Convert On-Off Valves to Control Valves

[Lowrentstuff]

Background Story:
I'm looking for a control valve that can control the stream to the desired flow. What I found in the domestic market are mostly Actuator valves, an On-Off type valve. I asked some sellers if it is possible to make that actuator to control the stream flow (like with 25%, 50%, 75%, or 100% opening), and then some said yes, while others said no. They said it's possible just by adding a positioner. But I have my doubts.

The Question:
- Is it possible to convert the On-Off valve into a Control valve?
- Does the actuator in the control valve and the on-off valve have different assemblies?
- How can adding a positioner would help?

 

[shvet]

Application: science, military, industrial, civil, domestic? Flowrate, pressure, rangeability, accuracy, delay? Region?

 

[RVAmeche]

Obviously this isn't enough information. But generally I would expect to need a new actuator and positioner for a retrofit.

Whether or not the valve is a good fit for the service is an entirely different question.

 

[LittleInch]

There's a world of difference between a valve which can control flow and ones which only isolate / turn on and off.

So

Is it possible to convert the On-Off valve into a Control valve? - IMHO, no. The valve type used for on/off (ball, plug, gate) is often not suitable for control purposes. So 25,50,75% open will mostly NOT correspond to 25, 50 or 75% flow. You need to know what your valve characteristics need to be.

See

https://www.instrumentationtoolbox.com/2014/03/control-valve-flow-characteristics.html?m=0

- Does the actuator in the control valve and the on-off valve have different assemblies? - Usually yes.
- How can adding a positioner would help? - It gives you feed back on the position of the valve.

If you want or need a control valve, buy a control valve. There are many many versions available on the market. where are you, Indonesia?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Lowrentstuff]

@shvet, I need a control valve for a small project (domestic use). It's applied to small flow rates up to 15 lpm, max pressure up to 5 bar, and it doesn't need high accuracy. What I need is for it can be fully closed, half open, and fully open and affect the flowrates at downstream.

@LittleInch, yeah I'm in Indonesia. While I might find a control valve from the business sales, it's hard to find one from the marketplace, especially with a low price. Moreover, they often think that the on-off valve and control valves are the same thing. At least people here are good at tinkering, but I don't want to be scammed.

Anyway, thanks all for your answer.

 

[LittleInch]

Why not just use two cheap on / off valves and in one of them add a manual control valve (tap or radiator valve) downstream and just open one or the other for full flow or then whatever flow you set on the manual valve. Might be a lot easier and cheaper.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Lowrentstuff]

@LittleInch, Thanks for the suggestion, but I don't want to lose the idea of automation control in the system process.

 

[Compositepro]

Solenoid valves can be used as control valves using time proportional control or straight digital control with two identical valves. One valve open is half-flow, two valves open is full flow. If waterhammer is an issue, add a pressure bladder tank as a capacitor to damp the pressure spikes.