The general trends in the automation of food processing have been heading towards more precise control and more information being gathered at device level. It is important for process engineers to appreciate which control structure would be most appropriate for their particular application.
Process control infrastructure has seen many advances in terms of design, efficiency and reliability, where better control has also paved the way for continuous processes, reduced waste, improved hygiene and greater efficiency. In addition, the amount of information available from local devices improves the feedback for control loops and provides better information for increasingly sophisticated plant visualisation, management and reporting software.
However, integrating this technology into an existing application can be a daunting prospect and one that may require expert help.
Automated process valves, depending on their size and design can either be ‘piloted’, i.e. a pressurised air supply is used to actuate the valve, or an external actuator, such as a solenoid, is used. These items are usually connected to a PLC or other electronic controller, one which uses a software program or routine in order to keep the sequence and operation of the process valves in synchronisation with the desired pressure, flow and mixing required of the fluid being controlled.
If a compressed air supply is available, then piloting the valves may be the right option and there are some innovative products on the market to connect large numbers of pneumatic control air lines to a control valve manifold block in a hygienic environment. This centralised system can prove suitable for smaller applications or those with reduced automation requirements.
However, as the scale of production increases so does the complexity and quantity of control wiring and compressed air lines, all of which require space, time and skill to be installed correctly. The alternative is the use of intelligent control valves that only require a common supply of compressed air and a fieldbus connection.
When connecting larger numbers of process valves, which are often required in high densities for continuous process applications (typically supplying fluids such as ingredients or for CIP processes in food processing applications), then a distributed control approach may be more suitable. Using fieldbus protocols such as ASi, Profibus and DeviceNet allows individual valves to be connected using just one or two cables to link back to a local controller, or up a level to a factory-wide bus network.
Onboard control loops
The relative costs of a separate local enclosure, rack mounted plc, I/O, cabling, power supply, HMI etc. can also effectively be replaced with just one small control unit that can be mounted either on or very near to the process valve. This is made possible by using smaller proprietary controls and / or intelligent valves with their own onboard control loops and parameters.
Deciding on which approach is the most suitable requires the decision-makers to have all of the available information and this will usually require an in-depth knowledge of the process as well as competent advice on the advantages and disadvantages of each design. Consideration about the ease of commissioning and maintenance as well as the availability of competent fieldbus engineers is also essential.
Bürkert Fluid Control Systems has been at the forefront of developing the technology required to make these significant steps in process control design possible. The ELEMENT range of intelligent control valves for example has been specifically designed for hygienic applications with many features that will benefit the food processing industry. The company also provides smaller localised controllers such as the multiCELL device which can be used to monitor and process feedback from several valves and sensors before communicating up to a PLC or wider factory automation platform.
These are all supported by a number of experienced designers and engineers, all on hand to provide expert advice in designing and installing a new system. Bürkert has products for all options, with no bias towards one or the other, just a commitment to delivering value and long-term reliability.
To learn more about intelligent control systems for food processors, please visit www.burkert.co.uk.