BCAS 2018

Technology Guide 36 www.bcas.org.uk Reciprocating compressors – NOT the dinosaurs you thought! Think of small piston compressors and so often the image of a tired noisy relic clattering away in a high-street tyre bay used to come to mind. Nothing could be further away from this reality than the contribution today’s modern reciprocating compressor technology is making to industrial productivity. BCAS reports. T he latest advanced piston technology is designed to meet exact application requirements; whether it is within a large industrial plant, a small workshop, or the controlled environment of a clean technology lab. That versatility includes customised piston solutions for industries with specific OEM demands as diverse as transport air suspension, marine propulsion and snow making equipment. The small-to-medium piston compressors range from 0.55 to 15 kW and are available as either oil-lubricated or oil-free machines. They can be supplied on a standard base or as trolley or receiver mounted units. If required, they can also be provided as part of a complete compressed air station including a refrigerant air dryer plus pre- wired starting and regulation equipment. Oil-lubricated piston compressors Compact, single-stage, oil-lubricated, reciprocating compressors in the 10-bar 1.5 to 15kW range are best suited for applications with limited space requirements. In these designs a lightweight compressor block, directly coupled to the motor, provides excellent cooling characteristics and smooth integration in small spaces. Filtered air enters both cylinders through the inlet valve. The piston is driven forward through the connecting rod attached to a balanced crankshaft. Air compressed in the cylinders leaves through the outlet valve when the pressure reaches 10 bar. Higher pressure, two-stage units allow filtered air to enter only one cylinder. This low-pressure cylinder feeds a second, high- pressure cylinder that can operate at a maximum pressure of 15, 20 or 30 bar and provide corresponding capacities ranging from 2.1 to 18l/s. The specific needs of the artisan workshop, garage operator or commercial vehicle service bay are catered for with 8, 10 and 12 bar receiver-mounted, simple-to- use, low weight, easy-to-move machines that offer capacities ranging from1.7 to 12.9 l/s. At the heavyweight end of the scale, there are two-stage cast iron piston compressors with high volumetric efficiency for demanding industrial, automotive, and commercial applications requiring working pressures of between 8 to 12 bar. Oil-free piston compressors Oil-injected compression, even filtered, cannot guarantee that all oil vapours, aerosols, and other contaminants are removed from the air. The oil-free air technology employing sealed for life bearings and PTFE or carbon piston rings that remove any risk of contamination and meets the certified ISO 8573-1 Class 0 standard in air quality. Oil free,10 bar piston compressors fall into three principal categories: Single- stage, one-cylinder units for applications between 1.0 and 2.5l/s; single and two- stage compressors designed for continuous duty, delivering quality air between 3 and 17l/s; as well as electronically controlled single-stage, fully silenced models. At the heavy end of the range are 25 to 40 bar, 37 to 275 kW, 3 and 4-stage high pressure oil-free compressors, which are the preferred choice for critical processes such as PET bottle blowing, aeronautic industry test benches and food and beverage production. Reciprocal compressors