pressure regulator valves 3

[entp]

Hi everyone, I have a simple question about pressure regulator valves.

If there is an existing PRV in a vault, is there an indicator on it showing the pressure differential it's regulating?

Thanks.

 

[bimr]

Probably not. There may be pressure gauges on the device.

You should see if there is a manufacturer's id tag on the valve. With that, you can look up the valve.

 

[entp]

OK, thanks.

Another question, can a given PRV be set to a range of pressure differentials, or do they have to be set to one pressure differential at the factory?

 

[bimr]

My understanding is that you may adjust the valve within a range of values, not just one preset.

http://www.cla-val.com/pdfs/N-90-01.pdf

 

[gerhardl]

PRVs can be of different constructions. Most simple and common is direct acting spring operated (pressure balanced on both sides on a membrane or disc against an additional adjustable spring force).

Second is a pilot (direct acting) construction, basically doing the same, but where a smaller pilot valve is regulating the larger, mainvalve pressure balance.

Now to your question, and perhaps some usable points, assuming your construction is either the one or other of this type.

a) Both should be equipped with pressure gauges upstream and downstream. Install well upstream and downstream to avoid turbulent strech if not already installed or plugs for gauges on the valve.

b) Both valves are normally adjustable within a given pressure range. Adjusting must always be controlled against gauges installed at site.

c) The first valvetype will have a more limitid flow capacity for the same size as the second. The first one will not regulate as fine as the second. Both will normally give increase a bit (1 bar) above the downstream set pressure if the downstream flow is stopped.

d) NOTE! PRVs are always dimensioned on flow and pressure range together. Either if flow is too high and/or too low and/or pressure fall to large, cavitating conditions may occur, and valves will be damaged and/or not operate properly over time.

Conclusion: Alwyas check exactly down to details what you actually have, check condition of existing equipment and allowed operating range, and compare to todays' need.

For older equipment, if overhaul or changes are necessary it is always useful to compare expected lifetime, cost and performance against a complete new construction.

If you want to keep the pressure downstream or upstream regulated between two preset figures you could do this several ways, depending on actual details. Normally you would end up by a valve regulated by external force and signals (motor operated valve) or two separate direct acting valves in combination either overflow valves (highest pressure before overflow preset) or regulating valves.

OK?