Valves as restrictive orifices

[gibsi1]

Can you successfully use a reduced size and/or port valve in place of a restrictive orifice plate? I have an 1.5" sump pump discharge line that is much shorter and of less elevation than originally designed for. The change has caused the pump to operate way off the right side of the curve. I have sized a restrictive orifice plate, but for various reason a valve would a nice. I just don't want it throttled because of past experience with random valves always finding their way wide open when operators make their rounds.

Running a few calcs seems to show that the valve would need to be much smaller than the designed orifice plate to serve the same purpose. Is this due to the smoother flow through the valve serving more as a frictional loss than an immediate pressure drop?

 

[BigInch]

It can be done.

Did you use a globe or plug valve?

I guess you used a full open position Cv for your pressure drop across the valve calculation?

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[GrimesFrank]

To me its one of those, yes it can be done...but why would you?

If you want a non throttling restriction to cause a pressure drop.....you really are wasting your money.

Maybe I'm missing something. The only thing I can think of is you want the benefit to isolate in a shutdown scenario. IMHO you need both for that, sizing down a valve for restrictive purposes is alot of work for nothing.

Do you have stock in a valve supplier? (j/k)

Frank "Grimey" Grimes
You can only trust statistics 90% of the time.

 

[gibsi1]

I really don't want to do it, either. Others in the organization were bringing it up and I wanted to ensure I was correct in my stance to use an orifice plate. It would take a small valve and cumbersome amount of fittings to make the valve work. What is the correlation between orifice plate discharge coefficient C and valve Cv?

 

[Artisi]

Reducing the impeller diameter is a much better solution.

 

[gibsi1]

Reducing the impeller costs us a lot of flow. This pump is in a very "utilitarian" sump application that doesn't need to be exact, but we do need to maintain good flow.

 

[BigInch]

Basic Valve Cv equation is, gpm = Cv * dP^0.5

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com