Is one better than the other? Advantages, disadvantages to either method? I used the chemical method quite a bit at work but have never used the magnaflux, we don't have the stuff to do that. The chemical check involves a cleaner, then spraying the area with one chemical and then after a certain period of time, spraying on the final stage at which time any cracks will show up. I'm starting prep on a new block and want to know if it'd be any better to pay someone to magnaflux it or just do the chemical method myself.

 

Mag is better as it's alot easier to see a bunch of metal dust particles jumping onto a crack.

 

I have done A LOT of both of these NDTs for over 20 years..........the main reason to use Magnuflux is the block does not need to be absolutly clean like it MUST be to get an accurate LPI and its a whole lot cheaper!

Primary Advantages of LPI:
The method has high sensitive to small surface discontinuities.
The method has few material limitations, i.e. metallic and nonmetallic, magnetic and nonmagnetic, conductive and nonconductive materials may be inspected.
Large areas and large volumes of parts/materials can be inspected rapidly and at low cost.
Parts with complex geometric shapes are routinely inspected.
Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.
Aerosol spray cans make penetrant materials very portable.
Penetrant materials and associated equipment are relatively inexpensive.

Primary Disadvantages of LPI:
Only surface breaking defects can be detected.
Only materials with a relative nonporous surface can be inspected.
Precleaning is critical as contaminants can mask defects
Metal smearing from machining, grinding and grit or vapor blasting must be removed prior to LPI
The inspector must have direct access to the surface being inspected.
Surface finish and roughness can affect inspection sensitivity.
Multiple process operations must be performed and controlled.
Post cleaning of acceptable parts or materials is required.
Chemical handling and proper disposal is required

Magnetic Particle Inspection
Magnetic particle inspection is a nondestructive inspection methods used for defect detection. The method is used to inspect a variety of product forms such as castings, forgings, and weldments. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such iron, nickel or cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be effective. Many different industries use magnetic particle inspection for determining a component's fitness-for-use.

Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petro-chemical , power generation and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test such things as offshore structures and underwater pipelines.

The magnetic particle inspection method along with liquid penetrant inspection is one of the oldest and most widely utilized forms of nondestructive testing currently in use today. Magnetic particle testing uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components. In theory, it is a relatively simple concept. When a bar magnetis broken in the center of its length, two complete bar magnets with magnetic poles on each end of each magnet will result. If the magnet were cracked but not broken completely in two, a north and south pole will form at each edge of the crack, just as though the break had been completed. If iron particles were then sprinkled on this cracked magnet, these particles will be attracted not only to the ends of the magnets poles but also to the edges of the crack.

In magnetic particle inspection there are primarily two types of magnetic fields used to inspect parts, longitudinal and circular. Longitudinal magnetic fields are typically created by placing the part in a strong external magnetic field generated by a conducting copper wire that has been looped or wrapped to form a coil. A coil would be used to inspect such things as a steel rod or a valve from a car engine that might have cracks or inclusions in it. A magnetizing coils is a standard feature on a dry/wet inspection unit but smaller field portable coils are also available. A wet horizontal unit is a large stationary piece of equipment that not only has head-shot and central conductor fixtures but also has a coil permanently mounted to it. The magnetic particles are held in a suspension of either water or oil and are supplied by a pump and hose on the system. These particles are of either the visible type, which means that they can be seen in normal white light, or the fluorescent type. Fluorescent particles require the use of a blacklight, which causes the particle indications to illuminate. This is much the same as causing a blacklight poster to glow in the dark.

I have used 110V to 440V

 

Wow.....i think that about puts this topic to bed.

 

Allthrottle's write up was pretty good. But it always sticks in my craw when I here the term "magnaflux". This is a brand name of the company that manufactures the consumables for the NDT industry. What is typically refered to as "magnaglux" is magnetic particle inspection or MT for short. The "chemical" process mentioned above is liquid penetrant inspection or PT for short. I do however disagree that it's less important for the block or whatever to be clean with MT as opposed to PT. And while MT may be cheaper if you already have the equipment, PT is by far cheaper for someone who does not. Three aerosol cans compared to powder or bath as well as a yoke is not comparable. Look around at an industrial testing supply house and they can give you a crash course and the materials you need. If you be real cool about it, the guy working in the back who works on all the stuff will usually "inspect" your stuff cheaper than a machine shop. If your really interested in knowing the differences and there limitations PM or email me.

ltlevil
American Petroleum Institute Authorized Pressure Vessel Inspector- API 510
American Petroleum Institute Authorized Piping Inspector- API 570
American Welding Society Certified Welding Inspector-CWI
ASNT Level II -MT, PT, UT and Film Interpretation

 

I tried to keep it simple…………I do agree on Magnaflux, but that’s what most engine shops/users call it and it’s been around since 1934 .
As a good example of were Magnaglo/Magnaflux is used today:

Amusement Rides

Automotive Manufacturers

Automotive Rebuilders

Fabrication Shops

Foundries

Law Enforcement

Lifting Devices

Maintenance Shops

Marine

Military

Pipelines

Railroads

Shipyards

Ski Lifts

Steel Mills

Test Labs

Tool Shops

Gas/Nuclear Utilities

Welding Shops

I am also a II and perform inspections with borescopes, videoscopes and fiberscopes. Lots of fun!
The cost is all relative but correct interpretation of PT results takes more training than MT to be sure…..

 

I understand, you did a great job of explaining things. I guess I'm a little sensitive. Several weeks ago I was contacted to "magnaflux" an aluminum head. I explained this could be done (head checked for cracks), but not in the "traditional" sense of "magnaflux". Went on to tell the gentleman the head would need to be disassembled, cleaned etc... Holy moses you would have thought I looked under his mother's skirt to do some inspection work there! All of a sudden I went from knowing my sh$t, to not knowing my a$$ from a hole in the ground. Something to the effect if I didn't know what "magnaflux" was I didn't need to be working on his stuff . I then reminded the gentleman that he called me, to which he replied that was my fault as well because I had misled him! I had never talked to him before, didn't even have a clue who he was. Bad thing is I don't even charge for that kind of thing it's always "do a favor for someone else" that's my rate. I was just trying to make sure everyone realizes there is a terminology difference. You also mentioned borescope, that is the shiznit. I have found it especially helpful when buying a used motor that's still assembled, sure does make looking at the cylinder walls alot easier. Only problem is sneaking the rig out so you can use it! Good talking with you and take care, also if you're ever in my neck of the woods drop by. Open invitation to tell lies, drink beer and eat boiled seafood. On top of this No Problem Raceway is about 45min. away and they have a SuperChevy show there in March or April. Like I said consider it an open invitation.

Steve

 

Good deal Steve, its a small world
No doubt some good stories to tell
I work on 95,000 tons of diplomacy...........lots of NDT/Lead Auditor work.
I am 3 miles from AB's Williamsburg, VA. brewery...........nothing like same day beer

Steve

 

A couple of C-notes can solve that problem.

The ProVision by SLI brings borescopes down to where they're
become reasonably affordable for just about anyone.

.

 

I've had them considering one of these at work for a while now. That'll help. Thanks.

 

In order for us to "release" any block for a build it MUST be pressure-tested. You CANNOT build a big enough magnetic field through a casting that size and on top of that you can't see every nook-&-cranny. They simply must pass a pressure test. We mag with both
"powder" and the "black-light/fluid" method, and nothing beats the old-fashioned P.T. "Spot-checking" suspected problems is OK. Thanks Gary in N.Y.