Most roots blowers in the market are of three leaf type. Each rotation of the three leaf roots fans uses two sets of three blade impellers to complete three intake and exhaust. It belongs to a positive displacement fan, which is a constant volume rotating gas power machine. The ends of the cylinder are surrounded by the shell and the wall panel. A pair of impellers are connected together (because of the gap, the two impellers do not contact directly), so the air inlet and outlet are separated. By rotating a pair of synchronous gears, both impellers rotate at constant speed in the cylinder. During the process of rotation, the air from the air inlet is pushed continuously by the impeller to the outlet to achieve the purpose of forced exhaust. The structure is simple and the performance is stable.
Friction and collision between two rotors are the most common faults of roots fans. Stop operation and immediately check whether obvious bumps and slight vibration are heard by touching the chassis by hand during operation.
First, don't rush to remove and fully inspect the fan. Touch the bearing bush and the front and rear housing by hand to check that the temperature is normal, then turn the coupling by hand or tool to see if the fan is flexible. If the temperature is normal everywhere, light, heavy and "rebound" phenomenon will appear when rotating, it can be judged that two rotors have collided. When the top shell is open, the rotor surface will have collision marks. Is the surface on one side of the rotor shiny and dented.
The reasons for friction and collision between the two rotors are: (1) loose fit of gear keyway and key. The fastening nut at the end of the gear shaft is loose or the washer is damaged. The hub bore and spindle are not installed correctly. The backlash of gear pair is too large, and the rotor key is loose.
The practice shows that the loose fit between the gear key slot and the drive shaft key is the main reason for the collision between the two rotors. According to further analysis, the working surface (both sides) of the key and shaft is in close contact with both sides of the hub key groove, which interfere with each other, and the rotor torque is transmitted through the two mating surfaces. When the fan starts, it will exert a great force on the key, which will cause long-term one-way force, key or key groove wear, and the matching angle of the two transmission gears is offset, which will cause the change of the rotor assembly spacing, which leads to collision.
At this point, remove the transmission housing and hammer the hex nut at the gear end to check for looseness and check that the washer is not valid. Then use the impact method to ensure that the hub of the drive shaft is not loose by the key. This rectangular method uses hardwood to place it between two rotors with minimum clearance. Rotate the pair by hand or tool so that both rotors collide with the tree. Observe the relative movement between the gear and the shaft during the collision. After a crash, test the gap again with a fill gauge. If there is relative movement between the gear and the shaft during the collision and the clearance between the two rotors changes after the collision, the loose fit between the hub and the drive gear key can be determined. This way, you can replace the key to eliminate the collision between the two rotors. The maintenance time is 2 hours, which can improve the running speed of Roots fan
