RE: Welding Elbows

With Christopher FEA results, perhaps the SIF pioneered by Markl (in the summer of 1955)will require adjustment in B31.3 (the SIF in b31.1 now appears to make more sense) - the early work of Markl showed that the bend tend to flatten in one of its axis during bending. The result is a reduction of Z since the outer fiber is "pushed" to the NA whcih ultimatley lead to the increased in flexibility.

The fatigue test performend by Markl on welded elbows can be found at Piping Engineering published by Tube Turns and if my memory serves me right it also appeared in the Design of Piping Systems by MW Kellogg Co. Typical failure of the welded elbow based on Markl study is at the welded joint (circumferential cracks).

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]   I
made a quick FEA run on an L-shaped pipe run with a long radius ell and there was no rotation. Uniform temperature throughout so the thermal strain was uniform. Everything changed scale uniformly since the thermal strain was equal. The pipes didn't go oval either. Anyone want pictures or details, let me know.

Answering my own post, I see I wasn't the only one who fell for it.

In a similar vein, Suppose you have a hole in the middle of a square plate and the plate is heated to a uniform temperature. Does the hole get larger or smaller?

Christopher Wright P.E. |"They couldn't hit an elephant from <a href="/group/PipingDesign/post?postID=L-guvr4qzVQIT-EDSOdnl51L1kGZHndP06tI85xptJt-AiYMdsdQeSqMSnw5zFaJtiUxMWZ43G10tYEc">chrisw@skypoint.com</a> | this distance" (last words of Gen. Received on Sun Apr 21 02:53:00 2002