ML20115A205
| ML20115A205 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Summer |
| Issue date: | 06/15/1984 |
| From: | Haas G PACIFIC SCIENTIFIC |
| To: | |
| Shared Package | |
| ML20114G054 | List:
|
| References | |
| FOIA-84-616 DR-1434, NUDOCS 8406210111 | |
| Download: ML20115A205 (4) | |
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REPORT NO.
DR 1434 ENCLOSURE 2 DATE 10 November 19
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DATA REPORT 1434 INVESTIGATION OF STAKING AND SET SCREW CONDITION ON PSA 1, 3 AND 10 SHOCK ARRESTORS Virgil Summer Plant il i
South Carolina Electric and Gas FROM d PE CIFIC SCIE nTIFIC KIN-TECH DIVISION
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PREPAPED BY AP OVED BY
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[7. E. Glauser Sr. Product Engineer Directp of En g.eering Leo E.
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Chief Design c.ngineer AEV OATE BY APPO.SY PAGES AFFECTED
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f REPORT NO.
DR 1434
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PAGE 1
OF 3
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This report is to review the conditions discovered on a number of PSA 1,-3 and 10 Shock Arrestors at South Carolina Electric
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and Gas, Virgil Summer Plant No. 1.,The conditions reported were the unstaking of the telescop,ing_ cylinder._at_.th_e bal,1 nut threaded joint; and, in addition, the three set screws securing the cylinder end plugs to the telescoping cylinder were found missing on a PSA 1 and PSA 10.
Units on' Report (prior to plant visit)
PSA 3 unstaked 28 units PSA 1 unstaked 5 units PSA 10 unstaked 4 units PSA 10 no set screw 1 unit The following units were examined and confirmed during PSCo tour of Summer #1.
In storage PSA 3 Mfg Date S/N 1464 unstaked Feb 77 S/N 1465 unstaked Feb 77 S/N 1466 unstaked Feb 77 In Plant Semi-installed PSA 3 S/N 1485 unstaked Feb 77 S/N 703 unstaked Oct 76 S/N 1505 unstaked Feb 77 PSA 1 S/N 731-unstaked Nov 76 S/N 733 unstaked Nov 76 S/N 734 uns'taked Nov 76 S/N 735 no set screw Nov 76 J
PACIFIC SCIENTIFIC = KIN-TECH DIVISION
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REPORT NO.
DR 1434 PAGE 2
OF 3
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Mfg Date PSA 10 S/N 779 unstaked
!*ov 76 S/N 780 unstaked Nov 76 S/N 1228 no set screw Feb 77
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SUMMARY
'OF INVESTIGATION From what was observed on the units in the storage area and in the plant, it is the conclusion that the units unstaked or without set screws would function satisfactorily.
Testing has been performed to establish that units, as discovered, would not be a safety hazard.
The missing set screws is looked upon as a random occurrence and Q.A. has taken steps to eliminate this problem with an inspection and verification stamp or mark.
The cause of the unstaked units has not been fully established.
All units examined had been staked.
It is the belief that the unstaking occurred sometime after leaving PSCo facilities.
The possibilities could occur during unpacking, being assembled into kits, improper alignment adjustments, repackaging'and shipment, handling at the site prior to and after installation.
REVIEW OF THE STAKING AND SET SCREW FUNCTION The telescoping cylinder is threaded to the ball nut and torqued into final position.
The torque leads are as follows:
PSA 1 10 ft-lbs PSA 3 36 ft-lbs PSA 10 60 ft-lbs ThetorqueloadsarefortheconvenienceoftheAssemblyDepar3 gnt to assure proper seating of the mated partsg The staking operation serves as a means of safetying against normal.
I handling as in assembly, shipping and installation.
The staking was not designed to resist intenticnal untorquing.
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PACIFIC SCIENTIFIC
- KIN-TECH DIVIS10N 1346 S State Chtfece fifvd. Anaheim, Ca 92803 (714) 774 5217
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REPOR T ' NO.
DR 1434
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OF 3
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The three set screws in the end plug serve the same basic purpose of safetying.
The cylinder end plugs on the PSA 1, 3, and 10 are all torqued to 50 inch-lbs for seating the parts.
The set screws were considered the most simple and practical way to restrain the end plug during normal handling of the shock arrestors.
Once th,e shock arrestor is fully installed with both ball joint ends secured, the two threaded joints cannot be unscrewed and therefore the set screws and stake no longer serve a l
function.
TESTING As stated above, the staking and set screws serve no primary function when the unit is installed and is operational.
- However, this condition was never tested.
Therefore, a PSA 1 and PSA 10 were dynamically loaded through the required frequency and time of the qualification test.
A PSA 1 was prepared without set screws or stake.
The tele-scoping tube was backed off 10 - 15' from full torque and stake position, and therefore loose.
The unit performed satisfactorilp.
The PSA 10 was prepared in same manner except that unit was torqued, staked and then the stake was broken.
It required 60 ft-lbs to breakaway and 50 ft-lbs to drive stake through the keyway.
The dynamic load was performed with the stake out of the keyway approximately 5*.
The unit completed one group of tests per PSCo DR 1377, 3 - 12 Hz in 3 Hz steps at 1004, 75% and 50% of rated load; and above 12 Hz,15 through 33 Hz in 3 Hz steps for single loading in tension and com-Pression at 1001 loads.
The unit met all requirements.
The telescoping tube was then rotated out two full turns and
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the test was repeated with no adverse affect.
PSA 3, which is of identical design, was not tested at this tire because it is believed the PSA 1 and PSA 10 illustrated the concept that units could function and not be a safety hazard.
PACIFIC SCIENTIFIC
- KIN-TECH DIVISION
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