Water lubricated stern bearing and repair damaged - bearing knowledge

Open water lubricated stern bearing because of no pollution, and simple manufacturing, maintenance etc, and with the development of material science, many new bearing materials with durable, low coefficient of friction is gradually applied in water lubricated stern bearing, so still have broad application prospects. But due to large water lubricated stern bearing assembly clearance, and ship operators when immersed in seawater, the affected by external factors, the distribution scale increased as the stern bearing damage is often happened. 'Liyang' built by the jiangnan shipyard in 1971, the original all belong to Shanghai ocean shipping company. Design for the machine with the long axis, including four stern shaft, intermediate shaft and thrust. Each intermediate each have an intermediate bearing and propeller diameter of 5. 32 m, host speed 105 RPM. Stern bearing originally common wood, USES the water lubrication, sealing packing for butter packing. At a dock repair, take out stern shaft after examination revealed extensive damage, stern bearing lower half surface bearing the actual gap of more than 10 mm, stern shaft surface wear is in good condition. Damage reasons cause analysis stern bearing damage in addition to the normal wear due to long-term operation, mainly includes shafting vibration, shafting alignment and bearing design is not reasonable, etc. Shafting vibration of shafting vibration in general can be divided into the shafting torsional vibration and longitudinal vibration and rotary vibration three categories. In ship construction, according to different types and different propulsion shafting, the shafting torsional vibration, vertical vibration and swing vibration calculation shall be submitted for examination and approval of classification society. For main propulsion shafting, should guarantee the maneuver is not commonly used speed range is too large amplitude vibration, should not be dangerous resonance speed, and not too large amplitude in the whole speed range of longitudinal vibration. If the shafting vibration amplitude of the stress or the rules and regulations of torque than the continuous running of the allowable values, should set up 'speed' of the area, in the area, the machine should not be running. Thus ship shafting vibration on normal sailing ship is a very important factor, the influence of abnormal vibration in addition to the may lead to machine can't work, also has a great influence to the stern bearing wear. 2, shafting center shafting alignment correction generally includes the method of lines ( The method of shaft) , bearing the allowable bearing load method and the reasonable load method three, the reasonable shipping shaft system alignment is usually adopt bearing load method. So-called reasonable load in the school, mainly considering the host hover effects when hot, hot state of the bearing load on the host when optimum reasonable distribution, the essence of which is to obey the rules of bearing load, stress and limit conditions, such as Angle, through the school of computing to determine the reasonable location of each bearing, shafting installation into the curve of the provisions of state, to make each bearing load distribution is reasonable. In shipbuilding, ship for adopting reasonable load alignment method of shaft system in the school, the school in the calculations shall be submitted to the classification society for approval. China classification society 'steel sea vessel classification and construction rules' and notice for surveyor of shafting alignment calculation, method and standard has explicitly stipulated in the school. Because of shafting alignment results directly affects the working condition of ship operating in the transmission system, affect the bearing load distribution. Thus, if the shafting alignment calculation inaccurate or alignment calculation of shafting installation, may make the uneven distribution of bearing load, causing overload bearing excessive wear. Bearing arrangement of water lubricated stern bearing material usually adopt common wood, acetate and other synthetic materials, each material based on their performance on the specific pressure, on the ship are not the same as its length when installation requirements. As China classification society rules of the water lubrication plows wood, synthetic rubber or plastic bearing, its length should be no less than specification required by 4 times the diameter of the propeller shaft calculation or 3 times the diameter of the actual, take its highly actie. Only guarantee the bearing length, thus ensuring the bearing stress area to make the bearing pressure conform to the requirements of the bearing material performance, so as to ensure the service life of the bearing. If not meet the requirements of the bearing size, will greatly speed up the bearing wear. Based on the analysis of the bearing damage reason, consult the ship engine log, found that the wheel that took place during a voyage, a month ago because of the propeller on the buoy, severe vibration of the shaft system of lead to damage of stern shaft seal, in the front axle is always in good running condition. So can conclude that the basic round stern bearing damage is caused by abnormal vibration in shaft system, the direct cause of abnormal vibration in shaft system is due to the propeller on the buoy, blade to lose its balance. In view of the above analysis, can determine the wheel original shafting alignment and bearing arrangement is reasonable. In addition to the damage of the propeller in the process of maintenance repair, according to the requirements of the repaired for stern bearing should be overall, can according to the ship stern shaft sleeve tube size as a benchmark to processing new stern bearing size. Processing an inner liner with stern tube the same false set; In the false welding set of locking plate; Set new bearing the acetate batten, according to the opinion of the acetate using manual and service providers, for running clearance to 3 mm, at the same time to make up for the center of the stern shaft sinking caused by deviation, stern bearing inner circle center service should be 50% x3 = 1. 5 mm, causes the stern shaft centerline and stern bearing center line in the overlap in the run. According to the size of set processing acetate lath; ( Can use whole boring machine and lathe processing, can also be separated two parts processing) Will be processed ready for batten, sequentially into the ship stern tube bushing; Measuring the actual diameter after installation; Stern shaft refitted, measuring clearance, intermediate shaft, measure the connecting flange of twists and turns and migration, measuring unit turn pick-and-roll and comparing with before the maintenance; Due to find out the specific cause of bearing damage, so the wheel from repair rear axle system running in good condition, does not appear again bearing damage.