The main power source of the centrifugal fan is the motor. In many cases, the transmission and connection method of the coupling is used to connect the fan and the motor. However, as a rigid connection, not all types of couplings can be used as centrifugal fans. For the transmission, the following editors have sorted out the selection requirements and main reference factors of centrifugal fan couplings for your reference.
1) Selection requirements for centrifugal fan couplings
When choosing a coupling, it is necessary to consider whether the mechanical properties of the coupling can reasonably meet the requirements of the centrifugal fan’s power, bearing capacity, power factor, etc., among which the load bearing capacity is an important indicator for selection, and the centrifugal fan coupling can withstand The loads mainly include: the torque transmitted by the impeller, the amplitude generated by the vibration of the motor itself, the gravity of the coupling itself, the center of mass or the inertial main shaft of the coupling due to various reasons that do not coincide with its rotation axis, and will also be generated during operation. Various forces or couples such as unbalanced centrifugal inertial force and centrifugal inertial couple force directly affect the operation of the coupling.
The shaft of the centrifugal fan belongs to the shafting transmission system that transmits power, and the transmission accuracy is not high, but the flexible coupling with a gap between the elastic coupling of non-metallic elastic elements and the movable element should be avoided to avoid During high-speed rotation, the coupling is damaged.
The two shafts connected by the centrifugal fan coupling are various due to manufacturing error, installation error, deformation of shaft load, base deformation, bearing wear, temperature change (thermal expansion, cold contraction), relative movement between components, etc. relative displacement due to factors. In general, the relative displacement of the two shafts is unavoidable, but the displacement directions generated by the shafting transmission under different working conditions, that is, the axial, radial, angular and displacement sizes are different, so the centrifugal fan The basic requirements for coupling selection are:
1. High strength and large bearing capacity. Due to the possibility of instantaneous peak load on the transmission shaft, the upper limit of the instantaneous torque of the coupling is required to be more than three times the rated long-term torque.
2. High elasticity, large damping, and sufficient vibration damping ability. Reduce the amplitude of shock and vibration to the allowable range.
3. It has sufficient compensation to meet the needs of displacement of the two axes during work.
4. The working reliability and performance are stable, and the coupling with rubber elastic elements should also have the characteristics of heat resistance and aging resistance.
2) Reference factors for selecting centrifugal fan couplings
1. The relative offset of the two axes
The relative offset of the two shafts connected by the coupling is unavoidable due to factors such as manufacturing and installation errors, deformation due to load and temperature difference, clearance caused by running wear, and special requirements for the design of the two shafts. Therefore, the relative offset compensation ability of the coupling is the first factor to be considered in the selection.
2. Load characteristics
The load when the centrifugal fan starts is different from the load during normal operation, and as the power output of the motor changes, the coupling will bear different loads in different periods, so when there is a severe impact load and long-term fluctuating load, Couplings with buffering and vibration damping functions should be selected to reduce peak loads and torsional vibrations, adjust the natural frequency of the system, and prevent resonance.
3. Working speed
The size of the working speed of the coupling is directly related to the centrifugal force of each part of the coupling and the deformation of the elastic element. Excessive speed will lead to increased wear, deterioration of lubrication, and loose connections. The working speed range of the coupling is determined by calculation according to the line speed and the upper limit size of the outer edge allowed by the strength of different materials of the coupling. The allowable speed range of the coupling of different materials, varieties and specifications is different.
4. Outline size
The outer dimensions of the coupling must be accommodated in the installation and disassembly space allowed by the unit. Under the conditions that meet the requirements of use, a coupling with good manufacturing process, convenient assembly and disassembly, easy adjustment, simple maintenance, and no need to move the two connected shafts to replace the wear-resistant parts should be selected. For large fans, it is difficult to adjust the alignment accuracy of the two connected shafts, so flexible couplings with long service life and easy replacement of wearing parts should be selected. In places where it is inconvenient to maintain operations such as underground, or where it is not easy to stop for a long time, couplings that do not require lubrication or have a long maintenance cycle and are easy to maintain should be selected to reduce non-working time and improve production efficiency.
5. Working environment
The working environment, such as temperature, humidity, water, steam, dust, acid and alkali, oil, corrosive medium and radiation, must be considered when selecting centrifugal fan couplings and their protective measures. In the environment of high and low temperature, acid and alkali and corrosive medium, metal elastic elements or flexible couplings with nylon and polyurethane as elastic element materials should be used, and flexible couplings with ordinary rubber as elastic element materials should not be used. The former has higher corrosion resistance, high and low temperature resistance, wear resistance and strength than rubber, but its elasticity and damping properties are not as good as rubber.