Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • 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!

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

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

KyleBwelder (Industrial)
6 Aug 07 21:28
Does anyone have any tips on how to weld a magnetized gas line. The tools used to monitor the piping have magnetized it. I cannot weld on the body of the pipe to connect them with a bar. The first bead would blow out until it finally got enough in between the two pieces of pipe to neutralize the magnetization. This unfortunately causes a huge mess which has to be ground off and it takes forever to do. So if anyone knows how to de-magnetize the pipe or anything to make welding it easier I would appreciate it.
metengr (Materials)
6 Aug 07 22:39
Yes. I have dealt with magnetized main steam lines at Power Plants over the years. The key is to introduce an opposing magnetic field to counteract the existing field in the pipe.

The opposing magnetic field can be introduced by two methods; a long welding lead (protected to prevent arcing) that is coiled or draped over the pipe circumference. Start with a low setting and increase gradually after a few minutes. Remove the welding lead and check for magnetism in the pipe.

The second method is a portable de-mag unit that NDT firms or contractors to de-mag large steam turbines or pump cases.
unclesyd (Materials)
6 Aug 07 22:45
You didn't mention the type weld or process your are trying to accomplish this weld with, but here goes.

Change the location of you ground and see if the arc changes direction. If it is a butt weld wrap your ground lead around the pipe on the side that the arc doesn't like. It should take about three turns.
It would pay to demagnetize the pipe if the above fails and if this is not feasible switch to AC.

Here a a little information on magnetic arc blow.

http://archive.metalformingmagazine.com/2001/05/Lincoln.pdf
BigInch (Petroleum)
7 Aug 07 1:48
Are you sure it was the monitoring method, or was the pipe stored in a N-S direction or parallel to HV overhead conductors (or both) for awhile before it was constructed?

http://virtualpipeline.spaces.msn.com

hacksaw (Mechanical)
7 Aug 07 8:45
The subject has been covered before in great deatil, try a search under key words.

Usually, you have a jig in place to align the pipe ends (or various filed fab'd clamps). If not, just tack or clamp a piece of steel across the joint. This serves as a keeper and you should be able to weld normally.

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!

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