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| Re: PHOTO - Genny on its side (1261645) | |||
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Re: PHOTO - Genny on its side |
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Posted by Bill West on Sun Dec 1 23:40:16 2013, in response to Re: PHOTO - Genny on its side, posted by kew gardens teleport on Sun Dec 1 19:42:55 2013. The Keep It Simple Sam theory has to be considered too. Each additional part increases the likelihood of something failing.ex #1 -a co -worker wanted me to add a second low oil pressure switch to an emergency generator to increase reliability. I asked what the original problem was. He hadn't considered that if it was a failure to shut down then the switches should be in parallel so that either one of them could initiate a shutdown. But if the problem had been false shutdowns then they needed to be in series so that they both had to agree before causing a shutdown. We left the system with one switch, his area was mechanical design not a control design. ex #2 -an oil tanker had a manual switch added to block the emergency generator's circuit breaker and allow the system to be exercised without disturbing the normal power system. First time the generator was needed for real the switch contact failed and kept the circuit breaker open. Bill |
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