Quality audits call for magnet inspections

Magnet inspection in Mauritius | Goudsmit Magnetics

They travel separately around the globe conducting hundreds of magnetic inspections each year. So far the farthest destination is Mauritius, which they take turns visiting once a year to perform magnet inspections at local sugar factories that must comply with European standards. Most of these inspections are for the food industry, but the chemical and mineral industries also require reliable reports that document the condition of magnets in the processing line. These are requirements that are imposed when companies want to pass quality audits. After all, the condition of a magnet is important for the quality of the finished product.

Quality inspectors
We asked our quality inspectors, Ger Kuijken and Roy van der Heijden, to tell us what a magnet inspection involves. Ger explained, ‘Usually the customer contacts us with a request, and otherwise we reach out to them if it has been almost a year since the previous inspection. The quality manager meets us on arrival and shows us where the magnet or magnets are installed in the processing line. Most of the time production must be stopped for about fifteen minutes so we can remove the magnet from the process to conduct the best possible measurement. Naturally we strictly adhere to the hygiene and safety standards in force within the company. Sometimes we have to wear so much protective gear you wouldn't even recognize us!’


Flux density
Roy continued, ‘We measure the flux density with a calibrated flux density meter, and we also check whether the magnet is properly installed in the production line and how well it has been maintained. We measure all the magnetic components present in the system, looking for the highest value. Then we look at whether all the plates or magnetic rods are within 10% of the highest measured value. This is the value that appears on the certificate. This allows us to see whether the magnetic value of the system measured during the annual inspection has stayed the same. Customers can choose which values they want to place the emphasis on; this can be from lowest to highest value, just the highest or just the lowest magnet value, or the replacement value of the magnet. It may also be that they only want a recommended or rejection value shown on the certificate. We provide whichever type of certificate they want.’

Ger added, ‘Customers decide their quality level for themselves. They may want a minimum of 10,000 gauss deferrization, or 5,000 gauss may be sufficient for their purposes. The latter, for instance, is sufficient for the capture of larger pieces of steel (> 2 mm). What is also important is whether the system is at a Critical Control Point (HACCP, a mandatory standard for the food industry with which the company complies) or the magnet serves to protect a machine. The market often demands the highest flux density. This is found by direct measurement at the pole. It is important that the measurement is always performed in the same way so it can be compared with the previous measurements. When the difference from the original value exceeds 10%, we explain what improvement measures are possible. In the near future our engineers will even be able to provide figures that predict the effectiveness of a magnet when the flux density drops.

Magnetic value
Roy continued, ‘The magnetic value can drop due to external conditions, such as moisture, exposure to high temperature or hard impacts or shocks. A regularly conducted, expert inspection provides clear insight into the quality and effectiveness of a magnet. Moreover, the inspection report offers guarantees for the positive assessment of quality audits that our customers receive from their suppliers.’

Magnetic field
Roy made one more important remark: ‘As everyone knows, you can measure the flux density of a magnet, but the magnetic holding field in the product chute is also very important! After all, a product chute must be completely covered by a magnetic field; rods mounted too far apart just won't get the job done. You can measure 10,000 gauss on the rods, but if the space between the rods is too great there will be spots where there is no magnetic field present and iron particles can slip through. Occasionally we encounter a situation in which a customer has increased the space between the rods or grids in an attempt to increase the product flow. But Goudsmit has other solutions for achieving that, such as rotating magnets, while still maintaining the desired level of effectiveness.’


An inspection certificate contains the following data:

  • Certificate number & date
  • Customer details
  • Contact's name
  • Goudsmit inspector's name
  • Magnet details, such as customer code, quantity, dimensions and holding field depth measurement
  • Measurement data, such as gaussmeter used, product temperature, measured value and normal value (+/- 10%)

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