Arrangement and method for sealing a propeller shaft of a marine vessel

1 . An arrangement for sealing a propeller shaft of a marine vessel, the arrangement comprising:

a shaft seal arrangement for sealing the propeller shaft against sea water, and

a lubrication arrangement comprising a lubricant circulation line for conducting lubricant to said shaft seal arrangement and for conducting lubricant from said shaft seal arrangement, a lubricant circulator configured to create a flow of lubricant in the lubricant circulation line and in said shaft seal arrangement,

wherein the lubricant circulation line defines a first part downstream of the lubricant circulator and upstream of the shaft seal arrangement and a second part downstream of the shaft seal arrangement and upstream of the lubricant circulator, and

wherein:

the first part of the lubricant circulation line includes a connection line that is connected in fluid connection with the lubricant circulation line downstream of the lubricant circulator and upstream of the shaft seal arrangement, and that is connected in fluid connection with the second part of the lubricant circulation line so as to selectively conduct a part of the flow of lubricant past the shaft seal arrangement,

at least one hydraulically operated pressure relief means configured to control the flow of lubricant in the connection line, wherein said at least one hydraulically operated pressure relief means is configured to be operated by means of the lubricant circulating in the first part of the lubricant circulation line,

said at least one hydraulically operated pressure relief means is configured to sense characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line,

said at least one hydraulically operated pressure relief means is configured to be hydraulically operated by means of the lubricant circulating in the first part of the lubricant circulation line in response to the sensed characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line,

said at least one hydraulically operated pressure relief means being configured to connect the connection line in fluid connection with the lubricant circulation line downstream of the lubricant circulator and upstream of the shaft seal arrangement,

the characteristics of the flow of the lubricant circulating in the first part of the lubricant circulation line said at least one hydraulically operated pressure relief means is configured to sense a volumetric flow rate of the lubricant circulating in the first part of the lubricant circulation line, and

said at least one hydraulically operated pressure relief means being configured to redirect a part of the flow of the lubricant circulating in the lubricant circulation line into the connection line if the volumetric flow rate of the lubricant circulating in the first part of the lubricant circulation line exceeds a threshold value for the volumetric flow rate.

2 . The arrangement according to claim 1 , wherein:

said at least one hydraulically operated pressure relief means is provided in the connection line.

3 . The arrangement according to claim 2 , wherein:

the characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line said at least one hydraulically operated pressure relief means is configured to sense is the pressure of the lubricant circulating in the first part of the lubricant circulation line, and

said at least one hydraulically operated pressure relief means is configured to be open if the pressure of the flow of lubricant circulating in the first part of lubricant circulation line exceeds a threshold value for the pressure and to be closed if the pressure of the flow of lubricant circulating in the lubricant circulation line subceeds the threshold value for the pressure.

4 . The arrangement according to claim 3 , wherein:

said at least one hydraulically operated pressure relief means being a check valve, and

the threshold value for pressure being a cracking pressure of the check valve.

5 . The arrangement according to claim 1 , wherein:

said at least one hydraulically operated pressure relief means being a resistance valve.

6 . The arrangement according to claim 1 , wherein:

the second part of the lubricant circulation line includes a lubricant tank in fluid connecting with the lubricant circulation line and configured to feed lubricant to the lubricant circulation line.

7 . The arrangement according to claim 6 , wherein:

the connection line being connected in fluid connection with the second part of the lubricant circulation line by being connected in fluid connection with the lubricant tank of the second part of the lubricant circulation line.

8 . The arrangement according to claim 1 , wherein:

the shaft seal arrangement comprising a plurality of seal rings axially space apart from each other and engaging the outer circumference of the propeller shaft such that at least one lubricant seal chamber is delimited between adjacent seal rings and the outer circumference of the propeller shaft,

the lubricant circulation line for conducting lubricant to said shaft seal arrangement and for conducting lubricant from said shaft seal arrangement being configured to conduct lubricant to said at least one lubricant seal chamber and configured to conduct lubricant from said at least one lubricant seal chamber, and

the lubricant circulator configured to create a flow of lubricant in the lubricant circulation line and in said shaft seal arrangement being configured to create a flow of lubricant in the lubricant circulation line and in said at least one lubricant seal chamber.

9 . A method for sealing a propeller shaft of a marine vessel with a sealing arrangement comprising:

a shaft seal arrangement for sealing the propeller shaft against sea water, and

a lubrication arrangement comprising a lubricant circulation line for conducting lubricant to said shaft seal arrangement and for conducting lubricant from said shaft seal arrangement, a lubricant circulator configured to create a flow of lubricant in the lubricant circulation line and in said shaft seal arrangement,

wherein the lubricant circulation line defines a first part downstream of the lubricant circulator and upstream of the shaft seal arrangement and a second part downstream of the shaft seal arrangement and upstream of the lubricant circulator, and

wherein the method comprises creating a flow of lubricant in the lubricant circulation line and in said shaft seal arrangement by means of the lubricant circulator, wherein the method comprises:

providing the first part of the lubricant circulation line with a connection line and connecting the connection line in fluid connection with the lubricant circulation line downstream of the lubricant circulator and upstream of the shaft seal arrangement, and connecting the connection line in fluid connection with the second part of the lubricant circulation line so as to selectively conduct a part of the flow of lubricant past the shaft seal arrangement, and

providing at least one hydraulically operated pressure relief means configured to control the flow of lubricant in the connection line, wherein said at least one hydraulically operated pressure relief means is configured to be operated by means of the lubricant circulating in the first part of the lubricant circulation line,

wherein the method includes sensing characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line by said at least one hydraulically pressure relief means,

wherein the method includes hydraulically operating said at least one hydraulically pressure relief means by means of the lubricant circulating in the first part of the lubricant circulation line in response to the sensed characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line.

10 . The method according to claim 9 , wherein:

providing one hydraulically operated pressure relief means in the connection line.

11 . The method according to claim 10 , wherein:

the characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line said one hydraulically pressure relief means is configured to sense is the pressure of the lubricant circulating in the first part of the lubricant circulation line,

keeping said one hydraulically pressure relief means open if the pressure of the flow of lubricant circulating in the first part of lubricant circulation line exceeds a threshold value for the pressure, and

keeping said one hydraulically pressure relief means closed if the pressure of the flow of lubricant circulating in the lubricant circulation line subceeds the threshold value for the pressure.

12 . The method according to claim 11 , wherein:

providing said one hydraulically operated pressure relief means in the form of a check valve, wherein the threshold value for pressure being a cracking pressure of the check valve.

13 . The method according to claim 9 , wherein:

connecting the connection line in fluid connection with the lubricant circulation line downstream of the lubricant circulator and upstream of the shaft seal arrangement with one hydraulically operated pressure relief means.

14 . The method according to claim 13 , wherein:

the characteristics of the flow of the lubricant circulating in the first part of lubricant circulation line said one hydraulically pressure relief means is configured to sense is the volumetric flow rate of the lubricant circulating in the first part of the lubricant circulation line, and

redirecting a part of the flow of lubricant circulating in the lubricant circulation line with said one hydraulically operated pressure relief means into the connection line if the volumetric flow rate of the lubricant circulating in the first part of the lubricant circulation line exceeds a threshold value for the volumetric flow rate.

15 . The method according to claim 14 , wherein:

providing said one hydraulically operated pressure relief means in the form of a resistance valve.

16 . The method according to claim 8 , wherein:

the second part of the lubricant circulation line includes a lubricant tank in fluid connecting with the lubricant circulation line and configured to feed lubricant to the lubricant circulation line, and

the method comprises feeding lubricant from the lubricant tank into the lubricant circulation line.

17 . The method according to claim 16 , wherein:

connecting the connection line in fluid connection with the second part of the lubricant circulation line by connecting the connection line in fluid connection with the lubricant tank of the second part of the lubricant circulation line.

18 . The method according to claim 9 , wherein:

the shaft seal arrangement comprising a plurality of seal rings axially space apart from each other and engaging the outer circumference of the propeller shaft such that at least one lubricant seal chamber is delimited between adjacent seal rings and the outer circumference of the propeller shaft,

the lubricant circulation line for conducting lubricant to said shaft seal arrangement and for conducting lubricant from said shaft seal arrangement being configured to conduct lubricant to said at least one lubricant seal chamber and configured to conduct lubricant from said at least one lubricant seal chamber,

the lubricant circulator configured to create a flow of lubricant in the lubricant circulation line and in said shaft seal arrangement being configured to create a flow of lubricant in the lubricant circulation line and in said at least one lubricant seal chamber, and

the method includes creating a flow of lubricant in at least one lubricant seal chamber of the shaft seal arrangement.