Sealing system for sealing a marine propeller shaft

Abstract

The invention relates to sealing system (1) for sealing a marine propeller shaft (3), the sealing system comprising; - a void chamber (2) arranged between lip seal systems (4, 5) for collecting leakage 5 from the lip seal systems and having a void chamber inlet (6) and outlet (7) for allowing air flow through the void chamber, - an air supply line (8) fluid coupled with a first flow path (11) including the void chamber for maintaining an overpressure in the void chamber, - a leakage collection system (9) fluid coupled with the void chamber outlet, and wherein the leakage collection system comprises a tank (10) that is fluid coupled with the air supply line through a second flow path (12) different from the first flow path (11) and in parallel with the first flow path.

Description

[0001] Sealing system for sealing a marine propeller shaft

[0002] BACKGROUND

[0003] The current disclosure relates to a sealing system for sealing a marine propeller shaft, the sealing system comprising a void chamber arranged between lip seal systems for collecting leakage from the lip seal systems and having a void chamber inlet and outlet for allowing air flow through the void chamber. Examples of systems having propeller shafts where the sealing system of the current disclosure can be applied include propulsion systems of a vessel, dredging pumps, as well as tidal turbines.

[0004] Sealing a marine propeller shaft using lip seal systems is well known. For instance, EP0671321B1 concerns a sealing assembly for sealing the end of a propeller shaft stem tube of a ship, directed towards the screw, said sealing assembly comprising sealing rings provided with a lip extending from the body of the ring and resiliently pressed against a bush mounted on the screw shaft. Between two sealing rings lies a chamber to which biodegradable grease is supplied.

[0005] A disadvantage of the sealing assembly is that grease or oil is discharged to the water outboard. That is undesirable and as a minimum requirement, the lubricant is an expensive biodegradable type.

[0006] A sealing product is known as “Supreme Ventus” which is a so-called air-type sealing system. The product has a constant air flow through a void chamber between opposite lip seals. The void chamber prevents an oil-to-water interface and therefore guarantees zero emissions of oil for seagoing vessels. The air flow drains any leakage from the void chamber into a monitoring tank. In addition, the void chamber enables to minimize pressure over a lip seal and therefore improves product service life of the lip seal.

[0007] SUMMARY

[0008] The object of the current invention is to improve an air type sealing system in that collection of leakage from the void chamber is improved.

[0009] Another object of the current invention is to provide an air type sealing system wherein a known problem is at least partly solved.

[0010] Another object of the current invention is to provide an alternative air type sealing system. Therefore, the invention provides a sealing system for sealing a marine propeller shaft, the sealing system comprising; a void chamber arranged between lip seal systems for collecting leakage from the lip seal systems and having a void chamber inlet and outlet for allowing air flow through the void chamber, an air supply line fluid coupled with a first flow path including the void chamber for maintaining an overpressure in the void chamber, a leakage collection system fluid coupled with the void chamber outlet, and wherein the leakage collection system comprises a tank that is fluid coupled with the air supply line through a second flow path different from the first flow path and in parallel with the first flow path.

[0011] Fluid coupling the tank with the air supply line through a second flow path different from the first flow path and in parallel with the first flow path enables to empty the tank by using the same air supply line to displace the contents from the tank. This also enables to transport leakage to an increased height position; in fact, any desired height position is possible depending on the operating pressure of the air supply line. This is all the more important for larger ships having large thrusters. Normally, leakage will be collected inside a monitoring tank which is located at the control room of a ship. This is usually at a height of up to 3-4 meters from the stern. However, with larger ships and with large thrusters, placing this monitoring tank at a height of 3-4 meters is not possible. The current invention enables placing the current monitoring tank at greater heights and to drain the leakage to greater heights of for example about 10 meters above the sealing system or even more, in order to suit the needs of larger ships.

[0012] The second flow path being in “parallel” with the first flow path here means that the first flow path and the second flow path branch off from the air supply line and both end up in the leakage collection system.

[0013] The void chamber is flown through with air that is supplied by the air supply line. The supply line determines the pressure in the void chamber and the air itself functions as transport medium to transport the leakage from the lip seal systems from the void chamber to the tank. The void chamber is normally an “air chamber”. Air is a suitable medium for pressurizing the chamber and to transport any leakage out of the void chamber, however another suitable gaseous medium is conceivable as well.

[0014] The void chamber inlet is normally arranged at an upside of the void chamber while the outlet of the void chamber is normally arranged at a bottom of the void chamber. This way, gravity assists the air flow through the void chamber in transporting leakage away from and out of the void chamber.

[0015] The leakage from the lip seal systems is a mixture of oil and seawater. The leakage needs to be collected and processed as waste.

[0016] In an embodiment of the sealing system according to the invention, the first flow path comprises a flow restricting member for restricting the flow of air through the void chamber. The flow restricting member ensures correct functioning of the lip sealing system while enabling to operate the supply line at different pressures. The flow restricting member is arranged in the first flow path upstream with respect to the void chamber. This improves functioning of the flow restrictor since upstream with respect to the void chamber is the side of the void chamber that is less likely to pollute. The flow restricting member may comprise an adjustable flow restrictor to improve an operational window of the sealing system.

[0017] In an embodiment of the sealing system according to the invention, the second flow path comprises a control valve to allow or stop flow of air through the second flow path. The control valve enables to couple or decouple the leakage collection system, in particular the tank thereof, with the air supply line as desired. This in turn makes it possible to empty the tank in a controlled way by displacing the oil / water mixture using the pressurized air from the air supply line. Directly coupling the tank to the air supply line through the second flow path is referred to as “drain mode”, since the tank is emptied, and the leakage is transported to a monitoring tank in a control room of the vessel or any other suitable place. The control valve can be any suitable valve that can allow or stop flow of air, like for example a one-way valve, a pressure-controlled valve, and an electronically controlled valve.

[0018] The second flow path in particular comprises a pressure-controlled valve that is normally closed. The control valve in the second flow path being a pressure control valve, enables to control the valve with an operating pressure of the pressurized air in the air supply line itself. This reduces the number of supply and control lines to for example a drive that is running the marine shaft. Reducing the number of lines is important, in particular when a drive is steerable and / or adjustable in depth like a thruster.

[0019] In an embodiment of the sealing system according to the invention, the second flow path comprises a one-way valve. This all the more enables to have a robust drain mode and helps to avoid pollution of the second flow path from the contents of the tank. Preferably, in this embodiment, the one-way valve is arranged between a pressure-controlled valve of the second flow path and the tank, however any suitable arrangement is conceivable.

[0020] In an embodiment of the sealing system according to the invention, the first flow path comprises a control valve system to couple or decouple the leakage collection system and the void chamber outlet. The first flow path including a control valve system enables to separate the void chamber from the tank, in particular during drain mode. This is important because the functioning of the sealing system is business critical. The control valve can be any suitable valve that couples or decouples the leakage collection system and the void chamber outlet, like for example a one-way valve, a pressure-controlled valve, and an electronically controlled valve.

[0021] In an embodiment of the sealing system according to the invention the control valve system of the first flow path comprises a normally open pressure controlled valve, wherein respective control input connections of the first flow path normally open pressure controlled valve and the second flow path normally closed pressure controlled valve are both fluid coupled to the air supply line. This enables to control both respective valves simultaneously. In addition, this all the more reduces the number of supply and control lines. In particular, the respective control input connectors of the first flow path normally open pressure-controlled valve and the second flow path normally closed pressure controlled valve are series coupled. This all the more assures simultaneous control of both the valves and also this guarantees a proper functioning of the sealing system including collecting of the leakage. However, a parallel coupling is conceivable as well, as long at the valves are operated simultaneously. In the technical field, control input or control lines is also referred to as “pilot lines”.

[0022] In an embodiment of the sealing system according to the invention, the leakage collection system comprises a buffer for temporarily collecting leakage from the lip seal systems, and wherein the buffer is included in the first flow path and upstream with respect to the tank. The buffer enables a continuous operation of the sealing system wherein leakage from the void chamber is collected even when the tank is decoupled from the void chamber and the sealing system is in drain mode. In particular, the control valve included in the first flow path is arranged between the buffer and the tank. This enables a direct coupling between the buffer and the void chamber and therefore leakage from the void chamber can always be collected. To put it differently, the void chamber outlet is directly coupled with the buffer. In an embodiment of the sealing system according to the invention, the leakage collection system is at least partly arranged below the void chamber. In particular the tank and or the buffer are at least partly arranged below the void chamber. Therefore, gravity assists the flow of pressurized air through the air camber in transporting leakage from the void chamber to the leakage collection system. It is however conceivable that the leakage collection system is at least partly arranged above the void chamber, like for instance up to 2.5 meters above the void chamber. In that case however, flow of pressurized air through the void camber transports leakage from the void chamber to the leakage collection system and has to overcome gravitation.

[0023] In an embodiment of the sealing system according to the invention, the void chamber comprises a check valve. The check valve enables to maintain a pre-determined overpressure in the void chamber compared to the water column pressure that the check valve is exposed to, and independent of the depth wherein the sealing system is operating. The predetermined overpressure is about 0,1 bar however it will be clear that any suitable overpressure is conceivable.

[0024] Therefore, the invention provides a marine propulsion system comprising a sealing system according to the invention. The sealing system according to the invention is in particular useful in a marine propulsion system comprising a height adjustable propeller unit, wherein the void chamber and tank move in unity and in correspondence with the height adjustable propeller unit. The sealing system according to the invention is in particular useful in combination with a height adjustable propeller unit because the sealing system has an improved head, also conveying height, since the pressurized air in the air supply line can transport the collected leakage to an increased height position.

[0025] Therefore, the invention provides a use of a sealing system according to the invention, comprising one of the following steps;

[0026] - operating the air supply line at a pressure below a predetermined reference pressure and simultaneously collecting leakage from the lip seal systems to the tank, and

[0027] - operating the air supply line at a pressure above the predetermined reference pressure and simultaneously emptying the tank by displacing collected leakage in the tank with pressurized air from the air supply line. The pressure above the predetermined reference pressure for emptying the tank is between 4 - 8 bar like for example about 6 bar. The about 6 bar may result in a possible head of more than 10 meters. It will be clear that any suitable pressure is conceivable, depending on a required head.

[0028] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached schematic drawings, in which; figure 1 shows a side view a sealing system according to the prior art; figure 2 shows a side view of a first embodiment of a sealing system according to the invention; figure 3 shows a side view of a second embodiment of a sealing system according to the invention; and

[0031] Figures 4 A, 4B and 4C show the first embodiment of figure 2 in different perspectives.

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] Figure 1 shows a sealing system according to the prior art. The sealing system 1 is configured for sealing a marine propeller shaft 3. The sealing system 1 extends around the axis 19 of the propeller shaft 3 and contacts the outer surface of the shaft 3 in a sealing manner. The sealing system comprising a lip sealing system 4, 5 that is known per se. The sealing system comprises two opposite lip seals 4, 5. A void chamber 2 is arranged between the two opposite lip seals 4, 5 of the lip sealing system 4, 5. The void chamber 2 functions to set a pressure across the lip seals 4, 5 and for collecting leakage from the lip seal system. Therefore, the void chamber has a void chamber inlet 6 and outlet 7 for allowing air flow through the void chamber. The leakage collection system 9 comprises a tank 10. The tank holds the oil and water mixture that is collected from the lip sealing system 4, 5 through the void chamber 2. In order to assist in setting the pressure in the void chamber 2, the void chamber comprises a check valve 13. The check valve 13 vents air 25 to outside the void chamber 2, normally to a body of water. The check valve 13 vents air in case the pressure in the void chamber 2 exceeds a predetermined maximum pressure setting.

[0034] Now turning to figure 2 that shows a first embodiment of a sealing system 1 according to the invention. In principle, mainly differences with the sealing system of fig. 1 will be clarified. The sealing system comprises an air supply line 8 for providing pressurized air to the void chamber 2. Therefore, the void chamber 2, in particular the inlet 6 of the void chamber 2, is fluid coupled with the air supply line 8. The inlet 6 is coupled with the supply line through a first flow path 11 for maintaining an overpressure in the void chamber. In other words, the void chamber is included in the first flow path, or in other words, is part of the first flow path. The overpressure with respect to the seawater at the operating height of the sealing system 1 is for example about 0,1 bar. Therefore, the check valve 13 vents air 25 to outside the void chamber 2.

[0035] The sealing system comprises a leakage collection system 9. The leakage collection system 9 is fluid coupled with the void chamber outlet 7 for collecting leakage of water and / or oil from the void chamber 2. The leakage collection system 9 comprises a tank 10. The tank holds the oil and water mixture that is collected from the lip sealing system 4, 5 through the void chamber 2. The tank is fluid coupled with the air supply line 8. The tank is fluid coupled with the air supply line 8 through a second flow path 12. Therefore, pressurized air in the air supply line is able to force the mixture out of the tank 10 to empty the tank. The mixture from the tank 10 is transported to a monitoring tank that is not shown. Such a monitoring tank is normally arranged in a control room of a vessel and is known per se. A monitoring tank can be used to monitor the total amount and composition of the collected leakage over a certain period of time. Subsequently, the contents of the monitoring tanks are transferred to a so-called dirty oil tank (not shown) for further processing as waste. This is quite common for a marine vessel. The second flow path 12 is different from the first flow path 11. The second flow path 12 is in parallel with the first flow path 11. Therefore, it is possible to empty the tank 10 without effecting the functioning of the void chamber 2. The second flow 12 path includes a control valve 15. The control valve is configured and arranged to allow or stop flow of air through the second flow path 12. In this case, the control valve 15 in the second flow path 12 is a pressure control valve. The first flow path 11 includes a flow restricting member 14. The flow restricting member is configured for restricting the flow of air through the void chamber 2. The flow restricting member 14 ensures correct functioning of the lip sealing system 4, 5. The flow restricting member 14 ensures correct functioning of the lip sealing system 4, 5 even in case the pressure of the air in the air supply line 8 is increased to empty the tank 10. In this case, the flow restricting member 14 comprises an adjustable flow restrictor.

[0036] As shown, the second flow path 12 is in parallel with the first flow path 11 because both the first and second flow path start at the air supply line 8 and end at the tank 10.

[0037] In this case, the tank 10 is arranged below the void chamber 2. Here, the tank 10 is arranged directly below the void chamber 2.

[0038] As shown in fig. 3, the leakage collection system 9 comprises a buffer 18. The buffer 18 is separate and different from the tank 10. The buffer 18 is configured for temporarily collecting leakage from the lip seal systems 4, 5. The buffer 18 is able to collect leakage from the lip seal systems 4, 5 during emptying of the tank 10. Emptying of the tank 10 can take for example 1 minute and can be done every 30 minutes however these periods of time are of course depending on the volume of the tank 10 as well as on the dimensions of the sealing system 1 and the pressure applied to the air supply line 8. The buffer 18 is included in the first flow path 11. The buffer 18 is arranged upstream with respect to the tank 10. Here, in particular, the void chamber outlet 7 is directly coupled with the buffer 18.

[0039] The buffer 18 is arranged below the void chamber 2. In this case, the buffer 10 is arranged directly below the void chamber 2.

[0040] The first flow path 11 includes a control valve 17. The control valve 17 functions to couple or decouple the leakage collection system 9 and the void chamber outlet 7. In this case, the control valve 17 in the first flow path 11 is a pressure control valve that is normally open.

[0041] As shown in fig. 3, the control valve 17 included in the first flow path 11, is arranged between the buffer 18 and the tank 10. It is also conceivable to arrange the control valve 17 directly between the void chamber outlet 7 and the tank 10. In other words, the control valve 17 can also be applied without implementing a buffer 18. The second flow 12 path includes a control valve 15. The control valve is configured and arranged to allow or stop flow of air through the second flow path 12. In this case, the control valve 15 in the second flow path 12 is a pressure control valve.

[0042] As shown in fig. 3, the second flow path includes a one-way valve 16. The one-way valve 16 is arranged upstream with respect to the leakage collection system 9. Here, the oneway valve 16 is arranged upstream with respect to the tank 10 of the leakage collection system 9.

[0043] The sealing system 1 can be used in a marine propulsion system (not shown). The sealing system 1 according to the invention is in particular useful, in case, the marine propulsion system comprises a height adjustable propeller unit. The void chamber 2 and tank 10 are integrated with the propeller unit. Therefore, the void chamber 2 and tank 10 move in unity and in correspondence with the height adjustable propeller unit. The void chamber 2 and tank 10 move in unity at least with respect to height position.

[0044] The sealing system 1 of figure 2 and / or figure 3 can be operated in different operating modes. A normal mode refers to collecting leakage from the void chamber 2 into the tank 10. In normal mode the air supply line 8 operates at a pressure below a predetermined reference pressure. At a pressure below a predetermined reference pressure, the valves 15, 17 are not activated. This means that valve 15 is closed and valve 17 is open and allows collecting leakage from the lip seal systems 4, 5, to the tank 10. The check valve 13 enables to maintain a pre-determined overpressure in the void chamber 2 compared to the water column pressure that the check valve 13 is exposed to, and thus independent of the depth wherein the sealing system 1 is operating. The predetermine overpressure in the void chamber is about 0,1 bar.

[0045] The sealing system 1 can be operated in different operating modes. A drain mode refers to emptying the tank 10. In drain mode the air supply line 8 operates at a pressure above a predetermined reference pressure. At a pressure above the predetermined reference pressure, the valves 15, 17 are activated. This means that valve 15 is open and valve 17 is closed. This allows emptying the tank 10 by displacing collected leakage in the tank 10 with pressurized air from the air supply line 8.

[0046] Figures 4A, 4B and 4C show the first embodiment of the sealing system 1 shown in figure 2 in different perspectives. Figure 4A shows the sealing system 1 along a longitudinal direction of the shaft 3. The void chamber inlet 6 and outlet 7 for allowing air flow through the void chamber are shown. The mounting flange 20 is shown which is mounted or mountable to a stationary part of a vessel (not shown). Another mounting flange 21 is mounted or mountable to the propeller shaft 3. The sealing system 1 including the mounting flanges 20, 21 is here referred to with reference number 24.

[0047] Figure 4B shows a detail of the sealing system 1 of figure 4A in cross sectional view. The sealing system 1 comprises the two opposite lip seals 4, 5. The void chamber 2 is arranged between the two opposite lip seals 4, 5 of the lip sealing system 4, 5. The void chamber 2 functions to set a pressure across the lip seals 4, 5 and for collecting leakage from the lip seal system. Therefore, the void chamber has a void chamber inlet 6 and outlet 7 (not shown here) for allowing air flow through the void chamber. The void chamber 2 separates the chamber 22 from the water side 23. The chamber 22 is normally filled with oil or grease. Although not shown here, there can be more lip seals that work in series, like for example another lip seal upstream with respect to the lip seal 4. Here, “upstream” refers to a possible leakage over the lip seal 4 from the water side 23 toward the void chamber 2. In this figure 4B, the another lip seal will be added to the left side which results in a sealing system 1 using 4 lip seals in total. It will be clear that any suitable number of lip seals is conceivable depending on the application and requirements.

[0048] Figure 4C shows the sealing system 1 of figure 4A in perspective partly cut-away view. The sealing system 1 extends around the axis 19 of the propeller shaft 3.

[0049] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.

[0050] -0-0-0-0-0-0-

Claims

Claims1. Sealing system (1) for sealing a marine propeller shaft (3), the sealing system comprising; a void chamber (2) arranged between lip seal systems (4, 5) for collecting leakage from the lip seal systems and having a void chamber inlet (6) and outlet (7) for allowing air flow through the void chamber, an air supply line (8) fluid coupled with a first flow path (11) including the void chamber for maintaining an overpressure in the void chamber, a leakage collection system (9) fluid coupled with the void chamber outlet, and wherein the leakage collection system comprises a tank (10) that is fluid coupled with the air supply line through a second flow path (12) different from the first flow path (11) and in parallel with the first flow path.

2. Sealing system according to claim 1, wherein the first flow path comprises a flow restricting member for restricting the flow of air through the void chamber.

3. Sealing system according to claim 2, wherein the flow restricting member comprises an adjustable flow restrictor.

4. Sealing system according to a preceding claim, wherein the second flow path comprises a control valve to allow or stop flow of air through the second flow path.

5. Sealing system according to claim 4, wherein the second flow path comprises a pressure- controlled valve that is normally closed.

6. Sealing system according to a preceding claim, wherein the second flow path comprises a one-way valve.

7. Sealing system according to a preceding claim, wherein the first flow path comprises a control valve system to couple or decouple the leakage collection system and the void chamber outlet.

8. Sealing system according to claim 5 and 7, wherein the control valve system of the first flow path comprises a normally open pressure controlled valve, wherein respective control input connections of the first flow path normally open pressure controlled valve and the second flow path normally closed pressure controlled valve are both fluid coupled to the air supply line (8).

9. Sealing system according to a preceding claim, wherein the leakage collection system comprises a buffer for temporarily collecting leakage from the lip seal systems, and wherein the buffer is included in the first flow path and upstream with respect to the tank.

10. Sealing system according to claim 9, wherein the control valve included in the first flow path, is arranged between the buffer and the tank.

11. Sealing system according to claim 10, wherein the void chamber outlet is directly coupled with the buffer.

12. Sealing system according to a preceding claim, wherein the first and second flow path end at the tank.

13. Sealing system according to a preceding claim, wherein the leakage collection system is at least partly arranged below the void chamber.

14. Sealing system according to a preceding claim, wherein the void chamber comprises a check valve.

15. Marine propulsion system comprising a sealing system according to a preceding claim.

16. Marine propulsion system according to the claim 15, comprising a height adjustable propeller unit, wherein the void chamber and tank move in unity and in correspondence with the height adjustable propeller unit.

17. Use of a sealing system according to any of claims 1-14, comprising one of the hollowing steps;operating the air supply line (8) at a pressure below a predetermined reference pressure and simultaneously collecting leakage from the lip seal systems to the tank, and operating the air supply line (8) at a pressure above the predetermined reference pressure and simultaneously emptying the tank by displacing collected leakage in the tank with pressurized air from the air supply line (8).-0-0-0-0-0-0-

Images