| Detector Configuration | Conveyor-type metal detector with a food-grade stainless-steel frame and automatic reject device | It can inspect packaged or unpackaged biscuits continuously while removing contaminated products from the production flow. | Choose a configuration that matches the conveyor layout, biscuit dimensions, packaging material, and required production speed. | Inspect the frame, reject mechanism, guards, and cable connections at least once per shift. |
| Suitable Metal Types | Ferrous, non-ferrous, and stainless-steel contamination | Different metal types have different detection characteristics. Stainless steel is often more difficult to detect than ferrous metal. | Test the detector with certified ferrous, non-ferrous, and stainless-steel test pieces under actual production conditions. | Verify all three test categories according to the plant's food-safety plan and documented testing schedule. |
| Typical Aperture Size | Approximately 300–600 mm wide and 100–250 mm high, depending on the product and conveyor | A smaller aperture generally provides better detection sensitivity, while a larger aperture accommodates wider or taller products. | Use the smallest practical aperture that allows the largest product and package to pass without contact or blockage. | Keep the aperture clear of flour, crumbs, plastic film, and product accumulation. |
| Indicative Detection Sensitivity | Common production targets may range from about 0.8–1.5 mm for ferrous metal, 1.0–2.0 mm for non-ferrous metal, and 1.5–2.5 mm for stainless steel | Actual sensitivity depends on aperture size, product effect, conveyor speed, product orientation, moisture, salt content, and packaging. | Do not select equipment solely by a catalogue value. Confirm performance using the actual biscuit recipe, package, and operating speed. | Record test results and investigate any gradual loss of sensitivity rather than simply increasing the sensitivity setting. |
| Conveyor Speed | Typically about 20–40 m/min for biscuit inspection, subject to detector design and product spacing | Speed affects the available inspection time, reject timing, product stability, and detection performance. | Leave consistent gaps between products and confirm that the reject delay matches the actual conveyor speed. | Check belt speed, belt tracking, encoder operation, and reject timing after maintenance or line changes. |
| Product Effect | Low-product-effect operation with automatic compensation or product-specific programs | Biscuits may contain salt, moisture, inclusions, or conductive packaging materials that can create false signals. | Store separate programs for different recipes, package sizes, moisture levels, and film structures. | Revalidate the program whenever the recipe, supplier, package, temperature, or production speed changes. |
| Reject System | Air blast, pusher, flap, or belt-stop reject system selected according to product size and speed | The detector is only effective when contaminated products are reliably separated from acceptable products. | Use a reject confirmation sensor, reject bin, and locked or monitored collection area where practical. | Test the reject action, reject confirmation, bin-full alarm, and fail-safe response at the start of each production shift. |
| Conveyor Belt | Food-grade, low-metal, non-magnetic belt with a design suitable for dry cleaning | Metallic components near the search head can cause interference and unstable readings. | Keep metal fasteners, tools, brackets, and unapproved belt components outside the detector's exclusion zone. | Inspect the belt for cracks, embedded metal fragments, excessive wear, and flour buildup. |
| Hygienic Construction | Stainless-steel construction, smooth surfaces, sealed electrical enclosures, and easy access for cleaning | Biscuit lines generate crumbs and flour, so poor hygienic design can increase contamination and downtime risks. | Position the detector where operators can clean around and beneath it without disrupting adjacent equipment. | Follow the approved dry-cleaning or wet-cleaning procedure and prevent water from entering sensitive electrical areas. |
| Electrical Supply | Commonly 220–240 V AC, 50 Hz in mainland China; confirm the actual site supply before ordering | Incorrect voltage, grounding, or power quality can cause alarms, unstable operation, or equipment damage. | Provide a dedicated, properly grounded circuit and install surge protection where the site power supply is unstable. | Check grounding, plugs, isolators, cable glands, and alarm-free restart after planned power interruptions. |
| Environmental Conditions | Typical operating range: approximately 5–40°C with controlled condensation and moderate humidity | Temperature changes, condensation, vibration, and electromagnetic interference can affect detector stability. | Install away from large motors, variable-frequency drives, welding equipment, strong vibration, and water spray. | Monitor condensation, vibration, nearby electrical modifications, and unusual background noise or false rejects. |
| Installation Position | After baking and cooling, and preferably after the final packaging stage when package inspection is required | Inspection after the last possible contamination point helps prevent contaminated products from reaching storage or shipment. | Provide adequate straight conveyor length before and after the detector and avoid placing it immediately beside metal transfer points. | Confirm that the detector remains level, stable, accessible, and correctly aligned with upstream and downstream conveyors. |
| Calibration and Validation | Commissioning test, product-specific setup, documented performance verification, and routine challenge testing | Metal detection performance must be demonstrated under real operating conditions, not only during no-load testing. | Use traceable test pieces and define acceptance criteria, test frequency, responsible personnel, and corrective actions. | Keep calibration and verification records, including date, product, speed, test piece size, result, and corrective action. |
| Routine Testing Frequency | At start-up, after product or setting changes, after stoppages, and at intervals defined by the food-safety system | Frequent testing helps identify changes caused by recipe variation, equipment movement, or reject-system failure. | Use a written checklist and test both detection sensitivity and automatic rejection. | Review trends in false rejects, missed tests, alarms, and failed verification results. |
| Operator Training | Training on product selection, test-piece handling, alarm response, reject isolation, cleaning, and recordkeeping | Human error can undermine a technically capable detection system. | Limit access to parameter changes and require authorization for program creation or sensitivity adjustments. | Refresh training after process changes, audit findings, repeated test failures, or personnel changes. |
| Best Choice for Most Biscuit Lines | A conveyor metal detector with product-effect compensation, stainless-steel construction, automatic reject confirmation, and product-specific programs | This combination balances sensitivity, hygienic design, production continuity, and operational control. | Finalize the choice only after a live product trial using the actual biscuit, packaging, conveyor speed, and operating environment. | Use preventive maintenance, documented verification, clean installation practices, and timely replacement of worn components. |
