# Pressure drop across butterfly valves

1. Jul 28, 2011

### matheus_carva

Hi,
I'll make a valve open and close for some degrees that I have to calculate, the valve motion will produce a pressure wave in the pipeline. I have to know how many degraus I must open the valve to produce a pressure drop that I want. Someone know how I can calculate it? Is there an equation that predict the pressure drops across a butterfly valve working as a throttling valve.
Thanks.

Last edited: Jul 28, 2011
2. Jul 28, 2011

### nickcarin

Related: https://www.physicsforums.com/archive/index.php/t-67757.html

Short Answer: Find a valve manufacturer that has determined this data for the same type of fluid, pressures, and temperatures that you are operating at, or find the desired valve positions through trial and error.

Long Answer: Without knowing the fluid and operating conditions (temperature, pressure) it would be difficult to come up with the proper equations. As far as I know, all fluid flow equations were derived based upon assumptions of the fluid properties at certain operating conditions.

Even with the appropriate flow equation, the resistance coefficient for valves and other fittings were determined experimentally. Likewise, these coefficients would need to be experimentally determined using your specific type of valve, at your specific operating conditions, for each degreee of valve rotation.

3. Jul 28, 2011

### edgepflow

To add to the last post, most butterfly valve manufacturs will have literature with tables of flow coefficient Cv vs % open.

4. Jul 29, 2011

### matheus_carva

Thanks, I'll get in touch with the manufacturer to ask about coefficient Cv.