explain:

Mainly suitable for various types of ships with large stern shaft diameter and axial movement, and lubricated with water as the medium.

SMA-II/IIB models are compensated by circular springs; SMC type is Ω - type spring compensation.

Water lubricated stern shaft seal is an important technology in ship engineering, which uses water as a lubricating medium to reduce friction and wear between the stern shaft and bearings, and has the advantages of environmental protection, energy saving, and no pollution. The following is a detailed explanation of the water lubricated stern shaft seal:

Definition and Basic Principles

Water lubricated stern shaft seal is a sealing device used for ship stern shafts. Its main purpose is to prevent seawater from entering the interior of the ship, while ensuring that the stern shaft can operate normally under water lubrication conditions. Its working principle is to form a barrier between the stern shaft and the sealing device by tightly contacting the sealing element with the surface of the stern shaft, utilizing the elastic deformation and friction of the sealing element to prevent seawater from passing through.

For example, in some small ships, simple rubber sealing rings are used as the main component of water lubricated stern shaft seals. The rubber sealing ring is fitted onto the stern shaft and tightly adheres to the surface of the stern shaft under the pressure of seawater and its own elasticity, preventing seawater from entering the ship along the stern shaft.

Main component composition

Sealing ring: This is one of the key components. Usually made of rubber or other polymer materials, it has good elasticity and wear resistance. The shape and size of the sealing ring should be tightly adapted to the stern shaft, with its inner diameter slightly smaller than the outer diameter of the stern shaft, to ensure sufficient clamping force can be generated after installation. Different ships will choose different types and materials of sealing rings based on factors such as the size and speed of the stern shaft.

Lining: The lining is generally installed inside the stern shaft sealing device, which directly contacts the stern shaft and provides support and guidance for the stern shaft. The lining material is usually selected from metals or alloys with good wear resistance and corrosion resistance, such as bronze. Its surface needs to have a high degree of smoothness to reduce friction with the stern shaft and effectively disperse the pressure generated during the operation of the stern shaft.

Cap: Cap is mainly used to fix the sealing ring and liner, so that they will not shift during the operation of the stern shaft. The gland is tightly connected to the outer shell of the stern shaft sealing device through bolts and other connectors, and the clamping force between the sealing ring and the stern shaft can be controlled by adjusting the tightening degree of the gland. If the clamping force is too strong, it will increase the frictional resistance of the stern shaft and affect the efficiency of the ship's power system; If the clamping force is too small, it may lead to poor sealing and seawater leakage.

advantage

Good lubrication performance: Water as a lubricant can effectively reduce friction and wear between the stern shaft and the sealing device. Compared with traditional oil lubrication, water lubrication can avoid the pollution caused by oil leakage to the marine environment. For example, water lubricated stern shaft seals are an ideal choice for ships navigating in areas with high environmental requirements.

Low cost: Water is an easily accessible resource that does not require regular replenishment and replacement of expensive lubricants like oil lubrication. Moreover, the structure of the water lubricated stern shaft sealing device is relatively simple, and the maintenance cost is also relatively low.

High safety: Due to the absence of lubricating oil, the risk of fire caused by lubricating oil leakage is reduced, which is of great benefit to the safe operation of ships.

Disadvantages and challenges

Difficulty in sealing: Compared with oil lubrication, the viscosity of water is lower, which makes it more difficult for water lubricated stern shaft seals to achieve the same sealing effect. The corrosiveness of seawater can also cause damage to the components of the sealing device, shortening its service life.

High requirements for stern shaft materials: Under water lubrication conditions, the stern shaft is more prone to corrosion, so it is necessary to choose stern shaft materials with good corrosion resistance or perform special anti-corrosion treatment on the stern shaft, which increases the construction cost of the ship.

Maintenance points

Regular inspection: It is necessary to regularly check the wear of the sealing ring, the surface smoothness of the liner, and the tightness of the gland. For example, if obvious wear, aging, or damage is found on the sealing ring, it should be replaced in a timely manner. Generally speaking, the inspection cycle depends on the frequency of use and navigation environment of the vessel. For vessels navigating in harsh sea conditions, the inspection cycle should be shorter.

Cleaning work: It is very important to keep the interior of the stern shaft sealing device and the surface of the stern shaft clean. Impurities and sediment in seawater may enter the sealing device, exacerbating the wear of sealing components. When a ship enters port or undergoes regular maintenance, the stern shaft and sealing device should be cleaned.

Reasonably adjust the clamping force: Based on the operation and sealing effect of the stern shaft, adjust the clamping force between the sealing ring and the stern shaft reasonably. This requires experienced technicians to use professional tools for operation to ensure the sealing effect and normal operation of the stern shaft.