What are the key reasons for the imbalance caused by the fan impeller? The reasons for the imbalance caused by impellers in application can be briefly divided into two types: impeller wear and impeller fouling. The causes of these two situations are related to the ash removal equipment connected to the induced draft fan. The reason for the imbalance of the impeller caused by dry ash removal equipment is mainly due to wear, while the reason for the imbalance of the impeller caused by wet ash removal equipment is mainly due to scaling. The technical master of Huake Zhichuang Dynamic Balancing Machine is as follows:
1. Impeller wear:
Although the dry test ash removal equipment can remove the vast majority of large particles of smoke and dust, small amounts of large particles and many fine smoke and dust particles accompany high-temperature and high-speed smoke and dust, causing continuous erosion of the blades by the induced draft fan. Over time, blade like wear occurs at the inlet and outlet of the blades. Because this type of wear is irregular, it leads to the imbalance of the impeller. In addition, the surface of the impeller is easily oxidized at high temperatures, transforming into thick oxide skin. The binding force between this oxide skin and the surface of the impeller is not uniform, and some oxide skin will automatically fall off due to vibration or centrifugal force, which is also one reason for the imbalance of the impeller.
2. Scaling of the impeller:
The humidity of the smoke and dust purified by the wet ash removal equipment (Venturi water film dust collector) is too high, and the uncleaned smoke and dust particles, although very small, have a high viscosity. When they rely on the induced draft fan, they can be sucked onto the non working surface of the blades under the action of gas vortices, causing severe smoke and dust scaling at the inlet and outlet of the non working surface, and gradually thickening. When some of the ash deposits fall under the combined action of centrifugal force and vibration, the balance of the impeller is destroyed, and the entire induced draft fan is causing vibration.
2、 Preventive Measures for Solving Impeller Imbalance
1. Solution to impeller wear:
The best way to prevent impeller damage caused by dry ash removal is to improve the wear resistance of the impeller, in addition to enhancing the dust removal function of the dust removal equipment. At present, the more mature method in this regard is thermal spraying technology, which uses a unique method to transform wear-resistant and heat-resistant metal or ceramic materials into high-temperature and high-speed particle flow, and spray paint onto the surface of the impeller blades, producing a layer of strong coating with much higher wear resistance, heat resistance, and oxidation resistance than the material of the blades themselves. This not only alleviates the damage caused by the damage to the dynamic balance of the impeller, but also alleviates the unevenness caused by the oxide layer.
When using an induced draft fan, it is best to use an impeller that has been thermally sprayed for dry ash removal. Impellers that have not been solved by overheating spraying in application can be considered for thermal spraying treatment during equipment maintenance. Although this will increase the production or maintenance costs of the impeller, it will increase the service life of the impeller by 1-2 times and increase the maintenance cycle of the induced draft fan. This further reduces the operating profit of the induced draft fan and all manufacturing systems, resulting in excellent overall benefits.
2. Method of handling impeller scaling:
(1) Water spray descaling: It is a common descaling method, and the sprinkler system is installed on the casing of the induced draft fan, consisting of pipes, three nozzles (one at the impeller outlet and two at the inlet), and drainage holes. The water source is usually tap water, with a pressure of about 0.3MPa. This type of approach is generally reasonable. The flaw is that each shutdown for descaling takes a longer time, requiring multiple shutdowns per month for descaling. Harm the normal application of the unit.
(2) High pressure gas descaling: The system adopts a structure similar to that of a sprinkler system, but its pipelines are high-pressure resistant pipelines, dedicated nozzles, and high-pressure gas sources. This type of equipment is rapid and reasonable in descaling the blades. It can open the high-pressure air source during the normal shutdown interval of the induced draft fan, and successfully remove scale in just a few tens of seconds. Due to its simple and convenient operation, it can be carried out many times a day, which not only solves the problem of laborious and costly manual descaling, but also sharply reduces the production cost of all units. The question is whether the customer has a prepared high-pressure air source (pressure between 0.8 and 1.5MPa, which can use compressed air or nitrogen), otherwise a dedicated high-pressure compressor equipment is required.
(3) Continuous blowing and cleaning of dirt by airflow: Structurally speaking, the continuous blowing equipment does not require external air sources. It uses the exhaust pressure of the induced draft fan itself to guide a small amount of smoke and dust (1% to 2% of the rated wind speed) from the inside of the induced draft fan to a dedicated nozzle located at the inlet of the impeller, and shoots smoke and dust into the non working surface of the blade at a high speed. This type of blowing is continuous, and it is activated with the opening of the induced draft fan, Not only will the smoke and dust that just adhered to the blade be scraped away, but it can also avoid the deposition and thickening of smoke and dust, and there is no need to shut down the machine for descaling. This equipment has a simple structure, minimal modification to the induced draft fan, and excellent anti scaling effect, making it a promising new technology.
3. Calibration of impeller dynamic balancing machine:
Whether it is using impellers treated with thermal spraying or using various methods of descaling, their function is not easy to achieve once and for all. After long-term application, the induced draft fan may still experience vibration exceeding the allowable upper limit. At this point, the imbalance problem of the impeller can only be solved through dynamic balance correction. In the past, the dynamic balance correction of the impeller was generally carried out on a dynamic balance machine, which was very inconvenient for induced draft fans, especially large fans, in application. Therefore, on-site dynamic balancing technology has gained increasing attention in recent years. Its key advantages compared to the past approach are
(1) Avoiding tedious disassembly work, saving disassembly and transportation costs, and reducing maintenance time;
(2) The original installation precision has been stored, improving the balance precision of all induced draft fan systems. The testing standards are outlined below.
Test equipment: on-site dynamic balance instrument
Test steps:
(1) Stick reflective strips on the fan shaft and measure the original vibration values: direct frequency amplitude Vrmso, power frequency amplitude Vo, and phase angle φ O;
(2) Measure the vibration values after adding test weight: direct frequency amplitude Vrmsl, power frequency amplitude V1, phase angle φ 1. Automatically obtain the dynamic balance calculation results (counterweight value and angle of adding counterweight);
(3) After adding counterweight, measure the remaining vibration values: direct frequency amplitude Vrms2, power frequency amplitude V2, phase angle φ 2. If it can meet the vibration inspection standards, it is sufficient.
Testing duration: For skilled on-site testing engineers, completing the above work only takes 1-2 hours. The on-site dynamic balancing process is a mature and user-friendly maintenance technology that can easily, conveniently, and economically solve imbalance problems.
1. Impeller wear:
Although the dry test ash removal equipment can remove the vast majority of large particles of smoke and dust, small amounts of large particles and many fine smoke and dust particles accompany high-temperature and high-speed smoke and dust, causing continuous erosion of the blades by the induced draft fan. Over time, blade like wear occurs at the inlet and outlet of the blades. Because this type of wear is irregular, it leads to the imbalance of the impeller. In addition, the surface of the impeller is easily oxidized at high temperatures, transforming into thick oxide skin. The binding force between this oxide skin and the surface of the impeller is not uniform, and some oxide skin will automatically fall off due to vibration or centrifugal force, which is also one reason for the imbalance of the impeller.
2. Scaling of the impeller:
The humidity of the smoke and dust purified by the wet ash removal equipment (Venturi water film dust collector) is too high, and the uncleaned smoke and dust particles, although very small, have a high viscosity. When they rely on the induced draft fan, they can be sucked onto the non working surface of the blades under the action of gas vortices, causing severe smoke and dust scaling at the inlet and outlet of the non working surface, and gradually thickening. When some of the ash deposits fall under the combined action of centrifugal force and vibration, the balance of the impeller is destroyed, and the entire induced draft fan is causing vibration.
2、 Preventive Measures for Solving Impeller Imbalance
1. Solution to impeller wear:
The best way to prevent impeller damage caused by dry ash removal is to improve the wear resistance of the impeller, in addition to enhancing the dust removal function of the dust removal equipment. At present, the more mature method in this regard is thermal spraying technology, which uses a unique method to transform wear-resistant and heat-resistant metal or ceramic materials into high-temperature and high-speed particle flow, and spray paint onto the surface of the impeller blades, producing a layer of strong coating with much higher wear resistance, heat resistance, and oxidation resistance than the material of the blades themselves. This not only alleviates the damage caused by the damage to the dynamic balance of the impeller, but also alleviates the unevenness caused by the oxide layer.
When using an induced draft fan, it is best to use an impeller that has been thermally sprayed for dry ash removal. Impellers that have not been solved by overheating spraying in application can be considered for thermal spraying treatment during equipment maintenance. Although this will increase the production or maintenance costs of the impeller, it will increase the service life of the impeller by 1-2 times and increase the maintenance cycle of the induced draft fan. This further reduces the operating profit of the induced draft fan and all manufacturing systems, resulting in excellent overall benefits.
2. Method of handling impeller scaling:
(1) Water spray descaling: It is a common descaling method, and the sprinkler system is installed on the casing of the induced draft fan, consisting of pipes, three nozzles (one at the impeller outlet and two at the inlet), and drainage holes. The water source is usually tap water, with a pressure of about 0.3MPa. This type of approach is generally reasonable. The flaw is that each shutdown for descaling takes a longer time, requiring multiple shutdowns per month for descaling. Harm the normal application of the unit.
(2) High pressure gas descaling: The system adopts a structure similar to that of a sprinkler system, but its pipelines are high-pressure resistant pipelines, dedicated nozzles, and high-pressure gas sources. This type of equipment is rapid and reasonable in descaling the blades. It can open the high-pressure air source during the normal shutdown interval of the induced draft fan, and successfully remove scale in just a few tens of seconds. Due to its simple and convenient operation, it can be carried out many times a day, which not only solves the problem of laborious and costly manual descaling, but also sharply reduces the production cost of all units. The question is whether the customer has a prepared high-pressure air source (pressure between 0.8 and 1.5MPa, which can use compressed air or nitrogen), otherwise a dedicated high-pressure compressor equipment is required.
(3) Continuous blowing and cleaning of dirt by airflow: Structurally speaking, the continuous blowing equipment does not require external air sources. It uses the exhaust pressure of the induced draft fan itself to guide a small amount of smoke and dust (1% to 2% of the rated wind speed) from the inside of the induced draft fan to a dedicated nozzle located at the inlet of the impeller, and shoots smoke and dust into the non working surface of the blade at a high speed. This type of blowing is continuous, and it is activated with the opening of the induced draft fan, Not only will the smoke and dust that just adhered to the blade be scraped away, but it can also avoid the deposition and thickening of smoke and dust, and there is no need to shut down the machine for descaling. This equipment has a simple structure, minimal modification to the induced draft fan, and excellent anti scaling effect, making it a promising new technology.
3. Calibration of impeller dynamic balancing machine:
Whether it is using impellers treated with thermal spraying or using various methods of descaling, their function is not easy to achieve once and for all. After long-term application, the induced draft fan may still experience vibration exceeding the allowable upper limit. At this point, the imbalance problem of the impeller can only be solved through dynamic balance correction. In the past, the dynamic balance correction of the impeller was generally carried out on a dynamic balance machine, which was very inconvenient for induced draft fans, especially large fans, in application. Therefore, on-site dynamic balancing technology has gained increasing attention in recent years. Its key advantages compared to the past approach are
(1) Avoiding tedious disassembly work, saving disassembly and transportation costs, and reducing maintenance time;
(2) The original installation precision has been stored, improving the balance precision of all induced draft fan systems. The testing standards are outlined below.
Test equipment: on-site dynamic balance instrument
Test steps:
(1) Stick reflective strips on the fan shaft and measure the original vibration values: direct frequency amplitude Vrmso, power frequency amplitude Vo, and phase angle φ O;
(2) Measure the vibration values after adding test weight: direct frequency amplitude Vrmsl, power frequency amplitude V1, phase angle φ 1. Automatically obtain the dynamic balance calculation results (counterweight value and angle of adding counterweight);
(3) After adding counterweight, measure the remaining vibration values: direct frequency amplitude Vrms2, power frequency amplitude V2, phase angle φ 2. If it can meet the vibration inspection standards, it is sufficient.
Testing duration: For skilled on-site testing engineers, completing the above work only takes 1-2 hours. The on-site dynamic balancing process is a mature and user-friendly maintenance technology that can easily, conveniently, and economically solve imbalance problems.
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