The first four-stage centrifugal air compressor has been introduced for PET blow molding. The Centac 750 from Ingersoll-Rand Co., Air Solutions, Davidson, N.C., is claimed to offer significant benefits in terms of low maintenance and extended life cycle. The Centac 750 has only four moving parts—a bull gear and three rotating impeller assemblies—and does not need an annual overhaul, unlike standard three-stage reciprocating compressors, which have many mechanical parts like pistons and running gears. The Centac 750 runs on a “non-contact compression” system. Air is compressed by converting velocity imparted by the impeller to pressure without contact between mechanical components. The compressor also delivers twice the air flow for the same amount of floor space as a reciprocating system. Ingersoll-Rand has sold several systems to leading U.S. bottle manufacturers.