Problem detection and discussion of new compressor

Chemical enterprises are industrial systems that carry out extensive work on equipment diagnostic technology. A set of equipment often has to be operated continuously for one to two years. In recent years, more than one single series of large units have been introduced, and several hundred thousand yuan to several days will be lost. million dollar. According to Japanese statistics, after using equipment fault diagnosis technology, the accident rate can be reduced by 50% to 75%, and the maintenance cost can be reduced by 25% to 50%.

At the beginning of 2010, a case was encountered in the work, that is, a large-scale synthetic gas compressor, the unit was strongly vibrated during operation, and the machine could not operate normally. The equipment fault diagnosis technology is used to judge the unit failure by performing spectrum analysis on the phenomenon that the shaft vibration of the syngas compressor suddenly becomes large. The reason for the vibration is that the rotor impeller enters the broken filter net, causing the rotor to unbalance and block the impeller flow passage. The impeller flow rate is reduced to cause noise and surge. According to this, the correct maintenance plan is adopted to solve the vibration noise and surge problem of the unit, avoiding major damage accidents that may occur in the equipment, reducing the unnecessary downtime maintenance or repair time of about 3 to 5 days, and avoiding about 1.5 million yuan. Accessories purchase costs.

1 Unit overview

The compressor unit is a 100,000 t methanol project unit synthesis gas compressor designed by a chemical plant in Hebei. It is a model produced by Shenyang Blower Factory with a model of 3BCL459. The compressor consists of one cylinder, three stages and nine stages (one stage four and two stages). The fourth stage and the circulating stage are first. The compressor and the prime mover are connected by a diaphragm coupling. The compressor, the transmission and the motor are mounted on the same steel base. The whole unit is lubricated by the combined oil station for oil supply. The end seal uses the dry gas seal of Sichuan Nisshin Seal Co., Ltd., and the prime mover uses the 4200 kW motor of Jiamusi Motor Factory.

1. 1 unit parameters

2 unit vibration test program

The measuring instrument used is the SKF data collector, model CMXA70. The analysis software is the SKF data acquisition analyzer kit and the ptitudeAnalyst analysis software. The entire measurement system consists of sensors, data collectors, preventive maintenance software and computers installed on the machine. The measurement method consists of an absolute vibration test method and a relative test method.

SKF's application prevention and maintenance software provides management of the measurement point database, patrol path setting, loading the inspection path into the data collector, and the data collector returns the measured data back to the computer. According to the measured data, it processes, analyzes and compares the trend analysis and forecast of the data status, and uses the expert system to diagnose the faulty equipment. The vibration measuring point arrangement is schematically shown, and H, V, and A represent horizontal, vertical, and axial directions, respectively.

Vibration measurement point layout diagram 3 vibration cause analysis

3. 1 Fault characteristics

Since the syngas compressor was started in June 2006, it has been operating normally with a vibration value of 28 μm. On February 15, 2010, the amplitude of the north-south tile of the gas compressor suddenly increased to 90 μm (the alarm value of the machine is 75 μm, shutdown) The value is 120 μm). The load reduction measures were taken at random, and the vibration value was reduced to 60 μm. Through the vibration measurement and analysis of various parts of the unit, it was found that the maximum point of the unit vibration was at the level of the compressor. Under different loads, the vibration value of each point does not change significantly with the load rise and fall. The bearing housing and vibration amplitude of the compressor.

For the absolute spectrum of the compressor housing H1 on February 15th, it can be seen from the spectrum diagram that the power frequency of the compressor (211Hz) is 25mm/s. There are components on the 3rd, 5th, 7th, 9th and 11th frequency. . The power frequency component accounts for 70% of the pass frequency, and the other components are 30%. Vibration spectrum of bearing housing 1H during abnormality of synthetic compressor

3. 2 Troubleshooting

According to the above vibration characteristics and the characteristics of the vibration spectrum, the following conclusions are drawn: 1 Since the rotor has been running smoothly and the process system is not overloaded, the possibility of bending the rotor shaft is small.

2 Since the vibration of the compressor is suddenly increased, accompanied by noise and surge, the possibility of the impeller being blocked by the foreign matter in the rotor impeller is very large, or the impeller is damaged. 3 Since there are vibration components on the odd multiples, it is possible to judge problems on the impeller and the blades. It is best to judge the cause 2 by actual experience and the above data. The main reason for judging the vibration of the synthetic gas compressor is that the rotor dynamic balance damages the impeller blockage and causes surge and noise due to foreign matter in the impeller flow path.

3. 3 Disintegration unit inspection

1 During the shutdown inspection, check the rotor impeller and the inside of the diffuser and other flow passages. It is found that metal mesh and metal screws are found in the impeller flow passage in the end impeller flow passage of the rotor. The analysis was performed because the filter in the compressor terminal caused the filter to have no fixed position due to design problems, causing the entire filter to be drawn into the compressor terminal inlet. After the filter and bolt are damaged, they are sucked into the impeller.

3. 4 processing

Remove the filter and bolts from the rotor impeller. As a result of the inspection, the impeller blades were not damaged or deformed, and no dynamic balancing treatment was performed. Redesign the filter to increase the strength of the internal skeleton of the filter. The repaired synthetic compressor was started running well on March 10, 2010. The vibration spectrum of the bearing of the synthetic gas compressor shows that the negative value of the power frequency is reduced from 25mm/s to 5mm/s before parking, and the vibration of the synthetic compressor shaft is reduced from 90μm to 28μm. The vibration and treatment of the synthetic gas compressor are obtained. It was a success. The vibration spectrum of the bearing housing 1H after the repair of the synthetic gas compressor.

4 Conclusion

The operation of the synthetic compressor unit after maintenance has been stable. The case of the syngas compressor unit is a good example. The use of equipment fault diagnosis technology for preventive maintenance of the unit can reduce accident parking, reduce maintenance costs, ensure safe production, and save energy.

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