Pipeline Metal Detection for Powders, Granules, Pastes, and Liquids

Why Some Materials Need Inspection Before Packaging

In continuous processing lines, not all products arrive at the packaging station in a form that is easy to inspect after filling. Powders, granules, pastes, liquids, and semi-solid materials are typically conveyed through enclosed pipelines, hoppers, or pumping systems before they reach the filling or sealing machine. By the time the product is inside a sealed bag, bottle, or container, any metal contamination present in the material stream is already locked inside the finished package.

Inspecting these materials before they enter final packaging is both more effective and more economical than attempting to detect contamination in sealed finished goods. Pre-packaging pipeline inspection intercepts contaminated material at the point where it can still be diverted or rejected without wasting packaging materials, and before the contamination risk is transferred to the consumer. For continuous processing lines handling bulk materials, pipeline metal detection is the appropriate inspection strategy.

Powder and Granule Inspection

Powdered and granular materials present specific contamination risks because they are typically produced, blended, and conveyed through equipment with metal contact surfaces — mixers, conveyors, mills, and sieves — where wear fragments can enter the product stream without visible indication. The enclosed nature of powder and granule handling systems means that contamination, once introduced, can be distributed through a large volume of product before it is detected by downstream quality checks.

Pipeline metal detection is applicable to a wide range of powder and granule products, including milk powder and dairy powders, seasoning blends and flavor powders, pharmaceutical granules and active ingredient powders, plastic granules and polymer compounds, chemical powders and industrial mineral products, and food ingredient powders such as starch, flour, and protein concentrates. Each of these materials moves through enclosed pipelines under gravity, pneumatic conveying, or screw auger systems, making a pipeline-mounted metal detector the natural inspection point.

For production lines where powder or granule materials are filled into bottles, bags, or pouches after inspection, integrating pipeline metal detection upstream of the filling station ensures that only verified material enters the packaging. Powder Filling Machines from Keypack Intelligent are designed to work in conjunction with upstream inspection systems, supporting a complete pre-packaging quality control workflow.

Paste, Liquid, and Semi-Solid Materials

Pastes, viscous liquids, sauces, gels, and semi-solid materials require a different inspection approach than dry powders or finished packaged goods. Their flow characteristics — high viscosity, non-uniform density, and sensitivity to shear — mean that they cannot be inspected on a standard flat conveyor belt system. They must be inspected inline, within the pipeline or transfer system that moves them from processing to filling.

Common paste and liquid products that benefit from pipeline metal detection include tomato paste, fruit purees, and sauce concentrates; dairy products such as yogurt, cream, and processed cheese; pharmaceutical liquids, suspensions, and semi-solid dosage forms; cosmetic and personal care products including creams, gels, and lotions; and industrial adhesives, lubricants, and chemical compounds. In each case, the product is pumped or gravity-fed through a pipeline, and the metal detector is installed as an inline component of that pipeline system.

The inspection challenge for viscous and semi-solid materials is that product effect — the electrical signal generated by the product itself passing through the detector coil — can be significant and variable. A pipeline metal detector designed for these materials must be capable of learning and compensating for product effect to maintain detection sensitivity without generating excessive false rejections.

Fully Enclosed Design for Processing Lines

The Pipeline Metal Detection MH200 is designed as a fully enclosed inline metal detector for pre-packaging inspection of powders, granules, pastes, liquids, and semi-solid materials. Unlike conveyor-based metal detectors that inspect products after packaging, the MH200 is installed directly in the product pipeline, inspecting the material stream continuously as it flows through the detection aperture.

The fully enclosed structure eliminates the exposure and contamination risks associated with open conveyor inspection, making the MH200 suitable for hygienic processing environments where product containment and cleanability are required. The detection head is constructed with an epoxy resin body, providing chemical resistance and structural integrity in wet or corrosive processing environments. The pipeline connection interfaces are designed to integrate with standard industrial pipeline fittings, simplifying installation into existing processing lines.

Detection and Control Features

The MH200 incorporates a dual balanced coil detection architecture, which provides stable, high-sensitivity detection by comparing the signal from two balanced receiver coils. Any disturbance caused by a metal contaminant passing through the detection zone creates an imbalance between the two coils, triggering a detection event. This balanced coil design provides inherent rejection of external electromagnetic interference, improving detection reliability in industrial environments with variable electrical noise.

Digital signal processing (DSP) handles the detection signal analysis, enabling precise discrimination between product effect signals and genuine metal contaminant signals. The system includes automatic product effect learning, which allows the detector to characterize the electrical signature of the specific product being inspected and compensate for it during normal operation. Automatic phase tracking continuously adjusts the detection phase angle to maintain optimal sensitivity as product temperature, moisture, or composition varies during a production run.

The control system stores up to 99 product programs, allowing rapid changeover between different materials without manual recalibration. An automatic rejection system is integrated with the detection output, triggering a rejection event when a contaminant is detected and diverting the affected material away from the downstream filling or packaging equipment.

Confirmed Technical Parameters

• Pipeline diameter: 200 mm — suitable for medium-volume powder, granule, paste, and liquid transfer pipelines.
• Throughput: Up to 1,000 kg/hour, depending on product density and flow characteristics.
• Power supply: AC 220V, 50–60 Hz — compatible with standard single-phase industrial power.
• Applicable materials: Powders, granules, pastes, liquids, and semi-solid materials.
• Detection head construction: Epoxy resin body for chemical resistance and hygienic design.
• Product programs: 99 storable product settings for multi-product production environments.

Where MH200 Fits in a Factory Line

The MH200 is designed to be installed at the point in the production process where the material transitions from bulk processing to packaging — typically between the final processing or blending stage and the filling machine inlet. This positioning ensures that all material entering the packaging system has passed through the metal detection checkpoint.

Typical installation positions and applications include food processing lines handling sauces, pastes, and liquid ingredients before filling into bottles or pouches; pharmaceutical granule screening lines where active ingredient granules are transferred from granulation to capsule or tablet filling equipment; chemical powder monitoring systems where bulk powders are conveyed from storage or blending to packaging; plastic granule inspection lines where polymer compounds are transferred from compounding to bagging or silo storage; and pre-packaging metal detection for any continuous processing line where the product is in a flowable state before final packaging.

In each application, the MH200 provides a documented, automated inspection record that supports quality system requirements and regulatory compliance for metal contamination control.

Select the Right Pipeline Metal Detector for Your Process

Pipeline metal detector selection depends on material type, pipeline diameter, product density, flow rate, detection sensitivity target, and the rejection method required for your specific process. A system configured for free-flowing dry powder will have different phase settings and rejection timing than one handling a viscous paste or liquid product.

Contact Keypack Intelligent to review your material type, pipeline diameter, product density, detection sensitivity, and rejection method before selecting a pipeline metal detector. Our application engineers will help you define the right configuration for your processing line and quality requirements.