Standard Operating Procedure for Centrifugal Blowers in Coking Plants

Thread Content

This post was last edited by HaiChuanLaoYu on 2026-5-3 19:25. 1. Working principle of centrifugal blowers: The centrifugal blowers used in coking plants consist of 3 components, namely the main unit, the auxiliary components, and the supporting components. Among them, the main components of the host unit include the blower’s host, motors (outdoor type, explosion-proof type, and standard type), a direct coupling that connects the host to the motor, and a common base that combines the host and the motor together. The attachment section includes elbow pipes, filters, silencers, general-purpose mesh filters, and special-purpose low-, medium-, and high-grade filters. The supporting components of a centrifugal blower mainly include a manual or motorized disc valve at the blower inlet, flexible connectors, and a motor control starter cabinet. The operating principle of the centrifugal blower in a coking plant is as follows: The rotation of the motor causes the blower impeller to spin, which in turn drives the gas between the blades of the impeller to rotate. The gas is then expelled through centrifugal force, resulting in an increasing gas flow rate. The kinetic energy generated during this flow is converted into static pressure energy; as the fluid volume increases, this static pressure is once again transformed into kinetic energy, and the gas is finally discharged. A negative pressure is created at the center of the impeller, and under the influence of atmospheric pressure, external air can immediately enter. With the continuous rotation of the impeller, air is continuously expelled and replaced, thereby achieving continuous blowing. 2. Common faults of centrifugal gas blowers 2.1 Vibration faults Vibration of the sliding bearings in blowers is a common type of fault that occurs during the operation of centrifugal gas blowers in coking plants; based on their mechanisms, such vibrations can be divided into forced vibrations and excited vibrations. Among them, forced vibration can also be referred to as synchronous vibration; it occurs due to improper installation of sliding bearings, imbalance of components in the shafting, and misalignment of couplings. Poor installation of sliding bearings can lead to issues such as improper bearing clearance, incorrect bearing tension requirements, and unreasonable spacing between contact points. The vibration frequency is the rotational frequency of the rotor; before reaching the critical speed, the amplitude increases as the speed rises. Self-excited vibration can also be referred to as subsynchronous vibration; it is characterized by oil film vortices and oil film oscillations. Its vibration frequency is lower than that of the rotor’s rotation, and it often appears suddenly at a certain speed, causing significant damage. 2.2 Excessively high bearing temperature: Centrifugal gas blowers operate at very high speeds, so there is a certain temperature limit in the areas where the bearings are installed; otherwise, it indicates that the bearing temperature is too high. The reasons for excessively high bearing temperatures include: first, during the assembly process, an overly tight axial clearance or no gap left between the bearing and the top of the bearing housing, which leads to a continuous increase in temperature ； Secondly, in centrifugal gas blowers, dry oil is typically used as a lubricant during operation; as a result, it is common for bearings to develop various faults due to inadequate lubrication. For example, situations such as an excessive amount of lubricating oil, too few oil chambers, too many impurities in the oil, or prolonged use of lubricating oil can all cause the bearing to heat up, leading to its damage. 2.3 Problems caused by the fan rotor: The rotor requires anti-corrosion treatment, as the fan needs to remain stationary for a long time during normal shutdown periods. If the rotor blades are not made of stainless steel, it is necessary to apply a thin layer of grease to them ； In the past, fan rotors were not coated with anti-corrosion grease, and as a result of poor sealing at the valves before and after the fan, the rotor blades would gradually rust, which in turn disrupted the dynamic balance of the fan; this led to significant vibration in the fan as well. 3. Troubleshooting Measures 3.1 Fan Vibration There are many reasons for bearing vibration, and the troubleshooting methods include: adjusting the distance between the bearings and the bearing housing, adjusting the clearance between the bearings or bearing sleeves, or replacing the bearings. The vibration of the blower causes corrosion on the blades; this may be due to the fact that the centrifugal gas blower is not cleaned in a timely manner after operating for extended periods, which leads to the continuous accumulation of dust on the blade surfaces. Once the accumulated dust reaches a certain weight, the centrifugal force generated by the rotation of the impeller throws the dust off the impeller. Since the amount of dust accumulated on each blade may vary, and the dust that accumulates or can be shaken off does not necessarily fall at the same time, uneven dust accumulation on the blades can lead to differences in the mass distribution of the impeller, thereby increasing the vibration of the centrifugal gas blower. At this point, it is necessary to shut down the machine immediately and carry out thorough cleaning of the centrifugal gas blower; by removing the accumulated dust, the dynamic balance of the impeller can be restored, thereby eliminating or reducing the vibration of the blower. Poor bolt fixation can also cause vibration in the fan; therefore, it is necessary to strengthen the bolts and ensure they are tightened firmly to the foundation. When collisions occur in the gas seal, this can lead to intense vibrations, but this issue can be resolved by adjusting the gas seal mechanism and reinstalling it properly. Furthermore, a key condition for hydrodynamic lubrication is an appropriate top clearance of the bearing. The bearing top clearance not only enables the formation of an oil film journal but also creates a floating space once it becomes buoyant. Secondly, it provides space for dissipating the friction heat generated by the lubricant and for the lubricant to flow out. If the clearance is too large, the oil pressure between the bearing and the journal will also decrease, thereby reducing the lifting force of the oil wedge ； If the gap increases to a certain extent, the centrifugal gas blower will naturally experience vibration. It is generally specified that the top clearance for high-speed, light-load bearings should be between 1/1000 and 3/1000 of the shaft diameter. Based on years of operational experience from coking plants, it has been found that the most stable and reliable operation is achieved when the top clearance of the bearing shells is 2.5/1000 of the shaft diameter. 3.2 Excessively high bearing temperature: Firstly, when a very tight fit exists between the bearing and the shaft journal, as well as between the bearing and the bearing housing, which leads to an increase in the bearing’s temperature, it is necessary to adjust the fit between the bearings again. This includes adjusting the nature of the fit between various components, checking their contact surfaces, and making further adjustments. Secondly, situations such as excessive or insufficient addition of lubricant can also lead to excessively high bearing temperatures in centrifugal gas blowers. Therefore, when adding lubricant, it is necessary to measure the actual temperature in advance to prevent this situation from damaging the bearings. When adding lubricant, a filter is needed to prevent impurities from entering, and once the addition is complete, the lubricant should be sealed promptly to avoid the fall of any impurities. In the case of long-term operation, it is necessary to replace the lubricating oil frequently in order to maintain its quality to the greatest extent possible; this helps ensure the quality of the bearings and prolongs their service life. Finally, when the efficiency of natural cooling is low, rapid cooling can be achieved by adding a cooling device. 3.3 Problems caused by the fan rotor The methods for correcting the dynamic balance of the rotor are as follows: Balance correction is carried out simultaneously on both correction surfaces of the rotor. The residual imbalance after correction ensures that, under dynamic conditions, the rotor remains within specified limits regarding imbalance; therefore, dynamic balance can also be referred to as two-sided balance. The most widely used methods for dynamic balancing are on-site dynamic balancing of the entire machine and process balancing. Among them, the test system based on the process balancing method is highly suitable for balancing rotating mechanical parts individually during the production process, as it is subject to relatively little interference and offers high balancing accuracy and efficiency. Therefore, the process balance method plays a very important role in the current field of dynamic balancing. The on-site dynamic balancing method for the entire machine involves using the machine itself as a base for the dynamic balancer. Sensors are used to measure the vibration levels in the areas related to the rotor, and after data processing, it is possible to determine the imbalances present on various balancing surfaces of the rotor as well as their locations. These imbalances can then be eliminated by adding or removing weight. Since the rotor in actual operating conditions does not require processes such as assembly, the entire machine can achieve a higher level of balance accuracy under operation compared to the process balancing method. 4. Maintenance of centrifugal blowers: After operating for an extended period of time, centrifugal blowers in coking plants may develop various types of faults. Therefore, it is necessary to carry out regular maintenance on these blowers, clean the oil tank filters periodically, check the quality of the lubricating oil regularly, and analyze its quality as needed. Furthermore, after centrifugal blowers have been in operation for a period of time, systematic inspections are necessary to take preventive measures, improve the efficiency of these blowers in coking plants, and extend their service life. (1) The blower is one of the most important devices in biochemical treatment; therefore, tasks such as the daily maintenance of centrifugal blowers must be carried out strictly in accordance with the instructions. (2) Try to use two blowers, alternating between them, to avoid using the same one for extended periods of time. (3) The lubricating oil should be replaced at least once every 3 months. During the replacement process, it is necessary to first thoroughly remove any remaining old grease from the bearings before adding new lubricating oil, with the amount added being 1/3 to 1/2 of the available space. When adding new lubricant, it is necessary to take protective measures to prevent impurities from entering the bearings. (4) Regularly clean the silencer at the blower inlet and the air filtration layer, as well as other related components, on a monthly basis, and check periodically whether the filters are damaged. (5) Regularly check the condition of the lubricating grease to promptly identify any issues that require replacement or replenishment. Under normal circumstances, grease needs to be replenished at least every 20 days. However, in cases of leakage or excessively high ambient temperatures, it is necessary to shorten the refueling time based on the actual conditions. (6) The coking plant needs to conduct a comprehensive inspection of the centrifugal blowers once a year. The inspection includes checking whether there is dust, damage, or corrosion on the impellers, whether the bearings are damaged, and whether the labyrinth gaps are too large.