RAS-J series Whispair blowers are heavy duty units for continous service featuring a proprietary design that reduces noise, pulsation, and horsepower levels over conventional blowers. An exclusive wrap-around plenum and Whispair jet elimininate rapid of air into the blower from the discharge area - a major problem with conventional blowers.

Design Features

CASING - The blower casing is of one piece close grained cast iron construction with seperate headplates. The casing is suitably ribbed to prevent distortion under the most severe operating conditions and incorporates the Roots Whispair feature for reduced pulsation, noise and horse-power levels.

IMPELLERS - The impellers are made from ductile iron with a tension strength of 60,000 PSI. They are statically and dynamically balanced by removing metal from the impeller body and operate without liquid seals or lubrication.

SHAFTS - The blower shafts are alloy steel forgings flange connected to the impeller body with high-tensile socket head capscrews. Labyrinth seals are machined into the shafts to minimize air leakage.

TIMING GEARS - The impellers are timed by a pair of accurately machined forged steel gears that operate in an oil bath. The wide-faced spur gears are manufactured to AGMA standards and are carburized and ground with a hardness of 58-60 Rc. On 1000J frame size units, the gears are secured to the shafts by a taper fit. Larger sizes use a taper locking device providing an easily adjustable and releasable mechanical shrink fit. No shaft-weakening keyways or locking pins are required.

BEARINGS - The impeller/shaft assemblies are supported at each end by double row squerical roller bearings designed for long life. The thrust end bearings are fixed to control the axial location of the impeller assembly in the unit. An inboard bearing is used on 1000J through 1400J frame size V-belt driven blowers to minimize drive shaft stresses.

LUBRICATION - The bearings and gears are splash oil lubricated. Gear end oil is metered through an orifice into a secondary sump under the gear and is fed into the bearings through specialy designed leaders. On 1000J frame sized units, the thrust end bearings are splash lubricated with an oil slinger inside a single splash lube cover. Larger sizes have individual oil resevoirs at each thrust end bearing and are arranged so that the rollers dip into the oil each time they roll to the bottom of the raceway. All oil resevoirs have visible oil level gauges.

TESTING - Each Roots rotary blower is given a complete mechanical run and one-point flow test at full speed and pressure to ensure mechanical integrity and verify performance. The units are operated at elevated pressure rise for a minimum of one hour after temepratures have stabilized. Flow, pressure and temperature readings are logged during the test and each blower must meet suitable vibration levels in three different planes before been certified as acceptable.

Performance Table

LOWER AIR PULSATION - Whispair blowers operate with up to 50% less pressure pulsation than conventional blowers due to the pressure equalizing effect of the Whispair jet design. In conventional blowers, as the impellar opens up to the outlet port, the higher pressure air in the discharge line rapidly expands into the lower pressure pocket formed by the impeller and the blower case. The resulting shockwave strikes the advancing surface of the impeller at sonic velocity. Four pressure pulses occur during each revolution transmitting shock loads to the gears and bearings.

LONGER BEARING LIFE - The pre-pressurization of the low pressure pocket through the Whispair jet smooths the pulsations and results in less shock being transmitted through the impellers to the bearings, resulting in approximately 20% longer bearinig life.

LOWER VIBRATION - The reduction in the magnitude of the pressure pulsation results in smoother operation.

LOWER NOISE - The pressure pulses, inherent in the rotary-lobe design, are also the major source of blower noise. The rapid backflow of air into the blower from the discharge line, four time per revolution, results in high noise levels in the conventional blower. The Whispair jet controls the backflow of air into the blower, reducing noise by approximately 5dBA.

HORSEPOWER - As the impeller passes the Whispair jet port, pressurized air channeled in the direction of rotation strikes the backside of the impeller. The air jet imparts energy to the impeller, aiding rotation and reducing the power required to drive the blower.