How vacuum regulator works???

[pardal]

Hi all valve people.
I need to control the vacuum level on a suction line.
My vacuum pump works up to 26 inch Hg , it is a compressor.

The suction pressure shall be controled from 26 to 0 Inch Hg

Up today I solve it using a modyfied relief valve conecting its output to the suction line in derivation.
By this way I can control it very good , but it decrease my flow capacity as the control is made by allowing air to enter to the system.
I know how a pressure regulator works , like those at the oxigen cylinders, but I wonder how to do a similar regulator to control vacuum, so no vacuum flow is changed.
I understood about pressure balance in the press regulator.
Maybe I have the solution in front of mine , but I can not see it.

I know that there are a lot of them on the shelf , but I want to build it by my self, I can not even copy from one made, because I have not any one.

Thanks in advance.







Pardal

 

[Lexfabrizio]

A normal pressure regulator controls pressure relative to atmospheric pressure or gauge pressure. You need to control relative to vacuum or absolute pressure. You thus need an absolute pressure regulator which references a vacuum source. You can modify a normal regulator by connecting the area (volume) above your diaphragm (piston) to a vacuum source to force diaphragm to see vacuum. You just need to ensure that the setting screw does not leak into the volume.

I hope this helps

Lex Lex Fabrizio
lexf@email.com