Installation and adjustment of centrifugal fan
The centrifugal fan is a driven fluid machine, which uses the input mechanical energy to increase the air pressure and discharge the gas.
Centrifugal fans are widely used in factories, coal mines, tunnels, cooling towers, vehicles, ships and buildings for ventilation, dust removal and cooling; ventilation and induction of boilers and industrial furnaces; cooling and ventilation in air conditioning system equipment and household appliances ; Drying and selection of grains, etc.
1. The installation of the overall unit of the centrifugal fan should be placed directly on the premise and leveled with double inclined pad iron.
2. For the centrifugal fan assembled on site, the cutting surface on the base should be properly protected, and there should be no rust or cracks. When the base is placed on the base, use double inclined pads to level it.
3. The bearing seat and the base should be closely connected, and the vertical unevenness should not exceed 0.2/1000. Use a level to measure on the main shaft, and the horizontal unevenness should not exceed 0.3/1000. .
4. Before bearing pad grinding and scraping, the axis line of the rotor should be calibrated with the axis line of the casing, and at the same time, the gap between the impeller and the air inlet and the gap between the main shaft and the hole shaft of the rear baffle plate of the casing should be adjusted to meet the requirements of the equipment technical documents .
5. When the main shaft and bearing bush are assembled, inspection should be carried out according to the requirements of the equipment technical documents. An interference of 0.03 to 0.04 mm should be maintained between the bearing cap and the bearing pad (measure the diameter of the bearing pad and the inner diameter of the bearing seat).
6. When assembling the fan casing, the position of the casing should be corrected based on the axis of the rotor, and the axial and radial gaps between the air inlet of the impeller and the air inlet of the casing should be adjusted to the range specified in the equipment technical documents at high speed, and the foundation should be checked at the same time. Are the screws tight. If the gap value is not required by the equipment technical documents, the general radial gap should be 1/100 of the impeller diameter, and the axial gap should be evenly distributed, and its value should be 1.5/1000~3/1000 of the impeller diameter (the smaller the diameter take the larger value). When adjusting, try to make the clearance value smaller to improve the efficiency of the fan.
7. When the fan is aligned, the misalignment between the fan shaft and the motor shaft: the axial positioning displacement cannot exceed 0.05mm, and the inclination cannot exceed 0.2/1000.
8. For the centrifugal fan installed with roller bearings, the different axis degrees of the bearing holes on the two bearing frames can be determined by the ease of rotation after the rotor is installed.
The centrifugal fan is a piece of equipment with a complicated structure, mainly composed of air inlet, damper, impeller, motor and vent. In different states, the effect of the centrifugal fan is not the same. Therefore, the operating conditions of different parts are not uniform, and the effect of the centrifugal fan will be affected. Adjusting the centrifugal fan to the best state can start from many aspects.
1. Centrifugal fans allow full-voltage starting or step-down motoring, but it should be noted that the current at full-voltage starting is about 5-7 times the rated voltage, and the step-down starting torque is positively related to the square of the voltage. When the grid capacity is insufficient, Should be started with a reduced voltage.
2. During the test run of the centrifugal fan, read the product manual carefully and check whether the wire connection is consistent with the wiring diagram; carefully check whether the working voltage of the fan power supply meets the requirements, whether the power supply is broken or in the same phase, and the volume of the distribution components Is it in compliance with the regulations.
3. There are no less than two people in total during the test run. One person controls the power supply, and the other person observes the operation status of the fan. If any abnormal situation is found, immediately shut down and check; first check whether the rotation direction is correct; after the centrifugal fan starts running, immediately check whether the operating current of each phase is Whether the balance and current exceed the rated voltage; if there is any abnormal phenomenon, it should be shut down and checked. After running for five minutes, turn off the fan and check whether there is any abnormality in the fan, and then restart the operation after confirming that there is no abnormality.
4. When the two-speed centrifugal fan is tested, it should be started at low speed first to check whether the direction of rotation is correct; when it is started at high speed, the fan must be stopped before starting to prevent high-speed reverse rotation, causing switch tripping and motor damage.
5. When the centrifugal fan reaches normal speed, measure whether the input current of the fan is normal, and the operating current of the centrifugal fan cannot exceed its rated voltage. If the operating current exceeds its rated voltage, check whether the supplied voltage is normal.
6. The motor power required by the centrifugal fan means that under certain working conditions, the required power is larger when the air inlet is fully open for the centrifugal fan and the fan box. There is a risk of damage to the motor if it is operated with the air inlet fully open. When the fan is tested, it is best to close the gate valve on the inlet or outlet pipe of the fan, and gradually open the gate valve after operation to reach the required working condition, and pay attention to whether the operating current of the fan exceeds the rated voltage.