using a welding rod that requires backing
using a welding rod that requires backing
(OP)
i need some guidance .every one knows it's common practice in tank building/vessel manufacture to weld from one side ,backgouge then weld from the other side (following Section IX welder and welding procedure requirements ) .
my question is this ; if the procedure being used calls for the SAW portion to HAVE backing ,is it permissible to use SAW to actually MAKE the backing with weld metal on one side ,then gouge from the other side and fill the joint up ? it seems like a logical approach but i dont know if it is acceptable according to Section IX. (using an electrode that calls for backing to MAKE the backing ,chicken and egg kinda stuff )
any help and applicable code references would be appreciated .
my question is this ; if the procedure being used calls for the SAW portion to HAVE backing ,is it permissible to use SAW to actually MAKE the backing with weld metal on one side ,then gouge from the other side and fill the joint up ? it seems like a logical approach but i dont know if it is acceptable according to Section IX. (using an electrode that calls for backing to MAKE the backing ,chicken and egg kinda stuff )
any help and applicable code references would be appreciated .





RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
In your case making an open butt weld with SAW can be tricky with some type of backing.
Have you looked at a ceramic or fiberglass backing tape for the SAW?
Can you describe your joint?
RE: using a welding rod that requires backing
thanks again folks
RE: using a welding rod that requires backing
Right be before I left work there were 2 large SS,1/2" being fabricated with the exact same procedure you are looking at. The welding machine accomplished 90% of the welding from the outside and the weld was finished from the inside.
RE: using a welding rod that requires backing
Joe Tank
RE: using a welding rod that requires backing
what i am trying to establish is the following ; is this first SAW bead which is completed without backing (even though the procedure calls for backing ) and is then gouged from the other side compliant with the weld procedure ?
If this whole approach is legitimate (and i believe it is ) can someone walk me thru some references i can use .
eg ; does the fact that we removed the unbacked SAW bead somehow 'make it all right ' to weld without backing ?
i hope i nailed the explaination this time , thanks folks
sf
RE: using a welding rod that requires backing
The SAW process requires backing. You may choose base metal, weld metal, ceramic or flux, but it has to have backing. The practice you describe is very common and is considered to be a weld made with backing. The backing being base metal.
RE: using a welding rod that requires backing
Going a little further. Look at QW 254, Welding Variables for SAW. Note that QW 402.4 applies as a non essential variable for the deletion of backing. Now turn to
QW 402.4 and note the second sentence.
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
' Double welded groove welds are considered welding with backing'
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
Two plates butted together welded from both sides is considered a joint with backing. Of course, you have to have a process and parameters that allow you to deposit a weld properly. We sometimes 'seal' the joint by depositing a layer using the FCAW or SMAW process to support the following passes made by the SAW process. The joint is still considered one with backing. It would not be considered a joint with backing if you use a process to weld from one side only.
Chicopee,
I'm not sure what you're referring to when you say using weld material as a backing strip, but, in the real world of vessel manufacturing backing strips are a last resort. It's much more cost effective to butt two plates together with the appropriate bevels and land, weld one side and backgouge to sound metal, as opposed to welding from one side. For one thing, most customers and designers for that matter, don't want permanent backing strips, and if you have to remove the backing strip, you'd be way ahead to follow the process outlined above.
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
'seal' (can be done with or without backing -as usual ) , THEN followed by a SAW pass(es )because the SAW requires backing , the whole backgouging from the other side is a red hering in this discussion .
my issue since i started this thread has been that by not putting that 'seal 'between the plates before using the SAW process we are not following our procedure or Section IX .
further to that backgouging and welding from the other side doesnt somehow magically fix the issue of welding across an open seam with SAW wire .
what i am looking for is a code reference /interpretation that either agrees with /disputes what i am saying ;that is backing means solid pieces . no holes even if they are just small skinny ones !
let me know what you think
sf
RE: using a welding rod that requires backing
The only reason we seal the joint is to avoid burning through while welding with the sub arc. 'Small skinny' holes don't matter to us if the process is capable of welding over them without burning through. In some cases the sub arc can handle joints with small gaps if the land is sufficiently thick and other minor adjustments are made.
Instead of placing a 'seal' pass from the backside of the joint, what if you were to put your first pass in using a lower heat input process, like stick or fluxcore, would you consider that welding without backing just because you're weling over some small gaps? The answer is no. The weld would be made with backing because you're not trying to make a weld from one side.
Have you reviewed QW402.4?
The matter can be summed by asking, Am I making a full penetration weld from one side only, or am I going to back gouge and weld from two sides? If you're back gouging and back welding, you're making welds with backing.
RE: using a welding rod that requires backing
Backing? which you say you already have, then you specify the backing material as metal or weld metal and as long as you use the same weldmetal(fillermetal)you are allowed w/o having a combination weld.
I guess you can have a WPS with weldmetal and get the bless from your AI. Be sure you do not get cought in a review...
withiout the proper docs.
I agree with JoeTank on this one.
RE: using a welding rod that requires backing
The only time that you can not get around using backing is when welding annular ring plates or doing butt-welded floor plates. With no access to the opposite side for back gouging, you MUST use a backing bar.
RE: using a welding rod that requires backing
RE: using a welding rod that requires backing
his/her procedure will allow for metal and what type of metal or weld metal and what type of metal, if the weldmetal is the same rod/wire just say it.
in the procedure...
you ave to know what you are doing with the paperwork or ask your AI or ... if the AI doesnot know then you ask the AI supervisor or seek help... yes pay a little bit for consulting and you will get the best answers.