Roots Blowers By Power Buildesign

Roots Blowers are typically used where the volume of air moved is large compared to the pressure differential. They also can be run in reverse to measure flow of gases or liquids, such as a gas meter. Since there must be operational clearance between the rotors, a single Roots blower can only pump across a limited pressure differential. Use of PTFE wiping strips in race car blowers increases efficiency, but only so far. If a Roots blower is operated out of normal parameters, the heat generated can expand the rotors to the point that they jam, with obvious results. Since Roots blowers can pump large volumes, but only at moderate compression, they are sometimes used in blower stages, frequently with intercoolers used between to cool the gas (air).
Positive Displacement Blowers (Roots Blowers)

Twin lobes and three lobes type blowers fall under this category. They have higher efficiency at moderate compression ratios, and are most efficient in the compression ratios of 1.1 to 2. They find use in applications, which require relatively constant flow rate at varying discharge pressures. These are generally available for capacities 10m3/hr to 10,000m3/hr for pressures up to 1kg/cm2(g) in single stage construction.