Method for discharging residual tightness test gas in insulating layer of LNG liquid cargo tank
By installing pipelines in the LNG cargo tank and utilizing a combination of vacuum pumps and warm gas, the problem of helium residue in the insulation layer was resolved, enabling efficient helium discharge, improving the performance of the insulation layer and the ship's operating efficiency.
Patent Information
- Application Number
- CN202510998660.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-10-17
AI Technical Summary
The residual helium in the insulation layer of the LNG cargo tank affects the insulation effect, and existing technology is difficult to efficiently remove it.
By installing pipes at the top and bottom of the liquid cargo tank and using a vacuum pump to create a vacuum, warm gas, especially nitrogen, is injected to carry and squeeze out the residual helium, and the characteristic that nitrogen molecules are larger than helium molecules is used to speed up the discharge.
It effectively discharges the helium in the insulation layer, improves the efficiency of the insulation layer, shortens the operation time, and improves the operation efficiency of the ship.
Smart Images
Figure CN120793084A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of shipbuilding technology, in particular to a method for discharging residual tightness test gas in the insulation layer of LNG liquid cargo tank. BACKGROUND
[0002] During the construction of the LNG liquid cargo tank, the tightness of the insulation layer shielding needs to be tested by using tracer gas, and helium is usually used as the tracer gas. The helium will remain in the insulation layer at the end of the tightness test. At present, polyurethane foam material is often used as the insulation layer. Since the thermal conductivity of helium is much larger than that of nitrogen and dry air, the helium remaining in the insulation layer will have an adverse effect on the insulation effect. Therefore, it is necessary to discharge the helium remaining in the insulation layer of the cargo tank. SUMMARY
[0003] Therefore, the present application provides a method for discharging residual tightness test gas in the insulation layer of LNG liquid cargo tank to solve the problems in the background art.
[0004] A method for discharging residual tightness test gas in the insulation layer of LNG liquid cargo tank, comprising the following steps:
[0005] S1, installing a first pipeline and a second pipeline at the top of the LNG liquid cargo tank, and installing a third pipeline and a fourth pipeline at the bottom of the LNG liquid cargo tank, one end of the first pipeline extends into a first annular space from the top of the liquid cargo tank, and the other end is connected to a first control valve, one end of the second pipeline extends into a second annular space from the top of the liquid cargo tank, and the other end is also connected to the first control valve, and the first control valve is connected to a vacuum pump; one end of the third pipeline extends into the first annular space from the bottom of the liquid cargo tank, and the other end is connected to a second control valve, one end of the fourth pipeline extends into the second annular space from the bottom of the liquid cargo tank, and the other end is also connected to the second control valve, and the second control valve is connected to a gas source, and the first pipeline and the second pipeline are both connected with an exhaust pipe;
[0006] The first annular space is located between the main layer insulation layer and the secondary layer insulation layer, and the second annular space is located between the secondary layer insulation layer and the ship structure;
[0007] S2, using the vacuum pump to vacuum the first annular space and the second annular space, and then using the gas source to introduce warm gas into the first annular space and the second annular space, and using the warm gas to carry and extrude the residual tightness test gas in the first annular space and the second annular space.
[0008] Preferably, pressure sensors are arranged on the first pipeline, the second pipeline, the third pipeline and the fourth pipeline, and temperature sensors are arranged on the third pipeline and the fourth pipeline,
[0009] The specific steps of step S2 are:
[0010] First, open the first control valve, close the second control valve, use the vacuum pump to draw the first annular space and the second annular space to a set vacuum degree through the first pipeline and the second pipeline, and maintain the pressure for a set time;
[0011] During the pressure maintaining process, the pressure changes in the first annular space and the second annular space are monitored in real time according to the pressure sensors on the first pipeline, the second pipeline, the third pipeline and the fourth pipeline;
[0012] After the pressure in the first annular space and the second annular space is stabilized, the vacuum pump is closed, warm gas is injected into the first annular space and the second annular space through the third pipeline and the fourth pipeline, and when the temperature in the first annular space and the second annular space is not higher than a set temperature value and the pressure is not higher than a set pressure value, the exhaust pipe on the first pipeline and the second pipeline is opened, and the residual airtightness test gas in the first annular space and the second annular space is carried and extruded by the warm gas.
[0013] Preferably, during the process of carrying and extruding the residual airtightness test gas in the first annular space and the second annular space by the warm gas, the concentration of the residual airtightness test gas at the exhaust port of the exhaust pipe is monitored by a gas detector, and if the concentration of the residual airtightness test gas at the exhaust port of the exhaust pipe is continuously higher than a set concentration for a period of time, the step S2 is repeatedly executed until the requirement is met.
[0014] Preferably, the method can be performed synchronously with the warming operation of the LNG liquid cargo tank.
[0015] Preferably, the method can be performed synchronously with the insulation layer negative pressure extraction operation of the global test of the LNG liquid cargo tank.
[0016] Preferably, a safety device is further arranged on the pipeline section of the third pipeline or the fourth pipeline close to the liquid cargo tank.
[0017] Preferably, the first pipeline and the second pipeline are both single pipes, wherein the pipeline end of the first pipeline extends to the upper part of the first annular space, and the pipeline end of the second pipeline extends to the upper middle part of the second annular space; or the pipeline end of the first pipeline extends to the upper middle part of the first annular space, and the pipeline end of the second pipeline extends to the upper part of the second annular space.
[0018] Preferably, the first pipeline and the second pipeline are both pipelines with double branches, and the end of one branch of both extends to the upper part of the corresponding annular space, and the end of the other branch extends to the upper middle part of the corresponding annular space.
[0019] The beneficial effects of the present application are:
[0020] 1. The present invention utilizes a vacuum pump to draw vacuum from the top of the first annular space and the second annular space, thereby discharging most of the helium in the two annular spaces. Then, nitrogen is injected from the bottom of the two annular spaces, and the nitrogen with large molecules displaces the helium with small molecules remaining in the pores of the insulating layer structure, thereby completely discharging the residual helium. The injected nitrogen has a certain temperature, which can increase the activity of the helium and accelerate the discharge speed of the helium, thereby greatly improving the discharge efficiency of the helium in the annular space.
[0021] 2. In the present invention, when the first annular space and the second annular space are evacuated, the third pipeline and the fourth pipeline can serve as connecting pipes to connect the first annular space and the second annular space to ensure that the pressures in the two annular spaces are equal and the pressures at different positions in each annular space are stable and balanced, thereby ensuring smooth subsequent nitrogen injection.
[0022] 3. The method of the present invention can be carried out simultaneously with the warming operation of the LNG liquid cargo tank. When carried out simultaneously with the warming operation, the temperature of the warm gas injected into the first annular space and the second annular space needs to reach about 60°C. This can better heat the air temperature in the annular space, heat the activity of the residual tightness test gas, and discharge the residual tightness test gas faster.
[0023] 4. The method of the present invention can be carried out simultaneously with the negative pressure pumping operation of the insulation layer for the global test of the LNG liquid cargo tank. After the negative pressure pumping operation of the insulation layer for the global test of the LNG liquid cargo tank shielding layer is completed, warm gas can be continuously injected into the two annular spaces to discharge the residual tightness test gas, which can greatly shorten the operation time of the ship and improve the operation efficiency of the ship. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0025] Figure 1 It is a structural schematic diagram of the present invention.
[0026] The meanings of the numbers in the figure are:
[0027] 1 is the first pipeline, 2 is the second pipeline, 3 is the third pipeline, 4 is the fourth pipeline, 5 is the first annular space, 6 is the second annular space, 7 is the first control valve, 8 is the vacuum pump, 9 is the second control valve, 10 is the gas source, 11 is the safety device, 12 is the exhaust pipe, 13 is the pressure sensor, and 14 is the temperature sensor. DETAILED DESCRIPTION
[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described in detail below with reference to the specific embodiments shown in the drawings. However, it should be understood that the description is only exemplary and is not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.
[0029] The terms used in the present disclosure are merely for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a," "an," and "the" used in the present disclosure and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.
[0030] It should be understood that although the terms first, second, etc. can be used in the present disclosure to describe various information, these information should not be limited to these terms, and should not be understood as indicating or implying relative importance. These terms are only used to distinguish one type of information from another type of information. For example, without departing from the scope of the present disclosure, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "when" or "upon" or "in response to determining".
[0031] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0032] In the description of the present application, unless otherwise specified and limited, it should be noted that the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be a mechanical connection or an electrical connection, it can be a communication between two elements, it can be a direct connection or an indirect connection through an intermediate medium, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.
[0033] In order to better understand the technical solutions of the present application, the present application will be described in detail below with reference to the drawings.
[0034] The present application provides a method for discharging the residual airtight test gas in the insulation layer of LNG liquid cargo tank, which specifically comprises the following steps:
[0035] S1, installing the first pipe 1 and the second pipe 2 at the top of the LNG liquid cargo tank, and installing the third pipe 3 and the fourth pipe 4 at the bottom of the LNG liquid cargo tank.
[0036] One end of the first pipe 1 extends into the first annular space 5 from the top of the liquid cargo tank, and the other end is connected to the first control valve 7. One end of the second pipe 2 extends into the second annular space 6 from the top of the liquid cargo tank, and the other end is also connected to the first control valve 7. The first control valve 7 is connected to the vacuum pump 8. The first pipe 1 and the second pipe 2 are each provided with a pipe valve for controlling the opening and closing of the pipe. The pipe ends of the first pipe 1 and the second pipe 2 are each connected to an exhaust pipe 12. The pipe sections of the first pipe 1 and the second pipe 2 near the liquid cargo tank are each provided with a pressure sensor 13.
[0037] One end of the third pipe 3 extends into the first annular space 5 from the bottom of the liquid cargo tank, and the other end is connected to the second control valve 9. One end of the fourth pipe 4 extends into the second annular space 6 from the bottom of the liquid cargo tank, and the other end is also connected to the second control valve 9. The second control valve 9 is connected to the gas source 10. The third pipe 3 and the fourth pipe 4 are each provided with a pipe valve for controlling the opening and closing of the pipe. The pipe ends of the third pipe 3 and the fourth pipe 4 are each connected to an exhaust pipe 12. The pipe sections of the third pipe 3 and the fourth pipe 4 near the liquid cargo tank are each provided with a pressure sensor 13. The third pipe 3 and the fourth pipe 4 are also provided with a temperature sensor 14.
[0038] The first annular space 5 is located between the primary insulation layer and the secondary insulation layer. The second annular space 6 is located between the secondary insulation layer and the hull structure.
[0039] S2, using the vacuum pump 8 to vacuumize the first annular space 5 and the second annular space 6, and then using the gas source 10 to introduce warm gas into the first annular space 5 and the second annular space 6, so that the residual airtightness test gas in the first annular space 5 and the second annular space 6 is carried and squeezed out by the warm gas.
[0040] Specifically, first, the first control valve 7 is opened and the second control valve 9 is closed. The vacuum pump 8 is used to vacuumize the first annular space 5 and the second annular space 6 through the first pipe 1 and the second pipe 2. During the vacuumizing process, the exhaust pipe 12 is in a closed state, and the pipe valves on the first pipe 1, the second pipe 2, the third pipe 3, and the fourth pipe 4 are all in an open state. Therefore, the third pipe 3 and the fourth pipe 4 can be used as a communication pipe to connect the first annular space 5 and the second annular space 6 to ensure that the pressures in the two annular spaces are equal and that the pressures at different positions in each annular space are stable and balanced.
[0041] When the vacuum degrees of the first annular space 5 and the second annular space 6 reach the set vacuum degrees, the pressure is maintained for a period of time, and during the pressure maintaining process, the pressure changes in the first annular space 5 and the second annular space 6 are monitored in real time according to the pressure sensors 13 on the first pipeline 1, the second pipeline 2, the third pipeline 3 and the fourth pipeline 4;
[0042] When the pressures in the first annular space 5 and the second annular space 6 are stable, the vacuum pump 8 and the first control valve 7 are closed, the second control valve 9 and the exhaust pipe 12 are opened, and the pipeline valve pieces on the first pipeline 1, the second pipeline 2, the third pipeline 3 and the fourth pipeline 4 still remain in the opened state. Warm gas is injected into the first annular space 5 and the second annular space 6 through the third pipeline 3 and the fourth pipeline 4 by using the gas source 10, and the temperature and pressure changes in the first annular space 5 and the second annular space 6 are monitored in real time by the temperature sensor 14 and the pressure sensor 13 during the process of injecting the warm gas. When the temperature in the first annular space 5 and the second annular space 6 is not higher than 30℃ and the pressure exceeds the normal atmospheric pressure (the difference between the pressure in the first annular space 5 and the second annular space 6 and the normal atmospheric pressure is not more than 30mbarg), the exhaust pipe 12 on the first pipeline 1 and the second pipeline 2 is opened, and the residual airtight test gas in the first annular space 5 and the second annular space 6 is carried and extruded out by using the warm gas (since the molecules of the warm gas are larger than those of the residual airtight test gas, the residual airtight test gas can be discharged in the process of the warm gas flowing upward from the bottom of the annular space; and the warm gas can increase the temperature of the primary and secondary insulation layers, can increase the activity of the residual airtight test gas remaining in the structure gap of the primary and secondary insulation layers, and can speed up the extrusion of the residual airtight test gas). The mixture of the residual airtight test gas and the warm gas is discharged along the first pipeline 1 and the second pipeline 2, and is discharged from the exhaust pipe 12 on the two pipelines.
[0043] During the process of carrying and extruding out the residual airtight test gas in the first annular space 5 and the second annular space 6 by using the warm gas, the concentration of the residual airtight test gas at the exhaust port of the exhaust pipe 12 is monitored by using the gas detector. If the concentration of the residual airtight test gas at the exhaust port of the exhaust pipe 12 continuously exceeds the set concentration for a period of time, the step S2 is repeatedly executed until the requirement is met. If the concentration of the residual airtight test gas at the exhaust port of the exhaust pipe 12 gradually decreases, the warm gas can be continuously injected until the discharged residual airtight test gas reaches the set requirement.
[0044] In the embodiment, the airtight test gas is helium, and the warm gas can be selected from nitrogen or dry gas, and the warm gas is preferably nitrogen.
[0045] In the embodiment, the first pipeline 1 and the second pipeline 2 are both single pipes, and the end of the first pipeline 1 extends to the upper part of the first annular space 5, and the end of the second pipeline 2 extends to the upper-middle part of the second annular space 6; or the end of the first pipeline 1 extends to the upper-middle part of the first annular space 5, and the end of the second pipeline 2 extends to the upper part of the second annular space 6, that is, the end of one of the first pipeline 1 and the second pipeline 2 is located at the top of the first annular space 5, and the end of the other pipeline is located at the upper-middle part of the second annular space 6, which is 1 / 4-1 / 3h from the top, where h is the height of the liquid cargo tank. By placing the ends of the first pipeline 1 and the second pipeline 2 at different heights of the two annular spaces, the balance and stability of the pressure of the two annular spaces can be further ensured when the two annular spaces are vacuumized.
[0046] In another embodiment, the first pipeline 1 and the second pipeline 2 are both pipelines with double branches, and the end of one of the two branches of each pipeline extends to the top of the corresponding annular space, and the end of the other branch extends to the upper-middle part of the second annular space 6, which is 1 / 4-1 / 3h from the top, where h is the height of the liquid cargo tank. By placing the ends of the first pipeline 1 and the second pipeline 2 at different heights of the corresponding annular spaces, the rate at which the two annular spaces reach the set vacuum degree can be accelerated when the two annular spaces are vacuumized, and the balance and stability of the pressure of the two annular spaces can be further ensured.
[0047] In a preferred embodiment, a safety device 11 is further arranged on the pipe section of the third pipeline 3 or the fourth pipeline 4 close to the liquid cargo tank. Before the first annular space 5 and the second annular space 6 are vacuumized, the safety device 11 needs to be opened, and the pressure safety threshold is set to -800 mbarg. If the pressure in the annular space exceeds the set safety threshold during the process of removing the residual density test gas, an alarm prompt can be sent. The safety device 11 can be a safety valve.
[0048] In a preferred embodiment, the above-mentioned method of the present application can be performed synchronously with the warming operation of the LNG liquid cargo tank. In the embodiment, the temperature of the warm gas injected into the first annular space 5 and the second annular space 6 needs to reach about 60°C, which can better heat the air temperature in the annular space and activate the residual density test gas, so that the residual density test gas can be removed faster.
[0049] In the preferred embodiment, the above-mentioned method of the present application can be performed synchronously with the insulation layer vacuumizing operation of the global test of the LNG liquid cargo tank. In this embodiment, the first annular space 5 and the second annular space 6 are vacuumized to -800 mbarg. After the insulation layer vacuumizing operation of the global test of the LNG liquid cargo tank is completed, the warm gas can be continuously injected into the two annular spaces to discharge the residual gas of the tightness test.
[0050] It should be noted that the embodiments described above are merely some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.
Claims
1. A method for discharging residual tightness test gas in the insulation layer of an LNG cargo tank, characterized in that: The specific steps include: S1, a first pipeline (1) and a second pipeline (2) are installed on the top of the LNG cargo tank, and a third pipeline (3) and a fourth pipeline (4) are installed on the bottom of the LNG cargo tank, one end of the first pipeline (1) extends from the top of the cargo tank into the first annular space (5), and the other end is connected to the first control valve (7), one end of the second pipeline (2) extends from the top of the cargo tank into the second annular space (6), and the other end is also connected to the first control valve (7), and the first control valve (7) is connected to a vacuum pump (8); one end of the third pipeline (3) extends from the bottom of the cargo tank into the first annular space (5), and the other end is connected to the second control valve (9), one end of the fourth pipeline extends from the bottom of the cargo tank into the second annular space (6), and the other end is also connected to the second control valve (9), and the second control valve (9) is connected to a gas source (10), and the first pipeline (1) and the second pipeline (2) are both connected to an exhaust pipe (12); The first annular space (5) is located between the primary insulation layer and the secondary insulation layer, and the second annular space (6) is located between the secondary insulation layer and the hull structure; S2, using a vacuum pump (8) to evacuate the first annular space (5) and the second annular space (6), and then using a gas source (10) to introduce warm gas into the first annular space (5) and the second annular space (6), and using the warm gas to carry and squeeze out the residual tightness test gas in the first annular space (5) and the second annular space (6).
2. The method for discharging the residual tightness test gas in the insulation layer of the LNG cargo tank according to claim 1, characterized in that: The first pipeline (1), the second pipeline (2), the third pipeline (3) and the fourth pipeline (4) are all provided with pressure sensors (13), and the third pipeline (3) and the fourth pipeline (4) are provided with temperature sensors (14). The specific steps of step S2 are: First, the first control valve (7) is opened, the second control valve (9) is closed, and the first annular space (5) and the second annular space (6) are evacuated to a set vacuum degree through the first pipeline (1) and the second pipeline (2) by a vacuum pump (8), and the pressure is maintained for a set time; During the pressure maintenance process, the pressure changes in the first annular space (5) and the second annular space (6) are measured in real time based on the pressure sensors (13) on the first pipeline (1), the second pipeline (2), the third pipeline (3) and the fourth pipeline (4); After the pressure in the first annular space (5) and the second annular space (6) is stabilized, the vacuum pump (8) is turned off, and warm gas is injected into the first annular space (5) and the second annular space (6) through the third pipeline (3) and the fourth pipeline (4) using the gas source (10). When the temperature in the first annular space (5) and the second annular space (6) is not higher than the set temperature value and the pressure is not higher than the set pressure value, the exhaust pipe (12) on the first pipeline (1) and the second pipeline (2) is opened, and the residual tightness test gas in the first annular space (5) and the second annular space (6) is carried and squeezed out by the warm gas.
3. The method for discharging the residual tightness test gas in the insulation layer of the LNG liquid cargo tank according to claim 2, characterized in that: In the process of using warm gas to carry and squeeze out the residual tightness test gas in the first annular space (5) and the second annular space (6), a gas detector is used to monitor the concentration of the residual tightness test gas at the exhaust port of the exhaust pipe (12). If the concentration of the residual tightness test gas at the exhaust port of the exhaust pipe (12) continues to be higher than the set concentration for a period of time, step S2 is repeated until the requirement is met.
4. The method for discharging the residual tightness test gas in the insulation layer of the LNG cargo tank according to claim 1, characterized in that: The method can be performed simultaneously with the warming operation of the LNG liquid cargo tank.
5. The method for discharging the residual tightness test gas in the insulation layer of the LNG liquid cargo tank according to claim 1, characterized in that: The method can be performed simultaneously with the negative pressure pumping operation of the insulation layer in the global test of the LNG liquid cargo tank.
6. The method for discharging the residual tightness test gas in the insulation layer of the LNG liquid cargo tank according to claim 1, characterized in that: A safety device (11) is also provided on the pipe section of the third pipeline (3) or the fourth pipeline (4) close to the liquid cargo tank.
7. The method for discharging the residual tightness test gas in the insulation layer of the LNG liquid cargo tank according to claim 1, characterized in that: The first pipeline (1) and the second pipeline (2) are both single pipes, wherein the pipeline end of the first pipeline (1) extends to the upper part of the first annular space (5), and the pipeline end of the second pipeline (2) extends to the middle and upper part of the second annular space (6); or the pipeline end of the first pipeline (1) extends to the middle and upper part of the first annular space (5), and the pipeline end of the second pipeline (2) extends to the upper part of the second annular space (6).
8. The method for discharging the residual tightness test gas in the insulation layer of the LNG liquid cargo tank according to claim 1, characterized in that: The first pipeline (1) and the second pipeline (2) are both pipelines with double branches, one end of each branch extending to the upper part of the corresponding annular space, and the other end extending to the middle upper part of the corresponding annular space.