Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / General Welding Discussion / backer
- - By jim Backus Date 05-30-2015 06:02
I weld flanges to poles
We usually weld the inside then backgouge to good metal and weld the outside.Every weld is U.T.ed.Now we are getting the tops and the diameter is too small to get inside.We are using backing bars.The inspector reads the backer as a flaw and has made us bevel the backer to a point.I don't think this was the intended use of the backer.
Am I wrong
Jim
Parent - - By Superflux (****) Date 05-30-2015 15:17
Is the backing bar a flaw OR? Are you not getting full penetration into the bar?
Parent - - By jim Backus Date 05-31-2015 01:02
He says there should be no indication at all.we bevel the pole,weld the backer in,then grind the pole and backer to a sharp point then fit the flange and weld it out to get full pen.
Parent - - By welderbrent (*****) Date 05-31-2015 01:49
Jim,

WELCOME TO THE AWS WELDING FORUM!!

A couple of questions: What welding process are you using?  What joint configuration (I'm not sure I'm following your description)?  Can you include a photo or tell us which joint from the applicable code?  Oh, yeah, what code are you working to (there must be one since you have acceptance/rejection criteria for the UT tech to go by)? 

I'm going to hold off saying some things that come to mind before I have a little more info.

He Is In Control, Have a Great Day,  Brent
Parent - - By jim Backus Date 05-31-2015 07:43
.052 mig. 30v@280 on the wire.The joint is basically turned into a single bevel v-groove with the flange being the flat side.the flange is 3 ft across and 2in thick with a 16 in hole.
Jim
Parent - - By welderbrent (*****) Date 06-03-2015 02:33 Edited 06-03-2015 22:56
Okay, I think we better start with a very common misuse of terms to make sure we end up on the same page.

You can't have a single bevel v-groove joint.  Short and sweet.  Bevels apply to one member of the joint and 'V' to both members.  So, you have a single bevel or double bevel on one member.  IF you have a bevel on both members of the joint then you have a 'V'.  See attachment.

You mention you have a flat side, so, you have a single bevel groove joint.  And you are using a backing/chill ring. 

Do you have a tight fit between the backing ring and the ID of the pipe? 

Is the backing ring thick enough that you are not blowing through?

edit:  and, how wide is your root opening?  (that can definitely add to Super's comment about lack of fusion to backing)

I'm going to hazard (key word) that at the travel speed you would have based upon the volts and wire feed speed of your process that Super is correct and you aren't getting good fusion and it is showing up on the UT.  Especially if you don't have a good root opening to compound the problem.

Brent
Attachment: groovewelds.png (6k)
Parent - - By Superflux (****) Date 06-03-2015 22:29
Just as I thought,
You are most likely NOT fusing into the backing material...
Parent - - By jim Backus Date 06-05-2015 03:01
My question was about putting a bevel on the backer.to me this changes the joint completely.I appreciate the criticism, but I already know how to pass the u.t.I do 10-15 per week.
Parent - By Superflux (****) Date 06-05-2015 21:41
So you are passing the UT of the weld, BUT the backer is a flaw??? I'm very confused.
Grinding a "point" on the backer is probably not in the joint configuration and therefore the UT tech has no authority to change this (nor do you). It also adds considerably to the cost bid for this job.
- By 803056 (*****) Date 06-06-2015 15:31 Edited 06-06-2015 17:12
I would be concern the UT tech is misinterpreting the display. If he/she plots the sound path carefully, it may be discovered the signal on the display is due to the sound beam passing through the root opening into the backing and back to the transducer.

Moving the transducer back and forth may allow the technician to determine if the signal displayed is a defect in the root or the backing (see attached sketch). A change in sound path should allow the technician differentiate between the defect and the backing. If there is still a problem, a change in the transducer angle may help. At a shallow angle (70 degrees), the signal may not be able to bounce off the backing and back to the transducer (no reflector displayed). A defect, if it is an inclusion, should produce a signal regardless of the transducer angle.  The sound path distance will change due to the different angle, but they should plot the same depth (trig functions).

If the technician is rejecting welded joints after welded joint, all with the same sound path distance, I would suggest a different transducer angle as a check. The defect will still be detected in most cases, unless it is a planer oriented parallel with the sound beam. However, the reflector from the backing may well disappear altogether with the change in transducer angle.

Al
Up Topic Welding Industry / General Welding Discussion / backer

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill