A single rotor system of a rotating machine is typically supported by two bearings, a plurality of rotor systems, typically coupled by a coupling. Therefore, the rotor misalignment has two meanings: one is that the rotor journal is not centered with the bearings at both ends; the other is that the coupling between the rotor and the rotor is misaligned, mainly reflected in the misalignment of the coupling. Some machines, such as turbine generators, meet the requirements when the rotor is not in operation. Once the temperature rises during operation, heat may be misaligned. In addition, the uneven foundation sinking, the failure of the pin hole wear of the coupling can also cause misalignment.
There are several main reasons for common rotor misalignment failures:
a. Design reasons. The calculation of the amount of thermal expansion under the working condition is not accurate, and the influence of the medium pressure and the change of the vacuum degree on the casing is not accurate.
b. Manufacturing, processing reasons. Uneven material, resulting in uneven thermal expansion; processing deviations and defects.
c. Installation and maintenance. Cold alignment data does not meet the requirements; maintenance failure causes thermal expansion to be blocked; poor insulation of the casing and uneven thermal expansion.
d. Operational operation. Overload operation; media temperature deviates from the design value.
e. The state is degraded. The base of the unit or the foundation is unevenly settled; the base slide is rusted, the thermal expansion is blocked; and the casing is deformed.
2Compressor rotor misalignment analysis and processing
2.1 propylene compressor rotor misalignment
The model of propylene compressor is 3MCl456, the motor power is 2500kW, the speed is 2985r/min, the speed increase box model is HS35, the speed ratio is 3.059, and the speed is n1/n2=9131/2985.
The vibration of the compressor near the speed increase box side is large, and the maximum value of the double vibration value of the driven shaft power frequency is 3.7mm/s. From the data analysis point of view, the driven shaft and the compressor rotor on the speed increase box side The alignment is not good. In the measurement of the raw data in the speed increase box, the meshing gap of the large and small gears (including the contact point of the tooth width and the tooth height direction) and the bearing clearance (bearing radial direction, axial clearance) are found. The center distance of the large and small gear shafts and the parallelism equivalents do not meet the requirements, which results in poor alignment and strong vibration. Preliminary analysis and judgment, the teeth may be defective, and the repair is more difficult. When the system is shut down for maintenance, it is decided to replace one speed increase box according to the operation condition of the speed increase box and the production conditions. The geometrical dimensions of the new speedbox were re-tested and installed one by one, and the internal and large pinion meshing gaps of the gearbox were measured, and the bearing clearance of each part was measured. After meeting the technical requirements, the replacement work was carried out. After measurement, The alignment between the speed increasing box and the compressor and the motor basically meets the specified requirements. After monitoring, the bearing temperature of the speed increasing box is less than 75, the vibration of the box is not more than 0.03 mm, and there is no abnormality.
After the gearbox is replaced, the size gear meshing clearance/mm0.25~0.330.380.28 meshing tooth height contact point/%60>55>70 meshing tooth width contact point/%80>70>80 pinion support bearing radial clearance/ Mm0.20~0.250.350.20 pinion support bearing axial clearance / mm0.30~0.500.550.40 large gear support bearing radial clearance / mm0.30~0.3750.300.32 large gear support bearing axial clearance / mm0.20~0.300 .350.28 Radial bearing and bearing gland interference / mm0.03~0.050.010.04 Increase the speed of the box side horizontal vibration / mm! The s-1 motorized part provides the horizontal displacement value of the 5.492.12 speed-increasing box side. The motorized part is provided. 756 It can be seen from Table 1 that before the gearbox is replaced, the meshing surface of the large and small gears is in poor contact, the radial direction of the bearing, and the axial direction. The large gap causes the shaft to have large runout and turbulence in the vertical and horizontal directions, which affects the alignment between the shaft and the shaft, which in turn causes strong vibration of the unit. After the gearbox is replaced, the meshing clearance of the large and small gears is reduced from 0.38mm to 0.28mm, and the contact points in the tooth height and tooth width direction are 70% and 80%. The radial and axial clearance of the bearing are also adjusted from the original data. Within the standard range, the vibration of the entire gearbox has been significantly improved.
After the internal data of the gearbox was measured, the compressor shaft and pinion shaft side of the unit, the motor shaft and the large gear shaft side were realigned. It was found that the vertical and horizontal alignment were improved before the maintenance. Taking the compressor shaft and pinion shaft centering as an example (the head is on the pinion shaft), the upper and lower values ​​of the vertical direction are 0, 0.29 mm before and after the inspection (the data measured after the inspection in brackets). 0, 0.21 mm), three dimensions are 0.14, 0.15 mm (0.09, 0.10 mm); the upper and lower values ​​in the horizontal direction are 0, 0.01 mm (0, -0.01 mm), respectively, and the three-dimensional values ​​are 0.06, -0.05 mm, respectively. (0.04, -0.03mm). Its standard reference value: the upper and lower values ​​in the vertical direction are 0, 0.162mm, and the three-dimensional values ​​are all 0.081mm; the upper and lower values ​​in the horizontal direction are all 0, and the three-dimensional values ​​are 0.038, -0.038mm respectively. Out, the alignment data after inspection is closer to the standard reference value than before the maintenance. In addition, the alignment data between the large gear shaft and the motor shaft is close to the standard reference value after the inspection. The solution to this problem has ensured the normal operation of the equipment.
2.2 Combined cycle compressor rotor misalignment
The combined cycle compressor is driven by a steam turbine, model 452B2, motor power is 3281kW, and the speed is 11465r/min. In a shutdown maintenance, it is decided to replace the turbine rotor and impeller group for the operation of the equipment for many years. After the successful completion of the replacement work, the compressor and the steam turbine should be centered, but the adjustments are not up to the technical requirements. After analysis, there may be two reasons:
a. When the normal equipment is deactivated, the piping system undergoes a stress change caused by thermal expansion and contraction. These stresses act on the nozzle connected to the compressor, especially at the tee and elbow, and the load is too large. When it causes a large deformation on the equipment pipeline, it affects the alignment of the equipment.
b. During the installation and piping process of the compressor, the internal stress remaining in the structural member due to welding or other processes, the residual stress of the compressor pinches the interface pipe of the compressor, so that the centering value cannot meet the requirements.
After research and discussion, it was decided that the maintenance personnel should perform stress-free alignment on the compressor, first release the stress in the pipeline, cut off the inlet and outlet pipes connected to the compressor, and make the compressor in a free state, and then perform centering. When the alignment data meets the technical standards, it is re-taken, and at the same time, the dial gauge is used to observe the change and direction of the alignment data during the takeover until all the pipeline connections are completed. Finally, the data in the middle meets the requirements, and the unit drives successfully once.
3 end
Through the overhaul of the propylene compressor and the combined compressor, the problem of the misalignment of the unit is solved, and the hidden danger hidden behind the appearance is also solved. After condition monitoring, the two units are in good operating condition and have always maintained stable and stable production.
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