ML20209F293

Part 21 & Deficiency Rept Re Gas Bubble Formation Between Diaphragm Layers within Sensing Element of Sor Series Switches.Cause Not Yet Isolated.Formation of Bubble May Cause Setpoint to Shift Outside Tech Specs

ML20209F293
Person / Time
Site:	Davis Besse
Issue date:	04/27/1987
From:	Jerrica Johnson SOR, INC. (STATIC O-RING)
To:	NRC
References
REF-PT21-87, REF-PT21-87-095-000 IEIN-87-016, IEIN-87-16, PT21-87-095-000, PT21-87-95, NUDOCS 8704300252
Download: ML20209F293 (1)

Text

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7 x a SOR, INC.

i. April 27,1987

To

All Nuclear Power Plant Qualified Pressure Switch Users

'Re: Preliminary 10CFR PART 21 Notice SOR is investigating a potential problem with our gauge pressure switches.

We direct your attention to NRC Information Notice IN 87-16. This notice addresses the SOR Series 1, 4, 5, 6, 8, 9,12 and 54 switches.

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, We - have discovered several switches at Davis-Besse Nuclear Generating Station which have contained 'a gas bubble _ formation between the diaphragm layers within the sensing element of the switches. The cause of the problem has not yet been isolated. The use of 316 stainless steel diaphragms has not completely eliminated the bubble formation as previously concluded in

IN87-16.

An indicator of a bubble formation is the increase in deadband of the pressure switch (i.e.: the rise of the increasing set point and/or the fall of the decreasing set point). The formation of the bubble may cause the set point to shift outside the technical specification limits.

SOR continues to investigate the phenomena. For any questions, please contact the factory .at (913) 764-2630, and ask for Nuclear Sales.

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'Regards: 1

' e i JYi *. lO'L"Uv\)Jh,x

! James R. Jo'hnsdn

Vic6 Presideng General Manager N. )

042787-07/ES132 l

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8704300252 870427 l hDR ADOCK 05000346

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