,.00

'COM'

'BRG',1,1,0,1,0,' case wear ring'

'KXX',.1257ES,.1559ES,.1705ES,.1541E5,1200.

NORMAL (PER B-J) j

'CXX*,200.6,-26.4 -25.56,200.8,1200.

NORMAL (PER B-J) l

'NLB',1,1,0,1,1,1,0,'

CASE WEAR RING CONTACT MODEL '

2.E7,2.E7,0.,.120,.35,0.,0.

'COM'

'NLB',1,3,0,1,1,1,0,*

HSB CONTACT MODEL (bottom edge)'

2.E6,2.E6,0.,.060,0.35,.0001,.000

'NLB',1,3,0,1,1,1,0,'

MISALIGNED HSB MODEL (bottom edge)'

)

.250E6,.250E6,0.,.0001,0.00, 0001,.000

'NLB',1,4,0,1,1,1,0,'

MISALIGNED MSd MODEL (TOP edge)'

.250E6,.250E6,0.,.0001,0.OO,.OOO2,.000

'COM'

'BRG',1,4,0,1,0,'

NOMINAL HSB, DAMPING AND ROTATIONAL STIFFNESS'

'KTT*,3.E6,0.,0.,3.E6,1200.

'CXX',050.,0.,0.,050.,1200.

• COM'

'NLB',1,9,0,1,1,1,1,' CARBON RING RUB MODEL' 50000.,50000.,O.,.040,.25,.001,0.001 (PROPERLY ALIGNED) l

'COM'

'BRG',1,28,0,1,1,'

MAGNETIC PULL MODEL'

'KXX',-500000.,0.,0.,-500000.,1200.

'COM'

'COM',

GYROSCOPIC DECLARATIONS

• GYR*,1,2,252000.

'GYR',1,22,6.05e5

'GYR',1,23,6.05e5

'GYR',1,25,7.58e5

' GY R',1,2 6, 6.15 e 5

' GYR *,1,27,6.15 e 5 Prepared by: H.L. Hassenpflug 28 January 1994 18

12-1229406-00 h

gy

'GYR',1,28,6.15e5

~

'GYR',1,29,6.15e5

~.

'GYR',1,30,6.15e5

'GYR',1,31,7.58e5

'GYR',1,34,2.13E6

'GYR',1,35,2.13e6

'GYR',1,45,1.17e5

'COM'

'COM' MASTER AND SLAVE DOF DECLARATIONS

'COM'

'MST',1,2,1

'MST',1,4,1 i

'MST',1,9,1

'SLV',1,10,1

'MST',1,12,1

'MST',1,18,1

• MST',1,25,1

'MST',1,31,1

'MST',1,43,1

'SLV',1,50,1

• SLV',1,12,2

'END' Prepared by: H.L. Hassenpflug 28 January 1994 19

~

I 4

APPENDIX B REACTOR COOLANT PUMP MOTOR CURRENT HISTORY Author:

Ray Waldo -

I I_have retrieved a great deal of pump amp data for the RCPs at Unit 3.

The amps for a given pump are dependent upon the.

temperature of the RCS and what other pumps are running.

Thus it is not easy to compare readings at one time with those at another I

time.

It is possible to correct for these effects and attempt to draw some conclusions.

I will be working on the puzzle some more but this is a status to date.

I have four data sets at around Hot Zero Power with four RCPs running.

Correcting them-all to 545 F by use of a factor of

)

-0.73 amp / degree F, I get the following results:

Date 3P002 amps Change 12/20/92 591.0 +/-C.5 10/10/93 595.7 +/-0.6 4.7 +/- 0.8 12/7/93 616.2 +/-0.5 25.2 +/- 0.7 12/13/93 623.2 +/-0.8 32.2 +/- 0.9 The next analysis was to look at pump amps during the 22 minute period near HZP on 12/13/93 when 3P004 was last.run. The aspect of interest here is to see if the motor loading increased or decreased during the run.

The pump was started at about 2040:36.

The readings below are the averages of 5 readings taken 6 seconds apart centered around the time listed.

The values listed are changes from the reference amperage of 591.0 amps at HZP based on the 12/20/92 data.

Change from Reference Time (amps) 2041 40.4 2042 36.0 2043 32.9 2044 34.5 2046 34.1 2048 30.4 2050 33.3 2052 30.2 2054 33.0 2056 30.0 2058 32.2 2100 27.1 2102 32.2 My conclusion from this is that the first two readings are high due to the pump starting up.

I compared this with the start of 3P001 on 12/7/93 at about the same conditions.

It showed very similar high starting amp readings that settled out in the same time frame.

Aside from this, the pump amps appear steady throughout the run of the pump.

There is clearly an increase in motor loading compared to the reference condition a year ago but 3

i

it did not change during the pump run.

Thus the sparks and flame seen at the end of the run were not indicative of some increased loading on the pump.

It also indicates that the high vibration seen during the last part of the pump run either existed for essentially the entire pump run or the vibration was not associated with any increased loading on the motor.

A corron theory is that we had some problem in the shaft alignment which caused the shaft to rub.

That rubbing heated up the shaft and caused it to bow and the bowing heated the chaft further et cetera.

The amp readings indicate that there was no significant change in the shaft loading during the run.

This would argue against the theory of an increasingly bent shaft during the run.

The first table would indicate that there may have been a slight increase in motor loading over the last year but this is a small effect that may not be related to the pump at all.

We will look at that in more detail but the effect is small.

clearly something big changed between the plant shutdown on 10/10 and the pump operation on 12/7/93.

It would also say that the condition was slightly worse on 12/13/93 when the pump was first run after the seal changeout.

The next task is to figure out what went on with the pump during the other pump operations since the refuelling.

These are more difficult to evaluate because they were done at different temperatures and pump combinations.

The two periods of greatest interest are on 11/27 when the pump was first run after its refuelling work was done and over the 3 day period. from 12/4/93 to 12/7/93 when the pump was run continuously.

On 12/4/93 3P002 was started at about 1210.

It was run in parallel with 3P003 from that point until about 1410 on 12/5/93 when 3P001 was started.

Over this 26 hour3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> period the relationship between pump amps for 3P002 and 3P003 remained about the same.

(I do notice a higher variation in pump amps for both pumps at this time than I am used to seeing.

It may be related to the cold 2 pump configuration. At the beginning 3P002 showed 2.8 amps higher than 3P003 but the standard deviation in the difference readings was 12.6 amps.

Typically the standard deviation of a given individual amp reading is about 2 amps.

At the end of the period it was 11 amps difference with a standard deviation of 10.6 amps.

One could say there was an increase in the difference but the uncertainty is high and RCS temperature increased by 200 F during the period so I don't consider the difference significant.)

From 1410 on 12/5/93 until 2210 on 12/5/93'3P001, 3P002 and 3P003 I

were running.

In this 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period the difference between the j

current on 3P002 and 3P003 remained about constant.

(It was significantly different than before due to the running of.3P001.)

At 2210 on 12/5/93 3P001 was stopped and 3P004 was started.

This continued until 0220 on 12/7/93 when 3P001 was restarted.

Over j

2 j

1 c

. - ~..

this period the difference in pump amps between 3P002 and 3P004 was essentially constant.

(It began at 8.8 +/- 2 amps and ended at 12.7 +/- 7.9 amps.)

From 0220 on 12/7/93 until 0530 on 12/7/93 all four RCPs were run.

Over this period the change in temperature corrected pump amps from the 1992 reference value went from about 25 amps to about 23 amps.

Within the uncertainty invol'ied I believe this was constant.

Thus it would appear to me that over the entire period of the 3P002 pump run from 12/4 to 12/7 the motor loading was about 25

}

amps higher than a year ago but did not change unexplainably during the period.

The final question is what was the loading on the pump when it 1

was first started.

3P003 was started at 0429 and 3P002 was started at 0434, 3P003 was then stopped at 0439 and 3P004 stopped at 0444.

When 3P003 was running alone it showed 591.2

+/- 1.5 amps.

This is 12.7 amps lower than the temperature corrected four pump amps for that pump a year ago.

When 3P002 was run alone it showed 609.3 +/- 3.7 amps.

This is 18.3 amps more than the reference value from a year ago.

On 12/30/93 similar sweeps were performed using 3P001 and 3P004.

In that case 3P001 alone showed 51.8 +/- 3.3 amps and 3P004 alone showed 574.6 +/- 1.9 amps.

3P001 showed 25.6 amps less than the reference current a year ago and 3P004 showed 31.6 amps less.

The average of the three other pumps is 23.3' amps less than reference.

3P002 showed 18.3 amps more than reference.

One could say, therefore, that 3P002 seems to have drawn 41.6 amps more than it should have.

There is a wide variation between-the pumps, however.

If you use the other pump on the same day the change appears to be 31.0 amps. It is difficult to say exactly how much 3P002 current was shifted on 11/27 from its reference value of a year ago but it was clearly shifted significantly.

From this I conclude that whatever extra motor loading was added happened between 10/10/93 when Unit 3 was shutdown and 11/27/93 when 3P002 was run.

Based on the first data table above, one could argue that the loading increased after the seal was changed out and the motor position was shifted around 12/10/93 but this effect was minor compared to the shift l

l seen during the original inspection period.

t Ray Waldo i

l 3

. _. _.. ~

4 j

i APPENDIX C

SUMMARY

OF RCP START SEQUENCE RCP STARTS / STOPS U3C6 Author:

Mike Knowlton e

6 n

'1 3/17/93 1145 All RCPs meggered SAT 1247 3MP003 started 1548 3MP002 started I

1548 3MP002 secured (Due to zero speed probe malfunction) 2040 3MP002 started 142,2/93 1011 3MP004 started 1554 3MP001 started t

2313 3MP003 secured (To balance) 3/23/93 0105 3MP003 started 0124'3MP004 secured (To balance) 0313 3MP004 started

. 2046 3MP001 secured (To replace Jower oil reservoir gasket and-l repair oil catch pan) 3/24/93 h

l 1230 3MP001 started l

lr.

1 i

-s w..,

r-.

- ~. - -

RCP STARTS / STOPS U3C7 10/10/93 0021 U-3 reactor manually tripped.

0514 RCP 3P004 secured.

0515 RCP 3P003 secured.

+

10-11-93 Mode 4, P001, P002 in service, ADV HV8419, 8421 in service 0550 Unit 3 entered Mode 5.

1515 Unit 3 - Secured RCP 3P002 to start cooldown to 130 degrees 1750 Unit 3 - Stopped last RCP 3P001.

11-25-93 0532 Unit 3, bumped RCP 3P004 uncoupled for rotation check.

Pump rotated sat.

11-26-93 1100 Unit 3 completed hand rotation of RCP's.

1441 Late entry for 1426, Unit 3 started 3P001 RCP for pump sweep.

Ran for 11 sec. 1441 Unit 3 started 3P002, RCP for pump sweep, ran for 11 sec. 1930 Unit 3 completed testing CCW to RCP check valves sat. 0-23 3-93-213 closed out.

4 11-27-93 0346 Unit 3, completed RCS 1 min purap sweeps with 3P002 18.9 sec and 3P003 15.5 sec. 0444 Unit 3 completed RCS 10 min pump sweeps with 3P903.

10 min i

and 3P002 10 mins.11-28-93 0540 Unit 3 RCP CB0 returned to VCT.

2

~!

11-30-93 Mode 5, 128 degrees F, 340 psig, bubble in pzr SDC in service with P015 0 4200 gpm 0130 Unit 3 started RCP P001 0135 Unit 3 started RCP P004 0145 Unit 3 stopped RCP P001 0155 Unit 3 stopped RCP P004 12-01-93 Mode 5, 129 degrees F, 345#, bubble in pzr SDC in service with P016 @ 4200 gpm 12/02/93 Mode-5, Boron 2642 ppm, Tc 131*F, 348 psia, 30%

P015 1A/2A 4150 gpm.

1603 U-3 started RCP 3P003 and started heat up to 185'F.

1612 U-3 started RCP 3P002.

2240 U-3 secured RCP P002.

CBO temp. indicates 180*F.

CBO flow indicates.09 gpm.

P003 CBO temp. at 120*, RCS at 150*.

12-03-93 t

Mode 5, 146 degrees Tc.

345 PSIA, 2654 RCS. boron.

PO15 on SDC 4150 GPM, P003 RCP in service.

P002 has high CBO temp when in service.

0003 Unit 3 - Started RCP P004.

1405 Unit 3 - Secured RCP's 3P003 & 3P004 for 3P004 speed probe repair.

2020 Unit 3 - Started P001 RCP.

2105 Unit 3 - Started P004 RCP.

2133 Unit 3 - Entered Mode 4.12-04-93 Mode 4, 225 degrees F.

Tc, 350 PSIA, 2649 PPM boron.

P001 and P004 in service, SDC secured.

3

i It-l Heat up to 330 degrees in progress.

i 1030 Unit 3 - RCS pressure at 2250 PSIA.

1131 Unit 3 - Secured RCP P001 and started P003 1205 Unit 3 - Secured RCP P004 and started P002 to support speed probe repair on 3P001 and key phaser repair on 3P004.

2-05-93 Mode 4, 330 degrees Tc, 2250 PSIA, 2649 PPM boron.

P003 and P002 in service, MSIV's closed, MORPH. in S/G.

P001 0.0.S.

for speed probe repair.

P004 0.0.S.

for key phaser repair.

1405 Unit 3 - Started RCP 3P001 after speed probe repair.

2213 Unit 3 - Secured RCP 001 to support maintenance.

2222 Unit 3 - Started RCP 004.

12-06-93 Mode 4, 331 degrees Tc, 39% PZR, 2684 PPM boron.

RCP P002, 3,

4 running.

P001 0.O.S.

for oil. pan work.

1651 Unit 3 - Entered Mode 3.

12-07-93 Mode 3, 535 degrees Tc, 2727 PPM boron.

RCP P002, P003, P004 running 0220 Unit 3 - Started RCP 001 to support hydro.

0230 Unit 3 - Received VLPM alarm STA notified alarms were for Channel 12 and 9.

0930 LE:

Unit 3 RCP 3P002 recleared for seal inspection at 0820.

1620 Unit 3 - Secured RCP 3P003 to commence cool down.

2035 Unit 3 - Entered Mode 4.

12-08-93 Mode 4, 329 degrees F, 2331 PPM boron.

RCPs P001 & P004 running, cooldown of 4

9 RCS in progress to mode-5 for P002 seal work.

0751 LE:

at 0718 Unit 3 entered Mode 5,'RCS temp < 200 degrees F.

0954 Unit 3 - Secured RCP 3P001.

1015 Unit 3 - Secured RCP 3P004; loop temp 137 degrees F.

12-11-93 0348 3P004 run for 20 seconds (pump sweeps) 0906 3P003 run for 30 seconds 1000 3P003 run for 60 seconds (pump sweeps) 1008 3P004 run for 60 seconds 1109 3P003 started (pump sweeps) 1119 3P003 stopped 1114 3P004 started (pump sweeps) 1124 3P004 stopped 12-12-93 0321 3P001 started 0340 3P004 started 1009 Mode 4 1133 3P003 started 12-13-93 2042 3P002 started 2106 3P002 stopped - seal fire 12-14-93 0227 3P003 stopped 12-15-93 0002 Stopped 3P001 l

l 5

.~

d 1

0004 Stopped 3P004-O b

4 4

l l

\\

a a

C 7'

6 4

t

. ~

-. - =

4 k

1 b

efs.' *,

,85 h.s3 "l! hb{f!,f,,'

M

,ph

'j(4'"tl J ' '%,

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j APPENDIX D RCP 3P002 VIBRATION DATA FROM DEC 13 START Author:

Jim Henderson - Station Technical

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weeks FIGURE 1 1X vibration vectors Figure 1 shows a 12 week trend of 3P002

1993, which indicates 3.8 mils at 260 degrees phase in September, t

prior to the U3C7 outage.

Normal unbalance response is <5 mils with a high CONCLUSION:

spot at 260 degrees.

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UNIT 3 RCP'S Table 1 J

Point ID:

3P002 HORIZ Plot:

4 WEEK TREND 19 Nov. 93 16:00 to 17 Dec. 93 08:00:00 Variable:

DIRECT DATE TIME MIN DM4 MAXIMUM AVERAGE MILS PP MILS PP MILS PP 03Dec93 00:00:00 0.0 18.4 9.2 03Dec93 08:00:00 NA NA NA 03Dec9?

16:00:00 0.0 2.3 0.7 04Dec93 00:00:00 0.0 1.7 0.2 04Dec93' 08:00:00 0.0 1.7 0.2 04Dec93 16:00:00 0.0 13.7 5.5 05Dec93 00:00:00 9.7 12.0 10.7 05Dec93 08:00:00 9.8 12.3 10.8 05Dec93 16:00:00 0.0 30.0 10.0 06Dec93 00:00:00 7.6 10.5 9.1 06Dec93 08:00:00 6.3 10.5 9.4 06Dec93 16:00:00 8.6 10.2 9.3 07Dec93 00:00:00 9.4 12.6 10.1 07Dec93 08:00:00 0.0 18.1 8.5 07Dec93 16:00:00 0.7 1.9 1.2 08Dec93 00:00:00 0.5 2.3 1.0 08Dec93 08:00:00 0.0 2.0 0.4 08Dec93 16:00:00 0.0 0.0 0.0 09Dec93 00:00:00 0.0 0.0 0.0 09Dec93 08:0U: 00 0.0 0.0 0.0 09Dec93 16:00:00 0.0 0.0 0.0 10Dec93 00:00:00 0.0 0.0 0.0 10Dec93 08:00:00 0.0 0.0 0.0 10Dec93 16:00:00 0.0 0.0 0.0 11Dec93 00:00:00 0.0 0.0 0.0 11Dec93 08:00:00 0.0 0.0 0.0 i'

11Dec93 1E:00:00 0.0 0.0 0.0 12Dec93 00:00:00 0.0 0.0 0.0 12Dec93 08:00:00 0.0 0.0 0.0 3

12Dec93 16:00:00 0.0 10.7 2.3 13Dec93 00:00:00 0.8 7.6 1.6 13Dec93 08:00:00 0.8 2.3 1.4 13Dec93 16:00:00 0.9 2.6 1.6 14Dec93 00:00:00 0.0 30.0 2.5 14Dec93 08:00:00 0.0 17.4 3.5 14Dec93 16:00:00 0.0 0.0 0.0 15Dec93 00:00:00 0.0 10.1 3.2 15Dec93 08:00:00 0.0 6.0 0.0 15Dec93 16:00:00 0.0 25.2 0.0 3

16Dec93 00:00:0C 0.0 0.0 0,0 16Dec93 08: 00:00 0.0 0.0 0.0 i

2 i

.16Dec93 00:00:00 0.0 o0. 0 0.0' 16Dec93 u08:00:00 0.0 0.0 0.0 16Dec93 16:00:00 0.0 0.0 0.0 17Dec93 00:00:00 0.0 30.0 0.0 17Dac93 108:00:00 0.0 0.0 0.0 Table 2 is a-trend table from November 19, 1993 to December 17, l

1993 showing the minimum, maximum and average of several 3P002 pump starts.

A maximum of 30 mils is seen during the early stages of the December 5,6,7, 1993 pump run._

Normal post maintenance vibration due to coupling and assembly effects is now 8-10 mils.

CONCLUSION:

On december 5, after operating 8 - 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, a transient event occured tripping the vibration, but vibration returned to " normal" after the event.

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1X vibraticn vectors plotted on polar paper show that at the beginning of the december S/6/7, 1993 run the vibration phase was f

at 120 - 130 degrees (nearly opposite the normally observed phase angle).

After the 30 mil spike occured, the vibration phase swung around the pole ending up at 260 - 270 degrees.

CONCLUSION:

A high vibration spike along with restraint of the 4

phase lag prior to, and return of the phase to normal after the spike are strong evidence of a severe shaft rub during the December 5/6/7, 1993 pump run.

a self-limiting condition prevented extended operation at high vibration on this run.

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RUW OP lo So APM TRAltt: tttIT3 BCP'S Point ID: 3P902 UERT O deg Point ID: 3POGZ HORIZ 270 deg 13Dec93 20:4Z:15 Plot: DRBIT 8 TinEBASE TRAMSIEi1T FILE Uariable: IIRFCT H PROBE 3P002 UERT

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2.0 MILS /dio CCW Rat.ation 0 RPn 50 n:;/div FIGURE 3 Figure 3 is the shaft orbit at 1050 RPM during the December 13, 1993 acceleration to speed showing highly chaotic orbit motion prior to achieving 1185 RPM.

Previous observation shows these pumps to be stable at 700 RPM.

CONCLUSION:

History of prior pump stability at much lower speeds indicates that shaft rub was occuring on this pump runup.

6

YGOL 5W h VA)Uf g.Rit[ysG WU pen IMIN: UNIf3 TEP'S cab OpY g f' foint ID: 3r002 HOMIZ Plot: B'JDE TRANSIENT FILI 133nc't128:42:10 in 13DecS3 21:06:6 Variable: 1X MH: tual 6.0 p B'

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FIGURE 4 December 13, 1993 delta RPM triggered IX vector plot showing vibration response during acceleration transient with indication of 10 mils upon achieving full pump speed of 1185 RPM.

CONCLUSION:

Extreme high vibration did not occur until later in the pump run.

7

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TRAIN: UNIT 3 KP'S VEN' foinL ID: 3PoehWERT 0'deg Ref: -0.24 voila Point ID: 3P0012MlHl7.

270 deg Nef: -10.4 volts 1;iikc33 08:i0:98 to 14Dec33 08:20:00 Uar: PRDBE GAP 24 FURIH THEND AUE eVDVR Stiari CENIERLINE POSIIl0M (not orbit or polar plot)

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7. g MI L & d i o CCW RilTAl filN FIGURE 5 Shaft centerline motion showing static position inside clearance 1

during the December 13, 1993 acceleration, steady state, rundown and post cooldown periods.

Shaft desplaces >40 mils in 40 minutes during and after the pump run, shaft is restored to the original starting location after an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> cooldown at rest.

l CONCLUSION:

The shaft had severe teraporary thermal bow that was relaxed back to normal after the shaft cooled down.

j 3

4 8

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l APPENDIX E EVALUATION OF THIS PROBLEM FOR SONGS 2 Author:

Neal Quigley -

Station Technical t

1 s

l 14EMORANDUM FOR FILE January 31, 1994

SUBJECT:

Assessment of loose lower Reactor Coolant Pump (RCP)

Motor Bearing for SONGS Unit 2 P

PURPOSE This assessment is being prepared to address the effects of a potentially loose lower motor bearing mountir.g plate on the operating Reactor Coolant Pumps in SONGS Unit 2.

HISTORY While completing of work on RCP 3P002 during the recent Unit 3 Cycle 7 refueling outage, it was discovered that one lower motor bearing pad had become loose.

The motor bearings consist of 6 tilting disc pads which are adjusted with a jackscrew located directly behind each pad.

During the outage work, Edison noted that one jackscrew had become loose.

This alluaed one of the bearing pads to travel away from the motor shaft and, as a result, would no longer support the motor shaft.

This is further discussed in Root Cause Report RCE 94-002.

Following the discovery of the loose jackscrew, Edison decided to inspect two other RCP's (3P003 and 3P004) for similar problems.

Specifically, Edison disassembled the motor oil drip pans and uncoupled the motor from the pump to complete bearing alignment checks.

This inspection revealed that the lower motor bearing on 3P002 was loose.

(Note that 3P001 was not inspected as bearing alignment checks had already been performed when the lower motor bearing was completely disassembled during the Cycle 7 maintenance activities and therefore, was not considered to be a potential problem.)

While performing the maintenance activities on 3P003, it was found that its lower motor bearing mounting plate was loose and had moved to a position that prevented the motor shart from being centered in the stator /trame.

Upon further inspection, it was discovered that twelve 3/4" mounting bolts were loose and two of the twelve bolts were missing.

The lower motor bearing mounting plate on 3P003 was repositioned to allow centering of the shaft in the stator / frame.

The two missing bolts were replaced and all bolts were torqued to secure 1

the mounting plate into this position. This discovery was made after the same work was completed on the other RCPs (3P002 and 3P004).

After the discovery of the loose mounting plate on 3P003, the other pumps (3P001, 3P002 and 3P004) were disassembled 1

1 1

as required to allow access for reinspection of the lower motor bearing mounting plate bolted joint.

The mounting plate on 3P001 was found to be tight,.3P002 was found to be loose, and 3P004's mounting plate bolts were required to be tightened approximately 1/12 of one turn to achieve full torque on its fasteners.

DISCUSSION Pump Configuration:

The RCP assembly is a vertical pump assembly with a vertical single stage centrifugal pump.

The motor and pump are connected by a removable spool piece.

There are two radial bearings and e.

dual acting thrust bearing in the motor.

The pump employs a hydrostatic bearing incorporated into the impeller.

The RCP shaft seal package is located between the lower motor bearing and the pump.

The lower motor bearing mounting plate is installed in the frame from the top before the rotor is installed in the. frame.

The motor frame has a. machined register into which the bearing mounting plate fits.

The gap between the frame and the plate is approximately 0.100" with electrically insulating materials between all mating curfaces.

Both vertical and horizontal surfaces have insulating material between them and insulating sleeves and washers are used on the fasteners.

The thickness of the insulating material is approximately the same as the radial gap between the bearing mounting plate and the motor frame and, consequently,'will allow only very minor movements of the plate.

If the bolts became loose enough to relax the clamping force on the joint, the plate would be allowed to. move within the clearance of the register.

If the bolts were to become loose enough to fall they would land in the Appendix R oil drip pans and be contained within the gravity drain system.

The RCP speed sensing system consists of a toothed disk mounted to the shaft and electrical speed probes attached to the mounting plate and provide input to the Core Protection Calculator (CPC).

The gap between the probe and toothed disk'is approximately-0.050".

In order for an RCP speed sensor to be damaged, the RCP shaft must be displaced by approximately 0.050" without.the mounting being moved.

In this unlikely event the probe would either be mechanically damaged and fail or the electrical coupling between the toothed disk and speed probe would be lost.

If the RCP speed signal from both probes is lost, the CPC's-would generate a reactor trip.

Vibration Monitoring:

All of the RCPs have been provided with single plane vibration monitoring capability.

The vibration monitoring package consists 2

of two proximity probes and a keyphasor probe.

These sensors or instruments are connected to a communication processor (one for each Unit) that continuously monitors each parameter for an off normal condition on the RCPs.

These signals are then multiplexed to a dedicated computer that continuously collects data which can be displayed upon user request.

This equipment is used to provide continuous monitoring of overall vibration displacement and filtered displacenents at IX and 2X running speed, associated phase angles for the filtered readings, and shaft orbits for all of the RCPs.

Additionally, the system also provides for various trending capabilities of these parameters.

The trending options for the RCPs include the capability of capturing system transients, such as a RCP start or shutdown, and I

various longer trending options of maintaining data from a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period up to 12 week intervals.

Seal Design / Monitoring:

l l

The retrofit seal package was designed as a joint effort by Sulzer-Bingham and Edison.

The new seal was designed with the benefit of years of operating experience that was provided by the seal vendor and the experience accumulated at SONGS.

Numerous features are employed in this new seal to provide a robust design i

with a high degree of reliability.

One of the most important I

features is that this seal design incorporates three seals in j

series, each of which is designed to withstand full system pressure.

A fourth seal, known as the vapor seal, can also 1

withstand full reactor coolant system pressure, was also included in the new seal design to further increase the design margin of this seal package.

The RCP seals are all instrumented with numerous sensors. The seal faces are cooled by a continuous flow of RCS fluid.

This fluid flow is known as RCP controlled bleed off (CBO).

Both the CBO temperature and CBO flow rate are monitored.

Additionally, the individual pressures between each seal " stage" are monitored.

All of these parameters are provided with alarms (either by control board instruments or computer generated alarms) to alert the control room operators of any off normal conditions.

Further Investigation:

A computer simulation of.the RCP assembly has been prepared by the pump vendor and is being modified to simulate the relaxation in the stiffness of the lower motor bearing.

The existing model was prepared to help further understand the dynamic response of pump / motor system.

The computer simulation was used to model the incident that occurred while attempting to return RCP 3P002 to service.

The design bearing gaps in the motor radial bearings (upper and lower) and the hydrostatic bearing in the pump are 0.004" and 3

.---______-_-___________-_---_x--_2_-

(

0.030", respectively.

The lateral clearance in the RCP seal, between the rotating shaft sleeves and stationary secondary shaft sleeves, is 0.070".

Preliminary results have shown that with the allowable vibration levels, the rotating and non-rotating seal sleeves will not make contact.

This is true only when the three bearings in the pump / motor system are aligned concentrically within tolerance, unlike the gross misalignment found on 3P002.

Preliminary results from the modified computer model indicate that the orbital shape which one might expect to observe at the proximity probes does not change substantially from conditions of full support to complete loss of the bolted joint.

However, the mean position of the shaft orbit shifts from a fully constrained bearing to one with no support.

Since dynamic vibration information is most likely to change only after rubbing has already occurred, a more appropriate parameter to trend would be shaft centerline positioning.

The preliminary results of the modified computer model support this conclusion.

The vibration monitor has the ability to determine bearing eccentricity (static shaft centerline displacement) using informetion from the two proximity probes installed on each RCP.

Since the shaft bearings have a fairly small gap when compared to the shaft seal lateral clearance, a fairly large movement is required to allow a rub to occur and begin to change the vibration signatures.

Monitoring shaft centerline position would provide the earliest indication of any trend in the bearing support system.

operating History:

As stated above, the lower motor bearing mounting plate for 3P003 was found with the clamping bolts loose.

Since no maintenance was performed on this joint during this outage (prior to discovery) it can be concluded that this joint was in this condition prior to this refueling outage.

Vibration data on this pump prior to the outage was approximately 6 mils direct (or overall) on both probes and there was no apparent seal stress or degradation.

The seal in 3P003 was replaced during the previous (U3C6) refueling outage and had performed satisfactorily and as such was not replaced during this outage.

The vibration levels of 3P003 following the restart of the Unit was approximately the same as that prior to the outage'and all were within expected values.

The only maintenance on this pump during this outage was to realign the lower motor mounting plate and secure in place with no appreciable change in vibration levels noted.

The seal package for the RCPs has a very good operating history and has exhibited high reliability.

As an example, the seal package installed in RCP 2P002 during the Unit 2 Cycle 6 4

{

u

4 refueling outage developed a problem very early in the cycle that culminated in one completely failed etage.

However, due to the multiple stage design of the seal pm kage, the Unit was allowed to run for the remainder of the fuel cycle and the RCP seal functioned properly without further incident.

The failed seal was further tested and withstood two reactor trip transients (4/24/92 and 7/31/92) without any further degradation.

This occurrence is an example of the seal design's performance capability and is a testament to its reliability.

CONCLUSION Based on vibration data for 3P003 (before and after the U3C7 refueling outage) and the condition of the lower motor radial bearing mounting plate that existed prior to U3C7 refueling outage, it is reasonable to believe that the loss of the lower l

motor bearing support is not a significant problem and therefore would not lead to seal damage or a reactor trip.

Continuous vibration monitoring will be used to detect changes in i

a RCP bearing support system that could be detrimental the seal.

l Indications that will be monitored are shaft centerline position, l

displacements and phase angles.

The shaft centerline position will be an effective tool that will indicate a change in the bearing support system.

A change ia vibration displacement could be indicative of a change in the shaft bearing support system but will most likely be an indicator only after shaft rubbing has begun to occur.

A change in phase angle would indicate a change in the shaft "high spot" position (relative to the keyphasor) that might be caused by a rub.

As a result of this discussion it can be concluded that with satisfactory RCP seal parameters, vibration levels, and an absence of a bearing eccentricity trend, continued operation of Unit 2 is warranted.

Furthermore, by continually monitoring the above parameters a condition that could cause seal degradation would be detected and measures could be taken to correct the problem or shutdown the unit before damage to the seal could occur.

Neal Quigley cc:

D.

P.

Breig R.

Waldo W.

W.

Strom C.

E.

Williams M.

M.

McGawn M.

A.

Herschthal 5

J.

R.

Rudolph N.

J.

Quigley M.

Wade, ABBCE CDM i

6

APPENDIX F RCP 3P002 MAINTENANCE HISTORY l

l AUTHOR:

Dick Borden - Quality Assurance i

I t

4 C______________._________._____________

December 22, 1993

SUBJECT:

Units 2 & 3 Reactor Coolant Pump Bingham-Willamette Seals and Pump Motor Bearings - Maintenance History Review TO:

W.

Strom At the request of the Independent Safety Engineering Group, in support of a Root Cause Evaluation, Quality Assurance personnel completed a review of the maintenance histories of the Units 2 and 3 Reactor Coolant Pumps Bingham - Willamette (B&W) Seals and the pump motor bearings both upper and lower.

The review was conducted to identify unusual equipment conditions documented on maintenance orders and nonconformance reports by Maintenance and Engineering personnel during inspection and maintenance activities.

The SOMM system and CDM files were accessed to obtain history information from the time of original installation of the B&W seals to the present and all SOMM's data related to motor bearings.

Completed documents and records were reviewed,for unusual conditions and time lines developed for the history of each pump.

Additional, all Mos related to maintenance on the eight RCP pumps and/or motors were reviewed via the SOMM's system.

Attached is a listing of unusual conditions documented on the maintenance orders and nonconformance reports reviewed.

Should you have any questions'regarding this review please contact Dick Borden/86-332 or Tom Redenbaugh/86-174.

RICHARD L.

BORDEN 1

RCP MAINTENANCE HISTORY DOCUMENTATION RECOVERY SELECTION METHODOLOGY 1.

SOMM history files (IMOH) were searched using plant equipment numbers:

PUMPS MOTORS S2/3-1201MP001 S2/3-1201MM001 S2/3-1201MP002 S2/3-1201MM002 S2/3-1201MP003 S2/3-3201MM003 S2/3-1201MOOO4 S2/3-1201MM004 2.

Print outs of the MO indexes (copied from the IMOH files) were reviewed to select Mos for further review based on the verbiage within the description fields.

If there was any mention of seals, seal cartridge, heat exchanger, motor bearings or shaft alignment inspection or maintenance activities the MO was selected for further review of the work done section of the MO.

3.

Reviews of the MO work done section were conducted to identify any documented unusual equipment conditions recorded during inspection or maintenance activities by maintenance or engineering personnel.

4.

Documented unusual equipment conditions or activities were then listed.

5.

RCP seal work time lines were drawn.

Associated RCP seal NCRs were included in the time lines.

6.

Add.itionally, the work done sections of all S31201MM002 -

MA3 Mos in SOMM category 90 (IMOH) were reviewed for unusual equipment conditions or activities that could be associated with motor bearing work or shaft alignment.

No additional Mos containing unusual bearing conditions or activities were identified.

7.

A SAS report was run on the work done sections of Mos related to 3P002 to identify any additional Mos not found using other search methods.

l I

2

l l

UNIT 2 Reactor Coolant Pump Seals l

P001 - No evidence of documented unusual conditions during l

maintenance / inspection activities.

l l

P002 - During seal removal - seal cavity was covered with

{

)

black residue.

Samples to Engineering.

(11/87 MO 87111605001)

" Slight dings were noted on the curvic teeth."

Not NCR condition per Cog. Engineer.

(5/89 MO 89052149) 1 "Found baffle bolts loose.

Went to raise shaft to remove bolts and found shaft would not raise.

NCR 9306136 generated." (6/92 MO 92010178) 1

-1 P003 "As found condition of bolts (baffle) is all were found loose."

" Inspection on gasket register on pump face revealed a gouge of approx 25% of seating area, meets acceptance criteria."

(6/93 MO 92031175)

P004 - Found 1 broken baffle bolt.

NCR 91040100 generated.

(4/91 MO 91021971).

Found 2 broken baffle bolts.

(6/93 MO 92121871) l UNIT 3 Reactor Coolant Pump Seals l

l P001 - No evidence of documented unusual conditions during maintenance / inspection activities.

P002 - During curvic teeth inspection "found burrs &

some deformation on a couple of teeth".

(8/88 MO 88071520000)

" Hydrostatic journal bearing exhibited wear".

Interin disposition - Accept As Is.

(5/90 NCR 90060990)

" Removed ring - all broken", " Metal ring blue from heat" (7/90 MO 89122939000)

P003

" Water leaking around shaft - 50% of o-ring missing" (7/90 MO 90060293)

P004 "Curvic teeth damaged" (7/90 MO 88021304)

" Broken baffle bolts" (4/92 NCR 92040110) 3

l ATTACHMENT 2 UNIT 2 Reactor Coolant Pump Motor Bearings P001 -

(10/87 MO 87051171001)

"...New radial brg. shoes that were used were refurburished, the thrust brg. adjusting had to be ground down from.287 to.246.

Set radial brg.

clearance to.010 after centering performed" "MO step 16 and are optional steps.

They were elected not to be performed..." per Cog. Engineer (MO Step 16 is lower bearing inspection / maintenance)

P002 -

(4/86 MO 85100611)

" Radial Guide bearings were heavily dirt scored, but had a good wear pattern.

Upper thrust bearings were heavily dirt scored and had a oil burn spot on trailing edge."

" Lower bearing inspection was not performed due to time."

P003 -

(10/87 MO 87051174)

...New radial brg. shoes that were used were refurburished, the thrust brg, adjusting had to be ground down from.287 to

.246.

Set radial brg.

clearance to.010 after centering performed" l

"MO step 16 and are optional steps.

They were elected not to be performed..." per Cog. Engineer (MO Step 16 is lower bearing inspection / maintenance)

(4/86 MO 85100609)

" Lower bearing inspection was not performed due to time."

(11/84 MO 84042109)

P004

" Days Engineering inspected radial bearings.

Two had slight scoring. Installed all six bearings and marked the scored ones."

(4/86 MO 85100610)

" Guide shoes are heavily scored, some metal chips and some electrolysis was starting. Upper thrust shoes were heavily scored, metal chips around lift hole..."

" Performed lower bearing inspection. Found lower radial bearing in good shape" (9/87 MO 87051176001)

" Upper and lower thrust bearings were replaced as well as the upper radial bearing"

" Step 16 of work plan not performed (optional) as directed by Station Technical..." (Step 16.is the lower bearing inspection / maintenance) 4

ATTACHMENT 2 (Continued)

UNIT 3 Reactor Coolant Pump Motor Bearings P001 - (2/87 MO 86083497 ) " Put in lower thrust bearings....

thrust runners and locknut.

Installed upper thrust shoes and....."

" Removed lower bearing shell and bearings, replaced bearing - centered shaft."

(5/88 MO88020963001) " Cleaned and inspected the thrust brg shoes."

" Reassembled thrust and radial brgs."

P002 * (10/85 MO85090317)

" Lower brg. inspection was not performed due to the amount of work that was performed to the thrust brg.

Alignment check was not performed because we ran out of time."

• (1/86 MO85122488)

"The thrust runner, upper and lower thrust shoes were replaced.

The upper and lower thrust shoes were modified as per Kingsbury Dwg. #3654 before they were installed."

"We found no indication of why the thrust brg.

fail, because the damage was so great."

• (2/92 MO 91090377)

"All lower thrust bearing shoes were replaced with new inkind bearing shoes." " Installed new bearings in lower thrust bearing leveling plate" " Graves finished installing brg. shoes centered shaft install 004 shim lockup bolts. Installed strong back tightened bolts did not safety wire."

" Lower guide bearing inspection not to be done" P003 - No unusual equipment condition comments about bearings identified in the Mos reviewed.

P004 - (11/85 MO 85090319)

" Lower bearing inspection was not performed due to amount of work that was performed because we ran out of time."

l 5

MO'S APPLICABLE TO MP002 REACTOR COOLANT PUMP MO93041575 - ALIGN SPOOL PIECE / INSTALL SPOOL PIECE AS REQUIRED WORK STARTED 10/11/93 STEP 6 RUNOUT READINGS: Readings taken from matchmark on motor coupling as "0".

AS FOUND READINGS:

0-T 0.000 90 - T 0.000 180 -

T 0.001 270 - T 0.001 B

0.000 B

-0.001 B

-0.008 B

-0.008 TOTAL SHAFT RUNOUT T

0.005 TIR B

0.008 TIR FROM WORK DONE SECTION:

o #1

-o.cw i

180 gN i

sancu 0.004 90 MDT DP 27 -0001

-o cci 90 Puw 270 - 0 00s 0

0.000 0 000 NO WORK DONE BETWEEN 10/13 AND 11/20 ON THIS MO 11/22/93 FOUND THAT SEAL WAS BELOW ADAPTER FACE. TURNED OVER -

NO OTHER SIGNIFICANT ENTRIES.

MO 92060990 - INSPECT THE HYDROSTATIC BEARING WORK STARTED 10/26/93 DISASSEMBLED -- WAYNE MARSH DID INSPt.CTION CENTERED HEAT EXCHANGER TO WITHIN.001 RECHECKED, STILL.001.

AFTER TENS [ONING WAS.0025.

CHECKED AROUND HEAT EXCHANGER FLANGE

{

.022 FEELER GAGE WENT UNDER HEAT EXCHANGER FLANGE.

GENERATED MO93101800 TO REMOVE BAFFLE AND HEAT EXCHANGER DUE TO

{

GAP. (10/28)

WCRK RESUMED 10/30 INSTALLED SEAL HOUSING CENTERED WITHIN.003.

ACCEPTANCE IS.004 PERFORMED CURVIC TEETH INSPECTION. NO PROBLEMS NOTED.

MO 91082524 - BREAK EDGE ON UPPER SHOULDER OF PUMP SHAFT STARTED 10/27/93 BROKE EDGE ON PUMP SHAFT PER FCN F7737M AND F7738M 6

l

4 MO 93101800 - REMOVE BAFFLE HEAT EXCHANGER CURE PROBLEMS ENCOUNTERED ON MO 92060990 - HEAT EXCHANGER WOULD NOT SEAT CORRECTLY WORK STARTED 10/29/93 FLEXITALLIC GASKET CAME APART DURING REMOVAL. NO OTHER PROBLEMS OR NOTATIONS.

MO 93110567 - CBO LINE GASKET REPLACED GASKET STARTED 11/23/93

.005

.005

/

.002 M3fDR

.007.002 PUNP

.000

.000 MO93112080 - RECORD "AS FOUND " DATA AND ADJUST BALANCE RING WORK STARTED 12/1/93.

NO "AS FOUND" DATA ON RUNOUT WAS ASKED FOR IN MO AS LEFT SHAFT RUNOUT: This is per the maintenance supervisor, no specific directions or locations are given.

MO 93120397 - REMOVE AND REINSTALL SPOOL PIECE '

WORK STARTED 12-8-93 STEP 5 RUNOUT READINGS ON THE SHAFT SPOOL PIECE TOTAL.005 - AS FOUND RUNOUT: Location etc per maintenance supervisor 7

O o

~1 2

a CDUPLING SHAri 0

\\

NO AS LEFT READINGS WERE TAKEN

~'

'd MO 93120549 THRUST RING COVER WORK STARTED 12/10/93 INSTALLED CARBON BUSHING MACHINED TO 10.750 MO 93120833 - REMOVE THRUST RING TO INSPECT SHAFT WORK STARTED 12/14/93 COULD NOT REMOVE THRUST COVER-DAMAGE TO THRUST COVER NOTED OPPOSITE KEY AND WEIGHTS MO 93120393 RECENTER THRUST RING COVER NO WORK PERFORMED - SEE MO 93120294 MO 93120294 - CBO FLOW LOW - REPLACE SEAL IF REQUIRED WORK STARTED 12/9/93 19:00 COUPLING HAD BEEN REMOVED ON MO93120347 SEAL CARTRIDGE REMOVED PER 6.2 MEASUREMENTS BETWEEN SHAFT AND ADAPTER BORE

[

m 3140 [T '3151 V

3149 1

%d REPLACED SEAL WITH REBUILT SEAL l

MOTOR NO SWING CHECK WAS PERFORMED PRIOR TO FIRST FAILURE OF CRASH RING MO 93020055 - BALANCE RCP AFTER SEAL WORK NO WORK PERFORMED MO 93081254 - REMOVE / INSTALL THRUST RUNNER l

WORK STARTED 10/14/93 1

8 l

REMOVED RADIAL BEARINGS AND UPPER THRUST SHOES CHECKED FI. OAT SAT AT.025 INCH (THIS IS THE VERTICAL FLOAT BETWEEN THE THRUST BEARINGS..

ADJUSTED UPPER GUIDE BEARING TO WITHIN.002 CENTER.

SHIMMED UPPER BEARING WITHIN.008 TIR ALIGN MOTOR TO PUMP MO 93120582 WORK STARTED 12/10/93 PUSHED MOTOR SHAFT TO DETERMINE TOTAL FLOAT -.024" Upper bearing SWEPT OD OF SEAL ADAPTER AS FOLLOWS:

SMALL V]NDOW 24 0

25,7 x

N\\

30

-15

\\

/

20N

/ -12 k#

0 LARGE WINDOW CENTERED UPPER BEARING WITH.002 GAP. RECENTERED LOWER SHAFT AT COUPLING.

TOOK INDICATOR READINGS:

5 HALL VINDJW 0

j

\\

/

-25 25 (

\\

'N

/

0

' # U '*'

MOVED MOTOR.020 9

12/11/93 MOVED MOTOR TO CENTER MOTOR TO ADAPTER.

MOTOR BOUND ON REGISTER-WITH CENTER BELOW:

SMALL VINDOW 0

1 11

-14 0

SECT LARGE VINDOW IONS 6.7.

1 THRU 6.7.33 NOT PERFORMED (ASKED FOR IN MO IF DIRECTED BY THE MAINTENANCE SUPERVISOR).

NO SWING CHECK IS INDICATED AND THERE WAS NO READJUSTING OF LOWER BEARING.

UPPER BEARING WAS RESHIMMED AND READJUSTED.

10

l l

l APPENDIX G l

TOLERANCE STUDY AUTHOR:

Jennefer Hedrick l

l l

l l

l l

L-----------------.

1 3P002 ROOT CAUSE APPENDIX ON CATIA DEMONSTRATION OF ALIGNMENT /TOLERENCE Catia was utilized to facilitate understanding of the reactor coolant pump / motor alignment variables during the investigation of the Unit 3 Cycle 7 re-start issues associated with P002.

Three alignment tolerance variables potentially caused the " rubbing" of the 3P002 shaft against one side of the seal thrust ring. These are:

motor upper and lower bearing alignment motor lower bearing " slop" pump and motor alignment A Catia model of the pump / motor was generated in order to examine the impact of these variables on the overall pump / motor alignment. The relative importance of each variable to the pump alignment was also assessed. Each alignment / tolerance variable was plotted separately, and also plotted with the other variables to evaluate the effect of the variable on the alignment of 3P002. The alignment variables were plotted using as found information from maintenance and STEC measurements.

The following conclusions can be drawn from the model:

o The combination of misalignment of upper and lower motor bearing, pump to motor misalignment and bearing slop could cause the rub between the seal thrust ring and shaft.

Any single misalignment of either the motor bearing, the pump to motor alignment or the bearing slop would not necessarily cause the rub.

The catia drawings are provided in the attached pages along with a brief description.

FIGURE l-RCP/ MOTOR ASSEMBLY A cross section of the reactor coolant pump and motor assembly is shown in Figure 1. A detail of the seal thrust collar is also provided (View B). Figure 1 is a simplification of the actual computer model which is three dimensional and fully scaled.

Cross sections of the model in Figure 1 will be used in later figures to show the relationship of the alignment variables previously discussed.

FIGURE 2-AS-FOUND 3P002 TOLERANCES / ALIGNMENTS Figure 2 represents the configuration of the pump / motor assembly after the motor move on 12/10/93, using the as-found alignment data. As with the remainder of the figures, Figure 2 is a cross section of the pump / motor assembly.

1

~ _ _ _ _ - _ - _ _ _ - _ _ _ _ _ _ - _ - _ _ _ _ _ - _ _ _ - _. - _ - _ _ _ - - _

l The dashed line titled " theoretical CL of motor" represents the position of perfect alignment of upper and lower bearings within the "A" and "B" motor index references.

The upper bearing is shown is the as-found position measured from the theoretical motor center (dimension "A").

The circle around the upper bearing represents the bearing tolerance to the centerline of the bearing. The point labeled " Shaft and Datum at A" represents the top of J

the motor shaft in the upper bearing at the extreme possible position.

The center of the lower bearing is described as " Center point of "B" dimension." The irregularly shaped bearing clearance for the lower 1

bearing represents the as-found clearances of all the bearing shoes.

The irregular shape is the " position envelope" for the centerline of the shaft. For the purposes of this model, the shaft is considered at the furthest point in the 5:00 position where it is labeled " shaft CL Datum at B".

The point labeled "CL of Pump" represents the centerline of the hydrostatic bearing.

There are two arcs drawn to represent the seal thrust collar dimensions and the hydrostatic bearing clearances on the 5:00 side of the seal where the " rub" occurred.

The dark line drawn from the upper bearing to the " axis position at carbon insert" and back to the centerline of the pump represents the direction that the shaft can take with these alignments and tolerances and shows that the shaft can rub. Specifically, the upper and lower bearing alignments can cause the shaft to ' tilt' toward the 5:00 position. The angle created by that tilt is carried to the top of the pump seal to see if the shaft can rub. In this case, the shaft would be extended into the carbon insert. It is assumed that the maximum displacement of the shaft would occur at the thrust collar and the shaft would ' tilt' back to the center of the hydrostatic bearing. The shaft is essentially bowed from the misalignment and tolerances in the motor and is assumed to arc back into the centerline of the pump.

By following the dark line that represents the shaft, it can be shown that the shaft can interfere with the thrust collar.

i FIGURE 3-CROSS SECTION OF 3P002 CONTACT AREA This figure shows a cross section of the shaft, thrust sleeve carbon insert and thrust ring cover. This figure graphically represents the interference that can occur. The dimensions of the interface vary depending on the assumptions used for the shaft bowing.

FIGURE 4-STUDY OF ALIGNMENT VARIABLE Figures 4 and 5 are hypothetical cases of pump / motor alignments'and tolerances to determine the sensitivity of each alignment variable on

+

l 2

l L

1

the ability of the shaft to rub the thrust collar.

Specifically, Figure 4 is identical to Figure 2 showing the as found conditions (and rubbing) except that Figure 4 eliminates the lower motor bearing slop. Using the dark line as representing the shaft, the figure shows that the shaft would not rub the thrust collar without the bearing slop.

Based on Figure 4, it is concluded that with the motor upper and lower bearing misalignment and the pump / motor misalignment, rubbing would not occur without bearing slop.

FIGURE 5-STUDY OF BEARING TOLERANCE VARIABLE Figure 5 shows that if the upper and lower bearings were.in alignment but there was as-found lower bearing slop, the shaft would not rub on the seal.

In this drawing, the dark line representing the shaft is tilted at the angle possible with the upper bearing to one extreme of the tolerance and the lower bearing to the other extreme in the slop. The shaft is extended to the end and would not rub the thrust collar.

FIGURE 6-PROCEDURAL MAXIMUM TOLERANCE Figure 6 shows the wort case alignment possible with all alignments within procedure tolerances. With the shaft hypothetically positioned at the worst extremes, the shaft would not rub.

FIGURE 7-AS-LEFT 3P002 TOLERANCE The as-left alignments of 3P002 are represented by this figure. These dimensions are as-left prior to the 12/25/93 successful startup of the pump.

.l 3

e I

p rets f aDI AL ttAtlkC p

~~

y UPP(E THRJ57 SLARlhC

[

l

7......,..,..

3s Cs p VLMtL u0104 CASL g

r 80TCR e LOWCE R ADI AL Bi&R)nc I

ft. 498 ft, 487 f t. 473 h370# MALP C%PlimC

$*00L PIECC g

SEE

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-1 m Ni A1 (ICN ANC($

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i tt w y

-,m sm,1c,c..,.

4 n m m

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f

>~1 ~ -.

..,m.......,,

cm....C

,- m m si.:

(N m CAA30p lm$[R1 m*e FIGURE 1

RCP/ MOTOR ASSEMBLY 4

l

4 M otillCAL 4 or noton

.645 514kDARC 1

etamins CL t At ah:(

g

.982

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C(WILR P0lki CT *8* Did Af *A*

23' AS-f0Jm3 BEARINC.636 CLEAEAkCE d*

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Spart ( DAlyg Af ag'

=

.921

'833

.888 Cl># FACT PolNT Af PTCtOSTAllC BCAAlieG Arl$ 9051f10d Al CARB0ti INSE97

.841 CLEAAANCf SEIW(E4 inaull StttVE A4 Cat 90n lustti

.338 CLE ARAhCE TOR HYDROSIATIC 8tattm3 FIGURE 2 AS-FOUND 3P002 TOLERANCES / ALIGNMENTS l

S 1

i 4

CAR 80s in5ERT

,_,.. ~,.

- TWtW57 SLtivt s

\\

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i, x

.885 CLE.RANCE

/

'N N

s I

i FIGURE 3 CROSS SECTION OF 3P002 CONTACT AREA

i e

l 4

Tit [MillCAL 4 W WCOR r.655 STANDAAD

$EARINC I

CL(18 ANCE

"; '.f.*'a h

l

=I a,n. m.1, r.

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$(IEVC skB Camus twSEtt HTDR351 ATIC.C[ FCE

.19 CLE AAAR t As inG F1GURE 4 STUDY OF ALIGNMENT VARIABLE 7

. \\

s 6

1

'l THtDRfflCAL t OF M0?CE, WClos 54 AFT AhD PJWP $hfI WAI Cl5 PLAT (WEWT Of AIll AT *A*

.a23 CEhifR POINI

\\

CT '8* DIN

~

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T,

WOIOR Smart 640 F W sHArt Crut(t PolW1 OF '4" DlW uns DisPLActpiNT CF Asis AT '6"

.642 ZME Alter [D 083

.gA1 CL(ARANCE Sf191(N in#' 58 SLIDi AND J

CAeS04 INSE A1 i

AngA Cr Attenaatt 4 h0VtWENT W1fMIM Arts position g( AR140 CLEARANC[

AT CatBON INSIRI

~.934 Ci(ARA 40E ICR uYttostAtit BEAT!WG FIGURE 5

STUDY OF BEARING TOLERANCE VARIABLE 8

r.

l 4

l 1

j IW10tiliCAL (

OF b370R, 80104 $HAff A2 PUWP $HMI s

8 War OlsPtactislai

,$34 CF AIj$ 47 *4*

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• 8' Diu THECRiflCAL (

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0F WO108, i

-a-uCTOR Spart AND CENTER Point CW

• A* D!w

.982 T0nt ALL0rfC (CR $ HAFT g

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.e95 aatA of AllCWA8it t WOvfd{ti v1 THIN

• OI2

)

8t AAl%3 n[ARANC[

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.514 CLEAE ANCI TCG HYDRC$TATIC 8(AtlkC har gl$PLActugny Of Atl$ AI *G*

Ar!$ pp5]flos Al CA4 BON 14$[R1 At!$ P0511:04 At NYCR05fatic 9tARlWC i

FIGURE 6

PROCEDURAL MAXIMUM TOLERANCE

-l 9

c.

l RCE 94.CO2 Reactor coolant Pump SealDamage, SONGS 3 February 28,1994

~j

~ l

=

i APPENDIX H VISUAL INSPECTION OF LOWER RADIAL BEARING t

AUTHOR: Mostafa Mostafa I

l l

l l

I l

[30] From: MOSTAFA MOSTAFA 3/1/94 10:11AM (2095 bytes: 29 In)

To: JERRY GARTLAND, CHONG CHIU cc: BILL STROM

Subject:

Re: 3P002 lower bearing

_____________________________.-- Message Contents

JERRY, THE JACK SCREW AT THE 5 O'CLOCN POSITION WAS LOOSE THIS WAS MANIFISTED IN A LOOSE LOCK NUT AND A LOOSE SCREW AT THAT LOCATION. IT APPEARS THAT THIS NUT WAS NOT TIGHT FROM DAY ONE DUE TO THE PRESENCE OF HIGH SPOTS'ON THE NUT FACE. THIS CONCLUSION WAS DRAWN BASED ON THE FACT THAT THE PAINT ON THE FLANGE WHERE THE NUT IS TURNED AGAINST WAS UNDISTURBED. IN COMPARISON,THE OTHER 5 NUTS WERE TIGHT AND THE PAINT ON THE FLANGE AT NUT LOCATION WAS DISTURBED IN A TYPICAL FASHION (ROUND SCORING).

THE ASSEMBLY IS CONFIGURED IN A WAY THAT EACH JACKING SCREW AFFECTS ONLY ONE SHOE. IT IS TRUE THAT EVERY SHOE IS BEING RETAINED BY TWO PEICES (SHOE RETAINIMG SEGMENTASSEMBLY) THAT IS BOLTED BY TOW SCREWS VIA LOCKING NUTS. THEREFORE, A LOOSE TACKING SCREW DOES NOT NECESSARILY MEAN OTHER SHOES ARE LOOSE TOO. EACH SHOE HAS A DEGREE OF FREEDOM IN THE HORIZONTAL PLANE ONLY AND ADJUSTED IN PLACE BY MEANS OF SETTING THE JACKING SCREWS.

MOSTAFA, 2/24/94 b