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# Estimating pressure downstream a needle valve

## Estimating pressure downstream a needle valve

(OP)
Hello,

I've been wondering whether estimating the pressure downstream a needle valve is possible, with given data.

I've attached the schematic to this post.

The fluid is lubricating oil, and the pipe material is SS with SCH 10s.

Since the valve is manually operated, I'm finding a way to model the effect challenging.

Can you help me with that?

Roberto

### RE: Estimating pressure downstream a needle valve

Doesn't the downstream condition set the downstream pressure for the desire flow rate?

### RE: Estimating pressure downstream a needle valve

For a good estimate of the pressure at the end of line, it needs some data, such as the line length, Cv of the needle valve, dP of the flow meter, etc.
The sketch didn't have enough hope to solve it.

### RE: Estimating pressure downstream a needle valve

The valve is likely where most of the pressure drop is. Simply get the model number from the valve, google "model+Cv" or similar to get the Cv curve. Different manufacturers show this differently, but it should be relatively easy to get the Cv at the flow you have.

Once you have Cv, you can calculate the pressure drop. Here's some more information on Cv https://en.wikipedia.org/wiki/Flow_coefficient.

Jim Breunig P.E.
XCEED Engineering
Mechanical Engineering
FEA Consultants

### RE: Estimating pressure downstream a needle valve

3D Dave.[thumbsup]

je suis charlie

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