Xin Feng Classroom | Ventilator Series: Explosion-Proof Centrifugal Fans

01  

Components of Explosion-Proof Centrifugal Fans  

Explosion-proof centrifugal fans primarily consist of an impeller, casing, inlet, regulating damper, and drive assembly.

Impeller: Welded between the curved wheel cover and plate-shaped wheel disc with 12 backward-inclined wing-shaped blades, ensuring high efficiency, low noise, and high strength. After static and dynamic balancing, the impeller operates smoothly. The impeller structure is identical for both ventilation fans and exhaust fans of the same model.     Casing: A worm-shaped body welded from ordinary steel plates. The fan casing is constructed as an integral structure. The induced draft fan features a cleaning door on the volute plate, with appropriate thickening to prevent soot wear and extend service life.     Inlet: A tapered, streamlined integral structure bolted to the inlet side of the casing.         Damper: Used to regulate fan flow. All blades are axially mounted in front of the inlet. The external drive structure ensures flexible and convenient rotation.     Drive Assembly: Consists of the main shaft, bearing housing, and coupling. The main shaft is fabricated from high-quality steel. The water-cooled integral bearing housing employs rolling bearings.

02 

 Explosion-Proof Centrifugal Fan Correct and Safe Operation 

   1. Starting the Explosion-Proof Centrifugal Fan

    (1) Under normal conditions, start the fan according to the startup sequence.

    (2) After startup, once the motor reaches normal speed, immediately open the inlet valve and adjust it to the required position (operated from the control room). Monitor whether the current remains within the specified range. 

   (3) Listen for normal fan and bearing sounds, and check bearing vibration levels.

 (4) If initial startup fails, investigate the cause and eliminate it before attempting another startup. 

2. Explosion-Proof Centrifugal Fan Shutdown 

(1) Under normal conditions, follow the system shutdown sequence.

 (2) Ensure all personal protective equipment is fully worn.

 (3) Do not clean energized equipment with wet towels or other tools. If cleaning is necessary, power must be disconnected.

 (4) Strictly adhere to operating procedures; no violations permitted.

03 

 Causes and Solutions for Vibration in Explosion-Proof Centrifugal Fans 

        Unlike other types of fans, explosion-proof centrifugal fans operate with working media entering and exiting along the axial direction of the fan, requiring operation under centrifugal force. Vibration in centrifugal fans is unavoidable. The maximum bidirectional amplitude of the fan bearings should not exceed 0.10 mm.

Excessive vibration in centrifugal fans can cause motor overcurrent and excessive temperature rise, potentially leading to motor coil burnout in severe cases. It also adversely affects components such as bearing anchor bolts, bearings, and shafts. There are only three causes for excessive vibration in centrifugal fans: 1. Fan manufacturing quality; 2. Installation quality; 3. Operational factors.     To minimize centrifugal fan vibration, strictly adhere to proper installation procedures: conduct equipment inventory and inspection; perform foundation checks, markings, shim adjustments, and anchor bolt configuration. Install the fan ensuring stable component placement; finalize alignment upon completion.     Before commissioning, conduct a comprehensive inspection covering the manufacturer's build quality and any potential damage or deformation during transport. This includes verifying shaft deflection, which must not exceed 0.10 mm. Due to field limitations, only a rough survey using a theodolite is feasible at this stage.     Simultaneously verify that the outlet angle of the centrifugal fan impeller blades matches the manufacturer's design specifications. Use a vernier caliper to check whether the clearance between the main shaft and impeller conforms to the design drawings. Additionally, inspect whether the thickness of the fan casing and its reinforcing steel meets the design requirements. Finally, ensure the regulating damper and collector are functioning properly.

Beep beep beep, pop quiz time!         After four sessions of study, I believe everyone should have a solid grasp of fans by now. Here are a few questions to test your knowledge. Take a look: 

 1. An explosion-proof centrifugal fan primarily consists of __________.      A. Impeller    C. Air inlet    B. Outer casing    D. Drive assembly       Click blank to view answer       ABCD            

2. Ventilator blades come in ______________ configurations.      A. Forward-curved blades    C. Curved blades    B. Backward-curved blades    D. Radial blades       Click the blank to view the answer       ABD            

 3      Common collector types currently include __________ categories.      A. Cylindrical    C. Arc-shaped     B. Conical    D. Conical-arc    Click the blank to view the answer       ABCD           

  4      The fan's tongue consists of _________.      A. Pointed tongue    C. Short tongue     B. Deep tongue    D. Flat tongue       Click blank to view answer       ABCD             

 5      The impeller of a centrifugal fan consists of _________.      A. Blades    C. Front plate     B. Shaft plate    D. Rear plate       Click blank to view answer       ACD              

 6      Centrifugal fans have __________ transmission methods.      A. Seven    C. Eight     B. Four    D. Six       Click blank to view answer       D             How many did you get right?