[May 2008] By investing in Alfa Laval Unique MixProof valves and ThinkTop valve control units as part of a multi-million pound plant overhaul, Unilever UK has increased throughput by 30%, made waste savings of approximately 10% and slashed energy consumption by more than a third at its Marmite / Bovril production plant in Burton-upon-Trent.
Local process engineering specialists, T Musk Engineering, carried out part of the revamp, installing 16 new vessels, alongside eight existing tanks, to be used for storage of processed brewer’s yeast. The flow of product and CIP fluids between these tanks and other key elements in the production process is controlled by the MixProofValve and ThinkTop combinations, which, in combination with a central processor, have enabled the whole process of filling, emptying and cleaning the tanks to be automated.
Prior to the revamp, the original vessels and process areas had to be isolated manually before any of these operations could be carried out. Consequently the new equipment has not only generated substantial time savings but has also reduced energy costs, water usage and improved hygiene.
The basic raw material used in the manufacture of Marmite is spent brewer's yeast. For many years this brewing by-product was seen as a nuisance rather than a potentially valuable food source. Examination of the yeast under a microscope revealed spherical and ovoid cells which the French scientist, Louis Pasteur, identified as living plants. A German chemist, Leibig, then discovered that this yeast could be made into a concentrated food product, which, though it resembled meat extract in appearance, smell and colour, was, in fact, vegetarian. The first Marmite production facility was established in Burton-Upon-Trent in a disused malting shed in 1902.
Although Burton is no longer the centre of British brewing, the town still supplies most of the spent brewers yeast that constitutes the base ingredient for both Marmite and Bovril.The current Burton-upon-Trent factory has been manufacturing Marmite and Bovril since the 1950’s and both products still enjoy such iconic status in the UK and abroad that production at the plant runs 24 hours per day 360 days per year.
The product enters the factory as a brewer’s yeast slurry from which the cell content is first separated and then concentrated in an evaporator before being transported to the storage vessels. The mixture is then passed through further filtration and evaporation. Of the 24 tanks involved in this process, one tank is being filled, another is being emptied and a third is being cleaned using a CIP system built around Alfa Laval Toftejorg Sani Magnum rotary spray heads installed in each tank.
Initially, Unilever’s engineers considered replacing the original manually-operated valves with sanitary butterfly valves. However, after further consideration they decided to use the opportunity provided by the revamp to opt for more sophisticated Unique Mixproof valves fitted with Think Top control units. As the name implies, the Unique Mixproof range is designed to enable two incompatible media to flow through the system without intermixing and is ideal for the job of isolating the product and CIP streams in the Marmite production process.
Controlled remotely using compressed air, each Unique Mixproof valve is normally closed with two plug seals forming a leakage chamber between them. When the valve is opened, the leakage chamber is closed enabling product to flow from one line into the other. Any accidental leakage flows into the chamber. The SeatClean versions installed at the Marmite factory enable the plugs and valve seat to be cleaned by means of seat lift during normal CIP operations. The valve also incorporates a balanced lower plug that absorbs pressure shocks or constant high pressures to prevent leakage and product mixing.
Each valve is equipped with a Think Top valve control and indication unit. ThinkTop employs a no-touch system which makes mechanical sensor adjustments unnecessary and ensures accuracy and repeatability. Chips built into the sensor unit detect the axial magnetic field of a magnet mounted on the valve stem and, by measuring the angle from each chip, the unit is able to calculate the precise position of the valve stem at any time.
In addition, LEDs provide a constant display of valve position, solenoids activated, set-up and instant fault indication. Linked to a PLC/SCADA based central processor, the Unique/Think Top combination has enabled Unilever to take greater control of all of their product movements and to plan and execute CIP cycles to keep energy and water usage and downtime to a minimum.
Peter Rose, Marketing Manager, Alfa Laval Ltd
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