Attachment to pad, or pad around attachment
Attachment to pad, or pad around attachment
(OP)
A client has supplied a design of a 15"H x 12"W temporary support lug welded to a 30"H x 30"W x 1"thk pad to be welded to 3/8" thick support skirt. There is a 14" moment arm on the load. Most times we would weld the lug to the shell, then cut the pad to fit around the lug, and weld the pad to the lug, and of course weld around the outside of the pad. We feel this is a better attachment to eliminate the kind of suction cup effect of welding the lug on top of the pad. Does anyone know of any guidelines for such an application. When one way should be used in leiu of the other by Moss or Bednar. Thanks





RE: Attachment to pad, or pad around attachment
Weld the external attachment directly onto a solid (read: do not cut holes to fit around the attachment) repad. the whole point of using a "REINFORCEMENT" pad is to reinforce the shell thickness so that the combined thicknesses can resist the local bending moment generated by the external attachment (read: lugs, clips, etc.).
If you actually done what you said you've been doing, please inform you previous Clients of this and fix the problem before a failure. I do hope I am wrong when reading and interpreting your message.
RE: Attachment to pad, or pad around attachment
RE: Attachment to pad, or pad around attachment
RE: Attachment to pad, or pad around attachment
By using the welding detail described by cycguy's method, I'd check the local stress at the edge of the lug using a shell thickness of the shell, ts + thickness of pad, tp.
The local stress at the edge of the pad would be checked by using the shell thickness only.
RE: Attachment to pad, or pad around attachment
RE: Attachment to pad, or pad around attachment
IMHO, the most common and practical way is the "lugs on pad" because it is easy to fabricate, weld, inspect and NDT.
RE: Attachment to pad, or pad around attachment
With the lug only to the pad, the load goes to the shell through the pad OD dimension, but you also have to check the lug-to-pad for tearout, etc. But if you had a stainless shell & a steel lug, the pad could act as a "poison pad" too