Valve Cracking Pressure

nicola_78 · January 11, 2016, 10:52

Hi everybody!

I'd like to evaluate the cracking pressure (which is the minimum upstream pressure to open the valve) of a swing check valve by means of an analytical method and a CFD analysis.

The disc has to open of a small distance.

Any suggestions?

Thanks!!

kaya · January 11, 2016, 14:11

assuming spring has a constant torque T, and the length between the center of the valve and the spring position is x, so you need flow pressure to generate F = T*x much force on the valve. If the area on the valve is A then you need the static pressure of P > F/A from the flow to open the valve. I don't think you need a cfd computation to find P since the flow is going to be creeping flow at the pressure which is just enogh to open the valve.

I am not sure why you consider CFD for such problem

nicola_78 · January 11, 2016, 18:11

First of all T=F*x. Then there is no spring, only the weight of the disc, let's assume it 2kg for example.
It is different, do I have to impose a small angle of rotation (1-2°), just the minimum to make flow pass? Do I have to impose a balance to rotation?

kaya · January 11, 2016, 18:27

you're right.

to me if there's no spring than any pressure greater than the ambient will make the disk / valve open considering that the center of gravity is aligned with the hinge.

nicola_78 · January 12, 2016, 03:33

Unfortunately the solution is different.

January 11, 2016, 10:52	Valve Cracking Pressure	#1
nicola_78 New Member Join Date: Nov 2015 Posts: 10 Rep Power: 11	Hi everybody! I'd like to evaluate the cracking pressure (which is the minimum upstream pressure to open the valve) of a swing check valve by means of an analytical method and a CFD analysis. The disc has to open of a small distance. Any suggestions? Thanks!!

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January 11, 2016, 14:11		#2
kaya Member Kaya Onur Dag Join Date: Apr 2013 Posts: 94 Rep Power: 13	assuming spring has a constant torque T, and the length between the center of the valve and the spring position is x, so you need flow pressure to generate F = T*x much force on the valve. If the area on the valve is A then you need the static pressure of P > F/A from the flow to open the valve. I don't think you need a cfd computation to find P since the flow is going to be creeping flow at the pressure which is just enogh to open the valve. I am not sure why you consider CFD for such problem

January 11, 2016, 18:11		#3
nicola_78 New Member Join Date: Nov 2015 Posts: 10 Rep Power: 11	First of all T=F*x. Then there is no spring, only the weight of the disc, let's assume it 2kg for example. It is different, do I have to impose a small angle of rotation (1-2°), just the minimum to make flow pass? Do I have to impose a balance to rotation?

January 11, 2016, 18:27		#4
kaya Member Kaya Onur Dag Join Date: Apr 2013 Posts: 94 Rep Power: 13	you're right. to me if there's no spring than any pressure greater than the ambient will make the disk / valve open considering that the center of gravity is aligned with the hinge.

January 12, 2016, 03:33		#5
nicola_78 New Member Join Date: Nov 2015 Posts: 10 Rep Power: 11	Unfortunately the solution is different.