Butterfly Valve

Your colleague is wrong, butterfly valves can be and are used to control flow. There are many different types of butterfly valves with different designed discs and offsets etc for a wide range of flows. They are not suitable for all flow control, but have a definite and relatively cheap place as a flow control device.

Extract from the Hayward site Butterfly Valves:

Butterfly valves control flow through a circular disc or vane by turning the valve's pivot axis at right angles to the direction of flow in the pipe. They are normally used as throttling valves to control flow.

Butterfly Valves: Learn more

It depends upon how accurately you want to control the flow.

The butterfly valves typically have an S shaped characteristics curve.

That means the response is sluggish in the low angle of opening and the valves also do not behave well when almost closed. It is only in the middle portion it responds and then also too quickly to the angle change.

I second. It really depends on your application,

A butterfly valve is a cheap, simple way to go and for some appilcations would be the best choice.

If you need precise control over a wide range of flows, a butterfly valve is probably not the best choice.

What other type of flow modulating valve would one use in a pipe >2.5m Ø (apart from a VSD on the pumps, that is) <rhetorical question>?

A butterfly valve can be controlled by an adaptive pressure control (APC) unit.

I am using butterfly valve for controlling water flow upto 10000 m³/hr. The feed back is taken from a magnetic flowmeter. With proper feed back system and an electrical actuator, the control is better than 2% of the flow. The controlability is good from some 500m³/hr to 10000 m³/hr.

The valve is simple centre shaft type.

Hi gsuhas. Thank you for your valuable comment. Have you noticed the differential pressure while you controlling. Because i heard that differential pressure is high when we are controlling in butterfly valve.

A certain differential pressure across a control valve will result in a given flow. The flow has no idea which type of valve is creating the differential pressure.

You will have pressure drop (differential pressure) across any type of valve. It is tread of between cost, pressure drop, controlability and the flow characteristic, that you have to choose.

Least pressure drop will be with so called Spear valve.(Not ver standard valve)

Can anybody inform about spear valve?

I would only use a butterfly valve for control when the pipe is too big for other valves to be practical. I've used notched ball valves successfully in some applications and seen b-fly valves work sometimes and not in other cases. Sometimes you need to be careful about the pressure drop across the butterfly valve.

You may want to be sure that your butterfly valve is not controlled with a digital output and actually has an analog signal going to it. Perhaps that is what your coworker is talking about.

You can use a butterfly valve to throttle the conveyed fluid flow rate, and also to open or close the pipeline. One of the simplest valves to use and maintain.

Make sure your new valve has a position indicator. IMHO, with your flow regime by all means equip the valve with a heavy duty actuator motor as well as manual handwheel just in case the electrical service is interrupted for some reason.

Good luck!