We have Diesel engine driving fire water Pump. I found the speed sensor considered not SCE (Safety Critical Element) while it is used for overspeed protection of the diesel engine. Is this correct ?? What is the reason to not consider it SCE?
HSH5757...
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My copy of NFPA-70, 2017 version, does not contain the term "SCE". Can you provide the source that does?
My opinion is a speed problem with an engine-driven fire-water pump will be revealed as a water pressure problem!
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Phil Corso
I agree with PhilCorso; a speed problem with a running fire water pump driven by a diesel engine would manifest itself in a pressure problem. The first thing a trained, conscious operator would do is have someone go out to check on the diesel--and if the diesel speed sensor is visible on an HMI check that, too. Is there a strainer of some sort upstream of the diesel-driven fire water pump? If so, is there a differential pressure switch or transmitter across that strainer connected to the control system?
Are there AC motor-driven fire water pump(s) on the site that feed the same system as the diesel driven fire water pump?
If there are no AC motor-drive fire water pump(s) on the site that feed the same fire water system as the diesel driven fire water pump, where does the pressure for the fire water system normally come from?
What starts the diesel-driven fire water pump--low fire water system pressure? Low AC mains power supplying the AC motor-drive fire water pumps? Some combination of the two?
Is there a check valve downstream of the diesel-driven fire water pump and a pressure switch between the diesel-driven fire water pump discharge and the check valve separating the diesel-driven fire water pump discharge from the rest of the fire water system?
These are some of the questions the designers of the system likely took into consideration. Likely; and probably; but not certainly.
And, again, to PhilCorso's question--please provide the citation to the term SCE.
