Magnetization of A 335 P11/P12 during grinding process

[B Osare]

Dear Experts,

 

We have observed that piping material  A 335  P11 & P12 of Super heater Header Tee size 12”& 18” (Thickness 45.00 mm & 65.00 mm respectively)  was magnetized during grinding process at Location (not in workshop).   Can anyone tell us how this phenomenon occurs and how it can be de-magnetize at job location? The weld material is getting cracked after welding. Please suggest the  welding procedure with suitable welding electrodes & what precautions  to be taken during welding.

 

 

Regards

 

B Osare

From National Fertilizers Limited, Vijaipur

[Don Under Survilliance]

wrap the copper coils around the job at location and ground it. it will surely help

 

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[Manoj Singh]

Do preheat before welding do demagnetize it

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[B Osare]

We have preheated up 250 deg C but no result...please suggest the Preheat Temp.

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[Chandra]

Usually during welding, you use earthing connection. Try to add 2 more earthing connections and weld, sure it will demagnetised during welding.

Usually we follow the same for welding of 9%Ni steeel

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[Biplab Pal]

Dear Mr. B Osare,

Can you please provide me the value magnetism strength.

The solution depends upon that value.

Use Gauss meter for checking & check the direction of magnetism.

On Tue, Apr 7, 2015 at 12:36 PM, B Osare <bos...@nfl.co.in> wrote:

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Thanks & Regards
Biplab Pal
Welding Inspector

E-mail:   bipla...@gmail.com
 
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[Hareesh K V]

Dear sir,

We had the issue of magnetism when we had done some modifications in a P11 pipe during shutdown of plant.

What we done is after fitup, we wrapped the welding cable (to be tried with positive and negative cable and wrapping direction as a trail and error method) and welded.

The principle we followed is right hand thumb rule. That is the magnetization developed by the cable should reduce/neutralize the magnetic effect created in the pipe. No of turns of cable will also a factor to increase or decrease the strength.
After welding of 1 or 2 inch length the magnetization will disappeared.

Best Regards

Hareesh K V

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