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RE: Pipe sizes

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I'm puzzled how Schedule 10 meets the specified diameter and Schedule 40 
does not.  Pipe identified by schedule number holds a constant outside 
diameter for a given nominal size (for 12" and less diameters, the OD is 
larger than the nominal size while 14 inch diameter and larger the OD is 
the nominal size).  The wall thickness and ID vary to make the various 
schedules.  For example the  1-1/2" schedule 10 and schedule 40 sizes you 
refer to both have an OD=1.900".  Schedule 10 has a wall thickness of 
0.109" resulting in an ID of 1.682"  while Schedule 40 has a wall thickness 
of 0.145" resulting in an ID of 1.610".

Bill Cain, S.E.
Oakland, CA

-----Original Message-----
From:	Robert Rollo [SMTP:rrollo(--nospam--at)]
Sent:	Tuesday, October 27, 1998 7:09 AM
To:	'seaint(--nospam--at)'
Subject:	Pipe sizes

I have had a curiosity question for quite some time.  Sure, I know of the 
existance of "schedule #'s" for pipe sizing (SCH 10, 20 , 40 , 80, 120), 
but what does that really mean?  What is the history of these numbers? 
 Whose "schedule" is it?

Despite repeated reminders, I can not seem to get my architects to quit 
indicating 1 1/2 " SCH40 handrails, whick exceed maximum allowable OD. 
 Does anyone out there specify round tube per A500B like 1 1/2 x 1/8 for 
handrails?  I often see 1 1/2" SCH10 for rails, which are compliant.

Thanks in advance for help with this, its driven me crazy for years.

robert d. rollo, PE
Corporate Associate
(806) 747-0161vox
(806) 747-7146 fax