Direct drives are often used for compact fans. The impeller is mounted directly onto the electric motor’s driven shaft, putting a great deal of strain on the bearings in the fan’s electric motors. In these operating conditions, bearings can wear prematurely, leading to downtime and unwanted maintenance costs.
Single-row deep-groove ball bearings are the most common type of bearing used for direct drive systems.
Shaft voltage induced predominantly by operation of electric motors on variable frequency drives (adjustable speed drives) creates an environment where electrical discharge current can flow through the bearing. This intermittent current flow can create arc pits that damage the bearing’s internal surfaces and lubrication, causing electrical erosion. A solution to this phenomenon is NSK deep-groove ball bearings with ceramic balls, called ceramic hybrid bearings. These specialty bearings offer protection from current flow through the bearing by using the exceptionally high electrical insulating properties of ceramic balls to create a high resistance barrier between the bearing’s steel rings.
The electric motor is mounted parallel to the fan’s impeller. In this case, power is transferred via one or more V-belts and pulleys. This design is usually used for medium to large fans. High volume flows and a build-up of heat can cause the bearings to wear out prematurely, resulting in production downtime and high maintenance costs.
The SNN series of plummer blocks from NSK features five different sealing arrangements to meet a range of requirements. The individual components are easy to fit, remove and maintain. Together with advantages such as high rigidity and good heat transfer, the split housings in the SNN series help to reduce costs.
NSKHPS Spherical Roller Bearings
Self-Lube® HLT Inserts
Self-Lube® Inserts with Flinger Seals
The electric motor is mounted on the same axis as the fan’s impeller. The shafts of the electric motor and the fan are connected by a torsionally flexible coupling. This method of connecting the impeller with the electric drive is mainly used for medium and large fans.
The tough conditions can cause the bearings to wear out prematurely, reducing productivity and driving up maintenance costs.