Gravity Fall Metal Detector Systems | SAFELINE

    Gravity Fall Metal Detector Systems

    For inspection of free falling powders, grains or granules

    Products and Specs

    Inspection of Powders and Granules

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    How does a Gravity Fall metal detector system work?

    Gravity Fall metal detector systems are suitable for the inspection of any free-flowing powder or granular product such as flour, milk powder, dried fruits and peanuts. The product flows through the production line and free falls under gravity through a small metal detector aperture, achieving high sensitivity. High frequency operation and sophisticated electronic filtering techniques combine to deliver the ultimate in metal detection sensitivity within the product flow. On detection of metal, a fully automatic, high-speed reject device operates, diverting the contaminated product and isolating it from the main product flow.

    How do I choose the most suitable Gravity Fall metal detector system?

    Gravity fall metal detection systems have been designed specifically for the inspection of free falling powders and granular products in non-pressurised applications. Reject devices are designed to be dismantled quickly and easily without the need for tools. This shortens clean down procedures to maximise production capacity. All reject devices are failsafe on power outage. Anti-static throughput tubes are supplied as standard to reduce the potential for static build up.

    Y-Valve Gravity Fall systems are suitable for the inspection of powders and granular products. The Y-Valve's quick release and captive reject mechanism simplifies cleaning procedures, ideal when product changeovers are frequent and when regular cleaning between production batches is required.

    Sealtite Gravity Fall systems feature an innovative design to provide a dust-tight seal. This virtually eliminates the escape of good product into the reject channel, reducing product waste. Sealtite technology is ideal for inspection of high value, dusty products in explosive environments and applications where insertion space is limited.

    Open Diverter Gravity Fall systems provide a cost effective solution for non-dusty products, and can be upgraded to Sealtite standards retrospectively if required. This system is best for non-dusty granular products where insertion space is limited.

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    What design features are in place to comply with industry and retailer standards and regulations?

    The following system design features are generally considered good practice, and will satisfy most brand retailer and food industry requirements:

    • A reject mechanism which can isolate the actual product which may contain metal contamination
    • An audible and visual indication of system status e.g. product has been rejected.
    • A reject confirmation system that will stop the flow of product if there is a failure of the reject mechanism.
    • Fail safe design in instances such as a power outage.

    How can a Gravity Fall metal detector system boost productivity?

    The period between metal detector tests can vary from each manufacturer and is dependent on the application, processes employed and distribution time. METTLER TOLEDO Safeline has launched new enhancements to its Profile range of Gravity Fall metal detectors that allow manufacturers to reduce the frequency of routine performance monitoring tests through Reduced Test mode and decrease the time taken to conduct performance monitoring tests through its Automatic Test System (ATS).

    Reduced Test mode has the ability to monitor the metal detector's performance on the production line to a level of certainty that the frequency of routine performance monitoring can be significantly reduced, subject to quarantine periods.

    ATS decreases the time taken to conduct performance monitoring tests by >80% (from 3-5 minutes per line, to under 30 seconds per line). Certified test samples are assembled in discrete acrylic tubes that run up the inside face of the metal detector aperture. The automated pneumatic control transports each test sample in turn, to a defined position above the principle sensing coils within the metal detector. The test sample is then released, simulating the presence of a contaminant in free-fall under gravity.

    The ATS test is performed and monitored on the return of the test samples to their original position.

    The whole process takes less than 30 seconds to complete for a three-metal test, or less than 45 seconds for a four-metal test. This increases productivity as only one operator is required to conduct routine performance monitoring tests and time taken to perform the tests are also significantly reduced.

    In some cases, depending on the testing protocol undertaken by your business, this can lead to significant uptime advantages, improved overall equipment effectiveness (OEE) and cost savings – all highly desirable attributes in today’s demanding production environments.

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    How do I determine the initial fall height of the product when using a Gravity Fall metal detector system?

    The fall height of the detector is normally expressed from the point at which the product begins to fall to the top of the detector flange. This height will determine the product’s velocity at the point of inspection. Ideally, the fall height should be reduced to a minimum by locating the equipment as close as possible to the point of initial fall, without infringement of the ‘metal-free zone’.

    By way of general guidance, the maximum fall-height for a 150mm diameter aperture metal detector would be approximately 800mm; however, this may vary depending upon the actual detector specification. As the fall-height is increased, the distance between the detector and the reject valve must also be increased in order to maintain adequate time for the reject device to respond.

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    How reliable are Safeline's Gravity Fall metal detectors?

    Built for installation in tough environments, all METTLER TOLEDO Safeline Gravity Fall metal detector systems utilise fully welded stainless steel support frames and robust construction techniques. This leads to low maintenance requirements and maximum reliability providing the lowest overall cost of ownership. All Gravity Fall metal detection systems are sealed to IP65 with a choice of finishes to suit all applications; painted finish can be selected for use in dry, non-aggressive environments while stainless steel construction is available for more demanding applications.

    Does METTLER TOLEDO Safeline supply Gravity Fall metal detectors that are ATEX/IECEx compliant for explosive atmospheres?

    If operating in a potentially explosive atmosphere, certain Gravity Fall metal detection systems can be supplied to comply with ATEX/IECEx regulations. Please discuss your requirements with your local sales representative.

    How can a Gravity Fall metal detector enhance worker safety?

    Manufacturers are under increasing pressure to provide ever-safer working environments for their employees. The latest METTLER TOLEDO Safeline Profile Gravity Fall metal detectors can contribute to safer working practices in food manufacturing environments.

    • By reducing the frequency of metal detector testing using new RT technology, there is a corresponding reduction in the number of ladder climbs required by an operator to conduct the test, either to drop the sample through the aperture, or to access the HMI to run the test routines.
    • Emulation allows the metal detector HMI to be controlled from a variety of networked devices such as a tablet or mobile phone, again reducing the need to work at height if the HMI is installed in an awkward location, as is the case in many dry product inspection applications.
    • When ATS is used, it virtually eliminates the need to work at height to conduct most routine performance monitoring tests, and removes the requirement for line operators to have to reach across installed equipment to drop the test samples through the aperture of the metal detector.


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