Pneumatics in the twenty first century
02 August 2012
One might be forgiven for thinking that pneumatics is ‘yesterday’s technology’, now rapidly giving way to modern electromechanical alternatives. Ian Morris would strongly disagree, as he focuses on some of the operational advantages that make pneumatics more compelling than ever as an effective means of producing mechanical motion.
Pneumatics is a fluid power technology that has been around for many years, serving a variety of sectors, including mining, offshore, marine, rail, road transport, construction and even dentistry. Application examples abound, with equipment providing a flexible, reliable and safe means of producing mechanical motion, whether it be on the factory floor or in the dentist’s chair.
Of course, the biggest marketplace for pneumatic actuation is ‘general industry’, comprising a very large and diverse customer base for lightweight, low-cost pneumatic actuators. This level of user diversity comes in useful at times of economic hardship; pneumatics isn’t quite as badly affected as other technology sectors that may depend on a narrower customer base. The market for pneumatics, I would suggest, is less susceptible to the vagaries of economic cycles, thanks to this broad horizontal reach.
So, what are the advantages to the user of selecting pneumatics as a preferred mode of power transfer? Take maintenance, for example. If we compare a linear drive unit based on a pneumatic cylinder with an electric rack and pinion drive, we can see that with the latter, there are many more wearable parts, whereas the lack of complexity of the pneumatic actuator presents a very different maintenance task. The pneumatics option is also cost-effective, thanks to simplicity of design and installation. Flexible nylon tube and fast-fit connectors has vastly improved the assembly process, and nowadays installation is often just a simple case of ‘plug and play’.
Pneumatics is an intrinsically safe technology and it has long been the method of choice for achieving actuation in hazardous areas. Compliance with the ATEX Directive - in terms of what equipment the Directive deems acceptable in environments containing a potentially explosive atmosphere - is not a burdensome issue, as far as pneumatic systems are concerned. But a word of caution here – as there is now a tendency to combine electronic components with pneumatic actuators for control and monitoring purposes, any such combination must be checked for compliance before it is installed and put to use.
While on the subject of electronic integration, it is worthy of note that the increased use of electronics with pneumatic equipment - commonly referred to as electro-pneumatics – has achieved greater levels of accuracy, control and monitoring. Modern industrial automation relies to a great extent on industrial networking protocols such as CANbus, and the pneumatics industry has responded by incorporating fieldbus connectivity within their equipment. Indeed, this fieldbus connectivity now extends to pneumatic valves, ensuring easy integration into a control system. And as far as monitoring goes, these systems also afford the user the benefits associated with remote diagnostics.
Coupling pneumatics with electronics makes a lot of sense, whether in terms of programming flexibility, speed of operation, better control and monitoring, or even better user safety. This ‘hybrid’ approach adds considerable flexibility when it comes to system design. For example, rather than the trip switches that have hitherto provided simple on-off control, programmable logic controllers (PLCs) are now able to facilitate a more complex pattern of event control. One of the more impressive aspects of the PLC function is that if users want a piece of equipment to take a little longer to close or longer to open, they simply programme it electronically while the action is still performed by the pneumatic cylinder.
With pneumatics come significant energy benefits. Under static conditions a pneumatic system (or, indeed, fluid power systems in general) do not use any energy. For example, when users want to hold a pneumatic cylinder in a chosen position, they simply lock off the valves necessary to effect the task and the cylinder stays static.
Fit for purpose
It is true to say that in some manufacturing environments, the electrical alternative may be more suitable. When automating a food processing line, for example, electric actuators would likely be the better choice as they don’t produce any exhaust air. However, in other industrial environments that do not demand such levels of hygiene, pneumatics would arguably be more suitable because the equipment is generally more robust, simpler to operate and easier and more cost-effective to maintain.
Ian Morris is director of the British Fluid Power Association
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