ML051050153
| ML051050153 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 05/25/2004 |
| From: | Karjala D NRC/RGN-III |
| To: | Jeffrey Jacobson NRC/RGN-III |
| References | |
| FOIA/PA-2004-0282 | |
| Download: ML051050153 (4) | |
Text
} Harold Chernoff - PMIC Item - RCP Motor Oil Sludge Page 1 From:
To:
Date:
Subject:
Duane Karja) (a I
John Jacobson Tue, May 25, 2O04 4:35 PM PMIC Item - RCP Motor Oil Sludge John During the 4/30/04 PMIC we discussed the RCP motor oil sludge issue and there was an open question on extent of condition. This is to close that open question.
The attached Corrective Action Program document (OTH057559), discusses the failure mode and extent of condition. Contrary to previous information, they do not believe that the failure mode was mixing of oils.
They believe the failure mode is due to a phenomenon of air entrainment and adiabatic compression which causes severe oxidization of the oil, called "micro-dieseling."
As for extent of condition, apparently it has been established the W motors are susceptible to this and all Point Beach RCP motors are subject to similar problems. The vendor offers an upgrade. Also, they are changing to an oil that is less susceptible.
Let me know if you need further information.
Duane CC:
Harold Chernoff; Kunowski, Michael; Louden, Patrick; Morris, R. Michael
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ij Nuclear Management Company E State Change History OTH Initiate
.0 by MCGOUGH.
JAMES Work Complete I0 by LONG, DOUGLAS Assign Work 5/12/2004 16:34:30 Owner SHERWOOD.
GARY Review &-
Approval 51192004 5:10:51 Owner HENNESSY.
FELICIA Reassign
'0 by-SHERWOOD.
GARY Approved 0
by HENNESSY.
FELICIA v,
Assign Work 511312004 18:48:15 Owner HENNESSY.
FEUCIA f,
i:
Quality Check 5/1912004 8:10:59 Owner PBNP CAP Admin V:
Assign by HENNESSY.
FEUCIA
'Update I0 by KREIL.
JULIE Conduct Work
.511412004 6:58:21 Owner HAWMAN.
JASON
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Licensing Approval 51/211204 8:23:49 Owner CONNOLLY.
JAMES Update 0
,by
- HENNESSY, FEUCIA Page I of 3 Conduct Work
,514=2004 8.07:58 Owner
- LONG, DOUGLAS
'I
- Quality Check 5n112004 14:17123 Owner PSNP CAP Admin Approve 0
by KRAUSE.
CHUCK e Section 1
-Activity Request Id:
Activity Type:
'Site/Unit:
V One Line
Description:
Activity Requested:
t)CATPR:
Initiator Department:
OTH057559 Other Point Beach - Unit 1 Submit Date:
5/1212004 16:34:30 U1R28 RESTART-Oil Sludgefouiing the "8"RCP Motor P-001IB-M
'a.) Document the laboratory testing results of the as-found oilfromthe IP-001B-M RCP motor.
b.) Discuss what conditions cause the oil sludge material to form.
c.) Document the decision-making process used to select the new Mobil DTE Medium grade oil.
d.) Document the extent of condition of the oil sludge problem with regards to the other RCP motors; are they susceptible to the same problem?
N EME Plant/Maintenance Engineering - Eecdrical PB Responsible Department: Engineering Activity Performer
.6 Section 2 LONG. DOUGLAS EU Initiator MCGOUGH. JAMES F-Responsible Group Code: EPT Engineering Programs Testing PB Activity Supervisor HENNESSY. FEUCIA 5)21/2004 7: N
.y Priority:
2 Due Date:
t Mode Change Restralnft 4 Management Exception From Pl' 1 OA/Nuclear Oversight?: N 6 Ucensing Review?:
NRC Commitment?:
N o NRC Commitment Date:
0 Significance Level:
B E Section 3 Activity Completed: 511912004 5:10:51 - LONG. DOUGLAS:
A.Document the laboratory testing results of the as-found oni from the 11P-0011B-M RCP motor.
A report of the Chevron Texaco laboratory analysis report Is attached to document the analysis that was performed on the used oil and sludge removed from the I P-001 B-M RCP upper oil pot during UL1R28. A summary of the oil analysis explains that the oil was severely oxidized. Proof of this is offered by the RPVOT (Rotating Pressure Vessel Oxidation Test) test results. The test results for the oil removed from the motor showed a RPVOT value of c100 while their critical low level Is 4425.
Their belief is that the oxidation of the oil Is being exacerbated by the known air entrainment Issue for this style of motor. There Is no mention of or any reference to oil mixing being an Issue In the problem. In fact, during conversations with the lead formulation engineer at Chevron, he Indicated that mixtures up to 3% were acceptable, as their testing had shown no degradation with up to 12%
mixtures. In addition. RPVOT test results from Herguth Laboratories are attached as Independent validation of the critical oxidation levels present.
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I Harold Chemoff - RCPMtrSludge.pdf P ae2i NuclearManagement Company Page 2 of 3 B.Disaiss what conditions cause the oil sludge material to form.
The mechanism for the sludgeformation Is the severe oxidation of the'oil as i result of adiabatic compression or micro-dleseling' In the area of the thrust bearing as a result of significant air entrainment. The'Chevron GST ISO 46 oil n use on the RCP motors Is not designed to handle the severe air entrainment. The Chevron product Is comprised of a group It base stock mineral oil. This oil Is highly refined to a condition where the molecular structure Is similar to that of synthetic oil. This
'molecular structure produces very few free radicals to allow polar bonding of the additive package to the base stock. In simpler terms. the additive package Is suspended in the base stock rather than bonded at the molecular level. As a result, the anti-foaming additive used In the Chevron oil works by a different method than the older obsolete Amokon product used previously. The Chevron ol uses a polyacralate foam suppression additive that attacks the formation of air bubbles by affecting the tensile strength of the film thereby causing the bubbles to expand until they pop under the surface of the oil. This process Is designed for systems where the oil has a long dwell time In the reservoIr prior to clrculaton'thrbugh the bearings. The upper reservoirs In the RCP motors have virtually no dwell time as the oil Is In constant circulation. The effect that this has Is that as the.
bubbles are expanding they are being pushed through the bearings. This increased bubble size is what aggravates the adiabatic compression. To make matters worse.-when the heavy oxidation occurs In this situation, the anti-oxidants In the oil are consumed at ever higher and higher rates until the oxidation reserve Is exhausted as was noted In this case. The sludge noted In the upper oil pot is the result of the oxidation by-products and some amount of additive fallout due to the high stress levels placed on the oil and the weak additive bonding In the group !I base oil.
C.Document the decision-making process used to select the'riew Mobil DTE Medium grade oil.
Once it was determined that the oil was In-fact oxidizing and the adiabatic compression was having a negative Impact on oil life, an oil was selected for better control of the air entrainment. The air entrainment Is believed to be the primary contributor to the oil oxidation Issue.
To simply restate the cause, 'the polyacralate anti-foaming additive that Is used In the Chevron GST 46 oil Is Ineffective for air entrainment (foaming) control In highly turbulent systems". The Chevron oil is designated a 'turbine oil and Is designed for used In systems with a significant dwell time of the oil. After conversations with EMD Curtiss-Wright (formerly Westinghouse EMD) possible replacement oils were discussed. It was their experience that oils with a silicone based anti-foaming additive was a superior choice for the application. Of the oils discussed. Mobil DTE Medium was identified as the most appropriate for our current motor configuration. The Mobil product Is a group I base stock that Is a less severely refined mineral oil. It has a silicone anti-foaming additive as well as a mild anti-wear additive. It was determined that If the air entrainment could be controlled, that oil with a lower oxidation stability life would be acceptable. The other oils that were possible candidates were synthetic oils. The oil that Chevron recommended In their report. Chevron GST 2300, Is high oxidation stability synthetic oil that does not address the air entrainment issue. Besides the high cost, synthetic oils do not lend themselves to oxidation stability testing. It would be nearly Impossible to test the synthetic oil for remaining oxidation stability life. The benefit of the Mobil DTE Medium Is that the oxidation stability can be checked with a relatively quick and Inexpensive RPVOT test for remaining life. Based on this Information and the fact that Kewanee and Palisades plants have been using the Mobil DTE Medium for many years without any Issues. It was decided that the DTE medium was the oil of choice. The oil change Is documented In SPEED 2004-035.
D. Document the extent of condition of the oil sludge problem with regards to the other RCP motors:
are they susceptible to the same problem?
From an extent-of-condition standpoint. all of the RCP motors at PBNP are susceptible to the sludge formation Issue with the possible exception of the spare motor currently sitting on the unit 1 44' turbine deck. Varying levels of oil oxidation have been noted on at least two of the other motor since their replacement with refurbished motors. The motors of this model have a specific thrust runner design that Is cross drilled with a radial set of holes that function as an oil pump during operation.
The oil discharged from this pump Is allowed to exit the thrust runner Into the flow chamber. The radial discharge configuration of these holes causes air to be whipped Into the all. There Is a modification specified by EMD Curtiss-Wright to correct this defect in the design of the motor. The modification Involves plugging the radial discharge hole In the thrust runner and drilling a set of tangential holes along with modifications tothe flow chamber. WO 0408169 and 0408170 were Initiated to collect oil samples from the unit 2 RCP motors to address extent-of-condition. These samples will be tested for remaining oxidation stability via RPVOT testing as well as for any visible' signs of oil degradation Including Increase in total acid number (TAN). particulate contamination levels and level of oxidation by-products. The samples are scheduled for collection during the 4nCMnA4
H-arold Chernott - Rul-'mirbludge.pat Pace 3ia Nuclear Management Company Page 3 of 3 operating cycle for unit 2 during a forced outage or down-power so that precursors can be Identified prior to U2R27. Until that time, bearing temperatures and vibration levels will be monitored to detect any adverse conditions related to the oil. These Indicators should give significant warning of on deterioration, as the failure mechanism will be a change in film strength of the oil.
511912004 8:10:59 - HENNESSY. FELICIA:
The RCP motor engineer has accepted an OTH.(OTH 013256) to evlauate changing the discharge configuration.
5t2112004 8:23:49 - KREIL, JULIE:
Forwarding to Ucensing for review~as indicated in Section 2 above.
5)21/2004 14:17:23 - KRAUSE. CHUCK, Reviewed by licensing. Appears to be a through evaluation.
Hot Buttons:
(None)
B Section 4 QA Supervisor: (None)
Licensing Supervlson {None)
EAttachments and ParentlChild Unks iUnied From.CAQ5552 by admin it(5/12/2004 16:34:47)
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45-PoLnLEas~h-DInfepdf (50205 bytes) by LONG, DOUGLAS (5119/2004 5:07:31) 52060:1A.P_
(18671 bytes) by LONG, DOUGLAS (5/19/2004 5:09:38)
E Change History 5/2112004 8:23:49 by KREIL, JULIE Last Modifier Changed From To......
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51211200414:17:23 by KRAUSE. CHUCK Activity Completed Changed From OrdgInal TextT To lAppended:] Reviewed by licensing. Appears to b a throuigh evaluation' State Changed From --
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Last Modified Date Changed From To Last Modifier Changed From........ To Last State Change Date Changed From-To Last State Changer Changed From To.'--
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