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| home : industrial : tech help |
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| What are some bearing removal practices? Be certain to use extreme care when removing Timken® bearings. Careful removal protects the bearings, shafts, and housings, which are vulnerable to damage. The best way to remove a bearing is to use a bearing puller or a hydraulic pneumatic press. Commercially available pullers include conventional hand-operated pullers and hydraulic pullers. Special puller designs are also available. In operating the puller, it is important to remember that the puller, located against the back face of the cone, must not contact the cage. To be sure that this doesn’t occur, rotate the cage by hand after the puller is in position. The cage should rotate freely when the puller is in position. Hydraulic pullers are used to apply more force. When the shaft shoulder extends as high as the cone rib outside diameter, special pullers can be used to remove the cone. Caution: If the bearing is to be reused or returned for repair, don’t use heat from a torch. Extreme heat will alter the bearing hardness and metallurgical structure resulting in irreparable damage to the bearing. Never use hardened drift, brass bar or center punch to remove the cone. They both damage the bearing. Also, brass bars usually chip, resulting in brass fragments getting into the bearing and causing damage. How and why are bearings rated? To aid in the correct selection of bearings that will handle designate loads, Timken publishes dynamic “catalog ratings” for all its tapered roller bearings. Under controlled laboratory conditions, specific bearings parts are tested to verify the load each type of bearing will withstand for a standardized 90,000,000 revolutions at 5000 revolutions per minute (RPM). At this speed, a bearing will reach the desired number of test revolutions in 3,000 hours. Therefore, the catalog rating lists load capacities in pounds, or Newtons, for a life of 3,000 hours. The term applied to the lifetime of a bearing is “fatigue life.” When a bearing is rotated faster than 500 RPM, it will reach 90,000,000 revolutions sooner, and its life in hours will obviously be shorter. Because of this rotation speed factor, coupled with operating environment and the statistical rations of contact fatigue, not every bearing will reach the life stated in the catalog. Some will require replacement sooner and some will last longer. |
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