Marine compressor shafting sealing system
By designing a marine compressor shaft sealing system, utilizing sealing sleeves, carbon ring structures, and high-pressure sealing gas, the problem of natural gas leakage between explosion-proof and non-explosion-proof areas was solved, thus achieving explosion-proof safety for LNG transport vessels.
Patent Information
- Application Number
- CN202511491504.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-19
- Publication Date
- 2025-11-28
AI Technical Summary
In existing technologies, heavy-duty centrifugal compressors pose a safety hazard of natural gas leakage between explosion-proof and non-explosion-proof areas in LNG transport vessels, resulting in insufficient safety.
A marine compressor shaft sealing system was designed, including a sealing sleeve, a hull sealing mechanism, and a gas passage. The system utilizes the high pressure of the sealing gas to prevent natural gas leakage. An effective gas isolation is established between the explosion-proof and non-explosion-proof areas through the sealing sleeve and carbon ring structure. The sealing effect is ensured by combining a backup gas source and a self-regulating pressure regulating valve.
It effectively prevents natural gas from mixing between explosion-proof and non-explosion-proof areas, improving the safety of the ship and ensuring explosion-proof safety during LNG transportation.
Smart Images
Figure CN121024971A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sealing device technology, specifically to a marine compressor shaft sealing system. Background Technology
[0002] The frequent trading of liquefied natural gas (LNG) necessitates the use of heavy-duty (HD) centrifugal compressors in LNG carriers. When LNG carriers are docked at the port of origin, the HD centrifugal compressors extract natural gas from onshore LNG storage tanks and pressurize it for transfer to the ship's LNG storage tanks. Upon arrival at the destination port, the LNG carriers also need to transfer the natural gas from their onboard LNG storage tanks to LNG storage tanks at the port.
[0003] The basic layout of a skid-mounted centrifugal compressor unit is as follows: the compressor main unit and its instruments are located in the explosion-proof area of the ship's hold, while the main motor is located in the non-explosion-proof area of the ship's hold. They are separated by a metal bulkhead welded into the ship's "wall," and the compressor-main motor shaft, equipped with a coupling, extends through the metal bulkhead. Because the heavy-duty (HD) centrifugal compressor is installed in the LNG carrier's hold, and the compressor needs to pressurize and transport LNG between the ship and the port, the unit has very high explosion-proof safety requirements. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention provides a marine compressor shaft sealing system that can resolve the safety hazard of natural gas leaking from the explosion-proof zone to the non-explosion-proof zone, which may occur during static or operational operation of the compressor unit.
[0005] The technical solution is as follows: A marine compressor shaft sealing system includes a compressor main unit located in an explosion-proof hazardous area, a main motor located in a non-explosion-proof area, and a metal cabin bulkhead located between the compressor main unit and the main motor. The main motor is connected to the compressor main unit via a coupling passing through the metal cabin bulkhead. The system is characterized in that a sealing sleeve is fitted onto the motor shaft of the main motor, and a cabin sealing mechanism is fitted outside the sealing sleeve. The cabin sealing mechanism includes a sealing outer shell and at least two carbon rings disposed within the sealing outer shell. A gas gap exists between the carbon rings and the sealing sleeve. A gas channel is provided between the carbon rings, connecting an air inlet on the sealing outer shell and the gas gap. The air inlet is connected to one end of a sealing gas pipe passing through the metal cabin bulkhead, and the other end of the sealing gas pipe is connected to a sealing gas source.
[0006] A further feature is that a cabin sealing installation platform is installed on the outer casing of the main motor, the cabin sealing mechanism is connected to the cabin sealing installation platform, and the cabin sealing installation platform has a hollow structure. The sealed gas pipeline is equipped with a manual valve and a self-operated pressure regulating valve; The sealing gas pipeline is also equipped with a bypass gas pipeline, which is connected to a backup gas source. A compressor shaft protective cover is provided between the compressor main unit and one side of the metal cabin bulkhead, and a coupling protective cover is installed on the other side of the metal cabin bulkhead; An expansion joint is provided between the coupling protective cover and the cabin sealing mechanism.
[0007] With this invention, the sealing gas entering the ship's cabin sealing mechanism is divided into two paths, one entering the main motor side and flowing out through the gap on the mounting platform at the main motor, and the other passing through the metal cabin bulkhead and flowing out through the gap on the compressor main unit side. Since the pressure of the sealing gas is always higher than the external atmospheric pressure, it can ensure that the sealing gas enters the atmosphere, preventing natural gas in the explosion-proof danger zone and air in the non-explosion-proof zone from entering each other's areas, eliminating safety hazards and improving safety. Attached Figure Description
[0008] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a cross-sectional view of the cabin sealing mechanism of the present invention; Figure 3 for Figure 2 Enlarged diagram of point A in the middle. Detailed Implementation
[0009] See Figure 1 , Figure 2 , Figure 3As shown, a marine compressor shaft sealing system includes a compressor main unit 1 located in an explosion-proof hazardous area, a main motor 2 located in a non-explosion-proof area, and a metal cabin bulkhead 3 located between the compressor main unit 1 and the main motor 2. The main motor 2 is connected to the compressor main unit 1 through a coupling 4 that passes through the metal cabin bulkhead 3. A sealing sleeve 5 is fitted on the motor shaft of the main motor 2, and an O-ring is provided on the inner wall of the sealing sleeve 5. This seal prevents natural gas that may be present in the explosion-proof area from entering the non-explosion-proof area through the gap between the sealing sleeve 5 and the motor shaft. The sealing sleeve 5 is fitted with a cabin sealing mechanism 6. The cabin sealing mechanism 6 includes a sealing shell and two carbon rings set inside the sealing shell. The number of carbon rings can be adjusted as needed. There is a gas gap between the carbon rings and the sealing sleeve 5, which allows sealing gas to pass through. A gas channel 7 is provided between the carbon rings, connecting the air inlet on the sealing shell and the gas gap. A pipe joint 8 is installed on the air inlet and connected to one end of the sealing gas pipe 9 that passes through the metal cabin bulkhead 3. The other end of the sealing gas pipe 9 is installed with a sealing gas interface 10 that connects to the sealing gas source. The sealing gas source is generally clean instrument air. A hand valve 11 and a self-regulating pressure regulating valve 12 are provided on the sealing gas pipe 9. After the sealing gas is depressurized by the self-regulating pressure regulating valve 12, it finally enters the cabin sealing mechanism 6. Carbon ring sealing is an existing technology. The specific principle is as follows: There are two or more floating carbon rings on the inner side. After the sealing gas is depressurized, it enters the inner cavity through the sealing body interface. In the inner cavity, it is divided into left and right branches. Under the pressure of the sealing gas, the carbon rings separate from one side of the inner cavity wall, and there is a certain gap between them. The sealing gas accumulates in the space above through this gap. At the same time, the other side of the carbon ring is tightly attached to the cavity wall. The flow of sealing gas between the two attached surfaces is blocked at this point, and finally only a small amount of sealing gas leaks radially to the atmosphere.
[0010] To improve reliability, a bypass gas pipeline 17 is also provided on the sealing gas pipeline 9. The bypass gas pipeline 17 is equipped with a backup gas interface 18 that connects to the backup gas source. If the instrument air is not available (such as gas source interruption, water (oil) content, too many solid particles, etc.), the bypass gas pipeline 17 needs to be opened to switch to nitrogen as the sealing gas. The nitrogen enters the sealing gas pipeline 9 through the backup gas interface 18.
[0011] A compressor shaft guard 13 is provided between the compressor main unit 1 and one side of the metal cabin bulkhead 3. A coupling guard 14 is installed on the other side of the metal cabin bulkhead 3. An expansion joint 15 is provided between the coupling guard 14 and the cabin sealing mechanism 6. The expansion joint 15 is used to compensate for the axial or angular displacement caused by hull swaying, thermal expansion, and unit vibration.
[0012] The left side of the cabin sealing mechanism 6 is connected to the cabin sealing mounting platform 16, and the right side is connected to the expansion joint 15. Sealing gaskets are installed between the cabin sealing mounting platform 16 and the cabin sealing mechanism 6, between the cabin sealing mechanism 6 and the expansion joint 15, between the expansion joint 15 and the coupling protective cover 14, between the coupling protective cover 14 and the metal cabin bulkhead 3, and between the metal cabin bulkhead 3 and the compressor shaft protective cover 13. The pressure of the sealing gas is always higher than the external atmospheric pressure. After entering the cabin sealing mechanism 6, the sealing gas passes through the gas channel 7 to reach the gas gap between the carbon ring and the sealing sleeve 5, and then splits into two paths to the left and right. The flow direction of the sealing gas is as follows: Figure 3 As shown by the red line, the left path flows towards the main motor and enters the cabin sealing installation platform 16, which is fixed to the outer shell of the main motor 2. The cabin sealing installation platform 16 has a hollow structure, which allows the sealing gas to flow out smoothly into the atmosphere of the non-explosion-proof area. The right path flows towards the compressor main unit 1, passes through the coupling protective cover 14 and the metal cabin bulkhead 3, and enters the compressor shaft protective cover 13. The sealing gas can flow out from the connection gap between the compressor shaft protective cover 13 and the compressor main unit 1 into the atmosphere of the explosion-proof hazardous area, thus preventing natural gas in the explosion-proof area and air in the non-explosion-proof area from crossing into each other's areas.
Claims
1. A marine compressor shaft sealing system, comprising a compressor main unit located in an explosion-proof hazardous area, a main motor located in a non-explosion-proof area, and a metal bulkhead located between the compressor main unit and the main motor, wherein the main motor is connected to the compressor main unit via a coupling penetrating the metal bulkhead, characterized in that, A sealing sleeve is fitted onto the motor shaft of the main motor. A cabin sealing mechanism is fitted onto the outside of the sealing sleeve. The cabin sealing mechanism includes a sealing shell and at least two carbon rings disposed within the sealing shell. A gas gap exists between the carbon rings and the sealing sleeve. A gas channel is provided between the carbon rings, connecting an air inlet on the sealing shell and the gas gap. The air inlet is connected to one end of a sealing gas pipe that penetrates the metal cabin bulkhead. The other end of the sealing gas pipe is connected to a sealing gas source. A cabin sealing installation platform is mounted on the housing of the main motor. The cabin sealing mechanism is connected to the cabin sealing installation platform. The cabin sealing installation platform has a hollow structure. A manual valve and a self-regulating pressure regulating valve are provided on the sealing gas pipe.
2. The marine compressor shaft sealing system according to claim 1, characterized in that, The sealed gas pipeline is also equipped with a bypass gas pipeline, which is connected to a backup gas source.
3. The marine compressor shaft sealing system according to claim 1, characterized in that, A compressor shaft guard is provided between the compressor main unit and one side of the metal cabin bulkhead, and a coupling guard is installed on the other side of the metal cabin bulkhead.
4. A marine compressor shaft sealing system according to claim 1, characterized in that, An expansion joint is provided between the coupling protective cover and the cabin sealing mechanism.