Maintenance of parallel shaft transmissions

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Maintenance of parallel shaft gearboxes are widely used in turbine compression units driven by electric motors or steam turbines. The technical requirements for the maintenance of such gearboxes include: 1. The levelness of the gearbox; 2. The parallelism of the gear pairs; 3. The gear meshing clearance; 4. The center distance between the gear pairs; 5. The meshing zone of the gear pairs; 6. The clearance of the sliding bearings. Points to note during the maintenance and assembly of gearboxes: 1. Due to the compact design and construction of these gearboxes, it is not possible to measure the center distance between the gear pairs using an inner diameter micrometer or an outer diameter micrometer during on-site maintenance； Using a vernier caliper with a length of 500 mm or more results in significant measurement errors; the obtained values have little to no practical value or usefulness. In particular, it is not possible to determine the parallelism of the two gear shafts while simultaneously measuring the center distance between the gear pairs. 2. During maintenance and assembly, when manual adjustment is used to ensure the parallelism of the two gear shafts (in both horizontal and vertical directions), adjusting this parallelism has an impact on a series of parameters such as the center distance and the meshing clearance – \"changing one thing affects the whole system.\" 3. During gear transmission, in order to create a lubricating oil film between the meshing tooth profiles and prevent the gears from heating up and expanding due to friction, a gap must be left between them – the meshing clearance. The presence of meshing clearance causes inter-tooth impacts, affecting the smoothness of gear transmission. Especially when the meshing clearance is large, it leads to a decrease in the overlap coefficient of the gear pair, a reduction in the accuracy of motion transmission, and increased wear; the obvious consequence in practice is increased noise from the transmission. Therefore, during maintenance, it is necessary to formulate a treatment plan based on the information obtained from checking and measuring gear meshing, in order to prevent problems resulting from excessive meshing clearance. 4. Place a wire at a distance of about 20 mm from the edge of each of the two end faces of the gear, and use the lead compression method to measure the meshing clearance of the gear pair. If the meshing clearance values at both locations meet the assembly requirements and the difference is ≤0.02 mm, it can be concluded that the center distance of the gear pair is also correct. When checking the meshing clearance of a gear pair, a dial indicator can be used for measurement. 5. When measuring the meshing clearance of a gear pair using the lead pressure method, the tip clearance (or root clearance) of the gear teeth is also determined; using the tip clearance allows for an easy and accurate assessment of the parallelism and center distance of the gear pair. 6. The center distance and mesh clearance of cylindrical helical gears change as the helix angle varies. Below is a case study on dealing with a large meshing clearance in gear pairs; colleagues are invited to refer to it and provide feedback. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml/wps9659.tmp.png