Check Valves: Upstream/Downstream Diameter Requirements

[computercameraman]

I'm working on a water pump station design where we will use tilting disc check valves on the pump discharge piping. Tilting disc check valves were chosen due to the possibility of transients and their non-slam characteristics.

I'm having difficulty confirming what upstream/downstream length requirements we should use. Here's what major manufacturers state:
- APCO/DeZurik: "Good pump station design encourages at least 3 pipe diameters of straight pipe down stream of a check valve (in some cases the upstream side)." I've spoken
- Val-Matic: "The valve should be installed in water pipelines three diameters downstream of pumps to prevent reverse flow."
- GA Industries: no published requirements
- Flowserve: no published requirements
- Henry Pratt: no published requirements

MSS SP-92 recommends installing a check valve 10 pipe diameters downstream and 5 diameters upstream of tees, fittings, pumps, etc.

I'm arguing in favor of 3 upstream diameters, since that seems to be on the shorter side of recommendations. Even DeZurik has articles that show elbows right after their check valves. However, I've received pushback that we can reduce the requirements further to save space (e.g. put the check valve directly after the reducer on the pump discharge).

What guidelines does everyone follow, if any? Do you defer to the manufacturer or just place the check valve as close as you can?

 

[1503-44]

Go with the MMS SP-92 spec unless you have a specific case and a a very good reason why you cannot.

Trying to "save space" might be a good reason in aircraft, or submarines, probably should not be of serious concern for water pump stations.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

The issue is one of turbulence affecting the action of the valve and possibly leading to vibration and wear / noise.

This applies U/s for the valve and D/S for other components.

You see all sorts of check valve location and there is as ever a compromise between 3D distance and space needed for the piping.

where possible put the valve in a straight, level bit of piping and maximise the straight pipe length.

Like this article says, 5D is probably more common upstream, but key is to ask the valve vendor.

https://www.valvemagazine.com/artic...onsiderations-to-maximize-process-performance

If you're really concerned you can always add a flow straightener or disc up stream.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[swazimatt]

that flow straightener looks like it would eat up a good chunk of head.

 

[LittleInch]

They don't. 1 or 2 psi nax.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

I will also recommend following MMS SP-92 spec unless you have a specific case and a a very good reason why you can't. The overall distance will depend on the pipe diameter which you have not stated.

 

[1503-44]

Putting in a flow straightener, if the only reason you are using it is to save space.seems like not much gain in overall shortening is going to happen. there's usually a couple of flanges that go with it.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."