A WAVE in a cup
26 December 2008
Premier Foods manufactures a range of packaged meals and soups at their site in Ashford, UK. Level probes are used to control the level of feed hoppers that supply the packing machines to fill sachets. These machines run at speeds varying from 160 to 600 packages per minute. The feed hoppers vary in size and use various agitators and vibrators to flow the powders.
VEGAWAVE vibrating fork device
One machine is dedicated to packaging soup powder in ‘cup-a soup’ variety sachets at a rate of 160 per minute. The challenge is to handle differing flavours and consistencies of powders. Some are drier, some have larger particles, others more adhesive, as some of the ingredients contain minute amounts of natural oils. To ensure even flow and mixing, the hoppers incorporate a small rotating agitator. Previous level switches had reliability problems, particularly when products were changed over.
Photo: On the left is the view inside the hopper before the switch was fitted. The agitator is in the centre. In the right photo, the vibrating switch is installed in the hopper just to the right of the agitator. Note the "tuning fork" that extends into the soup powder.
The solution was to use a VEGAWAVE vibrating fork device with remote electronics housings and quick release, hygienic fittings to enable fast removal and clean down between product changes. The units have proved reliable with different products running through the machine. The design is robust enough to work reliably even next to the agitators inside the small hopper.
Because it mounts from any orientation, it also has an advantage over proximity-based detectors, which need a polymer window into the vessel. There is a concern over this type of window, should it crack or chip, the minute plastic shards can be almost impossible to detect.
Vibrating level switches combine mechanical detection—using the damping of a vibrating element—with reliability of solid-state electronics. Self-checking is built in, electronic monitoring of the vibration frequency means that any damage, very high build-up, or device failure makes the switch an inherently safe device. Vibrating technology is also easy to set up compared to capacitive techniques and more reliable when compared to rotating paddle devices.
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