2nd Relief Valve
2nd Relief Valve
(OP)
I have a customer concerned about the fire pump main relief valve failing, which may cause damage to the fire protection piping due to high pressure in the system. They are suggesting installing a 2nd relief valve as a back up. Is this a good idea, where can this be installed?





RE: 2nd Relief Valve
What is your actual static system pressure? What is the head pressure of this pump?
Please advise
RE: 2nd Relief Valve
If this is the case, I do not see any problem with two listed/approved properly sized relief valves located downstream of the fire pump. There is no code or specific reason why this would cause a problem. Loss history would indicate this approach is a waste of money since desiel driver overspeed incidents are rare and the listed/approved relief valves are historically reliable.
I say explain everything in detail to the customer and install a second redundant relief valve if they still want to spend the money for the "extra" level of reliability.
{If you are referring to the 1/2-3/4 in. diameter circulation relief valve on an electric fire pump, this size relief valve is simply not designed or capable of preventing excessive pressure as you have indicated.......in addition, there is really no purpose for a larger diameter relief valve IF you have an electric fire pump!}
I hope this helps.
RE: 2nd Relief Valve
The relief valve is unlikley to fail shut and even if it did, the worst thing that is likely to happen is there will be some drips as the system should have been pressure tested to well above the maximum operating pressure when it was comissioned.
If the client has a big budget, you could install a fire pump with a variable speed drive (these have come on the market in recent years). The variable speed drive will regulate the pressure and if it fails a pressure relief valve will prevent overpressure.
RE: 2nd Relief Valve
If we decide to install the 2nd relief valve, what settings should be used. The current valve opens at 140 psi. The pumps are rated 2000 gpm at 130 psi.
RE: 2nd Relief Valve