Scarf joint on 1" steel plate

Date 01-04-2007 05:21

I would appreciate opinions on this matter.
I am concerned about the design of an assembly I have been tasked to weld.
What I have is a steel round base of approx. 5 feet in diameter and 24" in height made of pipe or rolled plate, with a top plate 1 1/2" thick, a bottom plate 1" thick and gusseted approx. every 8" around the circumference. The bottom plate has been beveled.
This base is supposed to be attached to a 10 foot by 10 foot 1" thick plate with a 45 degree bevel through the full thickness by means of a scarf joint.
This base will hold a structure that weighs about 20 tons. It is about 70 feet in length and 20 feet wide. and will rotate on a large gear on top of this base.
Maybe I am worrying for nothing or this joint design is seriously inadequate.
I think that overlapping plate 1" in thickness and welding the seams will provide for a very weak joint.
My opinion is is that this should be a full penetration weld.
Please give input. If my explanation is not clear ask questions and I will try to clarify.

By CHGuilford (****)

Date 01-04-2007 14:33

From what you describe, I have seen similar pieces made that way. I would assume that a qualified engineer reviewed the design of the parts you are dealing with, at least I hope so. You will probably see an approval stamp of some sort on the drawings and if that is the case, I would do exactly as asked.

It is good to ask questions though, that's how we learn. Sometimes the forces acting on a weldment are coming from a different direction than we would think they will. The welds are determined accordingly.
Something you might want to look at is the "Welding Design & Fabrication" magazine; there are articles written by Omer Blodgett that address engineering aspects of welding and I think they are accessible online. John Wright posted some links to the magazine some time ago but I have not looked for that since. At any rate, those articles won't tell you enough to become a welding engineer, but they do give excellent insight as to why welds are sized and located the way they are.