tailieunhanh - Mechanical Engineering-Tribology In Machine Design Episode 12

Tham khảo tài liệu 'mechanical engineering-tribology in machine design episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 262 Tribology in machine design tapered roller-bearings and spherical roller-bearings are generally limited to less than X 106 DN and X 106 DN respectively. These limits are basically those stated in bearing manufacturers catalogues. The selection of a type or a classification of grease by both consistency and type of thickener is based on the temperatures speeds and pressures to which the bearings are to be exposed. For most applications the rolling element bearing manufacturer can recommend the type of grease and in some cases can supply bearings prelubricated with the recommended grease. Although in many cases a piece of equipment with grease lubricated ball- or roller-bearings may be described as sealed for life or lubricated for life it should not be assumed that grease lubricated bearings have infinite grease life. It may only imply that that piece of equipment has a useful life less than that of the grease lubricated bearing. On the contrary grease in an operating bearing has a finite life which may be less than the calculated fatigue life of the bearing. Grease life is limited by evaporation degradation and leakage of the fluid from the grease. To eliminate failure of the bearing due to inadequate lubrication or a lack of grease periodic relubrication should take place. The period of relubrication is generally based on experience with known or similar system. An equation estimating grease life in ball-bearings in electric motors is based on the compilation of life tests on many sizes of bearings. Factors in the equation usually account for the type of grease size of bearing temperature speed and load. For more information on grease life estimation the reader is referred to ESDU -78032. Figure . Jet lubrication For rolling-element bearing applications where speeds are too high for grease or simple splash lubrication jet lubrication is frequently used to lubricate and control bearing temperature by removing generated heat. In jet lubrication

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