A Roots blower pump is a positive displacement Rotary Lobe pump that operates by pumping air or a gas with a pair of meshing lobes not unlike a set of stretched gears. Air/gas is then trapped in pockets surrounding the lobes and carried from the intake side to the exhaust.

Why is the rotary lobe blower called a ‘Roots Blower’?

The positive Rotary Lobe blower was designed in the 1850s by the two brothers Mr. Francis and Philander Roots. It was later patented in 1860 by the brothers and “Roots” became the name of the design.

What is the basic principle of a ‘Roots Blower’?

The Roots blower principle consists of the following: the process starts with air flowing from the inlet port into the element chamber. The timed rotation of the rotors against the wall of the chamber creates a so-called ‘air flow direction’. At this point, there is still atmospheric pressure in these chambers.

As soon as the first lobe passes the opening to the pressure side, the system pressure is adjusted. This is called isochoric compression. The rotors seal each other off to the inside, which prevents a change of pressure.

How does a ‘Roots Blower’ operate?

A Roots blower operates using the isochoric compression principle, also known as external compression. The pressure increase is achieved by intermittently transporting a gaseous medium (e.g. atmospheric air) into a system.

By forcing the medium from atmospheric conditions into a system with a given resistance (e.g. a water column, distribution network), the relevant pressure increase is achieved. The Roots blower will operate at a controlled output level to overcome this resistance.

What is the Robuschi ‘Roots Blower’ series comprised of?

The Robuschi ‘Roots Blower’ series is known as the RBS bare shaft series, it is composed of three conjugate lobe shaped rotors (Tri-lobe) which rotate inside a pre-machined chamber. The chamber is sealed by the rotating rotors, and the rotors are synchronised by means of a timing 1:1 gear ratio, positioned at the end of the shafts.
Bearings are positioned externally to the compression chamber with an oil lubricated system. The drive shafts have labyrinth style oil seals, so called because of the labyrinth of grooves that the oil must pass through. The splash lubrication system uses a fine mist of oil for lubrication. With this design one gets oil free compressed air or vacuum.

  • Rotary lobe blowers can achieve a pressure of up to 1,000 mbar (g), vacuum to 100 mbar (a) & air flow to 25,000 m³/h
  • There is a very wide range of models, sizes, options, and configurations available.
  • Optimal performance and maximum uptime with consistent quality and reliability in every application.

Also, the new ROBOX range of Robuschi Rotary Lobe Blowers / Vacuum exhausters has been reinvented, focusing on delivering exacting customer requirements.

Recently launched the new ROBOX blower unit concept, a cutting-edge solution that can accommodate rotary lobe and screw technologies to provide users with greater choice than ever before in helping meet their industrial air and gas needs.

With the new ROBOX, the difference between lobe and screw technology is reduced to just a few components. This makes it simpler than ever to change from one technology to another and embraces the ongoing shift in mindset from capital investment to total cost of ownership.

Robuschi rotary lobe blowers are available at varying pressures above atmospheric up to 1,000 mbar (g) and for vacuum duties up to 100 mbar (a) along with maximum air flow of 25,000 m³/h.


Mark Burn
Air & Vacuum Technologies (Pty) Ltd
Tel. +27 11 318 3241/2/3/4

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