Re: pressure test thoughts

From: <Christopher>
Date: Tue Sep 06 2005 - 18:56:00 EDT

On Sep 6, 2005, at 2:49 PM, aluser2 wrote:

> Dont forget it has to be adjusted by the temperature ratio, again a
> very
> blunt instrument. reducing it back to 1.3 was a good thing... we got
> just the same answers,
> but without putting quite so much unnecessary strain on the
> vessel/equpt.

Actually, the reason the proof factor went to 1.3 is because the Div1 allowables went to UTS/3.5 from UTS/4. The proof factor was reduced accordingly so that you'd have the same margin against yielding during the test as existed prior to the increase in allowable stress. 1.3 = 1.5 (3.5/4).

Adjusting the proof factor for temperature simply insures that the stress reached for the room temperature test is the same percentage of the working stress as would be experienced in service. It is a blunt instrument, but no blunter than the hydrotest itself.

Truth to tell, you'll always get a ceertain amount of yielding in a hydro-test
Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=slIC18vt29B5-SY3OaHl-1nVuAHKDaqd-RuEpgO8NIXeuNmN52VkyyGdYuJfuUJfMtL-jpUhyN-c">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Tue Sep 06 18:56:00 2005