Automating the past

Of all the process industry sectors, the food industry is the only one which has to deal with the problem of tradition. There is a strong romantic aspect to food production - everyone would like to think that their cheeses, cakes, biscuits and so on are produced to time-honoured recipes, and preferably in oak-beamed country kitchens.

The truth is very different, of course - hygienic constraints mean that even the smallest-scale commercial production entails use of stainless steel equipment. And as capacities increase, so the use of modern process techniques becomes ever more important. Companies in traditional industries often have very different approaches to incorporating cutting-edge automation techniques into their processes, however.

Gloucester-based Bottlegreen Drinks produces 'adult' carbonated drinks and cordials, with flavours such as lemongrass and ginger, spiced berry, and elderflower. Like many food and drnk companies, it used batch and continuous processing to make its drinks - at the start of each day, flavourings and syrups, fresh juices, spring water, citric acid and sugar syrup were batch-blended in a vat before being pumped into the production hall. But this approach led to problems: the time needed to measure each component into the vat and mix them exceeded the time needed for production. Production caught up with the blending process, resulting in knock-on delays in moving from one product to another.

The company considered several solutions, including increasing the capacity of the batch blending, but eventually settled on switching to continuous blending using an inline system from Bran + Luebbe. 'The continuous processing systems that we have developed overcome bottlenecks, because they can be dynamically altered to match the requirements of downstream operations,' says B+L's process systems manager, Stuart Moffatt.

The system is based around Bran + Luebbe's H-range metering pump and N-form static mixer. The pump has a variable throughput, with five separate metering pumpheads giving it a potential throughput of 500litre/hr. The pumpheads have lantern-flush plungers which allow the back of their seals to be flushed continually, preventing contamination. Bottlegreen specified 'flow/no flow' switches, which allow operators to check the presence or absence of ingredients, along with a pressure switch on the discharge to stop operation if the line becomes blocked.

'Bottlegreen required a system that would ensure high levels of accuracy in terms of bringing several different ingredients together in varying quantities and to mix them together to create a consistent product,' Moffatt says. 'With our unit, production staff can selec the ingredients for the product, set the metering and flow rates of the pumps, and start production.' Moreover, the variable speed of the system allows the company to match the blending rate to the production rate. Once production has started, the blender continuously tops up the header/buffer tank, so if there are stoppages down the line, the blender can be turned off.

Paul Martin, Bottlegreen's senior engineer, says the system has made a considerable difference. 'Before installing the system, we could get to a point in the day where another 1000-5000litres of product was needed to finish the day off, but there physically wasn't time to make this up.' When this happened, production had to be shut down, he says. 'We now have the ability to produce one product and run it through to a bulk holding tank and then. Following flushing of the relevant metering pumpheads and changing the settings, switch to another product.' The increased efficiency means that Bottlegreen now has the capacity - and the time - to invest in developing new products.

Stock responses

Another venerable product which is feeling the pressure of modern existence is Oxo, produced by Campbell's Grocery Products in Worksop. Campbell's faced the same problem as many UK businesses - reducing energy usage, to minimise liability for the Climate Change Levy.

Food production on a large site is complex, and the company needed a system which could monitor energy consumption over five separate processes. The system needed to be capable of looking at specific production zones, even down to monitoring a single machine.

Siemens provided the solution in this case, recommended a Scada system, the Simantic WinCC package, rather than a dedicated energy management package, it This was far more flexible, explains Steve McDermott, business development manager at Siemens Industrial Control Solutions. 'One of the main attractions of WinCC was the way the web navigator is seamlessly integrated; other Scada packages would have required a bolt-on internet publishing tool,' he says. This facility allows Campbell's operators to access the system from anywhere on the site via the internet,. Moreover, the system is configured so that operators can use Excel spreadsheets to input additional data.

'They only have to work with software they are familiar with, and they don't need learn to use the Scada package,' McDermott says.

WinCC is an unusual system, requiring no PLCs. Instead, the remote meters on the system add their data to the relational database on the system's hard drive using radio connections and then dynamic data exchange (DDE) links. 'Our experience has shown that WinCC is far better at handling the DDE links than other packages,' McDermott claims.

The system has helped Campbell's considerably, says energy manager Mick Blackburn. 'It has helped us achieve a massive six-figure financial saving over the last three years,' he says. 'Bearing in mind that the project cost was £70 000 overall, the payback period was much less than one year.'

Campbell's future needs and plans are also covered, he says. WinCC gives the company the ability to expand metering and report generation will help the company comply with the European Integrated Pollution Prevention and Control directive, which will affect the food industry after 2005. Internal targets will also be met, he says. 'Our target is to make savings of 3 per cent year-on-year. In some cases this could be as simple as encouraging people to turn off lights, but we could also install additional meters on items of equipment that are heavy consumers.'

While Campbell's was looking at ways to improve existing processes, South African fruit juice producer Appletiser had a more far-ranging project: moving its juice preparation plant from an artisan operation using rubber hoses, mobile pumps and buckets to a fully-automated modern batch process. This, explains APV Invensys engineering director Deon Barnard, was a far from simple operation. Natural variances in the raw materials - the balance between sugars and acids, for example - mean that strictly-set recipes are not practical.

The system installed has 31 units, 128 connections and more than 800 process phases, and uses 85 master recipes. APV, along with its automation partner Chaswill Process Technology, had to devise an automation system which could move any product from and to any point in the system. 'The only application that came to mind was WonderWare's InBatch package,' says Barnard. 'Combined with InTouch and InSQL, the solution soon began to take shape.'

The automation system allows users to 'drill down' to unit level within each part of the process, and then down further to the equipment and control module properties. They can use the InTouch environment to display any InBatch screen. Fault-finding modules within the system tell operators why phases are on hold, navigating automatically to the screen where the faulty devices are shown so that operators can see which device is causing the problem.

'Juice making was transformed from seemingly an esoteric art into a set of documented procedures within a controlled process,' Barnard says. 'The management of recipes, control of material and the overall quality control was enhanced to a point where tolerance of final product acceptance could be reduced by a significant margin.'

Sidebar: Even faster fast food

Beloved by students, derided by gourmets, Pot Noodle must be doing something right - it's Britain's best-selling instant hot snack. Demand is rising so fast that its maker, Unilever Best Foods, has automated production lines at its plant in Crumlin, Wales. The key to improving productivity is in synchronising drives throughout the process, says Unilever's project manager, Mark Edwards. 'We have upgraded all three lines with Unidrive variable speed drives from Control Techniques,' he says. 'Line three had been running Control Techniques Vector drives for ten years, and these had performed well, but we wanted to bring the whole line under PLC control and so chose Unidrive with UD773 plug-in modules to bring Profibus connectivity.'

Line three comprises several pasta mixing and processing operations, with a feed into the next section to complete the packaging process. There are 12 Unidrives on the line, varying from 1.1kW up to 7.5kW. The speed of the line is taken from a reference on the Unidrive for the rotary cutter, with a small off-set on two of the drives on the stretcher conveyor and steamer. If any drive fails, the whole line stops apart from the sheeter system, which keeps running until all the noodles currently on the line are processed through.

'The PLC only provides initiation and switches on fans and pumps,' says Edwards. 'All of the programming is on the coprocessor modules within the drives themselves.' This gives us added flexibility and means that the whole line doesn't stop unnecessarily, he adds.