Metal detection for liquids and pumped food
Anything that can be pumped can be inspected in the pipe. That is usually better than inspecting it afterwards in a jar, because the detector sees a thin, consistent cross-section instead of a thick container.
Sources in a liquid process
- Mixer and homogeniser wear — blades, seals and fasteners
- Pump components, particularly on abrasive or high-solids product
- Filter and strainer mesh, which sheds wire when it fails
- Ingredient intake, where powders and additives arrive from sacks and big bags
Conductivity is the whole problem
Salted, acidic and high-moisture liquids conduct well. That produces a strong, continuous product effect — and unlike a solid product on a belt, the liquid fills the entire aperture continuously, so there is no gap between products for the detector to reference against.
Modern signal processing handles this, but the achievable sensitivity is genuinely product-dependent. A neutral, low-salt product may reach figures close to the reference; a heavily salted sauce will not. There is no honest way to quote a number without testing.
Pipe diameter is the other lever. If the detector can be placed where the pipe is narrower — before a manifold rather than after, for instance — the sensitivity improves measurably at no extra equipment cost.
What can be built into a pipeline installation
- Integrated reject collection bucket. Diverted product lands in a dedicated container built into the unit rather than on the floor — and it can be locked where the detector is a critical control point.
- Teflon product pipe. Specified where the product or the cleaning regime demands it, and supplied together with a Teflon piston for high-temperature applications.
- Piston for high temperatures. A stainless piston for dense product, or the Teflon piston and product tube for applications above 100 °C.
Filler electrical connector. Allows direct integration with filling machines for synchronized operation — the detector and the filler act as one machine instead of two devices timed by hand, so a detection stops and diverts at the right point in the filling cycle.
Not sure what can be detected in your specific product? Send us a sample. You get a written test report with false reject rate and probability of detection — free and normally within a week.
What we typically supply
Pumped product
Pipeline detector with hygienic coupling and automatic reject valve.
Filled containers
Conveyor system after filling, for jars, bottles and pouches.
Pipeline integration
Free-fall detector at powder and additive intake.
Where should the reject go?
The reject valve diverts a volume of product around the detected metal. On an expensive product that volume is worth calculating: at a given flow rate and valve response time it can be several litres per event.
It is also worth deciding in advance what happens to diverted product. On most standards it cannot simply go back into the batch. Specify a container, and make it lockable if the detector is a critical control point.