Calculating Net Force on Valve in Pipe: Pressure Difference Analysis

[ice109]

if i wanted to figure out how much net force/torque is applied to a regular disk type valve in a pipe as a function of the pressure difference on both sides of the valve what would i have to do/where would i have to look?

 

[negitron]

You need only know the pressure difference between the two sides and the dimensions of the valve opening.

 

[FredGarvin]

When you say "disc type valve" do you mean a butterfly or a gate valve?

You can sometimes calculate that but to get a good number you can contact the manufacturer with the operating conditions. They can give you very good numbers usually versus percent open.

 

[gmax137]

try the NRC.gov website, and have a look at their Generic Letter 89-10. this subject has been treated in excruciating detail. I'm sure there are documents which describe the calculations needed to show compliance with the generic letter. There is a subsequent GL that kind of follows up but I can't recall the number or date of that GL.

The NRC interest began with motor operated valves, since the operators necessarily include a torque-sensing device to turn the motor off (to keep the motor from ripping the valve apart). The torque-sensing is necessarily adjustable, so the NRC question is, "how do you set the torque switches?" From this simple beginning a sub-culture of calculations and methodologies sprang...

 

[ice109]

When you say "disc type valve" do you mean a butterfly or a gate valve?

You can sometimes calculate that but to get a good number you can contact the manufacturer with the operating conditions. They can give you very good numbers usually versus percent open.

i mean butterfly type valve. the situation is that i have a valve with unequal pressures on each side and i want to know how much needs to be applied to turn it all the way through the turn i.e. as the pressures come to equilibrium.

 

[FredGarvin]

i mean butterfly type valve. the situation is that i have a valve with unequal pressures on each side and i want to know how much needs to be applied to turn it all the way through the turn i.e. as the pressures come to equilibrium.

That's what I was thinking you were pushing towards. Honestly, if you are interested in saving time, you can talk to either the valve or the proposed actuator manufacturer. They will be able to size a valve actuator to suit your situation. Letting them do that gives you more time to do the important things.

 

[ice109]

i'm designing the valve

 

[FredGarvin]

That puts a damper on that idea.

 

[ice109]

anyone?

 

[FredGarvin]

I would estimate projected areas and use Bernoulli to calculate the delta P across the valve to give you an estimate and then multiply by a factor of safety. At least that way you can ensure that, if anything, you will be on the high side of the torque requirement. Honestly, I have never had to do this and I was always under the impression that accurate numbers were always derived experimentally. I'll poke around to see if I can find anything in some handbooks.

 

[Q_Goest]

See if the attached helps. This was taken from "Aerospace Fluid Component Designers' Handbook", Feb. 1970.

 

[zul8tr]

See if the attached helps. This was taken from "Aerospace Fluid Component Designers' Handbook", Feb. 1970.

Good source, see page 6.2.3.4 for activation forces