In this video Magnaflux’s Brian Batteiger goes through the common steps of magnetic particle inspection on ferrous parts as outlined in ASTM E1444: Standard Practice for Magnetic Particle Testing. The specific sequence of steps may vary depending on the method of particle application, here we outline the steps in wet magnetic particle application, continuous method.
- Surface preparation: It is important for the test surface to be clean, dry and free from any dirt, grease, scale, paint or other materials which might interfere with the inspection, Brian is using SKC-S solvent cleaner/remover.
- System performance verification: Before beginning a mag particle inspection UV light must be verified with a UV-A Light Meter, white light measurements taken with a Visible Light Meter and magnetic particle bath concentration must be checked with a Centrifuge Tube.
- Magnetization set-up: The test part or area must be set-up to have the magnetizing current applied to it. This will be different for various applications, in the video Brian demonstrated how to set a part in a magnetic wet bench between the headstock and tailstock.
- Magnetization method: There are different types of magnetic current, ways to apply current to a part and magnetic field direction, check the part procedure for the correct magnetization method.
- Amperage: Make sure to consult the part procedure for the correct amperage which will vary depending on the part, type of metal and type of defect needing to be found.
- Magnetic field strength: Check the magnetic field strength with a Hall Effect Meter, QQI, known defect or Magnetic Flux Indicator Strip.
- Bathe the part: Brian demonstrates wet magnetic particle application, continuous method by apply the mag particle bath to the part before applying the current. In the Magnaflux demo room we use 14A magnetic powder in Carrier II for excellent indication visibility with less maintenance and better equipment life-span.
- Apply magnetic current: For wet, continuous method the magnetic bath stream is stopped directly before or at the same time the mag current is applied to the part. This is to minimize the possibility of the stream washing away any fine indications.
- Inspection: Evaluate the part under appropriate UV lighting conditions, Brian uses our EV6000 hand-held LED UV lamp in this demonstration. Inspect the part for any indications and take the appropriate steps to interpret and document any findings.
- Additional magnetization: Depending on the part and the process, additional magnetization may be required. In this case, repeat steps 3-6 for the additional magnetization.
- Demagnetization: Using the appropriate magnetic current, field strength and direction, demagnetize the part after the final inspection is complete and use a Field Meter to check for any residual magnetism.
- Postcleaning: Parts are cleaned after inspection to remove any remaining magnetic particles.
Just like all nondestructive testing methods, the results of a mag particle inspection are only reliable if the testing is performed accurately and consistently.
This is meant to provide a general overview of a typical MT / MPI process; all NDT testing must be performed in accordance with the prescribed specifications or test procedures.