Axial Check valve installed as a foot valve

[Ajay25]

Hi,
An axial foot check valve is installed in the vertical position in a sump.
The height difference between the (pump suction flange) and the (foot valve location) is 3m.
The issue is that the foot valve is leaking (not fully closing)to allow to prime the pump and hence it is not possible to pump water from the sump.
The manufacturer manual of the axial check valve states that 5m WC is required for tight closure of the axial check valve in vertical position.
Can we install the foot valve horizontally using a 90 degree bend, so as to make the same axial valve work as a foot valve (with tight closure)?
Do you see any other way to make the scheme work without changing the foot valve?
Thanks

 

[MikeHalloran]

Go ahead and put the bend in, but I don't think it will help; few pumps will self-prime from liquid that's 3m down.

I think you'll need a vacuum pump to prime the suction, or move the pump down toward the bottom of the sump.




Mike Halloran
Pembroke Pines, FL, USA

 

[LittleInch]

Why would making the valve horizontal change the WC required to seal it??

You could install two in series?, install a self priming pump or add a vacuum line to the inlet of the pump to proved the flooded inlet or try a different type of foot valve, aka Non return valve or install a submersible pump.

No other details so can't really go much further....

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

 

[Compositepro]

It probably makes most sense to change to a valve design that works. The purpose of the valve is to prevent drain-back of the lines so the pump does not lose its prime. Adding 2 meters to the rise of the discharge piping will put 5 meters of head on the foot valve.

 

[Compositepro]

Also be aware that any water level in the sump subtracts from the water column that the foot valve "feels". That is, if your pump discharges at one meter in elevation over the water level in the sump, then there is only one meter w.c. on the foot valve, regardless of how deep the valve is.

 

[georgeverghese]

Maybe we could check if this axial check valve vendor can retrofit an air assist closing / opening cylinder ?

 

[georgeverghese]

Ideally speaking, upon a normal shutdown of this pump, and if a discharge shutdown valve closes at around the same time, the suction line should remain primed. If air gets into the suction line, it can be due to

a) Reverse flow of air through the discharge line if there is no discharge SDV
b) Reverse flow of air through pump shaft seals - for single seal configuration
c) Some other reverse flow location.

See if you can cut out these reverse flow sources, where applicable.

 

[Brian835]

Check out

http://www.checkall.com.

These valves are used as foot valves. They are spring loaded poppet style; therefore, the spring will provide for a "bubble tight" seal without the need of head pressure (back pressure) to close the valve and prime the pump.

 

[Ajay25]

Hi,

Mike and Littleinch, you guys are right, it does not make a difference if I put in a bend.

compositepro, I don't completely agree with that, because the head available above the foot valve outlet flange, is equal to the length of the pipe below the flange of the pump suction flange, irrespective of the level of water in sump. Please explain to me if you think differently.

Georgeverghese, Interesting way of opering an axial foot valve with air assistance- do you have an example?

Regarding the issue at hand,
I discussed with the manufacturer regarding the issue, and they informed me that the check valve is designed to close reliably at 5m and not 3m in vertical condition.
I suggested a change of spring to facilitate closure of the foot valve at 3m, but apparently tolerances, coating thickness and other features also need to be controlled to ensure that the foot valve will reliably close at 3m.
Thankfully the manufacturer agreed to send the axial foot valve tested for 3m.

Thank you for your comments.

 

[Compositepro]

The differential pressure across the valve is equal to the height of the water column in the pipe above the water level in the sump. When not running, the pump is just a small restriction in the pipe. The length of pipe under the water level in the sump has no effect on the valve because the water pressures inside and outside this section of pipe are the same.

I just re-read your original post and I wonder why you think mounting the check-valve horizontally would help. In almost all valve designs the ball or flapper weight will help seal the valve in the vertical position, which is what you want.

 

[georgeverghese]

See recent discussion at thread 408-45678 for air assisted check valve.