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Reply to "Firewater pumps p&id and network over pressure protection"

PaulEngr posted:

I can't imagine why you'd have overpressure protection on fire pumps. For one thing most of the ones I'm familiar with are centrifugals so that wouldn't apply (overpressure is a positive displacement pump thing) and it may not be an actual electrical device but more likely simply a rupture disc. When it comes to fire pumps the general protection strategy with them is to run to failure unless the failure would cause additional consequences with the assumption that responding to a fire is the greater hazard. For example fire pumps specifically do NOT have overload/overcurrent protection because the goal is to run to failure even if it means burning up the motor. However a short circuit can shut down multiple fire pumps and/or cause other unforseen consequences so short circuit (fuse or magnetic-only circuit breaker) protection is included. Based on the same logic though I have never seen a written standard for fire pumps. I would have to imagine that overpressure protection would be along the same lines...even if we blow the line apart or dump water everywhere and hardly get anything put into action to put out the fire, so overpressure protection wouldn't be included.

PaulEngr, good day!

Actually there are many firewater network damages occurred in the past months due to the high pressure.

The sequence will be like that:

1- due to firewater pressure drop, the main electrical pump will start automatically. And from firewater philosophy, it can be stopped manually only.

2- while the operator investigating the cause of the pump start, this pump will keep the pressure increasing in the firewater network untill the pipe joint fails!


And thats why i want to add a control valve to eliminate the overpressure events.


Again please if you have any p&id for any firewater system please pass it to me.

Looking for your ideas please.