The argument for pneumatics in process industries
2nd Quarter 2011, Pneumatic systems & components
Pneumatic automation technology is perfect for many applications in process industries as it is robust, inexpensive and reliable. Compressed air can be easily transported, stored and is simple to control. These advantages enable pneumatics process control systems to perform fail to safe and speed control functions simply and easily.
With an average service life of more than 1 million cycles, pneumatic actuators will outlive most process valves. Even in harsh environments, generally found in process industries, with large temperature fluctuations, high levels of humidity, and abrasive substances. Pneumatic equipment is unaffected by temperatures between -5°C and +80°C, while special low-temperature variants can even operate down to -40°C and high-temperature variants up to +120°C. All stainless-steel component variants are extremely resistant to corrosion.
Festo pneumatic actuators and switch boxes are used to control butterfly valves on a water treatment plant sand filter
Pneumatics is an uncomplicated technology which is easy to install, and can be set up quickly during commissioning, saving time and money. Pneumatic drives have proved to be vibration-resistant and long-lasting. In contrast to electric drives, they consist of only a few components and are thus less susceptible to breakdowns. What is more, pneumatic drives are able to withstand continuous load and require no maintenance throughout their working life. There is no need for oil changes or lubrication top-ups.
Down with costs
Thanks to the lower costs, it is even worthwhile to automate manually operated valves retrospectively. Particularly in comparison with electric drive technology, the broad-based use of decentralised automation concepts with valve terminals results in considerable cost advantages. Savings of more than 50% are possible in some cases.
As pneumatic drives are overload-tolerant and allow higher drive forces to be achieved simply by increasing the supply pressure, it is often possible to use smaller drives with lower weight than would be possible with electric drives. Provided that the tubing connections are leak-free and components are correctly dimensioned, the result is energy-efficient solutions. Pneumatic systems from Festo can deliver high forces of up to 47 500 N and torques of up to 8500 Nm.
Emphasis on safety
Pneumatic drives have three emergency functions in the event of a power failure – open, close and stop. They are ideal for use in areas with a potentially explosive atmosphere, in particular when explosion-proof valves, such as NAMUR pilot solenoid valves with appropriate coils, are used and the valves or valve terminals are located outside the explosion-hazard zone. In these cases, the pneumatic drives in the explosion-hazard zone are supplied with compressed air via tubing, while the electrical control components can be installed in a non-hazardous zone. Pneumatic drives are ATEX-approved as standard up to zone 1.
Deposits or baked-on residues of foreign material can lead to considerably higher breakaway forces on pneumatic drives. This happens particularly when valves are not actuated regularly or for long periods. The overload tolerance of pneumatic drives is a great advantage, as with pneumatics it is not a problem to increase the operating pressure and thus obtain higher forces. They will not suffer damage even if overloaded to the point where they come to a standstill and have large reserves of force for cases where high breakaway torque is required.
Competent and relevant advice
Festo experts can help with the calculation of compressed air consumption and the optimum dimensioning of compressed air supply networks; they can also provide assistance during the tendering phase if required. Customers can obtain everything they need from a single source and with just one part number. This ensures a simple ordering process and means that projects can be completed more quickly.
For more information contact Joanne Dexter, Festo, +27 (0)11 971 5560, firstname.lastname@example.org, www.festo.co.za