A. General: 1. The blower shall be of the vertical rotary twisted ni-lobe positive displacement type blower. And must provide oil-free air, suitable for heavy-duty continuous industrial service. B. Impeller and Shaft: I. The Impellers shall be solid 3 lobe helical design to reduce pulsations and noise, with integral shafting, produced from close grain ductile iron. 2. Impellers shall be machined on all exterior surfaces to a precise contour for operating at close clearances and high efficiency operation. 3. Impellers shall be dynamically balanced to minimize vibration. 4. Blowers with impellers and shafts that are not of the one-piece integral design will not be accepted. Straight, two lobe or straight three lobe impellers are not acceptable. 5. Impeller housing shall be strongly ribbed one-piece design to prevent case distortion when operating at rated pressures. The housing shall be of high strength cast iron and precision machined for close clearance operation. 6. End plates shall be high strength cast iron with precision machined bearing fits to assure exact positioning of impellers in the main body housing. 7. Timing gears shall be helical design and machined from high strength alloy steel for precision timing, quiet operation and long life. C. Bearings and Seals: I. Bearings shall be heavy-duty spherical roller bearings for exact positioning of the impellers, to control thrust and to provide increased overhung load capacity. Bearings must be sized for a minimum BIO life of 50K hours. 2. Air seals of controlled flow design shall be piston ring type seals precision fitted to each impeller shaft to minimize air leakage and maximize efficiency. 3. Oil seals of piston ring and oil flinger design, shall be provided on each internal impeller shaft to prevent leakage from the oil reservoirs. 4. The drive seal shall be a high temperature elastomer lip type seal...
