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Welding a magnetized pipe.

Welding a magnetized pipe.

Welding a magnetized pipe.

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.

RE: Welding a magnetized pipe.

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.

RE: Welding a magnetized pipe.

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.


RE: Welding a magnetized pipe.

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?


RE: Welding a magnetized pipe.

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.

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