RE: Pneumatic Testing

>I am interested to find that you also have welders who "know".
I've heard on several occasions that specifying radiographic examination is one way to inspect quality into a weld. Seems that a welder who knows he'll have to go back and dig out and repair weld defects is a lot more careful making the weld in the first place.

I've also heard that you always find high quality welds on stairways or ladders where the welder has to stand on completed work to assemble the remainder.

>However I have never had a leak on coded work, and only a couple of pinholes
>on uncoded work. X ray failures are another matter.
A hydrotest really is a leak test, not a verification of structural safety. The proof factor of 1.5 dates from the days of riveted vessels, when you wanted to make sure the joints were tight. It's pretty rare for a vessel to fail completely from one cycle to 150% overpressure, since the corresponding membrane stress would be less than yield. What usually kills a pressure vessel, apart from outright abuse, is fatigue, which typically doesn't show up for a few hundred cycles at least. Every now and then you hear of a vessel rupturing during hydrotest, but not very often.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)