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- since 1996 -
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Technical Discussions
Fred raco
Consultant,
RNDT, Inc., USA, Joined Jul 2002, 24

Fred raco

Consultant,
RNDT, Inc.,
USA,
Joined Jul 2002
24
18:40 Apr-16-2013
MT and demag of springs

We have processed several large springs used for passenger trains. We are now having difficulty in demaging them.. Any ideas? Any assistance would be greatly appreciated.

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
20:47 Apr-16-2013
Re: MT and demag of springs
In Reply to Fred raco at 18:40 Apr-16-2013 (Opening).

Reversing/Decreasing DC is probably your best option.

Gerald

 
 Reply 
 
DJ Kallhof
DJ Kallhof
21:45 Apr-16-2013
Re: MT and demag of springs
In Reply to Fred raco at 18:40 Apr-16-2013 (Opening).

A detailed list of the available equipment, and process used to magnetize the springs would be helpful. Blindly suggesting options leaves a bit to be desired.

 
 Reply 
 
Ed T.
Other, ASNT Level III, UT, RT, MT, PT, VT
NDT Level III, Saudi Arabia, Joined Sep 2011, 169

Ed T.

Other, ASNT Level III, UT, RT, MT, PT, VT
NDT Level III,
Saudi Arabia,
Joined Sep 2011
169
06:09 Apr-17-2013
Re: MT and demag of springs
In Reply to DJ Kallhof at 21:45 Apr-16-2013 .

When I did railcar springs we used a 20 point stepdown process using AC coil while beating the ends of he springs with a rubber mallet and it seemed to work for us.

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
13:45 Apr-17-2013
Re: MT and demag of springs
In Reply to Gerald R. Reams at 20:47 Apr-16-2013 .

The gentleman asked for ANY ideas and ANY assistance.

Gerald R. Reams,
ASNT NDT Level III

 
 Reply 
 
Fred Raco, Jr.
Consultant,
RNDT, Inc., USA, Joined Jul 2002, 24

Fred Raco, Jr.

Consultant,
RNDT, Inc.,
USA,
Joined Jul 2002
24
14:41 Apr-17-2013
Re: MT and demag of springs
In Reply to DJ Kallhof at 21:45 Apr-16-2013 .

Spring: 36" long, 12" overall diameter, 1.75" diameter spring wire.
Direct induction at 2000 amps, indirect induction with a 1.5" OD copper central conductor at four locations around circumference, all AC.

 
 Reply 
 
Ed T.
Other, ASNT Level III, UT, RT, MT, PT, VT
NDT Level III, Saudi Arabia, Joined Sep 2011, 169

Ed T.

Other, ASNT Level III, UT, RT, MT, PT, VT
NDT Level III,
Saudi Arabia,
Joined Sep 2011
169
16:40 Apr-17-2013
Re: MT and demag of springs
In Reply to Fred Raco, Jr. at 14:41 Apr-17-2013 .

That is why I posted my experience with springs. Its an idea. Using a wrapped coil with AC current and a 30 point step down process and a little more amperage than used to mag it.
This should be done while striking the spring with a rubber mallet.
If you don't want to try my idea, I can't help you.

 
 Reply 
 
Paul
NDT Inspector,
USA, Joined Mar 2016, 21

Paul

NDT Inspector,
USA,
Joined Mar 2016
21
18:47 May-22-2019
Re: MT and demag of springs
In Reply to Ed T. at 16:40 Apr-17-2013 .

I was searching for the reasoning of why striking an object while demagnetizing the object improves the process of demagnetization. I noticed this technique while reading an operations manual of a refurbished demag coil we purchased. Just trying to understand the theory behind this as I have never heard of such a thing. I found this old post during my search and wondered if anyone would be kind enough to explain this.

 
 Reply 
 
Rick Lopez
R & D,
John Deere - Moline Technology Innovation Center, USA, Joined Jul 2011, 190

Rick Lopez

R & D,
John Deere - Moline Technology Innovation Center,
USA,
Joined Jul 2011
190
22:50 May-22-2019
Re: MT and demag of springs
In Reply to Paul at 18:47 May-22-2019 .

Paul,
I'm not sure of the exact mechanism at play, but you'd be doing the opposite of a well-known method of magnetizing ferromagnetic objects by striking them with a hammer, while keeping the object oriented north-south. I believe the basic idea is that the hammer strikes add energy to the material, which facilitates easy magnetic domain re-orientation. The idea is mentioned in Carl Betz's MT book in Chapters 7 and 17 for magnetizing and demagnetizing. As I recall, hammer magnetization was also featured in Walt Disney's "Unidentified Flying Oddball" movie (1979), which had a magnetized sword wreaking havok in King Arthur's court :)

 
 Reply 
 
George Hopman
Consultant,
NDE Solutions, USA, Joined Apr 2009, 44

George Hopman

Consultant,
NDE Solutions,
USA,
Joined Apr 2009
44
19:23 May-27-2019
Re: MT and demag of springs
In Reply to Fred raco at 18:40 Apr-16-2013 (Opening).

When I teach MT classes, I magnetize two different springs to show cracks and then successfully demagnetize them, but only with Magwerks (Indianapolis, IN) equipment. No other brand seems to work; I'm not sure why. Magwerks also has specialized demag units that use reversing DC and low cycle AC. I suggest sending them a magnetized spring and have them demag it for you and tell you what works.

 
 Reply 
 
NIKHIL H
NIKHIL H
11:14 May-31-2019
Re: MT and demag of springs
In Reply to Fred raco at 18:40 Apr-16-2013 (Opening).

Sir,

Please use AC, and reduce the current by 10 steps.

It will work for your springs.

 
 Reply 
 

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