Pneumatic systems: Air preparation matters
11 August 2017
To achieve process reliability, machine availability and to boost the service life of pneumatic systems, it is important to optimise air preparation. Here, Kai Feller, product manager process automation, at Festo offers a few tips
Particles, water and oils in compressed air can lead to mechanical friction, corrosion or clogging. A correctly specified and sized air preparation set is essential to the smooth running of a pneumatic system and, by following simple preventative steps, it is possible to significantly improve service life, energy efficiency and system availability, ensuring a machine functions to its full capacity.
Top tips include:
• Check the flow rates of fine filters: Flow rates might meet overall application requirements, but this can be misleading. Grid sizes on fine and micro filter units slow down air flow considerably – often leading to running the system at higher pressure to compensate, increasing energy usage. The solution is to use standard connecting plates, allowing fine and micro filters to be larger in size than the rest of the air prep set, enabling optimum flow rates throughout the system.
• Avoid water in the system: Liquids such as water in the system lead to corrosion, generating rust particles that can cause mechanical damage or block small flow cross sections. Installing condensate drains within filter units helps prevent carry-over of extracted liquid into the downstream air flow. These range in cost and complexity from fully automatic drains that automatically vent as the condensate builds up, to fully manual drains that rely upon regular maintenance inspections.
• Use easy-to-read pressure gauges: Gauges with pre-set operating zones enable fast setting and monitoring of operating pressure without relying upon skilled technicians. With only a quick glance, operators can easily check all is well. The optimum operating pressure can be easily displayed within a green zone. Pressure regulators are adjusted to set the needle within this range.
• Reduce air pressure to the machine: Minimise air consumption and energy use as far as possible. Often, machine pressure is determined by the requirements of only one or two components. By introducing pressure zones – either with a regulator on those components or by installing a pressure booster feeding a local reservoir – the overall air pressure of the machine can be reduced. Additional hardware costs are quickly recovered as a lower air pressure setting can be maintained for the whole machine, reducing air consumption and energy costs.
• Correctly size air preparation units: Pay attention to flow rates quoted for air preparation units: oversized filter bowls will not function optimally. Relying upon inducing a swirl action on the air flow, they only function at their best when the velocity of the air flow meets the design criteria. Don’t undersize – but don’t oversize either – it wastes money and impairs performance.
• Monitor or inspect filter elements: Monitor filter elements regularly, changing them before they lose efficiency and effectiveness. Clogged filter elements fail to remove particulates and can reduce flow rate by up to 50%. Contamination gauges or flow meters should be fitted, particularly for fine and micro filter elements. Stocking and replacing filter elements is a low cost, simple maintenance task that can reap large dividends in filter performance and avoiding pressure drop.
Festo has developed a series of technical resources designed to help engineers optimise air preparation. Available at www.festo.co.uk/stars-airprep, engineers can view a series of short tutorial videos and download a white paper called: 'Compressed air preparation in pneumatics'Available at www.festo.co.uk/stars-airprep.