Check Valve OK on the Pump Discharge Flange?

10/24/2024

Can a wafer check or grooved check valve be installed directly on a fire pump discharge flange?

I've found they affect the pump performance by 3 to 8 psi.

When testing we found this true and moved it by a foot. The pump didn’t hit its curve and was fairly new.

Shouldn’t NFPA 20 or manufacturers be aware of this?

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4 Comments

Mike Morey

10/24/2024 08:12:12 am

I've never heard of it being an issue, generally we put in full sized grooved swing checks for whatever it's worth. We install a LOT of fire pumps so I would think it would have come up by now. Though most of our real big pumps are Diesel so they have a relief valve which pushes the check out anyway.

Dan Wilder

10/24/2024 08:26:45 am

Acceptable as long as the pump is not required to have a pressure/circulation relief valve as that valve is to be installed first per 20-22' 4.20.3 (it's been in the standard since at least 2013).

The location of the check valve moving that little of an amount, assuming all other parameters remain the same (pipe size, fittings, and length to the test header remain the same), seems like that 3-8 PSI variation is excessive but maybe the wafer style internal diameter change is enough to change things (pump discharge flange can be a size smaller than the discharge pipe size requirements so a smaller check valve would have a higher loss across the valve at the same GPM if that applies in this situation and not sure if that still complies with 20).

What kind of check valve (clapper, spring clapper, single or double door-including orientation)?

Rob

10/24/2024 12:40:30 pm

I don't think it matters.... You are taking your pressure readings at the discharge flange prior to any check, regardless of its location.
At churn it would have zero impact on the pumps net pressure. Essentially no flow so no impact. Even at 100% or 150% it doesn't matter because you are only looking for GPM"s after the check and are still only concerned with net PSI at the discharge flange before the check.
Am I missing something?

Jack G

10/24/2024 04:28:01 pm

I was shown that a check with a split or rotating element , 6 inch, the check is 3 inches face to face or less ( tight pumproom )
The disc portrudes into the pump cavity. This portrusion affected / affects the pump test results by 5 psi . After this i stopped using the " cheap checkvalve " about 50 years ago. Made a difference if 5 psi. Kennedy wafer check. The water supply was down a tick and the pump curve was shirt.

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Check Valve OK on the Pump Discharge Flange?

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