Originally posted by MColley
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If all the pumps in a series are cranked up to 3,500 RPM (that's pump speed, not engine speed), and the attack engine suddenly reduces his flow, then the friction loss instantly disappears. But the governor keeps the pumps cranked up at a high speed. You go from having a relay to giant 3 or 4 stage pump. That is dangerous.
Centrifugal pumps are known for their ability to take advantage of intake pressure, and their ability to add net pressure to the water. When the friction loss is removed, this pressure compounds with each impeller in the system. Something has to give, and it might be something you were counting on.
When you're in a relay, your governor should be in the PRESSURE mode.
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