Conveyor belts for a metal detector – what do you need to pay attention to?
Industrial metal detectors and x-ray inspection systems are often used in pharmaceutical and food industries. They check whether the product contains any materials that are not naturally present in food.
People regularly ask me which conveyor belt is suitable for this type of application. This question often comes after an incorrect belt has already been installed and is causing the detector to malfunction.
How does a metal detector work?
Before selecting the appropriate belt, it is important to understand the basic mechanics of how a metal detector works. Most simply, it is an electric coil which creates a magnetic field. The conveyor belt carries an object through this field and when an abnormality occurs, the magnetic field changes and the detector is signaled.
There are a number of factors to consider when selecting a belt for a metal detector or x-ray inspection system:
- Fabric conveyor belts with a fully conducting antistatic layer generate a signal at the joint. Because of this interruption in material, it makes them unsuitable for this type of application
- Fabric conveyor belts with longitudinal conducting carbon fibers (instead of a fully conducting layer) provide antistatic properties without disturbing the metal detector. This is because of the thin fabric
- Fully synthetic, monolithic and plastic modular belts (without any special properties) can be used as well. However, these belts are not antistatic
Below are some further tips for optimum operation:
- Avoid varying thicknesses (e.g. joining film or cleats), asymmetry and vibrations
- Of course, metal fasteners are not suitable either
- Conveyor belts designed for metal detectors must be stored in their packaging in order to prevent contamination
- While constructing endless joining, be particularly careful that no dirt (e.g. metal parts) end up in the joint
- The belt supporting in and around the metal detector must be of a non-conducting material
- The conveyor belts must be properly aligned and may not rub against the frame
- When carrying out on-site steel welding activities, protect the conveyor belt against welding sparks
Online help in selecting the proper conveyor belt
On our website there is a tool that can help you select a conveyor belt based on a number of criteria. If you would like additional personal advice, please send me an e-mail at email@example.com.
I have found that 2 additional factors influence the installation
The sensitivity setting on the metal detector. If it is too sensitive the metal detector picks up surrounding metal objects even people passing with keys etc. Also moisture seems to affect the magnetic fields
Dear John, thank you for sharing this additional information.