Ceramic Backing Tape

[cmcclain]

While performing welds in accordance to AWS D1.1, how is ceramic backing tape categorized?

Is it seen as steel backing strip?

We have a repair project in which we will be using the ceramic as the backing, and we will be qualifying the welders with a setup as shown in Figure 4.21 (2006 Edition). I would like for the qualification to be performed with the ceramic tape in place of the steel backing. Is this allowable per D1.1?

The repair is of Carbon Steel parts, A36 material. FCAW with E71T-1 filler.

Thanks for the help.

Chris

 

[HgTX]

Ceramic backing is not considered to be the same as steel backing. It is permitted to be used, but not in exactly the same way. The weld would be considered a PJP if you don't backgouge it, unless you qualify the joint as a CJP. See 2.17.1.

Regardless of what you do with the welder qualification, you'll need to qualify the procedure for the non-standard joint per 4.8. And you can use the WPS qualification to qualify the welder who welded the test plate. For the next welder, though...if you're doing a welder qualification I think the code requires you to do the standard specimen, which is independent of the types of joints the welder will be welding. I suppose you could run the procedure qualification again with the next welder.

You have to read the code with a critical eye, though. There are a lot of backing-related provisions that don't specifically say they apply to steel backing but were probably intended to.

Hg

Eng-Tips policies: faq731-376

 

[HgTX]

Update: apparently some clarifications on what "backing" really means are coming in D1.1-2010, due out in April. But I don't know what they are and I'm too lazy to find out.

Hg

Eng-Tips policies: faq731-376

 

[connectegr]

Ceramic backing is typically used when the backing must be removed. In seismic applications (D1.8) the backing is removed and replaced with a reinforcing fillet weld. For non-seismic situations, this is an expensive and unnecessary process. As Hg noted, ceramic backing will be more clearly defined in the 2010 D1.1 (next month). At this time, ceramic backing is not allowed for D1.1 prequalified welds.

Both the procedure and the welder must be qualified for the use of ceramic backing.

http://www.FerrellEngineering.com

 

[unclesyd]

You will need to be aware that CBMs are not a panacea for problem welds, as with backing rings not all welds can handle them. Another not is that many of the styles carry a specification of maximum amperage and are process specific.
A weld joint that uses CBMs needs to a design not a happening.

There is/was a Korean site that had all the information on processes and procedures for welding with CBMs under nearly all standards. If I recall it was put out by the Korean Shipbuilding Org. I posted this Korean as it shows a similar sketch to ones in the reference document.

Check: "CBM Application for Blocks"

http://infosys.co.kr/index_05.html

A US supplier.

http://www.cerbaco.com/index.html