Hey, wait a minute.
This is awkward, but...
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Posted 21 April 2012 - 04:10 PM
I see in a local PID that PI is placed between centrifugal pump and check valve. I believe that this covers the case of check valve failure - stuck closed. By observing the PI, you can conclude that check valve has problem, not the pump. Or that the pump has problem, if PI shows lower than usual operating pressure.It is noted that min flow line is also connected between pump and check valve. So if check valve stucks closed, the pump will be protected by circulation through this line.See also http://www.cheresour...-valve-failure/ '> http://www.cheresour...-valve-failure/ Is there a min flow line? If so, I would place the no flow switch downstream check valve, net flow is of interest. If no, I would place it upstream check valve, thinking of better protection against water hammer (during startup or sudden stop of the pump).