Double cream contracts

Process engineers in industries such as chemicals and pharmaceuticals know all too well the changes wrought by the mergers and acquisitions of recent years. But few others are immune from the trend. Following its acquisition of Unigate's dairy and cheese business in July 2000, for example, Dairy Crest set out to rationalise its milk production and processing operations around the country.

The cornerstones of that restructuring were to be two new 'super dairies' at Chadwell Heath in Essex and at Severnside in Gloucestershire. Chadwell Heath was opened in 2001 and Severnside came fully on stream in early 2003, replacing three older dairies at Thornbury in south Gloucestershire, Kidlington in Oxfordshire, and Marshfield in Cardiff.

In a contract worth around a third of Dairy Crest's overall £39 million investment in the Severnside site, Lichfield-based contractor FMA Process Engineering successfully commissioned all five key phases of the new liquid milk dairy. The contractor's main responsibilities covered all aspects of process design and supply, including the implementation of process control and management reporting systems.

Severnside was designed to process up to 500 million litres of liquid milk a year and is Dairy Crest's centre for the processing, packing and distribution of milk in cartons and plastic bottles to multiple retail customers throughout the Midlands, Southern England and Wales. In addition to this core business, the dairy also produces 'added value' products such as organic and regional milks, fresh flavoured milk drinks, milk shakes and potted cream.

Phase one of the project covered the manufacture of cream products that were transferred to Severnside from a former St Ivel facility. Phase two saw the production of organic milks - a stage of the project that included bringing in for re-use plant and equipment from the Thornbury dairy. The next two phases of the project incorporated the production of Welsh (from Marshfield) and other regional milks and involved the commissioning of extensions to the equipment supplied for the first two phases. The final phase was the installation of a dedicated production unit for milk-shake bases destined for McDonalds.

Fast track project

To meet the tight deadlines laid down by Dairy Crest, FMA had to 'fast track' the project at all stages of design, installation and commissioning. Under the leadership of a project director, FMA's multi-disciplined team established close working relationships with Dairy Crest's own plant implementation team to ensure the smooth running of the project through all its phases.

The project management structure embraced both mechanical and electrical design and installation and the systems side of the super dairy. On the M&E front, FMA acted as project managers for key third-party equipment suppliers such as Tetra Pak (process and packaging equipment), Realm (stainless steel vessels, pipes and fittings) and Moody, the Retford-based specialist in the supply and refurbishment of used equipment for the dairy, food and beverage industries.

On the systems side, however, FMA was able to draw on its origins as a process control systems house. All control systems for Severnside were designed and managed in house from Lichfield. To give the integrated production control required by Dairy Crest, FMA developed systems incorporating the latest fieldbus applications of ASi and Profibus PA and DP. Rather than go for any one preferred supplier, FMA entrusted various elements of the plant control system to a selection of what it terms 'best of breed' control vendors, including Siemens, Danfoss, IFM, and Endress + Hauser.

Wide-ranging control

The overall scope of the control system includes three Compaq servers (one web server, one database server, and one for the iFIX I/O of GE Fanuc Intellution's Scada system). There are 12 iFIX client machines, and three primary PLCs interfacing with 10 ancillary PLCs from a variety of vendors. All told, there are 1480 intelligent field devices - valves, pumps, variable speed drives, and so on - and 230 instruments measuring the basic parameters of flow, level and temperature.

The way in which third-party suppliers were involved in the overall scheme of the project can be illustrated by the work carried out by TCS Automation. Working in conjunction with Alfa Laval and Bosch, TCS's part of the project involved the control and cleaning of aseptic valve manifolds supplying UHT product from an Alfa Laval Steritherm heat exchanger to three Bosch aseptic filling machines. Four Mitsubishi F1 PLCs were used in this sub-control system - one each for control of the Bosch filling machines, and the fourth providing dedicated control of the cleaning-in-place system that cleans all the lines, manifolds and fillers.

One of the many innovative features of the Severnside super dairy is its finished product handling area. Designed, custom-built and installed to order by Finnish materials handling specialist Elopak, the materials handling system consists of a barcode-based, roll container delivery system, together with a new cold storage area.

Setting standards

Predicted by Dairy Crest's chief executive, John Houliston, 'to set new industry standards for quality, service and efficiency', the system begins with receipt of empty polybottle containers (produced on site in a dedicated facility). Roll containers (trolley-like devices) are de-nested and placed into the system for washing and transport to the loading station. After the fresh milk has been filled into the polybottles, the bottles are conveyed to the downstream handling area where they are automatically inserted into the roll containers. An intelligent automatic transfer wagon then gathers, unloads and conveys the bottles to the cold-store area, ready for distribution to the retail outlets.

Sophisticated product handling such as this, of course, is now becoming almost a prerequisite in modern process plants whatever the sector. Most plants are part of a well-defined supply chain and the reliability of that chain rests on the plants' efficient operation. For its two super dairies Dairy Crest has entrusted its supply chain planning to Prescient Systems, whose advanced planning and scheduling software is being used to improve scheduling, processing and packing efficiencies. The Prescient software interfaces with Dairy Crest's existing manufacturing execution system (MES), previously installed at Severnside by FMA Engineering.