Re: [foxboro] UPS backup time
- From: "TED PLUMB" <tplumb@xxxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Thu, 17 May 2007 11:18:33 -0700
I don't know about your processes but I would assume it depends on your
plant. At our facility (Wastewater) we have power that comes from two
different substations. One primary and one standby. When the primary
goes down we automatically switch to the second which takes about 5 sec.
So, our UPS's are sized to supply approx. 15 minutes at 60% load for
remote DCS cabinets and workstations. Our main Process Support Facility
has a 250kw UPS that's backed up by a natural gas generator. So, If we
loose ALL power we're still in business but the rest of the City most
likely will be down and wouldn't be needing us much anyway.
>>> hiteshk70@xxxxxxxxx 5/17/2007 10:59 AM >>>
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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