Inductive sensors from Contrinex, available from PLUS Automation, are playing a vital role in food processing applications, from ensuring bottle seals are in place, to valve monitoring at a dairy plant


luminium-foil closures are commonly utilised as seals for plastic containers

filled with ketchup, mustard and other table sauces. One food-processing plant is using 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 and packed, 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. The sensors are required because, 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, downtime or potential rejection by customers. An in-line sensor system inspecting each container can confirm the presence of a foil closure, rejecting any faulty items. Each production line processes containers in batches. This means 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. Contrinex Extra Distance inductive sensors are suitable 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 suited to fast-moving production where high- speed sensing is required. The 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. The M30-diameter device can now test

the entire range of containers without the need to adjust the sensor height between batches. Other advantages include: · Reliable, repeatable in-line testing of a range of different-sized containers · Testing is completed without difficulty

at production-line speed · Immediate identification of containers

with missing closures · Elimination of manual inspection and potential batch rejection · Extended sensing distances up to

40mm In another food application, this time at a European dairy-processing plant, robust washdown inductive sensors from Contrinex, mounted on existing rotary actuators, are used to monitor control- valve status around the clock, providing real-time positional feedback to a plant- wide control system in a simple, cost- effective manner. During manufacture, milk products,

made from pasteurised or raw milk, require hygienic transportation between successive operations. Process engineers use stainless-steel pipework to transport liquid ingredients from one operation to the next. Fluid flow is managed using control valves fitted with electrical, hydraulic or pneumatic actuators. Multiple rotary-shaft valves deliver raw milk from holding tanks to each process station in sequence, maintaining specified flow rates and volumetric limits. Once processing of each batch is completed and all process vessels are

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

Washdown inductive sensors are used to monitor valve position in an application at a dairy processing plant

drained, closed-loop CIP cleaning commences. Accurate, repeatable valve sequencing is essential to prevent any chance of cross-contamination between processing and cleaning sequences. A robust, highly reliable sensor system, capable of withstanding the harsh washdown regimes in force, was needed to monitor control-valve positions during processing. Where possible, sensors must be mounted on existing rotary actuators, and real-time communication with existing plant-wide control systems is mandatory. Thankfully, sensing the position of a rotary-valve actuator is a routine task for Contrinex Classics washdown inductive sensors. These sensors interface directly with a range of industrial process controllers and provide cost-effective confirmation of control- valve status around the clock. A purpose-designed bracket, mounted on the top surface of each actuator, holds two sensors; these are positioned with the sensing faces vertically aligned, one above the other, and facing the actuator shaft. NAMUR-compatible (VDE/VDI 3845) mountings on the actuators provide a known datum for the sensors. A solid plastic disc, mounted on the shaft, carries two or more stainless-steel targets, positioned at 90˚ to each other around the outer peripheral surface of the disc. Each target occupies either an upper or a lower position corresponding to the height of one of the sensors. As the shaft rotates, opening and closing the valve, the targets pass in front of the sensing faces, triggering the sensors. These M12-diameter devices, rated to

IP68/IP69K, have all-metal bodies with PBTB sensing faces and vacuum- encapsulated electronics; each features an industry-standard PNP normally open output. Fully embeddable, and with a sensing range up to 2mm, they are suited to the hostile operating conditions of a washdown environment. Each sensor has an integral M12 connector, interfacing with the customer’s control system via a TPE-S-sheathed cable.

PLUS Automation


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