Prequalified Ceramic?

Date 11-15-2005 13:27

Duke,
My take on the use of ceramic in your case is that it is permissible. Reason is that you ARE backgouging the second side, now it would be a different case if you did not address the second side(being it was welded from one side only). See Table 4.5(33) states....
" The omission, but not the inclusion, of backing or backgouging. (all of the processes apply)

Also see the 5.10 Backing states....
" Roots of groove welds may be backed by copper, flux, glass tape, ceramic, iron powder, or similar materials to prevent melt through......"

HTH,
John Wright

By swnorris (****)

Date 11-15-2005 13:56

I agree with John. There are text sections of the code which support the position that the welding "shall be performed from one side with approved backing or welded from both sides through the process of backgouging". While Section 5.10 of the code allows the use of many types of backing material, Section C5.10 states that only steel backing is "pre-qualified". The root opening limitations of the pre-qualified, to be backgouged, connections "as-detailed vs as-fit" may draw the attention of a sharp weld procedure reviewer but can usually be a non persuasive argument. My personal opinion is these other backings may be used without regard to qualification when the user intends to remove the backing and backgouge.

By CHGuilford (****)

Date 11-15-2005 22:32

If you can apply ceramic tape to the root, then you have access to the second side (normally). So, to add another way to look at that, backgouging would be required if there is a problem on the root side, such as lack of fusion, or slag entrapment. If the weld is sound then no action is required. The key point is that you could backgouge if you needed to.

Chet Guilford

By Bill M

Date 11-16-2005 15:46

My opinion-
I don't think you have a choice.

I think backgouging is required after removing the ceramic...regardless of visual inspection of the root condition after ceramic removal.

By QCCWI

Date 11-16-2005 16:07

I agree with Bill
You must backgouge after removing ceramic backing plus I do believe the act of bagkgouging makes it prequalified per D1.1.

I do not know if it is true but I have heard about AISC releasing some book called AISC-358 that will back Bill up on what he said.

By CHGuilford (****)

Date 11-17-2005 14:34

So then, how deep do you have to backgouge? If the metal is sound and thoroughly fused all the way to the root, why would you need to?

I did not mean that the second side does not need addressing, simply that if the weld at the root is sound then why remove perfectly good metal? In many seams I have dealt with, the only places that required any attention was where the welds ran over a tack. Those usually clean up easily with a grinder. Naturally, if there is reason to question the welding, the backgouging would go deep enough, but only deep enough, to verify sound metal.

Chet Guilford

By jwright650 (*****)

Date 11-17-2005 15:14

Chet,
I follow your line of thinking. Sound material is the whole objective, which is why I simply allow the welder to brighten the material with the grinder so the third party(inspector) in the field or where ever will see that we "addressed" the second side even though no extra work needed to be done on the second side, in reality.
John Wright

By jwright650 (*****)

Date 11-16-2005 17:11

Backgouging also has a definition that allows the use of many tools that would be considered back gouging. (ie. light grinding, just brighten the material with a grinder to prove that there are no problems with the root)
The joint will most likely get UT or some sort of NDT to verify soundness anyway. I think you need to address the second side even if it is in this manner, in my opinion.
John Wright

By swnorris (****)

Date 11-16-2005 17:33

QCCWI is correct. There is a forthcoming document, Prequalified Connections for Special and Intermediate Moment Frames in Seismic Applications (ANSI/AISC 358). 358 will state that backgouging at the root zone will be required regardless of the quality of deposited metal from the weld root pass.
Although ceramic backing or any non fusible backing may still be used, the (required) act of backgouging makes the procedure take on a pre-qualified status as AWS has always deemed backgouging as an act to meet prequalification status.
I know some who have argued in the past that it is not necessary to do anything on the back side once the ceramic backing is removed, and the backing manufacturer sells the product based on the user not having to backgouge. It has always been our practice to, at the very minimum, do enough grinding, as John said, to prove that there are no problems with the backside.