Re: Why Class 150 ?

From: <anant>
Date: Mon May 10 2004 - 10:27:00 EDT

Hello ALL,

I am not an experience engineer but would like to have a suggession for this one...

Now as Mr.Davis want to know " Why DO they call it a "Class 150" flange? "

I hope my sugession would answer the obvious query that any person would have after knowing that flanges are known by ratings like 150#,300# etc but dont know from where the number 150 , 300, 600 generated..

If u go through the press-temp rating table u will find that max allowable pressure for all ratings flanges are mentioned in bars. for particular temp..so if u see the column of 150# rating with corresponding allowable pressure (bars) at softning temp and if u convert that pressure from bars to PSI u will be definetly go near by 150 and same is the case with other ratings 300, 600. just convert the pressure to PSI at the softening point and u get the rating of the flange...so find it out and see if its the same ? i think great professional & experience persons agrees to it or suggest if there another answer to it..

Regards,

Trainee Engineer ..
(India)

• DAVIS MCCONNICO <tz2@msn.com> wrote:
  > 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=hMsjoP0DrL43Wd_89zEKmVOSX96ASTBxPMs0oLwgbFtJxGbAvGkWD22MZIXeQUuIZ4Kjk2YGb8tFZcybJarYBRcasDMRVg">dmcconnico@thermosealinc.com</a>
  >
  >
  >
  

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