RE: Re: Reinforcement Pad Weep hole

On Sep 13, 2005, at 11:17 AM, Tony Paulin wrote:

> When we've seen this happen, the weld was started one day, and finished
> another, allowing water to collect in the pad/vessel space. Evaporating
> water during PWHT caused bulging.

Again--how do you know that the distortion wasn't caused by the welding heat? Are you telling me that any steam or hot air couldn't get out the same way the water got in? Anyone ever done a couple of simple calculations on the pressure it'd take to bulge a doubler? And whether the water would even evaporate at such a pressure? And what would happen to the pressure 10 minutes later when the weld cooled down?

>> It doesn't happen that often fortunately, but when it does the bulges are large and concerning. Water collects in a partially filled space over night or due to rain impinging on the partially completed weld. When the weld is finished, the rain water is trapped in the space in between the pad and vessel, or in the slip-on flange space, and not heated when the weld is completed, because the weld is far enough away from collected liquid that it does not evaporate. The bulging occurs during post-weld heat treat or when the line is put in hot service.

>> We have seen two failures of this type in the last two years. Received on Tue Sep 13 21:45:00 2005