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Assuring sealing with bellows for critical control valves

Assuring sealing with bellows for critical control valves

Assuring sealing with bellows for critical control valves

(OP)
Hi mates:
Your opinion or experience:
For a control valve in a vapor anhidrous hydrogen chloride service, (minus 32°F - 170 psig), is it reasonable to use a metal bellow for sealing the stem to the atmosphere, additional to the conventional sealing system?
I think that the efectiveness of a metallic bellow for sealing in a control valve is doubtful, as the bellow is exposed to a continuous movement (due to the modulation of the control valve). So, it will have a short life, I suppose.
Any suggestion?
Thanks
J. Alvarez

RE: Assuring sealing with bellows for critical control valves

The trouble with anhydrous HCl is that any leakage will combine with atmospheric moisture to generate strong acid which may attack the stem and rapidly make the leak worse.

A fugitive emissions bonnet with a dryer/acid indicator on the sniffer port would be the minimum I'd want.

There are some brands of bellows-sealed control valves out there which can give considerable bellows life.  There are also small packless control valves which eliminate the whole problem if your flows are small enough.

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