+65 6295 5282 ragu@rapengineers.com

“RAP Engineers is committed to providing quality products. We are proud to represent the Howden Roots line of blowers and compressors. We stock a large supply of Howden Positive Displacement Blowers and can customize a Howden (PD) Blower package to meet your needs.

Howden Roots manufactures a full line of rotary-lobe and centrifugal air and gas handling blowers as well as vacuum pumps. In 1854, Roots pioneered the rotary-lobe blower design and has extensive experience with a wide range of applications and industries.

A rotary positive blower, sometimes called a Positive Displacement, or PD blower, is a machine that “pushes” a relatively constant volume of the gas handled at the inlet through the discharge. It doesn’t internally compress the gas, so it isn’t considered a compressor. The amount of gas the machine handles is fixed by the configuration of the casing and rotating parts.”

Flow through a PD machine is relatively constant, regardless of pressure changes. This is different from a centrifugal compressor, which maintains a relatively constant pressure while the flow varies.

As the dual, figure-8 shaped impellers rotate, a fixed quantity of gas (or air) at the inlet is trapped between the impeller and the casing parts. With each revolution, four of these “pockets” of gas are trapped, then forced out the discharge against whatever pressure exists in the system.

When each of these pockets is expelled, a pulse is generated, which imposes a certain shock load on the blower and the downstream system. A ROOTS improvement on the basic PD design is the Whispair Blower. It lets the gas in the pocket pressurize slowly to discharge conditions via the internal “jets.” This significantly reduces pulsations and shock load on the equipment.

Key Features


  • Easy to install, with small footprint.
  • Acoustic enclosure is designed to provide up to 22 dBA free field attenuation.
  • Broad operating performance range provides a multitude of efficient and compact solutions.
  • Air flow from front to rear is designed for personnel safety and equipment reliability.
  • Access to air filter is convenient and designed to reduce pressure losses, improving reliability and blower efficiency and protecting your investment.



    • Small rotary performance
    • Flow rate: Up to 10,710 m3/hr (6,300 cfm)
    • Pressure: Up to 15 psig
    • Vacuum: Up to 28” Hg
    • Large rotary performance
    • Flow rate: Up to 120,000 m3/hr (70,000 cfm)
    • Pressure: Up to 35 psig
    • Vacuum: Up to 28” Hg and high vacuum
    • Custom design available for high static pressures


    Huge range of applications as the small lobe blowers are designed to work on trucks, while the bigger blowers operate in applications such as vacuum filtration and drying and materials handling.

    ROOTS™ Universal RAI ® Rotary Positive Blowers

    • Universal RAI blowers are heavy-duty rotary blowers designed with detachable rugged steel mounting feet that permit easy, in-field adaptability to vertical or horizontal installation requirements. Detachable steel mounting feet. The detachable mounting feet allow these units to be easily adapted to any of four drive shaft positions: right, left, bottom, or top.
    • The basic model consists of a cast iron casing, carburized and ground alloy steel spur timing gears secured to steel shafts with a taper mounting and locknut, and cast-iron involute impellers.
    • Oversized antifriction bearings are used, with a cylindrical roller bearing at the drive shaft to withstand V-belt pull. The Universal RAI® features splash oil lube on the gear end and grease lube on the drive end.
    • ROOTS’ exclusive “figure-eight” gearbox design improves oil distribution to maximize gear and bearing life.


    • Roots RAM series units are recognized by many as the most volumetrically efficient blowers in the industry.
    • Unless otherwise noted, RAM series equipment may operate under either vacuum or pressure application with no equipment modification, and can provide simultaneous vacuum and pressure for a system with a single unit.
    • RAM series units feature integral-shaft ductile iron impellers with involute profiles. Headplates and the rigid casing are cast grey iron, while the drive end and gear covers are aluminium.
    • Carburized and ground alloy steel spur timing gears are securely mounted on tapered shafts.
    • Detachable steel mounting feet permit adaptability to either vertical or horizontal installation requirements.
    • Piston-ring shaft seals reduce gas leakage through the headplates, while lip-type oil seals maintain lubrication in the bearings.
    • RAM units are splash lubricated on both sides with high volume oil reservoirs and convenient sight glasses.


    • Roots RCS series units are heavy-duty units with integral-shaft ductile iron impellers in an involute profile.
    • The headplates, gear cover, drive end cover and rigid, one-piece casing is grey iron.
    • Carburized and ground alloy steel spur timing gears are taper mounted on the shafts and secured with a locknut.
    • Cylindrical roller bearings combined with high volume oil reserves offer low maintenance and trouble-free operation.
    • Piston rings reduce air leakage through the headplate shaft openings, while lip-type oil seals maintain lubricant in the roller bearings.
    • All RCS series blowers are equipped with splash oil lubrication at both ends of the blower.

    RAS-J/RGS-J Forty PSL Blower

    • Extended flow range and efficiency with the advantage of the WHISPAIR plenum.
    • Up to 82% increase in pressure rise capacity.
    • Direct connect to 50Hz and 60Hz motors provides the largest flow range possible without gear-reducers.
    • Available with true pressure lubrication.
    • Mechanical seals are also available for your unique gas.

    Rotary Positive Blowers Easy Air Rotary

    • The EasyAir Rotary Factory Blower Package System is an improved design based upon the popular EASYAIR 8000 package.
    • The EasyAir Rotary system provides performance engineering in a standard package.
    • It is produced for vacuum or pressure applications, enabling simple, on-site installation.
    • Widely used in waste water treatment, pneumatic conveying & bulk handling needs, and process air needs applications

    RAM-GJ Gas WHISPAIR Blower

    • This model vent cavities are plugged for purge or drain.
    • Special long-life mechanical seals with Viton™ O-rings are installed at each bearing to control gas and oil leakage.
    • The seal incorporates a proprietary geometry that promotes enhanced cooling and extended life.
    • RAM gas units are suitable for both vacuum or pressure service.
    • Alternate materials and optional O-ring material are available for these machines.

    RAP Engineers is the leading provider of powder solutions, products & services for the Food, Dairy, Pharmaceutical, Sugar, Starch & Specialty Industries.



    About Us




    Privacy Policy

    Contact Us

    Please contact us to learn more from our experts

    10 + 3 =