Luoyang Petrochemical Polypropylene Co., Ltd. air separation unit air compressor, is a centrifugal air compressor imported from the United States ugly, the company model 3100 into 3, graded compression, two-stage cooling. The model is a shaft type, the first stage impeller is installed at the end of the low speed gear shaft to form a first stage rotor; the first stage impeller is installed at both ends of the high speed gear shaft to form a first stage rotor; the two gear shafts are driven by an active large gear They are distributed on both sides of the active bull gear and they are mounted in a horizontally split gearbox. The intercooler is a high efficiency finned heat exchanger. The instrument control system is advanced, using digital micro-computer Jiang 0 for control, 0 from 3 models is from 36833.310, human type 3 air compressor related performance parameters 1.
Index unit value Exhaust pressure Exhaust volume Active large gear speed 1 stage Rotor speed 1 stage Rotor speed 1 stage Rotor vibration interlocking value 1 stage Rotor vibration Interlocking value Air filter resistance, alarm value Surge sensitivity 10 also 2 vibration Fault characteristics The unit vibration monitoring system uses the US Bentley vibration probe and transmitter to track memory monitoring in real time through a microcomputer. During the operation, the vibrations at all levels are lower at the initial stage of the driving operation, which does not exceed 10μm. However, with the extension of the running time, the vibration value of the IIra-class rotor gradually increases. After about half a year of operation, the vibration value reaches 23, causing the unit to interlock. parking.
3 Failure Analysis The causes of vibration of centrifugal air compressors mainly include failure of the rotor coupling unbalanced vibration monitoring system and misalignment of the bearing. The following is an itemized analysis.
3.1 Vibration monitoring system failure If the vibration measuring probe and the transmitter are faulty, the vibration measurement result will be inaccurate, and the vibration value will suddenly change. The vibration measuring probe used by the unit is an eddy current displacement sensor. If the locking probe is fixed to the connector and the locking nut is loose, the vibration will cause the gap between the probe and the shaft to change, the gap is reduced, the vibration value becomes larger, and the gap is increased, and the vibration value becomes smaller; Zero drift of the vibration probe and transmitter can also cause vibration measurement results to be out of alignment.
3.2 Coupling failure and alignment between the bad large gear rotor and the motor, coupled by a toothed coupling, transmitting power and torque. The coupling can transmit the most torque, and can compensate for the serious wear of the coupling due to the installation error of the coupling between the two axes, and the uneven settlement of the unit foundation, which may cause poor alignment. 60 of the mechanical failure of the rotor system is caused by poor centering. The rotor system with poor alignment will produce a series of dynamic effects harmful to the equipment during its operation, causing early damage to the oil film and the deflection of the shaft, resulting in abnormal vibration of the unit, and the vibration will not be correct. The increase in severity increases.
3.3 Rotor Unbalanced Centrifugal Compressors are rotary machines that cause vibration when the rotor is unbalanced. The rotor imbalance due to uneven manufacturing of the rotor, called the initial imbalance, should be found and corrected in the manufacturer; the rotor is unbalanced due to improper assembly errors during the transportation and storage of the rotor, at the beginning of the start-up operation, Large vibrations are generated; the rotor is unbalanced due to the falling off of the components on the rotor or the foreign matter adhering to the impeller flow path, and the vibration value suddenly rises. All of the above can be ruled out. Due to the uneven wear of the particles on the impeller in the uneven deposition medium of the uneven scale medium on the impeller, the dynamic balance of the rotor is destroyed, and the vibration value is also increased.
3.4 Bearing Defects This unit has a Class 1 rotor and a Class 1 rotor supported by tilting pad radial bearings. When the system is subjected to small disturbances, each piece of bearing bush will follow the amount of disturbance and react accordingly to balance with it, so that it returns to a stable state, so it has better stability. However, when the bearing is too large due to the wear gap, the vibration value of the unit will increase. Cracking and peeling of the bearing babbitt also causes the vibration value of the unit to increase.
4 Troubleshooting 4.1 Checking the adjustment or replacement of the vibration probe and transmitter This is the first consideration and the simplest treatment. Check if the lock nut fixed to the connector of the vibration probe is loose. Check whether the gap voltage between the probe and the shaft is normal. The normal value is 6.3. If necessary, replace the vibration probe and transmitter. In order to facilitate troubleshooting, we replaced the stage rotor vibration probe and transmitter, but the start-up test, the high vibration value of the fault still exists, it can eliminate the vibration monitoring system failure factors.
4.2 Checking the coupling The first step is to check the coupling and alignment. Open the coupling and found that the lubrication is not so good and some of the grease has hardened. After the cleaning, each tooth surface was inspected, and no trace of wear was observed. Check the alignment and found no abnormalities. From the inspection situation, the factors of the coupling failure can be eliminated.
4.3 Check the rotor and bearing First remove the volute of each level, and find that the impeller diffusers of all levels have different degrees of fouling. The thickest part has 0.8. The inlet pipe also has a lot of dust. These dusts were thoroughly cleaned. Then open the upper cover to check the gears, the tooth surface is very smooth, no signs of wear are found, and the meshing area of ​​the meshing gap is normal. Remove the bearing inspection at all levels, the bearing babbitt alloy is intact, and the radial clearance is checked in the normal range. The other parts of the gap were also reviewed, and no abnormalities were found. At the start-up test, the vibration value of the first-stage rotor is normal, 9,10. From the inspection results, it is likely that the dust in the air is unevenly deposited on the impeller, which destroys the dynamic balance of the first-stage rotor and causes the vibration value to increase. The first-stage rotor speed is up to 51000, and the blood and dynamic balance requirements are more demanding.
4.4 Renovation of the fouling of the air filter impeller at the suction inlet, and the filter effect of the suction air filter is poor, which requires careful inspection and analysis. The filter was originally designed as a 4-plate and plate filter with a size of 800,800. The filter area is small, the filtration accuracy is not too high, and the sealing of the plate frame and the box steel structure is not strict, resulting in a small part of the air. After filtering, it enters the compressor directly. Although it is sealed with adhesive tape, the effect is not good. In order to completely improve the filtration effect, the filter was transformed into a self-cleaning air filter with a large filtration area and high filtration precision.
The self-cleaning air filter is assembled by assembling eight diameter 600-cylinder filter units, and the cartridge filter unit absorbs the ambient atmosphere under the negative pressure of the suction port of the air compressor, and the dust in the atmosphere is deposited on the filter cartridge. Outside; at the valve opening, the self-cleaning air nozzle sprays a short time of about 0.18 high pressure 0.45 0.7M, the airflow, enters the filter cylinder through the venturi, and blows back from the inside to the outside, blowing the dust outside the filter cartridge Drop it. This backflushing process is intermittent, and under the control of the system, only a certain number of filter cartridges are in a self-cleaning and backflushing state, and the remaining filter cartridges are still working, so the normal operation of the air compressor is not affected. After nearly two years of use, the new filter has a good filtering effect, and the scale of the impeller is very small, and the phenomenon that the dynamic balance of the stage rotor is destroyed is not increased.
5 Conclusion Through the above analysis and processing, it can be concluded that the filter effect of the air suction port filter is poor, resulting in uneven deposition of dust on the rotor, destroying the rotor dynamic balance, and now the vibration value gradually increases with the running time. Increase. The use of precision and high efficiency air filters can eliminate the resulting vibration faults.
Han Jie, Zhang Ruilin. Rotating machinery failure mechanism and diagnostic technology. Beijing Machinery Industry Wang Zhiqing. Adjustable operation and vibration of the turbine compressor. Beijing Machinery Industry Publishing, page 105
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