Tong,

WELCOME TO THE AWS WELDING FORUM!!

Now, I am not great at understanding some of our bi-lingual members, sometimes sentence structure and word choices do not mean the same to me as what you may have intended, so be patient while I go through some things and try to make sure I cover all the ground you need.

1) Make sure you understand that this table is for the essential variables for qualifying a PQR.  It has nothing to do with pre-qualified procedures or with qualifying/qualification of welders or what they can then do after being qualified. 

2) If you qualified a procedure by using a backing bar, then, if you remove backing from the welding process you need to qualify another procedure.  If you qualified by backgouging before welding the opposite side then want to weld without backgouging, you have to qualify another procedure. 

BUT, if you qualified without backing or backgouging and want to include one or the other or replace backgouging with backing then you can use the PQR already tested, approved, and recorded.  You need NOT go through the PQR process again.

See, OMISSION requires new PQR; INCLUSION is good to go without changing anything.

He Is In Control, Have a Great Day,  Brent

Sorry, I got interrupted and wasn't sure how long I would be.

So, next question, backing materials. Starting at the beginning, in Clause 2.17 we find that backing other than steel must be qualified to Clause 4 requirements for PQR's.

The question on my part then becomes, are we talking about backing for the welder after he is qualified or backing for the PQR?  Backing other than steel must be qualified with the Clause 4 PQR system.  Now, that is for backing left in place with no work done from the other side.  According to a technical inquiry answer published a while back you can use backing other than steel if it is then removed and cleaned by backgouging then welded from the other side; such as moment connection welded from the top then cleaned and welded from the bottom with a 5/16" fillet weld.  No need in that case for a PQR or special welder qualification to use ceramic backing, remove it and weld opposite side. 

Now, I don't see where changing backing material, other than steel, is an essential variable.  And, since steel is pre-approved, you can go to it anytime.  But, if you want to use the other backing materials listed then you must qualify one of them.  So while a change in backing is not listed as an essential variable in the table it is stated as not being pre-approved in Clause 2.17. 

You start out asking about Table 4.5 and then say that you qualified using backgouging.  So I think you are looking at the wrong table to see what you as a welder can and cannot do.  Before I ramble on too much I think we need to get a more distinct direction from you.  But the welder is good to go if he is qualified with backgouging or with steel backing.  It is the procedure that must be qualified to use other than steel, if, it is to be left in place. 

Let's go this way, IF, we are talking about you being qualified as a welder and what you can now do, YES, you can use any of those backing materials as long as there is a PQR/WPS for any backing that is not steel that will be left in place and only welded from the one side.  YES, you can weld by backing or backgouging if you originally qualified with either method.  NO, you may not omit both backing and backgouging, it is one or the other. 

You need to reference Table 4.12 if you are looking for essential variables for Welder Qualification.  It says 'omission' of backing if it was used for the qualification needs to requalify. 

I'm getting too many interruptions so I probably didn't make much sense here.

Brent