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losses thru a valve

Posted: Tue Aug 03, 2010 5:26 am
by linz
Hi hoping somone can help me understand how to sort out my problem.

We need to insert a sleeve type valve into an air line,either once or possibly at each 20m hose end, so there could be up to 10 valves/hoses in line.

The sleeve valve will create turbulent flow and a restriction, i am trying to work out how much of a restriction, based on the idea that the restriction(s) will be accumulative if more than 1 valve is installed, and there will be a maximum no of valves/ hoses that can be used before there is a performance issue with the air tool.

From looking at the calculator i understand i need to input data, but unsure what set-up is needed to get the input data.

I have at my disposal air receivers and compressors of various size , plus the 1" (25mm) flexible hose the system is based on, plus availability of pressure guage / swiths solenoids and timing devices.

In the workplace where this will be used the compressors are huge and feed in via 6" steel pipes to 1" outlets.

So can you suggest a test setup so that i can get the data to use the calculator, or have i lost the plot.

Thanks in anticipation.

Re: losses thru a valve

Posted: Tue Aug 03, 2010 7:28 am
by admin
The calculator for air pressure drop http://www.pipeflowcalculations.com/airflow/index.htm can be used with value of resistance coefficient - K entered.

Value for K can be obtained from the valve manufacturer or found in literature. If you can tell me more about the valve - type of valve (globe, gate, ball, needle ...) and nominal diameter and seat diameter maybe I can found the K value in the books for you.

Re: losses thru a valve

Posted: Wed Aug 04, 2010 2:15 am
by linz
The manufacture cannot provide the K value. See attached sketch, the air travels along a 19mm dia smooth bore pipe, exiting at 90 degrees thru 9 x 6.5mm dia ports, thru the transfer chamber, a ring shaped passage 19mm ID and 36mm OD, then entering back into the pipe thru 30 x 3.5mm ports. The sketch shows the valve in the open position, i have deleted the oring seals on the slidable transfer chamber.

Thanks

Re: losses thru a valve

Posted: Thu Aug 05, 2010 7:34 am
by admin
This problems in my opinion can be solved only by experiment.
Calculation is maybe possible but with very limited accuracy.

Maybe using numerical methods some better results can be obtained but again, some experiment is also required - that is what I think.