Calculating Net Force on Valve in Pipe: Pressure Difference Analysis

In summary: This is usually done with a rotating machine that has a load cell that can measure the actual torque applied.In summary, you would need to know the pressure difference between the two sides of the valve, the dimensions of the valve opening, and the torque required to open the valve.
  • #1
ice109
1,714
6
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?
 
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  • #2
You need only know the pressure difference between the two sides and the dimensions of the valve opening.
 
  • #3
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.
 
  • #4
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...
 
  • #5
FredGarvin said:
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.
 
  • #6
ice109 said:
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.
 
  • #7
i'm designing the valve
 
  • #8
That puts a damper on that idea.
 
  • #9
anyone?
 
  • #10
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.
 
  • #11
See if the attached helps. This was taken from "Aerospace Fluid Component Designers' Handbook", Feb. 1970.
 

Attachments

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  • #12
Q_Goest said:
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
 

What is the equation for calculating net force on a valve in a pipe?

The equation for calculating net force on a valve in a pipe is Fnet = P1A - P2A, where Fnet is the net force, P1 and P2 are the pressures on either side of the valve, and A is the cross-sectional area of the valve.

How do I determine the pressure difference for a valve in a pipe?

The pressure difference for a valve in a pipe can be determined by subtracting the pressure on the outlet side of the valve from the pressure on the inlet side. This can be measured using a pressure gauge or calculated using fluid mechanics principles.

What factors can affect the net force on a valve in a pipe?

The net force on a valve in a pipe can be affected by several factors, including the pressure difference, the cross-sectional area of the valve, the type of fluid flowing through the pipe, the velocity of the fluid, and the angle of the valve in relation to the flow of the fluid.

How does the net force on a valve in a pipe impact its performance?

The net force on a valve in a pipe can impact its performance by affecting the opening and closing of the valve. If the net force is too great, it can make it difficult for the valve to open or close properly. This can also lead to increased wear and tear on the valve, potentially causing it to malfunction over time.

Are there any safety considerations when calculating net force on a valve in a pipe?

Yes, there are several safety considerations when calculating net force on a valve in a pipe. It is important to ensure that the valve is designed to withstand the net force that will be exerted on it. It is also important to follow proper safety protocols when working with pressurized systems and to regularly inspect and maintain valves to prevent any potential hazards.

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