Low-temperature pipeline cooling test system and method for LNG (Liquefied Natural Gas) ship

Abstract

The invention discloses an LNG (liquefied natural gas) ship low-temperature pipeline cooling test system, which comprises a liquid header pipe, a volatile gas header pipe, a gas header pipe and a liquid nitrogen vaporization module, and is characterized in that the stern of the liquid header pipe is communicated with a temporary ventilation mast, the bow of the liquid header pipe is communicated with the bow of the volatile gas header pipe, and the stern of the volatile gas header pipe is communicated with the stern of the gas header pipe; the liquid nitrogen vaporization module comprises a liquid nitrogen storage tank, a vaporizer and a spraying short pipe, the liquid nitrogen storage tank is communicated with the vaporizer through a liquid nitrogen main pipeline, the vaporizer is communicated with the spraying short pipe, and the liquid nitrogen main pipeline is communicated with the spraying short pipe. And the spraying short pipe is respectively communicated with the liquid main pipe, the volatile gas main pipe and the gas main pipe through nitrogen branch pipes. According to the invention, one pipeline is cooled and the other pipelines are precooled at the same time, so that the precooling time of the pipelines is saved, the situation that each pipeline needs to be cooled from a normal temperature state when being cooled is avoided, the precooling time of the pipelines is saved, and the test period is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of shipbuilding, and in particular relates to a low-temperature pipeline cooling test system and method for LNG ships. Background Art

[0002] A membrane LNG carrier is a special ship used to transport liquefied natural gas at -163°C. Before the ship is officially put into operation, a cooling test is required on the pipeline to ensure that the construction quality of the LNG cryogenic liquid cargo system pipeline meets the design requirements.

[0003] In the traditional cooling test, there are the following two defects:

[0004] 1. Long cooling time. In the traditional cooling experiment, a vaporizer is used to vaporize liquid nitrogen and cool each pipeline separately without connecting to each other, and the initial state of each pipeline is room temperature. When the liquid main pipe is cooled, the volatile gas main pipe and the gas main pipe are still at room temperature. Depending on the external ambient temperature, the cooling time of each pipeline takes about 4-8 hours, and the detection time is about 1-2 hours, resulting in a lot of time wasted on pipeline precooling.

[0005] 2. Large consumption of liquid nitrogen. In traditional cooling experiments, after cooling a single pipeline, the cold air in the pipeline will be directly discharged, resulting in waste of liquid nitrogen and energy consumption. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and to provide a system and method for cooling a low-temperature pipeline of an LNG ship. The present invention saves the time for precooling the pipelines by cooling one pipeline while precooling other pipelines, avoids cooling each pipeline from room temperature, saves the time for cooling the pipelines and makes full use of the time for pipeline inspection. When inspecting the pipelines, this method can still precool other pipelines, reduces the time for cooling other pipelines to the specified temperature, and shortens the test cycle.

[0007] In order to achieve the above invention purpose, the technical solution provided by the present invention is as follows:

[0008] A low-temperature pipeline cooling test system for an LNG ship, the system comprises 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 with a temporary ventilation mast, the bow of the liquid main pipe is connected with the bow of the volatile gas main pipe, the stern of the volatile gas main pipe is connected with the stern of the gas main pipe, the bow of the volatile gas main pipe is connected with the ventilation mast, the bow of the gas main pipe is connected with the ventilation mast, the liquid nitrogen vaporization module comprises a liquid nitrogen storage tank, a vaporizer and a spray short pipe, the liquid nitrogen storage tank is connected with the vaporizer through a liquid nitrogen main pipeline, the vaporizer is connected with the spray short pipe, and the spray short pipe is connected with the liquid main pipe, the volatile gas main pipe and the gas main pipe respectively through nitrogen branch pipes.

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

[0010] Furthermore, the bow and stern of the volatile gas main pipe are respectively provided with temperature sensors, and a valve is provided on the pipeline connecting the volatile gas main pipe and the air-permeable mast.

[0011] Furthermore, the bow and stern of the gas main pipe are respectively provided with temperature sensors, and a valve is provided on the pipeline connecting the gas main pipe and the air-permeable mast.

[0012] Furthermore, four valves are arranged on the liquid nitrogen main line 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 arranged on the nitrogen branch pipes connecting the spray short pipe with the gas main pipe and the volatile gas main pipe.

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

[0014] A method for cooling a cryogenic pipeline of an LNG ship, the method specifically comprising the following steps:

[0015] S1. Prepare a low-temperature pipeline cooling test system for LNG ships, the system comprising 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 ventilation 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 gas main pipe is connected to the ventilation mast, the liquid nitrogen vaporization module comprises 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 pipe, 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;

[0016] S2, cooling of the liquid main pipe, opening the first valve, the second valve, the third valve and the fourth valve on the liquid nitrogen main pipe, opening the valve on the nitrogen branch pipe leading to the liquid main pipe, the liquid nitrogen in the liquid nitrogen storage tank is vaporized through the liquid nitrogen main pipe and passed through the vaporizer, and then leads to the liquid main pipe; the low-temperature nitrogen entering the liquid main pipe cools the liquid main pipe, and the temperature sensors arranged at the bow and stern of the liquid main pipe detect the temperature of the liquid main pipe, and the low-temperature nitrogen flows to the volatile gas main pipe and the temporary ventilation mast respectively through the valves arranged at the bow and stern of the liquid main pipe;

[0017] S3, while the cryogenic nitrogen cools the liquid main pipe, the cryogenic nitrogen flowing to the volatile gas main pipe through the detachable elbow pre-cools the volatile gas main pipe. When the cooling of the liquid main pipe is completed, the valve on the cryogenic nitrogen branch pipe leading to the liquid main pipe and the valve at the connection between the liquid main pipe and the volatile gas main pipe are closed;

[0018] S4, cooling the volatile gas main pipe, opening the branch pipe valve leading to the volatile gas main pipe, opening the valve on the pipeline connecting the volatile gas main pipe and the vent mast, opening the valve on the pipeline connecting the gas main pipe and the vent mast, and allowing low-temperature nitrogen to enter the volatile gas main pipe to cool the volatile gas main pipe. The low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the volatile gas main pipe and the gas main pipe to pre-cool the gas main pipe;

[0019] S5, cooling of the gas main pipe. When the cooling of the volatile gas main pipe is completed, the branch pipe valve leading to the volatile gas main pipe is closed, and the branch pipe valve leading to the gas main pipe is opened. The low-temperature nitrogen cools the gas main pipe. During the cooling process, the low-temperature nitrogen flows to the vent mast through the volatile gas main pipe and the gas main pipe;

[0020] S6. When the gas main is cooled, close the valve on the liquid nitrogen main line and stop delivering cryogenic nitrogen to the gas main. When the cryogenic nitrogen in the liquid main, volatile gas main and gas main is completely discharged through the ventilation mast and temporary ventilation mast, close the valves on all pipelines to complete the cryogenic pipeline cooling test.

[0021] Furthermore, the temperature of the low-temperature nitrogen when it is output from the spray short tube is -140°C. When the temperature of the liquid nitrogen after being vaporized by the vaporizer does not reach -140°C, the valve connecting the spray short tube and the liquid nitrogen main tube is opened to allow the liquid nitrogen to directly enter the spray short tube and mix with the vaporized nitrogen, so that the temperature of the nitrogen output from the spray short tube is reduced to -140°C.

[0022] Further, when the liquid main is cooled, the temperature sensor on the liquid main measures that the temperature inside the liquid main drops to -100°C, and the cooling of the liquid main is completed; when the volatile gas main is cooled, the temperature sensor on the volatile gas main measures that the temperature inside the volatile gas main drops to -100°C, and the cooling of the volatile gas main is completed; when the gas main is cooled, the temperature sensor on the gas main measures that the temperature inside the gas main drops to -100°C, and the cooling of the gas main is completed.

[0023] Based on the above technical solution, the present invention patented a system and method for cooling test of low temperature pipelines of LNG ships, which has achieved the following technical advantages through practical application:

[0024] 1. Compared with conventional solutions, the present invention is a method for cooling low-temperature pipelines of LNG ships. By cooling one pipeline, the other pipelines are pre-cooled, which saves the time for pre-cooling the pipelines, avoids cooling each pipeline from a normal temperature state, saves the cooling time of the pipelines and makes full use of the pipeline inspection time. When inspecting the pipelines, this method can still pre-cool other pipelines, reduces the time for cooling other pipelines to the specified temperature, and shortens the test period. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention discloses a cooling pipeline diagram of a liquid main pipe used in a low-temperature pipeline cooling test system of an LNG ship.

[0026] Figure 2 The present invention discloses a cooling pipeline diagram of a volatile gas main pipe used in a low-temperature pipeline cooling test system of an LNG ship.

[0027] Figure 3 The present invention discloses a gas main cooling pipeline diagram for use in a low-temperature pipeline cooling test system of an LNG ship. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0029] like Figure 1-3 As shown, the present invention belongs to a low-temperature pipeline cooling test system for LNG ships, which 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 ventilation 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 the ventilation mast 5, and the bow of the gas main pipe 3 is connected to the ventilation mast 5. The liquid nitrogen vaporization module includes a liquid nitrogen storage tank 8, a vaporizer 9 and a spray short pipe 10. The liquid nitrogen storage tank 8 is connected to the vaporizer 9 through a liquid nitrogen main line, the vaporizer 9 is connected to the spray short pipe 10, and the spray short pipe 10 is connected to the liquid main pipe 1, the volatile gas main pipe 2, and the gas main pipe 3 through nitrogen branches.

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

[0031] The fore and stern of the volatile gas main pipe 2 are respectively provided with temperature sensors 11 , and the pipeline connecting the volatile gas main pipe 2 and the air-permeable mast 5 is provided with a valve 77 .

[0032] The bow and stern of the gas main pipe 3 are respectively provided with temperature sensors 11 , and the pipeline connecting the gas main pipe 3 and the air-permeable mast 5 is provided with a valve 76 .

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

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

[0035] A method for cooling a cryogenic pipeline of an LNG ship, the method specifically comprising the following steps:

[0036] S1. Prepare a low-temperature pipeline cooling test system for LNG ships, the system comprising 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 ventilation 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 gas main pipe is connected to the ventilation mast, the liquid nitrogen vaporization module comprises 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 pipe, 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;

[0037] S2, cooling of the liquid main pipe, opening the first valve, the second valve, the third valve and the fourth valve on the liquid nitrogen main pipe, opening the valve on the nitrogen branch pipe leading to the liquid main pipe, the liquid nitrogen in the liquid nitrogen storage tank is vaporized through the liquid nitrogen main pipe and passed through the vaporizer, and then leads to the liquid main pipe; the low-temperature nitrogen entering the liquid main pipe cools the liquid main pipe, and the temperature sensors arranged at the bow and stern of the liquid main pipe detect the temperature of the liquid main pipe, and the low-temperature nitrogen flows to the volatile gas main pipe and the temporary ventilation mast respectively through the valves arranged at the bow and stern of the liquid main pipe;

[0038] S3, while the cryogenic nitrogen cools the liquid main pipe, the cryogenic nitrogen flowing to the volatile gas main pipe through the detachable elbow pre-cools the volatile gas main pipe. When the cooling of the liquid main pipe is completed, the valve on the cryogenic nitrogen branch pipe leading to the liquid main pipe and the valve at the connection between the liquid main pipe and the volatile gas main pipe are closed;

[0039] S4, cooling the volatile gas main pipe, opening the branch pipe valve leading to the volatile gas main pipe, opening the valve on the pipeline connecting the volatile gas main pipe and the vent mast, opening the valve on the pipeline connecting the gas main pipe and the vent mast, and allowing low-temperature nitrogen to enter the volatile gas main pipe to cool the volatile gas main pipe. The low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the volatile gas main pipe and the gas main pipe to pre-cool the gas main pipe;

[0040] S5, cooling of the gas main pipe. When the cooling of the volatile gas main pipe is completed, the branch pipe valve leading to the volatile gas main pipe is closed, and the branch pipe valve leading to the gas main pipe is opened. The low-temperature nitrogen cools the gas main pipe. During the cooling process, the low-temperature nitrogen flows to the vent mast through the volatile gas main pipe and the gas main pipe;

[0041] S6. When the gas main is cooled, close the valve on the liquid nitrogen main line and stop delivering cryogenic nitrogen to the gas main. When the cryogenic nitrogen in the liquid main, volatile gas main and gas main is completely discharged through the ventilation mast and temporary ventilation mast, close the valves on all pipelines to complete the cryogenic pipeline cooling test.

[0042] The temperature of the low-temperature nitrogen when it is output from the spray short pipe 10 is -140°C. When the temperature of the liquid nitrogen after being vaporized by the vaporizer 9 does not reach -140°C, the valve 71 connecting the spray short pipe 10 and the nitrogen main pipe is opened to allow the liquid nitrogen to directly enter the spray short pipe 10 and mix with the vaporized nitrogen, so that the temperature of the nitrogen output from the spray short pipe 10 is reduced to -140°C; the spray short pipe 10 and the liquid nitrogen main pipe are connected through the valve 65 to adjust the temperature of the vaporized nitrogen in real time, ensuring that the temperature of the low-temperature nitrogen meets the standard during the cooling experiment and ensuring the success of the experiment.

[0043] When the liquid main pipe 1 is cooled, the temperature sensor 11 on the liquid main pipe 1 measures that the temperature inside the liquid main pipe 1 drops to -100°C, and the cooling of the liquid main pipe 1 is completed at this time; when the volatile gas main pipe 2 is cooled, the temperature sensor 11 on the volatile gas main pipe 2 measures that the temperature inside the volatile gas main pipe 2 drops to -100°C, and the cooling of the volatile gas main pipe 2 is completed at this time; when the gas main pipe 3 is cooled, the temperature sensor 11 on the gas main pipe 3 measures that the temperature inside the gas main pipe 3 drops to -100°C, and the cooling of the gas main pipe 3 is completed at this time.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A low temperature pipeline cooling test system for LNG ships, characterized in that: The system comprises 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 ventilation 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 ventilation mast, and the bow of the gas main pipe is connected to the ventilation mast. The liquid nitrogen vaporization module comprises 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 line, 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 low-temperature pipeline cooling test system for LNG ships according to claim 1 is characterized in that: A valve is provided on the pipeline connecting the liquid main pipe and the temporary ventilation mast, temperature sensors are provided at the bow and stern of the liquid main pipe respectively, the bow of the liquid main pipe is connected with the bow of the volatile gas main pipe through a detachable elbow, and a valve is provided between the liquid main pipe and the detachable elbow.

3. The low temperature pipeline cooling test system for LNG ships according to claim 1 is characterized in that: The bow and stern of the volatile gas main pipe are respectively provided with temperature sensors, and a valve is provided on the pipeline connecting the bow of the volatile gas main pipe with the air-permeable mast.

4. The low temperature pipeline cooling test system for LNG ships according to claim 1 is characterized in that: The bow and stern of the gas main pipe are respectively provided with temperature sensors, and a valve is provided on the pipeline connecting the bow of the gas main pipe with the air-permeable mast.

5. The low temperature pipeline cooling test system for LNG ships according to claim 1 is characterized in that: Four valves are arranged on the liquid nitrogen main line 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 arranged on the nitrogen branch pipes connected with the gas main pipe and the volatile gas main pipe of the spray short pipe.

6. The low-temperature pipeline cooling test system for LNG ships according to claim 5 is characterized in that: The spray short pipe is connected to the liquid nitrogen main line between the third valve and the fourth valve, a fifth valve is arranged on the pipeline connecting the spray short pipe and the liquid nitrogen main line, and a valve is arranged on the spray short pipe outlet pipeline.

7. A method for cooling test of low temperature pipelines of LNG ships, characterized in that: The method specifically comprises the following steps: S1. Prepare a low-temperature pipeline cooling test system for LNG ships, the system comprising 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 ventilation 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 gas main pipe is connected to the ventilation mast, the liquid nitrogen vaporization module comprises 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 pipe, 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; S2, cooling of the liquid main pipe, opening the first valve, the second valve, the third valve and the fourth valve on the liquid nitrogen main pipe, opening the valve on the nitrogen branch pipe leading to the liquid main pipe, the liquid nitrogen in the liquid nitrogen storage tank is vaporized through the liquid nitrogen main pipe and passed through the vaporizer, and then leads to the liquid main pipe; the low-temperature nitrogen entering the liquid main pipe cools the liquid main pipe, and the temperature sensors arranged at the bow and stern of the liquid main pipe detect the temperature of the liquid main pipe, and the low-temperature nitrogen flows to the volatile gas main pipe and the temporary ventilation mast respectively through the valves arranged at the bow and stern of the liquid main pipe; S3, while the cryogenic nitrogen cools the liquid main pipe, the cryogenic nitrogen flowing to the volatile gas main pipe through the detachable elbow pre-cools the volatile gas main pipe. When the cooling of the liquid main pipe is completed, the valve on the cryogenic nitrogen branch pipe leading to the liquid main pipe and the valve at the connection between the liquid main pipe and the volatile gas main pipe are closed; S4, cooling the volatile gas main pipe, opening the branch pipe valve leading to the volatile gas main pipe, opening the valve on the pipeline connecting the volatile gas main pipe and the vent mast, opening the valve on the pipeline connecting the gas main pipe and the vent mast, and allowing low-temperature nitrogen to enter the volatile gas main pipe to cool the volatile gas main pipe. The low-temperature nitrogen enters the gas main pipe through the detachable elbow at the connection between the volatile gas main pipe and the gas main pipe to pre-cool the gas main pipe; S5, cooling of the gas main pipe. When the cooling of the volatile gas main pipe is completed, the branch pipe valve leading to the volatile gas main pipe is closed, and the branch pipe valve leading to the gas main pipe is opened. The low-temperature nitrogen cools the gas main pipe. During the cooling process, the low-temperature nitrogen flows to the vent mast through the volatile gas main pipe and the gas main pipe; S6. When the gas main is cooled, close the valve on the liquid nitrogen main line and stop delivering cryogenic nitrogen to the gas main. When the cryogenic nitrogen in the liquid main, volatile gas main and gas main is completely discharged through the ventilation mast and temporary ventilation mast, close the valves on all pipelines to complete the cryogenic pipeline cooling test.

8. A method for cooling test of low temperature pipelines of LNG ships according to claim 7, characterized in that: The temperature of the low-temperature nitrogen when it is output from the spray short tube is -140°C. When the temperature of the liquid nitrogen after being vaporized by the vaporizer does not reach -140°C, the valve connecting the spray short tube and the liquid nitrogen main tube is opened to allow the liquid nitrogen to directly enter the spray short tube and mix with the vaporized nitrogen, so that the temperature of the nitrogen output from the spray short tube is reduced to -140°C.

9. A method for cooling test of low temperature pipelines of LNG ships according to claim 7, characterized in that: When the liquid main is cooled, the temperature sensor on the liquid main measures that the temperature inside the liquid main drops to -100°C, and the cooling of the liquid main is completed; when the volatile gas main is cooled, the temperature sensor on the volatile gas main measures that the temperature inside the volatile gas main drops to -100°C, and the cooling of the volatile gas main is completed; when the gas main is cooled, the temperature sensor on the gas main measures that the temperature inside the gas main drops to -100°C, and the cooling of the gas main is completed.

Images