9. Since the flow, total pressure, main shaft speed and shaft power of the fan have a fixed relationship, the main shaft speed should not be changed when the motor capacity does not change. If the main shaft speed increases, the motor may be burned due to overload. The motor power used by the fan refers to the power not required when the air inlet and outlet are fully open in terms of mechanical losses and due reserves under a specific mine. If the outlet or inlet of the fan is not connected to the pipeline or is idle without external resistance, the motor may also be burned out. For safety, a valve shall be added to the outlet or inlet pipeline of the fan, and it shall be closed when starting the motor. After turning, the valve shall be slowly opened until the specified working condition is reached, and attention shall be paid to whether the current of the motor exceeds the specified value. High power motors must be started in proper ways, such as voltage reduction, frequency conversion, etc.

（3） The main faults and causes of the fan may occur during the operation of the fan. For the faults generated, the causes must be quickly identified and solved in time to prevent accidents. Faults in the Operation of 4-72-12 Centrifugal Fan and the Causes Table Fault Name Causes Severe Vibration of Bearing Box 1. The fan shaft is different from the motor shaft, and the coupling is installed askew. 2. The casing or air inlet rubs with the impeller. 3. The foundation stiffness is not enough or firm. 4. Impeller rivet is loose or wheel disc is deformed. 5. The impeller shaft disk and shaft are loose, and the coupling bolt is movable. 6. The connection between casing and bracket, bearing box and bracket, bearing box and seat is loose. 7. The air inlet and outlet pipes of the fan are poorly installed, causing vibration. 8. The rotor is unbalanced. Bearing temperature rise is too high 1. The bearing box vibrates violently. 2. The lubricating grease is poor in quality, deteriorated or overfilled, or contains dust, sand, dirt and other impurities. 3. The tightening force of connecting bolts of bearing cover seat is too large or too small. 4. The shaft and rolling bearing are installed askew, and the front and rear bearings are not concentric. 5. The rolling bearing is damaged. The motor current is too high and the temperature rise is too high. 1. The throttle valve in the air inlet pipe is not closed tightly when driving. 2. The flow exceeds the specified value, or the air duct leaks. 3. The gas density conveyed by the fan is too high. 4. The input voltage of the motor is too low or the power supply is cut off individually. 5. The coupling is improperly connected, the leather ring is too tight or the gap is uneven. 6. Affected by the violent vibration of the bearing box. 7. Affected by deterioration or failure of parallel fans. When the belt slides down, the two pulleys are not in the same plane with each other. Belt runout The distance between two pulleys is too close or the belt is too long.

How are dust collectors classified, major Boiler centrifugal fan Do you know how to distinguish it and how to define its economic type? Let's talk about it from these aspects. 1. Dust removal efficiency. Ningbo Boiler centrifugal fan Dust removal efficiency refers to the ratio of the amount of dust collected by the dust collector to the amount of dust entering the dust collector. According to the total dedusting efficiency, the dedusters can be divided into: low efficiency dedusters (50~80%), medium efficiency dedusters (80~95%) and high efficiency dedusters (more than 95%). 2. Dust removal resistance. The resistance indicates the pressure loss when the airflow passes through the dust remover. According to the resistance, dust collectors can be divided into low resistance dust collectors (Δ P<500Pa), medium resistance dust collectors (Δ P=500 ～ 2000Pa) and high resistance dust collectors (Δ P=2000 ～ 20000Pa). 3. Economy. Economy is one of the important indexes for evaluating dust remover, which includes equipment cost and operation and maintenance cost of dust remover. Among all kinds of dust collectors, the equipment cost of electrostatic precipitator is the highest, followed by bag type dust collector, Venturi tube dust collector, cyclone dust collector is the lowest electrostatic precipitator: the dust removal efficiency is high, generally above 99%, and the design efficiency is up to 99.99%. The wet dust collector is commonly known as "water dust collector" : The filtration efficiency can reach more than 85%, and the integrated desulfurization and dust remover of stone water film+swirl plate>>about 80% of desulfurization and dust removal can reach as high as about 95%.

Selection and application of fan performance (I) Description of fan performance: 1. № 10, 12, 16, 20 are converted according to dimensionless performance of № 10 model. 2. № 5, 6, 8 are converted according to dimensionless performance of № 5 model. 3. № 5 and below shall be determined according to the performance of the measured prototype. Note: According to the dimensionless performance curve conversion formula, total pressure H=ρ u2 H (Pa) flow Q=900 π D22 uQ (m3/h) shaft power N=N × D22u3 ρ/4000 (kw), where D2 - impeller outer diameter (m) u - impeller outer edge linear speed (m/s) ρ - gas density (Kg/m3), the required power rate shall be based on shaft power plus mechanical loss and motor reserve. 4. The solid line is № 5 model, and the dotted line is № 10 model. The performance of the fan is expressed by the flow, total pressure, main shaft speed, shaft power, efficiency and other parameters of the fan, and there are certain relationships between the parameters, which are listed in the following table. The relationship of fan performance parameters changes density ρ, speed n changes speed n, atmospheric pressure P, gas temperature t Q1/Q2=n1/n2 H1/H2=(n1/n2) 2 ρ 1/ρ 2 N1/N2=(n1/n2) 3 ρ 1/ρ 2 η 1=η 2 Q1/Q2=n1/n2 H1/H2=(n1/n2) 2 (P1/P2) (273+t2/273+t1) N1/N2=(n1/n2) 3 (P1/P2) (273+t2/273+t1) η 1=η 2 Note: 1. In the middle, Q represents flow (m3/h), H represents total pressure (Pa), N Represents shaft power (kw), η represents total pressure efficiency, ρ represents density (kg/m3), t represents temperature (℃), n represents speed (r/min), and P represents atmospheric pressure (Pa). 2. The footnote symbol 2 indicates the known performance and related parameters, and the footnote symbol 1 indicates the required performance and related parameters. （