Hi All
I want to use a high performance eccentric butterfly valve for gas flow control pupose. Dont ask me why butterfly, due to the cost reason and so many other reason my client wants butterfly valve.

Ok my question is what should be the minimum opening for the butterfly control valve?? As per my flow calculation, the opening for minimum to maximum flow is 4 to 50%.

Is it possible to control butterfly valve at 4% opening for minimum flow (minimum flow is not a normal case, it happens very few times).

Please help me

 

Hi Dasa,
Normally I use an orifice 2-3 meters before or after such valve to get a laminar flow.

This orifice has 2 pressure outputs for high/low pressure as pressure drop across the orifice. Then you connect a difference-pressure transducer, that has a range for 0% p-drop=4mA and 100% p-drop=20mA to an AI-card in your controlling device. This method is much better than a position of the valve, because position-control is moving out of its scaling by the time.

Furthermore, the orifice measure actual flow directly, while a position measure indirect, e.g. the motor operate, but the valve don't!

Regards
Jan

 

Hi Dasa,

What is the brand of the HPBV (High performance Butterfly valve) that you are using? In my opinion, butterfly valves are not that great for control applications. I understand you have selected HPBV due to the cost reason. However, I don't see the valve providing a good control at the opening you mention. Butterfly valves on a safe side should be used only from 20-50 degrees for good control. In exceptional cases you can go upto 60 on the higher side and 10-15 on the lower side.

4 degrees is too low.

Also, what is the manufacturer published Cv characteristic of the valve ? Is it Equal Percentage ?

Ronald Deepak
jronalddeepak [at] gmail.com