A prominent design feature of ZS Series blowers (photo) is their application of rotary screw compression technology. The rotary screw concept helps the blower to operate at efficiencies 35–40% higher than traditional tri-lobe blowers at a compression ratio equal to one. ZS products are positive-displacement, rotary-screw compressors with an integrated gearbox that drives intermeshing compression rotors, reducing energy losses compared to a belt-driven machine. The intake air is compressed between the rotors and their housing. Three sizes of the blowers, from 5 to 100 hp, are available. Primary uses for the ZS blowers are for aeration of wastewater at water treatment plants, moving grain or powders off railcars, and for cooling extruded plastic in non-woven textile plants. — AtlasCopco Compressors, Rock Hill, S.C.