Pressure drop across butterfly valves

In summary, the individual seeking help needs to determine the correct valve positions for desired pressure drops by finding a valve manufacturer with data for the same fluid, pressure, and temperature conditions or through trial and error. This is due to the specific fluid properties and experimental coefficients needed for accurate calculations.
  • #1
matheus_carva
2
0
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:
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  • #2
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
To add to the last post, most butterfly valve manufacturs will have literature with tables of flow coefficient Cv vs % open.
 
  • #4
Thanks, I'll get in touch with the manufacturer to ask about coefficient Cv.
 

1. What is pressure drop across butterfly valves?

Pressure drop refers to the decrease in pressure that occurs when fluid flows through a valve. In the case of butterfly valves, this drop in pressure is the result of the fluid passing through the restricted area created by the partially closed butterfly disc.

2. How does the design of a butterfly valve affect pressure drop?

The design of a butterfly valve, specifically the shape and size of the disc and the angle of the seat, can greatly impact the pressure drop across the valve. A properly designed butterfly valve will have a streamlined disc and seat, minimizing turbulence and reducing pressure drop.

3. What factors can cause an increase in pressure drop across butterfly valves?

There are several factors that can contribute to an increase in pressure drop across butterfly valves, including a high flow rate, a partially closed valve, a poorly designed valve, and a buildup of debris or sediment on the disc or seat.

4. How can pressure drop be minimized in butterfly valves?

To minimize pressure drop in butterfly valves, it is important to choose a properly sized valve for the intended flow rate, ensure that the valve is fully open during operation, and regularly clean and maintain the valve to prevent buildup of debris. Additionally, selecting a valve with a low pressure drop coefficient can also help reduce pressure drop.

5. Are there any alternatives to butterfly valves that can help reduce pressure drop?

Yes, there are several alternatives to butterfly valves that can help reduce pressure drop. Some examples include ball valves, gate valves, and globe valves. These valves have different designs and operating mechanisms that may be more suitable for certain applications and can potentially provide lower pressure drop than butterfly valves.

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