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Does size matter.
Posted: Mon Apr 09, 2012 9:40 pm
by swyld
Does the area/diameter of a non-return valve,check valve, call it what you will, make a difference to the load on a boiler feed pump? I am using a basic domestic valve with a swing flap, thinking that a similar area on both sides would make little difference to the force required to open it. Right or wrong?
Re: Does size matter.
Posted: Tue Apr 10, 2012 4:04 am
by barts
Swing checks work just fine from a pressure differential standpoint, but they're best if you don't try to run them too fast, or use a very small pump plunger. Ideally, a pump like this would have a large piston/plunger running at 100 rpm or less. For high speed use, lift checks with screws added to limit the lift work well.
Remember to fit a fine strainer ahead of the pump; check valves hate scale, pine needles and other things that find their way into hot wells and suction lines!
- Bart
Re: Does size matter.
Posted: Tue Apr 10, 2012 4:43 pm
by DetroiTug
The size of the check valves from what I can tell does matter. The smaller the line size, the faster the velocity of the liquid moving through it for each stroke of the pump, What really closes a check is the liquid trying to come back. If the line size is large, the small volume of water from the pump stroke, barely makes it past the check valve, the opening is large, and more is lost reseating the valve; the reason large check valves are usually altered to not open very much or "throttled". On the tug I'm using 1/4" inline check valves, works very well. Seems that is what all the steam car folks use as well.
-Ron
Re: Does size matter.
Posted: Thu Apr 19, 2012 3:07 pm
by SL Ethel
For my 5 hp plant I had good luck with a soft seat, stainless, spring loaded in-line check. It was 1/2", so it did not restrict flow, but because it had light, spring loaded internals, it did not chatter or wear even though it was on the delivery side of a hypro pump without any sort of damper.
I don't know where the valve came from (though it was definitely steam rated) because it came with a boiler I bought that was originally in a food-packing plant (hence the all SS fittings and valves that came with).
I believe you can get similar valves for a reasonable price from McMaster Carr.
Cheers,
Scott