In many production environments with small flow and high pressure, centrifugal fans are the main ventilation equipment, which not only directly affects the production capacity, but also is very important for the safety of relevant personnel and equipment.
1. Preparations before the centrifugal fan starts
The centrifugal fan should be carefully and comprehensively prepared before operation. The contents mainly include the following aspects:
1. Whether the type, performance index and filling amount of lubricating oil meet the requirements specified in the technical documents.
2. Whether the bearing lubrication system, sealing system and cooling system are working properly, these systems must be started before the centrifugal fan is started.
3. Check whether the power supply and circuit meet the electrical requirements and whether the wiring is correct.
4. Check whether there is condensed water, debris, etc. in the centrifugal fan and the air duct. If there is, it needs to be cleaned up to avoid major accidents when the centrifugal fan is started.
5. Check whether all the anchor bolts are loose, and ensure that the anchor bolts are tightened according to the specified torque, otherwise the centrifugal fan will vibrate more.
6. Manually turn the impeller for a few turns to ensure that the rotor is not rubbed or stuck.
7. Jog the centrifugal fan to see if the rotation direction of the fan is correct.
8. Check whether the protective cover of the rotating parts is installed in place to ensure the safe operation of the centrifugal fan.
9. Check whether the inlet and outlet dampers of the centrifugal fan work normally. The dampers must be closed before starting.
10. Carry out necessary training for fan operators, and have emergency response plans.
11. Check that the manhole door is closed.
12. Start the lubricating oil station and hydraulic oil station at least half an hour in advance to check whether the flow, temperature and pressure of the lubricating oil are normal, and whether the flow of cooling water is normal.
13. If there is a brake system, release the brake first.
2. Precautions for the operation of the centrifugal fan at each stage
1. Start operation
(1) After the centrifugal fan is started, pay close attention to the operation status of each component to confirm whether the sound, bearing temperature, vibration, current, etc. are normal. If there is any abnormality, it should be stopped immediately for inspection.
(2) If the fan is closed for trial operation for a long time, the inlet damper must be slightly opened to avoid excessive increase of the fan temperature.
(3) In the process of opening the baffle, pay close attention to the current situation. Avoid overloading of the motor due to the temperature of the injected gas, excessive resistance, etc.
(4) When the centrifugal fan starts, it is strictly forbidden to enter the stall state.
2. Operation monitoring
(1) Pay close attention to the operating parameters of the centrifugal fan, mainly the temperature and vibration of the bearing.
(2) Pay attention to the sound of the centrifugal fan. If abnormal noise occurs, it is necessary to determine the cause and solve it. Common abnormal noises include fan stall, foreign matter at the inlet, bearing damage, friction between the rotor and static parts, etc.
(3) Pay close attention to the operation of the bearing. The bearing temperature is very important to understand the operation of the bearing. Not only should the bearing temperature be lower than the required alarm value, but also the sudden change of temperature.
(4) Check the condition of the shaft seal. The shaft seal is the sealing structure of the dynamic and static parts. It should be checked whether there is leakage, heat generation, abnormal noise, etc.
(5) Pay attention to the motor current, and overload operation is not allowed.
(6) Monitor the output of the fan, any sudden change should cause alertness.
(7) Pay close attention to the stall signal, and it is strictly forbidden to run in a stall state. When the centrifugal fan stalls, generally the noise increases, the vibration increases, and sometimes the output decreases.
3. Shutdown operation
(1) Usually the centrifugal fan should be shut down after entering a low load, and the inlet damper should be closed after shutting down.
(2) The centrifugal fan with forced lubrication should continue to keep the operation of the lubricating oil station until the main shaft is completely stationary.
(3) For a fan with adjustable moving blades, the moving blades should be adjusted to the fully closed position before shutdown.
(4) When the medium is corrosive gas, attention should be paid to the hazard of the gas after shutdown, and the operating state of the sealed fan should be maintained after shutdown.
(5) Centrifugal fans used to transport high-temperature gas should continue to run until the temperature in the casing is lower than about 100 °C.
(6) If the machine is shut down for a long time, grease should be applied to the rust-prone parts of each mechanical part, and the machine should be cranked regularly to prevent the main shaft from bending.
(7) Empty the cooling water pipes and the water in the cooler to prevent the pipes and coolers from freezing and cracking in winter.