Subject: NCSX _ Thermocouples From: "George W. Labik" Date: Mon, 28 Apr 2008 17:22:43 -0400 To: "John Lawson" , "Robert J. Marsala" CC: "Stefan Gerhardt" , "Paul Sichta" , "Brentley C. Stratton" , "Michael E. Viola" Thank you for testing the two repaired T/C on V V1 and 2 on V V2. I will use this E mail as a way to get some information to others that may not be part of your concern. After you left, Wes and I continued the T/C check out. I observed TC 1, connector pin A to vessel ground, Port 12 flange 12, V V1 bottom for 15 minutes, it reached an impedance of 1.5 M? and was still rising. This repaired T/C reached a level similar to a non repaired T/C. Two repaired T/Cs on V V2, TC 43 and 44 were similar, reaching impedance values of 1.8 M? and still rising. Paul Sichta will provide a person to conduct a full testing of the cabling on the V Vs and will provide input to the testing definition and Installation Procedure. I will pass along the E mail comments from Stefan Gerhardt and John Lawson to Paul. In addition John has thought up a way to activate specific Flux Loops. Based upon the experience of this morning, checking the impedance of the T/Cs will take a long time using a Fluke meter with it's low voltage battery. I suggest that all T/Cs impedance be checked, perhaps specifying a time limit, and that the feedthrough pin location be verified by using a heat gun and Drawing SE 121-004 for location on the vessel. Electric heater strips are furnished in pairs, a primary and spare, and should be driven with a power supply to verify the pins used on the feedthrough. I believe Ray Gernhardt performed this test but I don't know if it was documented. One thing I noticed today was that the heater strip wires are routed to the feedthroughs across the heater strips themselves. The # 4 heater strip wires pass over all the other strips. I don't know how hot the strips can get if the vessel temperature is low and the power supply is cranked up to max. I would suggest that the wires be held off the strips in some fashion and that the power supplies not be able to be set to a max current. As a minimum the flux loops should be checked with a Fluke meter for continuity by measuring the conductor resistance, and impedance [ can the inductance be measured separately ? ] to vessel ground and using an exciter coil to verify the loop to pin data. Should the impedance be measured at a higher voltage than that of the Fluke meter?