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Technical Discussions
Derek
Derek
22:50 Feb-27-2017
Magnetic Particle Weld while Induction heater is running

I have run into a good question that i hope someone will have an answer or reference for.

Working on structural steel to ASME III NF requirements, the client would like to perform MPI in all layers of a 3.5 inch thick groove weld. The MPI will be done while the piece is at preheat temperatures of 275f - 450f and this preheat is generated and maintained with Miller induction heaters.

Will the the induction heat field (heat is created electromagnetically) affect the characteritics of the magnetizing field of the AC yoke?

Any information will be helpful

Thanks

1
 
 Reply 
 
Manuel Haces
Director, - Wire rope inspection
Haces Inspección del Noreste and Wire Rope Inspection, Mexico, Joined Jun 2002, 124

Manuel Haces

Director, - Wire rope inspection
Haces Inspección del Noreste and Wire Rope Inspection,
Mexico,
Joined Jun 2002
124
23:35 Feb-27-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Derek at 22:50 Feb-27-2017 (Opening).

Quite probably yes. Check before with a gauge. Probably you can switch off the machine. Check for residual magnetism, do the test. And switch on the heating machine. But certainly, discuss with your client. The heating drop. Possible repairs, etc.

 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
12:43 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Derek at 22:50 Feb-27-2017 (Opening).

Dear Derek,

Some important questions:

1. What are you welding? Is it a pipe? or something else?

2. What are the welding positions? Is there any overhead welding?

3. What is the model of your Miller induction heaters? Is this the one with the rolling type induction? or the one with preheat cable cover, preheat insulation, with the cable harness or the one with induction blanket?

Several things that you might want to consider:

1. With regard to item number 3 above, most of the miller preheat systems which have insulations or blankets wont let you apply MPI because you don't have access to the part's surface. You might need to turn the system off, remove the hindrance, check the area of the inspection with gaussmeter or hall effect sensor and demagnetize it if necessary. Then it is ready for MPI. I think only the rolling type preheat ___might___ let you to do the MPI when heating is on. "might!"

2. You said you require preheating. Do you require to maintain heating between passes? Usually there is a minimum temperature requirement for preheating and a maximum interpass temperature. Please be more specific.

3. As you know, because of the low flash point of the liquid magnetic inks, to the best of my knowledge, you are not going to be able to find oil based and paraffin based magnetic ink for those temperatures you mentioned and your choice will be limited to dry magnetic powders. Dry magnetic powders have less sensitivity because they are not as mobile as the ink type. Also on a side note, dry powders will become ineffective above a certain temperatures because the color of the particles gets damaged. So it is another factor to consider.

4. If you have access to the part's surface during the preheat and interpass heating, and you are reluctant to turn the system off and demagnetize it before preforming the MPI, then I suggest that you apply the magnetic field with the yoke and put a foil type (Burmah Castrol Strip aka magnetic flux indicator) or a segment type (ASME Pie gauge or Berthold) flux indicators to see if the artificial flawa are showing up. This way you can find out if the magnetic field from the induction heaters are affecting the MPI test or not. Remember: We cannot have two active magnetic fields at the same time in the specimen. So if the yokes magnetic field is much stronger, then the resultant field is going to be in the direction of the yoke's field (the some of the two vectors...).

5. If you have any overhead welds, then you cannot apply the dry magnetic powders.

Sincerely,
EB

 
 Reply 
 
Matthew Aguiar
Canada, Joined Jan 2017, 11

Matthew Aguiar

Canada,
Joined Jan 2017
11
14:14 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Derek at 22:50 Feb-27-2017 (Opening).

Hello Derek,

Seems like Eager Beaver has provided you with a great comprehensive answer, one of the most valuable pieces of information there is the importance of a performance check and verifying adequate field strength with the Castrol strip, QQI, etc. and the demagnetization step.

The only thing I could really add to the previous responses here is that if the yoke does not provide you with an adequate result, you always have the option of using prods (if they are available to you). Although they may not be as desirable to use as a yoke, they do have their benefits!

1
 
 Reply 
 
Derek
Derek
14:19 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 12:43 Feb-28-2017 .

Thanks for your input is as i suspected

1. What are you welding? HY110 steel
Circular plates 90in dia with machined preps approx 3in thick to round beam flanges

2. What are the welding positions? Flat SAW

3. What is the model of your Miller induction heaters? - the one with induction blanket?

Several things that you might want to consider:

1. The plan is to expose a few feet at a time in the blankets - With regard to item number 3 above, most of the miller preheat systems which have insulations or blankets wont let you apply MPI because you don't have access to the part's surface. You might need to turn the system off, remove the hindrance, check the area of the inspection with gaussmeter or hall effect sensor and demagnetize it if necessary. Then it is ready for MPI. I think only the rolling type preheat ___might___ let you to do the MPI when heating is on. "might!"

2. Yes and yes - it must be preheated and kept heated for the duration of welding and 4 hours after i think as well - 250F min and 450F max interpass - You said you require preheating. Do you require to maintain heating between passes? Usually there is a minimum temperature requirement for preheating and a maximum interpass temperature. Please be more specific.

3. Only Dry powder for this - didnt know about the color change - As you know, because of the low flash point of the liquid magnetic inks, to the best of my knowledge, you are not going to be able to find oil based and paraffin based magnetic ink for those temperatures you mentioned and your choice will be limited to dry magnetic powders. Dry magnetic powders have less sensitivity because they are not as mobile as the ink type. Also on a side note, dry powders will become ineffective above a certain temperatures because the color of the particles gets damaged. So it is another factor to consider.

4. I will try the pie gauge - let you know how that goes -- If you have access to the part's surface during the preheat and interpass heating, and you are reluctant to turn the system off and demagnetize it before preforming the MPI, then I suggest that you apply the magnetic field with the yoke and put a foil type (Burmah Castrol Strip aka magnetic flux indicator) or a segment type (ASME Pie gauge or Berthold) flux indicators to see if the artificial flawa are showing up. This way you can find out if the magnetic field from the induction heaters are affecting the MPI test or not. Remember: We cannot have two active magnetic fields at the same time in the specimen. So if the yokes magnetic field is much stronger, then the resultant field is going to be in the direction of the yoke's field (the some of the two vectors...).

5. If you have any overhead welds, then you cannot apply the dry magnetic powders. Thanks

 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
15:19 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Matthew Aguiar at 14:14 Feb-28-2017 .

Dear Mattew,

Thank you for your input.

Just a caveat.

Using prod is a very good idea, but combine it with dry magnetic powder and the sensitivity is decreased for surface/surface breaking defects. The reason is that dry magnetic powders are less mobile for HWDC or FWDC. Even for wet magnetic inks, Prods have less sensitivity than AC Yoke, because they mainly use, HWDC, DC or FWDC.

ASME Sec V, 2015, Article 7, T-752.2, says: Direct or rectified magnetizing current shall be used.

So according to ASME Sec V, it is not possible to use AC Prod. As a result, demagnetizing the area of inspection is also going to be much harder for the prod technique. This can cause Arc blow and wander in the subsequent passes. Moreover, HWDC Prod + Dry magnetic powder is the best method for detecting subsurface cracks, not the surface cracks.

Because of the sensitive nature of their application (it is according to ASME Sec III), it should be remembered that the prods are notorious for producing cracks due to overheating at the point of contact, especially for low carbon steels. The prod's contact area must be kept clean and maintaining a very good contact is crucial. In case any arc or overheating occurs it is considered a flaw and must be assessed with another NDT method other than MPI. It is a good idea to add this to the procedure for the part to be further assessed for heat induced cracks in prod contact areas with PT method.

Moreover, ASME Sec V, 2015, Article 7, T-752.3 says, If the open circuit voltage of the magnetizing current source is greater than 25 V, lead, steel, or aluminum (rather than copper) tipped prods are recommended to avoid copper deposits on the part being examined.

This is mainly due to the fact that copper can be alloyed with the steel at contact point. Not using a copper tipped prod can cause surface oxidization with scale or rust on the steel. Definitely a Catch-22!

IMHO, Prods must be used as a last resort because of all the complications and problems it can produce.

Sincerely,
EB

 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
16:19 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 15:19 Feb-28-2017 .

HY110 + ASME sec iii ... hmmm. It sounds like a nuclear submarine!

The defects you are looking for are mostly due to cold/hot cracking in this type of steel and in service ductility and scc.

Regarding the color change at high temperature:

ASTM E709, 2015, 8.4:

Dry Particles—Dry magnetic powders are designed to
be used as supplied and are applied by spraying or dusting
directly onto the surface of the part being examined. They are
generally used on an expendable basis because of the requirement
to maintain particle size and control possible contamination.
Reuse is not a normal practice. Dry powders may also be
used under extreme environmental conditions. They are not
affected by cold; therefore examination can be carried out at
temperatures that would thicken or freeze wet baths. They are
also heat resistant; some powders may be usable at temperatures
up to 600°F (315°C). Some colored, organic coatings
applied to dry particles to improve contrast lose their color at
temperatures this high, making the contrast less effective.
Fluorescent dry particles cannot be used at this high a
temperature; the manufacturer should be contacted for the
temperature limitations (see 15.1.2).

I also suggest you to take a look at these paragraphs:

ASME Sec V, 2015:

T:731
T-776
I-730.2

ASTM E709, 2015:

8.4
8.4.1
8.4.2
8.4.3

10.1.1.1

15
15.1
15.1.1
15.1.2
15.1.3
15.1.4

19.2

20.3.8

20.5
20.5.1.1

20.6.8

Also you might find some useful information in AMS 3040 & 3044.

Sincerely,
EB

1
 
 Reply 
 
Matthew Aguiar
Canada, Joined Jan 2017, 11

Matthew Aguiar

Canada,
Joined Jan 2017
11
17:33 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 15:19 Feb-28-2017 .

Eager Beaver,

I would absolutely have to agree with you that prods are definitely a last resort, I could not see someone intentionally burdening themselves by dragging around a HWDC power pack and dealing with the endless hoard of arc burns over simply picking up a AC yoke! But every once in a while sometimes the least desirable option can become your only option.

2
 
 Reply 
 
Derek
Derek
19:15 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Matthew Aguiar at 17:33 Feb-28-2017 .

theres no prods here only yokes and dry powder

 
 Reply 
 
Dent
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
19:35 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Derek at 22:50 Feb-27-2017 (Opening).

In this particular case I would not recommend doing this MT. Firstly it must be dry MT. ASME NF does not require progressive examination. Advise your client that this examination may do more harm than good. You will certainly not be able to remove all of the dry MT powder especially with residual magnetism and the induction heating. the weld quality may be further compromised.
As I recall this material requires examination 24 hours after completion of welding and post heat. The value added by this examination is marginal and may even be negative.
I presume there will be a volumetric examination by NF on a weld this substantial. You might be wiser to perform hot volumetric examination on a half finished weld.
Others have commented on other aspects of this.
One other thing is that ASME Section V Article 7 does not allow the use of pie gauge or shims to prove the field adequacy when using the yoke technique. It is not an obvious statement in the code but the yoke technique is not included in the techniques where these devices may be used. This is done for very good reasons.

2
 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
20:13 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Dent at 19:35 Feb-28-2017 .

Thank you Dear Dent.

I remember that you once mentioned that you have tested an AC yoke on some non-ferromagnetic articles with a pie gauge showing enough field and you concluded that this shows that there was enough field between the yoke legs in the air. (if I am correct)

But to me it is not the same when you put the AC yoke on some piece of ferromagnetic material. Because when you put a yoke on a piece of ferromagnetic material, the field is going to choose the path with lower reluctance (higher permeability) so putting a Castrol Strip or a Pie Gague can prove the field strength.

I agree that there is not anything mentioned about using a pie gauge for proving the field strength and direction but does that mean using a pie gauge is forbidden? I would be thankful to have your input.

Also ASTM E709 mentions:

20.8.5 Magnetic Field Indicators:

20.8.5.1 “Pie” Field Indicator—The magnetic field indicator
shown in Fig. 14 relies on the slots between the pie shaped
segments to show the presence and the approximate direction
of the external magnetic field. Because “pie” field indicators
are constructed of highly permeable material with 100 %
through wall flaws, indications does not mean that a suitable
field strength is present for the location of relevant indications
in the part under examination. The “pie” field indicator is used
with the magnetic particles applied across the copper face of
the indicator (the slots are against the piece) simultaneously
with the magnetizing force. Typical “pie” field indicators show
a clear indication in a five gauss external field. These devices
are generally used as instructional aids.

Which is in accordance to what you said. Do you suggest Berthold or Castrol strips? ( I know they are not covered by ASME Sec V... but with common sense...? )

So I would be thankful to know what you suggest if Derek wants to proceed with what he has planned. Do you suggest a custom made test piece?

 
 Reply 
 
Dent
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
20:24 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 20:13 Feb-28-2017 .

Sect V Article 7 over rules EW 709 where there is conflict.
Article 7 clearly does not allow these devices when using the yoke. There is nothing stopping you from using them, but not for code compliance knowing that the results are meaningless.
The simple verification is 10 lb. lift test.

To state again my opinion is this test of this progressive weld will likely do more harm than good.

1
 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
20:24 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 20:13 Feb-28-2017 .

Dear Derek,

As Mr. Dent has mentioned the removal of dry particles is very hard specially with the inductive heating and residual magnetism.

It is a very important issue. Even in the case that there is not any inductive heating working, ASTM E709 suggest using compressed air to remove the dry magnetic powder. I mentioned this in several posts above in the paragraphs that I recommended you to read.

19.2 Means of Particle Removal—Typical post-examination
cleaning techniques employed are: (a) the use of compressed
air to blow off unwanted dry magnetic particles; (b) drying of
wet particles and subsequent removal by brushing or with
compressed air; (c) removal of wet particles by flushing with
solvent; and (d) other suitable post-examination cleaning
techniques may be used if they will not interfere with subsequent
requirements.

Please also read 23.1.2 if you want to use compressed air.

 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
20:29 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Dent at 20:24 Feb-28-2017 .

Thank you very much Mr. Dent.

I absolutely agree with you about the harm of the test.

Yes the 4.5 Kg lift test is for yoke functionality. Assuming that the yoke is fully functional, Derek wants to test if the field from induction heating system is interfering with yoke induction field or not.

In other words, yoke has the field F1 (a vector) and induction heating has the field F2 (also a vector). I think Derek wants to check if the F_total is still very close to F1 or not?

What would you do in the similar situation?

Thank you very much sharing your experience and knowledge.

Sincerely,
EB

 
 Reply 
 
Dent
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
20:36 Feb-28-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 20:29 Feb-28-2017 .

Turn off the heaters temporarily.

Would only do this test under duress!

1
 
 Reply 
 
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 161

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
161
01:34 Mar-01-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 20:13 Feb-28-2017 .

You can get a beautiful pie gage indication when it placed between the poles of an AC or HWR yoke on a concrete floor or wooden desk top. The pie gage responds to the magnetic field in the air a very short distance off of the test surface. There is no need to contact a ferromagnetic surface to get an indication. Because of the shape of the magnetic field between the yoke poles when it is on a ferromagnetic test surface, a pie gage can be useful in showing how far one should move the yoke (regardless of the directions used to establish 100% coverage) when testing a long weld seam. I am not aware of a really reliable artificial flaw that can be applied to this sort of surface. I prefer to use EDM or laser-produced notches when possible but of course these techniques can't duplicate actual product in every case. Regarding the 3.5 inch thick groove weld, a welding process that would not normally require testing each pass with magnetic particle would be better - such as submerged arc, then back gouging and doing MPI on that surface before finishing the weld from the other side.

 
 Reply 
 
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
09:22 Mar-01-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to John Brunk at 01:34 Mar-01-2017 .




Dear John,

Testing a yoke on a wood (a diamagnetic material) with an ASME pie gauge between its legs is not the same as testing it on a ferromagnetic material.

When you test a yoke on a wood or concrete surface with a pie gauge present, you are not seeing indirect evidence of the "field strength, b" in the wood or concrete. Instead you are seeing the "magnetizing force, H" between the legs of the yoke. The flux line choose the path of less reluctance which can be the air, then they enter the ASME pie gauge in between because it offers much less reluctance than air. So it is absolutely normal to see very strong and beautiful indications on the ASME pie gauge on a wooden or concrete surface.

On the other hand, when you put the yoke on a ferromagnetic material, (e.g. iron, soft iron) the flux line are established through the ferromagnetic part. Because it is the path of less reluctance.

See the picture that I have attached for how the magnetic field changes its path in the presence of the soft iron.

The field strength and path is not at all comparable to what is happening on a diamagnetic material like wood. Of course we do not want to compare oranges with apples.

Of course there is not any reliable method to permit exact measurement of field intensity inside the material. To correctly measure the field strength, lines of flux must be intercepted which is impossible without cutting the part itself. Even that causes the change of flux path inside the part again... the value that you read this way, is the field that is jumping the air gap.

The pie gauge on the part's surface at least shows if the direction of the magnetizing force is correct. Our friend Derek here wants to use the yoke when the inductive heating is on. So I believe the ASME pie gauge, Berthold and Castrol strips are going to show whether the direction of applied magnetizing force is correct or not.

Sincerely,
EB

 
 Reply 
 
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 161

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
161
19:55 Mar-01-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Hamid Reza at 09:22 Mar-01-2017 .

Dear Eager Beaver, Apparently you did not read my post completely or you would not have replied to it as you did. A very large number of words have been exchanged in this forum on this subject without a clear solution to the original problem.

 
 Reply 
 
Chris Edwards
Consultant,
United Kingdom, Joined Dec 2012, 43

Chris Edwards

Consultant,
United Kingdom,
Joined Dec 2012
43
03:38 Mar-02-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to John Brunk at 19:55 Mar-01-2017 .

Induction heating induces a large AC current sufficent to heat the steel, there is a coresspondingly large magnetic field. MPI would be problematic, the induced filed could be too high for MPI or it might be possible to carry out MPI without any other applied magnetisation. If the field is too high the induction heater would have to be turned off (gradually ramp down power to demag?) before performing normal MPI test.

 
 Reply 
 
Derek O'Connor
Derek O'Connor
15:07 Mar-02-2017
Re: Magnetic Particle Weld while Induction heater is running
In Reply to Derek at 22:50 Feb-27-2017 (Opening).

Thanks for all the great information eminent colleagues!

 
 Reply 
 

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