We’re continuing our series on selecting blower technology for industrial wasterwater treatment applications with an overview of the technology behind centrifugal blowers. We covered positive displacement blowers last week. You can read the previous articles from the series by choosing “wastewater” under industries or by following the link.
Centrifugal Blower Technologies
Because centrifugal machines operate with pressure and flow rate as dependent variables, centrifugal blowers operate best as base load machines or in applications with constant pressure. Currently, three different designs of the modern centrifugal blower are in common use:
Multistage Centrifugal Blower – The multistage centrifugal blower (MSCB) is usually coupled directly with an induction motor driveshaft, resulting in a slower operating speed. The design principles are fairly simple: for more flow, increase the impeller diameter; for more pressure, increase the number of impellers (stages). Like all centrifugal machines, the impeller configuration has a large effect on the performance of a MSCB. A MSCB can have two to 11 stages and any number of impeller geometries to create the desired flow and pressure curve.
Integrally Geared Turbo Blower – The integrally geared turbo blower (IGTB) is driven by an induction motor via a speed-increasing gearbox. Although the motor rotates at only 1,800 or 3,600 RPM, the blower impeller rotates as fast as 30,000 RPM to produce the desired flow and pressure. The IGTB uses inlet guide vanes and variable diffuser vanes to control the air flow and pressure.
High Speed Turbo Blower
- Airfoil bearing high speed turbo blowers (HSTB) were introduced to the U.S. wastewater treatment market around 2007. Unfortunately, the technology was misapplied in many applications which led to headaches for both manufacturers and consumers. It is important to know that there are installations of airfoil bearing HSTB that have great reliability, thanks to well-applied technology and a clean working environment.
- Magnetic bearing HSTB have been used in the wastewater treatment industry longer than the airfoil design. Over the years, magnetic bearing turbo has proven extremely reliable due to the magnetic bearing controller that often prevents catastrophic failure. Both the airfoil and magnetic bearing machines use high speed permananet magnet motors controlled by variable frequency drives that allow the impellers to turn up to 60,000 RPM to create the desired air flow and pressure.
Which Centrifugal Technology Should You Choose?
Of the three centrifugal technologies, the multistage centrifgual blower (MSCB) offers the most versatility in wastewater treatment due to its ability to convey digester gas as well as air. The MSCB also offers the widest flow range due to the numerous configurations available. The integrally geared turbo blowers offers the largest flow rates and, thus, is not suitable for use in small plants. Finally, the high speed turbo blower offers the greatest potential in industrial wastewater applications due to its small footprint, high efficiency, and integrated control system.
Atlas Copco Efficiency Blowers
We’ll finish our series on selecting blower technology next week with a brief discussion on desigining the blower system. In the meantime, explore Atlas Copco’s blower technologies by visiting Atlas Copco’s efficiency blowers microsite.
