standard or RP for demagnetizing pipe

Date 01-16-2004 12:57

Did a quick Google search and found these articles that may help your problem. Did not take time to read but skimmed and may have useful info. Probably can use a MT yoke to demagnetize. Use a field indicator to verify.

http://www.prci.com/publications/L51389e.htm

http://www.consultantnet.co.uk/demagart.htm

http://www.gaussbusters.com/ppm93.html

By TimGary (****)

Date 01-16-2004 19:05

thcqci,

Great Links!
Thanks for sharing.

Tim

By Skip

Date 01-17-2004 19:55

Hi Bill:
If your having the same problem I had at a power plant, I sympathise with you.
My fitter and I where altering feed water lines to a boiler, this pipe was A106 gr.B 12" heavy wall with a "J" groove prep.
The process was Tig root with 70s-2 filler wire and fill and cap passes with 7018 A-1.
Anyway it came to tie in all the lines and as soon as I struck an arc I was in trouble. The arc was everywhere except in the joint.
As it turned out we checked the magnetism in the remaining joints with a meter and the thing went off the scale.
We wound up tacking bars 8" long, 2" wide and 1/2" thick all the way around bridging the joint.
The bottom quarter was left open to weld, it worked !
The bars were knocked off as the welding continued, we kept knocking off bars each quarter until the root was closed.
Saved my tail
Skip

By rodofgod (**)

Date 01-18-2004 01:32

Power plants are notorious for magnetism problems,especially when welding in/on the turbine hall or pipes that have been mechanically machined.? When I was welding these type of joints, I would get another welding machine and wrap the cables around the weld joint (5 to 8 times), adjacent to the weld, in an opposing fashion regards polarity-each side of the joint, then join the cable ends together! creating,in effect, a direct short!,then turning on and increasing the amps till the magnetism disappeared

Worked for me,but I know of no 'Standard/Code' that allowed for this!

By Bill A

Date 01-20-2004 04:59

I was able to download the reference from PRCI and it describes a few methods in a very easy to follow format. One of the methods described includes using the wraps of welding cable as mentioned in a message below, but it provides very specific directions that will probably be helpful to anyone looking for detailed guidance. The report addresses end to end butt welds as well as side branch connections in pipe.