Fans are widely used in various fields, especially in the application of boilers. Fans are a kind of machinery that converts the mechanical energy of the prime mover into gas that can be transported, and adds energy to the gas. The fan plays the role of mutual balance and ventilation during the combustion process of the boiler, and continuously delivers the air they need inside the boiler, and at the same time discharges the flue gas to the outside of the boiler to ensure the normal operation of the boiler combustion. And it is one of the indispensable mechanical equipment in various fields. There are many types of fans, generally including supply fans, primary fans, induced draft fans, desulfurization booster fans, powder exhausters, etc. However, in the actual long-term continuous work of the fan, there will be harsh operating conditions and high failures.
Over the years, problems such as high fan failure rate and low reliability have plagued the operation and maintenance personnel of boilers in these power plants. The fan failures encountered during maintenance and operation mainly include: serious damage to the wind wheel; fan vibration; bearing damage; serious oil leakage from the bearing box, etc. It is of great significance to diagnose and analyze the cause of fan failure and take scientific solutions to ensure the efficient operation of the fan and meet the production requirements. With the rapid development of my country's economy, the problem of energy shortage has become more prominent, and the demand for it has gradually increased. One of the energy sources that has been widely used for a long time is thermal energy, and in the development of many enterprises, the role played by engineering operations It is also very important, especially power engineering. Therefore, this article analyzes the development status of thermal energy and power engineering and the problems existing in the use of boilers, and discusses its future development direction.
the
1. The working principle and main structure of the fan
The working principle of the fan is that the fan relies on the input mechanical energy to increase the gas pressure and discharge the gas. It is a driven fluid machine. The performance parameters of the fan mainly include flow, pressure, power and speed. In addition, the noise and vibration are also the main reference objects for measuring the fan. The fan is mainly composed of a casing, an impeller, an air inlet, an air inlet box, an inlet adjustment door, a rotating group, a coupling, a bearing box, etc., and the motor drives the rotor group to drive the fan impeller to rotate.
The working principle of the centrifugal fan is basically the same as that of the turbo compressor, but because the gas flow rate is low and the pressure changes little, generally there is no need to consider the change of the gas specific volume, that is, the gas is treated as an incompressible fluid. Centrifugal fans can be made into two types of right-handed and left-handed. When viewed from the side of the motor, the impeller rotates clockwise, which is called a right-handed fan, and counterclockwise, called a left-handed fan.
2. Analysis of Common Faults of Boiler Fans
With the development of social economy and science and technology, and the acceleration of social industrialization, various high-tech products facilitate our production and life. Boiler induced draft fan is such a high-tech product. However, failures are inevitable during use. The failure of the boiler fan can be divided into mechanical failure and performance failure. Mechanical failures of boiler fans include mechanical failures, mechanical vibrations, lubrication system failures and bearing failures. These failures can affect the stable operation of the boiler, or force the boiler to shut down, causing major economic losses. The fan is the main auxiliary equipment of the boiler, and its operation directly affects the operation of the boiler. A detailed analysis of the failure of the boiler fan will help to ensure the safe and reliable operation of the boiler.
1. Cause analysis and countermeasures of blade wear
There are many reasons for the blade wear of the boiler fan, mainly including the following: during the operation of the boiler fan, the working condition is not designed, and the arc tangent of the blade inlet is different from the direction of the air intake in the impeller, resulting in air intake The angle of attack; the airflow dust particles in the fan wear and wash the inlet position of the blade; the fan inlet is equipped with a cyclone dust removal device, which has a good dust removal effect, but if the dust removal device is not cleaned in time, the fan is easy to enter the dust accumulation, The airflow generated in the boiler fan drives the dust particles into the vicinity of the blades, which has the same function as the file blades and increases the degree of blade wear; in addition, the welds or constituent materials of the fan blades have not reached a certain hardness, and once the dust enters, the hardness will be even higher. High, the speed of blade wear and erosion will be accelerated.
For blade wear faults, the solutions are as follows: First, strengthen the cleaning of dust accumulation in the dust removal equipment to reduce the amount of dust in the flue gas; starting from the operation of the boiler and coal quality, the dust accumulation of the dust removal equipment should be cleaned every 2 hours. At least one treatment can effectively reduce the degree of abrasion and erosion of the blades by dust particles. Second, reduce the exhaust resistance and keep the arc tangent of the blade inlet consistent with the air flow direction of the blade passage. Third, strengthen the transformation of the impeller of the boiler fan to increase the service life of the impeller. After the transformation, the single-plate curved blade can be used to replace the blade behind the wing, which increases the load of the motor to a certain extent, but can effectively avoid blade wear. The dust accumulation of the equipment will damage the balance and prolong the service life of the impeller. Fourth, materials with higher hardness can be used to effectively improve the wear resistance of the boiler fan blades.
2. The fan bearing temperature is too high
During the process of the fan continuously transporting air into the pot, the bearing will rise due to abnormal temperature. The actual analysis shows that the reason for the excessive temperature of the fan bearing is due to the abnormality of the bearing, insufficient cooling time, and poor lubrication effect. caused by other factors. During the normal operation of the fan, cooling water is needed to cool down the bearing. If you are not careful, it is easy to cause the cooling water pipe to enter the boiler room, which will cause the temperature of the cooling water pipe to rise, which will affect the cooling effect of the bearing. In addition, after long-term operation of the bearing, there will be peeling and increased gaps, which will also cause the temperature of the bearing to rise. In order to reduce the friction between the bearings, lubricating oil is usually applied to the fan bearings. The bearings will consume a large amount of lubricating oil during operation. Once the bearings run for a long time, the friction will increase. In addition, during the normal operation of the fan, part of the water will enter the equipment inside the fan, and the oil film on the bearing surface will be destroyed by the water. The decreasing lubricating oil and the destroyed oil film will cause the bearing to continue to wear The temperature will rise during operation, and severe cases will be burned out.
Before solving the temperature fault of the fan bearing, the maintenance personnel can first rotate the bearing to listen to the sound and vibration of the bearing to quickly determine the cause of the possible bearing failure, which can greatly improve the speed of troubleshooting. During the normal working process of the fan, the maintenance personnel can take preventive measures as early as possible according to a series of problems in the operation of the bearing, such as checking the lubricating oil applied on the bearing, and always ensuring that the softened oil has not expired or been damaged. Pollution and other quality problems, only in this way can the normal operation of the bearing be guaranteed. Secondly, the quality of the bearing must be strictly inspected to prevent aging and wear from affecting the operation of the bearing. The operating conditions meet the standard requirements.
3. Excessive fan noise
If there is a problem with the dynamic balance of the fan, or if the fan blades are damaged during the operation of the fan, it will cause vibration. noise. In addition, the fan is a centrifugal fan, which makes a loud whistling sound during operation and is very noisy. The noise pollution generated by the boiler fan seriously affects the rest of the residents living around it, causing harm to their health. Therefore, it is necessary to take comprehensive noise reduction measures.
Auxiliary dust suppression measures can be appropriately added to solve the problem of excessive dust. The air outlet pipe of the fan is connected to the wet dust collector through a long metal pipe. The dust collector first removes the large particles of dust and then enters the dust reduction and sound insulation room. The technical measures of the combination of expansion pipe and expansion chamber in the dust reduction and sound insulation room can reduce the gas flow rate. , so that small particles of dust naturally fall together with the condensation of water vapor in the flue gas, and at the same time play the role of resistant noise reduction. When the gas with low flow rate enters the noise reduction room and further expands, it passes through the resistive material for sound absorption and noise reduction, and then leads to the resistive muffler at the bottom of the chimney through the pipe, and the flue gas is discharged into the atmosphere through the expansion pipe at the top of the chimney. The drum and induced draft fan of the boiler can be centrally arranged in the same soundproof fan room. The blower sucks air in the room and takes away the heat emitted by the drum, induced draft fan and smoke pipe in the room at the same time. The wind muffler enters the interior. The boiler exhaust pipe is equipped with a muffler. Generally, a small-hole muffler or a multi-layer orifice plate throttling and pressure-reducing composite muffler with small-hole injection is used. In addition, a low-speed fan can be used to increase the impeller of the induced fan and reduce the speed of the fan. The pressure coefficient of the fan remains unchanged, and the fan operates normally to achieve the purpose of reducing noise. To reduce the impact on the residents during the operation of the boiler fan.
4. The oil leakage of the bearing box is serious
There are several reasons for the oil leakage of the bearing box: the design of the felt ring seal is unreasonable; the structural size design of the seal cavity is unreasonable; the running gap between the retaining ring and the shaft at the bottom of the seal cavity is too large, which is also a cause of leakage; the seal packing Improper use; voids in the seal due to differential pressure.
Measures that can be adopted: Reasonable design of felt ring seal structure, setting oil retaining device and return hole, the oil retaining ring should be fixed with the shaft and rotate with the shaft, which can not only prevent oil leakage, but also lubricate the oil close to the seal cavity. The oil is thrown out, which can have a better effect on preventing oil leakage. The oil deflecting ring should be installed in the oil chamber, as close as possible to the sealing chamber, but not to cause friction with the outside of the chamber, and the clearance is preferably 0.05-0.10mm. At the same time, a return hole is set in the lower part of the sealed cavity, so that the tendency of oil leakage is greatly reduced.
Reason: This phenomenon is mainly due to the sudden increase in the vibration of the fan during operation. This is because when the gas enters the impeller, there is a certain angle with the working surface of the rotating blade. According to the principle of fluid mechanics, the gas will have a vortex on the non-working surface of the blade, so the ash particles in the gas will slowly deposit due to the vortex effect. on non-working surfaces. Airfoil blades are prone to dust accumulation. When the dust accumulation reaches a certain weight, due to the centrifugal force of the impeller rotation, part of the dust accumulation will be thrown out of the impeller, resulting in uneven dust accumulation on the blades and uneven mass distribution of the impeller, which will increase the vibration of the fan. .
Solution: In this case, it is usually only necessary to remove the dust accumulated on the blades to reduce the vibration of the fan. The usual treatment method is to open the inlet door of the fan casing after a temporary shutdown, and the maintenance personnel enter the casing to remove the accumulated dust on the impeller.
3. Conclusion
the
Under the continuous promotion of my country's mechanical technology level, the efficiency of the fan (fan efficiency refers to the output power divided by the shaft power. The shaft power is the input power of the fan. And the reliability is continuously improved, but the fan is in the process of continuous operation There are still many fault problems. In addition to vibration, high temperature, oil leakage and corrosion wear, there are other faults, such as rotating surge and stall, which are the reasons for the failure of the fan. Therefore, in order to ensure that the fan can be safe and stable In operation, the maintenance personnel should check and repair the fan faults according to different fault causes, so as to minimize the probability of faults and major faults.
Fans are widely used in various fields, especially in the application of boilers. Fans are a kind of machinery that converts the mechanical energy of the prime mover into gas that can be transported, and adds energy to the gas. The fan plays the role of mutual balance and ventilation during the combustion process of the boiler, and continuously delivers the air they need inside the boiler, and at the same time discharges the flue gas to the outside of the boiler to ensure the normal operation of the boiler combustion. And it is one of the indispensable mechanical equipment in various fields. There are many types of fans, generally including supply fans, primary fans, induced draft fans, desulfurization booster fans, powder exhausters, etc. However, in the actual long-term continuous work of the fan, there will be harsh operating conditions and high failures.
Over the years, problems such as high fan failure rate and low reliability have plagued the operation and maintenance personnel of boilers in these power plants. The fan failures encountered during maintenance and operation mainly include: serious damage to the wind wheel; fan vibration; bearing damage; serious oil leakage from the bearing box, etc. It is of great significance to diagnose and analyze the cause of fan failure and take scientific solutions to ensure the efficient operation of the fan and meet the production requirements. With the rapid development of my country's economy, the problem of energy shortage has become more prominent, and the demand for it has gradually increased. One of the energy sources that has been widely used for a long time is thermal energy, and in the development of many enterprises, the role played by engineering operations It is also very important, especially power engineering. Therefore, this article analyzes the development status of thermal energy and power engineering and the problems existing in the use of boilers, and discusses its future development direction.
the
1. The working principle and main structure of the fan
The working principle of the fan is that the fan relies on the input mechanical energy to increase the gas pressure and discharge the gas. It is a driven fluid machine. The performance parameters of the fan mainly include flow, pressure, power and speed. In addition, the noise and vibration are also the main reference objects for measuring the fan. The fan is mainly composed of a casing, an impeller, an air inlet, an air inlet box, an inlet adjustment door, a rotating group, a coupling, a bearing box, etc., and the motor drives the rotor group to drive the fan impeller to rotate.
The working principle of the centrifugal fan is basically the same as that of the turbo compressor, but because the gas flow rate is low and the pressure changes little, generally there is no need to consider the change of the gas specific volume, that is, the gas is treated as an incompressible fluid. Centrifugal fans can be made into two types of right-handed and left-handed. When viewed from the side of the motor, the impeller rotates clockwise, which is called a right-handed fan, and counterclockwise, called a left-handed fan.
2. Analysis of Common Faults of Boiler Fans
With the development of social economy and science and technology, and the acceleration of social industrialization, various high-tech products facilitate our production and life. Boiler induced draft fan is such a high-tech product. However, failures are inevitable during use. The failure of the boiler fan can be divided into mechanical failure and performance failure. Mechanical failures of boiler fans include mechanical failures, mechanical vibrations, lubrication system failures and bearing failures. These failures can affect the stable operation of the boiler, or force the boiler to shut down, causing major economic losses. The fan is the main auxiliary equipment of the boiler, and its operation directly affects the operation of the boiler. A detailed analysis of the failure of the boiler fan will help to ensure the safe and reliable operation of the boiler.
1. Cause analysis and countermeasures of blade wear
There are many reasons for the blade wear of the boiler fan, mainly including the following: during the operation of the boiler fan, the working condition is not designed, and the arc tangent of the blade inlet is different from the direction of the air intake in the impeller, resulting in air intake The angle of attack; the airflow dust particles in the fan wear and wash the inlet position of the blade; the fan inlet is equipped with a cyclone dust removal device, which has a good dust removal effect, but if the dust removal device is not cleaned in time, the fan is easy to enter the dust accumulation, The airflow generated in the boiler fan drives the dust particles into the vicinity of the blades, which has the same function as the file blades and increases the degree of blade wear; in addition, the welds or constituent materials of the fan blades have not reached a certain hardness, and once the dust enters, the hardness will be even higher. High, the speed of blade wear and erosion will be accelerated.
For blade wear faults, the solutions are as follows: First, strengthen the cleaning of dust accumulation in the dust removal equipment to reduce the amount of dust in the flue gas; starting from the operation of the boiler and coal quality, the dust accumulation of the dust removal equipment should be cleaned every 2 hours. At least one treatment can effectively reduce the degree of abrasion and erosion of the blades by dust particles. Second, reduce the exhaust resistance and keep the arc tangent of the blade inlet consistent with the air flow direction of the blade passage. Third, strengthen the transformation of the impeller of the boiler fan to increase the service life of the impeller. After the transformation, the single-plate curved blade can be used to replace the blade behind the wing, which increases the load of the motor to a certain extent, but can effectively avoid blade wear. The dust accumulation of the equipment will damage the balance and prolong the service life of the impeller. Fourth, materials with higher hardness can be used to effectively improve the wear resistance of the boiler fan blades.
2. The fan bearing temperature is too high
During the process of the fan continuously transporting air into the pot, the bearing will rise due to abnormal temperature. The actual analysis shows that the reason for the excessive temperature of the fan bearing is due to the abnormality of the bearing, insufficient cooling time, and poor lubrication effect. caused by other factors. During the normal operation of the fan, cooling water is needed to cool down the bearing. If you are not careful, it is easy to cause the cooling water pipe to enter the boiler room, which will cause the temperature of the cooling water pipe to rise, which will affect the cooling effect of the bearing. In addition, after long-term operation of the bearing, there will be peeling and increased gaps, which will also cause the temperature of the bearing to rise. In order to reduce the friction between the bearings, lubricating oil is usually applied to the fan bearings. The bearings will consume a large amount of lubricating oil during operation. Once the bearings run for a long time, the friction will increase. In addition, during the normal operation of the fan, part of the water will enter the equipment inside the fan, and the oil film on the bearing surface will be destroyed by the water. The decreasing lubricating oil and the destroyed oil film will cause the bearing to continue to wear The temperature will rise during operation, and severe cases will be burned out.
Before solving the temperature fault of the fan bearing, the maintenance personnel can first rotate the bearing to listen to the sound and vibration of the bearing to quickly determine the cause of the possible bearing failure, which can greatly improve the speed of troubleshooting. During the normal working process of the fan, the maintenance personnel can take preventive measures as early as possible according to a series of problems in the operation of the bearing, such as checking the lubricating oil applied on the bearing, and always ensuring that the softened oil has not expired or been damaged. Pollution and other quality problems, only in this way can the normal operation of the bearing be guaranteed. Secondly, the quality of the bearing must be strictly inspected to prevent aging and wear from affecting the operation of the bearing. The operating conditions meet the standard requirements.
3. Excessive fan noise
If there is a problem with the dynamic balance of the fan, or if the fan blades are damaged during the operation of the fan, it will cause vibration. noise. In addition, the fan is a centrifugal fan, which makes a loud whistling sound during operation and is very noisy. The noise pollution generated by the boiler fan seriously affects the rest of the residents living around it, causing harm to their health. Therefore, it is necessary to take comprehensive noise reduction measures.
Auxiliary dust suppression measures can be appropriately added to solve the problem of excessive dust. The air outlet pipe of the fan is connected to the wet dust collector through a long metal pipe. The dust collector first removes the large particles of dust and then enters the dust reduction and sound insulation room. The technical measures of the combination of expansion pipe and expansion chamber in the dust reduction and sound insulation room can reduce the gas flow rate. , so that small particles of dust naturally fall together with the condensation of water vapor in the flue gas, and at the same time play the role of resistant noise reduction. When the gas with low flow rate enters the noise reduction room and further expands, it passes through the resistive material for sound absorption and noise reduction, and then leads to the resistive muffler at the bottom of the chimney through the pipe, and the flue gas is discharged into the atmosphere through the expansion pipe at the top of the chimney. The drum and induced draft fan of the boiler can be centrally arranged in the same soundproof fan room. The blower sucks air in the room and takes away the heat emitted by the drum, induced draft fan and smoke pipe in the room at the same time. The wind muffler enters the interior. The boiler exhaust pipe is equipped with a muffler. Generally, a small-hole muffler or a multi-layer orifice plate throttling and pressure-reducing composite muffler with small-hole injection is used. In addition, a low-speed fan can be used to increase the impeller of the induced fan and reduce the speed of the fan. The pressure coefficient of the fan remains unchanged, and the fan operates normally to achieve the purpose of reducing noise. To reduce the impact on the residents during the operation of the boiler fan.
4. The oil leakage of the bearing box is serious
There are several reasons for the oil leakage of the bearing box: the design of the felt ring seal is unreasonable; the structural size design of the seal cavity is unreasonable; the running gap between the retaining ring and the shaft at the bottom of the seal cavity is too large, which is also a cause of leakage; the seal packing Improper use; voids in the seal due to differential pressure.
Measures that can be adopted: Reasonable design of felt ring seal structure, setting oil retaining device and return hole, the oil retaining ring should be fixed with the shaft and rotate with the shaft, which can not only prevent oil leakage, but also lubricate the oil close to the seal cavity. The oil is thrown out, which can have a better effect on preventing oil leakage. The oil deflecting ring should be installed in the oil chamber, as close as possible to the sealing chamber, but not to cause friction with the outside of the chamber, and the clearance is preferably 0.05-0.10mm. At the same time, a return hole is set in the lower part of the sealed cavity, so that the tendency of oil leakage is greatly reduced.
Reason: This phenomenon is mainly due to the sudden increase in the vibration of the fan during operation. This is because when the gas enters the impeller, there is a certain angle with the working surface of the rotating blade. According to the principle of fluid mechanics, the gas will have a vortex on the non-working surface of the blade, so the ash particles in the gas will slowly deposit due to the vortex effect. on non-working surfaces. Airfoil blades are prone to dust accumulation. When the dust accumulation reaches a certain weight, due to the centrifugal force of the impeller rotation, part of the dust accumulation will be thrown out of the impeller, resulting in uneven dust accumulation on the blades and uneven mass distribution of the impeller, which will increase the vibration of the fan. .
Solution: In this case, it is usually only necessary to remove the dust accumulated on the blades to reduce the vibration of the fan. The usual treatment method is to open the inlet door of the fan casing after a temporary shutdown, and the maintenance personnel enter the casing to remove the accumulated dust on the impeller.
3. Conclusion
the
Under the continuous promotion of my country's mechanical technology level, the efficiency of the fan (fan efficiency refers to the output power divided by the shaft power. The shaft power is the input power of the fan. And the reliability is continuously improved, but the fan is in the process of continuous operation There are still many fault problems. In addition to vibration, high temperature, oil leakage and corrosion wear, there are other faults, such as rotating surge and stall, which are the reasons for the failure of the fan. Therefore, in order to ensure that the fan can be safe and stable In operation, the maintenance personnel should check and repair the fan faults according to different fault causes, so as to minimize the probability of faults and major faults.