Difficult to reach weld

Date 08-05-2004 15:48

We are attempting to apply a fillet weld in a difficult to reach location.

If you can picture a 6" Sch80 pipe with a 7/8" thick restriction ring. The ring extends out from the pipe 6". (Like a 6GR test...)

Perpendicular to the restriction ring are two 7/8" thick plates parallel to each other with a gap between them of 1-1/4". The plates are notched so that they fit around the restriction ring and connect to the 6" pipe. Width wise the distance from edge of plate to restriction ring is 7" on one side and 3" on the other. The plates extend out 1' - 5" from the 6" Sch80 pipe forming a hub if you will.

We are able to achieve a fillet weld all around on the first plate that is fitup. But on the second plate, we are unable to reach the inside joint to place the fillet weld along the pipe and restriction ring using either FCAW or SMAW. The problem is not just reach, it is also the welding angle. We are not able to get an acceptable welding angle because of the narrow gap plus the depth.

Hopefully you can picture this condition. And if anyone has any suggestions they would be appreciated. Thank you.
ziggy

By CHGuilford (****)

Date 08-05-2004 16:27

I'm not positive but I might be visualizing your weldment.

Would you be able to go to a groove on the open side of the 2nd 7/8" plate? You might not need to provide a full penetration weld, just a deep enough groove and a reinforcing fillet to get adequate throat?

Can you pre-fabricate a "spool" or stub pipe section, with the ring and 7/8" plates on a bench, and then insert and weld the spool in?

The only other thing I can think of I have never done but have often wondered about. Could you modify your FCAW gun with an "extended" contact tip? I was thinking that some copper tubing could be threaded to replace the contact tip and put in a slight bend at the end for the electrode angle. You could insulate the tube and then reach inside the joint. Possibly, some 0.035" wire would be flexible enough feed through without kinking.
Kind of a "Rube Goldberg" approach but maybe it would work?

Chet Guilford

By ziggy

Date 08-05-2004 17:01

Chet:
I think you have it.
For the second plate, I submitted an RFI to the EOR yesterday with the PJP weld and reinforcing fillet. The architect was here this morning to see the mockup. Still no word from the engineer.
The "spool" idea has merit but I doubt the EOR would accept it. This "hub" is part of a tubular truss assembly, the connecting linkage actually. The pipe section is about 6 feet long with the plates and ring assembly on both ends. (Actually the total number of plates is 16...two plates per truss connection...a total of four truss assemblies meet at the hub...the top plates pickup the upper chord, the bottom plates connect the bottom chord...I only mentioned two plates to keep it simple.)
We were also kicking around an idea about the FCAW. I have asked our welding supplier to make a visit today to talk it over. It might work?
Thank you Chet for the reply.
ziggy

By Malcolm (*)

Date 08-05-2004 21:17

I don't have a hint of a solution for your problem short of dumping it back in the lap of the engineer. Isn't it wonderful when engineers design things without taking into consideration how they can be built?