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Date: Thu, 7 Aug 2008 16:59:00 -0400
Reply-To: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Subject: 6 Re: [DCHAS-L] Cylinder volume units?
From: "Harry J. Elston"
Date: August 7, 2008 1:23:46 PM EDT (CA)
Subject: Re: [DCHAS-L] Cylinder volume units?
"SCF" = Standard Cubic Feet
It is the volume of the gas when measured at standard temperature/
pressure inside the tank that has been compressed to the maximum
operating pressure of the tank. It is NOT THE VOLUME OF THE TANK
WITHOUT THE GAS IN IT. For instance, a regular size SCUBA used in
diving will hold 80 SCF of dry air when the tank is at 68 F and 3000
psig. I like my fills "Lake Michigan Cold" and in doing so, can
usually squeeze a few more pounds of gage pressure out of the cold
fill. However, the ideal gas law works both ways and I have found it
a costly experiment in physical chemistry to get that "Lake Michigan
Cold" fill (from a generous dive shop) then immediately transfer the
tank to the bed of a pickup truck on a 100 deg. F summer day.
Careful - different people define "standard" differently, especially
temperature. Some use 0 C, some use 20 C. Standard pressure is
almost always defined as 760 torr, 760 mmHg, 1 atm, 101.325 kPa, or
14.7 psia. However, IUPAC's definition of "standard pressure" changed
to 100 kPa because apparently some folks can't handle the thought of a
unit with the extra 1.325 units of baggage hanging around. (I will
withhold comment regarding certain institutions here. At least NIST
still uses 101.325 kPa.)
The different definitions of standard temperature is a big "gotcha" on
the CIH exam - as they will nearly always put answers for 0 C, 20 C
and 22 C as plausible answers.
If you want to be utterly analysis-retentive about it, you need to
also specify the relative humidity of the gas as well because that
will have some affect on the numbers. However, most folks simply use
the ideal gas law and be done with it.
That's probably more information than you wanted, Margaret.
H
===
From: "paracelcusbombastusvon**At_Symbol_Here**juno.com"
Date: August 7, 2008 2:37:58 PM EDT (CA)
To: ecgrants**At_Symbol_Here**uvm.edu
Subject: Re: [DCHAS-L] Cylinder volume units?
SCF as others have stated is standard cubic foot (feet). With regards
to compressed gas cylinders this does not refer to the physical
internal volume capacity of the cylinder. It refers to the volume of
gas at STP the cylinder will contain once the gas has been compressed
to the "rated" pressure of the cylinder. Example: the standard
approximately 5 foot tall tank contains about 200 cubic feet of gas
compressed to about 2250psi.
Lynn Knudtson
===
From: "Russ Phifer"
Date: August 7, 2008 1:03:14 PM EDT (CA)
Subject: RE: [DCHAS-L] Cylinder volume units?
That=92s an easy one=85 standard cubic feet of gas. This is =93quantity=94
,
not =93volume=94. The =93standard=94 part there refers to temperature
(60=B0F)
and (pressure 30 in Hg).
Russ Phifer
Russ Phifer
WC Environmental, LLC
PO Box 1718, 1085C Andrew Drive
West Chester, PA 19380
610-696-9220x12/ fax 610-344-7519
rphifer**At_Symbol_Here**wcenvironmental.com
===
From: Laurence Stock
Date: August 7, 2008 1:09:25 PM EDT (CA)
Subject: Re: [DCHAS-L] Cylinder volume units?
Standard Cubic Foot
===
From: Jane McNeil
Date: August 7, 2008 1:09:58 PM EDT (CA)
Subject: Re: [DCHAS-L] Cylinder volume units?
standard cubic feet, perhaps?
Jane
===
From: Kent Candee
Date: August 7, 2008 1:20:16 PM EDT (CA)
Subject: Re: [DCHAS-L] Cylinder volume units?
standard cubic feet
Kent A. Candee, CIH
Assistant Secretary
Environmental Health Services Manager
Home Office Risk Improvement
EMC Insurance Companies
Ph: 515-345-2728
Cell: 515-321-5874
Fax: 515-345-2220
www.emcinsurance.com
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