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#8689 - 11/05/06 03:24 PM Re: Damascus barrels and magnafluxing question [Re: Zircon]
HomelessjOe Offline

Registered: 01/15/06
Posts: 14388
Loc: The Great State of Tennessee
Interesting post. I guess shooting damascus barreled guns is as close as I'll ever get to sky diving or bungee jumping.
NEVER ANOTHER DIME TO DAVE as long as he locks threads and removes posts.

#8690 - 11/05/06 03:25 PM Re: Damascus barrels and magnafluxing question [Re: Zircon]
Dick_dup1 Offline

Registered: 01/09/03
Posts: 798
Loc: WI
Originally Posted By: Zircon
Dick, in addition to standard codes (how large of an indication is rejectable), there is the issue of standards to set up the inspection process - especially with UT. The instrumentation needs to be calibrated with a standard that has similar metallurgical characteristics to the barrel being tested. For all practical purposes this means the standard needs to be a damascus, twist, or what have you barrel, equivalent in metallurgical condition (chemistry, thermomechanical processing, and final heat treatment) to the barrel being tested. The standard has reference notches, flat bottomed holes or what have you that the instrumentation must "see" and detect at a specified level. Then, and only then, is the test valid. I believe there are way too many variables to conduct NDE and then make a conclusion as to the safety of any given set of barrels.

As far as proofing goes, it's been around a long while, but it isn't the be-all, end-all either. There are some barrels in the "barrel study" that show definite signs of fatigue failure - something that no single overpressure shooting event will be able to detect.

You are indeed correct.
As I said, I set up, staffed and managed an NDE Department as part of a Quality Control Department. I had Level I, II and III Inspectors for every NDE discipline working for me. I have participated in the NDE of everything from welds on 35" SS piping, Inservice Inspections by underwater UT, radiography and eddy current testing of Steam Generator tubing. I have not listed all the standards because I wanted to keep things simple.-Dick

#8719 - 11/05/06 07:13 PM Re: Damascus barrels and magnafluxing question [Re: Dick_dup1]
Zircon Offline

Registered: 10/01/05
Posts: 142
Loc: Orygun
I'm in a similar circumstance, Dick. Have a QA and Inspection group that includes Level II inspectors and Level III examiners for UT, PT, RT, and ET. Not questioning your veracity, just wanting to add some commentary so that those outside the profession understand some of the limitations.

#8872 - 11/06/06 03:34 PM Re: Damascus barrels and magnafluxing question [Re: Zircon]
Jim Haynes Offline

Registered: 01/09/02
Posts: 358
Loc: Richmond, Texas
A very interesting series of posts. As an ASNT certified Level II inspector in Mag Particle Testing (MT) among others, I agree with everything Dick_dup1 stated. Someone suggested a wet flourescent test, but I can ascertain that would be a near impossibility to come to any conclusions. I asked my Level III what procedure would he write and what code would he use to perform such test on damascus barrels. He came back with the answer that first he would have to find from a customer or appropriate source what would be the acceptable and reject criteria. This is because a damascus barrel by nature of construction will display continuous bands of discontinuities. He knew of no source of reject criteria for relevant indications. In fact, it would be very difficult to determine between relevant and non-relevant indications, depending upon the type/quality of damascus or twist construction.

For fun, I took the damascus barrels of one of my wall hangar guild guns (a JABC) and did a head shot followed by a coil shot. Under the black light I had a beautiful yellow/green graphic of the welds. A discontinuity that was relevant would have been very hard to find, much less interpret.

As an afterword, cleaning the barrels after the test required intensive work. Nonetheless, I found lines of rust beginning where the microfine particles had imbedded themselves. I would not want to put damascus barrels from a high quality gun in such a test. Jim Haynes

Edited by Jim Haynes (11/06/06 03:34 PM)
Jim Haynes

#8942 - 11/06/06 10:34 PM Re: Damascus barrels and magnafluxing question [Re: Jim Haynes]
I. Flues Offline

Registered: 04/12/03
Posts: 327
Loc: Parma, OH
Awwww....come on guys! Jist get those Damascus barrels Magnaported and be done with it!

Sorry, I couldn't resist.....;-)

Mike Doerner

#9729 - 11/11/06 01:55 PM Re: Damascus barrels and magnafluxing question [Re: 2-piper]
Dave Weber Offline


Registered: 11/09/01
Posts: 780
Loc: Bloomfield, NY

What is Magnetic Particle Inspection?
Magnetic Particle Inspection or MPI is a nondestructive testing (NDT) method that is used to detect surface or near to surface discontinuities (such as cracks) in iron or steel. This NDT method is also often referred to as "Magnafluxing."

How does it work?
As its name implies, Magnetic Particle Inspection works using magnetism. Thus it will only work on a ferromagnetic material such as iron or steel.
The part or surface to be tested is placed in a magnetic field. The field is made up of flux lines that by nature move from the north pole of a magnet to the south pole. For this to happen the flux lines can either move through the air, or they can move through the metal. It is "easier" for the flux lines to move through the metal. Thus, most of them do just that; they travel in a path that is parallel to the surface being tested.
If, there were a crack in the test surface, the path of the flux lines through the metal would be interrupted. The flux lines, in order to cross this "ditch" would be forced to "jump over" it by temporarily leaving the metal, and travel through the air, before returning to the metal. This causes what is called a flux leakage at the crack. The flux leakage causes the crack to become a mini magnet. At this point, if one were to sprinkle some iron filings over the area with the crack, the filings would immediately be attracted to the crack. They would form up along it in such a way that the filings would form the complete outline of the crack. This would be easily visible to the naked eye, especially if the iron filings were themselves red in color, and the test surface were painted white.

What are some of the advantages and disadvantages of MPI?
MPI has the following advantages:
1) It's considered to be the best method for the detection of fine, shallow surface cracks in iron and steel. Thus, it's ideally suited to look for fatigue cracks, heat cracks, and other discontinuities, in weldments, on shafts, etc.
2) It will work through thin coatings of paint. This is not true for some of the other NDT methods. Thus new paint jobs on equipment need not be marred for this method to work.
3) It is highly portable. This method can be used anywhere, such as out in the field on construction sites, and even under water.
4) It's not limited by the size and shape of the specimen being tested. Small tanks to large cranes can be inspected using this method.
5) Inexpensive. The powders and liquids used for this test method are readily available.

MPI has the following disadvantages:
1) It will only work on ferromagnetic materials such as iron or steel. For other materials such as aluminum or plastic, alternative methods such as liquid penetrant would have to be used.
2) Although it can detect problems that are close to the surface of the material, ones that are very deep in the material will not be found when using this method.

How does Domson make use of MPI?
Of all the various NDT methods, Magnetic particle inspection is the method that Domson employs the most. It is always used extensively throughout our equipment certification programmes.
MPI is used on all the critical welds on lift equipment, and other structural members. It is also used on the main bodies/sections of lifting equipment and structural steel. Examples of this include the saddle areas of lifting hooks, and the high stress corner areas of structural steels.

MPI is best suited for finding surface cracks. Why would you use it on structural steel; wouldn't you miss the internal cracks?
Lift equipment and structural steels can be subjected to continuous and/or dynamic loads (i.e. shock loads). These can cause fatigue cracks to form in the cross sections of the steel. However, whether the steel is subjected to bending or shear, or shear due to angular twisting, or any combinations of these, it is the surface of the part that is typically subjected to the highest stresses. This means that if a fatigue crack were to form on the cross section of a part, it will always form on the outer surface of the part, rather than starting somewhere in the middle or interior of the cross section. Therefore, MPI is ideally suited for finding fatigue cracks.
Dave Weber
DoubleGun Evangelist
In Charge But Not Responsible

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