Air foil bearings

The build and operating principles of Aerzen’s current range of blowers are simple and efficient at the same time. Air supply in modern wastewater treatment plants is designed to guarantee maximum uptime, high energy efficiency and lengthy maintenance intervals. For this reason, Aerzen uses only air foil bearings. No oil or other lubricants are needed, just air. In this article, we explain the innovative bearings used in Aerzen Turbo Blower technology, which is designed for the future.

 

 

MAGNETIC BEARINGS VS AIR FOIL BEARINGS

Bearings based on simple physics

As an effective bearing without any mechanical friction at all, AERZEN uses compressed air in the two radial drive shaft bearings and the axial bearing for absorbing the axial forces. In doing so, air is never pumped with high pressure externally into the bearing shell. Instead, the compressor principle is used in a brilliantly simple way. Due to natural imbalance, when starting the turbo blower, the rapidly rotating shaft generates an eccentric circular motion in the air gap of the bearing. With the minimal distance to the bearing wall, the shaft increases the pressure in this area, and counterforce is generated in the form of an increase in pressure. This forces the shaft back in the opposite direction. Due to the rapidly increasing speed, the shaft centres in the bearing itself and increases the pressure in the air gap to more than 30 bar.

The prevailing torques are so high that they keep the shaft permanently in the centre of the bearing, even in the case of considerably varying and challenging operation conditions (e.g., in the event of overpressure), and this takes place in a free-floating manner without surface contact. What is extraordinary about this principle is the fact that the air cushion forms automatically without the need for further energy input.

Turbo blowers made by other manufacturers operate with magnetic bearing systems, which also seek to manage high speeds without a mechanical bearing system. However, magnetic bearings need an electrical current to enable the coils, arranged in a circle around the drive shaft, to develop their forces during operation and enable the shaft to rotate free from mechanical friction.

Very changeable operating conditions put the highly complex regulation system of the magnetic bearings to the test and this very frequently results in safety shutdowns of the entire turbo blower for reasons associated with this technology.

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Published in: FuturENVIRO Nº 73 September-October 2020