Pneumatic and Spring PRV...

[murphymok]

Hi All,

Can a pnuematic pressure reducing valve (200-50 psig) working together with a spring pilot pressure reducing valve (50-15 psig)in the same pressure reducing station?

Thanks in advance.

Murphy

 

[khan101]

Murphy, you have to explain a bit more what is the question?

 

[murphymok]

I have a building that uses a pneumatic pressure reducing valve (PRV)to reduce from 200 psig to 15 psig. It is a rather large pressure drop and the PRV is screening loud because of that. So, I will like to find out whether I can install a spring control PRV before or after the existing pneumatic PRV to make it a two-stage reduction (200-50-15 psig).

I am not sure if I can have a pnuematic and spring load PRV in one pressure reducing station.

Thanks.
Murphy

 

[codeeng]

I don't see why not. Alternatively, you could consider putting a plain orifice upstream of you PRV.

 

[khan101]

That is a normal practice at our plant. We use a spring loaded regulator, which reduces pressure from 100 psi to 20 psi and then we use a pneumatic control loop for regulating the required pressure. So yes, it is a common practice.

 

[gmorin]

Are we talking liquid or gas/steam here??

I agree that the scheme you mentioned would work fine, but before you go ahead, talk to your PRV manufacturer. It's possible he can recommend a multi-stage trim that would do the job within your existing valve body. That way you wouldn't need to mess with the upstream piping.

 

[Joesteam]

This is a very common situation here in NYC reducing the Con Ed steam from 200 down to 15 psig. About 95% of the installations use 2-stage reduction, because it is safer and it is a Con Ed regulation if there are no SRV's. There is NO PROBLEM mixing and matching the types of regulators used. We often replace one pneumatic in a series of two with a pilot operated with no problem, as long as the valves are sized correctly. Also, the rule is to keep the high pressure rating on the valve (and flange) up to and including the second PRV.
It is safe because if the first valve fails the second valve can handle the full pressure drop.