Level switch copes with yeast head22 February 2019

Danish brewer Carlsberg has resolved a production problem in a recently-built production centre in Fredericia, Denmark, thanks to a special sensor from Baumer.

Yeast is an essential ingredient of the brewing fermentation process, where it is used to convert the glucose in the wort to alcohol and carbon dioxide gas, giving the beer its alcohol content and its carbonation. However, yeast foam can be a problem when trying to accurately and reliably measure fluid level.

When fermentation is nearly complete (a process taking around 4 to 6 days), most of the yeast will settle to the bottom of the fermentation tank. It is then removed and reused for several fermentation processes, before finally being stored in an excess yeast tank and sold off as animal feed. In this final stage of filling the excess tanks, Carlsberg experienced problems with overflow, due to the heavy build-up of foam that prevented triggering of the traditional level-measuring technology, vibrating forks, installed in the tanks. (In normal conditions, the resonant frequency of vibration of the tines of the fork changes when immersed in a liquid).

The solution provided by Baumer was the Cleverlevel switch, which utilises a different sensing technology: frequency sweep. According to Baumer, an electrode integrated in the tip of the sensor forms a capacitor together with the environment forms a capacitor. The medium’s dielectric constant determines the capacity value. This, together with a coil in the sensor electronics, creates a resonance circuit. The measured resonance frequency can trigger a switching signal once it reaches a programmeable threshold.

The switch features an installation depth of 15mm and a self-draining sensor tip. The device can be configured via the dedicated software; for example, its switching range can be adjusted to ignore foams during maximum or minimum monitoring.

Lone Højbjerg Petersen, Carlsberg maintenance coordinator, says: “The CleverLevel switch has solved the problems we were experiencing with overflow in the excess tanks. We are now considering using the switch in our CIP (Clean-In-Place) caustic tanks, where we experience similar issues with foam and overflow”.

Will Dalrymple

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