Spring checks

[Deleted User]

I ran into this just the other day. I found the problem to be in how the plumbing was installed. The return pipes were "t,ed" in together to close to each other and when one pump turned on to cause conflict. I stoped the chatter by relocating the return t.

Steve Thomas (Foley Mechanical)

noisy spring check

I have just repiped a boiler and the customer called to complain about a noise she was hearing. The noise is coming from one of the spring checks I installed. We have three zones on the system now. All have flow controls on the supplies (B&G)and spring checks on the returns(Simmons). The main house is an old gravity system 2" mains. The second zone is a series loop w 2 rads piped in 1" and the third is the indirect 1". I used a series 100 on the main house loop and 007's on the others. I get a chattering noise from the 1"14 spring check on the return of the main house loop when either of the other zones are calling at the same time. Anybody have a solution?

Tony Conner

The Check...

...is probably too large for the flow.

ScottMP

The seats

Check the check , make sure it has a teflon seat. I used one product that a teflon ball and a brass seat and it chattered ... everytime.

Scott

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Dana

What is the purpose of the spring check. If you have flow checks why is it needed and why a spring check.

Tony Conner

From...

... the "Flow Of Fluids Through Valves, Fittings And Pipe - Technical Paper No. 410" by Crane:

"Most of the difficulties ecountered with check valves, both swing and lift types, have been found to be due to oversizing which results in noisy operation and premature wear of the moving parts."

"Sizing of check valves in accordance with the specified minimum velocity for full disc lift will often result in valves smaller in size than the pipe in which they are installed; however, actuall pressure drop will be little, if any, higher than that of a full size valve wich is used in other than a wide open position. The advantages are longer valve life and quieter operation."

I found this info about 10 years ago, and since I started using it, most of my check valve problems have disappeared. Really.

A pretty good rule of thumb is that the check valve will be one pipe size smaller that the line in which it's installed, assuming the line is the correct size for the flow, and not oversized. Far more important than springs, or soft seats, or anything else is pick the right size valve for the expected flow.

Frank_3

Hmmm...

That's an interesting article. I would think that if you have sized the pipe correctly for the expected flow then the same size check valve would be appropriate. I just took a look at the Taco web site and don't see anything in their FloChek specifications about "minimum velocity for full disc lift", just Cv numbers. The listed Cv are right around the maximum recommended flow for the given pipe size, so it certainly looks like you would pick the valve that matches your pipe size.

Where did you find the "minimum velocity for full disc lift" ratings that leads you to pick a valve one size smaller than the pipe?

[Deleted User]

What size

main did you run out to the zones? Is it possible that the main does not have the capacity to provide enough volume for the 1 1/4" main zone, and either, or both of the 1" zones at the same time?

A starving pump(s) will cause flow & check valves to do funny things. Noise is one.

Tony Conner

It's Not...

...an article. This is a widely recognized engineering publication dealing with fluid flow. There's engineering software available that's based on this thin soft covered book. ABZ was the original partner with Crane for it. It'll actually flag you when you've selected a check valve that is too large for the flow conditions. Crane and ABZ have apparently had a falling out sometime in the last few years, and Crane now does their own. But ABZ is still around.

Valve manufacturers will have literature on how to size their products. Every catalogue I've seen shows the formula, or has a chart on how to select a check for a given service.

Check valves are like control valves - line size is almost always oversize. Ever seen a swing check where the shaft has worn through the hole disc assembly, so the disc hangs crookedly in the valve body? That's an oversized check valve, with the disc flapping up and down in the fluid flow, like a flag in the wind.