Digital communication boosts process accuracy

Edited by the Engineeringtalk editorial team May 15, 2006

A project for the Berlin Schultheiss Brewery illustrates how Profibus PA fieldbus technology can exploit the advantages of digital communication with measuring instruments in new systems.

Because of the success of Profibus DP systems in filling and packing processes in the food and beverage industry, some of the first Profibus PA systems were installed on process control applications in the large German breweries: blending such modern control capabilities with the art of the long established brewer has been a major achievement.

The Schultheiss breweries have produced beer in and around Berlin for well over 100 years, and at various stages their breweries have been the largest in Germany.

One of the original Schultheiss brewery sites is now an arts and culture centre.

Beer production is now located in a relatively new plant to the West of the city.

Schultheiss is famous for their Berliner Weisse, a top-fermented bottle-conditioned wheat beer, made with both traditional warm fermenting yeasts and lactobacillus culture.

Experts describe the Berliner Weisse as a very light wheat beer, with a clear pale golden straw colour.

In line with the Schultheiss corporate philosophy to use state-of-the-art brewery technology and to maintain the best possible consistency in control, the company opted for measurement engineering based on Profibus PA fieldbus technology, when expanding fermentation and maturing capacity in 2002.

Sudmo, a specialist in the automation of food, chemicals and pharmaceutical plants, handled the process control engineering and automation aspects of the expansion project.

With 37 process fermentation tanks to control, the simplified cabling and commissioning procedures inherent with Profibus PA systems saved time on installation, and particularly in the associated documentation.

The aim of the automation project is to improve productivity by minimising the fermentation and maturing process control interventions that have to be performed manually.

The processes require precise temperature control, via automatic coolers, to maintain product quality and consistency.

Endress+Hauser, specialist in measurement engineering, not only supplied the measuring instruments but also provided consulting services for integration of the measurement data into the PLC, in order to meet the high demands in terms of measuring accuracy.

Precise automatic temperature and pressure control ensures a short fermentation time with optimal quality criteria.

The tanks and glycol cooler systems are equipped with fast-responding, high-precision pressure gauges (37 units) and temperature gauges (72 units) for that reason.

Even though high-quality measuring instruments are used, the controller unit accuracy required is 0.14C, and this can only be achieved using the digital data transfer possible using the Profibus PA network: a 4-20mA analogue based system would not have had this capability over the range required.

All the production processes are clearly documented with process reports and error histories.

Graphical data processing allows a detailed analysis of the processes.

From the data it is possible for the operators to detect any deviations from the optimal fermentation process immediately and initiate optimisation measures, when needed.

The Profibus PA system divides the fermentation process up into a maximum of 15 accurately defined individual steps, allowing flexible adaptation of the system, by choosing the separate procedures and files to produce the different types of beer.

New formulas or modifications can be integrated into the system quickly.

When the formula has been called up and the batch number assigned, the fermentation process is started.

This project for the Berlin Schultheiss Brewery illustrates how Profibus PA fieldbus technology can exploit the advantages of digital communication with measuring instruments in new systems.

Major benefits were found in the short installation and commissioning phases, creating optimal conditions for achieving a return on investment within only a few years.

For the special applications where high-precision automatic controls were required, for quality control density measurement, and also for filling processes, the improved accuracy available with the digital communications creates major advantages over traditional 4-20mA technology.