Magnetic Particle Testing MPI

Flawed can offer Magnetic Testing on-site or in house for smaller components in our dedicated test facility. We offer both visual colour contrasting methods and fluorescent.

Our Lillyhall, Cumbria facility can offer full MPI bench unit for one off or batch items.

Our technicians have PCN Level 2 Technicians to test welds, forgings and castings.

We can also offer PCN Level 3 Magnetic Testing services.

Learn About Magnetic Testing – What is it?

Magnetic Particle Inspection (MPI), also referred to as Magnetic Testing or Magnafluxing, is a non-destructive testing (NDT) methodology used to detect surface defects (plus defects located just below the surface) of ferromagnetic objects.

Ferromagnetic objects are made of iron, nickel, cobalt, or their alloys and can be magnetized by applying an electrical current (either AC or DC current can be used). Many industries including construction, automotive, military, aerospace, power generation and petrochemical use this non-destructive evaluation technique on forgings, castings and welds, including underwater (e.g., on oil rig components), to hunt for stress fractures and other defects. Some common items that are typically inspected using magnetic testing include boilers, pipes, crank shafts, cam shafts, washers, threaded bars, engine gears, connecting rods, piping joints, aircraft landing gear and many others.

Magnetic particle inspection is a popular NDT method because it is fairly easy to do, does not require as much cleaning or preparation to execute, is safe for both the inspector and the item being examined and relatively inexpensive as compared to other NDT techniques.

First an electrical current is applied to the object being tested to magnetize it. If the ferromagnetic item is flawless, the lines of magnetic flux (field) will transfer across the object unimpeded in straight lines. When there is a crack, flaw or discontinuity in the surface of the item being tested (for example, an excessive metal buildup concentrated in one small spot), however, magnetic flux and magnetic particles will leak out of the item at the site of each defect. When iron powder is applied to the object, it will collect in the spots where the flux is leaking. The powder will also reveal the size and the shape of each flaw in the object.

Magnetic testing can be conducted inside a testing facility using a stationary test bed or out in the field using a portable yoke device, making it a versatile nondestructive evaluation technique. The basic steps are as follows: clean the item, apply the electrical current, apply the iron powder or ferromagnetic medium while the part is still magnetized, remove any excess medium (for example, by using a bulb or syringe to gently apply a stream of air to the object), document the flaws or defects, turn the machine or yoke 90 degrees to repeat the steps, then demagnetize and clean the part.

Although magnetic particle inspection is useful for inspecting a variety of welded, cast or forged items, there are some drawbacks to this NDT technique. Most notably, it cannot be used on materials like aluminum, austenitic stainless steel or magnesium, and only small sections of each object can be examined at one time. Some items require a lot of power to magnetize, making this technique inefficient for some large scale ferromagnetic parts and equipment. Magnetic testing is best for the detection of surface level defects only and cannot detect deeper flaws although using DC current and a discerning eye slightly sub surface defects can be found.

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