I'm not sure what revision, but they are 1995 vintage. I found I/A CAR 7375
which addresses this drift issue, supposedly fixed at revision "W". I'm not
sure. It looks like I will end up taking a precision decade box up and
checking the FBMs.
I appreciate the help on this.
Thanks,
Gaylon
----------
From: Burness, Phil[SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, May 22, 2001 11:42 AM
To: 'Foxboro DCS Mail List'
Subject: RE: FBM03 Drift Characteristics
Any idea what revision of FBM03's you are using? There is a fix in
modules
(Rev J & above I think) that corrects for thermal drift.
Phil
-----Original Message-----
From: Hicks, Gaylon F. [mailto:[EMAIL PROTECTED]]
Sent: 22 May 2001 17:03
To: 'Foxboro DCS Mail List'
Subject: FBM03 Drift Characteristics
I'm conducting an informal survey in lieu of talking to TAC. I
would
appreciate and pertinent information anyone can share.
First, a little background. Browns Ferry uses Feedwater line
temperatures
as an input to our core thermal power calculation during normal
operation
(it's basically an enthalpy balance calc), and we operate based on
our
licensed thermal power limits, so we get whatever electrical MWs
output
based on this amount of steam, river temperature, etc.. If this
number is
inaccurate, we can lose electrical output, and we appear to be
missing about
9 MW electric at the moment. Our Feedwater line temperature is
measured by
two four-wire precision 100 ohm platinum RTDs on each of two
Feedwater lines
with a EXTBLK connection to a CHARC block. We use lab data RTD
specific
curves for each AIN block (we really, really want this to be
accurate), and
have these four inputs split between two FBM03s on the same CP. We
normally
operate with a FW temperature of about 380 degrees F.
Over the last year all four RTD measurements have trended downward
about 1
degree F, which would account for about 2 MW electrical. I have
been tasked
with contacting the vendor (Foxboro) to ask if there is any known
failure
mode or mechanism that would cause these four RTDs on two separate
FBM03s to
trend downward. I though I would try the list first to solicit
opinions.
No derogatory comments please. I have already expressed my opinion
on this
subject, but I don't want to bias anyone.
Again, your patience and any input is appreciated.
Thanks,
==================================================
Gaylon Hicks
Tennessee Valley Authority, Browns Ferry Nuclear Plant
Mail Stop PEC-2C
PO Box 2000
Decatur, AL 35609
Phone: (256) 729-7804 Fax: (256) 729-2047
email: [EMAIL PROTECTED]
FedEx Address: Shaw Road, Athens, AL 35611
==================================================
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