What is the typical demagnetizing process used after MPT inspection?

Using an AC demagnetizer is the typical demagnetizing process employed after Magnetic Particle Testing (MPT) inspections. This method is effective because it applies an alternating current field that progressively reduces the magnetic field in the test specimen to eliminate any residual magnetism that could interfere with subsequent inspections or affect the performance of the component in its intended application.

AC demagnetizers work by creating a rapidly alternating magnetic field, which helps to randomize the magnetic domains within the material. As the component is moved out of the magnetizing field while the AC current is applied, the magnetic domains become disoriented, leading to a decrease in the overall magnetic field of the component until it is effectively demagnetized.

Other methods, like applying a permanent magnet, heating the component, or using mechanical vibration tools, are not standard practices for demagnetization following MPT. Permanent magnets would typically reinforce rather than eliminate magnetism, heating may not uniformly cover the component or sufficiently reduce magnetism for all materials, and mechanical vibration is not a recognized technique for demagnetizing in the context of NDT. Thus, the choice of an AC demagnetizer aligns with industry best practices for ensuring that components are in a neutral magnetic state post-inspection.