ML20209E005
| ML20209E005 | |
| Person / Time | |
|---|---|
| Issue date: | 05/21/1999 |
| From: | Bahadur S NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Imbro E NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20209E010 | List: |
| References | |
| NUDOCS 9907140118 | |
| Download: ML20209E005 (2) | |
Text
r's :
May 21, 1999
-?
T'(
i MEMORANDUM TO: Eugene V. Imbro, Chief Mechanical and Civil Engheering Branch, NRR i
. FROM:
Sher Bahadur, Chief Original signed by Engineering Research Applications Branch, RES
SUBJECT:
-STELLITE 6 EVALUATION REPORT The subject report," Summary and Evaluation of NRC-Sponsored Stellite 6 Aging and Friction Tests," INEEUEXT-99-00116, April 1999, is being submitted for your use. This is a summary
' document of the research performed to date on Stellite 6 surfaces to address the need to
. provide assurance that motor-operated valves are able to perform their intended safety function under design basis flow and pressure loads. One of the parameters that affects a gate valve's
' operability is the friction between the disc seats and the valve body seats in most gate valves, I
these surfaces are hardfaced with Stellite 6, a cobalt based alloy.
The results of this research indicate that the surface of ihe oxide film contains crystalline solids within an amorphous substrate. The composition of the solids was not determined, but is l
expected to be chromium oxides, cobalt oxides, or carbides. Crystalline solids in general are very abrasive and can result in high friction between the moving surfaces, analogous to rubbing two pieces of sandpaper together. Longer aging times correspond with larger crystalline grains and higher friction.
s-The friction testing produced an important result with implications for in-plant testing. For all of the naturally aged specimens, the highest friction occurred on the first stroke. For example, the peak friction for the 40-day naturally aged sample was 0.40 on the first stroke.,0.34 on the second stroke, and a little lower on subsequent strokes. It appears that the first stroke smears the oxide film and dislodges some of the granules, so that subsequent strokes see lower friction values and less variation in the friction. This result underscores the importance of planning in-plant tests so that data are collected from the first stroke following a period of inactivity, if you have any questions on the report, please contact Jerry Jackson (415-6656) of my staff.
Attachment:
As stated cc: D. Terao T. Scarbrough
\\
h I
DISTRIBUTION:
/
ERAB r/l PDR
- DOCUMENT.NAME: g:\\jjackson\\stelrpt 74 seceive e sept of this document. Indicate in the loos: "C" = Copy without ettschment/ enclosure "E" = Copy with attachmentlenclosure "N' = No copy 0FFICE~
ERAB/RES,
.O ERAB/RES-l l
l NAME -
JJackson W /
SBahadur$svD DATE 5/IS /99 #
5/ 21 /99 0FFICIAL RECORD COPY 9907140118 990521 PDR ORG.
IStEBPDR b.9 -3 f3Q Y
v 1
4 U0u L
p UNITED STATES
'?
g j
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066-0001
\\*****/
May 21, 1999
. MEMORANDUM TO: Eugene V. Imbro, Chief Mechanical and Civil Engineering Branch, NRR FROM:
Sher Bahadur, Chief b Engineering Research Applications Branch, RES
SUBJECT:
STELLITE 6 EVALUATION REPORT The subject report," Summary and Evaluation of NRC-Sponsored Stellite 6 Aging and Friction Tests," INEEUEXT-99-00116, April 1999, is being submitted for your use. This is a summary document of the research performed to date on Stellite 6 surfaces to address the need to provide assurance that motor-operated valves are able to perform their intended safety function under design basis flow and pressure loads. One of the parameters that affects a gate valve's operability is the friction between the disc seats and the valve body seats. In most gate valves, these surfaces are hardfaced with Stellite 6, a cobalt-based alloy.
The results of this research indicate that the surface of the oxide film contains crystalline solids within an amorphous substrate. The composition of the solids was not determined, but is expected to be chromium oxides, cobalt oxides, or carbides. Crystalline solids in general are very abrasive and can result in high friction between the moving surfaces, analogous to rubbing two pieces of sandpaper together. Longer aging times correspond with larger crystallinc grains and higher friction.
The friction testing produced an important result with implications for in-plant testing. For all of the naturally aged specimens, the highest friction occurred on the first stroke, For example, the peak friction for the 40-day naturally aged sample was 0.40 on the first stroke.,0.34 on the second stroke, and a little lower on subsequent strokes. It appears that the first stroke smears the oxide film and dislodges some of the granules, so that subsequent strokes see lower friction values and less variation in the friction. This result underscores the importance of planning in-plant tests so that data are collected from the first stroke following a period of inactivity, if you have any questions on the report, please contact Jerry Jackson (415-6656) of my staff.
Attachment:
As stated cc: D. Terao T. Scarbrough
]