Full Vacuum Service? 1

[Manolo3]

Newbie question:
When manufacturers mean 'full vacuum service', are they referring to 0 psia (0 inHG)?? I've seen some specs that mention 'full vacuum service' as 29.9 inHG. Maybe they use atmospheric as the beginning of vacuum.

Just checking.
Thanks

 

[unclesyd]

Full Vacuum service means what it says any way you measure it. If you design for full vacuum you can usually get a positive rating for the vessel.
Our original vessels were F.V. and 15 PSIG while the later ones were designed for F.V. and 60 PSIG

 

[Montemayor]

Manolo:

Vacuum, in the truest sense, should be measured in Absolute pressure. This is a pressure value measured from absolute zero pressure, i.e., from an absolute vacuum base starting point. Note: often some scientists and engineers are delinquent in using the term "vacuum" when they mean a negative value from the base point of atmospheric pressure. This is often results in confusion and misunderstanding. Absolute pressure is the recommended usage because it is precisely that - absolute.

Here are the equivalents of vacuum measurement units:
1 Atmosphere = 14.696 psia
= 101.325 pascals
= 760 mm mercury
= 760 torr
= 760,000 microns mercury
= 29.94 inches mercury absolute (@ 32 oF)

1 Bar = 14.5 psia

I hope this helps you out.

Art Montemayor
Spring, TX