RIDGID metal detector User's Guide download pdf (Page 23)

About Metal Detection

Shapes and Orientation of Metal

Metal detector standards are based on testing using sphere shaped pieces of different types of metal

and in different sizes. This is because spheres are the same shape and size when viewed from any

angle.

Real contaminants are rarely spherical so may produce different signals depending on their

orientation as they pass through the aperture. Wire contaminants are the most dramatic example of

this as shown in the diagrams below.

A common solution to this problem is to use two metal detector heads positioned at different angles

across the conveyor belt so that the contaminant is presented at a different angle to both detectors.

Testing Metal Detector Performance

Regardless of how sophisticated and reliable a metal detector is, it is only as good as the frequency

and thoroughness of the testing programs supporting it.

Testing and recording are essential components of any HACCP system and must be supported by

clearly documented testing procedures that are communicated to all staff using the detector and are

monitored and reviewed on a routine and regular basis to ensure compliance with customer and

legislative requirements.

Test Frequency

Intervals between tests need to be short enough that if a fault is found, products potentially affected

have not left your premises and can be identified, recalled and retested. Once again, if your company

is a private label manufacturer, ensure that you agree upon any variation you make to testing

procedures, in writing, with your retailer customers.

To facilitate effective testing, all of Loma's Metal Detectors have an integral

Performance Validation

System (PVS) feature. This feature can be set up to automatically prompt the operator to carry out the

required test at a pre-set interval.

Product Test Samples

Some guidelines for the provision of product test samples are listed below.

■

Ensure that the samples are representative of a good product in all respects.

■

Ensure that the samples are free from metal contaminants.

■

Mark or label the samples to identify them and prevent them being despatched to customers.

■ Produce fresh samples for testing at a frequency that reflects the nature, durability and shelf

life of the product concerned. ‘Stale’ test packs may produce different product signals.

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RIDGID metal detector User's Guide Page 23