Re: [foxboro] UPS backup time
- From: "Ken Heywood" <kheywood@xxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Fri, 18 May 2007 08:12:51 -0400
Backup times for a UPS are a function of particular plant requirements
and a function of your plant configuration and particular DCS
characteristics. In other words, a crap shoot. You are guessing on what
the power failure does to the plant and what is the cause. The bottom
line is that the DCS needs to stay up long enough to preserve data,
sequence of events (if you have it) and to orderly shut down the DCS.
Some plants can keep running partially, but most power failures will
knock down equipment that precludes running production. So, keeping the
DCS alive for, let's say 60 minutes, would let you startup production
faster once power is restored. You won't have to wait for computers, CPs
and FBMs to bootup before starting the plant. Most plants take much more
time preparing to start than any startup time required for DCS.
International standard? It would be fool hearty to develop and I doubt
if any customer would follow one. Take it on a case by case basis!
Best Regards,
Ken Heywood
Process Control Services, Inc.
Hi List,
Does anyone know of any international standard which clearly specifies
how much backup time should a UPS offer when supplying to DCS ( or SIS)?
I am facing a situation where several conflicting client standards call
for opposite requirements. One standard mentions 30 minutes backup
should be OK.
Other mandates for 60 minutes. One more standard says two UPS are not
required and an emergency supply in lieu of a secondary UPS feed should
be OK.
I referred API RP 554 but it is too general on these aspects.
Any help is sincerely appreciated.
Hitesh
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