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# How to calculate vaccum pressure ?

## How to calculate vaccum pressure ?

(OP)
Dear all,

I am having a 12 mm diameter piston and cylinder arrangement,Using a handle i am moving the piston upward for 35 mm for inflow of fluid from reservoir against a check valve.
My question is how much partial vacuum pressure is created in the cylinder for the rise of 35 mm movement of 12 diameter piston?
Please provide any formula or sample calculation.

Regards,
Dinesh

### RE: How to calculate vaccum pressure ?

Assuming that the system is leak free, you can use Boyle's law to calculate the air pressure in the bigger volume...

### RE: How to calculate vaccum pressure ?

With a liquid you should get close to a perfect vacuum (or the vapor pressure of the liquid) minus the cracking pressure of the check valve. For a gas it all depends on the "head space" between the piston and the check valve. The gas in this space will be expanded as the piston moves. If you double the volume, the pressure will be half an atmosphere.

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