Is there any valve that can be used to change the pressure drop? 1

[Bhupinder1]

I know by using globe valve I can control the flowrate at a constant pressure drop. However, I am looking for a valve that can change the flowrate at different pressure drops. I got a 20 m line with enters to various boilers at different segments. For example, at boiler number 1, 2, 3, the pressure is 20 bara, 18 bara, 16 bara. But I want to have all at the same pressure & flowrate. So, by adding artificial pressure drop at 1, I can bring it down to 16 bara, and at point 2 to 16 as well.

 

[LittleInch]

Bhupinder,

You've answered your own question. Use a Control valve of some sort - globe valve being very common.

Control valves by their very nature are not fixed in one position but can change to match the particular requirements.

What you control the position on is up to you - flow, pressure, temperature, compostion etc. It's still the same valve.

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

 

[Bhupinder1]

LittleInch,

Thanks for your reply. Receiving the control valve (globe) spec, it seems you can only change the flowrate and not the pressure?
Looking at the data below, the inlet and outlet pressure are constant at 1500 & 400 kg/hr. I am looking for a valve that could change both the pressure and flowrate.

 

[LittleInch]

It's the SAME VALVE.Just write another condition with the same flow but different inlet and outlet pressures. If they are not extreme the same valve should be able to do multiple conditions.

Quite frankly if you're asking questions like this you really shouldn't be allowed anywhere near a data sheet or a control valve. Get some help locally to understand the issues.

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

 

[Bhupinder1]

That's what I thought initially that you could control the pressure as well as flowrate. But looking at the datasheet above and a lot of other datasheets the inlet/outlet pressure stays constant and only the flowrate changes. This is a contradictory information. I just need to make sure this valve would do the job. The only way you could control pressure/flowrate is by throttling the valve. So when you throttle it and the pressure stays constant but the flowrate changes, how could you throttle now in a different way that the pressure would also change. By just writing on a piece of paper the inlet/outlet conditions wouldn't change how a valve operates physically?!!

Look at the graph below, the pressure can stay constant but the flowrate changes, the Kv valve changes at different valve positioning. If you could substantiate your answers with evidence it will be helpful, like a proper engineers do!

 

[mk3223]

the inlet and outlet pressure are constant at 1500 & 400 kg/hr.

First, Where is the process conditions from for sizing the valve? How is real the flow rate changed with the same pipe size and pressure conditions?

It can be simple system to meet your design flexibility to have two parallel control valve, one the flow sizing and the other for the pressure sizing. Or, consult with other valve vendors who may specify a proper valve(s) to meet the request.

 

[LittleInch]

On the same graph you posted if you wanted 30l /sec and a 5 bar drop you would need a K value of 50.

Kv changes as you open and close the control valve. Each valve will be sixed for a different min and max CV or K.

Your previous example clearly has inlet and outlet pressures constant but we can't see the system which is controlling those pressures but it isn't the valve on that data sheet

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