Flexible automation of hygienic processes

?In the food and beverage sector Analysing each individual part of a plant or installation will show if an application requires centralised control interfacing to non-intelligent nodes, or -?if control has to be decentralised - using a fieldbus system and intelligent valves and actuators.

For larger and more complex plants, though, the answer is usually not a single automation concept for the entire process of production, as each different part and section of the process, down to machine level, has its own specific requirements.

This points to the value of employing different automation concepts in parallel: centralised and decentralised automation, as well as locally installed, pneumatic valve-block automation systems.

The centralised control concept is the most traditional of these, and although somewhat displaced in many larger plants, centralised cabinets with automation systems for electrical and pneumatic signals have certainly not lost their importance.

Air consumption

Centralised systems, however, require extended control air lines that increase air consumption and have a negative effect on the switching times of the valves.

There are also concerns as regards hygiene. Every additional control air and feedback line within the production plant is a potential source of contamination and risk, and must therefore be monitored, serviced and cleaned regularly - a costly undertaking.

Decentralised automation is a more recent concept. It employs intelligent pneumatic process and control valves for all production processes, and utility circuits such as steam, cleaning and temperature control media. The net result is greater flexibility for project planning, installation and maintenance, as well as transparency for process control.

The use of a decentralised automation system, employing intelligent process valves, also eliminates the problems of centralised systems, because automation functions - pilot valves, electrical and optical position feedback and fieldbus interfaces - are integrated directly as part of the process valves.

This approach minimises the number of cables and compressed air lines. In addition, by integrating an AS interface as a fieldbus interface, the intelligent valve capabilities can be fully utilised.

All that is required for the power supply, feedback and communications is a two-wire connection, interfacing the PLC with up to 62 valves.
Each process valve is connected directly to the main compressed air supply line in the field, significantly reducing the number and length of tube and cable connections, as well as the number of required control cabinets.

Flexible, pneumatic valve units and compact automation systems bridge the gap between centralised and decentralised automation concepts.

Using stainless steel attachment plates, these units are wall-mounted directly inside small, hygienically designed cabinets that can be installed close to a process. These small, pre-configured and standardised units eliminate the long runs to valves and field devices, and are relatively easy to keep clean.

This concept can involve the use of adapters that complement the valve terminals and automation systems used in different areas of the operation, while meeting the standards demanded by hygienic applications.

Pneumatic connections, the fieldbus interface and the I/O modules can be mounted directly on the control cabinet base or side. This facility allows for an altogether smaller design of control cabinets.

Additional components such as pipes, cables or control cabinet connections are eliminated, due to direct mounting, further reducing the time needed for installation and commissioning.

These designs can make the engineering and commissioning of automation systems easier and less costly. In addition, end-users benefit from plant standardisation, with easier plant monitoring and diagnosis, as well as reduced costs for maintenance and ownership of these facilities.