Check Valve Positions

Depends on the type/style/manufacturer of valve.

For example, these dual-discs may be installed in this manner (with factory approval)

www.keystonevalves.com/pdf/Gulf%20Wafer%20Check%20Valve%20IOM%203-07.pdf

Check valve can be installed in any position, but contact the manufacturer, since it is not that all valves can be done like that. Most of the time the valve is positioned by the guide shaft and the spring and hence become position independant.

However there are valves that are sensitive to the position.

Best person to contact is the manufacturer and his catalogue.

If you want to position the check valve vertically, ask for it.

Give the details since now the gravity and the static head is working against spring, so you are likely to need some extra spring stiffness.

This configuration is just a bit odd by our practice, since our NRVs normally have the vertical, but flow upwards.

Yes, provided only that the spring inside the valve can hold back the column of liquid above it, which can only be determined locally. If there is no spring, or the spring is not strong enough, then installing the valve in a line that is flowing vertically downwards will obviate the correct working of the valve, and render it useless. There is always a good process reason for installing a NRV. So it would be better to find a horizontal or rising process flow position, and install it there so that the process works as designed.

I'd avoid this unless there is no alternative, and even then only after giving all the details to the NRV supplier and getting agreement that it's OK.

Cheers..........Codey

You have not told us if you are asking about a specific type of check valve.

The standard "Swing Check" valve cannot be installed in the vertical with the flow down.

However, some Swing Check (not all) valves can be supplird with an external counter weight connected to the disk pivot pin that will close the disk during a no-flow condition.

I'm going to go against the flow and say, "NO". I've been thinking of it for awhile now and have yet to see a check valve in that position. There would be two quick reasons that I can think of.

1) The weight of the fluid or gravity would keep it open and any reverse flow would slam it shut so hard as to damage it. Most gravity check valves are built with a slight angle of the seat as to be all ready in the closed position when mounted horizontal.

2) Spring check valves become relief valves, a certain amount of pressure is required in order to open such valves, thus defeating the purpose. I think a check valve should be free flow one way and closed the other.

Any way, kind of like hockey, "Keep your stick on the ice and your check valves horizontal".

Hi,

The answer is yes if it is a spring loaded variety.; are usually disc or butterfly hinged type.

Watch out for the pressure loss across these valve especially the ones that fit between flanges as in something like a 4''NB pipe sized valve the orifice can be little more than 3''. Manufacturers provide tables of resistance to flow and delta P losses for these devices.

If the resistance creates a problem you can always increase the pipe size at the NRV by use of welding reducers either side of the location flanges.

In the UK you will find valves of this sort sold by Gestra and BSS as Northvale products suitable for most non-aggressive applications.

Hope this helps you.

May be quite dangerous with these - normal disc type/ hinged type with the flow downwards. The static head in these cases will act to disengage the seal.

The heavier spring loaded - the axial (ball type or cone type or their variants) are a bit safer since the spring stiffness for them is much higher. But i am yet to

a) come across one with the large NB

b) Usage of one , even this type, when the flow is downwards.

It is extremely not-preferable if permitted to say - since the forward flow now has to overcome the spring stiffness before the valve opens and the flow resistance (and hence pressure drop across valve) are going to be very high- almost unacceptable range.

The reducers before and after - must be carefully chosen since the valves (or anything for that matter) do not like much of a turbulance around.

But why at all the NRV is to be put in this position ? (asked in #2 onwards) and OP is silent as in most of the earlier posts .

Friends,

I've read the posts to date and am confused. I understand a check valve (NRV) to be desired when you want the fluid flow to be unidirectional. To me this means that when the fluid pressure downstream of the valve equals or exceeds the pressure upstream, the valve must be closed. Some of the posts suggest that a spring is needed to hold back the pressure of fluid upstream when there is none downstream--this appears to me to be unnecessary. Therefore, I suspect the external counterweight on a swing-check or butterfly-check and the spring on a ball-check or similar valve only needs to be sufficient to counter the mass of the moving element in the fluid.

With regard to the concern raised about the valve "slamming" against the seat, this is a real problem in the real world, and is most easily resolved by the use of a hydraulic damper or shock absorber. This will add a variable resistance to the motion of the valve, proportional to the speed of motion.

External counterweights and dampers have all been available for many years. Therefore, I would agree with those who say a vertical orientation with fluid flow downwards is possible if the proper valve and associated parts are used. I do not see the need for increased spring tension, other than for compensating for the mass of the moving element in the valve (in an application with vertical orientation and fluid flow upwards the spring pressure only needs to be enough to ensure seating at no flow without having to counter the mass of the moving element).

For fun, consider the requirements if the fluid being checked is mercury (liquid). In this case, the external counterweight would need to be used to hold the valve closed in a vertical upflow orientation; none would be needed in a vertical downflow orientation!

--JMM

NRVs are available in horizontal and vertical positions. We have to select as per our requirement like type of fluid, cracking pressure and direction of flow etc., In hydraulics not, it is not a problem for vertically down or up ward flow, where as for fluid transmission it should be selected as a need basis.