Intelligent valves for hygienic processes: How integrated valve systems eliminate the disadvantages of conventional automation concepts

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1 Intelligent valves for hygienic processes: How integrated valve systems eliminate the disadvantages of conventional automation concepts White Paper June 2009

2 Intelligent valves for hygienic processes: How integrated valve systems eliminate the disadvantages of conventional automation concepts Dipl.-Ing. Sebastian Kundel, Product Manager Process and control valves, Bürkert Fluid Control Systems With conventional centralised automation of process valves in production units for food, drinks and pharmaceutical products, it is often difficult to meet the necessary stringent hygiene and safety standards. Intelligent process valves with integrated automation functions offer an interesting alternative in this field and can help reduce planning, installation and maintenance costs. In the production of food, drinks, medicines and cosmetics, excellent hygiene in the process and around the plant play a key role. The statutory requirements of HACCP (Hazard Analysis and Critical Control Points) for food processing and GMP (Good Manufacturing Practise) for FDA-compliant processes in the pharmaceutical industry set most stringent standards as regards cleanliness, safety and product quality. In addition, all processes must be constantly monitored and documented. In an increasingly competitive global environment, companies are at the same time forced to make their production processes as efficient and cost-effective as possible. As a consequence, there is an ever increasing demand for automation at process level. In the field of process valves, conventional automation solutions including control cabinets with valve terminals, I/O systems and field bus connections 2

3 require extensive and costly hose connections and wiring. With this technology, the valves at field level are connected to the control unit in the control cabinet through a large number of long control air lines and discrete feedback connections. Apart from the high costs for the planning and installation of such Automation of process valves: centralised vs. decentralised solutions, there are also concerns as regards hygiene. According to HACCP, every additional control air and feedback line within the production plant is a potential source of contamination and other risks and must therefore be monitored, serviced and cleaned regularly, which is a costly undertaking. The use of innovative intelligent process valves does away with these problems. As the automation functions such as pilot valves, electrical and optical position feedback and field bus interfaces are integrated directly into the actuators of the process valves. This approach based on the principle of decentralised automation minimises the number of wires and hose lines. In addition, the concept is extremely flexible and provides a number of other advantages, which are explained in more detail below. Central automation through control cabinets Pneumatically operated valves are currently used at numerous points within production plants in the food and drinks industry, dairy factories and the pharmaceutical and cosmetics industries. These valves are normally automated through conventional centralised control cabinet systems, including a valve terminal, an I/O system and interfaces for communication via field bus. Each individual pneumatically operated fitting inside the production plant must thereby be connected to the control cabinet through a control air line as well as a discrete feedback line. The costs for the planning and installation of such solutions are very high, especially in more complex plants. In many cases, long 3

4 control air lines increase the air consumption and have a negative effect on the switching times of the valves. A large number of hoses and lines inside the plant are also problematic from a hygiene point of view. Another disadvantage of such automation systems is the fact that the pilot valve operating level is at a distance from the fitting, making it more difficult to commission, maintain and extend the plant. The alternative: integrated intelligent valve systems A viable alternative to the conventional use of central control cabinets is the integration of the required automation functions in the valves themselves. In this case, the process control system is only in charge of control and status monitoring. At field level, pneumatically operated process valves are used, which can be equipped with all required automation components such as a pilot valve with manual actuation, electrical feedback units and optical status indication, field bus 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 field bus interface, the entire range of advantages of this approach can be fully utilised. All that is required for power supply, feedback and communication is a two-wire line connecting the PLC Complicated wiring in central control cabinet with up to 62 valves. Each process valve is connected directly to the main compressed air supply line in the field, whereby these connections are kept as short as possible. This reduces the number and length of hose and wire connections as well as the number of required control cabinets to a minimum. The valve systems themselves are designed according to the EHEDG guidelines for hygienic design and easy cleaning. As a result, they feature the high IP protection required by the actual application and are made exclusively of detergent-proof materials. The IP protection is therefore not affected by prolonged use in environments with high air humidity or by frequent cleaning with aggressive chemicals. In comparison to conventional automation solutions, this design marks a real progress as regards improved hygiene. In addition to better hygiene, there are other advantages to reduced electrical wiring and fewer control air lines. Even prior to commissioning, users benefit from the decentralised concept as it simplifies project planning and allows for more flexible solutions thanks to easier integration of the process and automation levels. This also applies to the subsequent installation, commissioning and maintenance. A clearly visible status indicator integrated into the fitting allows the operator to monitor processes and the operating status of valves not only at a central point at control level but also directly at the fitting. 4

5 Design of the valve systems With conventional automation by means of control cabinet solutions, the drivers used in the plant must already be equipped with a device for electrical feedback. Innovative valve systems go a few steps further and cater for the integration of pilot valves with manual actuation, optical position indicators and other automation functions inside compact, hygienic and easy to clean stainless steel housings. Depending on the application, users can choose between different equipment and configuration options. The wide range of available options includes mechanical limit switches, inductive proximity switches and NAMUR initiators as well as mechanical position indicators and self-teaching limit position feedback modules with inductive linear displacement transducers. At the lower end, decentralised automation based on intelligent valve systems start with a process valve with integrated electrical feedback, simple optical feedback and integrated pilot valve. Such systems already do away with valve terminals in the control cabinets. Moving up one step in the modular valve program, users can avail of more of the already described advantages of decentralised automation. In addition to the electrical feedback and the pilot valve, these solutions include large-size highperformance colour LEDs for improved optical feedback, facilitating process monitoring at field level, and an optional AS interface serving as a field bus interface, whereby all these features are integrated into the valve system. These systems also Control valve for hygienic processes come with an analogue displacement transducer replacing two conventional initiators or micro switches. The limit position is thus adjusted reliably and automatically through a teach 5

6 function rather than manually. The process valves require only minimum space and can therefore be easily installed in the pipeline system of the plant. As they are made in highly resistant materials, they are easy to clean and provide maximum availability thanks to excellent functional safety. This high level of functional safety is mainly due to the integrated control air supply to the driver chambers, which ensures that the spring chamber of the pneumatic driver is also supplied exclusively with clean control air. Moisture, dust and contaminants in the ambient air can thus not enter the drive units. This in turn effectively prevents contamination of the piston seals and corrosion of the drive springs caused by cleaning solutions entering the housing. There is also no risk of moisture entering the feedback module or the control head along the spindle extension. While this considerably prolongs the service life of the driver, this design also has a positive effect on the hygiene of the process. As product cannot enter the driver, both the spreading of germs and contamination of the driver by mould are effectively prevented. There is thus no risk of fungal spores produced in the spring chamber being ejected into the ambient air at each switching process, which is a common problem with conventional valves. The actuator housing is flushed with control air at each switching process as some control air is fed through at the pilot valve. This means that, upon switching, a small volume of control air is fed into the housing. This process takes less than 10 milliseconds and ensures that a slight overpressure is built up in the housing, further improving its IP protection and preventing the penetration of humid air, for example in the event of changes in temperature or rinsing with cold water. The integrated pressure-relief valve ensures that the pressure in the housing is automatically reduced, if, after several switching processes, it reaches a value of approx. 0.5 bar. Through this combination of control air inlet and release, a constant overpressure is maintained inside the housing, while a certain volume of air is regularly replaced. This ensures that no condensate can build up inside the housing. Systems of the above design can be extended to complete control valve systems by combining them with digital electro-pneumatic positioners and process controllers. The control valves thereby meet the same stringent hygiene standards as the process valves. Ventilation of the spring chamber and flushing of the control housing are again included as standard. SUMMARY With the development of practical solutions that integrate automation functions into pneumatic actuators of process valves, the advantages of decentralised automation have become a real alternative to control cabinet systems for many users. Food and drink producers as well as companies in the pharmaceutical and cosmetics sector are now in a position to reconcile the commercial necessity of a high degree of automation of their production with the requirements of hygiene and safety. Thanks to their modular structure, sys- 6

7 tems based on intelligent process valves can be adapted to suit many situations and applications, whereby such optimised solutions are always based on high-quality, tried and tested components with a long service life. References DIN ISO Sicherheit von Maschinen Hygieneanforderungen an die Gestaltung von Maschinen (Safety of machinery - Hygiene requirements for the design of machinery) DIN EN :2005 Nahrungsmittelmaschinen Allgemeine Gestaltungsleitsätze Teil 2: Hygieneanforderungen (Food processing machinery Basic concepts - part 2: Hygiene requirements) Machinery Directive (98/37/EC) Teil für die Nahrungsmittelmaschinen, Anhang 1 (Food processing machinery - Annex 1) EHEDG, document 13 Guideline Hygienic Design von Apparaten für offene Prozesse (Hygienic design of equipment for open processing) EHEDG, document 8 Hygienic design equipment criteria 7

8 Kontakt Can we help you to optimise your hygienic processes with intelligent valves or do you have further questions? Just contact Bürkert Fluid Control Systems Dipl.-Ing. Sebastian Kundel Product management proccess and control valves Am Flugplatz Egelsbach Germany Tel: Website: 8