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A saphire  is pressed on a copper gasket by a metalic rod which is heated. The assembly is set to full aperture by adjusting a maximum heating power. By switching off the power the valve closes. The heating is adjusted such that the pressure reading of the pilot gauge is kept constant.

@Noel Hilleret, Sir, probably u r speaking about UDV 140 not EVR116. Is it so?

Hoops! EVR116 is a motor driven needle valve

Hi Noel,

 Thank you for the reply. So, can I substitute EVR 116 with a fine stroke Needle valve which is suitable for UHV application? Something like- http://www.lesker.com/newweb/valves/gasvalves_needlevalves.cfm?pgid=0

This item seems to be pricey but I am giving the link just for the sake of comparison.

I understand that I wont have the luxury of the having a set point and all but if my system is not fluctuating much, may be I can use this. Basically my application is to fill porous materials , for e.g Zeolites, with water or alcohol or anything with low vapor pressure- in a controlled manner.

thanks

saurabh

I agree with you that sapphire leak valves are the best but these things are quite costly. I sort of did what you suggested - using the needle valve with a check valve. I am using a simple ball valve instead of the swagelok one. The hysteresis might be a problem. The attachment shows what I finally decided upon.

UDV 140 is no more available. DO u suggest any substitute?

Hi Ranjini,

sorry but I never got this project off the drawing board. So, I am not sure about the substitute .

-saurabh