A system for monitoring for leaks in the inner tube of a vacuum double-wall tube

Abstract

This invention relates to a leak monitoring system for the inner tube of a vacuum double-walled pipe, belonging to the field of ship design and manufacturing technology. The vacuum double-walled pipe is connected to a venting pipe with a detection pipeline. In the hazardous area, the detection pipeline is sequentially equipped with a first rupture disc, a first check valve, a combustible gas detector, a second rupture disc, and a second check valve. Compared to existing designs, this invention primarily addresses the condition monitoring of vacuum double-walled pipes on large ships and directs potentially released natural gas to the bow venting mast via the venting system, thereby enhancing ship safety.

Description

Technical Field

[0001] This invention relates to an inner tube leakage monitoring system for vacuum double-walled tubes, belonging to the field of ship design and manufacturing technology. Background Technology

[0002] For ships using liquefied natural gas (LNG) fuel, if the LNG refueling system is located in a closed, secure area, the refueling pipeline needs to be designed with double walls. Considering the low-temperature characteristics of LNG, a vacuum-insulated double-walled pipeline and a nitrogen positive-pressure outer pipe with insulation are usually used to transport the LNG from the refueling station to the fuel tank.

[0003] There are two main methods for leak monitoring in vacuum double-walled tubes. One method uses a pressure sensor, whose value is not used as a reference for the vacuum level. When a leak occurs in the inner tube of the vacuum tube, the vacuum level fails, and the pressure rises, causing a qualitative change that can be indirectly monitored. The other method uses a rupture disc. When a leak occurs in the inner tube of the vacuum tube, the liquefied natural gas rapidly vaporizes, the pressure in the outer tube increases, the rupture disc opens, and the natural gas is released locally through the rupture disc outlet or through a separate connection to the vent mast.

[0004] The invention patent "Continuous Vacuum Insulated Double-Wall Pipe (CN109458500A)" applied for by Lu Ningbo et al. of Yada Pipeline Systems Co., Ltd. introduces a continuous vacuum insulated double-wall pipe, which includes several inner pipes and several outer pipes. The outer pipes are sleeved on the outside of the inner pipes. The two adjacent inner pipes are welded together. The two adjacent outer pipes are welded together with a half pipe. Several sets of thermally insulating sliding supports and several sets of thermally insulating fixed supports are provided between the inner pipes and the outer pipes.

[0005] The utility model patent "An assembly for a combustible gas detector installed on a double-walled pipe" (authorization publication number CN217109178U) applied for by Xue Changqi et al. of Hudong-Zhonghua Shipbuilding (Group) Co., Ltd. describes an assembly for a combustible gas detector installed on a double-walled pipe. The assembly includes: a combustible gas detector, a sealing gasket, a flange gasket, a flange seat plate, a locking ring, a junction box, and a junction box base plate. One end of the combustible gas detector has a threaded interface, and the combustible gas detector is fixed to the flange seat plate by a locking ring with internal threads. The sealing gasket is clamped in a groove between the combustible gas detector and the flange seat plate. A signal line at one end of the combustible gas detector is connected to the junction box, and the junction box is fixed to the junction box base plate by bolts. The junction box base plate is vertically welded to the flange seat plate. All components are connected to the flange interface of the outer pipe of the double-walled pipe by bolts. This invention solves the problem of how to install a combustible gas detector on a double-walled pipe, and features a compact layout, easy installation, and convenient maintenance. It mainly introduces the installation assembly for combustible gas detection.

[0006] The utility model patent "A Combustible Gas Combined Sealed Double-Wall Pipe (Authorization Publication No. CN219102267U)" applied for by Wu Jianmin et al. of Hubei Difeng Marine Power Co., Ltd. is specifically a combustible gas combined sealed double-wall pipe, including a combined sealing flange and a double-wall pipe flange; the combined sealing flange and the double-wall pipe flange are connected by an outer pipe and an inner pipe, and the double-wall pipe flange is provided with a ventilation hole one; the combined sealing flange includes an outer flange, an annular bushing, and an inner flange from the outside to the inside, a ventilation hole two is provided between the inner side of the outer flange and the inner flange, and a ventilation hole three is provided between the inner side of the annular bushing and the inner flange, and the ventilation hole one, ventilation hole two, ventilation hole three and the gap between the outer pipe and the inner pipe form a continuous airtight annular space. This invention utilizes a combination of sealing flanges and double-walled pipe flanges to form a continuous, airtight annular space with the outer and inner pipes. The negative pressure ventilation of this airtight annular space allows combustible gases that might leak from the inner pipe due to damage to be expelled, thus meeting the safety isolation requirements of the double-walled intake piping for gas-fueled engines. This patent primarily describes the ventilation double-walled pipe and does not conflict with existing patents.

[0007] For ships fueled by natural gas, a significant portion of the fuel tanks are located within the hull. Refueling pipelines need to pass through enclosed, secure areas. Considering the cryogenic nature of liquefied natural gas (LNG), vacuum-insulated double-walled pipes are a more economical option for refueling. However, existing technologies for monitoring leaks in vacuum double-walled pipes have several drawbacks: ① Using pressure sensors, the sensor values ​​are not used as a reference for vacuum levels. When a leak occurs in the inner tube, the vacuum level fails, and the resulting pressure increase leads to a qualitative change, making indirect monitoring difficult. For crew members, the pressure sensor values ​​can easily mislead them about the vacuum level. ② Using rupture discs requires daily inspection by the crew. When a leak occurs in the inner tube, the LNG rapidly vaporizes, increasing the pressure in the outer tube. This causes the rupture disc to open, releasing the natural gas locally, posing a potential risk to crew and maintenance personnel, and increasing the ship's operational risks. If a separate line is connected to the vent mast for release, the enclosed areas would require double-walled pipes, increasing costs. Summary of the Invention

[0008] The purpose of this invention is to address the problems existing in the vacuum double-walled tube monitoring system mentioned above. Based on the characteristics of liquefied natural gas and combined with the layout of fuel tanks and vented masts on large ships, a special design scheme is adopted to solve the above problems one by one. At the same time, the economic efficiency of construction and the convenience of crew maintenance are considered, making the system design more reasonable and improving the safety of the vacuum double-walled tube leakage monitoring system.

[0009] To achieve the above objectives, the present invention provides a leak monitoring system for the inner tube of a vacuum double-walled tube. The vacuum double-walled tube is connected to a venting pipe and a detection pipe. The detection pipe is provided with a first rupture disc, a first check valve, a combustible gas detector, a second rupture disc, and a second check valve in sequence in the hazardous area.

[0010] Preferably, the detection pipeline is connected to a pressure sensor between the vacuum double-walled tube and the first rupture disc.

[0011] Preferably, it is also connected with a reducer.

[0012] Preferably, the first check valve and the second check valve are shut-off check valves.

[0013] Preferably, the combustible gas detection uses infrared technology.

[0014] Preferably, the combustible gas detector adopts a pipe-type design, with the probe installed inside the pipe.

[0015] Preferably, the first rupture disc and the second rupture disc are made of stainless steel.

[0016] Preferably, the first rupture disc and the second rupture disc are connected by a clamp and installed on the outer tube of the vacuum double-walled tube. When the pressure reaches 1.5 kg, the rupture triggers the combustible gas detection alarm.

[0017] Preferably, the second rupture disc is installed between the combustible gas detector and the second check valve to prevent a small amount of gas from escaping through the valve and causing a false alarm from the combustible gas detector.

[0018] Preferably, the fuel tank safety valve is vented, and the natural gas outlet is connected to the venting pipeline to the bow venting mast.

[0019] In summary, the present invention has the following beneficial technical effects:

[0020] Compared with existing designs, the present invention mainly addresses the status monitoring of vacuum double-walled pipes on large ships and guides potentially released natural gas to the bow vented mast through a venting system, thereby improving ship safety. This system can adapt to different layout schemes, and these are all technical effects directly brought about by the technical features. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a vacuum double-walled tube inner tube leakage monitoring system as an example.

[0022] Reference numerals: 1. Vacuum double-walled tube; 2. Pressure sensor; 3. First rupture disc; 4. First check valve; 5. Combustible gas detector; 6. Second rupture disc; 7. Second check valve; 8. Ventilation double-walled tube; 9. Fuel tank safety valve. Detailed Implementation

[0023] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a leak monitoring system for the inner tube of a vacuum double-walled tube, comprising a detection pipeline connected from the end of the vacuum double-walled tube 1 to a venting pipeline. The detection pipeline is equipped with a pressure sensor 2, a first rupture disc 3, a first check valve 4, a combustible gas detector 5, a second rupture disc 6, a second check valve 7, and a reducing pipe. The first check valve 4 and the second check valve 7 can be shut-off check valves or other types of check valves. The above-mentioned accessories are connected by welding or other means for the arrangement of the combustible gas detector 5 in the vacuum double-walled tube 1.

[0025] The first check valve 4 and the second check valve 7 are made of stainless steel and can withstand certain low temperature requirements. As the main accessories of the inner tube leakage monitoring system of the vacuum double-wall tube 1, they can ensure that the arrangement of the combustible gas detection 5 of the vacuum double-wall tube 1 can withstand the main pressure impact in the opposite direction.

[0026] Pressure sensor 2 is installed between the outer tube of vacuum double-walled tube 1 and the first rupture disc 3. When the combustible gas detector 5 of vacuum double-walled tube 1 alarms, the crew can accurately determine the occurrence of the leak and confirm the specific pipeline of the leak based on the pressure value at that location and the alarm. Pressure sensor 2 is an auxiliary function of combustible gas detector 5.

[0027] The combustible gas detector 5 is designed to monitor leaks in the vacuum double-walled tube 1 and can employ infrared or other suitable methods. The combustible gas detector 5 must meet the corresponding explosion-proof requirements and uses a tube-mounted design; the probe of the combustible gas detector 5 is installed inside the tube.

[0028] The first rupture disc 3 and the second rupture disc 6 are made of stainless steel, designed for a pressure of 1.5 kg, and connected by a compression fitting. They are installed on the outer tube of the vacuum double-wall tube 1. When the inner tube of the vacuum tube is damaged, the liquid LNG or other similar cryogenic fuel will expand rapidly and the pressure will increase. When the pressure reaches 1.5 kg, the rupture disc will rupture, triggering the combustible gas detector 5 to sound an alarm.

[0029] The second rupture disc 6 is installed between the combustible gas detector 5 and the downstream shut-off check valve (or other type of check valve) to prevent trace amounts of gas from escaping through the valve and causing a false alarm in the combustible gas detector 5. Without the second rupture disc 6, the escaped gas has no outlet and will remain in that section of the pipeline. Furthermore, this section of the pipeline cannot be purged, which will prevent the combustible gas detector 5 from resetting. Therefore, the installation of the second rupture disc 6 is very important and is a key arrangement in the combustible gas detector 5 arrangement method used in the vacuum double-walled pipe 1.

[0030] The fuel tank safety valve 9 is vented, and the natural gas outlet is connected to the venting pipeline to the bow venting mast, which saves costs and has a high safety factor.

[0031] All accessories are centrally located at the end of the vacuum double-walled tube 1 in a hazardous area to monitor its operating status. The system outlet is connected to the ventilation system to ensure the reliability of the ship's system and the safety of the crew.

[0032] For ships fueled by natural gas, a significant portion of the fuel tanks are located within the hull, while the refueling station is situated on or below the main deck. The refueling pipelines need to pass through enclosed, secure locations. Considering the low-temperature characteristics of liquefied natural gas, vacuum-insulated double-walled pipes are a more economical choice for refueling pipelines. Leakage monitoring of vacuum double-walled pipes is also important.

[0033] When the inner tube of the vacuum tube is damaged, liquefied natural gas or other similar cryogenic fuels expand rapidly, and the pressure increases. When the pressure reaches 1.5 kg, the rupture disc explodes, triggering the combustible gas detector 5 to alarm. The second rupture disc 6 is installed between the combustible gas detector 5 and the downstream check valve to prevent a small amount of gas from escaping through the valve, causing a false alarm of the combustible gas detector 5.

[0034] When other safety valves or devices in the connected venting pipeline release natural gas, the second check valve 7 can effectively block gas with a pressure greater than 1.5 kg, preventing damage to the second rupture disc 6. The second rupture disc 6 effectively blocks trace amounts of natural gas from entering the combustible gas detector 5, avoiding false alarms.

[0035] Compared to traditional arrangements, this invention provides a leakage monitoring system for the inner tube of a vacuum double-walled tube, offering advantages such as simple installation, high safety and reliability, cost savings, and long service life. The rupture disc features a detachable design, facilitating maintenance and replacement. This invention introduces a novel approach to fuel reliability design, provides crew members with a practical method for detecting gas in vacuum tubes, and offers strong support for shipboard safety monitoring.

[0036] When a leak occurs in the inner tube of the vacuum double-walled tube 1, the vacuum thermal insulation fails. Due to the low temperature characteristics of liquefied natural gas, the natural gas expands rapidly, and the pressure will continue to rise, damaging the rupture disc. This causes the pressure sensor 2 and the combustible gas detector 5 to both alarm. The released gas passes through the venting system to the bow venting mast.

[0037] This invention employs a dual-rupture disc combustible gas detection system 5, which fully considers the issue of trace natural gas leakage, ensuring the normal and safe operation of the system and preventing false alarms caused by trace amounts of natural gas seeping into the combustible gas detector 5 when other safety valves, such as the fuel tank safety valve 9, are opened. At the same time, no purging system is installed in this section of the pipeline, so the system can only be disconnected and purged separately.

[0038] The system outlet is connected to the bow venting mast via a venting pipe to prevent natural gas from being released locally in the event of a leak in the vacuum double-wall pipe 1, which would pose a certain risk. It also avoids having a separate line to the bow venting mast, thus saving costs.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A leak monitoring system for the inner tube of a vacuum double-walled tube, characterized in that, A detection pipeline is connected to the vacuum double-walled tube (1) and the venting pipeline. The detection pipeline is equipped with a first rupture disc (3), a first check valve (4), a combustible gas detector (5), a second rupture disc (6), and a second check valve (7) in sequence in the dangerous area. The first rupture disc (3) and the second rupture disc (6) are connected by a compression fitting and installed on the outer tube of the vacuum double-walled tube (1). When the inner tube of the vacuum double-walled tube (1) is damaged, the first rupture disc (3) ruptures and triggers the combustible gas detector (5) to alarm. The second rupture disc (6) is installed between the combustible gas detector (5) and the second check valve (7) to prevent a small amount of gas from escaping through the second check valve (7) and causing a false alarm of the combustible gas detector (5), and to prevent the combustible gas detector (5) from failing to reset due to a small amount of gas remaining in the section of the pipeline that cannot be purged.

2. The leakage monitoring system for the inner tube of a vacuum double-walled tube according to claim 1, characterized in that, The detection pipeline is connected to a pressure sensor (2) between the vacuum double-wall tube (1) and the first rupture disc (3).

3. The leakage monitoring system for the inner tube of a vacuum double-walled tube according to claim 1, characterized in that, It is also connected to a reducer.

4. A leak monitoring system for the inner tube of a vacuum double-walled tube according to any one of claims 1-3, characterized in that, The first check valve (4) and the second check valve (7) are shut-off check valves.

5. A leak monitoring system for the inner tube of a vacuum double-walled tube according to any one of claims 1-3, characterized in that, The combustible gas detector (5) uses infrared or other suitable methods.

6. A leak monitoring system for the inner tube of a vacuum double-walled tube according to any one of claims 1-3, characterized in that, The combustible gas detector (5) adopts a pipe seat type, with the probe installed inside the pipe.

7. A leak monitoring system for the inner tube of a vacuum double-walled tube according to any one of claims 1-3, characterized in that, The first rupture disc (3) and the second rupture disc (6) are made of stainless steel.

8. A leak monitoring system for the inner tube of a vacuum double-walled tube according to claim 7, characterized in that, The pressure of the first rupture disc (3) and the second rupture disc (6) is set to 1.5 kg.

9. A leak monitoring system for the inner tube of a vacuum double-walled tube according to any one of claims 1-3, characterized in that, The fuel tank safety valve (9) is vented, connecting the natural gas outlet to the vent line to the bow vent mast.

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