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#1
11-06-2006, 06:01 AM
 FX45 Guest Posts: n/a
PSI .. PSIG.. PSIA help please

Ok I know that PSI = lb/ft^2 and the G stands for gauge and a stands for absolute. My question is do you convert between the three.

For example I am given a number 50 PISA ... how do I convert that? I don't understand and can't find anything on the net. When solving problems I want to be in PSI, right? So therefor when given PSIG x 144= PSI correct? please help i have the test tomorrow and I don't want a simple conversion messing my mark up.
#2
11-06-2006, 06:12 AM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,452 Rep Power: 13
Re: PSI .. PSIG.. PSIA help please

PSIG is the pressure read from a guage which reads the difference between the pressure in the pipe and the pressure of the atmosphere. PSIA is the total pressure including the pressure of the atmosphere.

PSIG + 1 atmosphere = PSIA
PSIA - 1 atmosphere = PSIG

1 atmosphere is approximately 14.7 PSI, so use that value, or the acutual atmosphere measurement for your location if you have it.
#3
11-07-2006, 07:08 AM
 Unregistered Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

thank you very much!
#4
04-22-2007, 05:53 PM
 Unregistered Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

psia is the absolute pressure

psig is the gauge pressure. It is lower than the absolute pressue by the atmospheric pressure in the room where the gauge is being used.

atomospheric pressure is generally assumed to be 14.7 psi

psi is not specific, but generally assumed to be the same as psig
#5
08-24-2007, 03:47 AM
 Unregistered Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

if psi and psig are same then how atmospheric pressure be 14.7 psi. it should be 0 psi.
I think it is 14.7 psi 0 psig. so, generaly psia and psi are same.
#6
11-04-2007, 11:44 PM
 Unregistered Guest Posts: n/a
how to convert PSIG to Kg/sq.cm

#7
11-05-2007, 04:14 AM
 Grace Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

1 psi = 1/14.5 bar = 1e5/14.5 Pa (or N/m2)

Therefore 1 psi = 1e5/14.5 x 1e-4 = 10/14.5 N/cm2 = 0.6897 N/cm2

1N = 1 kg.m/s2 = 1/9.8067 kgf

I'm assuming you mean kgf, otherwise the units of your conversion would be kg/cm/s2...

Assuming you mean kgf/cm2:

1 psi = 0.6897/9.8067 = 0.0703 kgf/cm2
#8
11-05-2007, 04:25 AM
 Grace Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

Quote:
 Originally Posted by Unregistered if psi and psig are same then how atmospheric pressure be 14.7 psi. it should be 0 psi. I think it is 14.7 psi 0 psig. so, generaly psia and psi are same.
Atmospheric pressure at sea level is 14.7 psia = 0 psig.

psig is pressure relative to a reference point, typically ambient pressure (usually safe to assume 14.7 psia, unless your calculation is for a pressure relative to that in a liquid column, e.g. at seabed conditions).

psi is a unit of pressure difference, hence the common assumption that if a pressure is given in psi it is equivalent to a gauge pressure. Unless it is obvious I would ask for it be clarified as the term 'psi' tends to be a bit misused - usually when the originator does not know if they mean gauge or absolute!
#9
11-25-2007, 05:55 PM
 Unregistered Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

Quote:
 Originally Posted by Grace 1 psi = 1/14.5 bar = 1e5/14.5 Pa (or N/m2) Therefore 1 psi = 1e5/14.5 x 1e-4 = 10/14.5 N/cm2 = 0.6897 N/cm2 1N = 1 kg.m/s2 = 1/9.8067 kgf I'm assuming you mean kgf, otherwise the units of your conversion would be kg/cm/s2... Assuming you mean kgf/cm2: 1 psi = 0.6897/9.8067 = 0.0703 kgf/cm2
so if i have air at 200psi its 214.7psig?
#10
03-03-2008, 10:23 AM
 COWTWNKID Guest Posts: n/a
Re: PSI .. PSIG.. PSIA help please

Psia "absolute" =14.7 At Sea Level
Psig "guage" = 0 At Sea Level If Your Reading Is Sensative To Altitude For Plumbing Or Avaionics Or Even Engeniring This Would Be A Critical Issue 0 Psi Or Psig {same} =14.7 Psia

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