IR 05000341/1985046
| ML20206T153 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 06/27/1986 |
| From: | Maura F, Ring M, Tomlinson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20206T146 | List: |
| References | |
| 50-341-85-46, NUDOCS 8607080032 | |
| Download: ML20206T153 (19) | |
Text
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION REGION III.
Report No. 50-341/85046(DRS) Docket No. 50-341 License No. NPF-33 Licensee: Detroit Edison Company 2000 Second Avenue Detroit, MI 48224 Facility Name: Fermi Nuclear Power Plant, Unit 2 Inspection At: Fermi 2 Site, Newport, MI Inspection Conducted: November 19, 1985 through June 5, 1986 hMMA-Inspectors: F. A. Maura 4-36-f6 Date kW E. Tomlins $46-f 6 Date Approved By: Chief /A'Z746 Test Programs Section Date Inspe_c_ tion Summary t Inspection on Novemb_er 19_, 1985_ through J_une_5_, 19_86 (Report ho. 50-341/85046(DRS)) Areas Inspected: Special announced inspection by Region III and NRR personnel of the licensee's program to determine and correct the cause of emergency diesel generator bearing failures, an independent analysis of several bearing distress conditions by NRC consultants, and a review of operating and maintenance history at two other nuclear plants with similar engines. This inspection was conducted in accordance with Inspection Procedures 92701 and 92711.
Results: The root cause(s) of the bearing failures could not be positively identified. Several possible contributors were identified and corrected. A test program was performed to demonstrate the engines would perform satisfac-torily within a predetermined envelope. The use of the gap check as an indicator of a distressed bearing is flawed. The Region has no data base to conclude that engines with severely distressed bearings, which pass a gap check, are capable of perfonning their safety function for an extended period of time.
No violations or deviations were identified.
8607080032 860703 PDR ADOCK 05000341 PDR G y
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4' 1.
Persons Contacted
Detroit Edison Company , . abd ! F. Agosti, Vice President, Nuclear Operations ! 'R. Anderson, System Engineer a
l. Burkholder, Maintenance Foreman R. Cole, Maintenance Foreman ' abde. Conen, Licensing Engineer . d ! ab. Fix, Plant Support' Engineer J abde. Green, Systems Engineer J ' a. Lenart, Plant Manager.
J j abcde. Loyallo, Station Chemist P
"d. Nyquist, Diesel Generator Problem Task -Force Leader ! 'J. Silder, Licensing Engineer
R. Wooley, Supervisor, Licensing
i Fairbanks Morse abC. Ankrum, Manager, Analytical Engineering-ab. Bilex, Service Representative.
G E. Greene, Manager, Customer. Services E. Weisshaar, Service Representative A. Wickman, Service Representative t Failure Analysis' Associates abL. Swanger, Managing Engineer
Franklin Research Center ,V. Bacanskas, Senior Engineer, Nuclear Engineering ' L. Leonard, Principal Scientist, Rolling Bearings,
i Gears, and Failure Analysis Section aH. Ripple, FRC Fellow, Fluid Film Bearings, Seals and Rotor Dynamics Section <
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Engineered Applications Corporation ' a l P. Louzecky, Engineering and Design Consultant-
Duane Arnold Energy Center
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R. Hannen, Assistant Plant Superintendent - Operations l B. Lacy, Maintenance Superintendent-R. McCraker, QC Supervisor D. Mineck, Plant Manager i ~Y. Anagnostopoulos, Maintenance Engineering Supervisor ! J. Smith,-. Technical Support Supervisor l W. Seely, Mechanical Maintenance Foreman i
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Prairie Island Nucl_ ear _ Plan _t D. Buernman, Lead Machinist W. Hadeka, QC Inspector M. Jablonske, Production Engineer G. Lenertz, Superintendent Maintenance G. Miller, Superintendent Operations Engineering J. Nelson, Fonner_ Superintendent Maintenance (Retired) E. Watzl, Plant Manager A. Pietrowski, Fairbanks Morse Service Representative The following NRC personnel also attended the January 24, and/or February 14, 1986 meeting.
a_ P. Byron, Senior Resident Inspector, Fermi 2 " A. Davis, Deputy Administrator, Region III abW. Guldemond, Section Chief, OPS:DRS a. Keppler, Administrator, Region III J a. Kudrick, NRR d ab. Notafrancesco, NRR A C. Paperiello, Director, DRS (M. Parker, Resident Inspector, Fenni 2 G. Wright, Section Chief, 2C:DRP aDenotes persons attending the January 24, 1986 meeting at the Fenni 2 site.
bDenotes persons attending the February 14, 1986 meeting at the Region III office.
jDenotespersonsattendingtheFebruary 28, 1986 interim exit interview.
' Denotes persons attending the November 22, 1985 interim exit interview.
Denotes persons attending the June 5, 1986 telephone exit interview.
The inspectors also contacted other licensee personnel including members of the Operations, Quality Assurance and Maintenance departments.
2.
Introduction On November 13, 1985 Emergency Diesel Generator (EDG) No. 13 was manually-tripped during a 24 hour surveillance test when the operator heard unusual noises and felt low frequency vibrations. An initial inspection revealed that the upper crankshaft connecting rod bearing No. 3 had disintegrated and that the No. 3 piston skirt was cracked. During January 1985, EDG's No.11 and 12 had experienced the failure of several upper crankshaft bearings which were attributed to the lack of proper lubrication during eng'ine starts. As a result station procedures were modified to require prelubrication prior to each planned start, and lube oil filter inspections and lube oil analysis were performed at specified intervals in an effort to detect future bearing failures at an early stage (see Inspection Report No. 50-341/85006).
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b As a result of the November 13, 1985 failure the licensee reactivated the Task Force used to investigate the January failures.
The NRC inspection consisted of a review of the licensee's
investigation, a' visual inspection of the failed' components and of additional components at the request of the inspectors, discussions with representatives of the engine manufacturer and other licensee consultants, independent analysis of damaged bearings by NRC consultants, and review of the performance of other Fairbanks Morse engines owned by other licensees (Duane Arnold and Prairie Island Nuclear Stations) within Region III.
3.
Inspection Results a.
November 1985 Bearing Failures i Upon disassembly of EDG No. 13 the following damaged components were noted: Upper crankshaft connecting rod bearing No. 3 (disintegrated) and
main bearings No. 3 and 13, Upper crankshaft No. 3 main and connecting rod journals,
No. 3 cylinder liner and No. 3 piston skirt,
! Lower crankshaft main bearing No. 4.
- Other upper and lower crankshaft main and connecting rod bearings were noted to have been scored by foreign particles some of which remained embedded in the bearing.
It was also noted that the " frosted" appearance, found on some bearing surfaces during the January 1985 inspection, had become rougher.
In addition to the many foreign particles found embedded on the bearing surface or laying on the oil groove, a dark brown foreign substance was found adhered to the surface of some of the bearings.
As a result of these findings the licensee performed an inspection of EDG No. 14, main and connecting rod bearings.
The inspection revealed significant amounts of foreign particles embedded on the surface of the bearings, scoring of the surface of the bearings, and roughness of the " frosted" areas.
In addition, the brown or black ' foreign substance first noticed in EDG No. 13 was found adhered to i several EDG No. 14 bearings.
The upper crankshaft journals also.
l showed several brown staining marks of several inches in length with ' varying widths.
The No. 1 main journal had a definite roughness on its stained surface.
Light grooving was detected on several journal surfaces with No. 12 journal having the more pronounced grooving.
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In response to an NRC request, on December 3, 1985, the licensee i reluctantly opened EDG No. 11 for. inspection.
Significant damage to upper crankshaft main bearings ~Nos. 13,.8 and 5; moderate' damage to Nos. 9 and 6; and light damage to No.'3 was found. The inspection'
of the main journals showed large areas of aluminum transfer on . Nos. 5-and 6; moderate on Nos. 8 and 9; and small on Nos. 3 and 13.
! I As a result of the damage found on EDG No. 11 the licensee inspected EDG No. 12.
No significant damage was found on any of the upper.
j crankshaft bearings.
i The inspector reviewed the operating history of the engines for the period since their last reassembly in February 1985 and determined , i that the damaged engines had experienced < 20% of the number of ! starts, < 3% of the number of dry starts, and < 50% of the number j. of operating hours than were experienced prior to the failures of January 1985.
A summary of.the engines' operating history is given t t on Table 1.
L A review of the analysis performed on the monthly lube oil samples and the quarterly filter inspection showed that both failed to
, predict the impending failures experienced in' November 1985.
No- ) adverse trends in any of the parameters' measured (aluminum, iron, i tin, pH, viscosity, etc.) could be found.
A summary of the results is shown on Table 2.
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' In summary, damaged bearings were found in EDG Nos. 11 and 13. Other observations noted were: , i (1) the " dirtiest" bearings and journals were found on EDG Nos. 13 j and 14.
(2) the " frosted" appearance on the bearing surface was more i predominant on EDG No. 14 than 13, and least on 11 and 12.
l The roughness of the frosted areas was most notable on EDG ~ No. 14.
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(3) the operating history in terms of starts, dry starts, running i hours, and ratio of running hours per start was well below that ' experienced prior to the failures of January 1985.
(4) the monthly oil samples and quarterly filter inspections failed.
to predict the bearing failure.
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' - Table No. 1 - Engine Operating Summary Engine No./- l Engine' Starts! . Running l Running' HRS l l ~ Time Period l Total I W/ Manual -l W/0 Manuall Fast l Slow l Time-lPer No. Starts l Prelube Prelube (HRS) Ns. 11 l l l l .l . l l . l Pre Feb 1985-l 305 l 132 l 173 l 300 l 5 l 346 l 1.13 l 2/26 - 11/17/85l
l
l
l 26 l 8 l 125 l 3.68 l.
12/21-26/85 l
l
l
1 0- l 10~ l 20* l 2.00-l No. 12 I l l l l l l . l-Pre Feb 1985, l 205 l
l _152 l 199 l _6 l 292-l' 1.42 l 1/19 - 11/27/85l
l
l
l 27 l 10 l 136 - l 3.68 l 12/16-23/85 l'
-l
l
l-0 l 7 l 137 l _19.57-l No. 13 l l l l l l l 'l' Pre Feb 1985 l 159 l
l 134 l 150 l 9 l 214 l 1.35 l 2/5 - 11/13/85 l
l
l
l 23 l 6 l
.l 3.21-l 12/7-25/85
49 l
l
l 3_ l 46 l 223 l 4.55 l No. 14 l l l l l l l " Pre Feb 1985 l 175 l
l 145 l 171-l 4 l 270 l 1.54 L 2/5 - 11/16/85 l
l
l
l 22 l 7 l 117
4.03 l 12/7-14/85 l
l
1
1 0 l 8 l 250 l 31.25 l l l l l l l l l QExcept for upper main bearing.No. 6 which was replaced after six starts and 18 hrs - 41 min of operation.
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Table 2 - Lube Oil Sample Results , EDG No./ l Viscosity l Iron l Aluminum l Tin l Date CST @ 40C wt ops wt ope wt ope EDG No. 11 l l l l l 4/10 l 181
5.3 l 1. 5 ' l < 0.5 l L 5/17 l 179 l 3.4 ,i 1.5 l < 0.5 l ' 6/3 l 175 l _ 2. 4 l .0.8 l < 0.5 l j 6/28* l 189-l 11.0 l < 0.5 l < 0.5 l l 7/29 l 184
6.6 l 0.9 l < 0.5 l 8/26 l 175 l 1. 2 l 0.7 l < 0.5. l-9/23 l 177 l 1.3 l 0.9 l < 0.5 l.
- 10/26 l 179 l 2.2 l 2.0 l < 0.5
4 ' 12/4 l 178
3.5 l 1.0 I _< 0.5 l , 12/23 l 179 l 2.9 l 1.1 l < 0.5 l l l l l l l l l l l
- l EDG No. 13 l
l l-l l' 4/4 l 190 l 0.9 l 1. 0 l < 0.5 l , l 4/27 l 188 l 2.5 l 0.7 l < 0.5 l 5/16 l 188 l 1.7 l 1. 0 l < 0.5 l ' 6/12 l 188 l 6.7 l < 0.5 l < 0.5
7/10 l 188 l 6.3 l < 0.5 l < 0.5-l 8/6 l 184 l l l < 0.5 l --- ---
9/3 l 188 l 1.5 l 2.0 l < 0.5 l 10/1 l 185 l 1.7 l 1.4 l < 0.5 l 10/28 l 181 l 2.0 l 0.7 l < 0.5 i 11/7 l 173 l 0.9 l 0.8 l < 0.5 l , 11/13 l 192 l 4.9 l 1.1 l < 0.5' l
- Licensee suspects sample contamination.
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Cause of November:1985 Failures i-The licensee had no explanation for the condition of EDG No.- 11 bearings.
In the case of EDG No. 13 the licensee has stated that the failure of the No. 3 main bearing-was caused by the failure of I the No. 3 connecting rod bearing which in turn was caused by incorrect reassembly in January 1985. The licensee bases his , conclusion on the finding that fretting had occurred in the surface '. where the bearing cap meets the connecting rod and the fact that one-connecting rod bolt nut had a " low" breakaway tor _que. The licensee failed to consider the fact that: (1) other connecting rod bearing caps were found with as low 'or - ) lower breakaway torque readings as that of No. 3 on EDG No. 13 without experiencing damage, . (2) breakaway torque readings are not an accurate measurement of actual torque values at the time of assembly,- ' l\\ . l (3) the fretting could have occurred after the bearing had failed ! while the engine was being shutdown,
] (4) several QA/QC program controls used to ensure proper engine reassembly would have had to fai1 simultaneously. Such a ' j breakdown, while possible, has not been demonstrated.
If a l misassembly actually occurred, the licensee must identify where l the breakdown in controls occurred and take the necessary steps to prevent this recurrence.
l In the March 18, 1986 report the licensee modified their' earlier i position. THe report states that the root cause of the connecting ! rod bearing No. 3 could not be-determined conclusively from an i inspection of the failed components.
l j c.
Independent Analyses i In an effort to better. understand the cause(s) of bearing failures, j and the " frosting" appearance noted on some of the bearings, the
inspectors obtained several bearings frcm EDG Nos.11 and 13; and samples of the lapping compound (Timesaver 111), " bearing ' j conditioner," and new lube oil (Shell Caprinus R40). The samples were taken to Franklin Research Center-(FRC) in Philadelphia, PA for ! analysis. The results are presented in Attachment A.
In summary FRC concluded that:
) (1) The " frosted" surface appearance on bearings from EDG No.13 i was the result of particulates having impacted or indented the l surface. Based upon their sizes, shapes, and composition, the-particulates had originated in a lapping compound that was used i , to polish the journal and which also was included in a break-in l lubricant used when reinstalling the bearings.
. l (2) Staining on the outer diameter surfaces of EDG No.13 bearings-- i did not appear to indicate an. improper seating of the bearings
in the mounting blocks.
! 8-i , _, - -. ..r..--_,- --.,, - .- ~,,. ~, - n# -n . ,..m.- .- -,.,,, _. - - .,,,,.7_-- .sm, .,--r ,y ,_.--^v %--,,9 - 4.,,--- - -
(3) Scoring damage on EDG No. 11 bearings was the result of sliding induced fatigue, which, in turn, was caused by inadequate clearance (i.e., improper alignment)~ and/or insufficient lubricant film.' Surface flow was further evidence of high contact load between the journal and the bearing.
(4) Staining on the inner diameter surface of an EDG No. 11 main bearing indicates there may have been contamination or dilution of the lubricants.
Such dilution could have been a significant factor in the failure to maintain an adequate lubricant film between the bearing and the journal.
(5) The bearing material, microstructure, and hardness were-characteristic of a standard cast aluminum sleeve bearing alloy.
Defective or substandard material did not play a role 'i in bearing-failures.
(6) A sample of lubricating oil met the manufacturer's viscosity i specifications, b'at water and iron (most likely metallic iron or iron oxide particulates) were excessive.
It is not known whether this is characteristic of the bulk source or if the oil sample had been mishandled.
d.
December 1985 Bearing Failures Following the problems experienced in November and early December 1985, the licensee replaced the following components during the reassembly of all four EDGs: (1) EDG No. 11 - Lower crankshaft main bearings No. 1 and 13, connecting rod bearing No. 4, and all upper crankshaft main bearings.
(2) EDG No. 12 - Lower crankshaft main bearing Nos. 1, 3, 5, 6 and , 13, upper crankshaft main bearing Nos. 5, 6, 13 and 14, and connecting rod bearing No. 3.
(3) EDG No. 13 -. Lower crankshaft main bearing Nos. 2, 4, 5, 6, 7, 8, 10, and 13, connecting rod bearing No. 3, upper crankshaft, and all upper crankshaft main and connecting rod bearings, No. 3 liner, and upper piston and connecting rod.
(4) EDG No. 14 - Lower crankshaft connecting rod bearings No. 2 and 6, and all upper crankshaft main and connecting. rod bearings.
After reassembly, the break-in runs for the EDGs were expanded in accordance with the vendor recommendations and a licensee program to demonstrate that slow starting the engines would not cause distressed D bearings was performed.
The demonstration program consisted of: 100-hour run, after the 40-hour maintenance run-in was completed
35 slow starts,.with at least a one-hour run per start, and
sufficient time between runs to permit the oil to cool below 150F Gap check of upper bearings
One additional slow start to verify engine integrity after the
gap check was completed Three (3) fast starts, with at least one-hour run per start
Gap check of upper bearings
Physical inspection of main bearings
Test runs per vendor's procedures, following bearing inspections
The final number and type of starts and the hours of operation accumulated pri'r to bearing inspectinn are shown on Table 1.
It should be noted that, except for the three fast starts at the end of the program, all other starts were slow because the vendor had stated that fast starts were a significant contributor to the experienced bearing damage.
The results of the demonstration program were as follows: (1) EDG No. 11 - Upper crankshaft main bearing No. 6 failed after 18.5 hours during the break-in run and was replaced.
No. 5 main bearing failed after an additional 1.5 hours of operation.
At this point all bearings were inspected and severe distress was noted on bearing Nos. 3 and 13.
(2) EDG No. 13 - Severe distress was found on upper crankshaft main bearing Nos. 4, 7 and 13.
I e.
Cause of Late December 1985 Failures The licensee stated that probable causes of the bearing failures were: (1) an undesirable alignment pattern with EDG No. 11 upper main bearing caps.
The licensee felt that the November 1985 failures on EDG No. 11 were also caused by this problem.
According to the licensee, while the upper crankshaft bore mandrel alignment had always been within vendor specifications during engine reassembly, the vendor had just informed them that the variations between adjacent bearings showed an undesirable "saw tooth" pattern.
(2) foreign material in EDG No. 13 lube oil system downstream of the five micron filter.
While significant evidence of dirt has been noted on the bearings of all four EDGs in the past, the
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.. . _.. .. _ _ ... _ - -! . d licensee had never felt compelled to take action to correct'the '
problem.
All_ of the foreign material _ noted in the January 1985 inspection, and probably most of-that still being found in the- < latest bearing inspections, was introduced in the system during manufacture, the long storage period at the site, or during the.
- modification to the lube oil system performed in 1982 and 1983.
At this time the licensee was requested to formally submit a program
to the-NRC. explaining the cause(s) of the repeated bearing failures,
the actions planned to correct the problem, and the testing planned-to demonstrate the reliability of the engine.
' f.
Corrective Actions Taken i At meetings on January 24 and February 9,1986, the licensee presented - their conclusions on the causes of the bearing failures,' their planned I corrective. actions; and the demonstration test program to be performed i to restore confidence in the Fermi 2 diesels.
Following several , telephone discussions with the licensee and the NRC, the licensee , , submitted the final program on March 18, 1986.
In general the program consisted of correcting the undesirable bearing cap alignment on EDG No. 11, an extensive flush of the.
lube oil system of EDG Nos. 11 and 13, and replacing the lube oil ! previously used with a new brand, Mobilgard 450.
Following l
reassembly each engine was subjected to the bearing break-in test I as well as the most recent vendor recommendation of a 100-hour l run, under load, for bearing " seasoning." The demonstration test
program performed on EDG Nos.11 and 13 consisted, as a minimum, of: j j (1) Gap check on the upper crankshaft' main bearings, at the l completion of the " seasoning" run, using a 0.002" feeler.
- gauge between the bearing and the bearing saddle, per the i; manufacturer's recommendation.
(2) Twenty (20) prelubed " slow" starts; after each' slow start the i EDG was run under load for a minimum of two (2) hours, ! including a one (1) hour at a load of 1500 to 2600 kW.
! b (3) Gap check on the upper crankshaft main bearings using a 0.002"
feeler gauge.
i (4) Ten (10) prelubed " fast" starts; after each fast start'the EDG j was run under load for a minimum of two'(2) hours, including l one (1) hour at a load of 2500 to 2600 kW.' ! (5) Gap check on the upper crankshaft main bearings using a 0.002"
feeler gauge.
i i_ (6) A seven (7)-day continuous run with the EDG under a load of l 1500 to 2600 kW.
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. , (7) Gap check on the upper crankshaft main bearing using a 0.002" feeler gauge.
g.
Bearing Inspection After the Demonstration Program After completion of the demonstration test program, selected upper crankshaft bearings were disassembled (loaded half only) for visual examination.
The selected bearings were Nos. 3, 5, 6, 8, 9 and 13 on EDG No.11 and Nos. 3, 4, 7,10 and 13 on EDG No.13.
These bearings had experienced the following history of engine starts and hours of operation: Bearing No.
Prelubed Starts Dry Starts Operating Hrs.
Fast Slow EDG No. 11 3, 5, 6, 13
30
416 8 and 9
40
436 EDG No. 13 3, 4, 7, 13
30
504 ,
13
0 727 All bearings passed the 0.002" gap check.
The visual inspection showed all bearings, except No. 13 on both engines, to be in good ' condition.
A light grey area surrounding the wear pattern was noted.
This condition has been experienced before and is explained in the Franklin Research Center report (Attachment A).
The fact that it was " light" in nature could be attributed to the effectiveness of , the lube oil flushing operation.
Bearing No. 13 on EDG No. 11 showed a slight amount of surface scoring, however no aluminum transfer to the journal surface had occurred.
Bearing No. 13 on EDG No. 13 showed slight surface scoring and a small pitted area on the rear face next to the oil' groove.
In addition, aluminum transfer to the journal had occurred on the rear face forming a band approximately 1/2 inch wide next to the oil groove area.
The aluminum covering on the journal appeared to be thin and smooth.
The licensee removed the aluminum from the journal and the same bearing was reused.
It should be noted that the beneficial effects of the lube oil
system flush were evident during this inspection.
For the first time no foreign material was found in the oil groove or embedded in any of the 11 bearings inspected.
, Following the visual inspection the engines were reassembled and the bearing break-in procedure reperformed which included a minimum of 100-hours at * 2600kW for bearing " seasoning."
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Other Problems / Concerns Experienced Since January 1986 During the January-February 1986 period the licensee experienced: (1) Foaming of the Shell Caprinus U 40 lube oil in EDG No. 11 prior to the change to Mobilgard 450. The unit operated for * 42 hours at various speeds and load conditions before the oil was changed.
(2) One lube oil low pressure trip on EDG No. 11 due to a slow start with too low of an engine speed for the existing oil condition.
The procedure was modified in order to increase the initial engine speed during slow starts.
(3) A fire on EDG No. 13 exhaust lagging, apparently caused by oil which had been spilled during the oil flush operation, did some minor damage which was repaired.
(4) A cap screw from'one of the inspection covers on EDG No. 13 was dropped. The licensee was unable to locate the missing cap screw inside or outside of the engine.
(5) A piece of a piston oil ring segment was found in EDG No. 12 near the No. 10 cylinder during a gap check. All 12 upper pistons were inspected and no defective oil rings were found.
It could not be determined how and when the piece was introduced in the engine.
(6) The lube oil viscosity in EDG Nos. 12 and 14 was noted to be decreasing during runs in December 1985.
Following the oil change to Mobilgard the lube oil viscosity in EDG No. 14 remained normal.
Prior to the change to the Mobil lube oil on EDG No. 12 the licensee replaced the mechanical seal of the engine driven fuel oil pump.
In addition, all 24 fuel injector nozzles and 24 fuel injector pumps tested negative for fuel leaks.
During subsequent runs the viscosity decreased initially from 144 to 137 centistokes at 40*C.
It has since held steadily a * 137 which is well within the minimum acceptable value of 130 centistokes at 40'C.
(7) At the January 24, 1986 meeting a member of the public, a former millwright at the station during the installation of the diesel engines, expressed the theory that the bearing problems being experienced were being caused by the methods used to align the engine skid to the foundation.
According to the individual the shims used to mount EDG Nos. 13 and 14 had been optically aligned to ensure a level foundation while those used on EDG Nos. 11 and 12 had not been.
As a result of discussions with the licensee, the vendor, and the NRC consultants, the inspectors have determined that the bearing failures experienced have no connection with the methods used to align the engine skids during initial installation.
In addition, bearing failures have occurred in engines installed by either of the two different methods stated to have been used.
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. i.
Long Term Inspection Program The licensee has proposed the following program to monitor future bearing performance: (1) to perform a special visual-inspection of bearing No. 13 on EDG No. 13 at the next 18-month Technical' Specification surveillance inspection.
(2) to gap check all upper and lower crankshaft main bearings every six months and following three non-manually prelubed (dry) starts.
(3) continue the monthly oil sample analysis.
I No violations or deviations were identified.
4.
Review of Other Licensee's Experience with Similar Diesels Throughout the repeated bearing failures at Fermi, the NRC has questioned the licensee regarding the experiences of other licensees owning the same l vendor diesels, as well as the changing positions the vendor has been promulgating with each passing failure.
For example, the vendor's manual and Service Information Letters only require that new bearings be broken-in by test runs at increasing speed and load which encompasses approximately ten engine starts and approximately ten hours of operation.
As additional failures were experienced a 40 hour break-in run at approximately rated load was added, and finally an additional 100 hour " seasoning" run at * rated load was also added.
The licensee and vendor also have continually blamed fast starts for some of the bearing problems.
Visits were made to the two licensees (Prairie Island and Duane Arnold)
i within Region III who own Fairbanks Morse diesel generators to review their operating and maintenance history, and in the case of Prairie Island, to examine the condition of the bearings on one diesei being disassembled for cylinder liner replacement.
a.
Duane Arnold (DAEC) Experience The two emergency diesel generators at the DAEC are Fairbanks Morse Model No. 3800TD 8-1/8 which is the same model as those at Fermi 2.
The only significant difference between the units at the two sites is that the DAEC diesels' lower crankshaft helps support the generator (one bearing generator) while those at Fermi 2 do not (generator has bearings at both ends).
The operating history of the two emergency diesels, for the last six years, is shown in Table 3.
The summary shows that for the last six
years all starts (over 220 per diesel) have been fast, prelubricated, except for the few auto starts which are fast, dry, starts.
The only
slow starts experienced have been in conjunction with break-in tests run by the vendor representatives.
There have been very few of these and they are not well documented.
In addition the number of fast starts exceeds the number of running hours which is contrary to what the vendor has stated is necessary to improve bearing performance.
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The bearing failure history at DAEC has been good with the exception of bearing Nos. 12, 13 and 14 on the lower crankshaft.
The upper crankshaft bearings have never been disassembled, as a result, although the bearings have never failed a gap check their condition is unknown.
NRC review showed that the licensee experienced failures-of the lower crankshaft bearing No.13 of diesels 1G-31 in 1977,1978, 1980 and 1981; and for diesel 1G-21 in 1980.
Bearing No. 12 failed in diesel IG-31 in 1981, and for diesel 1G-21 in 1980.
Bearing No. 14 failed in diesel 1G-21 in 1981.
The failed bearings were not available for inspector examination. The failures have been attributed to several causes such as generator misalignment, low oil sump level, etc., however, it should be noted that Prairie Island has experienced thrust bearing (No. 13) failures for apparently different reasons.
From the record review and discussion with knowledgeable licensee
personnel it was determined that DAEC has not used " bearing condi-tioner," and has not performed break-in runs or " seasoning" runs, during or following the reassembly of the engine with new or existing bearings.
According to the licensee the only break-ins performed (under the direction of the vendor representatives) , covered a few starts and less than six hours of running time.
Table No. 3 - Duane Arnold Diesel Generators Operating History Engine No./ l Engine Starts Running l Year l Total l W/Manuall W/0 Manuall Fast l Slow l Time l i Prelube Prelube (HRS) ' Diesel (1G-31) 1985 l
l
l
l 29 l
l
l 1984 l
l
l
l 54 l 1* l
l 1983 l
l
l
l 46 l
l
l . 1982 l
l
l
l 44 l
l
1 1981 l
l
l
l 30 l
l
l 1980 l
l
l
l 28 l
l
l l l l l l l l ' I l l l l l l Diesel (1G-21) l l l l l l l 1985
33 l
l
l
l
l
l 1984 l
l
l
l 46 l
l
l 1983
33 l
l
l
1
l
l 1982 l
l
l
l
l
l
l 1981 l
1
l
l
l
l
l 1980 l
l
l
l 31 l
l
l
- 0ne of the three dry starts
,
- - - - - - -
.. ... -. ... - - - . .. -. - J
r , . b.
Prairie Island Experience ~ - Prairie Island (PI) has two' diesel generators of the same vendor and model as Fermi 2.
The main' difference between the units.at the two sites is that PI diesels' lube oil system has not been modified to , continuously prelubricate the lower crankshaft.
The licensee is , . presently evaluating the vendor's proposal to modify the lube oil i J system.
The operating history of the two PI emergency diesels, for the last ! six years, is shown in Table 4.
The table also summarizes the , , l period between bear _ing inspections / replacement for diesel No. 2 (02).
' The review of licensee documents showed that with the exception of < ] engine starts following the annual preventive maintenance inspection, '
or following bearing disassembly / replacement,.all_ starts have been fast, prelubricated. The.only dry starts experienced by these , diesels have been unplanned auto starts.
i Table No. 4 - Prairie Island. Diesel Generators Operating History Engine No./ l Engine Starts Runing l
Year l Total l W/Manuall W/0 Manuall Fast l Slow l Time l Prelube Prelube (HRS) i '
1985 l
l
l
l 47 l 15 l 101 l ' 1984
48 l
l
l 46 l
l
l
1983 l
l
l
l 45 l
l
-l ' 1982 l
l
l
l 44 l
l
l 1981 l
l
l
l 39 l
l
l
1980 l
l
l
l 54 l
l 113 l l l l l
l l ' I l l l l
l , j D2 l l l l l l l j 1985 l
l
l
1
l
l
l j 1984 l
l
1
l 42 l 2-l .67 l l 1983 l
l
l
l 46 l
l
l 1982
40 l
l
l 38 l
l
l , 1981 l
l
l
l 43 l
1
l 1980 l
l
l
1
l
l 649 l l l l l l
-l t 1/28/80 - 4/21/861 278 l 254 l
l 265 l 13 l 494 l l l l l l l
4/1/85 - 4/21/86 l
l
l
1 48 l
l 77-l j i i
i !
! .- -. _- - -. _ - -. -. . -. .. - - - - -. -
InlateDecember1979 emergency /dieselD2trippedduetohigh crankcase pressure being caused'by water in the lube oil as a result of a lube oil cooler leak. During the investigation and repair of the oil cooler in late January 1980, the licensee found that the thrust bearings (No. 13) for each crankshaft had been damaged. New thrust bearings were installed. All other bearings inspected (all upper crankshaft main and connecting rod, plus lower crankshaft connecting rod bearing No. 5 and 10) were found undamaged. The recently completed replacement of all cylinder liners provided the opportunity to inspect several D2 bearings and compare the findings with the known history of engir.e starts and running hours since the January 1980 inspection.
The inspector witnessed the engine disassembly and noted that: (1) lower crankshaft bearing No.13 failed the 0.002" gap check. All other bearings passed the gap check. Visual inspection showed the bearings to be severely distressed and it was replaced. A gap check of the bearing during the April 1, 1985 annual inspection was satisfactory.
(2) upper crankshaft bearing No.13 had experienced moderate to severe distress and was replaced.
(3) considering the degree of damage experienced by both (upper and lower) No.13 main bearings, there was very little aluminum transfer to their journal surface (none on the upper crankshaft and only a few streaks on the lower crankshaft).
(4) light grooving was noted on several of the lower crankshaft connecting rod bearings. The licensee choose to replace bearing Nos. 1, 4, 7, 10 and 12.
(5) the oil (Mobilgard) on the upper crankshaft area was found to be free of particulate matter which could be felt by touch. The bearings and oil grooves were noted to be free of dirt particles although a few embedded particles were noted in some of the bearings.
(6) five pistons (Nos. 2, 3, 8 and 11 upper and No. 8 lower) were replaced due to pitting on the piston head. The severity of the damage varied between the pistons.
The damage to the D2 bearings, found during its recent disassembly, took place within a six year period which included eleven automatic (dry) starts. A satisfactory gap check of the D2 lower crankshaft bearing No. 13 after nine dry starts was recorded. Two additional dry starts caused the bearing to fail the gap check.
- - - -
._ . A review of D1 records showed that'the engine's upper crankshaft was removed during July 1985 for the purpose of replacing cylinder liners No. 11 and 12.
The other liners (1 thru 10) were replaced during October 1985. At the time of the upper crankshaft removal (July 1985) the licensee replaced connecting rod bearing Nos. 1 and 9 and main bearing No. 9 and 13.
Because of excessive axial clearance lower crankshaft No. 13 bearing was also replaced.
The inspector examined the D1 bearings and noted that the lower crank-shaft No. 13 main bearing had experienced severe distress while the upper crankshaft Nos. 9 and 13 main bearings had experience light to moderate distress. The operating history of the D1 bearings could not be determined within the inspection time available.
From the record review and discussions with knowledgeable licensee ' personnel it was determined that at PI the break-in runs, following i the reassembly of an engine with new or previously removed bearings have not always been in accordance with the vendor's recommendations, and like at DAEC, were never as extensive as those promulgated by the vendor at Fermi 2.
It should also be noted that at PI the ratio of hours of operation to the number of starts, although not less than 1.0 like at DAEC, is, however, smaller than the Fermi 2 ratio, which the vendor considered inadequate, c.
Summary i The Duane Arnold and Prairie Island emergency diesel generators have . experienced severe distress on their thrust bearings (No. 13), more pronounced on the lower crankshaft than on the upper crankshaft.
At Prairie Island this condition should improve when the lube oil system of each diesel is modified to continuously maintain the lower , ' crankshaft lubricated.
Neither site has experienced catastrophic bearing failures like those at Fermi 2.
In addition, neither site has employed the bearing conditioner, the 40-hour break-in run, or the 100-hour seasoning run, advocated by the diesel vendor at Fermi 2, following the reassembly of an engine with new bearings.
The ratio of hours of operation to the number of starts for both sites is also less than the Fermi 2 ratio which was considered by
the diesel manufacturer as being too low.
No violations or deviations were identified.
5.
Summary The licensee identified several factors which could have contributed to l the EDG bearing failures, however the root cause(s) could not be ' positively identified.
Several contributors, in different combinations, probably caused the different bearing failures experienced.
. i
- - -
While fast starts and inadequate bearing break-in or " seasoning" have been identified as possible contributors to the bearing failures experience at other nuclear plants has ruled them out.
Since these engines were. designed to run continuously under load, a 100 hour bearing " seasoning" run while not detrimental will not, by itself, prevent bearing degradation.
Neither will slow starts. The most probable contributors to the bearing failures experienced are dry starts and. bearing cap misalignment.
Analysis of monthly lube oil samples, while beneficial to ensure the quality of the lubricant, can not be used to detect incipient failure of , aluminum bearings.
A review of the operating and maintenance history of similar engines at two other nuclear plants, in addition to the Fermi 2 experience, appears - to indicate that the No. 13 (thrust) main bearings constitute a generic design weakness in the application of these engines as standby power sources.
The gap check as an indicator of a distressed bearing is flawed.
Failure to pass the gap check is only an indication that a bearing has been severely overheated.
Experience at Fermi 2 and Prairie Island has shown that the gap check has failed to warn of impending bearing failure.
The NRC has no data base to conclude that engines with severely distressed bearings which pass a gap check are capable of performing their safety function for an extended period of time.
6.
Exit Interviews The inspectors met with licensee representatives (denoted in Paragraph 1) throughout the inspection period.
In addition NRC Management meetings with the Detroit Edison Company were held on January 24, 1986 at the site and February 14, 1986 at the Region III Office.
At each meeting the NRC discussed the latest findings of our inspection and the licensee presented their findings and proposed corrective actions.
At the conclusion'of the inspection on June 5, 1986, the inspectors summarized the results of the inspection to the licensee via telephone.
The inspector also discussed the likely informational content of the inspection report with regards to documents reviewed by the inspector during the inspection.
The licensee did not identify any such documents as proprietary.
____ o ATTACHMENT A , p
9 FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN TECHNICAL REPORT . l ! l- , I* l . I
20fH & RACE STREETS PHILADELPHIA. PA 19103 TWX 710 670L1889 TEL (216)4481000 (- - j i ~fy [ s_. //iI . ) ' l / ) ~,l, J j.
~ , NAR 131998
l ' . i EVALUATIONS OF BEARING FAILURES IN FAIRBANKS-MORSE DIESEL ENGINES , , ' AT THE ENRICO FERMI UNIT 2 REACTOR . FRC Project 5896-012 USNRC Contract NRC-05-83-216 Task TAM-212 Prepared for Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 . NRC Project Officer: P. Cortland FRC Engineers: L. Leonard and H. C. Rippel February 28, 1986 , . Prepared by: Reviewed b : Approved by: ab Da k $fh e:=? Piliic p3 Author 'oopertmen%Iredor ' oste:A/>?/#4 1h785 oste 2 - n - F & oste: PRANKUN RESEARCH CENTER DIVISION OF ARVM/CALSMN seen a saca svearn sumasswena.pa mes -. -. .. . _.. - . _ _ _ _... - _... ,- . - -..- _ , , _ _ _ _,. .. - -... - - .
F-5896-012 CONTENTS Section Title Pag
INTRODUCTION
. . . . . . . . . . . . .
ANALYSES AND DISCUSSION.
. . . . . . . . . . 2.1 BEARING SURFACE ANALYSES
. . . . . . . . . 2.2 BEARING MATERIAL
. . . . . . . . . . . , 2.3 LAPPING COMPOUND AND BREAK-IN LUBRICANT
. . . . . 2.4 LUBRICATING OIL a . . . . . . . . . . . f
CONCLUSIONS ON FAILURE ANALYSES.
. . . . . . . .
SUMMARY OF MEETING AT MONROE, MICHIGAN, 1/24/86, AND FR0 CONCLUSIONS AND RECOMMENDATIONS.
. . . . . . . APPENDIX A OIL ANALYSIS REPORT APPENDIX B OIL SPECIFICATION DATA
1
I
iii < -. _ _. .-.
F-5896-012 1.
INTRODUCTION At the request of the Nuclear Regulatory Commission (NRC), Franklin Research Center (FRC) has conducted a study of factors contributing to bearing failures that occurred during qualification tests of Fairbanks-Morse diesel engines at the Detroit Edison Company (DECO) Enrico Fermi Unit 2.
Damaged bearings, samples of lubricating oil, lapping compound, and break-in lubricant were evaluated, using scanning electron microscopy, metallography, chemical analyses, and hardness testing.
FRC also attended a meeting held at DECO's Monroe, Michigan, site on January 24, 1986. At this meeting, there were presentations and discussions concerning the bearing failures and ways to mitigate them. A sumnary of this information and FRC's conclusions and recommendations relative to the meeting are contained in Section 4 of this report.
-1-
_ __ _ _ __ _ _ _ _ F-5096-012
2.
ANALYSES AND DISCUSSION 2.1 BEARING SURFACE ANALYSES 2.1.1 " Frosted" or Dull Surfaces
l , The upper main No. 5 and crank,No. 5 bearings from Engine 13 were submitted for analysis. The bearings, which were removed from the engine
following a series of start-up tests, exhibited dull, roughened, " frosted" surfaces at several locations around each bearing. Examples of this condition are shown in Figures 1 and 2.
The distribution of this surface damage rela-tive to the orientation of the bearings and the direction of shaft rotation (as reported to FRC by NRC personnel) is sketched in Figure 3.
Since the damage did not correlate with the location of the maximum loading, it appeared that erosion, corrosion, or cavitation mechanisms could have been the cause.
In addition, material separated from the affected surface could then have adhered to either the shaft or the bearing, thus accounting for the scoring of the surfaces and the adherence of particles shown in Figure 1.
To more clearly define the nature of the surface alteration, samples from various locations with different types and levels of damage were studied in the SEM. As shown in the series of mier graphs in Figure 4 through 8, the dull visual appearance of a frosted surface resulted from the highly irregular nature of the surface on a microscopic scale. The less damaged areas had experienced individual dents and subsequent smearing of each dent's raised edges. Repeated multiple denting and smearing occurrences appear to be responsible for the more heavily damaged surface regions at the locations indicated in Figure 3.
J The occurrence of this denting primarily* in the ordinarily non-loaded areas of the bearings can be attributed to three possible mechanisms: (1) the hearing could have made light contact with particulates adhering to the shaft; (1) free particles larger than the gap between the shaft and the bearing could have been drawn onto the gap, thus leaving an imprint; or (3) there could hsve been high velocity impacting of the surface by lubricant borne particulates.
The first possibility appears remote since particulates on the shaft would . , have led to pronounced scoring, particularly in the area of maximum loading, and such was not the case. Furthermore, since the shaft, as would be i-2- - __ __._ -. - _, - - - - - -
. .__.. -_ _ -- - -. _ _ _ - F-5896-012
i expected, was reported to have been significantly harder than the bearing, any particulates would be much more likely to embed in the bearing.
Evidence of angular particulates having plowed into the bearing surface, as seen in Figures 4 and 5, supports the second possibility stated above,
whereas the high density of dents without any embedded particulates lends evidence to the third possibility.
It should also be kept in mind that aluminum bearings are less efficient at catching and embedding particulates than softer babbit bearings. Therefore, the particulates would continue to circulate (if they were smaller than the 5-micron filter in the system) and cause denting. Accordingly, it must be concluded that hard particules had been cirulating with the lubricant. The nature and source of the particulates is described further in Section 2.3.
2.1.2 Bearing Outside Diameter Surfaces
The outside diameter (OD) surfaces of the bearings were also studied to determine if some staining present was an indication of improper mounting.
As shown in Figures 9 and 10, the minor staining correlated with lubricant seepage, whereas the more pronounced patches of deposited material appeared to reflect fretting between the bearings and mounting blocks. Energy dispersive x-ray analysis (EDXA) of the deposited material showed the presence of iron, nickel, and copper. The first elements would be consistent with a steel or iron block, but the source of the copper is not clear. However, at this point, this does not appear to be a critical question since the extent of the deposits and staining does not seem excessive or indicative of improper f mounting of the bearings.
\\ l . 2.1.3 Surface Scoring A second group of bearings from Engine 11 was analyzed to characterize the nature of surface scoring that was noted after a second set of start-up tests. Representative examples of surface deterioration are shown in the macrographs in Figures 11 through 14. The non-uniform scoring wear pattern in Figures 11 and 12 indicates a poor conformity between the shaft and the bearing. At the relatively early stage of bearing surface damage, little-3- - --__ _.
_ . - . , _. .. . . .. . -..
.. . . - . - F-589G-012 aluminum could have transferred to the mating shaft. Therefore, a non-uniform build-up with resultant non-uniform wear appears an unlikely cause for the pattern.
In addition to the non-uniform wear in the load sone, the contact j surfaces exhibited metal flow across the recessed end of the segment and the j outer edge of the bearing's load zone, as shown in Figures 13 and 14. This is evidence of a high degree of contact between the bearing and the journal.
Since inadequate clearance and/or lack of lubrication, especially during " dry" starts, is commonly responsible for the initial bearing wear leading to metal transfer to the shaft, it appears that both of these factors could have played a role in the bearing surface degradation.
Various stages in this surface degradation were documented in scanning electron microscope (SEM) micrographs. In Figure 15, the initial stages of shallow scoring and surface cracking are evident. The small patches of tin in the bearing are randomly distributed and are meant to act as a temporary safeguard lubricant until mating sliding surfaces conform and an oil film is established.
In wear areas of the bearing that appeared very polished on visual examination, the SEM micrographs of Figure 16 show that the tin had flowed and become elongated streaks in the equally flowed aluminum matrix.
This initial flow and polishing represents a " running-in" of the surface and would be stable if an oil film could be maintained to prevent further contact with the shaft.
In areas exhibiting the later stages of surface degradation, it was difficult to observe the tin particles, which could be observed readily in specimens that were damaged to a lesser damage.
The individual scoring defects in the more heavily worn areas exhibited - very smooth surfaces at their bases, as shown in Figures 17 and 18, Since some of these scoring lines had tongues of metal that were in the process of being removed, as in Figures 18 and 19, it appears that the pieces that had been renoved had failed by a fatigue process rather than by a plowing mechanism. That is, a crack had initiated and undermined the surface, and then the mating surfaces repeatedly opened and closed on each other, thus flattening and smoothing the fracture surface, prior to exfoliation. The high localized stress responsible for the narrow strings of surface material i-4- - -- - . - -. - _ _ _ _ _ _ _ \\
. . _. - - _- - - - F-5896-012 removed can be attributed to the presence of bearing metal picked up by the shaft during earlier stages in the failure process.
The fatigue damage and surface flow on the bearings is clear evidence that an adequate lubricant film had not been maintained between the mating sliding surfaces either because of improper clearances, i.e., misalignment between the shaft and the bearings, or insufficient oil, particularly during start-up.
It is significant to note that there was no evidence on the Engine 11 bearings of the frosted type of damage that was on the bearings from Engine 13.
This would indicate that the particulates respensible for the frosting were not present in Engine 11 during the testing sequence.
2.1.4 Inside Diameter Surface Staining One bearing was submitted for the analysis of a large stained patch on the contact surface of the non-loaded half of No. 5 main upper bearing from Engine 11.
It was reported to FRC that this stain was noticed when the residual oil was wiped from the bearing after it was removed from the diesel.
The stain, shown in Figure 20, was found to be superimposed on top of the wear-in lines on the bearing surface, masking these lines to various degrees.
Therefore, it appears that material had deposited on the bearing during the inactive period prior to disassembly and that there may have been some contamination of the lubricant.
EDXA established the presence of traces of sulfur and chlorine in an organic deposit (elements lighter than sodium, i.e, carbon, oxygen, etc., are not detectable by the EDXA technique employed). Since no particulates were detected in the deposit, it is concluded that the deposit in and of itself was not a contributory factor in the scoring or spalling degradation described in previous sections. However, if tLt deposit originated from fuel oil dilution of the lubricant, such dilution could have been a factor in the failure to maintain a lubricant film sufficient to preclude spalling or scoring.
' 2.2 BEARING MATERIAL Tests were conducted to assure that the bearing material and/or hardness was within the specifications for the type of aluminum alloy customarily used in sliding bearing applications.
-5- . . _ ._- ..
._ _ -- .--. . F-5896-012 2.2.1 Chemical Composition of Bearina Material The results of chemical analyses on two main bearing segments (13-5UB and 11-5UT), one crank bearing segment (13-5UT), and the composition of cast aluminum alloy 850.0, which is commonly used in sliding bearings, are as follows: 13-5UB 13-5UT 11-5UT Alloy 850.0 Tin 6.00 5.99 5.95 5.5-7.0 Copper 0.930 1.00 0.925 0.0-1.3 Nickel 0.892 0.925 0.790 0.7-1.3 Iron 0.245 0.524 0.140 0.7 max Magnesium 0.002 0.019 0.007 0.10 Aluminum 91.47 91.23 91.75 Remainder It is clear that the composition of the analyzed bearings meets the chemical specification for aluminum alloy 850.0.
Thus, failure cannot be attributed to substandard alloy composition.
2.2.2 Bearing Microstructure The expected microstructure for cast alloy 850.0 consists of a dendritic distribution of tin particles and accicular NiA1 in an aluminum solid-
, solution matrix. As shown in the examples in Figure 21, the microstructures of the bearings agreed with that normally anticipated, and no evidence of casting deficiences was noted. The differences in interdendritic spacing in the two micrographs in Figure 20 most likely reflect different cooling and
solidification rates.
A cross section cut through a scored or spalled region was prepared to determine if the microstructure, particularly the tin phase, influenced the I cracking path. As shown in Figure 22, there was no indication of such behavior. In addition, the base of the fracture appeared smooth in profile, consistent with the direct views of the scoring or spalling defects shown in . Figures 17 and 18.
l-6- -. .- - - - - _ ..
- - . _ . .- - __ F-5896-012 2.2.3 Hardness The strength level of several bearing samples was determined by measuring the hardness of metallographic samples. The results were as follows: ! Bearing Rockwell H Hardness
13-5UT crank
13-5UB main
11-5UT main 93.5 For an 850.0 alloy, these hardness levels indicate that the material had been subjected to a T101 temper, which entails an aging treatment plus 4%. cold working. An aging treatment alone should have resulted in a hardness of 85 Rockwell H.
The cold working significantly increases the yield strength (nominal compressive yield increases from 10,950 psi to 24,640 according to data in Volume 1 of the Eighth Edition of the ASM Metals Handbook).
Thus, the extruded flow of surface metal pointed out in Figures 13 and 14 ! can be attributed to high loads rather than to the material's yield strength being below its rated value.
2.3 LAPPING COMPOUND AND BREAK-IN LUBRICANT Samples of the lapping compound and the break-in lubricant that had been used in preparing the journal surfaces of the shaft and in the initial fit-up of the shaft in the bearings were analyzed to determined if either could be the source of the particulates found embedded in the surfaces of the Engine 13 bearings discussed in Section 2.1.1.
It was reported to FRC that the break-in ' lubricant, which was a viscous black liquid, contained graphite and lapping compound.
As shown in Figure 23, both the lapping compound and break-in lubricant contained angular particulates whose sises, shapes, and composition (Mg, A1, Si, Cu, and Fe) matched those of the particulates embedded in the Engine 13 bearings. Thus, the lapping c m =d and/or the break-in lubricant can be considered the source of the particulates. In addition to the mineral particulates, the lapping compound contained a much finer powder rich in lead and chromiu'm which did not appear to have contributed to the frosting damage.
-7- - _.
. . . . _ -. _, , _. -. -.
F-5896-012 2.4 LUBRICATING OIL An unused sample of the lubricating oil, Shell Caprinus R 40, was submitted for analyses to determine if its characteristics, in particular its viscosity, met those specified by the supplier of the diesel engine and hence those expected by the operator (i.e., Detroit Edison). The report from Phoenix Chemical Laboratory, which is appended to this report, indicates that the viscosity did indeed meet the viscosity specifications (192.0 cs at 40*C and 14.66 cs at 100'C, converted from data in the specification sheet, a copy of which is also appended to this report). However, both the iron and water content were high, indicating some contamination of the oil prior to receipt by FRC. No such contamination was reported in data from Detroit Edison for samples routinely taken after each shutdown of an engine. Thus, it is not clear whether the initial oil supply was somehow contaminated or if it contributed in any way to the degradation of the bearings in Engine 11.
P-8- _.
.
._. _ F-5896-012 s 3.
CONCLUSIONS ON FAILURE ANALYSES Based on the previous findings, the following conclusions were reached: 1. The " frosted" surface appearance r-n bearings from Engine 13 was the result of particulates having impacted or indented the surface. Based upon their sizes, shapes, and composition, the particulates had originated in a lapping compound that was used to polish the journal and which also was included in a break-in lubricant when assembling the shaft in the bearings.
2. Staining on the outer diameter surfaces of Engine 13 bearings did not appear to indicate an improper seating of the bearings in the mounting blocks.
3. Scoring damage on Engine 11 bearings was the result of sliding induced fatigue, which, in turn, was caused by inadequate clearance (i.e., improper alignment) and/or insufficient lubricant film. Surface flow was further evidence of high contact load between the journal and the bearing.
4. Staining on the inner diameter surface of an Engine 11 main bearing indicates there may have been contamination or dilution of the lubricants. Such dilution could have been a significant factor in the failure to maintain an adequate lubricant film between the bearing and the journal.
5. The bearing material, microstructure, and hardness were characteristic of a standard cast aluminum sleeve bearing alloy. Defective or substandard material did not play a role in bearing failures.
6. A sample of lubricating oil met the manufacturer's viscosity specifications, but water and iron (most likely metallic iron or iron oxide particulates) were excessive. It is not known whether this is characteristic of the bulk source or if the oil sample had been adshandled.
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8% ' Figure 1.
Macrographs showing examples of " frosted" surface damage on an Engine 13-5UB main bearing segment.
In A, some scoring and an adhering particle are also evident.
In B, a small smeared adhering particle is outlined.
l-10-
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Macrograph showing an example of " frosted" surface damage on Engine 13-5UT crank bearing segment. A large adherent metal flake is in the center.
I i-11- . _ __ . - - .. .. ..
A. Main Bearing F-5896-012 Top s' o $< -
l Shaft Rotation Heavy Frosting ' Across Race Frosting Along Central Oil Groove j B. Crank Bearing Top Maximum Frosting Frosting Along Central Oil Groove d - - Shaft Rotation /
Majo Figure 3.
Sketches showing the distribution of surface frosting relative to the loading patterns on the sliding bearings from Engine 13.
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150X , Figure 4.
SEM micrographs showing an area of pronounced frosting on the - 13-5UB main bearing. The surface is very irregular and embedded particulates containing Mg, A1, Si, Ca, and Fe are indicated by arrows in A and are c,1early evident in B.
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Figure 5.
SEM micrographs showing further details of both the frosted surface and embedded particles of Figure 4.
The surface is a mixture of dents and smeared-over material.
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1000X l l i Figure 6.
SEM micrographs showing additional fine details of the heavily ' disturbed frosted surface of Figure 4.
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300X i Figure 7.
SEM micrographs showing surface damage along the central oil groove on the 13-SUT main bearing segraent. The damage is less severe than that in Figures 4 through 6, and individual dents are clearly delineated at the edges of the disturbed band (see also Figure 8).
An embedded particulate is also evident in B.
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1000X ! Figure 8.
SD4 micrographs showing individual dents with smearing of the originally raised edges, in addition to an embedded mineral particulate, on the 13-5UT main bearing segment.
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13-5UT 0.5X Figure 9.
Macrographs of the 13-5 main bearing showing staining on the OD surfaces of the two segments.
In A, the staining appears to reflect lubricant seepage, whereas in B, there are distinct patches j of built-up residue, possibly from fretting.
j , -18- -. _ _ . -- -.- -. .. -. - - - - - - - - - - - - - - - -... - -. -., - - - - - - - - - - - - - - - - . --
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13-5UT Main 9X Macrographs s'owing patches of built up debris on the OD surfaces h Figure 10.
- of segments of 13-5 bearings. The debris appears to reflect that some fretting of the mounting block had occurred.
_ -19-
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. 11-3UT Main IX Figure 11. Macrograph showing the load zone of a main bearing.
There is a non-uniform wear pattern, with scoring at the top and bottom areas j i in'the macrograph (see also Figure 12). The arrow indicates the sliding direction.
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11-3UT 2x Figure 12. Macrographs showing higher magnification views of the top and bottom area of Figure 11.
Note the non-uniform wear pattern and the individual gouge-like markings on the surface. The arrows indicate the sliding direction.
-21- - -. _. _. - -,. _.. - - - - ... -.
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$< , e..., , , t?}'d'br.6V.f;,i[',:;& 11-3W Main 8X . Figure 13. Macrograph showing the top area of the upper macrograph in Figure 12.
In addition to the scoring, the surface experienced plastic flow in the sliding direction across the recess at the segment joint.
-22- .. -... - .. . . ... - -. .. _ _ - -. . - - - - - - - - - -.. - - - -.
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11-SUT Main 8X , , Figure 14. Macrographs showing a bearing with more severe snrface damage than that on the bearing in Figures 11 through 13.
In addition to scoring damage, there is metal flow out across the bearing's edge on the right.
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11-12UT 300X . Figure 16.
SEM micrograp is showing a highly polished surface on which the tin phase has been smeared owing to sliding contact with the shaft.
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SEM micrographs showing the formation of an individual surface defect by the exfoliation, i.e, fatigue spalling, of a surface layer strip.
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The fine powder in the lapping compound had a different composition than the particulates and was rich in lead and chromium.
-32- , _ _ -, _, - _ _ _, _ - _, _ _ _ _ - _ -
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SIMMARY OF MEETING AT MONROE, MICHIGAN,1/24/86 AND FRC RECOMMENDATIONS A meeting was held at DECO's Fermi Unit 2 site at which DECO: its consultant, Dr. Lee Swanger of Failure Analysis Associates (FAA); and Colt Industries, manufacturers of the Fairbanks Morse diesel generators, made presentations.
DECO described the history of the generators including the problems, diagnosed the causes of the problems, and then proposed corrective actions.
DECO concluded tilat the failures to date in the upper bearings can be attributed to a combination of possible factors which include: a.
long-time inactive storage b.
contamination c.
lack of lubrication during rapid starts d.
misalignment e.
lubricant inadequacies.
Dr. Swanger discussed the design of sliding bearings, in general, and presented the results of analytical studies of the loading and lubrication of the upper main and connecting rod bearings in the diesel in question. He concluded that the design and lubrication, i.e., film thickness, were adequate for the application.
Colt basically agreed with the information given by DECO and FAA and stressed their reconsnendation that disassembly inspection be discontinued owing to the Potential for introducing misalignment and contamination into the system. They felt that feeler gauge measurements of the gap between bearing sections was an adequate technique for monitoring bearing condition and reconsnended a wear-in test to " season" the bearings prior to the qualification tests.
. Based upon its own' investigation, the above presentation, and the discus-sions which followed them, FRC offers the following connents and recommenda-tions: -33-i ._ _ _ - --
_- -_ _ _ _ _ _ _ _ _ _ _ - _. _ _ _ _ _ _. _ _ _ ___ - ! F-5896-012 i 1.
There may be some differences of opinion among the investigators as , to the relative importance of each of the above factors as contribu-i ting to the failures. Nevertheless, this should not be of major importance as DECO appears to have addressed all of the various
parameters in its proposed solutions to the bearing problem. It is felt that such steps as flushing the system to remove contaminants,
using accurate alignment procedures, employing manual lubrication ' prior to all starts, using a lubricant which has been demonstrated to be effective in similar engines, and using a " seasoning" or run-in , procedure to eliminate "high spots" on the journal / shaft interfaces will all contribute to a greater reliability of the bearings. How-
ever, since no tests with dry starts are included in the proposed test envelope, there remains a question as to how DECO will handle this issue.
2.
DECO and Colt propose to monitor the state of a bearing by analysis of the oil after each shutdown and by measuring the gap between the halves of each bearing (every 6 months). However, all the experience at Fermi Unit 2 to date has shown that these monitoring steps can only determine if a bearing has experienced a failure. They cannot ! indicate if the bearing is beginning to fail. Analyses of the oil ' after each engine run did not indicate any bearing problem, although heavily damaged bearings were found on disassembly. Accordingly, only by direct observation of the bearings can it be demonstrated unequivocally that all the various steps implemented by DECO have been successful in precluding bearing wear and failures. Thus, it is j recomended that, as a minimum, 50% of the upper main bearings should be visually inspected after removal of the caps.
'
While it is a valid argument that disassembly and reassembly.can alter bearing position (alignment) and/or introduce contaminants, it is felt that the need to verify fully the effectiveness of all the fixes in the initial qualification tests outweighs the possible problems inherent in the evaluation process. If the run-in or " seasoning" process is, indeed, effective in preventing bearing failures, the repeat of such a procedure (although time consuming) could be reemployed following the inspection, providing the bearings are in good condition.
3.
The analytical analyses of engine bearing performance characteristics (performed for Detroit Edison by L. Swanger of FAA) are judged to be i sufficiently rigorous for the intended purpose. The analysis included the necessary ingredients of: , Establishment of " polar loading diagrams" for. each bearing via a i a.
dynamic analysis of the engine hardware operating at rated speed and rated power.
b.
" Journal Orbit Analyses" to establish time varying magnitudes of " peak oil-film pressure" and " minimum oil-film thicknesses" during operation.
i i-34- , ...- - . - - -. - _. - _ _. - - _- . - - . . .. -. -... . _
, F-5896-012 While resulting maximum values of " peak oil-film pressure" are of the order of 80% of the maximum capability of the aluminum-6% tin bearing material (hence satisfactory), minimum values cited for " minimum oil-film thickness" (133 micro-inches) are, in our opinion, somewhat too small in light of the large-size (8-inch-diameter) hardware involved allowing little margin for error with regard to bearing alignments, transient overload, and the like. There are, however, dozens of other identical Fairbanks-Morse diesel engines operating at the same power-speed condi-tions (hence, identical bearing loadings) that, apparently, have not had the degree of bearing failures experienced by the Fermi Unit 2 units.
. -35-
. , APPENDIX A OIL ANALYSIS REPORT , ! l , FRANKUN RESEARCH CENTER OM90N OF ARVIN/ CAL 5 PAN ' 20th & RACE STREETS. PHILADELPHIA.PA 19103 - -. ..-. - -.=--. -.. - . -. - . - .. - -. . -...
ARES CODE C12 TJLEPMoN E 772 - 3577 P1oenix Gemice; Le> ore <ory, loc.
FUEL AND LUBRICANT TECHNOLOGISTS 3953 5HAKESPEARE AVENUE CHICACO. lLL. 60647 December 20, 1985 RECEIVED FROM Franklin Research Center 20th 6 Race Sts.
Philadelphia, PA 19103 SAMPLE OF Oil LABORATORY NO.
5 12 19 27 MARKED Caprinus R 40 Aluminum, ppm 6.1 Iron, ppm 31.1 Chromium, ppm 0.15 Viscosity 9 40*C., cs.
190.4 Viscosity 8 100'C., cs.
14.55 Karl Fischer Water, ppm 1509 ' A. A. Krawetz
I l^ - l l l- { ! APPENDIX B
IOILSPECIFICA j l
. FRANKUN RESEARCH CENTER ' OlVISION OF ARVIN/CALSPAN 20th & RACE STREETS. PHILADELPHIA.PA 19103 . -.. - -.. - - . - -. - -. -. - -. . -.--....- - -... - --. - -. - - - . .. . -.. - - ... -. .
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i SOC:17-80 , (Supersedes SOC 17-77) gh Technical Bulletein - . Wf Shell Oil Company 011. DISTRIBUTORS OF PHII.A., INC.
FORD STREET BRIDGE AND RAMP WEST CONSHOHOCKEN, PA. 19428 PHONE: 215-825-0600 Caprinus* R oil 40 A high basicitylubricating oil especially developed for , extended servicein large medium-speed diesel engines.
Product Description cluded are GE, EMD, ALCO, Fairbanks Morse and other similar diesels.
Caprinus R oil 40 is a highly alkaline engine oil developed to meet the performance requirements Field Test Results of modem medium-speed diesel engines in Extensive field testing of Caprinus R oil 40 railroad, marine and stationary power applica-confirmed its excellent retained alkalinity benefits tions. Its high initial basicity and excellent as well as its outstanding dispersancy. Test en-equilibrated long-term basicity effectively meet gines were remarkably clean and had low wear.
the requirements imposed by higher cylinder Deposits, including those in critical ring belt horsepower, extended drain intervals, reduced oil areas, were at a minimum.
consumption (less make-up oil), and the effect of Now GE 3600 HP U368 locomotives were used high sulfurfuels.
in one test. Operating in high speed passenger / Caprinus R oil 40 has an initial TBN-E of 10.2 freight service, three locomotives pulled about 40 (ASTM D 2896), and usually will equilibrate to a rail cars and auto carriers at an average speed of TBN-E of about 2.0 to 3. Din service. it is available in opproximately 60 mph. Mileage averaged over one viscosity grade,SAE 40.
180,000 miles per engine during the 12-month test The oil has been approved by General Electric period. Engine inspections at the completion of Companyas a Superior Class il" Higher Alkalinity" the test indicated outstanding lubricant perfor-Lebricant. It has been classified in the " Extensive mance. On an engine cleanliness rating (10= use" category by Electro-Motive Division of clean), a typical cylinder was rated at 9.1 using GeneralMotors Corporation.
Caprinus R oil 40, compared to an overall average , of 7.5 for cylinders from an engine in similar Applications service using a competitive Class 11 oil. The entire ' -. Caprinus R oll 40 ls recommended for all medium-engine reflected this cleanliness advantage for speed 2-stroke and 4 stroke diesel engines, in-Caprinus R.
____ ___ _ _ _ _ - _ _ _ __ _ _
_ _ _ _ - ____ . Table I compares the ring belt pertormme of Power assembly wear was minimal, sludge de-Capnnus R with a fully approved oil used at posits were nil. Top compression rings had an av-another railroad unde r slightly different operating erage EMD chrome ring rating of 1.5,and allother conditions.
critical parts such as trunnion bearings, rings and Engine oils were changed at four to six-month grooves, and cylinder liners were within or near intervals (70-100,000 miles). Alkalinity equilibrat-new parts specifications. Silver trunnion bearings y ed at 2.3 TBN-E (D 664) with Caprinus R oil, were in excellent condition.
compared to slightly over 1.0 for the reference oil.
in the EMDs, used oil alkalinity equilibrated at Five new EMD SD45-2 engines were also used 3.0 TBN-E (D 664) afte r about two or three months in a 12-month field test in coal hauling service.
of service. The commercial reference Class 11 oil This service usually involved three locomotives equilibrated at 2.0 TBN-E. There were no oil pulling a 10,000-ton train at about 35 mph average changes during the test period.
speed. Mileage for the period was about 92,000 in EMD power units, Shell recommends a "no miles for each engine. As with the GE units, the scheduled oil drain" service practice when sup-engines had low wear and were remarkably clean piemented with an adequate oil analysis pro-when inspected at the close of the test period.
gram.
Table I/ Piston Ring Belt Performance - GE U36B Engines Commerclat Caprinus R oil 40 Class H Oil Locomotive Type GE U36B. Railroad A GE U36B. Railroad B Mileage 171,790 179.516 114.000 126.000 Paston Ring Groove Filkng. Percent Compression Ring Number 1
16
25 Compression Ring Number 2
25
45 Compression Ring Number 3
5
30 Oil Control Ring
0
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-- -- .. . _.. .q l . Figure 1/ Comparison of Used Oil Alkalinity in OE U368 Engines .'
(10.2 by ASTM D 2896) . - h k E a - T %- g4 % Caprinus R oli 40. Railroad A "hmmmmmmmmmmmmm Commercist Class it Oii Railroad B mmmmm MW ! O
100 150 200 Oil Use. Days
Figure 2/ Comparison of Used Oil Alkalinity in EMD SD45 2 Engines .
(10.2 by ASTM D 2896) ,
r.
a \\ ?' \\ g
Caprinus R off 40 >-
" " " " " " " Class 11 Reference System Oil I O 100 200 300 400
- -
Oil Use. Days - b i Typical Properties of Caprinus R oil 40 L . i Property ASTM Test B8eewd Value - Gravity, ' API D 1298 23.5 Vascosity at 100*F. SUS D 445 1000-105:i Viscosity at 210*F, SUS D 445 77-80 Vascosity Index D 2270 65-69 , Flash Point,'F D 02 475 ' Pour Point. *F D 97
T8N-E D 864 9.4 D 2696 102 ~ TAN-E D 064 0.8 Initet pH D 864 9.5 Sutfated Ash,%w D 874 1.1 1.2 m }}