Three screw pump shaft and shaft clearance lock reason
Three screw pump shaft and shaft clearance lock reason, the reason analysis According to the work of the sliding bearing, the general three screw pump bushing hole and the shaft is a gap fit, the size of the parts on the shaft diameter and bore diameter deviation , It is generally determined by the average working temperature of 20 ℃ to ensure that there is a reasonable gap between the shaft and the bushing hole. Affect the sliding bearing overheating failure of many factors in the bearing structure design is reasonable, the material used in the right circumstances, the main bearing overheating is the radial clearance size of the improper assembly and improper use caused. Radial clearance of sliding bearing bearing overheating failure, the radial clearance of the sliding bearing Δ is the difference between the diameter of the bearing hole and the journal diameter, the sliding bearing to leave a certain radial clearance, its role is as follows: Is to achieve shaft and bearing Activities at least the conditions of the joint; is to ensure the operation of the shaft accuracy assurance; is the formation of an important condition for liquid lubrication. Therefore, the radial clearance of plain bearings is very important, too large or too small are extremely harmful. The gap is too small, it is difficult to form a lubricating oil film, the friction heat is not easy to be taken away, the bearing overheating, serious "will hold the shaft"; gap is too large, the oil film is difficult to form, will reduce the machine running accuracy, will produce severe vibration and noise , And even lead to tile accidents. Second, the radial clearance of the sliding bearing to determine the technical performance of the screw pump: journal speed n = 2950r / min, journal diameter d = 30mm; motor for synchronous motor, oil residue, the bearing material is tin-based copper. Theoretical Radial Clearance of Plain Bearings Radial Clearance of Slewing Bearing Δ = K · d. Where: K --- high-precision bearing factor, from the "Mechanical Design Manual" found K = 0.0008. d --- journal diameter, d = 30mm. Substitution: Δ = 0.02mm from the "Mechanical Design Manual" found that the maximum gap Δmax = 0.10mm. The original sleeve measurements, data and location: to measure the shaft diameter, the corresponding position size data: Shaft diameter 1: 29.99mm29.94mm29.90mm Shaft diameter 2: 29.92mm29.90mm29.90mm Sleeve 1: 30.01mm29.97mm29. 92mm Sleeve 2: 29.94mm29.92mm29.915mm The actual value of the radial clearance of the sliding bearing Maximum clearance: Active rod: 0.03mm Follower rod: 0.02mm. The bearing in the actual use of the process, due to the gap is too small, friction heat is not easy to be taken away, combined with oil as the media residue, more impurities, easy to enter the gap, the bearing overheating, serious "will be" axle " Watt phenomenon. Third, the prevention and improvement measures In order to prevent the bearing overheating failure, if the larger radial clearance adjustment, Δ = 0.03mm. At this time the bearing with the vice although the normal work, but its service life is greatly reduced, so in determining the radial bearing clearance, should ensure that the bearing under the premise of normal work to stay as small as possible. After the bearing assembly, the first grinding should try to run the good run-in specifications and test run, and then gradually load acceleration, the shaft and bearing surface with raised convex, and finally put into normal operation. Otherwise, even if the clearance is not too small, but because after the assembly without trial run, and put into normal operation, resulting in bearing overheating or even burning tile. In this regard, the radial clearance of the sliding bearing should be controlled at 0.10mm ~ 0.15mm. Radial clearance of bearing overheating and bearing life is greatly affected, so for the radial clearance, we must strictly control within a reasonable range. In determining the bearing radial clearance, to fully consider the factors that affect the radial clearance, in addition to considering the shaft diameter, speed, load and machine accuracy, but also consider the following points: a. Bearing material. Different bearing materials, different expansion coefficient, the gap is different. b. Shaft and bearing surface roughness. c. journal and bearing geometry and mutual position error (ie, roundness, cylindricity, coaxiality, etc.). d. bearing operating temperature. f. sudden changes in starting conditions. Fourth, the conclusion Different media and different speeds on the screw pump shaft clearance requirements are not the same. Through the above calculation and analysis, the best clearance data of the sleeve was obtained. Equipment to transform the normal operation of a year to verify that our analysis is feasible.
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