With the rapid development of air compression industry technology in our country, air compressors have made significant improvements in structural layout and functional forms. Centrifugal air compressors have become the new generation of air compression equipment. Due to the insufficient understanding of the principle of centrifugal compressors in petrochemical industry production, there is a risk of equipment failure in actual production control. A detailed analysis of the causes and treatment methods of centrifugal compressor failures has a guiding role for the automatic scheduling of mechanical equipment.

The principle of centrifugal compressors

Compressors can be classified into a wide variety of categories from different perspectives. According to the form of the compressor, it can be classified into fixed type, mobile type, enclosed type, etc. Centrifugal compressors are one of the most commonly used devices.

1.1 Principle

Centrifugal air compressors belong to velocity-type compressors. When the gas load is stable, centrifugal air compressors operate stably and reliably. Centrifugal air compressors are driven by impellers to rotate gas at high speed, generating centrifugal force. Due to the diffused flow of gas within the impeller, the flow velocity and pressure of the gas after passing through the impeller are increased, continuously producing compressed air. Based on this principle, centrifugal compressors can provide sufficient air pressure in mechanical transmission systems, promoting effective interaction between mechanical components and providing reliable power for the operation of external connection devices.

1.2 Characteristics

For the compressors used in the early days, centrifugal compressors not only have their component structures been streamlined and improved, but also the overall structural layout of the compressors is more in line with the operational functions of the equipment. At present, centrifugal compressors are assembled with one or more rotating impellers together, which speeds up the gas flow rate and is of great help for the control of gas pressure energy. Depending on the usage conditions, centrifugal air compressors have the characteristic of stable gas pressure operation. The degree of wear formed between components is relatively light, and it will not cause excessive wear to mechanical parts. All these are conducive to increasing the gas operation speed of the compressor and improving the exhaust efficiency.

2. Operation faults and handling

In recent years, the application scope of centrifugal air compressors in the chemical industry has become wider. Such equipment not only provides a guarantee for the regulation of gas pressure energy itself, but also supplies sufficient gas pressure energy to the connected equipment of the compressor, thereby driving the high-efficiency operation of the mechanical transmission system. The compressor utilizes the continuous flow of gas to convert the original mechanical energy of the motor. The working intensity of this process is affected by the working load of the mechanical equipment. Given the continuous increase in the operating load of mechanical equipment in the chemical industry, the failure rate of centrifugal compressors has also significantly increased.

The oil pressure dropped suddenly

The reasons for the sudden drop in the oil pressure of the compressor are rather complex and closely related to the internal components of the unit. The handling of this fault should be determined based on the actual situation. Under normal circumstances, a drop in oil pressure is related to the oil pipes of the lubrication system such as oil pumps and oil pipes. To deal with this fault, it is necessary to conduct pressure tests and carry out handling work. For example, when the malfunction of the oil pump decreases, the pressure also drops. The oil pump should be inspected in a timely manner to identify the cause of the malfunction. When the fault is related to the oil pipe, the fault stems from the leakage caused by the relevant rupture. The specific measure is to replace the new oil pipe.

2.2 The gas outlet flow rate decreases

The main reason for the reduction in gas outlet flow lies in the filter and sealing device. If these two components are not properly controlled, the gas flow will decrease, affecting the normal function of the compressor equipment. Fault handling methods: Firstly, the main cause of the filter failure is the reduction in suction volume due to the clogging of the gas filter. The fault can be eliminated by cleaning the gas filter. The second reason for the malfunction of the sealing device is that the sealing gap is too large, causing leakage. The best solution is to replace the seal or adjust it as per the regulations.

2.3 The outlet temperature of the cooler is too high

The temperature at the outlet of the gas cooler is above 60℃. The occurrence of this fault is related to the cooling water volume of the cooler, as well as the fit between the cooling tubes, flow rate, and tube sheets and tubes. For instance, if the fit between the tube sheet and the tube becomes loose or the cooling tube breaks, the temperature at the outlet of the gas cooler cannot be maintained, causing it to exceed the allowable range. The operating pressure of the compressor was too high, which increased the wear of the components and caused a significant temperature rise. The specific treatment measures include using a tube expander to tighten the loose tubes or blocking both ends of the damaged tubes, and cleaning the core of the cooler.

2.4 The bearing temperature is too high

Bearings are the core components that cause operational failures in centrifugal compressors, determining the overall operational efficiency of the entire equipment. Excessively high bearing temperatures are relatively common faults in compressor operation. The main manifestations of temperature faults are: the orifice diameter of the throttle ring at the oil inlet of the bearing is too small, resulting in insufficient oil intake. The oil pressure of the lubrication system drops or the oil filter is clogged, resulting in a reduction in the oil intake. The cooling water volume of the oil cooler is insufficient and the inlet oil temperature is too high. Based on these fault phenomena, the actual handling process requires the maintenance of the oil pump and oil pipe of the lubrication system or the cleaning of the oil filter. Adjust the inflow volume of the cooling water in the oil cooler; The orifice diameter of the throttle ring at the oil inlet of the bearing is too small, resulting in insufficient oil intake. The orifice diameter of the throttle ring should be appropriately increased. Inspect the oil cooler, eliminate water leakage faults or replace the oil with new oil.

2.5. Excessive vibration of the bearing

Vibration loads increase the load-bearing amplitude of bearings and cause structural failure and wear of centrifugal air compressors, posing a significant threat to the damage of components. The fault manifestation of excessive vibration load on the bearing: The dynamic balance accuracy of the rotor or the large and small gears of the speed increaser is disrupted. The interference between the bearing cover and the back of the bearing bush is too small. Poor gear meshing, severe gear wear or damage. For the handling of such faults, the main approach is to recalibrate the dynamic balance. Scrape the horizontal middle surface of the bearing cover or grind the adjusting gasket to ensure that the interference fit is 0.02 to 0.06mm. Check the wear of the gears, recalculate the non-parallelism, center distance and meshing area between the large and small gears to make them meet the requirements.

2.6 Poor cooling effect of the cooler

The cooler is mainly used to regulate the stability of the internal temperature of the compressor, maintain a balanced temperature to create an excellent operating environment for the compressor, and the failure of the cooling system will affect the performance of the entire equipment. Main fault manifestations: The cooling capacity of the gas cooler has decreased; Dirt on the surface of the cooling tube The cooling tube is cracked or the fit between the tube and the tube sheet is loose. To deal with cooler faults, it is necessary to inspect the components from multiple aspects. At the same time, the cooling water volume should be checked with emphasis. It is required that the water flow rate in the cooler tubes should be less than 2m/s. Clean the cooler core; Block both ends of the damaged pipe or use a tube expander to tighten the loose pipe. When necessary, the cooler can be re-selected for installation and treatment to enhance the cooling effect of the compressor during actual operation and reduce the occurrence rate of cooling failures.

3. Daily maintenance of centrifugal compressors

Under the background of industrial technology reform, many mechanical equipment have been widely applied in industrial production. Air compressors are responsible for converting mechanical energy into gas pressure energy, facilitating the daily operation and regulation of mechanical automatic control systems. On the one hand, regularly inspect the functional status of the mechanical system of the compressor, detect potential faults through equipment debugging methods, and handle operational faults in advance. On the other hand, disassemble and inspect the main components such as bearings and coolers to determine whether there are problems such as wear and lubrication in the mechanical parts, and replenish the lubricating oil in time to improve the operating efficiency of the system. For some aging compressor equipment, new equipment or components can be replaced when necessary. This is also an effective way to prevent faults.

4. Conclusion

Centrifugal air compressors have optimized and upgraded the structure of traditional compressors, enhancing the conversion efficiency of electric mechanical energy by compressors, promoting the generation of more air pressure energy from mechanical energy, and driving the automatic control of chemical machinery equipment systems. Given the functional characteristics of centrifugal air compressors, enterprises must do a good job in handling faults when choosing such equipment, promptly address the fault risks existing during the operation of the compressor, and reduce the functional damage caused by faults to mechanical equipment. In addition to dealing with various faults in a timely manner, it is also necessary to regularly inspect and maintain the components of the compressor to effectively prevent the failure rate of the compressor operation.

Source: Internet

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