Sensors help keep ketchup fresh

A food-processing plant trusts Contrinex’s sensors to help it ensure plastic bottles, filled with liquid food products, are hermetically sealed and its customers kept safe. Prior to the containers being capped, a long-distance inductive sensor, positioned directly over the packaging line confirms the presence of an aluminium-foil seal over the top of every container.


Aluminium-foil closures are commonly utilised as seals for plastic containers filled with ketchup, mustard and other table sauces. At a food-processing plant, closures are applied to filled containers passing along an automated production line, sealing the contents ready for capping and bulk packaging.

From time to time, equipment malfunctions can occur and containers leave the sealing station without closures in place. If unsealed containers are not detected prior to capping, entire batches of product may require manual inspection, resulting in lost production, down-time or potential rejection by customers.

An in-line sensor system inspecting each container could confirm the presence of a foil closure, rejecting any faulty items. Each production line processes containers in batches. The system must accommodate containers whose heights vary by up to 20mm, without adjustment of sensors between batches as successive batches may comprise containers of differing sizes.

Customer Solution

Contrinex Extra Distance inductive sensors are ideal for this application, with the M30-diameter units operating reliably at sensing distances up to 40mm; a single sensor thus accommodates the entire range of container heights. Robust construction with chrome-plated brass bodies and PBTP sensing faces ensures that these devices are suitable for a busy production environment.

A single sensor, located immediately after the sealing station and positioned directly above the production line, provides reliable, repeatable and fast detection of the aluminium-foil closures. With a switching frequency of up to 100Hz, this Extra Distance unit is well suited for fast-moving production where high-speed sensing is required.

This Contrinex inductive sensor has an industry-standard PNP normally-open interface and an integral M12 cable connector, allowing easy removal and replacement of individual sensors for maintenance. Connection to the customer’s test equipment is via a flexible PVC-sheathed cable.

With an unmatched combination of 40mm sensing distance in an M30-diameter device, the customer can now test the entire range of containers without adjusting the sensor height between batches. Contrinex Extra Distance inductive sensors deliver exceptionally reliable test results at production-line speed, without interruption.

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