HIGH spirits

Located at an altitude of over 300m, midway between Perth and Inverness, Dalwhinnie distillery is the highest in Scotland. A division of Scotland's largest distilling group United Distillers, Dalwhinnie performs 10 `mashes' each week, to produce 28 000 litres of spirit from its two stills.

United has recently spent £2.5million installing automated control systems, part of a £12million spend on similar modernisation in six of the company's malt distilleries.Until the latter part of 1996 Dalwhinnie's processes were manually controlled.

Alan Rutherford, United's Scotch whisky production director, told PE: `Distillers had two main objectives for the control system; improving operating efficiency and the rapid collection of management data. We wanted to achieve improvements in the distillery's economic performance and in product consistency.

`Malting has changed a bit over the years,' he added, `because of the development of different varieties of barleys. But the biochemistry of malting has not changed. We are forbidden from adding enzymes or chemicals to the process because of the legal definition of whisky.'

Double measures

Dalwhinnie operates a range of sequential processes with contrasting demands. Malt intake and cleaning in place are suited to programmable logic controllers. Measurement of temperature and flow rates and continuous control processes such as fermentation and heating of the stills are better served by distributed control systems architecture.

Moore Products' APACS system resolves this dilemma by offering both DCS and PLC capabilities combined in a single control system. APACS, Moore claims, can also cut the cost of engineering the system with the application of 4-mation, its dedicated IEC1131-compliant programming language.

The Moore Products system at Dalwhinnie involves a control panel connected to temperature, level and flow sensors that are installed at all key stages of the process. Control system outputs drive the valves and pumps to move product and ingredients.

A number of operator screens are provided, giving overviews of the whole process or more detailed views of particular sections such as mashing and distillation. The screens show an alarm banner that alerts operators to out-of-tolerance process conditions.

Recipes for the product are held in control system and batches are executed on instruction from the operator. Output from the two stills - initially low wines, then the collected spirit fraction, and finally feints - remains under the control of the distiller. A glass and brass spirit safe allows the distiller to see the distillate and judge by eye and experience when to collect spirit and when to recycle for a second distillation.

To maintain the quality of the product the plant is hygienically cleaned and sterilised by a cleaning in place (CIP) cycle. Here again, automatic control saves time and effort on an essential but what can be a rather tedious task.

On-line remote access to real-time data has also speeded up the exchange of information with United's headquarters in Edinburgh, claims Rutherford.

Previously, a weekly report based on manually recorded data was mailed to Edinburgh from Dalwhinnie. At best, therefore, the management's information would be a week old.

With the APACS system the information is available when needed via a modem, gathered directly into spread sheets and other management information tools from the control system. Equally important, modem links connect the Dalwhinnie distillery to Moore Products' support office to maintain the reliability of the control system.