Self-cleaning device for liquid collecting well of fuel tank of LNG (Liquefied Natural Gas) ship

Abstract

The invention discloses a self-cleaning device for a liquid collecting well of a fuel tank of an LNG (Liquefied Natural Gas) ship. The self-cleaning device comprises the liquid collecting well, a bottom injection pipe, an annular return pipe, a cofferdam and a plurality of cleaning pipes, the two immersed pumps are sleeved with the annular return pipe, and the annular return pipe is installed on the upper portion of the liquid collecting well and connected with one end of the bottom injection pipe through the S-shaped connecting pipe; the cofferdam and the annular return pipe are coaxially fixed on the inner bottom surface of the liquid collecting well; a plurality of through holes are uniformly formed in the bottom circumference of the cofferdam in the radial direction; each cleaning pipe is provided with a vertical part and a horizontal part and is in an L shape, the upper ends of the vertical parts of the cleaning pipes are circumferentially and evenly connected to the annular backflow pipe, the horizontal parts of the cleaning pipes are inserted into the penetrating holes of the cofferdam in a one-to-one correspondence mode, and a plurality of nozzles are formed in the bottom of the inner section and the two sides of the inner section of each cleaning pipe located in an inner cavity of the cofferdam respectively. The liquid collecting well is scoured through the backflow working condition of LNG, impurities can be prevented from being gathered below the bottom suction opening of the immersed pump, and normal work of the immersed pump is guaranteed.

Description

Technical Field

[0001] The invention relates to a self-cleaning device for a liquid collecting well of a fuel tank of an LNG ship. Background Art

[0002] With the increasingly stringent environmental protection requirements of the ocean, liquefied natural gas (LNG) has been widely adopted as a new fuel for ships. The LNG liquid in the fuel tank 100 is injected through the LNG filling pipeline 101. Two submersible pumps 20 need to be installed in the fuel tank 100 to extract liquefied gas to supply the power system of the ship. A liquid collection well 10 is recessed at the bottom of the fuel tank 100 corresponding to the two submersible pumps, and the bottom suction ports of the two submersible pumps 20 extend into the liquid collection well 10. When the submersible pump 20 is working, the LNG liquid in the fuel tank 100 will converge to the liquid collection well 10, and then be extracted by the submersible pump 20 and transported to the power system of the ship through the gas supply pipeline 201. In this process, the flow of LNG will drive the impurities deposited on the inner bottom of the fuel tank 100 to flow to the liquid collection well 10. Currently, the impurities in the LNG are blocked by the suction filter of the submersible pump 20. The isolated impurities will accumulate directly below the suction port of the submersible pump 20. If the suction filter is not cleaned for a long time, it may be blocked by impurities or even be sucked into the two submersible pumps 20, affecting the normal operation of the submersible pumps 20. When the power system (main engine and generator) of the ship is not in operation, the BOG generated by the fuel tank 100 cannot be consumed, so the LNG will flow back to the fuel tank 100 through the gas supply pipeline 201 and the LNG filling pipeline 101 (see Figure 1a 、 Figure 1b and Figure 1c ). Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a self-cleaning device for the liquid collection well of the LNG ship fuel tank. It uses the reflux condition of LNG to flush the liquid collection well, which can prevent impurities from accumulating below the bottom suction port of the submersible pump, thereby ensuring the normal operation of the submersible pump.

[0004] The object of the present invention is achieved as follows: a self-cleaning device for a liquid collecting well of a fuel tank of an LNG ship, comprising a liquid collecting well, a bottom injection pipe, an annular return pipe, a cofferdam and a plurality of cleaning pipes; the liquid collecting well is arranged at the inner bottom of the fuel tank, two submersible pumps are vertically arranged in the fuel tank, and the bottom suction ports of the two submersible pumps extend into the liquid collecting well; the bottom injection pipe is horizontally arranged at the lower part of the fuel tank along the length direction of the fuel tank and is located on one side of the liquid collecting well, and the middle part of the bottom injection pipe is connected to the LNG filling pipeline of the fuel tank; wherein,

[0005] The annular return pipe is sleeved outside the two submersible pumps and installed on the upper part of the liquid collection well. The annular return pipe is connected to one end of the bottom injection pipe through an S-shaped connecting pipe;

[0006] The cofferdam and the annular return pipe are coaxially fixed to the inner bottom surface of the liquid collection well. The cofferdam is a cylindrical body with an outer diameter smaller than the inner diameter of the liquid collection well but larger than the outer distance between the two submersible pumps. The height of the cofferdam is lower than the installation height of the annular return pipe. A plurality of radial perforations are evenly distributed around the bottom circumference of the cofferdam.

[0007] The cleaning pipe has a vertical portion and a horizontal portion and is L-shaped. The upper ends of the vertical portions of several cleaning pipes are evenly connected to the annular return pipe on a circumference, and the horizontal portions of several cleaning pipes are inserted into several through-holes of the cofferdam one by one. Several nozzles are respectively opened at the bottom of the inner section and on both sides of the inner section of each cleaning pipe located in the inner cavity of the cofferdam.

[0008] In the above-mentioned self-cleaning device for the liquid collecting well of the fuel tank of the LNG ship, the annular return pipe is fixed to the upper part of the inner wall of the liquid collecting well by a plurality of brackets.

[0009] The self-cleaning device for the LNG ship fuel tank liquid collecting well of the present invention has the following characteristics:

[0010] 1. Introduce the LNG injection pipe into the liquid collection well and use the LNG reflux condition to flush the liquid collection well. No additional purge process is required. Impurities accumulated in the liquid collection well in the fuel tank can be blown away to prevent impurities from accumulating directly below the bottom suction port of the submersible pump, thereby ensuring the normal operation of the submersible pump.

[0011] 2. After self-cleaning, impurities will gather on the periphery of the cofferdam, making it easier to clean up later.

[0012] 4. The self-cleaning device of the present invention has a simple structure and low cost, and can be installed with only commonly used pipes, profiles, brackets, etc.

[0013] 5. The self-cleaning device of the present invention has a reasonable structure. The annular return pipe in the liquid collection well is close to the top of the inner wall of the liquid collection well, and the cofferdam is located at the bottom of the liquid collection well, which does not affect the installation and maintenance of the submersible pump in the liquid collection well.

[0014] 6. The arrangement of the self-cleaning device of the present invention is also applicable to liquefied gas ships carrying other cargoes, and is also applicable to LNG type A tanks, type B tanks and type C tanks. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1a This is a side view of a conventional LNG carrier fuel tank;

[0016] Figure 1b This is a top-down perspective view of a conventional LNG carrier fuel tank;

[0017] Figure 1c This is a front view of a conventional LNG carrier fuel tank;

[0018] Figure 2 2. It is a front view of the self-cleaning device for the liquid collecting well of the fuel tank of an LNG ship according to the present invention;

[0019] Figure 3 yes Figure 2 Enlarged view of the middle P site;

[0020] Figure 4 yes Figure 2 A-direction view in. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] See also Figures 2 to 4 The self-cleaning device of the LNG ship fuel tank liquid collecting well of the present invention includes a liquid collecting well 10, a bottom injection pipe 1, an annular return pipe 3, a cofferdam 4 and four cleaning pipes 5.

[0023] The fuel tank 100 is in the shape of a lying cylinder; the liquid collecting well 10 is provided at the bottom of one side of the fuel tank 100, and the liquid collecting well 10 is in the shape of a barrel or a round waist barrel. In this embodiment, the liquid collecting well 10 is in the shape of a barrel, and two submersible pumps 20 are provided in the fuel tank 100, and the bottom suction ports of the two submersible pumps 20 extend into the liquid collecting well 10.

[0024] The bottom filling pipe 1 is horizontally arranged at the lower part of the fuel tank 100 along the length direction of the fuel tank 100 and is located on one side of the liquid collecting well 10. The middle part of the bottom filling pipe 1 is connected to the LNG filling pipeline 101 vertically inserted into the fuel tank 100.

[0025] The planar shape of the annular return pipe 3 is adapted to the planar shape of the liquid collecting well 10. The annular return pipe 3 is sleeved outside the two submersible pumps 20 and is installed on the top of the liquid collecting well 10 through four brackets 30. The four brackets 3 are evenly welded and fixed to the top of the inner wall of the liquid collecting well 10 in a circumferentially distributed manner. The annular return pipe 3 is connected to one end of the bottom injection pipe 1 through an S-shaped connecting pipe 2.

[0026] The cofferdam 4 is coaxially fixed to the inner bottom surface of the liquid collecting well 10. The cofferdam 4 is a cylinder with an outer diameter smaller than the inner diameter of the liquid collecting well 10 but larger than the outer distance between the two submersible pumps 20. The plan shape of the cofferdam 4 is adapted to the plan shape of the liquid collecting well 10. The height of the cofferdam 4 is lower than the setting height of the annular return pipe 3. Four radial perforations are evenly distributed on the bottom circumference of the cofferdam 4.

[0027] The cleaning pipe 5 has a vertical portion and a horizontal portion and is L-shaped. The upper ends of the vertical portions of the four cleaning pipes 5 are evenly connected to the annular return pipe 3 around the circumference, and the horizontal portions of the four cleaning pipes 5 are inserted into the four through-holes of the cofferdam 4 one by one, and the ends of the horizontal portions of the four cleaning pipes 5 are located on a circle whose diameter is smaller than the axial center spacing of the bottom suction ports of the two submersible pumps 20; a number of nozzles 50 are respectively opened at the bottom of the inner section and on both sides of the inner section of each cleaning pipe 5 located in the inner cavity of the cofferdam 4.

[0028] The self-cleaning device of the LNG ship fuel tank liquid collection well of the present invention is that when the submersible pump 20 is working and when the power system of the ship (main engine and generator) is not in working state, LNG simultaneously flows back to the bottom injection pipe 1 through the LNG filling pipeline 101, and is then introduced into the liquid collection well 10 through the connecting pipe 2, the annular return pipe 3 and the four cleaning pipes 5. When the power system of the ship is in a non-working state, that is, when LNG is refluxed, the impurities accumulated in the liquid collecting well 10 are blown away by the joint action of the nozzles 50 of the four cleaning pipes 5 and the submersible pump 20. The dispersed impurities will gather at the periphery of the liquid collecting well 10 and be blocked by the cofferdam 4 to prevent them from gathering directly below the bottom suction port of the submersible pump 20. At the same time, the impurities in the fuel tank 100 flowing to the liquid collecting well 10 are also isolated by the cofferdam 4 and will not enter the inside of the cofferdam 6, that is, they will not gather directly below the submersible pump 20, preventing the suction port filter 21 of the submersible pump 20 from being blocked, thereby ensuring the normal operation and safety of the submersible pump 20, and also facilitating subsequent cleaning by maintenance personnel.

[0029] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the art may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by the claims.

Claims

1. A self-cleaning device for a liquid collecting well of an LNG ship fuel tank, comprising a liquid collecting well, a bottom injection pipe, an annular return pipe, a cofferdam, and a plurality of cleaning pipes; the liquid collecting well is arranged at the inner bottom of the fuel tank, two submersible pumps are vertically arranged in the fuel tank, and the bottom suction ports of the two submersible pumps extend into the liquid collecting well; the bottom injection pipe is horizontally arranged at the lower part of the fuel tank along the length direction of the fuel tank and is located on one side of the liquid collecting well, and the middle part of the bottom injection pipe is connected to the LNG filling pipeline of the fuel tank; it is characterized in that The annular return pipe is sleeved outside the two submersible pumps and installed on the upper part of the liquid collection well. The annular return pipe is connected to one end of the bottom injection pipe through an S-shaped connecting pipe; The cofferdam and the annular return pipe are coaxially fixed to the inner bottom surface of the liquid collection well. The cofferdam is a cylindrical body with an outer diameter smaller than the inner diameter of the liquid collection well but larger than the outer distance between the two submersible pumps. The height of the cofferdam is lower than the installation height of the annular return pipe. A plurality of radial perforations are evenly distributed around the bottom circumference of the cofferdam. The cleaning pipe has a vertical portion and a horizontal portion and is L-shaped. The upper ends of the vertical portions of several cleaning pipes are evenly connected to the annular return pipe on a circumference, and the horizontal portions of several cleaning pipes are inserted into several through-holes of the cofferdam one by one. Several nozzles are respectively opened at the bottom of the inner section and on both sides of the inner section of each cleaning pipe located in the inner cavity of the cofferdam.

2. The self-cleaning device for the LNG ship fuel tank liquid collection well according to claim 1, characterized in that: The annular return pipe is fixed to the upper part of the inner wall of the liquid collecting well through a plurality of brackets.

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