help: control valve self actuating

[Jaimy]

Good day,

We have a self actuating control valve with a complaint that it cannot sustain its set pressure.
The valve is an Masoneilan model 535V with masoneilan 10900 actuator.
Cv: 0.1
actuator max shut off press forw/rev: 220 bar

process data:
medium: hydrogen / gas-vapor
flow max: 40 kg/h
pressure (up): 201 bar-a
pressure drop: 170 bar
density: 14.4 kg/m3
The calculated Cv: 0.04868

Isn't the pressure drop of 170 bar too large for the valve?
How do i know the valve will perform in this application?

Hope you can help.
thank you so much.

 

[LittleInch]

" that it cannot sustain its set pressure"

Is this at some low flow rate or in the duty conditions you have provided? Is there some sort of small volume downstream?

Did you provide a "minimum" flow or any other duty points?
What type of valve characteristic is it - linear or equal percent?

What is it controlling on - upstream or d/s pressure?

What are the variations / mismatch of set pressure?

Pressure drop of 170bar is not unknown.
You have chose a reputable vendor, why would it not work. Double check the input sheet from the vendor and od a quick Cv check yourself if you're that worried.

Generally the issue is not the valve, it's the system you've put it into doesn't allow it to function properly or you're asking it do a 1-100% flow range or something equally beyond it's capabilities.

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

 

[Jaimy]

Good day,

Thank you for the feedback.
I have little knowledge on valve design and trying to keep up.
The valve should control the downstream pressure to approx. 30-31 bar.I have been informed that the valve controls the downstream pressure only to 50 bar but does not drop to the required 30 bar.
Alas there is no flowmeter on the line I could only find the process conditions on a datasheet. The process datasheet does not provide any minimum nor normal flow, just the max flow of 40kg/hr.
The hydrogen flows from a 2 inch line (the valve is 1 inch) into a 8 inch main header discharge pipe.
The valve has a set pressure range of 27.58-51.71 bar.

I'll check the input sheet from the vendor to check valve specs.

Thank you.

 

[LittleInch]

The other possible option then is that the controller spring or diaphragm is broken or that the valve itself has become worn so that even when fully closed, there is gas leaking past the seat more than it should.

Has it ever worked?

Is the actuator fitted correctly, i.e. does it open when it is supposed to close? There are many ways to set these regulators up so it is easy to get the control action incorrect.

This is the regulator manual

http://www.google.co.uk/url?sa=t&rc...EHT2jtgSEcQUPg&bvm=bv.121421273,d.bGg&cad=rjt

If you have the serial number just call masonellian up. I'm sure they will help you out.


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

 

[Jaimy]

Thank you so much!
I discussed this with my mechanical colleague.
The manual is very helpful and gave me better view of the components.
I have the serial number, just waiting on the feedback from them.

THANK YOU!