steam pressure conversion

[ChemicalBandy]

How can I determine the pressure of a steam that is given in an old book as e.g.

steam 80# ga

What does 80# mean?
What conversion factor is necessary to convert it into bar or Pascal?

Thanks

Andreas

 

[whammett]

80# steam, is steam at 80 psig. to convert to bar use normal comversion factors from psig to barg.

"Scientists dream about doing great things. Engineers do them." -James Michener

 

[rmw]

Wow, does that question (and answer) make me feel old.

One of our esteemed forum members KATMAR has a freeware that is sweet for doing conversions. Visit him at

http://www.katmarsoftware.com

for a free download.

rmw

 

[whammett]

Thanks for the link rmw.

"Scientists dream about doing great things. Engineers do them." -James Michener

 

[rneill]

I believe the ga stands for gauge pressure as opposed to absolute pressure.

 

[simplemath2]

A little deviation from original post.

I often encountered refinery steam line marked as 50 pound steam. General speaking, Does it mean gauge pressure(50psig) or absolute pressure(50psia)?

Thanks.

Yung

 

[katmar]

In my experience, if a pressure is not labeled as either gauge or absolute then the chances are that it is a gauge pressure. Especially in an in-plant situation.

The only exception is that when a pressure is given in mmHg (millimeters of mercury) then it is usually an absolute pressure. I guess this is because it is usually chemists or physicists who use this unit of pressure and scientific (as opposed to engineering) work generally concerns absolute pressures. Perhaps the unit "atmospheres" falls in the same category.

Of course there are exceptions to these common practices and we should always try to label our pressures as gauge or absolute to remove the doubt.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[MJCronin]

To add to KATMAR's explanation....

Consider the circumstances.....if you are looking at a PID for a process chem plant steam system, "50 pound" steam is only really interesting (or relevant) when the units are in psig.

Lab settings or vacuum systems....possibly different.

-MJC

 

[racookpe1978]

Also - Or more relevant, mm HG (millimeters mercury) or inches of water (both are traditional US standards) are very often used with vacuum systems or low pressures that cross atmospheric and vacuum systems like condensers or low head pump suctions.

Knowing absolute pressures at these low values is critical.

At a 950 psi steam, or in a 4500 psi gas line, the 14.7 atmospheric pressure to gage pressure conversion is (almost always) "assumed" to be made: the gage is always needed to reference gage pressure. That is, psig is the only pressure that makes sense.

 

[katmar]

I didn't include inches of water in my list because that unit is often used in fan design and general HVAC work, where it is always a gauge pressure even if it is slightly below atmospheric e.g. a pressure of -10" water

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[rmw]

Inches of water is also used in boiler furnace pressure measurement too. And, yes, HK, that is closely related to fan pressure measurement too, isn't it?

rmw