Pressure: bar, bara, barg : Where can be found a clarification 7

[ATsampalas]

Hi all,
Where can I find a standard clarification between :
bar ?
bara (Absolute Pressure) ?
barg (Gauge Pressure) ?
The Standard being either : ASTM, ASME, British Standard, Euro-Norm, or ...
Sincerely,
A_Tsampalas

 

[racookpe1978]

Well, a lot of the concern relates to what you are measuring, WHERE you are measuring it, and what the actuall (differential) pressure. (Regardless of whether your units are Imperial =psix - or metric = barx)

Example. A 3000 psig gas tank half-full is 1500 psig, and it won't really matter whether you are measuring that gas at sea level, 1500 meters, or 300 feet. The 14.7 psia (1 bara) of atmospheric pressure is irrelevent. Same case for a 1200 psig steam system.

The little difference of atmospheric pressure on the steam pressure gage as a cold front moves through (or if the steam generator could be moved from sea level to 1400 meters) is irrelevant, but the "value" of that steam going into a -2 psig condenser, a 0.0 psig condenser, or a +12 psig condenser is considerable!

If a pump has a minimum suction pressure of .75 meter, and you only provide 25 cm of water, the "fractions of a bar" you are missing will destroy the pump impeller.

Thermodynamically, you have to use the proper unit(s) for the energies (gas states, vapor pressures, thermal energies, combustion energies) you are concerned about.

 

[BigInch]

It starts making a big difference when you're laying pipe, or driving an SSBN at the bottom of the ocean.