convert in. to psia

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Postby PotatoNick » Fri Mar 11, 2005 7:31 pm

I looked on weather.com and the atmospheric pressure for my area is Pressure: 29.81 in. what does that mean? 29.81psia? I searched google couldn't find it, searched atmospheric pressure on here and couldn't find it. Does anyone know?
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Postby plasticex009 » Fri Mar 11, 2005 8:04 pm

29.81 inches means 29.81 inches of mercury column <a href="http://www.dwyer-inst.com/htdocs/pressure/ManometerIntroduction.cfm">(read this)</a>. Psi and inches Hg are two different measurement units for pressure so to go between them, you must use a conversion factor.


1.000 atmosphere = 14.69 psia = 1,013. millibar = 29.92 in Hg = 760 torr (mm of Hg)

http://www.convert-me.com/en/convert/pressure
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Postby ethyl » Fri Mar 11, 2005 11:35 pm

Here is some interesting reading about psia and psig
http://www.convert-me.com/en/bb/viewtopic.php?p=1807&

now my question: what are the ratings on pvc pipe? psia or psig
It should not make any difference but i would like to know.
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Postby Dextromethorphan » Fri Mar 11, 2005 11:41 pm

So, 1 pascal = 10millibars? My chemistry book has the pascal for all pressure messurements. Also, I can't stand when anything besides SI units are used...inches....meh!
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Postby plasticex009 » Sat Mar 12, 2005 2:25 am

Pipe pressure ratings are in gauge pressure because it would be nonsensical to use an absolute scale. The pressure rating is the pressure differential between the inner and outer walls of the pipe: Rating = Inside Pressure - Outside Pressure. Outside pressure is assumed to be one atmosphere, so we can say: Rating = Inside Pressure - Atmospheric Pressure. Gauge pressure is defined as: Gauge = X psia - Atmospheric Pressure; exactly the same thing. Note, atmospheric pressure is always represented as an absolute (meaning it has a zero point) pressure (psia).

<s>Yes, 1Pa = 10 millibar.</s> This is the exact reason I posted the link to the page with conversions.
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Postby Freefall » Sat Mar 12, 2005 1:47 pm

Here's one of the most useful pages I've found. Conversion factors for just about everything.

http://www.processassociates.com/proces ... cf_all.htm
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Postby pacogoatboy » Mon Mar 14, 2005 9:05 pm

No, 1 Pa does not equal 10 millibar. A bar is 100,000 Pa, so 1 Pa = 0.01 millibar, or 100 Pa = 1 millibar. Also commonly used is the kPa, of which there are 101.3 in an atmosphere. You'll often find tire gauges in kPa as well as psi.
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Postby Dextromethorphan » Mon Mar 14, 2005 9:51 pm

That's what I was thinking of! The kPa...1atm=101.3kPa=760mm Hg
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Postby plasticex009 » Mon Mar 14, 2005 10:02 pm

What was I smoking when I posted that? It makes no sense at all now that I look at it. :x
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Postby BewareOfDog » Mon Mar 14, 2005 10:53 pm

Over 3 days have gone by, and no further reply from the Author of this Topic. I left it alone because I had a feeling that there was no need to answer his question. In other words, "why did he ask in the first place?"

The only reason I was ever interested in a completely accurate measurement of my current atospheric pressure was because I was experimenting with 4x and higher mixes in a Hybrid. Everyone knows that you can be off as much as 20psig OVER, and your mixture will still be within a 5% range. So what's the point?
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