Cause Analysis of Vibration Failure of Centrifugal Air Compressor

Cause Analysis of Vibration Failure of Chemical Machinery Centrifugal Air Compressor Li Zhenwei* (China National Petroleum Corporation Liaoyang Petrochemical Company Power Plant) The air separation unit of a company has the air compressor of model DH4540 produced by Shenyang Blower Group Co., Ltd. The table is used as a raw material air compressor for the air separation unit. The machine adopts four-stage compression. The synchronous motor drives the large gear through the gear sleeve coupling. The large gear drives the first and second low speed shafts and the third and fourth high speed shafts to rotate at high speed. The motor speed is 1495r/min and low speed. The shaft speed mode is forcedly lubricated by the oil supply system. The five tilting tiles are evenly distributed in the circumferential direction. The upper tile is 2 blocks and the lower tile is 3 blocks. The tile is made of steel. The inner hole is cast with bark alloy and used together with the adjustment pad. . Since the tilting pad can be deflected when the journal is out of the equilibrium position due to external disturbance, the tile can be automatically adjusted to the equilibrium position, so that the pressure of the oil film is always equal to the external load, and the direction is opposite and collinear, which is well eliminated. The factor of oil film oscillation occurs.

1The working principle of the centrifugal compressor DH4540 air compressor is driven by the synchronous motor through the gear sleeve coupling. The large gear drives the high-speed rotation of the first and second low-speed shafts and the third- and fourth-level high-speed shafts. Under the action of centrifugal force, the gas is Go to the diffuser behind the wheel. In the middle of the working wheel, a thin zone is formed, and the front gas enters the impeller from the intake portion in the middle of the working wheel. Since the working wheel rotates continuously, the gas can be continuously extracted, thereby maintaining the continuous flow of gas in the air compressor. The gas increases the pressure due to the centrifugal action, and leaves the working wheel at a high speed. The gas gradually decreases the speed through the diffuser, and the kinetic energy is converted into static pressure energy, which further increases the pressure and compresses.

2 The problem occurred in the operation of the compressor is caused by the automatic vibration of the high-speed shaft of the third and fourth-stage high-speed shafts (the vibration of the first and second-stage low-speed shafts is normal). The vibration of the compressor before the interlocking parking is shown. The vibration value of the three-stage high-speed shaft is obviously exceeding the standard, reaching 61.0 pm, which exceeds the three-stage high-speed shaft. Analysis of the causes of shaft vibration failure The air compressor has repeatedly experienced vibration over-standard phenomena in different situations. After analysis, the main reasons are as follows: a. Impeller fouling. The compressor was automatically stopped twice due to the vibration of the high-speed shaft of the third and fourth-stage high-speed shafts. It was found that the impellers of the third- and fourth-stage high-speed shafts were seriously fouled, and the compressor suction line, the interstage pipeline and the interstage gas cooler were corroded. More things. The two parts of the parking and maintenance are cleaned of various dirt, and the high and low speed shaft impellers are sandblasted and tested for dynamic balance. The installation process is carried out in strict accordance with the technical requirements, and it runs normally after being turned on.

* Li Zhenwei, male, born in November 970, engineer. Liaoyang City, Liaoning Province, 111003. Chemical machinery b. Tile damage. The vibration of the third and fourth-stage shafts is super high, and the shutdown inspection, the three-stage and four-stage bearing bushes are damaged, the babbitt alloy is detached, and the operation is normal after replacement.

c. Poor contact of the tile, the radial clearance of the bearing pad is not ideal. Due to the error of the processing precision of the tile, there is an error in the clearance value of each bearing bush, which cannot achieve the same consistency, so that the bearing with smaller clearance has higher requirements on lubrication, the oil temperature and oil pressure adjustment requirements are strict, and the phenomenon of oil accumulation is easy to occur. It has a great influence on the vibration.

d. Gear meshing and centering adjustment. The overall rotation of the compressor is driven by the gear mesh, so the requirements for gear meshing are very strict. During the overhaul process, the rotor center distance, tooth contact, tip clearance and flank clearance should be strictly adjusted. The alignment of the shaft has a great influence on the smooth running of the unit. In the inspection process, the centering correction is performed by the advanced laser alignment instrument to ensure the accuracy of the alignment.

e. The impact of other factors. The data acquisition of the unit is controlled by instrumentation. In actual operation, the unit parking phenomenon caused by the malfunction of the instrument control point also occurs from time to time. The main factors are the looseness of the fastening bolt of a fixed sensor, the friction between the sensor tip and the rotor main shaft, the oil between the sensor and the cable joint, and the outside. Environmental disturbances, etc., all of which affect the change in measured values.

4 Troubleshooting measures (Continued from page 772) Table 8 Process adjustment scheme Welding method Welding current Welding voltage Welding speed Protection gas Manual arc welding reduction 30% reduction 10% constant MIG welding increased by 10% unchanged 30% Automatic TIG welding increased by 2.5%. The third butt weld test plate weld metallographic action for the high-speed shaft vibration of the compressor: a. Thorough inspection and maintenance of the unit, including interstage cooler and interstage pipeline Pressure test, derusting, impeller descaling, rotor flaw detection and dynamic balance inspection are required to be qualified; b. check alignment, median, bearing clearance and bolt pre-tightening force meet relevant technical requirements; c. gear, impeller The accuracy and material of the rotor, bearing bush and seal are checked and the quality meets the requirements; d. The inspection process has confirmed and recorded in steps, strictly in accordance with the maintenance regulations; e. Lubricating oil quality is analyzed according to the regulations, lubricating oil is mild oil pressure Control within the scope of the process requirements; f. The operator carefully operates, carefully inspect, strictly control the parameters according to the sound operation rules, to avoid the compressor working point into the surge area; g.

After the conclusion of the 5th, the vibration values ​​of the third- and fourth-stage high-speed shafts of the unit are 14 and 16m respectively, and the operation is stable, meeting the production process requirements, and the effect is remarkable.

5 Conclusion and phase steel has been used more and more in the domestic petrochemical industry due to its good corrosion resistance. However, due to the lack of corresponding standards and basis, the conventional use and acceptance of dual-phase steel is only performed in accordance with the requirements of the welding process evaluation, and the corrosion resistance is often not evaluated. In this test, the materials were firstly inspected, and then the corrosion test was performed on the butt welds and the pipe joints of the pipe and tube sheets according to the actual corrosion conditions. Most corrosion tests were found to be unqualified due to the welding process. In this case, the welding process was adjusted. The final corrosion test was all qualified. At present, the batch of air coolers have been used in harsh conditions for more than two years, and the corrosion resistance is good. Through this test, it is considered that for the dual-phase steel sound setting, it is not only necessary to perform acceptance from the intensity of the sound of the sound, but the corrosion resistance of the sound should be strictly checked and accepted.

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