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- since 1996 -

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Technical Discussions
Mehdi Eskandarzade
Mehdi Eskandarzade
06:08 Nov-18-2009
Magnetic Particle

Hi,

I have MT device of yuke. however I have not any manual for that. I have spray type and dye magnet particle. is any one can help me how to use it. I use particles after the device is on, however the particles have not effectively gather beside of the crack.

Best Regards,

    
 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 298

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
298
08:26 Nov-18-2009
Re: Magnetic Particle
In Reply to Mehdi Eskandarzade at 06:08 Nov-18-2009 (Opening).

Hi Mehdi,

Normally people who do NDT have training before they use the equipment. In fact most cases require training and certification.
However I will give you some advice to help you get started.
You say you have "Spray type and Dye magnet particle".
This is confusing because Dye test is not used with a yoke.

Firstly you can only use the yoke to crack test if the part can be magnetised. In other words, when the yoke is switched on, is it pulled towards the part? If not, you cannot test it.
Normally you would use a (white) contrast paint on the part (or area of the part) to test, and then put the yoke on, switch it on and spray ink lightly around the area whilst the yoke is still on. Stop spraying the ink, then switch the yoke off.
The ink has small "magnetic" particles that are attracted to the crack, but they will also settle out in the spray can, so you will need to keep this well agitated (shaken) to keep them in suspension.
Your yoke will only find cracks that run in the direction between the feet of the yoke.

Some systems use powder particles and not an ink, and some use fluorescent particles that need an Ultra-Viloet lamp to show the cracks.

There. That was a Magnetic particle test lesson in 5 minutes. Look at what you have got, and if it is like I described above, and the yoke works, try it.

Godfrey

    
 
 Reply 
 
Mehdi Eskandarzade
Mehdi Eskandarzade
10:23 Nov-19-2009
Re: Magnetic Particle
In Reply to Godfrey Hands at 08:26 Nov-18-2009 .

Dear Mr. Hands,

Thanks a lot for your useful information. I do like guides, however the particles produce small collonies in variety of areas, it means that determine the correct indication from false or non relevant indication is very deficult. is it common in MT test?
how can I find that the particle collonies is due to the crack?
Best Thanks, Mehdi

    
 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 298

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
298
12:20 Nov-19-2009
Re: Magnetic Particle
In Reply to Mehdi Eskandarzade at 10:23 Nov-19-2009 .

Dear Mehdi,
Yes it is common that indications are seen from non-cracked areas, especially in Magnetic testing.
This is the main reason why it is normally necessary to have training and experience before anyone can start crack testing.
I would certainly recommend that you follow a training course, which has to include a lot of practical experience before you start using the equipment.
Without it, you run a risk of either missing cracks, or else declaring cracks in parts that are not cracked.
It is normally accepted that a minimum of 12 hours theoretical training and 1 month practical experience under the direct supervision of qualified personnel are required.
You may find that there is a requirement for certification or else for more training and expereince specified in the testing that you are trying to perform.
There are training courses available in many countries world-wide, so look on the Internet to try and find one near you.
With my best Regards,
Godfrey

    
 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
12:22 Nov-19-2009
Re: Magnetic Particle
In Reply to Mehdi Eskandarzade at 10:23 Nov-19-2009 .

Hello Mehdi

You appear to be knowledgeable about inspection from your use of the corrrect terminology, i.e. false and non-relevant indication.

Your posts indicate that you have a cracked test piece but you are not happy with the nature of the test ppiece crack indication arising from application of the magnetic field and particles. If this is correct then you should check your yoke (lift test), your ink (settlement test) and your test piece - (gauss meter for residual magnetism). Thoroughly demag and clean (ultrasonic cleaning works very well) your test piece to ensure there's no residual magnetism.

The ink would be my primary suspect due to the clumping. This can caused by residual magnetsim of the particles - (a bad batch of particles with too high retentivity or contamination). Look very carefully at the settled particles after the test to check for any evidence of clumping or contamination away from a magnetic field. If clumps are evident and you have a demag coil pass the bulk ink through the coil several times - always the same direction and always careful to take the container a couple of meters along the axis of the coil, then retest. If clumps persist or you dont have a coil I suggest obtaining a new ink and trying that on your test piece.

BTW standard practice is to apply the magnetising field continuously from a few seconds before until a few seconds after ink application to encourage particle movement. Dont forget to test at mutually perpendicular directions.

    
 
 Reply 
 
Mehdi Eskandarzade
Mehdi Eskandarzade
15:27 Nov-20-2009
Re: Magnetic Particle
In Reply to Nigel Armstrong at 12:22 Nov-19-2009 .

Dear All,

Now I have some view in hand to strat. Thanks alot for your guides.

Best Regards, Mehdi

    
 
 Reply 
 

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