Vibration Fault Analysis and Maintenance of Large Long-axis Deep Well Pump

Through the vibration failure analysis of large deep well pumps and various causes of vibration, a method for easy judgment of the motor and pump at the site is proposed.

Pangang has a large deep well pumping station on the upper reaches of the Jinsha River. The pumping station consists of two deep wells with an inner diameter of 18m and a depth of 31m. The Jinsha River water entered the deep well through four Dg1200 pipes, and the upper part of the deep well was equipped with 20 sets of 30JD-19x3 sand control deep well pumps on the reinforced concrete frame beam with the cross section of 1450mm×410mm. We have made some explorations on the reasons for the vibration during the long installation and maintenance.

First, the relevant technical performance parameters of the deep well pump Model: 30JD-19x3, three-stage impeller flow: 1450m3 / h drive shaft length: 24.94m, a total of 9 shaft pump shaft diameter: 080mm pump shaft material: 40Cr speed: 985r / min thrust tile Oil temperature: <50°C Cooling water pressure: 0.8MPa Inner diameter of water pipe: 500mm Head: 80m Rubber bearing Lubricating medium: Clear water without motor When single machine weight: 14t vertical motor model JKL15-6 Rated power: 500kW Rated voltage: 6000V rated Current: 60A motor rotor moment of inertia: 58kg·m2 Motor weight: 4t motor and pump body vertical and horizontal direction allowable amplitude value: <0.l0mm This deep well pump requires water quality sand content is not more than 0.1%, particle size is not more than 0.2mm, And the first stage impeller of the pump should be immersed in the water level below lm. At present, during the July and August floods, the sediment concentration of the Jinsha River in the deep well pump has been nearly 20%.
Second, the vibration fault is judged. The pump and the motor are vibrating during operation. When there are conditions, first disconnect the coupling between the two, analyze whether the vibration source is from the pump or the motor, and carefully check the vertical motor base and Whether the connection bolts of the pump are tightened and the level of the installation is not good. 1. Motor vibration source and discrimination

(1) Whether the rotor working speed is close to the critical speed. It is possible to generate resonance by calculating whether the torsional stiffness of the motor shaft and the motor torsional vibration frequency are close to the critical speed of the motor, the pump angular frequency, and the grid frequency. Especially for the motor used for the first time, when a vibration failure occurs, the analysis and calculation are performed. The operating speed of the rotor of the motor should be at least 25% below the critical speed or about 40% above the critical speed. In the analysis, it is also considered that the mass of the motor rotor cannot be simplified into a concentrated mass condition, but distributed along the rotating shaft. Therefore, the critical critical speeds such as the second and third orders should be analyzed when analyzing the critical speed.

(2) Unbalance of the rotor of the motor. The imbalance of the rotor of the motor is the most important and common cause of vibration, such as: 17#, 19# motor, the vibration speed of the motor is 9.8-l0mm/s measured by the speed vibrometer (displacement meter), compared with the vibration speed standard of IS02372. Class III machinery should be less than 4.5mm/s, and in the state of 9.8-l0mm/s, the amplitude of the motor measured by the vibrometer is 0.30mm. In order to find out the imbalance of the rotor of the motor, we made two steel frames on the site to erect two parallel rails (note that the steel frame should have sufficient rigidity), the upper surface of the rail is treated as smooth and clean, and the rail is matched with the level. The surface is adjusted horizontally and fixed. During the inspection, the rotor of the motor is placed on two rails, and the rotor inlet metering pump is pushed by hand to roll back and forth several times, and each time it is still, it is marked under the rotor. Stick the viscous object to the symmetrical point of the weight position, and then rotate the rotor several times until the rotor can stop at any position. Confirm that the rotor of the motor has reached static equilibrium. Replace the sticker with the equivalent mass to complete the balance of the motor rotor. If the above method still cannot solve the problem, it is necessary to check the rotor of the motor. After the above two motors were added with a balance weight of 45-5 g on the rotor side, the amplitude value was reduced to 0.05 mm, and the vibration velocity value measured by a displacement meter was about 2.1 mm/s.

(3) For motors that have been used for a period of time, the vibration causes to check whether the bearing clearance is too large, whether the shaft seat fixing screws are loose, whether the shaft is worn and bent, or a part of the windings are short-circuited, the air gap is uneven, and the rotor and The unevenness of the annular gap between the stators is generally not more than 10%. It is particularly noteworthy that when the motor amplitude value is close to the standard value, it is considered that it is still within the acceptable range. After the load is loaded, the motor amplitude value will exceed the standard. This is because the vibration factors of the entire deep well pump transmission system are mutually affected. And the result of the joint action. 2. Pump body vibration source and judgment

(1) Vibration caused by pump installation and assembly deviation. The level difference between the pump body and the thrust pad after installation and the verticality of the water pipe will cause the vibration of the pump body, and the three control values ​​are also related. After the pump body is installed, the total length of the water pipe and the pump head (excluding the filter net) is 26m, which are all suspended. If the vertical deviation of the water pipe is too large, the pump and the shaft will cause severe vibrations such as the pipe and the shaft. . If the verticality of the water pipe is too large, the alternating stress will be generated during the operation of the pump, causing the breakage of the water pipe. After the deep well pump is assembled, the water pipe is within the total length, and the verticality error should be controlled at 2 mm. The vertical and horizontal horizontal error of the pump is <0.05/l000mm. Pump head