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Intelligent networked valves decentralise control of beverage plant operations

11 April 2011

Used in conjunction with Burkert’s intelligent valves, a decentralised AS-i fieldbus system not only greatly simplifies the field installation, but also enhances the efficiency, safety and hygiene of food and beverage plant operations

Food and beverage companies working with additives, such as concentrates and flavours, have to ensure that their production processes are not only safe and hygienic but also efficient; important considerations that have led to a growth in demand for sophisticated process automation. However, the conventional approach, which typically centralises the automation of process valves, for example, has its limitations and operators are now moving towards more viable and efficient control platforms comprising intelligent process valves with integrated automation functions.

Centralised control architectures require cabinets to house valve terminals and I/O systems with remotely located valves connected back to these cabinets via numerous air lines and discretely wired feedback loops. Apart from the high cost of such installations, they are not entirely without problems as regards to hygiene.

A recently upgraded production plant for fruit juice concentrate, and other basic ingredients for beverages and food products, underlines the benefits of a more distributed control strategy. The new facility includes intelligent process valves from fluid controls specialist, Burkert, which are used by the drink manufacturer across its entire production facility in a decentralised control system with communications via an AS-interface (AS-i) fieldbus.

Control of product flow, the auxiliary circuits for water, steam, sterile air and cleaning fluids is all decentralised, thanks to the use of intelligent valves. As a result, the central process control system overhead is substantially reduced, being limited to supervisory control and status monitoring. The key to this arrangement is the AS-i fieldbus, which enables the advantages of remotely located intelligent devices to be utilised to the full. All that is required for power supply, feedback and communication is a two-wire cable that connects the central PLC with up to 62 valves. Each process valve is individually connected to the main field compressed air supply to keep the lines as short as possible.

The status of individual valves can be checked onsite, even from a distance, by making use of the bright, coloured LED status indicators. And should manual intervention be necessary, the process valves can be operated from their ‘Element’ control heads, which contain all the automation functions and fieldbus interfaces.

Once the reliability and efficiency of this arrangement was proven, the decision was taken to roll out decentralised control to other sections of the plant. Today, the raw product intake unit, the homogenisation and pasteurisation station and the raw product distribution system are equipped with Burkert’s intelligent process valves. Angle seat and diaphragm valves control the flow of cleaning media, including acids, alkalis and water, as well as steam and sterile air supply. As the operating and maintenance staff were already familiar with As-i and its connection system, commissioning the new plant sections was relatively straightforward.

Networked process valves - hygienic, compact and safe
The intelligent valves units described in the main article comprise a valve actuator and control head. They are manufactured according to the EHEDG guidelines for hygienic design and easy cleaning, feature the necessary high IP protection and the use of detergent-proof materials in their construction. These measures ensure that the valves operate reliably when subjected to long-term use under conditions of high humidity and frequent cleaning with aggressive chemicals.

A further key feature of Burkert intelligent valves is the provision of an integrated control air inlet to the actuator chambers, which ensures that the spring chamber of the pneumatic driver is supplied only with clean control air. Moisture, dust and contaminants in the ambient air cannot enter the actuator units and this, in turn, prevents ingress of cleaning solutions, which might otherwise contaminate the piston seals and corrode the drive springs.

This design also eliminates the risk of moisture from the spring chamber entering the feedback module or the control head along the spindle extension. this significantly prolongs the service life of the driver, and is a positive benefit to process hygiene, as bacterial colonisation and mould formation are prevented. Thus there is no risk of spores produced in the spring chamber being ejected into the ambient air at each switching process, which is a common problem with conventional valves.

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