Control Panel Does The Wright Mix

The Max wright Limited panel which controls the production of some products at the bottling and canning plant of Britvic Soft Drinks in Widford, near Chelmsford, is a good example of the increased flexibility in the process control environment being demanded by manufacturers these days. Programs held within the Siemens programmable logic controller (PLC) enable Tango, Pepsi or any other type of drink to be mixed, according to production requirements.

This latest extension to the plant came on stream in April 1996 and immediately started round-the-clock operation. In a 12-hour shift, nearly 60,000 litres roll off the production line in 180,000 bottles.

The Widford site is also Britvic's main research and development centre. In this area too the versatility of the mixing plant is put to good use, allowing new drink formulations to be produced quickly and accurately for evaluation.

Information on all the different mixtures is held in memory and displayed on a screen built into the Max Wright Ltd. Panel. The man-machine interface (MMI) allows the operator to control the manufacturing process, which typically comprisses transfer of ingredients from two outside storage silos and subsequent batch blending of water and syrup in two product mix tanks inside. Before a new production run starts, in-situ cleaning of the stainless steel tanks and pipework is required and this is instigated by the MMI which talks to a seperate CIP (cleaning-in-place) equipment controller.

There are unavoidable variations in the concentration of syrups delivered to Britvic and these are detected in the laboratory by analysing the first few bottles of each new batch. Adjustments to the quantities of the ingredients may be made easily by the operator at the MMI, which also incorporates a plant status screen for monitoring tanks levels and liquid flow rates.

System monitoring detects any errors such as drive or valve malfunction, in which case start-up is aborted or, if the system is in the middle of a batch run, production is automatically halted by closing all valves and stopping the pumps. When the error has been corrected, production is resumed quickly by pressing the fault reset and start pushbuttons.

Main contractor for the project was Penborn Technical Services, Brentford, whose electrical projects engineer, Andy Conway, said, 'We have worked with Max Wright for over 12 years and regard them as one of the better electrical panel builders on our books. In particular, they understand the fundamentals of the process industry. The company was able to supply the panel in a short time scale, as they produce everything in-house - complete electrical build, software writing for the PLC and operator interface, and even manufacture of the sheet metal cabinets. This was a great benefit to us as Britvic were pressing for early completion of the project.'

Reliability of the equipment supplied was also paramount, as lost production in the drinks industry is very expensive. Furthermore, accuracy is essential in the production of 'food' products which must adhere strictly to their stated composition.

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