In the induced draft system, the centrifugal fan, as a commonly used induced draft fan, is often accompanied by a large load when starting, which is easy to cause the overload of the centrifugal fan motor, especially the centrifugal fan with a certain age is more likely to burn out the motor, so Realizing no-load start-up or reducing the start-up load has become a problem for enterprises to consider. How to realize no-load start of centrifugal fans?
1) The method of centrifugal fan to realize no-load start
1. The reason for the large starting load of the centrifugal fan
The starting load of the centrifugal fan is mainly affected by the airflow. Under normal conditions, the inlet and outlet of the centrifugal fan are open. The larger the size of the impeller blades, the greater the airflow resistance at the beginning of operation, which requires the motor to output more power. In order to drive the impeller of the centrifugal fan, if you want to reduce the starting load, or even start with no load, you first need to solve the problem of airflow resistance.
2. No-load startup method
If you want to start the centrifugal fan with no load, you can do it by adjusting the size of the air inlet. Specifically, close the air inlet valve, disconnect the air flow and the release of the impeller blades at the inlet, so as to reduce the load of the impeller blades to the lower limit. At this time, only the normal output power of the motor can drive the impeller to rotate, and then gradually open the air inlet valve with the operation of the impeller, so that the centrifugal fan can operate normally.
3. Other methods to reduce startup load
In addition to reducing the starting load by controlling the air inlet valve, the centrifugal fan can also be modified by frequency conversion, so that the output power of the motor can be controlled by the frequency converter or the frequency conversion motor, and the work can be adjusted freely when full pressure is required to start frequency to avoid motor burnout. Moreover, the frequency conversion transformation of the centrifugal fan can more conveniently adjust the fan speed, so as to better control the working efficiency of the centrifugal fan.
2)Precautions for starting the centrifugal fan
1. Check the power supply (voltage, switch, etc.), whether the circuit meets the electrical requirements, and whether the wiring is accurate.
2. Check whether there is condensed water, dust and other debris in the fan and pipeline. If there is, it needs to be cleaned up to avoid failure when the fan is started.
3. Confirm whether the anchor bolts, the main body of the centrifugal fan, the accessories and auxiliary devices, and the connecting parts of the connecting pipes are tightened as required.
4. Confirm whether the parts are aligned. For the coupling or centrifugal fan with drive, check the coupling or pulley, whether the V-belt is installed reliably, and whether the coaxiality between the fan shaft and the motor shaft meets the requirements.
5. Check whether the bearing lubricating oil (grease) is sufficient and in good condition. If there is an oil supply device, first test the operation for 2 hours, and measure whether the oil temperature and oil pressure are normal.
6. Whether the grounding protection wire and current protector (fuse) of the motor are installed as required.
7. Manually rotate the fan shaft and prime mover shaft, check whether the rotation is smooth, and confirm that there is no abnormality.
8. Confirm that the air inlet adjustment door of the centrifugal fan is fully closed, and ensure that the starting load is the lower limit.
9. Relevant operators should be trained in advance so that they can quickly and correctly operate the emergency situation when the fan is started.