Cryogenic-pipe cooling test system and method for LNG carrier

Abstract

A cryogenic pipe cooling test system and method for an LNG carrier. The system comprises a liquid main pipe (1), a boil-off gas main pipe (2), a gas main pipe (3), and a liquid nitrogen vaporization module. The rear part of the liquid main pipe (1) is in communication with a temporary vent mast (4); the front part of the liquid main pipe (1) is in communication with the forward part of the boil-off gas main pipe (2); the rear part of the boil-off gas main pipe (2) is in communication with the rear part of the gas main pipe (3); the forward part of the boil-off gas main pipe (2) is in communication with a vent mast (5); and the forward part of the gas main pipe (3) is in communication with the vent mast (5). The liquid nitrogen vaporization module comprises a liquid nitrogen storage tank (8), a vaporizer (9), and a spray spool (10), wherein the liquid nitrogen storage tank (8) is in communication with the vaporizer (9) by means of a liquid nitrogen main pipe; the vaporizer (9) is in communication with the spray spool (10); and the spray spool (10) is respectively in communication with the liquid main pipe (1), the boil-off gas main pipe (2) and the gas main pipe (3) by means of nitrogen branch pipes. By means of cooling one pipe while pre-cooling the other pipes, pipe pre-cooling time is reduced, and during cooling, the cooling of each pipe starting from ambient temperature is prevented, thereby reducing pipe pre-cooling time and shortening the test cycle.

Description

A test system and method for cryogenic pipeline cooling in LNG carriers Technical Field

[0001] This invention belongs to the field of shipbuilding technology, specifically relating to a cryogenic pipeline cooling test system and method for LNG ships. Background Technology

[0002] A membrane-type LNG carrier is a specialized vessel for transporting liquefied natural gas at -163°C. Before the vessel is put into operation, a cooling test must be conducted on the pipelines to ensure that the construction quality of the LNG cryogenic cargo system pipelines meets the design requirements.

[0003] Traditional cooling tests have the following two drawbacks:

[0004] 1. Long cooling time. In traditional cooling experiments, liquid nitrogen is vaporized using a vaporizer to cool each pipeline separately, without interconnection, and each pipeline is initially at room temperature. When the liquid main pipeline has cooled down, the volatile gas main pipeline and the gas main pipeline are still at room temperature. Depending on the ambient temperature, the cooling time for each pipeline is approximately 4-8 hours, and the testing time is about 1-2 hours, resulting in a significant waste of time on pipeline pre-cooling.

[0005] 2. High liquid nitrogen consumption. In traditional cooling experiments, after cooling a single pipeline is completed, the cold air inside the pipeline is directly discharged, resulting in waste of liquid nitrogen and energy consumption. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system and method for cooling pipelines in LNG ships. This invention pre-cools other pipelines while cooling one pipeline, saving pipeline pre-cooling time and avoiding the need for each pipeline to start cooling from room temperature. This saves pipeline cooling time and makes full use of pipeline inspection time. During pipeline inspection, this method can still pre-cool other pipelines, reducing the time it takes for other pipelines to cool to the specified temperature and shortening the test cycle.

[0007] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0008] A cryogenic pipeline cooling test system for LNG carriers includes a liquid main, a volatile gas main, a gas main, and a liquid nitrogen vaporization module. The stern of the liquid main is connected to a temporary ventilator, the bow of the liquid main is connected to the bow of the volatile gas main, the stern of the volatile gas main is connected to the stern of the gas main, the bow of the volatile gas main is connected to the ventilator, and the bow of the gas main is connected to the ventilator. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank, a vaporizer, and a spray pipe. The liquid nitrogen storage tank is connected to the vaporizer via a liquid nitrogen main pipeline, the vaporizer is connected to the spray pipe, and the spray pipe is connected to the liquid main, the volatile gas main, and the gas main via nitrogen branch pipes.

[0009] Furthermore, a valve is installed on the pipeline connecting the liquid main to the temporary ventilation mast, and temperature sensors are respectively installed at the bow and stern of the liquid main. The bow of the liquid main is connected to the bow of the volatile gas main through a detachable elbow, and a valve is installed between the liquid main and the detachable elbow.

[0010] Furthermore, temperature sensors are respectively installed at the bow and stern of the volatile gas main pipe, and valves are installed on the pipeline connecting the volatile gas main pipe and the ventilation mast.

[0011] Furthermore, temperature sensors are respectively installed at the bow and stern of the gas main, and valves are installed on the pipeline connecting the gas main to the ventilation mast.

[0012] Furthermore, four valves are installed on the main liquid nitrogen pipeline between the liquid nitrogen storage tank and the vaporizer, namely the first valve, the second valve, the third valve and the fourth valve, and valves are installed on the nitrogen branch pipes that connect the spray short pipe to the gas main pipe and the volatile gas main pipe.

[0013] Furthermore, the spray pipe is connected to the main liquid nitrogen pipeline between the third valve and the fourth valve, a fifth valve is installed on the pipeline connecting the spray pipe to the main liquid nitrogen pipeline, and a valve is installed on the outlet pipeline of the spray pipe.

[0014] A method for cryogenic pipeline cooling tests on LNG carriers, the method specifically includes the following steps:

[0015] S1. Prepare a cryogenic pipeline cooling test system for LNG ships. The system includes a liquid main, a volatile gas main, a gas main, and a liquid nitrogen vaporization module. The stern of the liquid main is connected to a temporary ventilated mast, the bow of the liquid main is connected to the bow of the volatile gas main, the stern of the volatile gas main is connected to the stern of the gas main, and the bow of the gas main is connected to the ventilated mast. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank, a vaporizer, and a spray pipe. The liquid nitrogen storage tank is connected to the vaporizer through a liquid nitrogen main pipeline, the vaporizer is connected to the spray pipe, and the spray pipe is connected to the liquid main, the volatile gas main, and the gas main through nitrogen branch pipes, respectively.

[0016] S2, Liquid main cooling: Open the first, second, third, and fourth valves on the main liquid nitrogen pipeline, and open the valves on the nitrogen branch pipe leading to the liquid main. Liquid nitrogen in the liquid nitrogen storage tank is vaporized through the vaporizer in the main liquid nitrogen pipeline and then flows to the liquid main. The cryogenic nitrogen entering the liquid main cools the liquid main. At the same time, temperature sensors at the bow and stern of the liquid main detect the temperature of the liquid main. Meanwhile, the cryogenic nitrogen flows through the valves at the bow and stern of the liquid main to the volatile gas main and the temporary venting mast, respectively.

[0017] S3, while the cryogenic nitrogen cools the liquid main, the cryogenic nitrogen flowing to the volatile gas main through the detachable elbow pre-cools the volatile gas main. After the liquid main is cooled, close the valve on the cryogenic nitrogen branch pipe leading to the liquid main and the valve at the connection between the liquid main and the volatile gas main.

[0018] S4, evaporative gas main pipe cooling: open the branch pipe valve leading to the evaporative gas main pipe, open the valve on the pipeline connecting the evaporative gas main pipe and the ventilation mast, open the valve on the pipeline connecting the gas main pipe and the ventilation mast, and low-temperature nitrogen enters the evaporative gas main pipe to cool it. Low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the evaporative gas main pipe and the gas main pipe to pre-cool the gas main pipe.

[0019] S5, Gas main pipe cooling: After the volatile gas main pipe is cooled, close the branch pipe valve leading to the volatile gas main pipe and open the branch pipe valve leading to the gas main pipe. Low-temperature nitrogen gas is used to cool the gas main pipe. During the cooling process, the low-temperature nitrogen gas flows to the ventilated mast through the volatile gas main pipe and the gas main pipe.

[0020] S6. After the gas main pipe has cooled down, close the valve on the liquid nitrogen main pipe to stop supplying cryogenic nitrogen to the gas main pipe. After the cryogenic nitrogen in the liquid main pipe, volatile gas main pipe and gas main pipe has been completely discharged through the venting mast and temporary venting mast, close all the valves on the pipes to complete the cryogenic pipeline cooling test.

[0021] Furthermore, the temperature of the low-temperature nitrogen gas output from the spray short pipe is -140°C. When the temperature of the liquid nitrogen after vaporization by the vaporizer does not reach -140°C, the valve connecting the spray short pipe and the liquid nitrogen main pipe is opened, allowing the liquid nitrogen to directly enter the spray short pipe and mix with the vaporized nitrogen gas, thereby reducing the temperature of the nitrogen gas output from the spray short pipe to -140°C.

[0022] Furthermore, when the liquid manifold is cooled, the cooling of the liquid manifold is completed when the temperature sensor on the liquid manifold measures that the temperature inside the liquid manifold has dropped to -100°C; when the volatile gas manifold is cooled, the cooling of the volatile gas manifold is completed when the temperature sensor on the volatile gas manifold measures that the temperature inside the volatile gas manifold has dropped to -100°C; when the gas manifold is cooled, the cooling of the gas manifold is completed when the temperature sensor on the gas manifold measures that the temperature inside the gas manifold has dropped to -100°C.

[0023] Based on the above technical solution, the present invention patent's cryogenic pipeline cooling test system and method for LNG ships has achieved the following technical advantages through practical application:

[0024] 1. Compared with conventional methods, the present invention provides a method for cryogenic pipeline cooling tests on LNG ships that pre-cools other pipelines while cooling one pipeline, saving pipeline pre-cooling time and avoiding the need for each pipeline to start cooling from room temperature. This saves pipeline cooling time and makes full use of pipeline inspection time. During pipeline inspection, this method can still pre-cool other pipelines, reducing the time it takes for other pipelines to cool to the specified temperature and shortening the test cycle. Attached Figure Description

[0025] Figure 1 is a diagram of the liquid manifold cooling pipeline in a cryogenic pipeline cooling test system for LNG ships according to the present invention.

[0026] Figure 2 is a diagram of the volatile gas main cooling pipeline in a cryogenic pipeline cooling test system for LNG ships according to the present invention.

[0027] Figure 3 is a diagram of the gas main cooling pipeline in a cryogenic pipeline cooling test system for LNG ships according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] As shown in Figures 1-3, this invention pertains to a cryogenic pipeline cooling test system for LNG carriers. The system includes a liquid main pipe 1, a volatile gas main pipe 2, a gas main pipe 3, and a liquid nitrogen vaporization module. The stern of the liquid main pipe 1 is connected to a temporary ventilated mast 4, the bow of the liquid main pipe 1 is connected to the bow of the volatile gas main pipe 2, the stern of the volatile gas main pipe 1 is connected to the stern of the gas main pipe 3, the bow of the volatile gas main pipe 1 is connected to a ventilated mast 5, and the bow of the gas main pipe 3 is connected to a ventilated mast 5. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank 8, a vaporizer 9, and a spray pipe 10. The liquid nitrogen storage tank 8 is connected to the vaporizer 9 via a main liquid nitrogen pipeline, the vaporizer 9 is connected to the spray pipe 10, and the spray pipe 10 is connected to the liquid main pipe 1, the volatile gas main pipe 2, and the gas main pipe 3 via nitrogen branch pipes.

[0030] A valve 79 is installed on the pipeline connecting the liquid main 1 and the temporary ventilation mast 4. Temperature sensors 11 are installed at the bow and stern of the liquid main 1. The bow of the liquid main 1 is connected to the bow of the volatile gas main 2 through a detachable elbow. A valve 78 is installed between the liquid main 1 and the detachable elbow. A detachable short pipe is installed on the nitrogen branch pipe leading to the liquid main 1 to facilitate the removal of the equipment pipeline after the cooling experiment is completed.

[0031] Temperature sensors 11 are installed at the bow and stern of the main volatile gas pipe 2, and valves 77 are installed on the pipeline connecting the main volatile gas pipe 2 and the ventilation mast 5.

[0032] Temperature sensors 11 are installed at the bow and stern of the gas main pipe 3, and valves 76 are installed on the pipeline connecting the gas main pipe 3 and the ventilation mast 5.

[0033] Four valves are installed on the main liquid nitrogen pipeline between the liquid nitrogen storage tank 8 and the vaporizer 9, namely the first valve 61, the second valve 62, the third valve 63 and the fourth valve 64. Valves 72, 73, 74 and 75 are respectively installed on the nitrogen branch pipes that connect the spray short pipe 10 to the gas main pipe 3, the volatile gas main pipe 2 and the liquid main pipe 1.

[0034] The spray pipe 10 is connected to the main liquid nitrogen pipeline between the third valve 63 and the fourth valve 64. A valve 65 is installed on the pipeline connecting the spray pipe 10 and the main liquid nitrogen pipeline, and a valve 71 is installed on the outlet pipeline of the spray pipe 10.

[0035] A method for cryogenic pipeline cooling tests on LNG carriers, the method specifically includes the following steps:

[0036] S1. Prepare a cryogenic pipeline cooling test system for LNG ships. The system includes a liquid main, a volatile gas main, a gas main, and a liquid nitrogen vaporization module. The stern of the liquid main is connected to a temporary ventilated mast, the bow of the liquid main is connected to the bow of the volatile gas main, the stern of the volatile gas main is connected to the stern of the gas main, and the bow of the gas main is connected to the ventilated mast. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank, a vaporizer, and a spray pipe. The liquid nitrogen storage tank is connected to the vaporizer through a liquid nitrogen main pipeline, the vaporizer is connected to the spray pipe, and the spray pipe is connected to the liquid main, the volatile gas main, and the gas main through nitrogen branch pipes, respectively.

[0037] S2, Liquid main cooling: Open the first, second, third, and fourth valves on the main liquid nitrogen pipeline, and open the valves on the nitrogen branch pipe leading to the liquid main. Liquid nitrogen in the liquid nitrogen storage tank is vaporized through the vaporizer in the main liquid nitrogen pipeline and then flows to the liquid main. The cryogenic nitrogen entering the liquid main cools the liquid main. At the same time, temperature sensors at the bow and stern of the liquid main detect the temperature of the liquid main. Meanwhile, the cryogenic nitrogen flows through the valves at the bow and stern of the liquid main to the volatile gas main and the temporary venting mast, respectively.

[0038] S3, while the cryogenic nitrogen cools the liquid main, the cryogenic nitrogen flowing to the volatile gas main through the detachable elbow pre-cools the volatile gas main. After the liquid main is cooled, close the valve on the cryogenic nitrogen branch pipe leading to the liquid main and the valve at the connection between the liquid main and the volatile gas main.

[0039] S4, evaporative gas main pipe cooling: open the branch pipe valve leading to the evaporative gas main pipe, open the valve on the pipeline connecting the evaporative gas main pipe and the ventilation mast, open the valve on the pipeline connecting the gas main pipe and the ventilation mast, and low-temperature nitrogen enters the evaporative gas main pipe to cool it. Low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the evaporative gas main pipe and the gas main pipe to pre-cool the gas main pipe.

[0040] S5, Gas main pipe cooling: After the volatile gas main pipe is cooled, close the branch pipe valve leading to the volatile gas main pipe and open the branch pipe valve leading to the gas main pipe. Low-temperature nitrogen gas is used to cool the gas main pipe. During the cooling process, the low-temperature nitrogen gas flows to the ventilated mast through the volatile gas main pipe and the gas main pipe.

[0041] S6. After the gas main pipe has cooled down, close the valve on the liquid nitrogen main pipe to stop supplying cryogenic nitrogen to the gas main pipe. After the cryogenic nitrogen in the liquid main pipe, volatile gas main pipe and gas main pipe has been completely discharged through the venting mast and temporary venting mast, close all the valves on the pipes to complete the cryogenic pipeline cooling test.

[0042] The temperature of the cryogenic nitrogen gas output from the spray pipe 10 is -140℃. When the temperature of the liquid nitrogen after vaporization by the vaporizer 9 does not reach -140℃, the valve 71 connecting the spray pipe 10 and the main nitrogen pipe is opened, allowing the liquid nitrogen to directly enter the spray pipe 10 and mix with the vaporized nitrogen gas, thereby lowering the temperature of the nitrogen gas output from the spray pipe 10 to -140℃. The spray pipe 10 and the main liquid nitrogen pipeline are connected by valve 65, which allows for real-time adjustment of the temperature of the vaporized nitrogen gas, ensuring that the cryogenic nitrogen gas temperature meets the standard during the cooling experiment and guaranteeing the success of the experiment.

[0043] When the liquid manifold 1 is cooled, the temperature sensor 11 on the liquid manifold 1 measures that the temperature inside the liquid manifold 1 drops to -100°C, at which point the cooling of the liquid manifold 1 is complete; when the volatile gas manifold 2 is cooled, the temperature sensor 11 on the volatile gas manifold 2 measures that the temperature inside the volatile gas manifold 2 drops to -100°C, at which point the cooling of the volatile gas manifold 2 is complete; when the gas manifold 3 is cooled, the temperature sensor 11 on the gas manifold 3 measures that the temperature inside the gas manifold 3 drops to -100°C, at which point the cooling of the gas manifold 3 is complete.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A cryogenic pipeline cooling test system for LNG carriers, characterized in that, The system includes a liquid main pipe, a volatile gas main pipe, a gas main pipe, and a liquid nitrogen vaporization module. The stern of the liquid main pipe is connected to a temporary venting mast, the bow of the liquid main pipe is connected to the bow of the volatile gas main pipe, the stern of the volatile gas main pipe is connected to the stern of the gas main pipe, the bow of the volatile gas main pipe is connected to the venting mast, and the bow of the gas main pipe is connected to the venting mast. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank, a vaporizer, and a spray short pipe. The liquid nitrogen storage tank is connected to the vaporizer through a liquid nitrogen main pipeline, the vaporizer is connected to the spray short pipe, and the spray short pipe is connected to the liquid main pipe, the volatile gas main pipe, and the gas main pipe respectively through nitrogen branch pipes.

2. The cryogenic pipeline cooling test system for LNG carriers according to claim 1, characterized in that, A valve is installed on the pipeline connecting the liquid main to the temporary ventilation mast. Temperature sensors are installed at the bow and stern of the liquid main. The bow of the liquid main is connected to the bow of the volatile gas main through a detachable elbow. A valve is installed between the liquid main and the detachable elbow.

3. The cryogenic pipeline cooling test system for LNG carriers according to claim 1, characterized in that, Temperature sensors are installed at the bow and stern of the main volatile gas pipe, and valves are installed on the pipeline connecting the bow of the main volatile gas pipe to the ventilation mast.

4. The cryogenic pipeline cooling test system for LNG ships according to claim 1, characterized in that, Temperature sensors are installed at the bow and stern of the gas main, and valves are installed on the pipeline connecting the bow of the gas main to the ventilated mast.

5. A cryogenic pipeline cooling test system for LNG carriers according to claim 1, characterized in that, Four valves are installed on the main liquid nitrogen pipeline between the liquid nitrogen storage tank and the vaporizer, namely the first valve, the second valve, the third valve and the fourth valve. Valves are also installed on the nitrogen branch pipes that connect the spray short pipe to the gas main pipe and the volatile gas main pipe.

6. A cryogenic pipeline cooling test system for LNG carriers according to claim 5, characterized in that, The spray pipe is connected to the main liquid nitrogen pipeline between the third valve and the fourth valve. A fifth valve is installed on the pipeline connecting the spray pipe to the main liquid nitrogen pipeline. A valve is installed on the outlet pipeline of the spray pipe.

7. A method for cryogenic pipeline cooling tests on LNG carriers, characterized in that, The method specifically includes the following steps: S1. Prepare a cryogenic pipeline cooling test system for LNG ships. The system includes a liquid main, a volatile gas main, a gas main, and a liquid nitrogen vaporization module. The stern of the liquid main is connected to a temporary ventilated mast, the bow of the liquid main is connected to the bow of the volatile gas main, the stern of the volatile gas main is connected to the stern of the gas main, and the bow of the gas main is connected to the ventilated mast. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank, a vaporizer, and a spray pipe. The liquid nitrogen storage tank is connected to the vaporizer through a liquid nitrogen main pipeline, the vaporizer is connected to the spray pipe, and the spray pipe is connected to the liquid main, the volatile gas main, and the gas main through nitrogen branch pipes, respectively. S2, Liquid main cooling: Open the first, second, third, and fourth valves on the main liquid nitrogen pipeline, and open the valves on the nitrogen branch pipe leading to the liquid main. Liquid nitrogen in the liquid nitrogen storage tank is vaporized through the vaporizer in the main liquid nitrogen pipeline and then flows to the liquid main. The cryogenic nitrogen entering the liquid main cools the liquid main. At the same time, temperature sensors at the bow and stern of the liquid main detect the temperature of the liquid main. Meanwhile, the cryogenic nitrogen flows through the valves at the bow and stern of the liquid main to the volatile gas main and the temporary venting mast, respectively. S3, while the cryogenic nitrogen cools the liquid main, the cryogenic nitrogen flowing to the volatile gas main through the detachable elbow pre-cools the volatile gas main. After the liquid main is cooled, close the valve on the cryogenic nitrogen branch pipe leading to the liquid main and the valve at the connection between the liquid main and the volatile gas main. S4, evaporative gas main pipe cooling: open the branch pipe valve leading to the evaporative gas main pipe, open the valve on the pipeline connecting the evaporative gas main pipe and the ventilation mast, open the valve on the pipeline connecting the gas main pipe and the ventilation mast, and low-temperature nitrogen enters the evaporative gas main pipe to cool it. Low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the evaporative gas main pipe and the gas main pipe to pre-cool the gas main pipe. S5, Gas main pipe cooling: After the volatile gas main pipe is cooled, close the branch pipe valve leading to the volatile gas main pipe and open the branch pipe valve leading to the gas main pipe. Low-temperature nitrogen gas is used to cool the gas main pipe. During the cooling process, the low-temperature nitrogen gas flows to the ventilated mast through the volatile gas main pipe and the gas main pipe. S6. After the gas main pipe has cooled down, close the valve on the liquid nitrogen main pipe to stop supplying cryogenic nitrogen to the gas main pipe. After the cryogenic nitrogen in the liquid main pipe, volatile gas main pipe and gas main pipe has been completely discharged through the venting mast and temporary venting mast, close all the valves on the pipes to complete the cryogenic pipeline cooling test.

8. A method for cryogenic pipeline cooling test of an LNG ship according to claim 7, characterized in that, The temperature of the cryogenic nitrogen gas output from the spray short pipe is -140℃. When the temperature of the liquid nitrogen after vaporization by the vaporizer does not reach -140℃, the valve connecting the spray short pipe and the liquid nitrogen main pipe is opened, allowing the liquid nitrogen to directly enter the spray short pipe and mix with the vaporized nitrogen gas, thereby reducing the temperature of the nitrogen gas output from the spray short pipe to -140℃.

9. A method for cryogenic pipeline cooling test of an LNG ship according to claim 7, characterized in that, When the liquid manifold is cooled, the cooling process is complete when the temperature sensor on the liquid manifold measures that the temperature inside the liquid manifold has dropped to -100°C. Similarly, when the volatile gas manifold is cooled, the cooling process is complete when the temperature sensor on the volatile gas manifold measures that the temperature inside the volatile gas manifold has dropped to -100°C. Likewise, when the gas manifold is cooled, the cooling process is complete when the temperature sensor on the gas manifold measures that the temperature inside the gas manifold has dropped to -100°C.

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