Compressed air is changing…

Published:  05 May, 2017

PWE reports from this year’s Hannover Fair where Gardner Denver has launched a new, water-cooled oil-free compressor from its CompAir brand – Ultima - offering up to 12% improved energy efficiency compared to a conventional two-stage machine with a 37% smaller footprint.

Launched as part of the company’s CompAir PureAir range, Ultima is available in models from 75 kW to 160 kW and is designed for best in class performance, for applications that demand the highest levels of air quality and purity.

Unlike standard oil-free compressors, which have a single motor and mechanical gearbox design to drive the low and high pressure air ends, Ultima uses the U-Drive concept - two, high-efficiency, permanent magnetic motors which replace the gearbox and single motor.

These variable-speed motors, powered by an inverter, can achieve speeds of up to 22,000 rpm and deliver efficiencies greater than IE4.

While conventional variable-speed machines are already well proven in numerous applications and deliver high energy efficiency, the two stages of compression are linked mechanically, meaning they need to speed up and slow down at the same time.

Ultima, however, is different. By removing the gearbox and single motor entirely and replacing with two U-Drives powered by two separate inverters, each airend stage is now driven directly and independently, for even greater performance. An intelligent digital gearbox design then monitors and adjust the speeds of each aired continuously, ensuring maximum efficiency and pressure ratios at all times.

In addition, the design of the compressor results in hugely reduced friction, resulting in an oil-free compressor with the highest levels of efficiency throughout its full turndown range.

Ulrich Thomes, senior technical engineer from Gardner Denver, who led the engineering team responsible for Ultima’s design said: “From the outset we had clear requirements for the specification of Ultima’s drive unit and found that no current-generation motor was able to deliver the efficiencies required. U-Drive is a true, next-generation motor and the result of three years’ development. We believe that this is one of the most advanced compressor drive technologies available to customers today and ideal for a pioneering product such as Ultima.”

Energy recovery

Around 94% of compressor energy is converted in to heat, which, unless it is captured, is vented in to the atmosphere as wasted energy. Ultima uses a bespoke, closed loop water cooling system to ensure that the maximum amount of energy can be recovered from the complete compressor package, taking heat directly from the major components, including the motors, inverters, airend jackets and the oil circuit.

This results in up to 12% better overall heat recovery than a standard two-stage oil-free compressor, for even greater levels of efficiency. Furthermore, Ultima also acts as a high-efficiency water heater, heating the cold water that enters the compressor, which can then be used for other applications.

Cooling and ventilation

For maximum efficiency, the air entering a compressor should be as cool and dense as possible, so Ultima is engineered to ensure that no warm air is vented in to the compressor room. Instead, this warm air is processed within the machine enclosure and, using a heat exchanger, the air is cooled and then recirculated via the base frame around the compressor. As a result, no heat is wasted, no dust or particulate matter enters the compressor and the inlet air stays cool.

This also helps to reduce installation time and expense significantly as there is no requirement for additional ducting.

With a noise level of only 69 dB(A), Ultima is also extremely quiet, meaning that compressor can be installed easily at the point of use, rather than housed in a separate compressor room, eliminating the need to install and maintain pipework, to maximise efficiency further.

Energy optimised

PWE was told by the manufacturer that Ultima’s engineering team have considered energy consumption at every stage of the design, to create a compressor which, in idle mode, uses 45% less energy than a conventional 2 stage compressor. This can require as little as 8kW of electricity to power a 160kW compressor when idling.

Elsewhere, an intelligent control concept has eliminated the need for an air unloader valve, effectively eliminating the pressure drop that occurs as a result of a compressor controlling the volume of air entering the aired. This also improves maintenance efficiency, as it is one less component to service and replace routinely.

It uses approximately 20% less parts than a standard oil-free compressor, helping to reduce maintenance requirements and compressor reliability.

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