further to Chris's comments this is a common question (and even more common
misconception).
I did find an old flange book and that is true many years ago the rating was
150psig @ 500F and 300psig @500F for carbon steel. I have never seen the
other ratings matched.
But as materials and steel manufacturing improved the allowable pressure
rating of the flange
was able to be increased. This validation was done by companies such as TUBE
TURNS and Bonney Forge who had testing and Research depts. Then everybody
took the knowledge for free, reverse engineered the products and the
"researchers" went out of business. Industry had supported the knowledge
base in those early days.
The trend across Older copies of the standard shows this, the last change was prior to ANSI B16.5 1977 for the basic values. (up to 285psi @ 100F) Older codes had 274psi @ 100F.
The other equally peculiar and frequent question is schedule designations.
heres the scoop and its a similar explanation .
The schedule numbers originally referred to an approx expression 1000x (p/s)
(s = allowable stress).
Again the materials and fabrication improved (darn it ... a moving
target)and so the value of S improved, making the formula invalid.
If you take approx a 1938/1939 code and use those values, it comes out about right... up to 10" (standard)(standard was the former designation.)
' 001(780)465-9762
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-----Original Message-----
From: DAVIS MCCONNICO [mailto:tz2@msn.com]
Sent: Friday, May 07, 2004 2:37 PM
To: <a href="/group/PipingDesign/post?postID=BRCbm27LEUUPU-RAC3D8h-cyLQ6TakdevvSzOdp8VklcNdOVjJ10ihDi_fwmBYqAUxwtIQlkWestoDa-ohZoFkkiA58">PipingDesign@yahoogroups.com</a>
Subject: [PipingDesign] Why "Class 150" ?
Ok, all you pipe nerds.
Here's a dumb question.
I'm not an engineer, just a gasket salesman. But I enjoy reading this forum and have enhanced my knowledge thereof. I've asked this for the last few weeks to all my engineer customers and no one knows.
Usually when a pipefitter (in the USA) refers to a "150 lb. flange" he means an ASME B16.5 Class 150 flange. It's amazing how many think the "pressure rating" of that flange is 150 psig. Obviously, that's not the case. It's material and temperature dependent. For example, per table 2 of B16.5, a 304 Stainless Class 150 flange has a pressure rating of 235 psig AT 200 deg. F. But here's my question:
Why DO they call it a "Class 150" flange? From whence was the figure "150" derived?
It's not the weight! It's not the pressure rating! I've even run some numbers from table 2 and it doesn't even seem to be the AVERAGE! (I ran an average on the table for the 4 material groups of carbon steel, which is the highest pressure rated group: 130 psig)
Here's hoping someone can clear up a long-standing and nagging question.
-Davis
Thermoseal Contact Information
Area Representative:
Davis McConnico
South East District Manager
Thermoseal Inc.
Pensacola, FL. 32504
voice: 850 / 477-0960
fax: 850 / 477-0106
email: <a href="/group/PipingDesign/post?postID=SU9Zo5EmK5VaY-9bzvTiLE5UWbw0WQ_fhIyGj9FwhzBoyCdUgfO9DMdVpdyN1Kqm6MBn5fJ7JR2DVIJZ6wchsz84DHgNUPU">dmcconnico@thermosealinc.com</a>
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Yahoo! Groups Links Received on Fri May 07 19:01:00 2004
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