Manual technical repair of burned crankshaft of piston compressor

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A company's 6D32-250/320 type and H22(Ⅲ)--165/320 The compressor has been in operation for more than 30 years, and the crankshaft is severely worn. The conicity, ovality, and parallelism of the crankshaft neck have seriously exceeded tolerances. Two oil-cut and shaft-burning accidents have occurred in succession. Not only has the journal been thinned, but the surface of the burned crankshaft is also covered with grooves and a crack layer caused by high-temperature oxidation, which seriously affects the long-term, safe, and high-load operation of the compressor. The journal was repaired using manual techniques. Preparation: 1. Provide technical briefing and safety education to participants. 2. Tools and materials: 150mm square frame level with an accuracy of 0.02mm/m, micrometer (matched with the journal), feeler gauge, 150~300 vernier caliper, tire tool (three pieces of crankshaft journal tire grinding), two sets of hardwood polishing curtains, Various files, double-sided oilstones, electric polishers, dial indicators and magnetic table bases, knife-edge rulers and various sandpapers, polishing powder, white canvas, white cloth, kerosene, machine cleaning cloth, ∮6 steel bars, 0.7mm fuses and other materials. Shaft repair steps: 1. Remove the crankcase upper cover, connecting rods (H22 (III) type two adjacent ones need to be completely removed), main bearing upper cover, and plug the oil holes on the main and crank journals with cloth strips. 2. Measurement: Divide the crankshaft neck into 4 to 5 sections, and use a measuring point every 45° on the circumference to measure the diameter of the four points. Measure the level of the adjacent main journal and record it. Using the main journal as the benchmark, use a level to verify the crankshaft journal and measure the level difference between the vertical and horizontal positions. Draw a multi-section crankshaft neck cross-section according to the on-site crankshaft journal wear condition, round it up according to the cross-section and use it as a cross-section construction drawing, and determine the filing position and filing amount through mutual comparison. 3. Roughing stage: Large-area filing is based on the measured construction drawings and comparison data of each measurement. Its purpose is to eliminate convex edges, make the crankshaft neck smooth, and basically find roundness and leveling. It does not require smoothness, only straightness. At this stage, repeated measurements and manual filing (using a grinder and file) are used to repair the maximum wear datum plane with reference to the level of the adjacent shaft diameter. At this location, start filing the shaft with a tire tool grinding point. The amount of filing is until the maximum wear point is just flat, and it is repaired in both directions until it is enclosed. When measured with a 150mm steel ruler, the transmittance is ≤15%, the transmittance gap is ≤0.10mm, and the journal is basically formed. 4. Fine filing stage: When the grinding points evenly cover more than 70% of the journal, and there are no large areas (∮20~25 mm) of depressions, it is transferred to the fine-grinding stage. In addition to the rough filing stage method, three types of fetal membranes with different inner diameters are also used to measure, grind, and file from the datum plane in both forward and reverse directions. Measure the data while trimming. If there are any ridges, they must be trimmed. ； It is required that the contact area in each axial direction reaches more than 85%, the surface smoothness reaches more than ▽4, and the parallelism, levelness and ovality and taper of the journal are ensured. Pay attention to grinding the R on both sides of the journal at the same time (R=20 mm). At this stage, the journal has been finalized. 5. Coarse throwing: Use emery cloth to polish the crankshaft to ▽4 or above. At this time, pay attention to the ovality, conicity and levelness of the journal. 6. Fine polishing: After the crankshaft neck is finalized, its ovality, taper, parallelism and levelness meet the technical requirements. At this time, the connecting rod and thickened shim are turned to check the matching size. After the identification is correct, the finish can be treated with whetstone, emery cloth, polishing metallographic emery cloth, polishing powder and other means. The final smoothness reaches ▽7~8 or above, and the two sides R are polished with thick hemp rope and polishing powder. 7. Measure the final crankshaft journal diameter and level. 8. Clean the fuselage, take out the cloth strips, blow through the oil holes, and install thickened tiles. 9. Test drive. Technical requirements: 1. Crankshaft levelness ≤ 0.08 mm/m, journal ovality and conicity < 0.10 mm, parallelism to the main axis ≤ 0.02mm/100mm, conicity ≤ 0.015mm/100mm, ovality ≤ 0.01mm/100mm. 　2. The crankshaft difference is measured at four positions, up, down, left and right, at a distance of 440 from the crankshaft diameter center.: The upper and lower deviation is ≤0.04 mm and the left and right deviation is ≤0.02 mm. 　3. The connecting rod clearance is 0.25~0.35 mm, and the string measurement is 0.35~0.75 mm on each side. 　4. More than 80% of the connecting rod slingback and the connecting rod body are evenly contacted, more than 70% of the babbitt alloy and the journal are evenly contacted, and there should be no obvious wear marks on the working surface. 5. There should be no grooves, scratches or roughening on the surface of each journal. If there are any, they must be ground and removed. Things to note: ⑴　During the rough repair stage, the original journal must be retained as much as possible, and the amount of repair must not be too large. This is to ensure that the strength of the crankshaft is within the allowable range and to reduce the workload of repairing the shaft. ⑵　During the rough repair stage, ensure that the crankshaft journal and the main journal are at the same level. ⑶　When there is a conflict between the horizontal and diameter dimensions, the diameter should be given priority and the horizontal dimension should be taken into consideration. ⑷　After repairing the shaft, don’t forget to take out the oil hole cloth strip ； Before installation, the crankshaft and connecting rod oil holes should be blown through, and no iron pins should remain. ⑸　The shoulder R must be repaired synchronously with the journal and thrown above ▽7. ⑹　When repairing the crankshaft journal, ensure that the piston stroke remains unchanged. This should be checked by the small change in cylinder clearance pressure.