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August 17, 2022


The popularity of Fortress Technology’s Gravity Stealth metal detectors continues unabated. A critical part of most food production processes, inspecting and removing metal contaminants in upstream free-falling dry applications, Fortress draws attention to several recent enhancements designed to advance productivity, enhance safety and maintain HACCP compliance in the busiest of food factories.

With productivity being such a critical measurement of output per hour, machine uptime on any fast-moving gravity inspection line is critical. Custom manufactured to accommodate different food factory layouts, including mezzanine floors, ceiling mounts, between product chutes and hoppers, and even integrated alongside a checkweigher, the Fortress Stealth Gravity metal detector is packed full of useful labour and time saving features. Including digital automatic testing to eliminate production downtime, plus accurate, high speed reject capabilities.

Offering best-in-class detection of magnetic and non-magnetic metals, Fortress Gravity Metal Detectors are increasingly an everyday sight on flour, rice, cereal, sugar, powder and grain production lines.

“There is always value to be gained from adding upstream detection systems to most processes,” explains Fortress Commercial Manager Jodie Curry. “Machines upstream often make it easier to detect contaminants, trace to their source and potentially alert staff to equipment failures before they become catastrophic and potentially trigger huge recalls.”

Scanning raw materials as ingredients come into the factory is prudent for many reasons.  Although in most instances these ingredients would be inspected by the supplier, a re-inspection will help to doubly ensure that suppliers are complying and hold them accountable for ingredient quality, reaffirms Jodie “Of course, the most notable benefit is preventing metal from entering the production process in the first instance. Rejecting at the end of the line is typically the most expensive phase.”

For hazardous locations, such as flour factories or chemical plants where the application presents a combustible explosion risk, Fortress supplies clear ratings to meet the defined danger standards. Always mindful of real factory conditions, the robust Gravity Metal Detector is built to be sturdy and stable enough to withstand vibrations and temperature changes without compromising performance.

Available in a selection of food-grade anti-static aperture in-feed pipe sizes, including 75mm, 150mm and 200mm, Fortress Gravity Metal Detectors apply powerful Digital Signal Processing technology to identify the smallest of metal fragments. Operatives are instantly alerted to any detection by an audible and visual alarm. A reject confirmation alert verifies that the reject device has operated correctly during every reject.

An easier clean

To remove metal contaminants from good product flow, most Fortress customers now specify the company’s new retractable easy clean diverter valve reject system. IP69K-rated, rather than tubular supports or struts, the new Fortress Gravity design features open supports and fewer welds. Making it easier to identify potential areas where product material can accumulate, and much faster to sanitise.

Overcoming another longstanding challenge with Gravity systems – gaining access to the enclosed flap-style reject mechanism and removing it from service for deep cleans and maintenance – Fortress has engineered a retractable reject unit. By placing on a carriage, processing operatives can quickly disconnect, gain access to working parts, clean and slot back into place, with minimal business disruption.

Average clean times now take operatives a matter of minutes. Jodie confirms: “With open areas and smoother surfaces, operatives can now access and clean their Gravity Metal Detectors much faster. Not only does this reduce machine downtime, it also speeds up the changeover process from one application to another.”

Safety at heights

To successfully comply with application-specific production standards, food processors also need an appropriate and effective testing system. Defined by the audit process of industrial metal detectors and the criteria set out by each retailer Code of Practice (COP), tests are typically scheduled throughout the day at hourly intervals to confirm the inspection system is repeatedly identifying all potential metal contaminants.

Manually performing these regular tests on Gravity Metal Detectors can be especially time consuming. The degree of accuracy could also be considered questionable. Mainly due to challenges of accessing machinery positioned at height. “It is virtually impossible to time and again replicate a metal contaminant passing through the exact centre of the product flow within the aperture in free-flowing applications,” notes Jodie.

“One of the biggest pitfalls of manual testing in Gravity applications is dropping the test sample from a height, through the centre of the product flow where the signal is the least sensitive,” she highlights. With many Gravity metal detectors located near product silos above production lines, climbing up to perform this task manually is usually a two-person job and brings with it some significant safety risks.

To solve this dilemma, Fortress created Halo Automatic Testing. An alternative to manual performance testing, without interrupting production, Halo mimics the signal disturbance in the centre of the aperture, without having to physically pass a metal contaminant through the metal detector or flush out a sample. In addition to reducing operational costs, Halo testing is proven to reduce waste and product rework.

Through the incorporation of all these innovative features, Fortress asserts that its popular process-centric inline Gravity applications are now internationally regarded among the safest to operate and maintain.