The application of slewing ring bearing for Harbour and shipyard cranes

      Slewing ring bearing is widely used in harbour crane and shipyard crane for slow-turning under heavy load. As the load situation for harbour crane slewing ring bearing and shipyard crane is relatively larger, three row roller slewing ring bearing can provide better performance comparing with other structure slewing ring bearing.

  In harbour crane and shipyard crane, slewing ring bearing serves as a joint between the upper structure and the undercarriage, providing a means of 360-degree rotation.

   Since the bearing is so critical, careful maintenance is necessary. More than 96% of slewing ring bearing failures are due to surface-originated lubrication problems, contamination, overloading, and improper installation and mounting fits. These surface failures occur much earlier than classical fatigue failures and are less predictable.

Bearing lubrication

 The bearing should be lubricated at regular intervals, with a heavy-duty, extreme-pressure grease. Slowly rotating equipment or oscillating applications, such as backhoes, excavators, and cranes, should be relubricated about every 100 hours of operation. More frequent lubrication—every day or every eight hours—may be needed on rapidly moving or continuously rotating equipment such as trenchers and boring machines.

  While adding grease, the bearings should be rotated to spread the grease throughout, with enough grease added to purge the old grease out through the seals. This procedure helps to clean out contamination.

  Over long periods of time, grease tends to dry out and condensation can form within a bearing. Grease should therefore be introduced at least every six months, whether the equipment is operating or idle.

Gear lubrication

  Most large bearings incorporate gear teeth and the gear lubrication requirements are not the same as for the bearing. Because the meshing action of the teeth tends to squeeze out lubricant, the gears should be lubricated every eight hours on slow or intermittently rotating equipment, and more often on rapidly or continuously rotating equipment. Small amounts of grease should be introduced at the point of mesh between the gear and pinion.

Bolts

  A check of bolt torque should be part of any routine maintenance procedure. The frequency of these checks depends on severity of service. Vibration and shock tend to loosen bolts, so periodic torque checks will ensure that the proper preload level is maintained.

  Mounting bolts should be torqued to the proper level and checked periodically to ensure proper pre-tension. Improperly pre-tensioned bolts can fail, causing damage to equipment and, more important, injuries to workers.

  Additionally, tightened bolts tend to creep or elongate over a period of time, which reduces preload. Elevated temperatures will also increase bolt creep and this factor should be considered in developing a torque-check schedule.

Seals

 Seals on the bearing should be visually inspected periodically to be sure they are fully intact. Insignificant as these seals may seem, they aid considerably in the prevention of bearing raceway contamination.

 Xuzhou Wanda Slewing Bearing Co.,Ltd. is a slewing bearing manufacturer specializing in standard and non-standard slewing bearing.Over the years, we keep supplying high quality product & good service to customers of crane. 

  We have strict quality control system in our own factory,meanwhile, we have passed ISO9001:2008 Quality System Certification, certificates of Bureau Veritas and China Classification Society . 

         Besides, we have advanced production equipment and technology to meet high precision of slewing bearing. And we have professional engineers for slewing ring bearing selection.