×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Hollow Bead Defect

Hollow Bead Defect

Hollow Bead Defect

(OP)
Gents,

Can someone spare their precious time in answering my below question please ?

Well, we are constructing a 10" Water Pipeline using API-1104 as acceptance criteria.  We are applying a dolly-mix procedure (Root-uphill with E7010 electrodes and rest downhill with E7010 electrodes). Pipe W.T is 9.27mm.  This dolly-mix procedure is due to the pipe ovality problems to avoid the lack of root fusion and root undercut defects.

While interpreting films, we have found an hollow bead defect in the root pass.  our client is telling that hollow bead will not occur when applying uphill root progression welding.

Can someone explain this statement is correct or incorrect with reasons please.

Thanks in advance.

RE: Hollow Bead Defect

Normally the 7010 for the root would be downhand using a drag technique (DC+).

The following is a very general statement and all may not agree. This is based on research done in Au.

Problems with hollow beads begin in the root pass when the primary causes, very high welding currents and travel speed are used. One additional contributor is the high cellulose electrode such as your 7010.

Here is a paper where this was presented.

Cantin D., Bee J., The causes and control of hollow bead in pipeline girth welds WTIA/APIA
Research Seminar, Wollongong, NSW Australia 26 October 1995

RE: Hollow Bead Defect

(OP)
Thank you unclesyd. As you said E7010 for the root would normally be downhand. But since we had applied an uphill root pregression, travel speed would not be that high. Hence, are there possiblities for Hollow Bead to occur in root pass?

Thanks for your time.

RE: Hollow Bead Defect

I've seen it going both ways and checking with some RT technicians they all said they have seen it with either process.
There are secondary conditions that can contribute to the hollow bead defects. One of more prevalent contributors is running (DC +) where there are several papers that state that (DC -) will help prevent same. In V-up some welders tend to take the squeeze off the electrode if using the drag technique. Long arcs with relatively high amperage is supposed to be a prelude to form hollow beads.
At times it can be hard to pin down the exact cause as the biggest variable is the welder.
I've seen it most when a welder has been gigged for wagon tracks and turns up the heat to overcome this problem.



 

RE: Hollow Bead Defect

(OP)
Thank you unclesyd. Finally i got the answer from you.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close