​Practical Function, Construction, and Normal Shutdown Procedures for Backward-Curved Double-Inlet Centrifugal Fans

Practical Function, Construction, and Normal Shutdown Procedures for Backward-Curved Double-Inlet Centrifugal FansConsidering their operating principle, backward-curved double-inlet centrifugal fans typically handle low gas flow rates and small pressure differentials during operation. Therefore, changes in gas specific volume need not be considered, and the gas is treated as an incompressible fluid. Backward-curved double-inlet centrifugal fans can be categorized into two types: right-hand rotation and left-hand rotation. Viewed from the motor side, the impeller rotates clockwise. This is termed a right-hand fan. If the impeller rotates counterclockwise, it is termed a left-hand fan. From a structural perspective, the primary components of a backward-curved double-inlet centrifugal fan are as follows: The casing is typically constructed from steel plate for robustness and reliability. It comes in integral and semi-open types, with the semi-open design facilitating easier maintenance. The impeller consists of blades, an arc-shaped front plate, and a flat rear plate. The rotor requires static and dynamic balancing to ensure stable rotation and optimal performance. The transmission section comprises the main shaft, bearing housing, rolling bearings, and belt pulleys. In practice, the backward-curved double-inlet centrifugal fan unit can be regarded as a variable-flow, constant-pressure device. During operation, when speed is constant, the theoretical pressure-flow curve of the unit must be linear. Due to internal losses, the actual characteristic curve exhibits curvature. After completing work, the backward-curved double-inlet centrifugal fan unit must be shut down following proper procedures. The specific steps are as follows: 1. First, open the exhaust valve sequentially, then slowly close it. 2. Gradually close the inlet throttle valve to 20-25%. 3. Press the stop button, monitoring for any abnormalities during shutdown. Oil supply may be stopped 5-10 minutes after the backward-curved double-inlet centrifugal fan unit has ceased operation, or when bearing temperature falls below 45°C. After shutdown, the backward-curved double-inlet centrifugal fan unit must be rotated 180 degrees periodically within 2-4 hours.