Installation inspection of lower rudder bearing liner:

Before installing the upper and lower bearing bushings of the rudder, the diameter of the rudder knob hole must be remeasured with an inside micrometer, and the outer diameter of the bushing must be remeasured with an outside micrometer. The actual fit interference measured should meet the requirements of the drawing. Before measurement, the inside and outside micrometers should be checked.

2. The installation of the upper and lower bushings of the rudder generally adopts oil pump pressing. When pressing, the pressing force should be calculated based on the piston area of the oil pump and the oil pump pressure, and the pressing force should meet the technical requirements. Generally, the actual pressing force should be greater than the specified pressing force.

function

Support and reduce friction: The lower rudder bearing liner is installed inside the lower rudder bearing to provide support for the rudder stock, allowing it to rotate flexibly around its axis, while reducing friction between the rudder stock and the lower rudder bearing, reducing wear, and ensuring efficient operation of the rudder system

Bearing radial force: During the navigation of the ship, the rudder blades will be subjected to the force of water flow, which is transmitted to the lower rudder bearing liner through the rudder stock. The liner can withstand the radial force generated thereby, maintain the stability of the rudder stock, prevent excessive displacement or shaking, and ensure the maneuverability of the ship

Sealing and anti-corrosion: The clearance between the lower rudder bearing liner and the rudder stock needs to maintain a certain degree of accuracy to achieve good sealing effect, prevent leakage of media such as seawater and lubricating oil, and prevent external impurities from entering the interior of the rudder bearing, causing corrosion and damage to the rudder stock and liner

Structural characteristics

Lining body: It is usually made of metal materials such as bronze, brass, etc., which have good wear resistance, corrosion resistance, and self-lubricating properties, and can adapt to the frequent rotation of the rudder stock and the corrosive environment of seawater. The inner surface of the liner is generally finely processed to ensure the precision and surface quality of the fit with the rudder stock, reducing the friction coefficient

Installation method: The lower rudder bearing liner is generally installed inside the lower rudder bearing using interference fit or clearance fit. Interference fit can make the connection between the liner and the lower rudder support tighter, preventing displacement or loosening of the liner during operation; Gap fit facilitates the installation and removal of the liner, while also compensating to some extent for dimensional changes caused by temperature fluctuations or wear

Lubrication and sealing structure: In order to further reduce friction and prevent leakage, the lower rudder bearing liner is usually equipped with corresponding lubrication and sealing devices. The lubrication device can be an oil cup, oil groove, or centralized lubrication system, which injects lubricating oil into the gap between the liner and the rudder stock to form an oil film and reduce friction and wear. Sealing devices often use rubber sealing rings, oil seals, or mechanical seals, which are installed at both ends of the liner or other critical parts to effectively prevent medium leakage

Material selection

Metal materials: Bronze alloy is one of the commonly used lining materials, such as tin bronze, aluminum bronze, etc. Tin bronze has good wear resistance, corrosion resistance, and anti friction properties, and is suitable for lower rudder bearing bushings under general working conditions; Aluminum bronze has higher strength and hardness, as well as good resistance to seawater corrosion, and is commonly used in large ships or rudder systems under harsh sea conditions. In addition, brass alloys are widely used due to their good processing performance and economy, but their corrosion resistance is relatively weak and appropriate anti-corrosion measures need to be taken.

Non metallic materials: With the development of material technology, some non-metallic materials such as polytetrafluoroethylene (PTFE), nylon, etc. have also begun to be applied to the lower rudder bearing liner. These materials have extremely low friction coefficients, good self-lubricating properties, and corrosion resistance, which can effectively reduce the frictional resistance of the rudder stock and improve the efficiency of the rudder system. However, non-metallic materials have relatively low strength and heat resistance, and require reasonable selection and design based on specific working conditions

Gap requirements

The gap size between the lower rudder bearing liner and the rudder stock directly affects the performance and service life of the rudder system. Too small a gap can lead to increased friction between the liner and the rudder stock, resulting in overheating and increased wear and tear; If the gap is too large, it will affect the positioning accuracy of the rudder, resulting in a decrease in the maneuverability of the rudder system, and may cause vibration and noise of the rudder.

According to the regulations of various classification societies, the gap between the rudder bearing liner and the rudder stock under the rudder system shall not be less than (the diameter of the rudder stock). If the lower rudder bearing liner is made of non-metallic synthetic material, the gap between the lower rudder bearing liner and the rudder stock must not be less than

Maintenance and replacement

Daily maintenance: Regularly check the working condition of the rudder bearing liner, including visual inspection, wear measurement, lubrication condition inspection, etc. If cracks, severe wear, poor lubrication and other problems are found on the surface of the liner, corresponding measures should be taken in a timely manner for treatment, such as replacing the lubricating oil, repairing or replacing the sealing device, etc.

Regular replacement: The lower rudder bearing liner will gradually lose its original performance due to wear and tear after long-term use, so it needs to be replaced according to a certain cycle. Generally speaking, the replacement cycle of the liner depends on factors such as the frequency of use, navigation environment, and liner material of the vessel. It is usually inspected and replaced during dock repairs or regular maintenance of the vessel