Accessories

Equipment

Materials

SELECTION GUIDE: MAGNETIC PARTICLE INSPECTION EQUIPMENT

In addition to standard purchasing decisions regarding versatility, economical operation, durability in harsh environments, and reliability, the purchase of the particular type of MPI equipment depends on four primary criteria. These criteria are detailed below.

1. Types of Defects

a. What type of defect are you attempting to identify?

• Surface Defects – an AC model is generally sufficient
• Near Surface Flaws – an HWDC (half wave DC) or FWDC (full wave DC) model is recommended

b. What is the direction of the defect you are attempting to identify?

• Longitudinal Defects – A contact shot is used to inspect longitudinal defects
• Transverse/radial Defects – A coil shot is used to inspect transverse/radial defects

2. Part Length

a. Conventional MPI Units

b. Multi-Directional MPI Units

3. Processing Rate

Is your production rate low or high?

• Low – A Conventional MPI unit that requires one contact shot and one coil shot is sufficient.
• High – A Multi-directional unit is recommended because it magnetizes parts in all directions in one cycle/shot, thus reducing processing time dramatically

4. Magnetizing Field Strength

Proper magnetizing field strength depends on the material, size, and geometry of the part plus the type and location of the defects being sought.

The most effective method of determining adequate field strength is testing with artificial QQI defects adhered to critical inspection areas.

Rule of Thumb – The general rule for contact shots is 100-500 amps/inch of part diameter.