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.



From: "paracelcusbombastusvon**At_Symbol_Here**"  

Date: August 7, 2008 2:37:58 PM EDT (CA)
To: ecgrants**At_Symbol_Here**
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 
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


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?


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

Count on EMC for Loss Control Services

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