Low pressure compressed air is widely used for applications such as waste water aeration at treatment plants; dilute phase pneumatic conveying of dry powders and flue-gas desulphurisation of emission stacks.

“The blower market for small volume flows has been largely dominated by blower technology such as twin-lobe and Roots-type (typically used for early turbochargers in vehicles) which has not seen any major technical improvements over the past 50 years,” according to Pieter van Wyk, Atlas Copco Business Line Manager, Oil-Free Air, Atlas Copco Compressor Technique.

Recognising a market need, Atlas Copco developed an air blower solution based on its oil-free screw technology which uses internal compression instead of external compression, a technology which Van Wyk says is far superior to any other traditional blower technology. “This development enables us to offer the market an alternative low-pressure blower which runs at a similar duty to traditional lobe-technology units, but includes all of the features and benefits associated with modern screw compressors.”

Lower energy costs

The ZS range integrates the proven benefits of screw technology and will cut energy costs by an average of 30% when compared twin-lobe and Root-type blowers. Although the ZS blower does not represent the lowest capital cost solution on the market, these significant energy cost savings associated with the efficiency of a screw compressor lowers the lifecycle costs substantially.

Van Wyk points out that the energy savings alone make up for the initial purchase cost and will realise quick return on investment. “Over a five year period, 80% of the total costs of a 160kW blower, will be down to energy, while the remaining 20% will be equally split between the initial capital cost and the ongoing maintenance costs.”

“Screw compressors are not generally associated with the most efficient technology, but when it comes to the1 000 – 8 000 cubic centimetre per hour flow range, our screw technology without any doubt offers the best efficiency,” continues Van Wyk. “The ZS+ oil-free Variable Speed Drive (VSD) (22-355 kW, 30-475 hp) air blower range takes the two key prerequisites of reliability and energy efficiency to another level.”

The ZS+ VSD is supplied as a state-of-the-art, ready-to-run package with completely integrated VSD convertor and proven Elektronikon controller. “Our premium solution also comes with its own on-board PLC to precisely control the unit’s volumetric flow and discharge pressure. It is also fully compatible, via Modbus or Profibus, to a company’s SCADA system in a plant room, enabling a customer to very quickly get a complete picture of what his compressors are doing.”

100% oil-free and made to last

The 100% oil-free air delivery of the ZS blower is absolutely essential in many applications where end-product contamination must be avoided at all cost. In an oil injected compressor, the oil removes some of the heat when it is separated from the compressed air. But because the blowers run oil free, they run hot so they are fitted with an additional water-cooled jacket around the housing to extract heat from the air.

ZS blowers are manufactured to very high quality standards and are made to last. Screw technology has a much longer trouble-free running life. All ZS blowers are guaranteed for five years, but Van Wyk notes that the average lifespan is between seven and nine years. “As only bearings and seals will wear, only preventative maintenance is needed over an approximate five year period,” reveals Van Wyk.

Excellent component accessibility further enhances maintenance and extends service intervals in the ZS blower range. “And in the event that a seal does go, the design prevents any oil from mixing with the air. The oil is trapped in a redundant chamber and vented to the atmosphere to prevent contamination via the screws. A Roots-type blower won’t last much more than a quarter of that time; the lobes on the Roots blowers are usually treated as consumables. They can be refurbished but they are usually replaced like bearings or filters.”