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Pressure losses due to check valve

Pressure losses due to check valve

Pressure losses due to check valve

(OP)
Hi,
I am calculating the pressure losses through a fluid system and would like to know if the cracking pressure of a check valve must be added when determining the losses through a check valve? Some manufacturer's have graphs showing the pressure losses at a given flow but does this include the cracking pressure?
Thank you,
Gabriel

RE: Pressure losses due to check valve

I can't imagine why it would not include the initial pressure.  You can easily tell if it includes it or not, because the graph would start at (0,0) if it did not include initial pressure.  If it included initial pressure, the graph would start at that cracking pressure plotted above the minimum flow shown on the graph.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

(OP)
Thanks BugInch!!

That answered my question and it is exactly how you said, the graphs start at the cracking pressure!!

RE: Pressure losses due to check valve

You gave me very good clues.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

BigInch,

I agree with your thesis, even if there are around examples of pressure drop chart for check valves showing a pressure drop which could be lower than the cracking pressure of the valve. It seems to me somewhat strange. What do you think about?
 

RE: Pressure losses due to check valve

I don't see it.  Those are log values, so they can't go below zero.  Next pressure drop value down is 0.01 and the next flowrate to the left is 0.1

But, if there was such a chart , I'd say it would be for when it was installed in the vertical->down direction.  If it was for a vertical->up direction, or a horizontal position, I DON'T think I would use such a valve.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

I think the pressure drop in the dark blue section is always 0.5 psi.

Good luck,
Latexman

RE: Pressure losses due to check valve

Works for me.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

If you want to find out if the supplier knows what he is selling ask for some reverse valocity vs deceleration criteria. this is needed when you do you waterhammer analysis.

Reference Fluid Transients in pipeline Systems Pof ARD Throley. Also look at the Delft laboratories or APCO website.

RE: Pressure losses due to check valve

Ya, can't show that on a log-log chart!

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

My apologies, I was definitely wrong: must be tired and need some rest!

RE: Pressure losses due to check valve

What puzzled me is the fact that pressure drop lines go down the dark blue section (that is values lower than cracking pressure of 0.5 psi), while this should not happen. It must be a plot mistake of the manufacturer.

RE: Pressure losses due to check valve

It is correct for the pressure drop lines to extend down below the marked cracking pressure because the marked cracking pressure is specific to a particular valve orientation.  In the example given above, the cracking pressures are given for horizontally mounted valves, presumably for upflow. If the flow is horizontal, or vertically downward, the cracking pressure would likely decrease.  In that case the pressure drop lines would apply for any pressure greater than the actual cracking pressure.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Pressure losses due to check valve

Katmar,

This makes sense.

The lines should be at least dashed in the dark blu area (ah ah I am clutching at straws)

RE: Pressure losses due to check valve

Logically that may be true, but there's no notes on the chart that I saw.  The orientation should be specified unless not horizontal.

But less than 1/2 psi, I really wouldn't care.  I have my analysis software set to solve to +/- 1 psi, and that's too close.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure losses due to check valve

BigInch - Just curious - what software do you use for pipe network analysis?

RE: Pressure losses due to check valve

I'm using Stoner Pipeline Simulator, an Advantica product these days.  Started using it in 1985 connected from Laredo to a mainframe in Carlisle, PA.  A much bigger current version will run on a small laptop today.  It will do either gas or liquids steady state and transients, the thermodynamics, mixture tracking, product batch tracking, Newtonian or non, really almost anything you want to do.  But no multiphase flow.  

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

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