Positive Displacement Blowers

ZG positive displacement blower

Positive displacement (PD), roots-type air blowers

Ecotao supplies positive displacement blowers as replacements for Duroflow, RAM/RCS, Root URAI, Sutorbilt Legend and Tuthill Competitor brands and models.


Positive displacement air delivery, aeration and vacuum equipment

To be able to quote properly, please describe your application and advise the altitude, air flow required (m3/h) and and pressure (or vacuum) needed at this flow rate. There are various pressure units such as PSI, mbar, Pascal etc.

These blowers have a long life. There are cases of these blowers running for 20 and more years with good service maintenance.

A rotary positive blower, also called a positive displacement blower, or PD blower “pushes” a relatively constant volume of the gas from the inlet to the discharge (outlet). Gas is not compressed as in a compressor. The volume of gas the machine pumps is determined by the configuration of the casing and rotating parts.

Flow through a PD blower is constant, irrespective of pressure changes. This is different from a centrifugal compressor that maintains a constant pressure while the flow varies.

Variable speed motors or variable speed drive (VSD)

A VSD can be very effective on a PD machine. The reduction in electrical power consumption is much less than it would be with a dynamic machine (like a fan or centrifugal compressor), but it can still be substantial.
Roots blower parameters

The below graphs illustrate the details you need to consider when selecting your blower.

Positive displacement blower brands

Ecotao will advise on and select an air blower according to your specific need and application.

The pipe size that delivers air from the blower to the system is one of the most important considerations. The diameter of the pipe selected is based on the air flow and pipe length or distance to the point of air discharge. The pipe diameter is selected to minimize friction losses. See Engineering Toolbox Spreadsheet to calculate the required pipe diameter.
For example, at 2m water (gauge pressure, 0.21kg/cm2 or 206mbar at sea level), 5m3/min (300m3/h), 25m pipe length and with a maximum allowed pressure loss of 50 cm (0.05kg/cm2, 50mbar), a 100 mm ID pipe is the minimum needed.

Applications and use

Pneumatic conveying of bulk materials

Positive displacement blowers are used in suction (vacuum) or discharge pressure. Machine sizes range from small blowers installed on vehicles to very large blowers used in pneumatic elevators for vacuum operated ship unloading. The hourly capacity of such unloading installations is up to 1000 tons at present.


Any aquaculture unit can use these blowers for aeration of ponds, tanks, dames, etc.
Pressurized aeration of basins in sewage treatment plants.
Filter flushing blowers in drinking water production plants.
Gas boosting blowers.
Steel production.
Application in direct-reduction plants.
High vacuum boosters.

Equipped with special shaft seals.
Conveying of practically all gases.

Positive displacement blowers are found in the chemical, petrochemical, and metallurgical industries. Special designs are available to handle aggressive gases. These machines are used in both conventional and nuclear power plants and can comply with the safety regulations.