Re: Re: Hydrotest (High point) Vents

From: <Christopher>
Date: Sat Feb 02 2008 - 13:13:00 EST

On Feb 2, 2008, at 3:53 AM, delacruzjuan1977 wrote:

> So when the subject of strenght weld was posted, my reaction is
> that strenght weld has
> nothing to do with seal welding of a threaded joint (between a
> fitting and a valve).

My own take on this is that small welds, be they seal welds or strength welds are more likely to harbor defects of one kind or another if they're done after all the other QA is completed. Small welds (including tack welds) tend to cool a lot faster than larger welds which are subject to greater heat input. They're more highly restrained and when they shrink, there's a greater tendency toward high shrinkage stresses, which aggravates the tendency toward cracking.

The biggest problem is not the cracked seal weld, the problem is the crack itself, which may propagate into the vessel wall. Almost as significant is a what-the-hell-it's not-a-strength-weld attitude toward such welding.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=dNZRUNaH-kcMnCNw5HtP9s78Ig8d2xUNYMbPVOlFzdAaauFi_SfETUxP8dw2jWbTOM7tA9DsSWyc0A">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 Sat Feb 02 13:13:00 2008