Control Valve Sizing

Pick up the phone and discuss the problem with the local friendly valve distributor.

Back pressure?,... you mean from the systems curve? or the Cv of the valve....

Just use a really big, shiny one, with a handle.

You should consider that the near-closed differential pressure across the valve this high (as in boiler feed pump back-pressure, perhaps?) can add much to the torque required for the valve operator. If you do no buy the most robust valve and operator recommended by the suppliers for the task at hand, it will fail early, and whoever buys this plant will have to turn this into a hand operated valve (if they can find a wheel large enough). Make sure the valve and operator gets installed correctly, so that the limit switches are not by-passed with jumper wires at any time. Simply having the valve keep ramming all the way shut until it trips the operator is not what I would call good practice.

It doesn't look as though a flow through the valve is possible...

In my experience, backpressure is immediately upstream of the valve, which would also be the inlet pressure. You have given two different values for this (5 kg/cm² and 9 kg/cm²)! Maybe I'm missing something?

Is the process fluid a gas or a liquid?

Why have you determined that a globe valve best suits this application?

What we have here is a failure to communicate.

The last two words of that phrase are not necessary.

Or to add: "...waiting to happen."

Thanks Lyn, for pointing out the redundancy of that previous statement of mine.

Not being a Bible reader, I vaguely remember some reference in there about suffering fools gladly.

I wonder if this is what the author was referencing?

Are you sure that is what is says? Not that we don't already suffer....fools.

Back pressure is not normally used to describe valve design differential pressure, so perhaps a translation problem, inlet pressure, discharge pressure at full design flow. Back pressure valves are sometimes spring loaded check valves, where controlled flow yields a certain pressure at the control point, which you could construe to be the inlet of the valve. Used in the OP context, I would perhaps make an incorrect assumption that the pressure referred to a 'back' was the pressure at the valve discharge at full design flow...(?)

(U.S. valve sizing person 15 years practical experience mostly liquid)

Delta P..... are you using pumps?
If so what type of pumps, where are you using them?

It would seem to me you are hinting at a flow control valve or choke valve!

Could you provide a sketch of the fluid circuit? There is a bit of uncertainty and a sketch might make your arrangement more clear.

He has one, but it is a bit sketchy.

It might not exist. After all, were it to exist, a discussion with the local friendly valve distributor is all that it needs to solve this problem. Can CR4 readers conjure one up in its absence (rhetorical question - NNTR)? Most unlikely.

Here are some unknowns:

• Line size
• Temperatures, of both wetting fluid and ambient
• Flow rates
• Wetting fluid
• Line type specification
• Line insulation
• Location of valve
• Orientation of valve
• Actuation of valve
• Connection arrangement between valve and line
• Position detection arrangements
• Quantity of valve required
• Shipping destination
• Etc.

All this is the domain of the valve distributor.

"The amount of use of the telephone is inversely proportional to the number in existence." - PWSlack

<...we...> So there are several individuals there, and no-one knows how to solve the problem. How extraordinary. Their best bet is #3↑.