Magnetism in pipeline 1

[Inchtain]

Dear colleagues,

I wonder about the possible techniques to overcome the residual magnetism in a pipeline during welding!

By the way, from where that some underground or above ground pipes become magnetized?

Thanks for your continuous support.

Best wishes,

 

[1503-44]

Pipe can become magnetised usually by storage with a North-South alignment with the earth magnetic field, or parallel alignment and close proximity to HV electric power lines. Earth Magnetic fields are not always north-south, so check a magnetic compass and store pipe with an East-West alignment. Store pipe as far away from HV lines as possible and always perpendicular to the line itself.


Lots of suggestions how to demag here,

https://duckduckgo.com/?q=demagnitize+oipeline&t=brave&ia=web

 

[LittleInch]

Look up "de gaussing"

I've seen welders wrap their cables around the pipe(s) when welding to generate a magnetic input to prevent the arc from going sideways, but not sure how effective that is.

Not usually too difficult to de-magnetize pipes though.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

By wrapping cables and pulsing current in decreasing increments in reversing directions does work well.
AC demag is usually easier and better. Sets are made to do this.

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P.E. Metallurgy, consulting work welcomed

 

[saplanti]

Here is a fabricator recommendation similar to others above.

https://www.thefabricator.com/thewe...-to-demagnetize-pipe-to-make-welding-possible

 

[EdStainless]

Just a point of clarification. Your issue is with magnetization. All steels are ferromagnetic and that part cannot be changed. They do very a lot though in how much field they can retain when they are magnetized.

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P.E. Metallurgy, consulting work welcomed

 

[Inchtain]

Thanks all for the above discussions.

I would like to know exactly which cables negative? grounding cable? to wrap around? and at what distance from the welding grove? and how many wraps required? and how to reduce the current?

Can we have clear steps that have been applied and succeeded using DC equipment?

Best regards,

 

[SJones]

See if these results help: Google Search Results

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[LittleInch]

That link by saplanti gives you most of the answers. Any experienced pipeline welder should have seen this before and is in control of current and can see the weld arc.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Or if that doesn't work, maybe this,

 

[gtaw]

You can try this link for an article on demagnetization:

https://www.nxtbook.com/nxtbooks/aws/it_202005/index.php#/p/16

There were several posts on this subject right here. A quick google search will provide the links.



Best regards - Al