Magnetic Particle Inspection for crack detection

Bluewater Thermal Solutions employs a non-destructive testing procedure called magnetic particle inspection on ferromagnetic materials in order to detect defects and surface or subsurface anomalies by magnetizing the metal part and then applying a wet or dry suspension of ferrous iron particles to the component so that, much like a magnet, the iron particles will be attracted to any problem areas. There are two types of magnetic particle inspection methods Bluewater technicians will utilize depending on the material being tested. This magnetic particle inspection method is our most widely used technique because it has a greater level of sensitivity at detecting any discontinuities within the material.

For steel components which have been previously treated for stressed applications, our technicians will typically utilize the residual magnetic particle inspection procedure. In selecting the appropriate magnetic field and current we consider the part geometry and material, the types of problems we are looking for, and how deep the field needs to penetrate the material. In each method it is necessary for the anomalies that are revealed to be properly examined so that it can be determined if the indications are debilitating to the component itself or if they are merely irrelevant. Features of the anomalies that distinguish the type of indications present include the shape of the particle buildup and the breadth and clarity of the outline. The types of discontinuities or indications include cracks on the surface or subsurface, fatigue cracks, shrink cracks, grinding cracks, seams, hairlines, inclusions, forging laps, seams,  splits, tears, pipes, voids, porosity and bandings.

Magnetic Particle Inspection features

  • Does no damage to the metal
  • Rapid detection of defects located on or near the surface
  • Approximate size and shape of defects are outlined
  • Helps prevent the failure of parts during service
  • After the part has been magnetized and tested, demagnetization is possible
  • Excellent for detecting anomalies too small to be seen with the eye

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