Engineers must consider pros and cons of valve network alternatives 12 January 2015

Bürkert Fluid Control Systems is advising engineers in food processing plant to tread carefully if they want to take advantage of modern process valve controls to improve feedback loops, maintenance data, and plant visualisation, management and reporting.

The company points out that automated valves, depending on their size and design, can either be piloted, using compressed air for automatic actuation, or they can be solenoid actuated, generally under PLC control.

If an air supply is available, piloting the valves may be the right option and there are now innovative solutions to connect large numbers of pneumatic control air lines to a control valve manifold in a hygienic environment.

This centralised system "can provide an ideal solution for smaller applications or those with reduced automation requirements," says the firm.

However, as the scale of production increases so does the complexity and quantity of control wiring and compressed air lines, it advises – all of which require space, time and skill to be installed correctly.

The alternative is intelligent control valves that only require a common supply of compressed air and a fieldbus (industrial digital communications network) connection.

"When connecting larger numbers of process valves, which are often required in high densities for continuous process applications – typically supplying ingredients or fluids for CIP processes – a distributed control approach may be more suitable," says the company.

It makes the point that, 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 network.

Separate local enclosures, rack mounted PLCs, I/O, cabling, power supplies, HMIs etc can also be replaced with a single control unit mounted either on or near to the process valve.

"Deciding which approach is the most suitable requires the decision makers to have ... an in-depth knowledge of the process, as well as competent advice on the advantages and disadvantages of each design," warns Bürkert.

Bürkert Fluid Control Systems offers the Element range of intelligent control valves, designed for hygienic applications.

The company also provides smaller localised controllers, such as the multiCELL device, which can be used to monitor and process several valves and sensors, communicating up to a PLC.

Brian Tinham

Related Companies
Burkert Contromatic Ltd

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