Double-wall pipe airtightness detection equipment for LNG (Liquefied Natural Gas) ship

Abstract

The invention relates to the field of double-wall pipe airtightness detection, in particular to LNG ship double-wall pipe airtightness detection equipment which comprises a shell. The two ends of the shell are each provided with a connector, each connector comprises a first connecting unit and a second connecting unit, each first connecting unit is used for being connected with the end of the inner pipe, each second connecting unit is used for being connected with the end of the outer pipe, and each second connecting unit comprises an outer connecting shell arranged on the periphery of the corresponding first connecting unit in a sleeving mode; a second annular gap exists between the outer connecting shell and the first connecting unit, a connecting pipe for connecting the two connectors is arranged between the two connectors, and the two ends of the connecting pipe are connected with the outer connecting shell in the two connectors respectively and communicate with the corresponding second annular gap in the two connectors; a first fan is arranged between the connecting pipe and the outer connecting shell, and a barometer is arranged on the outer connecting shell. According to the invention, the safety in the detection process is ensured.

Description

Technical Field

[0001] The invention relates to the field of double-wall pipe air tightness detection, and in particular to a double-wall pipe air tightness detection device for LNG ships. Background Art

[0002] The double-wall pipe is composed of an inner pipe and an outer pipe. Since the double-wall pipe is mostly used to transport LNG, the air tightness test of the double-wall pipe is particularly important. There is an annular gap between the inner pipe and the outer pipe. If the inner pipe leaks, the leaked LNG gas will leak into the annular gap. However, since the inner pipe is located inside the outer pipe, the leakage of the inner and outer pipes needs to be tested simultaneously during the test, which makes it difficult to detect leaks during the air tightness test.

[0003] Chinese patent publication number CN118275055A discloses an airtightness test tool for a 6G70ME-GI diesel engine double-walled gas pipe, wherein the gas system of the diesel engine comprises a gas supply component, a cylinder, a gas block and a purge control component connected by a double-walled gas pipe, wherein the gas block is mounted on the cylinder head of the cylinder and is provided with a process hole for processing, wherein the process hole is connected to an outer pipe of the double-walled gas pipe and is provided with a screw plug for isolating the process hole from the outside, wherein the outer pipe of the double-walled gas pipe is provided with a plurality of test plugs; the airtightness test tool is made of rubber and is used to be placed in the process hole to block the outer pipe channel of the double-walled gas pipe at the process hole.

[0004] The above-mentioned experimental tools are used to test the double-walled pipes after installation. Before installation, the manufacturers of double-walled pipes also need to conduct air tightness tests on the double-walled pipes before leaving the factory. The main purpose is to monitor whether the double-walled pipes themselves have defects. During the inspection, the inner pipe and the annular gap are pressurized respectively to determine whether there are air tightness problems in the inner and outer pipes. At the same time, since the manufacturer needs to sample and test a large number of double-walled pipes, and in order to ensure the accuracy of the test results, LNG gas needs to be introduced into the inner and outer pipes. LNG gas is flammable. If a leak occurs, it is easy to cause an explosion. In particular, when a leak occurs in the inner pipe, the leaked LNG gas will flow into the annular gap, so it is not easy to diffuse out of the annular gap. When the leakage accumulates too much, it is easy to cause an explosion. At the same time, since the first fan continuously circulates the air in the circulation pipeline, the leaked LNG gas is prevented from accumulating in the first annular gap, and the LNG concentration in the first annular gap is prevented from increasing. Summary of the invention

[0005] In view of the above problems, a double-wall pipe air tightness detection equipment for LNG ships is provided. A connector is arranged at both ends of the outer shell, and a connecting pipe is arranged between the two connectors to connect the two connectors, so that the first annular gap, the second annular gap and the connecting pipe form a circulation pipeline, and a barometer is arranged in the connector. When there is no leakage in the inner pipe, the pressure in the circulation pipeline does not change. If the LNG gas in the inner shell leaks, the barometer can monitor the pressure rise in the circulation pipeline. At the same time, since the first fan continuously circulates the air in the circulation pipeline, the leaked LNG gas is prevented from accumulating in the first annular gap.

[0006] In order to solve the problems of the prior art, the present invention provides a double-wall pipe air tightness detection equipment for LNG ships, comprising an outer shell, in which a double-wall pipe is placed, the double-wall pipe is composed of an outer pipe and an inner pipe, and a first annular gap exists between the outer pipe and the inner pipe; a connector is respectively arranged at both ends of the outer shell, the connector comprises a first connecting unit and a second connecting unit, the first connecting unit is used to connect with the end of the inner pipe, the second connecting unit is used to connect with the end of the outer pipe, the second connecting unit comprises an outer connecting shell sleeved on the periphery of the first connecting unit, a second annular gap exists between the outer connecting shell and the first connecting unit, a connecting pipe for connecting the two connecting heads is arranged between the two connecting heads, the two ends of the connecting pipe are respectively connected to the outer connecting shells in the two connecting heads, and are communicated with the corresponding second annular gaps in the two connecting heads, a first fan is arranged between the connecting pipe and the outer connecting shell, after the outer connecting shell is fixedly connected to the end of the outer pipe, the first annular gap, the second annular gap and the connecting pipe are communicated, and a circulation pipeline is formed, and a barometer is arranged on the outer connecting shell.

[0007] Preferably, a dilution unit is provided at the lower part of the connecting pipe, the dilution unit includes a dilution box provided below the connecting pipe, an air inlet pipe is vertically provided at one end of the connecting pipe, both ends of the air inlet pipe are respectively connected to the connecting pipe and the dilution box, an air outlet pipe is vertically provided at the other end of the connecting pipe, both ends of the air outlet pipe are respectively connected to the connecting pipe and the dilution box, and the connection between the air outlet pipe and the dilution box and the connection between the air inlet pipe and the dilution box are respectively located at both ends of the dilution box.

[0008] Preferably, a first switch valve is provided on the connecting pipe, a second switch valve is provided on the air inlet pipe, and a third switch valve is provided on the air outlet pipe. When no leakage occurs in the inner pipe, the first switch valve is opened, and the second and third switch valves are closed. When leakage occurs in the inner pipe, the first switch valve is closed, and the second and third switch valves are opened.

[0009] Preferably, a stirring unit is provided in the dilution box, and the stirring unit comprises a stirring frame rotatably arranged in the dilution box, and a plurality of stirring blades are evenly and fixedly arranged on the peripheral wall of the stirring frame.

[0010] Preferably, multiple stirring frames are provided, and a driving unit for driving the stirring frames to rotate is provided on the upper part of the stirring frames. The driving unit includes a synchronous wheel fixedly provided on the upper end of the stirring frames, and a synchronous belt for driving all the synchronous wheels to rotate synchronously is provided on the outside of all the synchronous wheels. A rotating driver for driving the synchronous wheel to rotate is provided on the upper end of one of the synchronous wheels.

[0011] Preferably, a second fan is provided in the middle of the dilution box, and the second fan is used to blow the air from the connection between the dilution box and the air inlet pipe to the connection between the dilution box and the air outlet pipe.

[0012] Preferably, a ventilation unit is provided on the dilution box, and the ventilation unit includes an air pump provided on the side wall of the dilution box, and a fourth switch valve is also provided on the side wall of the dilution box.

[0013] Preferably, the first connecting unit includes an inner connecting shell, a soft rubber sleeve is fixedly provided at the end of the inner connecting shell, the inner ring side wall cross-section of the soft rubber sleeve is a wedge-shaped structure, an extrusion sleeve is slidably provided inside the inner connecting shell along the extension direction of the inner connecting shell, the end portion of the extrusion sleeve is a wedge-shaped structure, an extrusion unit is provided at the end of the extrusion sleeve away from the soft rubber sleeve, and the extrusion sleeve extrude the soft rubber sleeve through the end of its own wedge-shaped structure.

[0014] Preferably, the extrusion unit includes an extrusion ring which is rotatably arranged in the inner connecting shell, a plurality of extrusion blocks are fixedly arranged on one end of the extrusion ring facing the extrusion sleeve, and the extrusion blocks are evenly arranged around the axis of the extrusion ring. A plurality of electromagnets are evenly arranged on one side of the extrusion ring around the axis of the inner connecting shell, and the electromagnets are energized in sequence. A plurality of magnetic suction blocks are evenly distributed on the end of the extrusion ring facing the electromagnet, and an extension rod is fixedly arranged on the end of the extrusion sleeve away from the soft rubber sleeve along the extension direction of the inner connecting sleeve.

[0015] Preferably, a plurality of support rods are arranged in the shell along the length direction of the shell, and the support rods are in a "V"-shaped structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. By setting a connector at both ends of the outer shell, and setting a connecting pipe between the two connectors to connect the two connectors, the first annular gap, the second annular gap and the connecting pipe form a circulation pipeline, and a barometer is set in the connector. When there is no leakage in the inner tube, the pressure in the circulation pipeline does not change. If the LNG gas in the inner shell leaks, the barometer can monitor the pressure rise in the circulation pipeline, so the supply unit stops supplying LNG. At the same time, because the first fan continuously circulates the air in the circulation pipeline, the leaked LNG gas is prevented from accumulating in the first annular gap, thereby preventing the LNG concentration in the first annular gap from increasing, thereby ensuring that in the subsequent disassembly of the double-walled pipe, the LNG gas concentration in the first annular gap will not reach the minimum combustion concentration, ensuring the safety of the detection process.

[0018] 2. A dilution unit is provided at the lower part of the connecting pipe, so that after the barometer detects LNG leakage, the first connecting pipe provided on the connecting pipe is closed, the connecting pipe is disconnected, the second switch valve and the third switch valve provided on the air inlet pipe and the air outlet pipe are opened at the same time, and the first annular gap, the second annular gap and the dilution tank form a new circulation pipeline. Since the volume of the dilution tank is larger than that of the connecting pipe, the dilution tank has a better dilution effect on the leaked LNG gas, thereby avoiding the situation that when the inner pipe has a serious leakage due to air tightness problems, the circulation pipeline formed by the first annular gap, the second annular gap and the connecting pipe cannot dilute the LNG gas in time.

[0019] 3. By arranging a stirring frame and a second fan, the stirring frame stirs the air in the dilution box through the stirring blades, and the air in the dilution box is blown more evenly through the second fan, thereby improving the dilution effect of the dilution box. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The invention is a three-dimensional schematic diagram of a double-walled pipe air tightness detection device for LNG ships, which is connected to a double-walled pipe.

[0021] Figure 2 The invention is a side view of a double-walled pipe air tightness detection device for LNG ships, which is connected to the double-walled pipe.

[0022] Figure 3 The present invention is a double-walled pipe air tightness detection device for LNG ships Figure 2 Schematic cross-sectional view at AA in the middle.

[0023] Figure 4 The invention discloses a double-wall pipe air tightness detection device for LNG ships, which is a cutaway stereoscopic schematic diagram of a double-wall pipe.

[0024] Figure 5 The present invention is a double-walled pipe air tightness detection device for LNG ships Figure 4 A local enlarged schematic diagram of point B in the middle.

[0025] Figure 6 The present invention is a double-walled pipe air tightness detection device for LNG ships Figure 4 A partial enlarged schematic diagram of point C in the middle.

[0026] Figure 7 The present invention is a double-walled pipe air tightness detection device for LNG ships Figure 4 A partial enlarged schematic diagram of point D in the middle.

[0027] Figure 8 It is a three-dimensional schematic diagram of a double-wall pipe air tightness detection device for LNG ships of the present invention, which is connected with a double-wall pipe and has its outer shell removed.

[0028] Fig. 9 It is a three-dimensional schematic diagram of a double-wall pipe air tightness detection device for LNG ships of the present invention, which is equipped with a double-wall pipe and has an outer shell and a dilution tank removed.

[0029] Fig.10 It is a three-dimensional schematic diagram of a double-wall pipe air tightness detection device for LNG ships of the present invention with the outer shell and the dilution tank removed.

[0030] Fig.11 It is a three-dimensional schematic diagram of an extrusion unit of a double-walled pipe air tightness detection device for LNG ships of the present invention.

[0031] The numbers in the figure are:

[0032] 1. Shell; 11. Supply unit; 12. Support rod; 2. Connector; 21. First connecting unit; 211. Inner connecting shell; 212. Soft rubber sleeve; 213. Extrusion sleeve; 214. Extrusion unit; 2141. Extrusion ring; 2142. Extrusion block; 2143. Electromagnet; 2144. Magnetic block; 215. Extension rod; 216. Fixing ring; 217. Spring; 22. Second connecting unit; 221. Outer connecting shell; 222. First fan; 3. Connecting pipe ; 4. Outer tube; 41. Inner tube; 5. Dilution unit; 51. Dilution box; 52. Air inlet pipe; 53. Air outlet pipe; 54. First switch valve; 55. Second switch valve; 56. Third switch valve; 57. Stirring unit; 571. Stirring frame; 572. Stirring blade; 573. Drive unit; 5731. Synchronous wheel; 5732. Synchronous belt; 5733. Rotary drive; 58. Second fan; 59. Ventilation unit; 591. Air pump; 592. Fourth switch valve. DETAILED DESCRIPTION

[0033] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] Reference Figure 1-Figure 6 : A double-walled pipe air tightness detection device for LNG ships, comprising a shell 1, in which a double-walled pipe is placed, the double-walled pipe is composed of an outer pipe 4 and an inner pipe 41, and a first annular gap exists between the outer pipe 4 and the inner pipe 41; a connector 2 is respectively arranged at both ends of the shell 1, the connector 2 comprises a first connecting unit 21 and a second connecting unit 22, the first connecting unit 21 is used to connect with the end of the inner pipe 41, the second connecting unit 22 is used to connect with the end of the outer pipe 4, the second connecting unit 22 comprises an outer connecting shell 221 which is sleeved on the periphery of the first connecting unit 21, and the outer connecting shell 221 is provided with a first connecting unit 21; the outer connecting shell 221 is provided with a first connecting unit 21; the outer connecting shell 221 is provided with a second connecting unit 2 ... There is a second annular gap between the shell 221 and the first connecting unit 21, and a connecting pipe 3 is arranged between the two connecting heads 2 to connect the two connecting heads 2. The two ends of the connecting pipe 3 are respectively connected to the outer connecting shells 221 in the two connecting heads 2, and are connected to the corresponding second annular gaps in the two connecting heads 2. A first fan 222 is arranged between the connecting pipe 3 and the outer connecting shell 221. After the outer connecting shell 221 is fixedly connected to the end of the outer pipe 4, the first annular gap, the second annular gap and the connecting pipe 3 are communicated to form a circulation pipeline, and a barometer is arranged on the outer connecting shell 221.

[0035] In the traditional double-walled pipe inspection process, the sealing performance of the inner pipe 41 and the outer pipe 4 needs to be inspected separately. First, the air tightness of the inner pipe 41 needs to be inspected, and then the air tightness of the outer pipe 4 can be inspected. This is because the existing inspection methods all judge the air tightness of the double-walled pipe by the change of air pressure. If the outer pipe 4 is inspected first, the high-pressure gas needs to be passed into the first annular gap first. If the inner pipe 41 itself has an air tightness problem, and the outer pipe 4 does not have an air tightness problem, the pressure in the first annular gap will still drop, so there will be a misjudgment of the air tightness of the outer pipe 4. The air tightness of the inner pipe 41 is inspected first, which ensures that it is not easy to make a misjudgment when the air tightness of the outer pipe 4 is inspected later. In order to ensure the accuracy of the inspection process, LNG gas will be introduced into the inner pipe 41 when the air tightness of the inner pipe 41 is inspected, so as to simulate the environment of the inner pipe 41 in the double-walled pipe during actual transportation. However, LNG gas is flammable. If there is a leak in the inner tube 41, the leaked LNG gas will be discharged into the first annular space, and the air in the first annular space is not circulated, resulting in an increase in the LNG concentration in the first annular space. After the test is completed, when the double-walled tube is removed from the test equipment, the LNG gas remaining in the first annular space will overflow, which is a high risk.

[0036] In order to avoid the above situation, the air tightness detection equipment is further optimized so that after the detection is completed, the concentration in the first annular space will not be too high and cannot reach the combustion concentration, thereby ensuring the safety of the staff. The specific structure and working steps are as follows:

[0037] When conducting the experiment, the double-walled tube is placed horizontally in the shell 1, and then the two connectors 2 are connected to the two ends of the double-walled tube respectively. When the connector 2 is connected to the double-walled tube, two steps of connection are required. First, the first connecting unit 21 needs to be connected to the inner tube 41, and then the end of the outer connecting tube 3 is connected to the end of the outer tube 4. At this time, the first annular gap and the second annular gap are connected to each other. When the air tightness of the inner tube 41 is tested, a supply unit 11 is provided on one side of the shell 1. The supply unit 11 injects LNG gas into the inner tube 41 through the first connecting unit 21 and maintains a certain pressure. The pressure needs to be preset according to the actual use situation, and no reference value is provided here. At the same time, the first fan 222 is started. Under the action of the first fan 222, the gap between the outer tube 4 and the inner tube 41 is extracted from the first annular gap, and the extracted air enters the second annular gap in one of the connectors 2, and then is discharged into the second annular gap in the other connector 2 through the connecting pipe 3, and finally flows back to the first annular gap. When there is a problem with the air tightness of the inner tube 41, the LNG gas in the inner tube 41 will leak into the first annular space. Since the air in the first annular space is in a state of continuous flow, the LNG gas accumulated in the first annular space will be extracted.

[0038] During the test, the air pressure in the inner tube 41 is higher than that in the first annular gap. When the inner tube 41 leaks, the LNG gas in the inner tube 41 is discharged into the first annular gap, which will inevitably cause the air pressure in the first annular gap to rise, which can be monitored by the barometer. When the barometer detects a pressure increase, the supply unit 11 stops supplying LNG gas and starts to relieve pressure, and the pressure in the inner tube 41 gradually decreases, thereby reducing the leakage of the inner tube 41. The LNG gas leaked into the first annular gap is diluted by the air flowing in the first annular gap, thereby avoiding the accumulation of LNG gas, thereby ensuring that in the subsequent disassembly of the double-walled pipe, the LNG gas concentration in the first annular gap will not reach the minimum combustion concentration, thereby ensuring safety during the detection process.

[0039] Reference Figure 2 , Figure 3 , Figure 6 and Figure 7A dilution unit 5 is arranged at the lower part of the connecting pipe 3, and the dilution unit 5 includes a dilution box 51 arranged below the connecting pipe 3. An air inlet pipe 52 is vertically arranged at one end of the connecting pipe 3, and both ends of the air inlet pipe 52 are respectively connected to the connecting pipe 3 and the dilution box 51. An air outlet pipe 53 is vertically arranged at the other end of the connecting pipe 3, and both ends of the air outlet pipe 53 are respectively connected to the connecting pipe 3 and the dilution box 51. The connection between the air outlet pipe 53 and the dilution box 51 and the connection between the air inlet pipe 52 and the dilution box 51 are respectively located at the two ends of the dilution box 51.

[0040] Reference Figure 4 , Figure 6 and Figure 7 : A first switch valve 54 is provided on the connecting pipe 3, a second switch valve 55 is provided on the air inlet pipe 52, and a third switch valve 56 is provided on the air outlet pipe 53. When there is no leakage in the inner tube 41, the first switch valve 54 is opened, and the second switch valve 55 and the third switch valve 56 are closed. When there is leakage in the inner tube 41, the first switch valve 54 is closed, and the second switch valve 55 and the third switch valve 56 are opened.

[0041] Since the air storage in the connecting pipe 3 is limited, the total amount of air in the circulation pipeline is small when the first blower 222 is running. If the leakage of the inner pipe 41 is serious, the LNG concentration in the circulation pipeline will rise rapidly. In order to prevent the LNG concentration from reaching the explosion concentration, a dilution tank 51 is set at the lower part of the connecting pipe 3. When the barometer detects that the pressure in the circulation pipeline has risen, it means that the inner tube 41 has a leak. A controller is provided on the outer shell 1. The pressure monitored by the barometer is preset with a rated pressure threshold, that is, when the first fan 222 circulates the air in the circulation pipeline, a certain air pressure fluctuation will occur. In this way, the rated pressure threshold is preset for the barometer to avoid misjudgment of the barometer. When LNG gas leaks into the first annular gap of the column, the air pressure in the circulation pipeline rises and exceeds the maximum value of the rated pressure threshold. At this time, the barometer controls the first switch valve 54 to close through the controller, disconnects the connecting pipe 3, and opens the second switch valve 55 and the third switch valve 56. The first annular gap, the second annular gap and the dilution tank 51 form a new circulation pipeline. Since the volume of the dilution tank 51 is much larger than the volume in the connecting pipe 3, the air stock in the dilution tank 51 is larger and the dilution effect is better.

[0042] Reference Figure 3 and Fig. 9 A stirring unit 57 is provided in the dilution box 51 . The stirring unit 57 includes a stirring frame 571 rotatably provided in the dilution box 51 . A plurality of stirring blades 572 are evenly and fixedly provided on the peripheral wall of the stirring frame 571 .

[0043] Reference Figure 8-Figure 10: There are multiple stirring frames 571, and a driving unit 573 for driving the stirring frames 571 to rotate is arranged on the upper part of the stirring frames 571. The driving unit 573 includes a synchronous wheel 5731 fixedly arranged on the upper end of the stirring frame 571, and a synchronous belt 5732 for driving all the synchronous wheels 5731 to rotate synchronously is sleeved on the outside of all the synchronous wheels 5731, and a rotating driver 5733 for driving the synchronous wheel 5731 to rotate is arranged on the upper end of one of the synchronous wheels 5731.

[0044] The rotary driver 5733 is preferably a servo motor. When the rotary driver 5733 is started, the rotary driver 5733 drives one of the synchronous wheels 5731 to rotate. Under the action of the synchronous belt 5732, all the synchronous wheels 5731 rotate, so that all the stirring racks 571 arranged in the dilution tank 51 can rotate. The stirring rack 571 stirs the air in the dilution tank 51 through the stirring blades 572, so that the LNG gas discharged into the dilution tank 51 can be quickly diluted.

[0045] Reference Figure 3 and Figure 4 A second fan 58 is provided in the middle of the dilution box 51 , and is used to blow air from the connection between the dilution box 51 and the air inlet pipe 52 to the connection between the dilution box 51 and the air outlet pipe 53 .

[0046] Since the dilution tank 51 is relatively long, the LNG gas entering the dilution tank 51 through the air inlet pipe 52 will gather on one side of the dilution tank 51. Although there is a stirring effect of the stirring frame 571, the dilution effect of the dilution tank 51 cannot be maximized. After the second fan 58 is set in the middle position of the dilution tank 51, the air at the connection between the dilution tank 51 and the air inlet pipe 52 is discharged to the connection between the dilution tank 51 and the air outlet pipe 53 through the action of the second fan 58, and the LNG gas is diluted by the overall volume of the dilution tank 51, thereby improving the dilution effect.

[0047] Reference Figure 3 , Figure 4 and Figure 8 A ventilation unit 59 is provided on the dilution box 51 . The ventilation unit 59 includes an air pump 591 provided on the side wall of the dilution box 51 . A fourth switch valve 592 is also provided on the side wall of the dilution box 51 .

[0048] After the double-wall pipe test is completed, if there is a leak in the inner tube 41 of the double-wall pipe, the fourth switch valve 592 is opened, and then the air pump 591 is started. The air pump 591 extracts the mixed gas diluted with LNG gas in the dilution tank 51, and the outside air re-enters the dilution tank 51 through the fourth switch valve 592.

[0049] Reference Figure 4 and Figure 5The first connecting unit 21 includes an inner connecting shell 211, a soft rubber sleeve 212 is fixedly provided at the end of the inner connecting shell 211, the inner ring side wall cross-section of the soft rubber sleeve 212 is a wedge-shaped structure, and an extrusion sleeve 213 is slidably provided inside the inner connecting shell 211 along the extension direction of the inner connecting shell 211, the end of the extrusion sleeve 213 is a wedge-shaped structure, and an extrusion unit 214 is provided at the end of the extrusion sleeve 213 away from the soft rubber sleeve 212, and the extrusion sleeve 213 extrude the soft rubber sleeve 212 through the end of its own wedge-shaped structure.

[0050] Reference Figure 5 and Fig.11 The extrusion unit 214 includes an extrusion ring 2141 which is rotatably arranged in the inner connecting shell 211, and a plurality of extrusion blocks 2142 are fixedly arranged at one end of the extrusion ring 2141 facing the extrusion sleeve 213. The extrusion blocks 2142 are evenly arranged around the axis of the extrusion ring 2141, and a plurality of electromagnets 2143 are evenly arranged around the axis of the inner connecting shell 211 on one side of the extrusion ring 2141. The electromagnets 2143 are energized in sequence, and a plurality of magnetic blocks 2144 are evenly distributed on one end of the extrusion ring 2141 facing the electromagnets 2143. An extension rod 215 is fixedly arranged at one end of the extrusion sleeve 213 away from the soft rubber sleeve 212 along the extension direction of the inner connecting sleeve.

[0051] A fixing ring 216 is fixedly provided on the inner wall of the inner connecting shell 211, and the axis of the fixing ring 216 is colinear with the axis of the inner connecting shell 211. The extension rod 215 passes through the fixing ring 216 and slidably cooperates with the fixing ring 216. There is a gap between the extrusion sleeve 213 and the fixing ring 216. A spring 217 is provided in the gap along the extension direction of the extension rod 215. The two ends of the spring 217 are fixedly connected to the fixing ring 216 and the extrusion sleeve 213 respectively. A plurality of rolling balls are rotatably provided on the wedge-shaped structure of the extrusion sleeve 213. In this way, when the extrusion sleeve 213 extrudes the soft rubber sleeve 212, the friction between the extrusion sleeve 213 and the soft rubber sleeve 212 will not be too large, thereby ensuring the smooth extrusion of the soft rubber sleeve 212 by the extrusion sleeve 213.

[0052] During installation, the soft rubber sleeve 212 is inserted into the interior of the inner tube 41, and then the electromagnet 2143 is energized in turn. The electromagnet 2143 attracts the magnetic block 2144 set on the extrusion ring 2141, so that the extrusion ring 2141 rotates, and the extrusion ring 2141 drives the extrusion block 2142 to rotate synchronously. When the extrusion block 2142 rotates, it squeezes the end of the extension rod 215, so that the spring 217 is gradually stretched. Under the action of the extrusion block 2142, the extrusion sleeve 213 gradually squeezes the soft rubber sleeve 212, so that the soft rubber sleeve 212 is tightly fitted to the inner wall of the inner tube 41, ensuring the sealing of the end connection of the inner tube 41.

[0053] When the double-walled tube needs to be removed, the extrusion ring 2141 rotates in the opposite direction, the spring 217 drives the extrusion sleeve 213 to retract, and the extrusion sleeve 213 is separated from the soft rubber sleeve 212, so that the double-walled tube can be removed.

[0054] Reference Fig.10 : A plurality of support rods 12 are arranged in the shell 1 along the length direction of the shell 1, and the support rods 12 are of a "V"-shaped structure.

[0055] When the double-walled tube is placed on the support rod 12 , the “V”-shaped structure of the support rod 12 can prevent the double-walled tube from rolling along the width direction of the housing 1 .

[0056] Working principle: When conducting the experiment, the double-walled tube is placed horizontally in the shell 1, and then the two connectors 2 are connected to the two ends of the double-walled tube respectively. When the connector 2 is connected to the double-walled tube, two steps are required. First, the first connecting unit 21 needs to be connected to the inner tube 41, and then the end of the outer connecting pipe 3 is connected to the end of the outer tube 4. At this time, the first annular gap and the second annular gap are connected to each other. When the air tightness of the inner tube 41 is tested, a supply unit 11 is provided on one side of the shell 1. The supply unit 11 injects LNG gas into the inner tube 41 through the first connecting unit 21 and maintains a certain pressure. At the same time, the first fan 222 is started. Under the action of the first fan 222, the gap between the outer tube 4 and the inner tube 41 is extracted from the first annular gap, and the extracted air enters the second annular gap in one of the connectors 2, and then is discharged into the second annular gap in the other connector 2 through the connecting pipe 3, and finally flows back to the first annular gap. When there is a problem with the air tightness of the inner tube 41, the LNG gas in the inner tube 41 will leak into the first annular gap. Since the air in the first annular gap is in a state of continuous flow, the LNG gas accumulated in the first annular gap will be extracted, and the pressure in the circulation pipeline formed by the first annular gap, the second annular gap and the connecting pipe 3 will be constant.

[0057] When the inner tube 41 leaks, the LNG gas in the inner tube 41 is discharged into the first annular gap, which will inevitably cause the air pressure in the first annular gap to rise, which can be monitored by the barometer. When the barometer detects the pressure rise, the supply unit 11 stops supplying LNG gas and starts to relieve pressure, and the pressure in the inner tube 41 gradually decreases, thereby reducing the leakage of the inner tube 41. The LNG gas leaked into the first annular gap is diluted by the air flowing in the first annular gap, thereby avoiding the accumulation of LNG gas, thereby ensuring that in the subsequent disassembly of the double-walled pipe, the LNG gas concentration in the first annular gap will not reach the minimum combustion concentration, thereby ensuring the safety of the detection process.

[0058] The above embodiments only express one or several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the protection scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A double-walled pipe air tightness detection device for LNG ships, comprising a housing (1), wherein the housing (1) is used to place a double-walled pipe, the double-walled pipe comprising an outer pipe (4) and an inner pipe (41), and a first annular gap exists between the outer pipe (4) and the inner pipe (41); It is characterized in that A connecting head (2) is provided at each end of the outer shell (1), the connecting head (2) comprising a first connecting unit (21) and a second connecting unit (22), the first connecting unit (21) being used to connect to the end of the inner tube (41), the second connecting unit (22) being used to connect to the end of the outer tube (4), the second connecting unit (22) comprising an outer connecting shell (221) sleeved on the outer periphery of the first connecting unit (21), a second annular gap being provided between the outer connecting shell (221) and the first connecting unit (21), and a second connecting shell (221) being provided between the two connecting heads (2). A connecting pipe (3) is provided for connecting the two connecting heads (2); both ends of the connecting pipe (3) are respectively connected to the outer connecting shells (221) in the two connecting heads (2), and are communicated with the corresponding second annular gaps in the two connecting heads (2); a first fan (222) is provided between the connecting pipe (3) and the outer connecting shell (221); after the outer connecting shell (221) is fixedly connected to the end of the outer tube (4), the first annular gap, the second annular gap and the connecting pipe (3) are communicated to form a circulation pipeline; a barometer is provided on the outer connecting shell (221).

2. The double-walled pipe air tightness detection equipment for LNG ships according to claim 1 is characterized in that: A dilution unit (5) is arranged at the lower part of the connecting pipe (3), and the dilution unit (5) comprises a dilution box (51) arranged below the connecting pipe (3); an air inlet pipe (52) is vertically arranged at one end of the connecting pipe (3), and the two ends of the air inlet pipe (52) are respectively connected to the connecting pipe (3) and the dilution box (51); an air outlet pipe (53) is vertically arranged at the other end of the connecting pipe (3), and the two ends of the air outlet pipe (53) are respectively connected to the connecting pipe (3) and the dilution box (51); the connection between the air outlet pipe (53) and the dilution box (51) and the connection between the air inlet pipe (52) and the dilution box (51) are respectively located at the two ends of the dilution box (51).

3. The double-walled pipe air tightness detection equipment for LNG ships according to claim 2 is characterized in that: A first switch valve (54) is arranged on the connecting pipe (3), a second switch valve (55) is arranged on the air inlet pipe (52), and a third switch valve (56) is arranged on the air outlet pipe (53). When the inner pipe (41) does not leak, the first switch valve (54) is opened, and the second switch valve (55) and the third switch valve (56) are closed. When the inner pipe (41) leaks, the first switch valve (54) is closed, and the second switch valve (55) and the third switch valve (56) are opened.

4. The double-walled pipe air tightness detection equipment for LNG ships according to claim 2, characterized in that: A stirring unit (57) is arranged in the dilution box (51), and the stirring unit (57) comprises a stirring frame (571) rotatably arranged in the dilution box (51), and a plurality of stirring blades (572) are evenly and fixedly arranged on the peripheral wall of the stirring frame (571).

5. The double-walled pipe air tightness detection equipment for LNG ships according to claim 4, characterized in that: A plurality of stirring racks (571) are provided, and a driving unit (573) for driving the stirring rack (571) to rotate is provided on the upper part of the stirring rack (571). The driving unit (573) comprises a synchronous wheel (5731) fixedly provided on the upper end of the stirring rack (571), a synchronous belt (5732) for driving all the synchronous wheels (5731) to rotate synchronously is sleeved on the outside of all the synchronous wheels (5731), and a rotation driver (5733) for driving the synchronous wheel (5731) to rotate is provided on the upper end of one of the synchronous wheels (5731).

6. The double-walled pipe air tightness detection equipment for LNG ships according to claim 2, characterized in that: A second fan (58) is arranged at the middle position of the dilution box (51), and the second fan (58) is used to blow air from the connection between the dilution box (51) and the air inlet pipe (52) to the connection between the dilution box (51) and the air outlet pipe (53).

7. The double-walled pipe air tightness detection equipment for LNG ships according to claim 2, characterized in that: A ventilation unit (59) is provided on the dilution box (51), and the ventilation unit (59) comprises an air pump (591) provided on the side wall of the dilution box (51). A fourth switch valve (592) is also provided on the side wall of the dilution box (51).

8. The double-walled pipe air tightness detection equipment for LNG ships according to claim 1, characterized in that: The first connection unit (21) comprises an inner connection shell (211), a soft rubber sleeve (212) is fixedly arranged at the end of the inner connection shell (211), the inner ring side wall cross-section of the soft rubber sleeve (212) is a wedge-shaped structure, an extrusion sleeve (213) is slidably arranged inside the inner connection shell (211) along the extension direction of the inner connection shell (211), the end of the extrusion sleeve (213) is a wedge-shaped structure, and an extrusion unit (214) is arranged at one end of the extrusion sleeve (213) away from the soft rubber sleeve (212), and the extrusion sleeve (213) extrudes the soft rubber sleeve (212) through the end of its own wedge-shaped structure.

9. The double-walled pipe air tightness detection equipment for LNG ships according to claim 8, characterized in that: The extrusion unit (214) comprises an extrusion ring (2141) which is rotatably arranged in the inner connecting shell (211) around the axis of the inner connecting shell (211); a plurality of extrusion blocks (2142) are fixedly arranged on one end of the extrusion ring (2141) facing the extrusion sleeve (213); the extrusion blocks (2142) are evenly arranged around the axis of the extrusion ring (2141); a plurality of electromagnets (2143) are evenly arranged on one side of the extrusion ring (2141) around the axis of the inner connecting shell (211); the electromagnets (2143) are energized in sequence; a plurality of magnetic blocks (2144) are evenly distributed on one end of the extrusion ring (2141) facing the electromagnets (2143); and an extension rod (215) is fixedly arranged on one end of the extrusion sleeve (213) away from the soft rubber sleeve (212) along the extension direction of the inner connecting sleeve.

10. The double-walled pipe air tightness detection equipment for LNG ships according to claim 1, characterized in that: A plurality of support rods (12) are arranged in the outer shell (1) along the length direction of the outer shell (1), and the support rods (12) are of a "V"-shaped structure.

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