As the main ventilation equipment in most environments, the centrifugal fan is installed and used directly affects the indoor ventilation, but if it is used improperly, it is easy to cause low fan efficiency, poor indoor ventilation, and even affect the service life of the centrifugal fan. How to use it better?
1) Trial operation of the centrifugal fan
In the correct use method of the centrifugal fan, the trial operation is a work that must be carried out after the installation is completed. The main purpose is to check the installation and operation of the fan, so as to avoid the failure of most centrifugal fans in the official operation in advance. The specific method as follows.
1. Preparations
(1) Check electrical equipment, control display instruments; check all inlet and exhaust piping systems of centrifugal fans; check all equipment in the process system.
(2) Check whether the couplings, bearings, rotors, oil seals, and transmission mechanisms of the centrifugal fan are damaged; Whether there is any abnormal sound; whether the instrument is reliable, etc.
(3) Check whether the connecting bolts between the casing and the base are tightened;
2. No-load test run
After everything is normal, start the motor with the inlet adjustment door slightly open, pay attention to record the motor current and start time, adjust the hydraulic coupling, adjust the fan speed, and do the following when the centrifugal fan is at full speed:
(1) Measure the vibration and temperature of centrifugal fan and motor bearings, and the specified data shall not be exceeded;
(2) Measure motor current and voltage;
(3) Check the oil leakage of the lubricating parts;
(4) After the centrifugal fan reaches full speed, gradually open the regulating door to increase the air volume, and be careful not to exceed the specified current;
(5) The centrifugal fan shall not run for less than 20 minutes after the bearing temperature is stable, and prepare for trial operation with load after confirming that the safety and stability requirements are met;
(6) After the test run is over, check whether the fan and supporting equipment are damaged and deal with it;
(7) Check whether the fastening bolts are loose and fasten them;
(8) Close the access door, etc.
2. Test run with load
The test run with load is carried out after the no-load test run is completed and meets the requirements, after confirming that all the equipment of the centrifugal fan’s intake and exhaust systems have been debugged, and after confirming that the entire system is qualified for the test run with load:
(1) After everything is normal, start the motor with the inlet adjustment door slightly open, and pay attention to the motor current;
(2) When the centrifugal fan reaches full speed, gradually open the regulating door to increase the air volume, and pay attention to the current not exceeding the rated value;
(3) The centrifugal fan runs continuously at full speed for 16~24 hours. During this period, the measured bearing temperature, vibration value, motor current, voltage, and load must not exceed the corresponding specified data;
(4) At the end of the operation of the centrifugal fan, the process system where the fan is located should be deloaded and prepared for shutdown;
(5) Gradually close the inlet adjustment door, and stop the motor according to the motor operation regulations.
2) The correct method of using the centrifugal fan
After the centrifugal fan has finished its test run and there is no problem, it can be used normally. But in normal use, you should also pay attention to starting the fan correctly, and in an emergency, you should also perform an emergency stop operation in the correct situation, instead of pressing the emergency stop button at the slightest sign of trouble.
1. Preparatory work before starting the centrifugal fan
(1) Close the regulating damper, close the inlet and outlet damper of the fan;
(2) Manually crank, check the gaps between the various parts of the fan, and turn the impeller and the casing to see if there is friction;
(3) Coupling, pulley protection passport installed in place;
(4) Whether the oil level of the bearing box meets the lubricating oil level during operation;
(5) For centrifugal fans with water-cooled bearings, check whether the water supply of the cooling water pipe is good;
(6) Determine the steering direction of the centrifugal fan, and at the same time check whether there is water leakage, oil leakage, vibration, abnormal noise, odor, etc.
2. Start and stop of centrifugal fan
(1) Start the fan (pay attention to whether it is running smoothly)
After the centrifugal fan is started, gradually open the damper until the actual air volume is required for production; when opening the damper, pay attention to the operating current of the motor to prevent the fan from overloading due to excessive opening of the damper. After starting, the fan bearing temperature should be detected, and the temperature rise of the bearing should not exceed 40 degrees of the ambient temperature of the site.
(2) Fan shutdown
Reduce the load first, then stop the centrifugal fan, and then close the cooling water inlet and outlet valves. If the hot air is conveyed, the fan should be stopped after the heater is stopped, and the fan should be stopped when the outlet temperature of the centrifugal fan drops to 40 degrees. After the fan is stopped, the drain valve at the bottom of the casing should be opened for drainage, and the inlet and outlet dampers of the fan should be closed at the same time.
3. Inspection and emergency stop during operation
(1) Centrifugal fan operation check
a. Listen to whether the fan is running smoothly, whether there is any abnormal sound or friction;
b. Check whether the anchor bolts are loose;
c. Detect the temperature and lubrication of the bearing;
d. Whether the bearing lubricating oil cooling water is unblocked, and whether there is a temperature difference between the inlet and outlet pipes;
e. Is there any leakage of lubricating oil in the bearing box;
f. Whether there is any abnormal noise in the operation of the bearing box and the bearing, and whether the rotation is stable;
g. Check whether the current operation is stable.
(2) Application of emergency stop
a. Found that the fan has severe noise;
b. There is friction between the impeller and the casing;
c. The vibration of the casing suddenly intensified;
d. The bearing temperature continues to rise and exceeds the allowable temperature rise range;
e. The sudden increase in current cannot be restored within 2 minutes;
f. Serious oil leakage from the bearing box;
g. The cooling water is interrupted for more than half an hour.
