What is 'Cracking pressure'?

by Martin
(San Francisco, CA, USA)

Looking at check valves, I see specification such as this:

Cracking pressure 4 PSI

What is cracking pressure and in this example what does a cracking pressure of 4 PSI mean in a real world use.

Comments for
What is 'Cracking pressure'?

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Jan 18, 2008
 Check valve cracking pressure
by: Jim G

Martin
No flow in a check valve. Most check valves are spring loaded with a ball or flapper in them........air or oil in one side and nothing comes out. Air or oil in the other would open above a certain pressure and start a flow, I think what you mean cracking is when the seat of the check is cracked and flow in the permitted direction starts.
Jan 02, 2008
 Cracking pressure of valves
by: Anonymous

Howdy Martin....

Consider, instead of "cracking pressure" the term "minimum operating pressure".

In a check valve, that means that the valve won't start to pass air until the cracking pressure, or minimum operating pressure has been reached.

Whatever the device is inside the check valve that helps the ball stay on the seat (or the flap to stay closed...whatever) will required a certain amount of PSI to overcome and allow air to pass.

If your air line has 3 PSI in it, and the cracking pressure of the device in line is 4 PSI, you won't get any flow through your line at all until the air pressure exceeds the cracking pressure.

Some applications call for very low compressed air pressures and if the cracking pressure or minimum operating pressure of an in line component is too high, the application will be starved for air. That's why they show the cracking pressure on the valve spec.

Hope this helps. Nice hearing from you.

Bill
Publisher

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