A fan is a mechanical device used to transport gas. From an energy perspective, it is a mechanical device that converts the mechanical energy of the prime mover into gas energy.

Classification of fans and pumps

Fans and pumps can be divided into:

Axial flow pumps and fans

Centrifugal pumps and fans

Mixed flow pump fan

Cross flow fan

According to the magnitude of its pressure rise, it can be divided into:

High pressure centrifugal fan (2.94-14.6kPa)

Medium pressure centrifugal fan (0.98-2.94kPa)

Low pressure centrifugal fan (<0.98kPa)

High pressure axial flow fan (0.49-4.90kPa)

Low pressure axial flow fan (<0.49kPa)

Fans can be divided into:

Boiler induced draft fan

Wear resistant fan

High temperature fan, etc

1、 Roots blower and pump

Working principle: The three blade impeller is rotated three times by two impellers for suction and exhaust, so that a certain amount of gas surrounded by the box and impeller is transported from the suction side to the discharge side.

Features:

The vibration of noise is very small;

Durable performance, capable of long-term continuous operation;

High speed, high efficiency, and very compact structure;

Simple structure;

Due to the attachment of a gear oil splash device, there will be no oil leakage;

Complete models available for selection according to usage

Bearing application area

Bearing application: Mainly used to withstand radial loads. Commonly used bearings include deep groove ball bearings, angular contact ball bearings, and cylindrical roller bearings. Cylindrical roller bearings are mostly used as load-bearing bearings, while other types of bearings can not only carry loads but also play an axial positioning role on the rotor

Rotor support type: The rotor adopts a support structure with one end fixed and the other end moving. In the two support modes, the front bearing usually plays an axial positioning role in addition to bearing; In the three support mode, the front and rear bearing parts are only used for load-bearing, and a small bearing is used for positioning.

2、 Axial flow pump and axial flow fan

Working principle: The squeezing propulsion force of the rotating blade causes the fluid to obtain energy, increasing its pressure and kinetic energy. When the impeller rotates, the fluid flows in axially, and after obtaining energy in the blade channel, it flows out along the axial direction.

Bearing applications:

Front cylindrical roller bearing

The rear end adopts two sets of angular contact ball bearings of the same model, which are installed back to back and withstand axial forces in two directions. The fit between the outer ring and the bearing shell hole is a clearance fit, and the clearance is adjusted by the width of the outer spacer ring.

TWB bearing application NU2238M, NJ244M, NU2318M

3、 Centrifugal fans and pumps

Working principle:

The centrifugal force generated by the high-speed rotation of the impeller allows the fluid to obtain energy. When the impeller rotates, the fluid flows in axially, then rotates 90 degrees into the impeller channel and flows out radially. The impeller rotates continuously, creating a vacuum at the inlet of the impeller, allowing the fluid to be continuously sucked in and discharged by the pump.

Main bearing models in centrifugal fans

223 series: 22312223162232022324223262233822340223422348

63 series: 631263166320

Other models: 222302223823048

Application of bearings in axial flow fans

Small axial flow fan (impeller diameter less than 1 meter), directly driven by the motor

Large axial flow fan (impeller diameter above 1 meter), motor+two sets of DGBB

Bearing models: 6307, 6308, 6309, 6310, 6312, 6316, 6319, 6320, etc

Application of bearings in single stage centrifugal blowers

Option 1: CRB+ACBB

Model example: NU238+7232

Application of bearings in multi-stage centrifugal blowers

Option 1: One end is CRB+DGBB, and the other end is CRB or DGBB

Option 2: One end is CRB+ACBB, and the other end is CRB

Model examples: NUP238, NUP224, NUP232 (or NJ series)

4、 Faults and causes

Main faults and causes of the fan (excessive bearing temperature rise)

Severe vibration of the bearing box;

The lubricant has poor quality, deteriorates or contains impurities such as dust, sand, dirt, or insufficient filling amount;

The tightening force of the connecting bolts of the bearing box cover and seat is too large or too small;

The installation of the shaft and rolling bearing is skewed, and the front and rear bearings are not concentric;

The rolling bearing is damaged or the shaft is bent.

Problems encountered in the use of bearings

The noise during bearing operation is loud and unacceptable to the user; The phenomenon of early bearing damage is that the bearing heats up after a short operating time (2-3 hours), and over time, it can cause the bearing to burn out due to high temperature.

Cause analysis

The MB type self-aligning roller bearing has a high matching rate between the rollers and the inner and outer race raceways, making it easy to generate heat;

Poor surface roughness;

Surface defects such as bumps and scratches on the surface of the roller and inner race raceway

proposal

Consider the numerical value of the best fit rate between the roller and the inner and outer race raceways.

After determining the numerical value of the coincidence rate, select the appropriate radial clearance tolerance range.

Develop noise (or vibration) standards for "fan specific bearings".

Strictly control the scratches on the surface of the roller and raceway, especially the scratches on the raceway surface at the gap of the inner ring assembly.

Strictly control the curvature of the chamfered arc of the outsourced turning roller according to the drawings.