Definition and Function

The stern shaft lubricating oil tank is an important equipment used in ship power systems to store and supply stern shaft lubricating oil. Its main function is to provide continuous and clean lubricating oil for the stern shaft bearings and sealing devices to reduce friction and wear, while taking away heat and ensuring the normal operation of the stern shaft system. In addition, it can also play a role in precipitating impurities and separating water, ensuring the quality of lubricating oil.

Structural composition

Box section:

The body of the fuel tank is usually welded from metal materials (such as steel plates), which have sufficient strength and sealing. The shape of the box is generally designed according to the spatial layout and capacity requirements of the ship, commonly including rectangular prisms, cylindrical shapes, etc. The interior of the box will undergo anti-corrosion treatment to prevent lubricating oil from corroding the box. For the convenience of observing the oil level, an oil level gauge is installed on the box, which can be a glass tube oil level gauge or a float type oil level gauge.

Oil inlet and outlet section:

Imported for adding new lubricating oil or receiving lubricating oil returning from the stern shaft system. Imports are usually equipped with filters to filter out impurities in the return oil, preventing impurities from entering the oil tank and circulating back to the stern shaft system. The outlet is connected to the lubricating oil pump, which delivers lubricating oil to the stern shaft bearing and sealing device through the pump. Valves may also be installed at the outlet to control the flow of lubricating oil.

Oil pump and filtration system:

Oil pump is a key equipment that transports lubricating oil from the oil tank to the stern shaft system, usually using gear pumps or screw pumps. The flow rate and pressure of the oil pump should be determined according to the lubrication requirements of the stern shaft system. The filtration system includes a coarse filter and a fine filter. The coarse filter is used to filter out larger particles of impurities, while the fine filter can filter out smaller impurities to ensure the cleanliness of the lubricating oil delivered to the stern shaft system.

Breathable device and liquid level alarm device:

The breathable device is used to balance the air pressure inside and outside the fuel tank. When lubricating oil is pumped out or refluxed, the air pressure inside the oil tank will change. The ventilation device can allow air to enter and exit the oil tank, ensuring that the pressure inside the oil tank is normal. The liquid level alarm device can monitor the level of oil and issue an alarm when the oil level is too low or too high, reminding the crew to take timely measures to prevent the lubrication of the stern shaft system from being affected by abnormal oil level.

working principle

Lubricating oil is stored in the oil tank, and when the stern shaft system needs lubrication, the oil pump starts. The oil pump extracts lubricating oil from the outlet of the oil tank, removes impurities through the filtration system, and delivers the lubricating oil to the stern shaft bearing and sealing device through pipelines. During the operation of the stern shaft, lubricating oil forms an oil film between the bearings and the sealing device, reducing friction while absorbing heat. The used lubricating oil flows back to the oil tank through the return pipeline, and during the return process, the filter at the inlet filters the lubricating oil again. The breathable device inside the fuel tank ensures stable air pressure, while the liquid level alarm device monitors the oil level in real-time.

advantage

Ensure lubrication quality: Through the filtration system and sedimentation effect, clean lubricating oil can be provided for the stern shaft system, reducing the wear of impurities on the stern shaft bearings and sealing devices, and improving their service life. Meanwhile, a stable oil supply ensures that the stern shaft system is always in good lubrication condition.

Temperature regulation function: Lubricating oil can take away the heat generated by the operation of the stern shaft during circulation, playing a cooling role. Moreover, the fuel tank itself has a certain heat dissipation capacity, which helps to maintain the temperature of the stern shaft system within a reasonable range and prevent damage to components due to excessive temperature.

Easy to maintain and manage: Equipment such as oil level gauges and liquid level alarm devices enable crew members to easily observe and monitor the condition of lubricating oil, detect problems in a timely manner, and carry out maintenance. Moreover, it is convenient to add and replace lubricating oil and clean filtering equipment at the oil tank.

Disadvantages and countermeasures

Risk of oil leakage: Due to the numerous oil tanks, connecting pipelines, and equipment, poor sealing may result in oil leakage. The response measures include regular inspection of sealing parts, such as oil pump seals, pipeline connections, etc., and timely replacement of damaged seals. At the same time, in the design and installation process, it is necessary to improve the reliability of the seal, such as using high-quality sealing materials and sealing structures.

Lubricating oil contamination issue: Despite the presence of filtration systems, lubricating oil may still be contaminated, such as water ingress and microbial growth. Regularly check the quality of lubricating oil, such as detecting indicators such as water content and acidity. For moisture, it can be removed by installing oil-water separation devices; For microbial growth, preservatives can be added or lubricating oil can be replaced regularly to solve the problem.

Application scenarios

Stern shaft lubrication in ship power systems: In various ships that lubricate the stern shaft with oil (such as large cargo ships, oil tankers, warships, etc.), the stern shaft lubrication oil tank is an indispensable equipment to ensure the normal operation of the stern shaft system. It provides lubrication and cooling for the stern shaft bearings and sealing devices, which is an important guarantee for safe navigation of ships.