How to Conduct a Magnet Pull Test

Attention to product purity on the production line has never been greater, creating the need for manufacturers to detect and eliminate foreign objects before the end product reaches end-use customers. Eliminating contaminant metal also prevents damage to expensive processing machinery, reducing downtime and repair costs. Eriez (Erie, PA) shows manufacturers how and why it’s important to conduct a magnet pull test.

http://youtu.be/5slbfB0-7zQ

For the most part, smaller permanent magnets should be subjected to semi-annual testing using a pull test kit. These permanent magnets include magnetic plates, magnetic grates, magnetic traps and grates in housing.

FACTORS AFFECTING MAGNETIC PERFORMANCE
Under normal operating conditions, magnets should retain their strength indefinitely. However, several factors affect performance and should be recognized by plant operators before testing for magnet pull strength.

Exposing magnets to high temperatures outside their design range may cause magnets to fail completely or show signs of weakening. (Typical ranges for standard Eriez Rare Earth (RE) magnet circuits are up to 150 degrees Fahrenheit, 150 to 250, 250 to 400 and maximum 850 degrees Fahrenheit.)

Welding equipment used on, or in close proximity to, permanent magnet circuits can be damaging to magnet performance. The direct current can short the magnetic field and essentially kill the magnet. Also, the heat associated with welding will damage the magnet circuit.

Subjecting the raw magnet material to liquids as a result from a breach in the magnet enclosure. RE magnets are typically made from Neodymium Boron Iron and the iron will oxidize, causing the circuit to fail if it gets wet.

Physical abuse when handling the magnet will create a shortened lifespan. The actual magnet material inside the separator is brittle. When subjected to repeated abuse or heavy physical handling, it will break down over time and fail. This may occur even when little physical damage is evident on the outside.

WHICH MAGNETS GET TESTED?
For the most part, smaller permanent magnets should be subjected to semi-annual testing using a pull test kit. (Pull test kits are available from most industrial magnet manufacturers.) These permanent magnets include magnetic plates, magnetic grates, magnetic traps and grates in housing.