Re: pressure test thoughts

From: <George>
Date: Thu Sep 08 2005 - 14:37:00 EDT

Chris:
I have run into this a number of times - a mfr. might have a vessel designed and possibly built, but not tested. Customer wants a vessel NOW, and didn't need the full MAWP. So, it was tested and stamped for something less than its actual capability. Agreed, in this time of short steel supply/high cost, this is not so likely. But 20-30 years ago, this did happen. Would think customer would want the max rating, but I've seen plenty of cases where this did not happen. In gas industry, particularly in field production, some amazing things happen, especially when time and money start to conflict. Just the other day, saw a 1440 Psig vessel applied at 200 Psig - not economic, but was available.

George McKinney

• Original Message -----
  From: Christopher Wright
  To: <a href="/group/PipingDesign/post?postID=FMa-BtnD6uz-ZcmUq_tnNKqUo7rMXyBZR9C9uhBDbCzGTqCL3TdqkI1bPt1uFb3sOzagOiLEUDHGQWomLbCITBga90ROVg">PipingDesign@yahoogroups.com</a>
  Sent: Thursday, September 08, 2005 2:22 PM
  Subject: Re: [PipingDesign]pressure test thoughts
  

On Sep 8, 2005, at 12:06 PM, George McKinney wrote:

> At a later date, they wanted a higher rating. So, checked
> calculations, re-tested, and re-certified at the actual capability.
Who re-certifies it? Here in Minnesota you could probably do that as
what's called a 'Minnesota Special' but strictly speaking it hasn't
been re-rated, since it the working pressure is no higher than the
original MAWP.

Why would anyone go the the trouble of testing and stamping for the
lower pressure? Unless the vessel was corroded or damaged the original
MAWP qualifies it for service at any pressure up to and including the
MAWP. No re-testing is required. Had it been damaged and then de-rated?
If so, you couldn't re-rate it until it was fixed. Again, by National
Board rules.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>

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[Non-text portions of this message have been removed] Received on Thu Sep 08 14:37:00 2005