Moves to decentralisation

There is now a GROWING move towards the adoption of decentralised automation systems, especially with more practical solutions now being developed to integrate automation functions into the pneumatic actuators of process valves.

Early adopters include food / beverage producers and companies in the pharmaceutical and cosmetics sectors that use a high degree of automation in their production and systems in order to meet strict hygiene and safety requirements.

Both the statutory requirements of Hazard Analysis and Critical Control Points (HACCP) for food processing and Good Manufacturing Practice (GMP) for Food and Drug Administration-compliant processes in the pharmaceutical industry set the most stringent standards as regards cleanliness, safety and product quality. Processes must also be constantly monitored and documented.

The increasingly competitive global environment, meanwhile, means companies need to make their production processes as efficient and cost effective as possible, driving demand for increased automation at the process level.

In the field of process valves, conventional automation systems – including control cabinets with valve terminals, input/output (I/O) systems and fieldbus connections – require extensive and costly tube connections and wiring.

The valves at field level are connected to the control unit through many extended pneumatic control lines and discrete feedback connections. In many cases, long control air lines increase the air consumption and have a negative effect on the switching times of the valves.

Moreover, apart from the high costs for the planning and installation of such solutions, there are concerns with regard to hygiene. According to HACCP, 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.

Intelligent process valves eliminate these problems, as automation functions – pilot valves, electrical and optical position feedback and fieldbus interfaces – are integrated directly into process valves’ actuators.

This approach, based on the principle of decentralised automation, minimises the number of cables and compressed air lines. With integrated intelligent valve systems, the process control system is only in charge of centralised control and status monitoring.

At field level, pneumatically operated process valves are used, which can be equipped with the required automation components: pilot valves with manual actuation, electrical feedback and optical status indication units, fieldbus interfaces, and even positioners and process controllers.
Plants based on such decentralised automation systems are, therefore, working with complete intelligent valve systems. By integrating an AS interface as a fieldbus interface, the entire range of advantages of the intelligent valve approach can be fully utilised.

All that is required for 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, reducing the number and length of tube and cable connections, as well as the number of required control cabinets, to a minimum.