Flow through a check valve

Question

is the flow of a fluid through a check valve subject to fluctuations due to any disk movement ?

Answer 1

Check valve disc fluctuations in liquid systems are not likely for a properly sized valve, and if present at all would have immeasurable effect on the contunity of flow.

The effect of turbulence caused by the valve would probably have as great an effect on flow, but those local disturbances would be likewise dampened-out downstream.

I have seen off-centered pivot check valves in process air systems which did some rocking, but we did not consider it a problem, either.

As an aside, with common swing-check valves there can be a reversal of flow when the pump is shut off in a pressurized system and this can cause pounding and potential damage due to water hammer.

Answer 2

Fluctuations as in the  pressure or flow rate?

If the pressure is not high enough to properly unseat the valve then I would suppose so.

Answer 3

I am assuming the check valve will be in the discharge line of a pump.

In some pumps like reciprocating ,you will find suction and discharge check valves.

I dont think pressure fluctuation is due to the disk movement untill and unless there is a trapped situation in the disc movement.I mean to say the disc is malfunctioning due to choking.

The biggest draw-back with check valves is the pressure drop,not fluctuation.

Most probably the the fluctuation will be caused by the suction pressure condition and varying loads in the down-stream .

Creation of vapour in the pump casing or in the discharge line may cause the fluctuation.

In the check valve of a pump [positive displacement pump] if the disk is unbalanced then it may cause a variation in flow and pressure.

if the padding the discharge line is not proper then flow will be erratic.

In my opinion you must check with the flow passages and suction condition.

Get through the NPSH principle.