Application of condition monitoring technology on air compressor

State monitoring and diagnostic technology technical version of the state monitoring technology application in air compressors Su Zhizhong Dai Fengtao \ Zhu Xiongxin 2, Cheng Jun 2, Ai Heti Jiang Jiang 3 (L. Dushanzi Petrochemical Company Research Institute of Equipment; 2. Dushanzi Petrochemical Company ethylene plant fitter workshop; 3. Dushanzi Petrochemical Company ethylene plant air separation workshop, Xinjiang Karamay 83360 () preventive maintenance, to ensure smooth production.

The air separation plant of a factory is responsible for the whole plant gas and nitrogen supply. The two 40OOOmYh air compressors are the core equipment of the two air separation plants. They are the company-level key units and are equipped with the S8000 online monitoring system. Since the implementation of the state monitoring technology on the S8000 online monitoring system, preventive maintenance of the air compressor unit has been realized. The following two successful cases illustrate the application of condition monitoring and fault diagnosis techniques in implementing preventive maintenance.

The unit is manufactured by Ingersoll Rand, and the eddy current displacement sensor of the two measuring points of the gear type multi-axis compressor is installed at a 45° difference from the horizontal direction.

The speed of the stage is 12000r/min, the alarm value is 33|xm, the interlocking stop value is 38|xm. The second-level speed is 16668r/min, the alarm value is 29|xm, the interlocking stop value is 34|xm. The third-level speed is 22500r/min, and the alarm value is 25| Xm, chain shutdown value 30|xm. Since the start of June 2009, the vibration values ​​of the two X and F measuring points have a slow upward trend, especially after March 20, 2010, the vibration value increases. Faster. The three-stage vibration trend chart is as shown. On June 8, 2009, the vibration value of the third-level A measuring point is 6.3|xm, and the vibration value of the third-level F measuring point is 7.6|xm. On March 20, 2010, the vibration value of the X measuring point is 17.6|xm. The vibration value of the point is 15.1|xm, and by May 24, 2010, the highest vibration value of the three-level X measurement point is 27.2|xm, and the F measurement point also reaches 25.2|xm, which has exceeded the alarm value 25| Xm, and there is still an upward trend.

In order to analyze the cause of the vibration increase of the unit, the S8000 online monitoring system is used to analyze the signal of the unit. Shown are the time domain waveform and spectrum contrast on May 27, 2010 at 21:11:55 and August 1st, 2008 at 22:46:07. . It can be seen from the comparison that the main component of the large vibration is 1 frequency. According to the characteristics of the slow creep of the vibration, it can be judged that the vibration is caused by the uneven scaling of the rotor, causing the rotor to be slowly fluctuating and unbalanced. The state monitoring and diagnostic technology reached the alarm value, and the vibration still has an upward trend. Therefore, the workshop decided to immediately carry out maintenance to avoid production accidents.

History teaching data two air points 1 * empty machine >> three 8LTS dynamic waveform W 1 air compressor waveform spectrum 010 May 29 air separation workshop on the air compressor to stop maintenance. It was found that the surface area of ​​the impeller, the diffuser and the casing was severely carbon and scale, and the air filter of the air compressor inlet had more dust.

In order to solve the vibration failure of the air compressor, the following measures are taken to avoid repeated failures after maintenance.

1 Replace the three-stage rotor. The replaced rotor is cleaned and descaled as a spare part.

Q uses steam to purge and descale the diffuser and the casing.

Q selects the inlet filter core with better quality and higher precision. If the domestic filter element is used, the non-woven fabric can be pre-filtered on the outside of the filter; the old filter cartridge in the self-cleaning filter is all updated, after replacement The filter resistance is significantly reduced, the filtration effect is improved, and the air compressor is inhaled.

(4 Check the source of the third-level scale. Check that the secondary heat exchanger has no internal leakage, the trap of the lower part of the secondary heat exchanger is abnormal, and the condensate cannot be discharged normally. So it is decided to remove the trap and use the hose to discharge the condensate. After the start-up operation check, it was found that the secondary heat exchanger drained the water pipe more.

1 After the air compressor is overhauled, the vibration is obviously reduced, and the three-stage vibration value is greatly reduced by about 15MI1V and kept at 1llpm. Through the state monitoring technology, the unit's operating condition is grasped in time, and the fault type, location, degree, etc. of the unit are accurately diagnosed. . Through monitoring information, reasonable arrangement of maintenance time and maintenance content, the failure of the third-stage vibration of the air compressor vibration was successfully solved.

2, 2 air compressor unit monitoring and operation management 2 air compressor and 1 air compressor structure is the same, on March 21, 2010, the first-order vibration suddenly rises, A measurement point rises from 13.2pm to 21.6|Jm, F measurement The point rises from 12.9|Jm to 22.4|Jm, which is close to the alarm value.

The reason for the sudden increase in vibration was that the shop was swaying.

Through the S8000 online monitoring and analysis system, the signals of the X and F measuring points are analyzed before and after the sloshing. The main frequencies in the spectrum are 1x, 2x, 3x, and the 3rd frequency is the most prominent. The spectrum is as shown. . Through spectrum analysis, it is believed that the appearance of 3 times frequency is mainly related to the connection mode between the rotor and the impeller. The rotor and the impeller are connected by an irregular triangular prism. This type of connection is prone to looseness and friction, and thus appears to be 3 times the frequency spectrum.

In order to analyze the changes in the spectral structure before and after the vibration mutation, the time domain waveforms and spectrograms of March 25, 2010, 01:57:04 and March 1, 2010, 10:57:04 were compared and analyzed. By comparison, it is found that the cause of the vibration rise is mainly caused by a 3 times increase. The spectrum comparison chart before and after the vibration mutation is as shown. The reason why the 3 times frequency rises is that the motor suddenly powers off when the workshop suddenly slams, causing the loose connection between the compressor rotor and the impeller, so that the vibration suddenly rises.

3. Guaranteed transportation measures After the vibration of the air compressor suddenly rises close to the alarm value, the vibration value is stable, and no large fluctuations and sudden changes occur. It is recommended that the compressor continue to operate, but the operation is kept smooth and the load cannot be large. Change, prevent the occurrence of slamming accidents, avoid fluctuations, and cause vibration to rise again. In terms of condition monitoring, strengthen the condition monitoring of the unit and pay close attention to the operating conditions of the air compressor and the trend of vibration changes.

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