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Psia vs. Psig

Psia vs. Psig

Psia vs. Psig

(OP)
Can someone please tell me the difference between gauge pressure and atmospheric?  Psig vs. Psia.  In laymen terms.

Thank you

RE: Psia vs. Psig

psia is absolute pressure
psig is gage pressure

At sea level one feels 14.7 psia or 0 psig. A typical presure messuring device measures pressure compared to atmospheric pressure, hence psig.    

RE: Psia vs. Psig

Gauge pressure (psig)is the actual pressure above atmospheric, in other words if the gauge reads 30 psi there is actually 30 + 14.7 psi or 44.7 psi. Absolute (psia)is the total pressure on the gauge, or 44.7..Mike

RE: Psia vs. Psig

Just to underline what the others have said, and to address an error in your question...
PSIA is pounds per square inch absolute, NOT pounds per square inch atmospheric.

Jack M. Kleinfeld, P.E.  Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering
www.KleinfeldTechnical.com

RE: Psia vs. Psig

rebel,
JKEngineer's point is very important.
Answering your question as asked:
atmospheric pressure is a specific pressure.
i.e.: has a determined value of
      0.0 psig = 14.69 psia = 1 atm
      AT SEA LEVEL!
The question should have been: what is the difference between GAUGE and ABSOLUTE pressure?

1 atm is the atmospheric pressure at sea level.

Then:
0.0 psia = -14.69 psig (absolute vacuum)
also
psia = psig + 14.69psia

in layman terms:
the absolute pressure (psia) =
the pressure measured by a pressure gage (psig)
 +
the atmospheric pressure in psi at that location (psia), at sea level the atmospheric pressure = 14.69psia.

HTH
Saludos.
a.

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