JP2015227726A - Seal arrangement for propeller shaft and method for sealing propeller shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To create a new shaft sealing system, particularly suitable for limited spaces, which maintains the optimal conditions at a lip seal and maximizes the service life of the seal.SOLUTION: The invention relates to an arrangement and method for sealing a propeller shaft of a ship using sealing 26. The sealing comprises a group of lip seals 30, 32, 34, 36, arranged consecutively in the direction of the propeller shaft so that a chamber 38, 40, 42 is created between adjacent lip seals. The pressure of a first chamber 38 on the propeller 6 side is close to the pressure of the surrounding water at the propeller shaft level, and the pressure of a second chamber 42 furthest from the propeller is adjusted to a fixed value that is lower than the pressure of the first chamber. The pressure of a third chamber located between the first chamber and the second chamber is adjustable by a pressure regulation device to a value between the pressure values of the first chamber and the second chamber by adjusting the pressure loss caused by the flow of a liquid medium.

Description

  The invention relates to a device for sealing a propeller shaft of a ship as defined in the premise of claim 1 and to a method for sealing the propeller shaft of a ship as described in the premise of claim 6.

  A propeller of a ship or a large ship corresponding thereto is supported by a main body of the ship or a propulsion device by a bearing. The propeller shaft has a shaft seal device between the main body and the shaft to prevent ambient water from entering the main body, and on both sides of the bearing to prevent bearing lubricant from leaking into the water or into the main body. It has a bearing seal device. The shaft seal must maintain its sealing characteristics for as long as possible because reliability is paramount for the operation of the propulsion system and the reliability of the bearings supporting the shaft. The shaft seal is below the water surface, meaning that hydrostatic pressure is applied to the shaft seal. The shaft seal is composed of several lip seals and a seal chamber between them. This device is designed to reduce the pressure in the chamber by pumping air into the chamber or by connecting the chamber to an oil tank and utilizing gravity to maintain the seal chamber pressure at the desired level by the hydrostatic pressure of the oil. In another way of adjusting the pressure, the total pressure difference is distributed to the parts. In particular, in electrical ladder propeller systems where the available space is very limited, all additional devices associated with the shaft sealing system inherently create space problems when using existing shaft sealing systems. .

  The service life of a shaft seal is affected by many factors that need to be at the best possible level. The most important factors that affect seal performance and service life are the lip seal pressure differential, the temperature of the seal-to-shaft contact surface, the peripheral speed of the shaft outer surface, and the lubricant chemicals that affect the seal material. It is an influence. The coupling effect of these factors must be at a sufficient and acceptable level that the seal can achieve the maximum usable life by its design.

  Environmentally friendly oils, i.e. biodegradable oils, have properties that are more susceptible to factors such as operating temperature, and therefore further requirements are set for their use.

  A solution is known from US Pat. No. 5,683,278 that uses compressed air to regulate the pressure in the chamber between seals.

  It is an object of the present invention to create a new shaft sealing system that is particularly suitable for confined spaces that maintains optimal conditions in the lip seal and maximizes the usable life of the seal. The device according to the invention is characterized by the features described in the characterizing part of claim 1. The method according to the invention is characterized by the features described in the characterizing part of claim 6. Other preferred embodiments of the invention are characterized by the features defined in the dependent claims.

  Embodiments in accordance with the present invention extend the usable life of the seal by optimizing operating conditions. By adjusting the pressure in the internal chamber of the sealing system, the pressure differential of the lip seal is kept as low as possible and is optimal for the usable life over the entire operating life of the system. The heat output generated at the seal is transferred by the circulating oil to the frame of the ladder propeller device and further to the sea water, keeping the temperature at the seal sufficiently low.

  The media used to pressurize the internal chamber cools the seal boundary to a temperature range that is optimal for sealing performance. Since biodegradable oils are particularly sensitive to high temperatures, the cooling effect is more effective, especially for the use of biodegradable oils. The solution therefore provides better conditions for the use of environmentally friendly oils.

  In applications where the shaft sealing is in the ship's body or propulsion device, away from the immediate vicinity of the shaft and body, the sea water around the ship does not necessarily sufficiently cool the seal. Embodiments according to the present invention allow sufficient cooling reliably and at low cost.

  The present invention makes it possible to generate optimal conditions for the seal in changing operating environments. As the ship draft changes, the pressure in the seal chamber is adjusted so that the pressure difference between the lip seals is as low as possible. As the temperature of the environment, especially the temperature of the seawater around the propeller device, changes, the temperature of the sealing contact surface can be kept as low as possible. Furthermore, when the pressure change is due to ship operation, the pressure in the chamber can be adjusted according to the pressure of the surrounding seawater. This mainly relates to a CRP drive (a counter-rotating propeller drive) in which the pressure affecting the axis changes according to the operating conditions of the ship.

  Embodiments according to the present invention provide advantages with respect to manufacturing and manufacturing engineering. The same system is suitable for many types and even all types of ships. Embodiments according to the present invention can use standard seals, ensuring usability and quality. The solution requires fewer parts, lower costs, and easier to install in the limited space of the ladder propeller device. The system can be designed in a modular configuration, which provides advantages in assembly and maintenance phases and raw material acquisition. The system also includes measurement and adjustment devices that facilitate more effective condition monitoring, creating better preconditions for life cycle management.

  The present invention will be described in more detail below using specific embodiments with reference to the accompanying drawings.

The figure which shows the propeller system with which the sealing apparatus by this invention was applied. The figure which shows the sealing apparatus by this invention.

  FIG. 1 is a partial schematic view of a ship propulsion device 2 comprising a propulsion device in which the device according to the invention is implemented. The propulsion device is a steering propeller device attached to the ship body using a slewing bearing device. Such a steering propeller device is known, for example, under the trade name AZIPOD (registered trademark), which is a trademark owned by ABB Oy. An electric motor 8 for operating the propeller 6 is attached inside the casing 4 of the propulsion device 2. In the present embodiment, the electric motor 8 is a synchronous motor having an exciter 12 attached to the propeller shaft 10 by a known method. Both ends of the propeller shaft 10 are supported by the casing 4 of the propulsion device 2. FIG. 1 shows only the bearing 14 at the end on the side of the propeller 6 provided with roller bearings. Another bearing is used at the other end of the electric motor 8 in a known manner.

  The casing 4 of the propulsion device includes an intermediate compartment 16 on the side of the propeller 6 between the propeller 6 and the bearing 14. The wall of the intermediate compartment 16 includes a wall 18 on the propeller side, an outer peripheral portion 20 at the end of the propulsion device, and a support structure 22 for the bearing 14. The propeller shaft 10 passes through the center of the intermediate compartment 16. At the bearing end of the intermediate compartment 16 is a bearing outer oil seal 24 that prevents the bearing lubricant from leaking out of the bearing housing. Correspondingly, there is a bearing inner oil seal 25 at the end of the bearing 14 on the motor side. A shaft sealing 26 is fitted into the propeller end within the intermediate compartment 16 to prevent ambient water from entering the intermediate compartment 16. Thus, the intermediate compartment 16 is completely sealed and under normal operating conditions there is no liquid. The shaft sealing 26 is fitted in a closed intermediate compartment, allowing the replacement of the sealing in the compartment.

  FIG. 2 is a schematic diagram of the details of the shaft sealing 26 and the pressure and lubrication system. The shaft sealing 26 is comprised of four lip seals 30, 32, 34 and 36 that are fitted in the direction of the shaft 10 so that the chambers 38, 40 and 42 are between adjacent lip seals. . The pressure outside the lip seal 30 is the pressure generated by the ship's draft, for example 0.4-1.0 bar. The first chamber 38 closest to the propeller 6 is limited by the lip seals 30 and 32. The pressure on both sides of the contact surface of the lip seal 30 is basically the same. The pressure in the first chamber 38 is always measured by the sensor 44. This measurement data is sent to the control device 78. The programming of the control device 78 includes a PI control device 66, an error variable management unit 64, and a reference pressure measurement data processing unit 46. The controller utilizes a software implementation, which is an inexpensive solution that does not use separate components. The first chamber is filled with water or oil, the pressure of which basically corresponds to the pressure of the surrounding water at the axis. The second chamber 42 of the shaft ceiling 26, furthest away from the propeller, is between the lip seals 34 and 36. The pressure in the second chamber is slightly higher than the pressure of air in the intermediate compartment 16. The pressure in the second chamber is, for example, about 0.1 bar, so that there is a pressure difference between the contact surfaces of the lip seal 36. The second chamber 42 is connected by a pipe 48 to an oil tank 50 that stably maintains the pressure of the second chamber at a rated value using gravity.

  Between the first chamber and the second chamber is a third chamber 40, bounded by lip seals 32 and 34, with the contact surface facing the shaft. The third chamber 40 is connected to the oil tank 50 using a pipe 52, a pump 54 and a pipe 56. The pressure in the third chamber 40 is constantly adjusted by the motor 58 that operates the pump 54. The motor is controlled by a frequency converter 60. Using a pressure regulating device, the pressure in the third chamber 40 is adjusted between the first chamber and the second chamber so that the pressure difference between the contact surfaces of the lip seals 32 and 34 is approximately the same. Keep the value corresponding to the difference. For example, when the pressure in chamber 42 is 0.1 bar and the pressure in first chamber 38 by draft is 0.7 bar, the pressure in third chamber 40 is about 0 using pump 54. Adjusted to 4 bar.

  The pressure in the third chamber 40 is measured by the sensor 62. The measurement data is sent to the control device 78. The PI controller 66 of the control device calculates a rotational speed instruction to be sent to the frequency converter 60 based on the pressure measurement data from the sensors 44 and 62. The second and third chambers are connected to the tank by drains 68 and 70 through valve 72. A choker 74 is installed in the drain pipe 70 for flow regulation. The choker is designed according to the maximum temperature of the seal chamber. Therefore, the pressure regulating device of the present embodiment includes the pump 54 and the flow regulating choker 74. Due to the flow produced by the adjustable pump 54, the operation of the pressure regulating device is based on the pressure loss produced by the choker 74 or another flow valve. The pressure loss generated by the choker depends on the oil flow rate. Thus, the desired pressure in the chamber 40 is achieved by adjusting the rotational speed of the pump with a frequency converter. Downstream of the pump 54, an oil flow passes through a heat exchanger 76 that allows an effective cooling function to be achieved as a by-product of pressure regulation with a simple configuration. When the oil is warm and the viscosity is low, the desired pressure in the chamber 40 is achieved only by a large flow rate. A large flow rate makes the cooling power appropriate. When the oil is cold, the desired pressure can be achieved with very low flow rates. This means that already cold oil is not unnecessarily cooled. The heat exchanger can comprise, for example, a box on the frame of the propulsion device and transfers heat directly to the surrounding sea water. Alternatively, the oil tank can be placed in the propulsion device in an advantageous manner so that the tank is in contact with the surrounding sea water.

  The above adjustment system effectively maintains the pressure and temperature of the shaft sealing chamber within the rated values, allowing the longest service life. At the same time, it is possible to use biodegradable oil without impairing the sealing function.

  The intermediate compartment solution allows all seals to be replaced without placing the ship in the dry dock, making maintenance and repair work easier.

  As ship draft and weather conditions change, the lip seal pressure differential is maintained at the lowest possible level in a controlled manner. Since the actual pressure of the surrounding seawater is always measured, the pressure change due to the movement and operation of the ship, which is an important factor of the CRP drive, is also taken into account.

  The pressurizing device according to the present invention can be applied to most shaft sealing devices regardless of the sealing structure. The device is suitable for various ship types and all draft levels without having to adjust the height of the oil tank when the draft changes.

  In summary, the device requires fewer pipes, tanks, level detectors and control valves, coupled with a simple mechanical structure, and is less expensive than conventional systems.

  The apparatus includes built-in pressure and pressure level measurement and monitoring that can be used for condition monitoring purposes.

  In an alternative embodiment, the pump generates a constant flow rate and the pressure in the seal chamber 40 is adjusted so that the PI controller 66 operates an electrical flow valve (not shown) instead of a frequency converter. Can be configured.

  In the above, the invention has been described using specific embodiments. However, the description should not be construed as limiting the scope of patent protection, and embodiments of the invention may be varied within the scope of the appended claims.

Claims (6)

  A device for sealing a propeller shaft (10) of a ship by means of a sealing (26), said propeller shaft being supported on said ship body or propulsion device by means of a bearing (14), said sealing (26) being adjacent A group of lip seals (30, 32, 34, 36) arranged continuously in the direction of the propeller shaft (10) so that a seal chamber (38, 40, 42) is formed between the lip seals. A second seal farthest from the propeller (6), wherein the pressure in the first seal chamber (38) on the propeller (6) side is essentially close to the pressure of sea water around the level of the propeller shaft (10) The pressure in the chamber (42) is adjusted to a constant value that is essentially lower than the pressure in the seal chamber (38) on the propeller side, and the device is Adjusting the pressure loss caused by the flow rate of the liquid acting as a medium, the pressure in the third chamber (40) between 8) and the second chamber (42) furthest from the propeller By means of a pressure regulating device that is adjustable to a value between the pressure values of the first chamber (38) and the second chamber (42).   The pressure regulating device is based on a pressure loss generated by a choker (74) or another flow control valve, the pressure loss being due to a flow generated by an adjustable pump (54). The apparatus according to claim 1.   The apparatus according to claim 1, wherein the pressure regulating device is based on a pressure loss produced by another pressure regulating valve due to a constant flow produced by a fixed discharge pump.   4. The device according to claim 1, wherein the same medium from one oil tank (50) circulates in two or more sealing chambers (38, 40, 42).   Device according to any one of the preceding claims, characterized in that the medium used for pressure regulation passes through a heat exchanger (76) using a flow for cooling purposes.   A method for sealing a propeller shaft (10) of a ship by means of a sealing (26), said propeller shaft being supported by said ship body or propulsion device by means of a bearing (14), said sealing (26) being adjacent A group of lip seals (15, 32, 34, 36) that are continuously fitted in the direction of the propeller shaft (10) such that a seal chamber (38, 40, 42) is formed between the lip seals (30, 32, 34, 36). 30, 32, 34, 36), and the pressure in the first seal chamber (38) on the side of the propeller (6) is basically close to the pressure of the water around the propeller shaft level and farthest from the propeller. The pressure in the two seal chambers (42) is maintained at a constant value essentially lower than the pressure in the seal chamber (38) on the propeller side, and the chamber (3 on the propeller side) ) And the second chamber (42) farthest from the propeller, the pressure in the third chamber (40) is the pressure in the first chamber (38) and the second chamber (42). A method characterized in that it is always adjusted to a value between values.

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