ML20150F285

Safety Evaluation Supporting Resolution of Tdi Diesel Engine Vibration Problems at Facility

ML20150F285
Person / Time
Site:	Rancho Seco
Issue date:	03/28/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20150F283	List: ML20150F280 ML20150F285
References
TAC-67001, NUDOCS 8804050128
Download: ML20150F285 (6)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RESOLUTION OF TDI DIESEL ENGINE VIBRATION PROBLEMS RANCHO SECO NUCLEAR GENERATING STATION NECHANICAL ENGINEERING BRANCH DIVISION OF ENGINEERING & SYSTEMS TECHNOLOGY

1.0 INTRODUCTION

During pre-operational testing of two newly installed Transamerican Delaval, Inc. (TDI) emergency diesel engine generators (A2 and B2) at Rancho Seco, excessive vibration effects were observed in both units. These effects were significant in several auxiliary piping systems and components in-cluding the turbocharger and air starting system, the exhaust shroud, the jacket water supply system, the lube oil system and the fuel oil system. j These systems were also designed and ir. stalled by TDI. The major effects were characterized by various pipe and support failures, by excessive vibration of the turbochargers and the jacket-water-return-header / exhaust shroud structures, and by high pressure pulses in the lube oil systems. Aftr.r 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of testing operation, SMUD evaluated the test results and concluded that the vibration levels were unacceptable. TDI was contracted to resolve the turbocharger vibration problems, and a third party consultant Duke Engineering and Services, Inc., (DES), was centracted to resolve the general 1 vibration problems with the piping systems. Anotherconsultant(Engineering i

Dynamics, Inc.) was also contracted to assist with the resolution of vibration t

1 problems in the lube oil systems and the return lines of the jacket water l

! supply systems.

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2.0 EVALUATION The root causes of the vibration problems were determined to be the vibration of the engines themselves and the turbochargers. In addition, the rotary gear l pumps in the lube oil systems induced fluid pulsations in this piping, which

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were amplified by their geometry and the location of the control valves. The location and the adjustment of these valves were determined to be of critical importance in reducing the magnitude of the vibration. The combined motion of the engines and the turbochargers induced considerable vibratioa in the jacket water return headers which are attached to the exhaust shrouds; this vibration caused cracking in some of the supports of the return headers and excessive vibration of the shrouds, which were determined to be poorly con-structed and supported. Likewise, turbocharger vibration was attributed to be the cause of broken turbocharger lube oil supply and return lines.

Substantial modifications have been made by TDI and SMUD to reduce this vibration. The vibration of the turbochargers was reduced by installing large strut supports, and other smaller supports. The vibration in the lube oil systems was reduced by modifying the piping geometry, adding pulsation dampers and relocating the control valves. The vibration of the exhaust shrouds and the jacket water return headors was reduced by stiffening the shrouds and the header supports, or by replacement with flexible pipe segments. Similar measures were taken to reduce the vibra-tion in the piping of other systems. However, although these modifica-tions were successful for the "A2" engine, the "B2" engine shroud still l l

experienced cracking and internal leaking. This was attributed to local 1 1

vibration of the shroud plates induced by impact of the exhaust pipes on certain internal shroud diaphragms.

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All piping systems and components on both angines which experienced excessive vibration problems have been reevaluated, modified and retested at 3000 KW.

The "A2" engine was run for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> without any adverse effects, and was found l to satisfy the prescribed vibration acceptance criteria. The "B2" engine has

, also completed a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test run, but cracks were found on some supports and on the shroud. The licensee perfonned an evaluation of these failures and the function of the shroud, and concluded that the "82" engine could operate without the shroud, by applying insulation to the exhaust pipes. The supports of the jacket water return header were modified and attached directly to the engine. The "B2" engine was rerun for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> without adverse effects and found to satisfy all vibration criteria. Several interim reports (Reference 1 and subsequent submittals) were submitted by SMUD to the staff describing the installed modifications, the engineering calculations and a comparison of measured vibration quantities (velocities or displacements) with the corres-ponding acceptance criteria. The licensee demonstrated that the measured vibration levels at the 3000 KW 1evel were within the acceptance criteria envelope. The staff has reviewed these modifications, the supporting cal-culations and the vibration data, and has found that they are in accordance

with current engineering practice and design methodology and are therefore acceptable, j i

l The acceptance criteria for vibration testing acceptability were initially specified by DES. These criteria were reviewed by the staff and found to be less conservative than the vibration criteria b'ased on trethods stated

intheindustrystandardOM-3,1982(Reference 2)andtherefore,unaccep-i table. This standard has recently been revised to produce even more i

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i conservativevibrationcriteria(Reference 3). However, the current criteria (based on OM-3, 1982) have been determined by the staff to be acceptable if continuous surveillance and vibration monitoring of the diesel engines and connected syste is performed during future operation of these er.gines. The tests which ve been performect to demonstrate operability have satisfied this requirement and have therefore been found to be acceptable.

In a letter dated February 1,1988 (Reference 4) the licensee committed to implement a TOI Owners Group maintenance and surveillance program, which includes hourly checks of piping for leaks during diesel engine operation, inspection of various jacket water nozzle welds, measurement of turbocharger -

and diesel engine vibration during 24-hour surveillance runs and subsequent comparison to baseline data. These 24-hour surveillance runs will be per-formed at each refueling interval. The licensee has also stated that a site-wide maintenance program, which monitors the vibrations of major equipment on 90-day intervals and ensures that unanticipated increases in vibration levels are detected in a timely manner, will include the TDI diesel generators. Additionally, the staff requires that during any operation of the diesel engines longer than about 15 minutes, the vibration levels of the piping and components be closely monitored and remain below the established acceptance criteria, and that all piping systems and com-ponents be continuously checked for leaks and cracks.

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5-The licensee has also committed to perform an evaluation of the entire design

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of the TDI diesel piping and auxiliary skid arrangement. This evaluation will  ;

be performed after restart and completed prior to the next refueling outage, l l

to determine if an alternate design is more advantageous. In Reference 5, the l licensee comitted to use Reference 3 as the basis for the acceptance criteria for this evaluation. The staff finds this proposed long term evaluation accep-table.  !

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3.0 CONCLUSION

1 The staff has evaluated the test data and results at 3000 XW submitted by the licensee and finds that the TDI diesel engine vibration levels are within acceptable limits. These engines have also successfully completed 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> operation tests without any significant adverse effects. Based on the fore- l going considerations, including the licensee commitments regarding maintenance and surveillance of the TDI diesels and the auxiliary systems and components, the staff finds the test results to be acceptable for plant restart, subject to the staff requirement stated above regarding surveillance and vibration monitoring during all diesel engine operation, provided the 3000 KW 1evel is not exceeded, j i

I 4.0 REFEPENCES 1

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1. Letter AGM/TA 88-080 from B. G. Croley, SMUD, to F. J. Miraglia, Jr., I l

NRC, dated March 4, 1988, with attachments, i C -

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1 i 3 2. ANSI /ASME DM3-1982, "Requirements for Preoperational and Initial  ;

a l Start-up Vibration Testing of Nuclear Power Plant Piping Systems." l American Society of Mechanical Engineers, New York, NY.

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3. ANSI /ASME OM3-1986, or latest draft. -  !

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4. Letter GCA 88-032 from C. Andognini, SMUD, to F. J. Miraglia, Jr.,

i NRC, dated February 1,1988. -!

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5. Letter GCA 88-193 from C. Andognini, SMUD, to F. J. Miraglia, Jr., l t

NRC, dated March 21, 1988.  ;

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