Large tin bronze bushings for ship stern shafts

The stern shaft is the shaft that extends out of the stern through the stern tube. One end of the stern shaft is connected to the propeller, and the other end is connected to the gearbox or coupling and then to the engine. The stern shaft of a large ship is installed on two bearings, one is called the stern bearing, which is the part of the hull that contacts the water. The other is called the front copper sleeve, which is connected to the engine room. The stern shaft is generally composed of a flange, a shaft, a journal, a tapered shaft and a stud. The journal contains the stern tube assembly. The function of the stern tube is to support the weight of the propeller and the stern shaft (stern bearing). The stern shaft copper sleeve is installed on the stern tube of the journal. For ships using water lubrication, bearings are generally installed on the journal of the stern shaft to prevent journal friction and corrosion. The bearings are generally assembled on the shaft with an interference fit.

Technical requirements
1.The sleeve material is generally tin bronze 10-2. For the processed copper bearing, cracks, dense pores, looseness and sand holes are not allowed. For defects that are not very serious, repairs are allowed. After the bearing is roughly processed and before it is installed on the shaft neck, it should be subjected to a water pressure test with a test pressure of 0.2MPa. There should be no cracks or leakage within 5 minutes. 

2.The roundness and cylindricity of the bearing should meet the requirements. 

3.The bearing should be pressed into the shaft by red sleeve or hydraulic sleeve method, and it shall not be fixed with pins. After the copper sleeve is on its red sleeve shaft, its tightness should be checked. It is strictly forbidden to have loose fit at a distance of 70mm from the end of the tail shaft cone. 

4.In order to reduce the stress concentration phenomenon of the bearing red sleeve on the shaft, unloading grooves are often opened at both ends of the sleeve. 

The surface roughness of the copper sleeve of the tail shaft Ra≤1.6um. When pulling the oil groove, the oil groove should be straight and the burrs should be trimmed.

Material selection
The stern tube bearing is located inside the tail tube, below the water level, and has harsh working conditions. It has to bear the uneven cantilever load when the propeller rotates and the dynamic load when the propeller accidentally hits an obstacle, as well as the weight of the stern and propeller and the additional vibration force that may occur during operation. Since the stern tube bearing is difficult to check when the ship is sailing, in order to prevent the ship from being affected by its failure, the stern shaft copper sleeve must be wear-resistant and corrosion-resistant. Therefore, the material of the stern shaft copper sleeve is generally ZCuSn12Ni2. ZCuSn12Ni2 cast copper alloy has high strength, elasticity, wear resistance and anti-magnetism, good pressure processing in hot and cold states, high flame resistance to electric sparks, can be welded and brazed, has good machinability, and is corrosion-resistant in the atmosphere and fresh water.

As a professional manufacturer engaged in the research and development of copper alloy components and self-lubricating bearings for more than ten years, we look forward to further improving product performance and application scope through continuous research and technology accumulation, and serving global companies. If you have any product or technical questions, please feel free to contact us: [email protected].