ML20198T506

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Forwards Preliminary Data from Friction Tests of Aged Stellite 6 Specimens
ML20198T506
Person / Time
Issue date: 11/12/1997
From: Mayfield M
NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To: Wessman R
NRC (Affiliation Not Assigned)
References
NUDOCS 9711170013
Download: ML20198T506 (15)
v • d • e


Text

(

l? lbyster 12,1997 MEMORANDUM TO: Richard H. Wessman, Chief Mechanical Engineering Branch )

Division of Engineering j Office of Nuclear Reactor Regulation l FROM: Michael E. Mayfield, Chief Electrical, Materia!s, and Mechanical Engineering Branch Division of Engineering Technology Office of Nuclear Regulatory Research

SUBJECT:

PRELIMINARY DATA FROM FRICTION TESTS OF AGED STELLITE 6 SPECIMENS The subject data in the attachment is transmitted at the request of members of your staff. The data was collected from aging tests of Stellite 6 specimens subjected to a typical BWR operating environment of temperature, pressure, and water chemistry for various lengths of time. These tests are intended to determine the effects of film buildup, on seating surfaces, and the impact of the film on the performance of typical motor-operated valves. The tests were conducted at the Battelle Institute, Columbus, Ohio.

The data show the effects of environment on (1) development of surface films on the Stellite specimens, (2) magnitudes of friction coefficients due to the formation of the films, and (3) composition of the film through the thickness. The effects of simulated inservice test (IST) strokes on changing the film thicknesses and the friction coefficients are also shown.

Preliminary indications are that the frictio, coefficients continue to increase with film thickness and that the coefficients decrease with subsequent strokes. For the one test point selected, the specimens subjected to prior IST strokes show a lower trend of friction coefficients than those specimens not subjected to prior IST strokes. The tests are continuing and will simulate longer periods of operation. The tests are expected to be completed in CY 1998, if you have any questions on the attachment, please contact Gerald H. Weidenhamer (415-6015) of my staff.

Attachment:

As stated Distribution: Signature File (LCS), Branch Reading File, Document r. ontrol Desk, PDR DOCUMENT NAME: g:\weidenha\ friction.da

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Background i The Idaho National Engineering and Environmental Laboratory (INEEL)is performing research related to

. motor-operated valves (MOVs) to assist the NRC.

The results of this project will provide information to:

Determine how aging can affect the performance of motor-operated valves.

Determine the maximum disc-to-seat friction expected of a fully aged valve.

. Determine the effect periodic valve cycling due to ~

in-service testing has on friction.

An oxide film could affect the operating force during closing and while seating.

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Stellite 6 specimens were aged at simulated BWR l

coolant conditions in a corrosion autoclave. t j

Temperature 550 F Pressure 1050 psi

pH (room temperature) 6.5 to 7.0 Oxygen (ppb) 100 - 200 Conductivity (micro S/cm) < 1.0 Flow velocity (ft/sec) 2.2 to 2.8 I

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Stellite 6 specimens have been aged 4

for 2,10,20,40, and 78 days.

Results show that the surface of the oxide film

is rich in chromium and lean in cobalt. l:

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  • Results show that the oxide film growth rate

! is parabolic.

Results also show that the friction continues i to increase as the specimens age.

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I The growth rate of Stellite 6 oxide film is parabolic.

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0 10 20 30 40 50 60 70 80 Time (d) c,, ,,7 ,

l The maximum friction continues to increase L on Stellite 6 specimens aged for 78 days. i 0.6 x 2 day maximum ,

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+ 20 day maximum 0.5 4 40 day maximum g

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l The maximum friction not only increases as the Stellite 6 i

spacimens age, but also does not appear to reach a plateau.

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We also investigated whether in-service testing affects the oxide film growth characteristics or the resulting friction. -
Stellite 6 specimens were aged for 78 days with in-service test cycles after 25 days and again after 50 days.
  • Results show that the oxide film thickness was affected by the simulated wedging, but the oxide film continues l to grow after the simulated wedging similar to those of

! the undisturbed oxide film.

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Results also show that the in-service test cycle initially reduces the friction, although it is not clear whether this trend will continue as the specimens age.

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I The oxide film thickness is altered  !

i during the simulated wedging, but follows the  !:

growth rate from the undisturbed aging tests. L

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Aging "

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2: IST l- , i 500 t 0 10 20 30 40 50 60 70 80 Time (d) c,, ,,7 ,

In-service testing initially  :

reduced the maximum friction.

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l l Results of Testing to Date The friction for naturally aged specimens has not

! plateaued as the specimens age.

l l The friction during the first stroke was always

.the highest and decreased substantially during additional stroking.

For the single specimen tested, the friction was 5-10% lower following in-service testing.

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

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[ This presentation is an account of work sponsored by an

! agency of the United States Govemment. Neither the United States Govemment nor any agency thereof, nor any of their l employees, makes any warranty, expressed or implied, or i

assumes: any legal liability or responsibility. for any third party's

! use, or the results of such use, of any information, apparatus, product, or process disclosed in this presentation, or represents that its use by such third party would not infringe privately owned rights.

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.--. . - . . . . . . . - - . . . . . - . . . _ - . - - - .

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