Air sealing three-support oil lubrication split type stern tube device and design method

Abstract

The invention relates to an air seal three-support oil lubrication split type stern tube device and a design method. The air seal three-support oil lubrication split type stern tube device comprises a tail seal, a rear shaft hub, a rear bearing, a rear shaft tube, a flow guide cover, a middle shaft hub, a middle bearing, a front shaft tube, a front shaft hub, a front bearing, a head seal, a stern tube, a tube support and an oil, water and gas external pipeline system which are sequentially arranged from the stern to the bow. Optimized design is carried out by considering the characteristics of oil lubrication stern tube air and lubricating oil circulation and arrangement of bearings and shaft hubs, and the problems of oil and gas pipeline arrangement and supporting, stern tube lubricating oil supply and circulation, stern tube bearing installation and maintenance, stern tube welding and installation and the like are solved. The device comprises a stern tube lubricating oil circulating system, an air sealing system, an oil pipe and an air pipe (including a supporting bracket and a pipe joint) in the stern tube, a bearing, a sectional stern tube, a shaft package and the like. The installation process is simple, pipeline arrangement is reasonable, air and lubricating oil circulation is efficient, and the overall installation and maintenance convenience and operation reliability of the stern tube device are improved.

Description

Technical Field

[0001] This invention relates to the field of marine engineering equipment technology, and in particular to a split-type stern tube device with air sealing, three supports, and oil lubrication suitable for large ships, and its systematic design method. Background Technology

[0002] Ship propeller shaft support systems typically employ either oil lubrication or water lubrication. Oil lubrication remains widely used in ships due to its reliability. If oil-lubricated propeller bearings are used, a stern tube is required between the propeller shaft and the seawater. Depending on the number of propeller support bearings, there are double-supported, triple-supported, or multi-supported stern tubes. Seals are installed between the fore and aft hubs and the shaft within the stern tube; the stern seal is located at the stern, and the bow seal at the bow. Modern ships, to isolate the oil-water interface and balance internal and external pressures during significant draft changes, incorporate an air chamber within the stern seal—an air seal. The stern tube can be assembled in sections by welding the hub and steel tube at the shipyard, or it can be a pre-assembled, integral stern tube supplied from an equipment manufacturer.

[0003] In existing patent technologies, such as patent document (CN206704501U), a marine pipeline structure for oil lubrication is disclosed. This structure uses seamless steel pipes to connect multiple bearing seats and achieves segmented connections through welded components. While this structure achieves a three-bearing arrangement, it lacks an air-sealed cavity and relies solely on mechanical seals to prevent oil leakage. This results in insufficient sealing reliability and an inability to cope with internal and external pressure differences caused by draft changes. Furthermore, its sensor tube requires drilling through multiple bearings, leading to a complex structure that is prone to damaging the bearings. It also lacks dedicated pipeline support and maintenance channels, making subsequent maintenance difficult. Patent document (CN204642137U), on the other hand, proposes an integrated stern tube device that integrates the stern tube, fore and aft bearings, oil and gas pipes, and sensor protection pipe into a single unit for overall installation. While this solution reduces the boring and press-fitting processes in the dry dock stage, its integral structure cannot meet the technological requirements of segmented construction of large ships; moreover, it only has two bearings, front and rear, which is not suitable for three-support high-precision shafting systems; at the same time, the structure does not consider air seal design, which cannot meet the IMO's environmental protection requirements for oil-water interface isolation.

[0004] In summary, the existing technology has the following technical problems:

[0005] 1. Lacking an air-sealed structure, it cannot effectively isolate the oil-water interface and is difficult to adapt to large changes in ship draft;

[0006] 2. The lack of a systematic piping and bearing arrangement for the three-support layout led to difficulties in installation and coaxiality control.

[0007] 3. There are no dedicated maintenance channels or process holes. The stern tube needs to be disassembled for bearing clearance inspection and pipeline maintenance, which is costly.

[0008] 4. Improper pipe support and layout can easily lead to loose joints or sensor failure due to vibration;

[0009] 5. The monolithic structure is not suitable for sectional shipbuilding processes, which limits its application in large ships.

[0010] Therefore, it is necessary to design an air-sealed, three-support, oil-lubricated, split-type stern tube. Summary of the Invention

[0011] The purpose of this invention is to provide an air-sealed, three-support, oil-lubricated, split-type stern tube device and its design method, solving the technical problems of poor sealing reliability, difficult installation and maintenance, and unsuitability for segmented construction in the prior art, and meeting the requirements of air sealing, three-support, and oil lubrication. The stern tube and its design method of this invention include the design, installation, and arrangement relationships of a stern tube lubrication oil circulation system, an air sealing system, internal oil and air pipes (including support brackets and pipe joints), bearings, segmented shaft tubes, shaft hubs, and external piping systems. The stern tube bearings of this invention are fixed inside the shaft hub by epoxy casting or by press-fitting. This invention solves problems related to stern tube piping arrangement, oil and gas circulation, bearing installation, bearing and shaft inspection, and stern tube oil draining, and has significant practical value.

[0012] To achieve the above objectives, the technical solution of the present invention is as follows:

[0013] A split-type stern tube device with air-sealed three-support oil lubrication includes, from stern to bow, a stern seal, aft shaft hub, aft bearing, aft shaft tube, a shroud, center shaft hub, center bearing, front shaft tube, front shaft hub, front bearing, and a bow seal, a stern tube and tube support, and external piping systems for oil, water, and air. The stern seal has four sealing rings, with rings #1 and #2 facing the stern to prevent seawater ingress, and rings #3 and #3S facing the bow to prevent lubricating oil leakage. An air cavity is formed between rings #2 and #3, which includes a continuously supplying air inlet pipe and a drain pipe. The bow seal has rings #4 and #5 and an oil tank with a high-level alarm. Sealing rings #4 and #5 face the stern to prevent lubricating oil from flowing into the tank. The stern tube contains sensor pipes, oil pipes, and air pipes, connected by pipe fittings and supported by pipe supports within the stern tube. The external oil, water, and air piping system includes: an air control unit to control the air pressure to the stern seal and stern tube lubricating oil tank, with a low flow alarm function; a stern tube lubricating oil tank to provide lubricating oil to the stern tube and lubricating oil pump unit, with high / low level alarm functions; a lubricating oil pump unit to provide circulating lubricating oil to the stern tube and stern seal; and a discharge collection unit to collect oil and water leaking from the stern seal, with an air flow controller and a high level alarm function.

[0014] Furthermore, the white alloy bearings are fixed in the rear axle hub, the middle axle hub, and the front axle hub by epoxy casting; each axle hub has an epoxy injection port below the bearing mounting section and an epoxy vent above it, with the rear axle hub having two vents and the middle axle hub and the front axle hub each having one vent.

[0015] Furthermore, each axle hub has radial adjustment screw holes at 45°, 135°, 225°, and 315° in the circumferential direction for installing adjustment screws; the rear axle hub and the middle axle hub each have 4 screw holes on both ends of the bearing, for a total of 8; the front axle hub has only 4 screw holes on one end, and the other end is fixed and adjusted in the compartment through the flange attached to the bearing.

[0016] Furthermore, the rear axle tube connects the rear axle hub and the center axle hub. It has a 600mm diameter process hole near the lower part of the rear axle hub for installing oil pipes, air pipes and sensor pipe joints. After installation, it is repaired by welding with steel plate. A manhole cover is provided near the upper part of the center axle hub for pipeline installation and for checking the bearing clearance when the ship enters the dry dock.

[0017] Furthermore, the front axle tube connects the center shaft hub and the front axle hub, and a manhole cover is provided in the middle of the tube or at a required position for inspecting the propeller shaft.

[0018] Furthermore, the stern tube is equipped with seven functional pipelines, including: an oil inlet pipe and an oil return pipe for the stern seal 3# / 3S# oil chamber, an air inlet pipe and an air vent pipe for the stern seal 2# / 3# air chamber, and temperature sensor pipes leading to the rear bearing, middle bearing, and front bearing, respectively; the pipelines are connected by pipe joints and supported by pipe supports welded to the inner or outer wall of the stern tube, with a support span of 800-1000mm.

[0019] Furthermore, the rear bearing has a rear flange, which is pre-drilled with screw holes and air holes that match the tail seal, and is connected to the oil pipe and air pipe inside the stern tube via a right-angle joint; the bottom of the flange is provided with an oil drain plug with a sealing ring; a sensor tube is provided below the rear bearing and a temperature sensor is installed.

[0020] Furthermore, the rear bearing housing of the intermediate bearing has no front or rear flanges, and a through hole is provided on the rear bearing housing for the tail sealing oil pipe, air pipe and rear bearing sensor pipe to pass through; a sensor pipe and a temperature sensor are provided slightly below the intermediate bearing.

[0021] Furthermore, the front bearing has a front flange, with a sensor tube and temperature sensor installed slightly below it; the front flange centrally arranges the tail seal oil / gas inlet / outlet pipe, the middle and rear bearing sensor tube, the stern pipe inlet / outlet oil pipe and its connectors, realizing the integration of pipeline interfaces.

[0022] A design method for the above-mentioned stern tube device includes:

[0023] (1) Rear, middle and front axle hub design

[0024] (1.1) Hub size design: Based on the classification society specifications for the stern hub dimensions, the values ​​are calculated using the following formulas: Hub thickness: t = 0.33 × d³, Hub length: l = 3 × d s In the formula: d s —Diameter of the tailpipe shaft at the hub, mm.

[0025] (1.2) Shaft hub design: The bearing is installed on the shaft hub with epoxy resin. The shaft hub needs to consider the design of epoxy casting holes and adjustment holes. After the bearing is installed, the openings of the epoxy casting holes and adjustment screw holes on the outer surface are sealed by welding with 50mm diameter round steel. The shaft hub is made into a conical shape or welded with a flow guide to improve water flow.

[0026] (2) Rear and front axle tube design:

[0027] (2.1) Rear Axle Tube Design: The rear axle tube connects the rear axle hub and the center axle hub. A 600mm diameter process hole is provided below the axle tube near the rear axle hub for the installation of oil, gas, and sensor pipeline connectors. After the pipeline installation is completed, it is repaired by welding with steel plates. A manhole cover is provided above the axle tube near the center axle hub. This manhole cover is used for pipeline installation and also facilitates the inspection of the clearance between the shaft and the center bearing when the ship enters dry dock. In order to reduce appendage drag, the manhole cover can be placed inside the fairing.

[0028] (2.2) Front shaft tube design: The front shaft tube connects the center shaft hub and the front shaft hub. A manhole cover is provided in the middle or at the required position to facilitate the maintenance of the propeller shaft.

[0029] (2.3) Welding design: A welding bevel is reserved at the connection surface between the stern tube and the hub. A 30×8 steel ring can be spot welded at the outer diameter to facilitate welding. After the welding between the stern tube and the hub is completed, the paint needs to be repaired.

[0030] (3) Design of stern tube piping and supports:

[0031] (3.1) Piping Design: There are a total of 7 pipes inside the stern tube, including oil pipes: the oil inlet and return pipes to the oil chamber before tail seal #3 / 3S#, and the air inlet and vent pipes to the air chamber before tail seal #2 / 3#. Sensor pipes include: the temperature sensor pipe to the aft bearing, the sensor pipe to the middle bearing, and the sensor pipe to the front bearing. Steel or copper pipes are used for the piping, minimizing unnecessary joints.

[0032] (3.2) Pipe support design: The pipe supports adopt the type of welding inside the stern tube and the type of welding outside the stern tube. The pipe supports are evenly distributed and the span is 800-1000mm.

[0033] (4) Design of rear, middle and front bearings:

[0034] (4.1) Aft Bearing Design: The aft bearing housing has a rear flange. Before leaving the factory, screw holes and air holes are drilled on this flange according to the installation requirements of the tail seal. It is connected to the oil pipe and air pipe inside the stern tube through a right-angle connector. The lower part of the flange is the lowest point of the stern tube, where an oil drain plug is installed. To ensure no oil leakage, a sealing ring is installed below the drain plug. The aft bearing sensor tube is installed below the bearing, and the sensor is mounted thereon.

[0035] (4.2) Middle Bearing Design: The rear bearing housing has no flanges at the front and rear, but pipe passage holes are required for the tail sealing oil, air pipe, and rear bearing sensor. The middle sensor tube is installed slightly below the bearing, and the sensor is mounted there.

[0036] (4.3) Front bearing design: The front bearing is equipped with a front flange, and the front sensor tube is set and the sensor is installed on the lower part of the bearing; and the tail sealing oil and gas inlet and outlet pipes, the middle and rear bearing sensor tubes, the stern pipe oil inlet and return pipes, and the pipe joints are reasonably arranged at the front bearing.

[0037] (5) Installation quality inspection:

[0038] (5.1) Coaxiality inspection: The coaxiality of the fore, middle and aft stern bearings shall be re-measured according to standard GB / T34000-2016 after on-site installation and stern tube welding;

[0039] (5.2) Tightness test: After the stern tube, the oil circuit in the stern tube and the sensor protection tube are installed, a 0.2MPa tightness test shall be performed. The inside of the stern tube and each pipeline must be kept clean.

[0040] The present invention has the following beneficial effects:

[0041] 1. Reliable air-sealed structure: Through the continuous air supply chamber between #2 and #3, the oil-water interface is effectively isolated, adapting to changes in draft, preventing lubricating oil from leaking into the ocean, and meeting environmental protection requirements;

[0042] 2. Reasonable three-support layout: The front, rear, and middle bearings work together to support the shaft system, improving the rigidity and stability of the shaft system, which is suitable for high-power propulsion systems of large ships;

[0043] 3. Modular design adapts to shipbuilding processes: Each section can be prefabricated in the shipyard and welded on-site, making it compatible with modern modular shipbuilding processes;

[0044] 4. Convenient maintenance: The rear axle tube is equipped with a process hole and a manhole cover, and the front axle tube is equipped with a manhole cover, so the bearing clearance can be checked and the sensor can be replaced without disassembly;

[0045] 5. Piping system integration and optimization: The seven functional pipelines are clearly categorized and firmly supported, reducing vibration interference and improving system reliability;

[0046] 6. High bearing installation accuracy: Epoxy casting + adjusting screw dual positioning, combined with coaxiality re-measurement, ensures the alignment accuracy of the shaft system;

[0047] 7. Strong fault tolerance: When the #3 sealing ring fails, the #3S# spare sealing ring will automatically engage to ensure navigation safety;

[0048] 8. Easy to clean and maintain: The air chamber and pipeline can be cleaned with fresh water, extending the life of the seal.

[0049] In summary, this invention employs a rationally arranged and cost-effective three-support stern tube design method. By considering the characteristics of oil-lubricated stern tube air-oil circulation and bearing arrangement, and through the design of the lubricating oil circulation system, air sealing system, oil and air pipes (including support brackets and pipe joints) inside the stern tube, bearings, segmented stern tube, and shaft housing, a method suitable for the design, arrangement, and installation of a three-support oil-lubricated stern tube is formed. Compared to methods that fail to adequately consider stern tube design, leading to potential installation difficulties and subsequent operational failures, this method features a rational stern tube arrangement, feasible technology, and solid theoretical foundation. It can effectively avoid stern tube malfunctions and has been proven in actual ship testing, demonstrating strong practical significance. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the air-sealed three-support oil-lubricated split stern tube device of the present invention;

[0051] Figure 2 A schematic diagram of a three-support oil-lubricated stern tube;

[0052] Figure 3 A schematic diagram of the pipe support welded inside the stern tube;

[0053] Figure 4 A schematic diagram of the pipe support welded to the outside of the stern tube;

[0054] Figure 5 A schematic diagram of the piping arrangement for the forward bearing flange of the stern tube;

[0055] In the diagram: 1-Tail seal, 2-Rear shaft hub, 3-Rear bearing, 4-Rear shaft tube, 5-Diffuser, 6-Center shaft hub, 7-Center bearing, 8-Front shaft tube, 9-Front shaft hub, 10-Front bearing, 11-Tail seal, 12-Pipe joint, 13-Pipe support, 14-Pipe, 15-Manhole cover, 16-Epoxy resin, 17-Propeller shaft, 18-Process hole, 19-Tail seal oil tank, 20-Lubricating oil pump unit, 21-Stern tube lubricating oil tank, 22-Vacuum collection unit, 23-Air control unit, 24-Tail seal oil outlet, 25-Tail seal air inlet, 26-Tail seal air outlet, 27-Tail seal oil inlet, 28-Center bearing temperature sensor interface, 29-Rear shaft temperature sensor interface, 30-Stern tube oil inlet. Detailed Implementation

[0056] The specific embodiments of the present invention will be described in detail below with reference to the figures:

[0057] like Figures 1 to 5 As shown in the embodiment of the present invention, an air-sealed three-support oil-lubricated split stern tube device and its design method include a stern tube lubrication oil circulation system, an air sealing system, oil pipes and air pipes inside the stern tube (including support brackets and pipe joints), bearings, a segmented stern tube, and a shaft housing, etc.

[0058] (1) Overall layout: The three-support stern tubes are arranged from the stern to the bow as follows: stern seal 1, rear shaft hub 2, rear bearing 3, rear shaft tube 4, flow guide 5, middle shaft hub 6, middle bearing 7, front shaft tube 8, front shaft hub 9, front bearing 10, and bow seal 11. The bearing temperature sensor, air, lubricating oil and other pipelines are arranged inside the stern tube.

[0059] (2) Stern Seal: Stern seal 1 has four sealing rings, numbered 1#, 2#, 3#, and #3S. Sealing rings 1# and 2# face the stern to prevent seawater from flowing into the stern tube. Sealing rings 3# and #3S face the bow to prevent lubricating oil from flowing out of the stern tube. The chamber between 2# and 3# has a continuous air intake and an outflow pipe. If oil or water leaks, it can flow out through the pipe to prevent lubricating oil from leaking out of the ship.

[0060] (3) Rear, middle and front axle hubs: The tail axle frame can be made of cast steel, welded steel plate and segmented castings or forgings.

[0061] (4) Rear and front axle tubes: The axle tubes protect the stern shaft and hub, forming a tubular space with seals. The axle tubes are made of rolled steel plates, with the outer surface derusted, the interior coated with anti-rust oil, and the exterior sprayed with anti-rust paint to prevent seawater corrosion. Due to the air-sealed design, there cannot be any flared openings inside the axle tubes to prevent air from accumulating and being unable to escape, which would affect the function of the air seal.

[0062] (5) First seal: The stern seal has two sealing rings, numbered 4# and 5# respectively. The sealing rings face the stern to prevent lubricating oil from flowing into the tank. The stern pipe is equipped with a first seal oil tank with a high level alarm, and the circulation of lubricating oil is driven by the rotation of the shaft.

[0063] (6) Piping and supports inside the stern tube: The stern tube contains sensor tubes, oil tubes and air tubes. The pipes are connected by pipe joints and supported inside the stern tube by pipe supports.

[0064] (7) Rear, middle, and front bearings: The bearings are made of white alloy cast into the bearing assembly and pressed into the inner hole of the bearing housing. The outer circle of the bearing housing is machined with a 30mm diameter recessed plane at the contact position with the bearing adjusting screw to facilitate the fixing and operation of the bearing adjusting screw.

[0065] (8) Installation quality inspection: The stern tube, bearings and pipelines need to be inspected after installation.

[0066] (9) External piping system for oil, water, and gas: The stern tube device of the present invention requires the circulation of air, lubricating oil, and fresh water, therefore an external piping system is provided (see...). Figure 5 Includes: an air control unit for controlling the air pressure to the stern seal and stern tube lubricating oil tank, with a low flow alarm; a stern tube lubricating oil tank for supplying lubricating oil to the stern tube and lubricating oil pump unit, with high / low level alarms; a lubricating oil pump unit for supplying circulating lubricating oil to the stern tube and stern seal; and a venting and collection unit for collecting oil and water leaking from the stern seal, with an air flow controller and a high level alarm.

[0067] The (3) middle, rear, middle and front axle hubs:

[0068] (3.1) Hub dimensions: The dimensions of the stern hub, according to the classification society's specifications, shall not be less than the values ​​calculated using the following formulas:

[0069] Hub thickness: t = 0.33 × d3

[0070] Hub length: l = 3 × d s

[0071] In the formula: d s —Diameter of the tailpipe shaft at the hub, mm.

[0072] (3.2) Shaft hub design: The bearing is installed on the shaft hub through epoxy, so the design of epoxy casting holes and adjustment holes needs to be considered for the shaft hub.

[0073] (3.2.1) Epoxy Casting Hole: Within the length of the bearing installation area, drill a 35mm diameter epoxy injection port radially from below the hub and tap the thread (the lowest thread length is 35mm for easy connection to the epoxy casting fixture). Drill a 35mm diameter epoxy vent hole radially above the hub. Considering the relatively long epoxy casting space for the rear bearing, two epoxy vent holes can be drilled above the rear hub to ensure even epoxy distribution. The middle and front hubs only require one epoxy vent hole.

[0074] (3.2.2) Bearing mounting adjustment screw holes: Drill radial holes (tapping threads, for mounting M20 adjustment screws) at 45°, 135°, 225°, and 315° circumferentially within the length of the bearing installation area. The rear axle hub and center axle hub have 8 threaded holes tapped on two sides. The front axle hub only needs 4 holes tapped on one side, and the other end can be fixed with an internal adjustment flange.

[0075] (3.2.3) After the bearing is installed, the openings of the epoxy casting holes and adjusting screw holes on the outer surface shall be sealed by welding with a 50mm diameter round steel bar. The adjusting screws do not need to be removed.

[0076] (3.2.4) Hub shape design: Since the rear and middle hubs are in water, they can be made into a conical shape or welded with a flow guide to improve water flow.

[0077] (3.2.5) Shaft hub design: The bearing is installed on the shaft hub through epoxy, so the design of epoxy casting holes and adjustment holes needs to be considered for the shaft hub.

[0078] The rear and front axle tubes mentioned in (4):

[0079] (4.1) Rear Axle Tube Design: The rear axle tube connects the rear axle hub and the center axle hub. A 600mm diameter process hole is provided below the axle tube near the rear axle hub for the installation of oil, gas, and sensor pipeline connectors. After the pipelines are installed, they are repaired by welding with steel plates. A manhole cover is provided above the axle tube near the center axle hub. This manhole cover is used for pipeline installation and also facilitates the inspection of the axle and center bearing clearances when the ship enters dry dock. To reduce appendage drag, the manhole cover can be placed inside the fairing.

[0080] (4.2) Front shaft tube design: The front shaft tube connects the center shaft hub and the front shaft hub. A manhole cover is provided in the middle or at the required position to facilitate the maintenance of the propeller shaft.

[0081] (4.3) Welding Design: A welding bevel is reserved at the connection surface between the stern tube and the hub. A 30×8 steel ring can be spot welded at the outer diameter for easy welding. After the welding of the stern tube and hub is completed, the paint needs to be repaired.

[0082] The internal piping and supports of the stern tube mentioned in (6):

[0083] (6.1) Piping Design: There are a total of 7 pipes inside the stern tube, including oil pipes: the oil inlet and return pipes to the oil chamber before tail seal #3 / 3S#, and the air inlet and vent pipes to the air chamber before tail seal #2 / 3#. Sensor pipes include: the temperature sensor pipe to the aft bearing, the sensor pipe to the middle bearing, and the sensor pipe to the front bearing. Steel or copper pipes are used for the piping, minimizing unnecessary joints.

[0084] (6.2) Pipe support design: Pipe supports can be either welded inside the stern tube or welded outside the stern tube. Pipe supports are generally evenly distributed, with a span of 800-1000 mm.

[0085] The rear, middle, and front bearings mentioned in (7):

[0086] (7.1) Aft Bearing Design: The aft bearing housing has a rear flange. Before leaving the factory, screw holes and air holes are drilled on this flange according to the installation requirements of the tail seal. It is connected to the oil pipe and air pipe inside the stern tube through a right-angle connector. The lower part of the flange is the lowest point of the stern tube, where an oil drain plug is installed. To ensure no oil leakage, a sealing ring is installed below the drain plug. The aft bearing sensor tube is installed below the bearing, and the sensor is mounted thereon.

[0087] (7.2) Middle Bearing Design: The rear bearing housing has no flanges at the front and rear, but pipe passage holes are required for the tail sealing oil, air pipe, and rear bearing sensor. The middle sensor tube is set slightly below the bearing and the sensor is installed.

[0088] (7.3) Front bearing design: The front bearing has a front flange, and the front sensor tube is set off slightly below the bearing and the sensor is installed. The front bearing needs to be arranged reasonably because it needs to accommodate the tail sealing oil, air inlet and outlet pipes, the middle and rear bearing sensor tubes, the stern pipe oil inlet and return pipes, and the joints of these pipes.

[0089] Installation quality inspection as described in (8):

[0090] (8.1) Coaxiality inspection: The coaxiality of the fore, middle and aft stern bearings shall be re-measured according to standard GB / T34000-2016 after on-site installation and stern tube welding;

[0091] (8.2) Tightness test: After the stern tube, the oil circuit in the stern tube and the sensor protection tube are installed, a 0.2MPa tightness test shall be performed. The inside of the stern tube and each pipeline must be kept clean.

[0092] Installation quality inspection as described in (9):

[0093] (9.1) Normal conditions: Air enters the stern pipe air pipe through the air control unit via the pipeline where valve V1 is located, and flows to the stern seal, and then flows into the venting and collection unit. Lubricating oil enters the stern seal through the lubricating oil pump unit via valve V3 from the stern pipe oil tank, and another path enters the stern pipe through the pipelines of valves V4 and V5, and flows out of the stern pipe back to the stern pipe oil tank;

[0094] (9.2) Damaged tail seal #3: When the leakage of oil in the drain pipe increases, it indicates that the #3 seal may be damaged. At this time, close valves V3 and V8. No lubricating oil flows to the chambers of the #3 and #3S# seals. The pressure difference generated before and after the #3S# spare seal will start working.

[0095] (9.3) Air line cleaning: Fresh water can be used to clean the air line and chamber by selecting valve V3.

[0096] This embodiment is merely an exemplary description of the present invention and does not limit its scope of protection. Those skilled in the art can make partial changes to it, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A split-type stern tube device with air-sealed three-support oil lubrication, characterized in that, It includes the following components arranged sequentially from stern to bow: stern seal, aft shaft hub, aft bearing, aft shaft tube, fairing, center shaft hub, center bearing, front shaft tube, front shaft hub, front bearing and bow seal, stern tube and tube support, and external piping systems for oil, water and gas. The stern seal has four sealing rings. Sealing rings #1 and #2 face the stern to prevent seawater ingress, while sealing rings #3 and #3S face the bow to prevent lubricating oil leakage. An air cavity is formed between sealing rings #2 and #3, equipped with a continuous air inlet pipe and a vent pipe. The bow seal has sealing rings #4 and #5 and an oil tank with a high-level alarm. Sealing rings #4 and #5 face the stern to prevent lubricating oil from flowing into the tank. The stern tube contains a sensor tube, an oil pipe, and an air pipe, connected by pipe joints. The system is connected and supported within the stern tube by a pipe bracket; the external oil, water, and gas piping system includes: an air control unit for controlling the air pressure to the stern seal and stern tube lubricating oil tank, with a low flow alarm function; a stern tube lubricating oil tank for supplying lubricating oil to the stern tube and lubricating oil pump unit, with a high / low level alarm function; a lubricating oil pump unit for supplying circulating lubricating oil to the stern tube and stern seal; and a discharge collection unit for collecting oil and water leaking from the stern seal, with an air flow controller and a high level alarm function.

2. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The rear axle hub, middle axle hub, and front axle hub are all fixed with white alloy bearings by epoxy casting. Each axle hub has an epoxy injection port below the bearing mounting section and an epoxy vent above it. The rear axle hub has two vents, while the middle axle hub and the front axle hub each have one vent.

3. The air-sealed three-support oil-lubricated split stern tube device according to claim 2, characterized in that, Each axle hub has radial adjustment screw holes at 45°, 135°, 225°, and 315° circumferentially for installing adjustment screws; the rear axle hub and the middle axle hub each have 4 screw holes on both ends of the bearing, for a total of 8; the front axle hub has only 4 screw holes on one end, and the other end is fixed and adjusted inside the compartment through the bearing's own flange.

4. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The rear axle tube connects the rear axle hub and the center axle hub. It has a 600mm diameter process hole near the lower part of the rear axle hub for installing oil pipes, air pipes and sensor pipe joints. After installation, it is repaired by welding with steel plate. A manhole cover is provided near the upper part of the center axle hub for pipeline installation and for checking the bearing clearance when the ship enters the dry dock.

5. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that... The front axle tube connects the central shaft hub and the front axle hub, and a manhole cover is provided in the middle of the tube or at a required position for inspecting the propeller shaft.

6. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The stern tube is equipped with seven functional pipelines, including: an oil inlet pipe and an oil return pipe for the stern seal 3# / 3S# oil chamber, an air inlet pipe and an air vent pipe for the stern seal 2# / 3# air chamber, and temperature sensor pipes leading to the rear bearing, middle bearing, and front bearing, respectively; the pipelines are connected by pipe joints and supported by pipe supports welded to the inner or outer wall of the stern tube, with a support span of 800-1000mm.

7. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The rear bearing has a rear flange with pre-drilled screw holes and air holes that match the tail seal, and is connected to the oil pipe and air pipe inside the stern tube via a right-angle joint; the bottom of the flange is equipped with an oil drain plug with a sealing ring; a sensor tube is located below the rear bearing and a temperature sensor is installed.

8. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The rear bearing housing of the intermediate bearing has no front or rear flanges. A through hole is provided on the rear bearing housing for the tail sealing oil pipe, air pipe and rear bearing sensor pipe to pass through. A sensor pipe and temperature sensor are installed on the lower part of the intermediate bearing.

9. The air-sealed three-support oil-lubricated split stern tube device according to claim 1, characterized in that, The front bearing has a front flange, with a sensor tube and temperature sensor installed slightly below it; the front flange centrally arranges the tail seal oil / gas inlet / outlet pipe, the middle and rear bearing sensor tube, the stern pipe inlet / outlet oil pipe and its connectors, realizing the integration of pipeline interfaces.

10. A design method for a stern tube device according to any one of claims 1-9, characterized in that, include: (1) Rear, middle and front axle hub design (1.1) Hub size design: Based on the classification society specifications for the stern hub dimensions, the values ​​are calculated using the following formulas: Hub thickness: t = 0.33 × d³, Hub length: l = 3 × d s In the formula: d s —Diameter of the tailpipe shaft at the hub, mm; (1.2) Shaft hub design: The bearing is installed on the shaft hub with epoxy resin. The shaft hub needs to consider the design of epoxy casting holes and adjustment holes. After the bearing is installed, the openings of the epoxy casting holes and adjustment screw holes on the outer surface are sealed by welding with 50mm diameter round steel. The shaft hub is made into a conical shape or welded with a flow guide to improve water flow. (2) Rear and front axle tube design: (2.1) Rear Axle Tube Design: The rear axle tube connects the rear axle hub and the center axle hub. A 600mm diameter process hole is provided below the axle tube near the rear axle hub for the installation of oil, gas, and sensor pipeline connectors. After the pipeline installation is completed, it is repaired by welding with steel plates. A manhole cover is provided above the axle tube near the center axle hub. This manhole cover is used for pipeline installation and also facilitates the inspection of the shaft and center bearing clearance when the ship enters dry dock. In order to reduce appendage drag, the manhole cover can be placed inside the fairing. (2.2) Front shaft tube design: The front shaft tube connects the center shaft hub and the front shaft hub. A manhole cover is provided in the middle or at the required position to facilitate the maintenance of the propeller shaft. (2.3) Welding design: A welding bevel is reserved at the connection surface between the stern tube and the hub. A 30×8 steel ring can be spot welded at the outer diameter to facilitate welding. After the welding between the stern tube and the hub is completed, the paint needs to be repaired. (3) Design of stern tube piping and supports: (3.1) Piping Design: There are a total of 7 pipes inside the stern tube, including oil pipes: the oil inlet and return pipes to the oil chamber before tail seal #3 / 3S#, and the air inlet and vent pipes to the air chamber before tail seal #2 / 3#. Sensor pipes include: the temperature sensor pipe to the aft bearing, the sensor pipe to the middle bearing, and the sensor pipe to the front bearing. Steel or copper pipes are used for the piping, minimizing unnecessary joints. (3.2) Pipe support design: The pipe supports adopt the type of welding inside the stern tube and the type of welding outside the stern tube. The pipe supports are evenly distributed and the span is 800-1000mm. (4) Design of rear, middle and front bearings: (4.1) Aft Bearing Design: The aft bearing housing has a rear flange. Before leaving the factory, screw holes and air holes are drilled on this flange according to the installation requirements of the tail seal. It is connected to the oil pipe and air pipe inside the stern tube through a right-angle connector. The lower part of the flange is the lowest point of the stern tube, where an oil drain plug is installed. To ensure no oil leakage, a sealing ring is installed below the drain plug. The aft bearing sensor tube is installed below the bearing, and the sensor is mounted thereon. (4.2) Middle Bearing Design: The rear bearing housing has no flanges at the front and rear, but pipe passage holes are required for the tail sealing oil, air pipe, and rear bearing sensor. The middle sensor tube is installed slightly below the bearing, and the sensor is mounted there. (4.3) Front bearing design: The front bearing is equipped with a front flange, and the front sensor tube is set and the sensor is installed on the lower part of the bearing; and the tail sealing oil and gas inlet and outlet pipes, the middle and rear bearing sensor tubes, the stern pipe oil inlet and return pipes, and the pipe joints are reasonably arranged at the front bearing. (5) Installation quality inspection: (5.1) Coaxiality inspection: The coaxiality of the fore, middle and aft stern bearings shall be re-measured according to standard GB / T34000-2016 after on-site installation and stern tube welding; (5.2) Tightness test: After the stern tube, the oil circuit in the stern tube and the sensor protection tube are installed, a 0.2MPa tightness test shall be performed. The inside of the stern tube and each pipeline must be kept clean.

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