A high – temperature fan is a special – type fan specifically designed for high – temperature working environments. Its materials have strong high – temperature and high – pressure resistance. Main types of high – temperature fans include stainless – steel high – temperature – resistant fans, transmission high – temperature fans, and centrifugal high – temperature fans. Blower, Liaoning Blower, Anshan Blower
High – temperature fans are widely used in chemical industries, petroleum, metallurgy, forging, electric power, nuclear power plants, environmental protection, and other fields.
Structural Features of High – Temperature Fans
- A high – temperature fan mainly consists of an impeller, a casing, an air inlet, a motor, a connector, cooling fan blades, and other parts.
- The impeller is a multi – blade single – inlet centrifugal impeller, made of galvanized steel or cold – rolled steel. The blades are designed according to aerodynamic principles. The impeller is composed of ten backward – inclined airfoil – shaped blades, a curved front disk, and a flat rear disk. It is made of high – strength and durable steel plates and has undergone strict dynamic and static balance corrections. It has good air performance, high efficiency, and stable operation.
- The air inlet adopts a convergent streamlined vortex – reducing form, with less air – flow loss and high working efficiency of the high – temperature fan.
- The casing of the high – temperature fan and the motor are installed and connected with metal castings. Cooling fan blades are installed on the motor shaft head. The outer wall of the metal casting is provided with inlet and outlet water pipe interfaces to cool the metal casting and the shaft head and ensure the normal operation of the motor under high – temperature conditions.
- Its motor is a special high – temperature motor, and the fluid part of the high – temperature fan uses temperature – resistant materials. The cooling structure has reliable performance. Compared with other boiler – induced draft fans, it has the advantages of simple structure, convenient maintenance, and high cost – performance.
Root Causes of High – Vibration Common Faults and Their Treatment Measures
-
Dust
The impact of dust on the normal operation of high – temperature fans cannot be ignored. During operation, the impeller of the high – temperature fan is constantly rotating at high speed, causing a large amount of dust to accumulate. This will directly lead to an abnormal operating environment for the rotor, and then the central blades will be directly worn or the rotation speed will be abnormal, resulting in high vibration.
In response to this situation, dust – cleaning work must be done thoroughly, and the environment must be kept clean. In addition, the accumulated dust on the impeller of the high – temperature fan should be regularly cleaned. Secondly, the application of dynamic balance tests, and the rotor correction result must be controlled within 0.1mm/s.
-
Bearings
Bearings are significantly related to the single – frequency and multi – frequency of high – temperature fans. When a bearing fails, the amplitude will increase. Therefore, once a bearing fails, it will directly lead to a vibration fault of the high – temperature fan. After a bearing fails, if the staff fails to detect it in a timely manner, its impact on the high – temperature fan will only be fully manifested after a period of time. In the initial stage, the horizontal and vertical vibrations of the bearing are basically controlled within 3mm/s. However, after 15 to 60 days, due to the faulty operation of the bearing, the amplitude will suddenly increase, and the damage degree of the internal parts of the fan can be imagined.
In response to this situation, two suggestions are given. First, the staff must do a good job of amplitude detection. Once an abnormality occurs, timely and effective initial tension treatment should be carried out. Second, the quality of the bearings is of great importance. Purchasers must focus on this when purchasing and test its quality and performance. Before application, the internal structure of the newly purchased bearings should be checked again. If there are any defects, they should be replaced. Secondly, attention should also be paid to bearing heating. For example, when using the oil – boiling method for heating, contact between the bearing and the bottom of the oil tank must be avoided, and the temperature should be controlled between 95 and 100℃. The heating should be ensured to be even, and wiping treatment should be carried out before installing the main shaft.
-
Reinforcement and Assistance
Fan operation is always accompanied by vibration. Although high – temperature fans have stronger adaptability to the environment than other ordinary fans, it does not mean that harsh environments will not affect them. For example, the vibration fault caused by the abnormal rotation speed of the high – temperature fan blades will directly affect its normal operation.
Based on past experience, it is recommended to reinforce the body of the high – temperature fan to avoid such problems. In practice, high – temperature cement is commonly used for reinforcement, which can avoid the situation of high vibration due to an unsteady body. At the same time, maintenance personnel should use professional tools to adjust the rotor frequency of the fan and the concentricity of the central runner and the motor in a timely manner to avoid the problem of abnormal rotation speed of the central runner. After the adjustment, the foundation bolts of the body need to be tightened to ensure that the body base and the shim are firmly welded.
-
Fan Rotor Imbalance
Poor system dust – removal effect causes uneven wear of the impeller, resulting in rotor imbalance; ash powder in the flue gas is deposited on the back of the blades, resulting in imbalance; the fixing bolts of the detachable blade wear – resistant lining plate are loosened and fallen off.
Facing the above situations, the following treatment methods can be tried:
- If the overall wear of the impeller is not serious, the problem can be directly solved through on – site dynamic balance.
- If the overall wear of the impeller is more serious and the wear – resistant layer of the blade has been worn away by more than 2/3, to avoid continued wear and the scrapping of the entire impeller, the method of first surfacing the wear – resistant layer and then conducting on – site dynamic balance can be adopted. This can be repeated, and the service life of the impeller can be nearly doubled. The surfacing electrode can be selected according to the blade base material. For example, D227 and R317 are surfacing materials with good performance. In addition, the location and thickness of the surfacing layer should be selected according to the structure of the fan inlet to improve the surfacing quality. For a fan with double – sided air inlets, the severely worn part is in the middle of the blade. The weld of the surfacing layer here should be dense and thick, which can effectively increase the wear cycle.
- If the fixing bolts of the detachable blade wear – resistant lining plate are loosened and fallen off, since the wear – resistant layer of the fan blade is detachable. Before conducting the dynamic balance of the fan, it is necessary to carefully check each bolt of the impeller, re – tighten the loosened ones and spot – weld them. Otherwise, it is difficult to eliminate vibration through on – site dynamic balance.
Faults of high – temperature fans are all premonitory. Staff should pay special attention to this. Once a fault is detected during inspection, even if it is only a minor one, the cause should be identified and the elimination work should be done in a timely manner. Many high – temperature fan faults are due to the fact that minor faults are not detected. When the working time reaches a certain level, more serious problems will be exposed. The daily real – time monitoring and maintenance of high – temperature fans are particularly important. The maintenance of high – temperature fans must be timely and the root causes must be found, and scientific treatment should be carried out.
