Low flash point fuel double wall tubing device and method of assembly

Abstract

The application relates to the technical field of low-flash-point fuel double-wall pipe devices, and discloses a low-flash-point fuel double-wall pipe device and an assembling method thereof, which form a set of high-efficiency welding, folding and mounting processes for the inner pipe and the outer pipe of the double-wall pipe, ensure that the welding requirements are fully met, the mechanical performance of the welding seam is improved, the forming quality of the welding seam is improved, and the one-time inspection qualified rate is high.

Description

Technical Field

[0001] This invention relates to the technical field of low flash point fuel double-wall tube devices, specifically to a low flash point fuel double-wall tube device and its assembly method. Background Technology

[0002] With the increasing frequency of extreme weather events, global requirements for carbon emission reduction are becoming increasingly stringent, making the use of low-carbon and clean fuels on ships a major industry trend. LPG, LEG, and ammonia fuels are gradually becoming recognized alternative fuel choices. However, due to their low temperature, low flash point, and flammability and explosiveness, the requirements for their use on ships are far higher than for conventional fuels. For example, LPG fuel has a lower explosive limit of 1.5% and is heavier than air, making it prone to accumulation and explosion after leakage. Similarly, with ammonia fuel, a leak can cause discomfort to humans at a concentration of 100 ppm, and pose a health hazard at 250 ppm. To reduce accidents caused by pipeline leaks, ship fuel pipelines are generally made of austenitic stainless steel, primarily using butt welding for connection. The welding quality must be sufficiently high, requiring a 99% first-pass yield rate when using RT (Real-Time) non-destructive testing. The argon flow rate and its concentration at the weld are key indicators affecting the weld pass rate.

[0003] Depending on the engine's needs, fuel originates from the fuel tank, is heated and pressurized by the fuel supply unit, and then supplied to the engine in liquid form for combustion. Excess fuel returns to the fuel tank via the return pipe. To enhance safety, current technology designates the engine compartment as a safe area, and uses double-walled pipes for the fuel lines, consisting of an inner and outer pipe. Fuel is transported through the inner pipe; in the event of a leak in the inner pipe, the leak can be contained between the inner and outer pipes for secondary protection, preventing it from entering the engine compartment and causing a fire or explosion. However, in current practical applications of double-walled pipe arrangements, the following problems and disadvantages are commonly observed:

[0004] 1. The welding and joining process of the inner and outer pipes of the double-walled pipe is complex, inefficient, and inconvenient to install.

[0005] 2. When welding the double-walled pipes together, the inner and outer pipes require separate temporary argon-filling fixtures. These temporary fixtures are temporarily sealed with cardboard, which is prone to leakage, makes it difficult to control the flow rate, and results in insufficient argon filling. The concentration is often not up to standard due to the lack of a monitoring device, which leads to poor weld quality and a low first-time inspection pass rate.

[0006] 3. Argon purging is difficult for the final weld, resulting in extremely poor weld quality, a very low pass rate, and a high risk of leakage.

[0007] 4. Inadequate support between the inner and outer pipes of the double-walled pipe fails to mitigate the uneven stress caused by thermal expansion during fuel transport and the vibration from the engine, making the double-walled pipe prone to damage and leakage, thus posing a safety risk. Summary of the Invention

[0008] One of the objectives of this invention is to propose an assembly method for a low flash point fuel double-walled tube device, forming a set of highly efficient welding, joining and installation processes that take into account both the inner and outer tubes of the double-walled tube, ensuring that welding requirements are fully met, thereby improving the mechanical properties of the weld and the forming quality of the weld, and achieving a high first-time inspection pass rate.

[0009] The technical solution of the present invention is as follows:

[0010] A method for assembling a low flash point fuel double-walled tube device includes the following steps:

[0011] S1000: The outer pipe is pre-cut into two half-pipe segments, and the outer pipe is welded together after the inner pipe is constructed.

[0012] Step S1000 includes:

[0013] S1110: Sequentially, according to the direction of fuel transportation in the inner pipe, the closing positions of the double-walled pipes are set as the first weld position, the nth weld position, and the last weld position, where n is a positive integer;

[0014] S1120: The supply pipe is inserted into the outer pipe through the pipe cap to form the beginning end of the double-walled pipe. Its first closing joint is the first welding position. The return pipe passes through the outer pipe through the pipe cap. This is the end of the double-walled pipe. The last closing joint before the end is the last welding position. The several welding positions in the middle are the nth welding position.

[0015] S1130: The double-walled pipes are joined sequentially at the first weld position, the nth weld position, and the last weld position.

[0016] Furthermore, the welding closure method in step S1120 includes:

[0017] S1121: The first gas source and / or the second gas source provide nitrogen-argon mixture gas through the first argon filling pipe connected to the inlet of the first valve group, and continuously inject it into the inner pipe to meet the flow rate required for argon arc welding;

[0018] S1122: Weld the inner tube and perform non-destructive testing on the inner tube weld to ensure that the weld meets the requirements;

[0019] S1123: The second gas source provides argon gas, which is connected to the test tube through the second argon filling tube, and is then filled into the annular space of the double-walled tube through the test tube;

[0020] S1124: Weld the half-segments on the outer pipe weld together and perform non-destructive testing on the outer pipe weld to ensure that the weld meets the requirements.

[0021] Furthermore, the welding closure method for the final weld position in step S1120 includes the following steps:

[0022] S1125: The first gas source and / or the second gas source provide nitrogen-argon mixture gas through the first argon filling pipe connected to the inlet of the first valve group, continuously injecting it into the inner pipe to meet the flow rate required for argon arc welding, and finally discharging it through the vent of the second valve group.

[0023] S1126: Perform welds on the inner tube and conduct non-destructive testing on the welds to ensure they meet the requirements;

[0024] S1127: The first and second gas sources provide nitrogen-argon mixture through the air inlet pipe, which is then filled into the annular space of the double-walled pipe. The fan is started to form negative pressure ventilation. Part of the mixture overflows from the overflow pipe to ensure that no air is mixed into the mixture entering the double-walled pipe. By ensuring the composition of the nitrogen-argon mixture, the quality of the weld is ensured.

[0025] S1128: Weld the half-segments on the outer pipe weld together and perform non-destructive testing on the outer pipe weld to ensure that the weld meets the requirements.

[0026] Furthermore, the construction method for the inner pipe in step S1000 is as follows:

[0027] S1210: Two semi-circular parts symmetrically surround and hug the inner tube, and are fastened to the inner tube by fastening parts, and are combined into one piece;

[0028] S1220: Use clamps as installation tools to wrap around all the curved elastic parts, and tighten the clamps with bolts to compress the curved elastic parts.

[0029] S1230: After tightening, make its outer diameter smaller than the inner diameter of the outer tube, then push it into the outer tube, and stop before the edge of the outer tube touches the edge of the clamp;

[0030] S1240: Loosen the clamps and continue pushing the inner tube with the installed flexible support into the outer tube to reach the designated position.

[0031] Furthermore, after installing the flexible support components, install the rigid support components, following these steps:

[0032] S1310: Insert a support ring onto the inner tube;

[0033] S1320: Two half-tube segments are opened on the outer tube at the location of the rigid support member, and several runway holes are opened on the half-tube segments;

[0034] S1330: Weld rigid support components onto the inner tube;

[0035] S1340: Insert the support plate into the runway hole for welding;

[0036] S1350: Two half-tube segments are joined together and welded to form a tube;

[0037] S1360: The tube formed in S1350 is joined together with the outer tube in a ring shape, and then welded.

[0038] S1370: Perform non-destructive testing on the welds on the outer pipe to ensure that the welds meet the requirements.

[0039] Another objective of this invention is to provide a low flash point fuel double-walled tube device, comprising a double-walled tube, a half-tube segment, a first gas source, a second gas source, an overflow pipe, a blower, an air inlet pipe, an air outlet pipe, a pressure test pipe, a first valve group, a second valve group, and a pipe cap, wherein the pipe cap is located at one end of the outer tube, and the pressure test pipe is connected to the air outlet pipe;

[0040] The double-walled pipe includes a first control valve, a second control valve, a first argon filling pipe, a second argon filling pipe, a first welding position, an nth welding position, an outer pipe, and an inner pipe welded inside the outer pipe. The two ends of the exhaust pipe are respectively connected to the first control valve and the outer pipe. The inner pipe includes a supply pipe for conveying fuel to the main unit and a return pipe for returning surplus fuel. The first valve group is installed on the supply pipe, and the second valve group is installed on the return pipe.

[0041] The first and second air sources are installed side by side in the air inlet pipe of the double-walled pipe, and the overflow pipe is set on the air inlet pipe. The air is drawn out by the fan, and the gas from the first and / or second air sources flows in the annular space of the double-walled pipe under negative pressure.

[0042] Furthermore, a number of flexible support members and a number of rigid support members are provided between the inner tube and the outer tube;

[0043] Some of the flexible support components are located at the front and rear ends of the inner pipe elbow;

[0044] Rigid supports and some flexible supports are located in the straight section of the inner tube and are arranged at intervals.

[0045] Furthermore, there are at least three flexible support members, with one at the front end of the elbow and two at the rear end of the elbow. The two flexible support members at the rear end of the elbow are installed at angles that are 90° off from each other around the inner tube.

[0046] Furthermore, the flexible support includes two semi-circular portions and two fastening portions, with the two ends of the semi-circular portions extending to form arc-shaped elastic portions;

[0047] Two arc-shaped elastic parts are symmetrically distributed, and their arc-shaped parts are in contact with the inner wall of the outer tube;

[0048] The curved elastic part is equipped with an anti-static and low-temperature resistant insulating sheet.

[0049] Furthermore, the rigid support includes a support plate and a support ring component. The outer tube has two half-tube segments at the location of the rigid support. Several runway holes are opened on the half-tube segments. The number of support plates is the same as the number of runway holes and they are welded together.

[0050] The support ring is a circular tube, sleeved on the inner tube and welded. One end of the support plate is welded to the support ring, and the other end of the support plate is welded to the runway hole. The support plates are arranged in a ring array between the inner tube and the outer tube.

[0051] The working principle and beneficial effects of this invention are as follows:

[0052] 1. Develop a set of highly efficient welding, joining, and installation processes that take into account both the inner and outer pipes of the double-walled pipe.

[0053] 2. When welding the double-walled pipes together, the inner and outer pipes use a fixed nitrogen-argon mixed gas source and are configured in proportion. The flow rate is easy to control. The nitrogen-argon gas ratio and concentration are detected by a monitoring device to ensure that the welding requirements are fully met, thereby improving the mechanical properties of the weld and the forming quality of the weld. The first-time inspection pass rate is high.

[0054] 3. Argon purging of the final weld is more reasonable and convenient, resulting in better weld quality.

[0055] 4. The inner and outer pipes are rationally arranged by combining flexible and rigid support components, which can eliminate the uneven stress caused by thermal expansion and the vibration from the engine, reduce the risk of double-wall pipe rupture and leakage, and improve safety.

[0056] 5. Flexible supports are used to accommodate low-friction sliding and vibration caused by the thermal expansion of the inner tube relative to the outer tube. They are easy to assemble and are used to create radial flexibility in the annular space designated as a hazardous area to accommodate the thermal expansion of the inner tube relative to the outer tube at bends. When subjected to engine compartment vibrations, they maintain radial flexibility in contact, preventing damage to the outer tube and thus minimizing the source of leakage in the outer tube and preventing excessive pipe vibration levels. Attached Figure Description

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0058] Figure 1 This is a schematic diagram of the structure of the present invention;

[0059] Figure 2 The cash register features a double-walled tube structure.

[0060] Figure 3 This is a schematic diagram of a rigid support structure.

[0061] Figure 4 This is a schematic diagram of the assembly of rigid and flexible support components;

[0062] Figure 5 This is a sectional view of a rigid support member;

[0063] Figure 6 Schematic diagram of pre-assembly of flexible support component;

[0064] Figure 7 This is a schematic diagram of the installation of a flexible support that is rotated and offset by 90°.

[0065] In the diagram: 100, Engine; 101, Double-walled pipe; 1011, Inner pipe; 1012, Outer pipe; 1013, Semi-segment; 1014, Runway opening; 102, First air source; 103, Second air source; 104, Supply pipe; 105, Return pipe; 106, Overflow pipe; 107, Fan; 1071, Inlet pipe; 1072, Exhaust pipe; 108, Pressure testing pipe; 1091, First argon filling pipe; 1092, Second argon filling pipe; 110, First valve assembly; 111, Second valve assembly; 112, First control valve; 113. Second control valve; 120, flexible support; 1201, arc-shaped elastic part; 1202, semi-circular part; 1203, fastening part; 1205, clamp; 121, rigid support; 1211, support plate; 1212, support ring; 130, first weld position; 131, nth weld position; 132, last weld position; L, support spacing; 201, differential pressure sensor; 202, flow meter; 203, gas detector; 210, non-destructive testing; 3, installation location; 4, weld seam; 5, 90° offset installation; 6, fuel flow direction. Detailed Implementation

[0066] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0067] Example 1

[0068] like Figure 1-7 As shown, an assembly method for a low flash point fuel double-walled tube 101 device includes the following steps:

[0069] S1000: The outer pipe 1012 is pre-cut into two half-pipe segments 1013, and the outer pipe 1012 is welded together after the inner pipe 1011 is completed.

[0070] The overall assembly method of the double-walled tube 101 device in step S1000 includes:

[0071] S1110: In the direction of fuel transportation in the inner pipe 1011, the closing positions of the double-walled pipe 101 are set as the first welding position 130, the nth welding position 131, and the last welding position 132, where n is a positive integer;

[0072] S1120: The supply pipe 104 (or gas supply pipe) is inserted into the outer pipe 1012 through the pipe cap to form the beginning end of the double-walled pipe 101. Its first closure is the first weld position 130. The return pipe 105 passes through the outer pipe 1012 through the pipe cap. This is the end of the double-walled pipe 101. The last closure before the end is the last weld position 132. The several weld positions in the middle are the nth weld position 131.

[0073] S1130: The double-walled tube 101 is joined together in sequence according to the first welding position 130, the nth welding position 131 and the last welding position 132.

[0074] During welding, welding work is carried out only after the gas detector 203 detects that the concentration of the nitrogen-argon mixture meets the requirements; at the same time, welding work at the final welding position 132 is carried out only when the differential pressure detector detects negative pressure.

[0075] The welding and joining method in step S1120 includes:

[0076] S1121: The first gas source 102 and / or the second gas source 103 provide nitrogen-argon mixture gas, which is connected to the inlet of the first valve group 110 through the first argon filling pipe 1091 and continuously injected into the inner pipe 1011 to meet the flow rate required for argon arc welding.

[0077] S1122: Weld seam 4 of inner tube 1011 and perform non-destructive testing on weld seam 4 of inner tube 1011 to ensure that weld seam 4 meets the requirements;

[0078] S1123: The second gas source 103 provides argon gas, which is connected to the test tube 108 through the second argon filling tube 1092, and is filled into the annular space of the double-walled tube 101 through the test tube 108.

[0079] S1124: Weld the half-pipe segments 1013 on the weld seam 4 of the outer pipe 1012 together, and perform non-destructive testing on the weld seam 4 of the outer pipe 1012 to ensure that the weld seam 4 meets the requirements.

[0080] The welding closure method for the final weld position 132 in step S1120 includes the following steps:

[0081] S1125: The first gas source 102 and / or the second gas source 103 provide nitrogen-argon mixture gas, which is connected to the inlet of the first valve group 110 through the first argon filling pipe 1091 and continuously injected into the inner pipe 1011 to meet the flow rate required for argon arc welding. Finally, it is discharged through the vent of the second valve group 111.

[0082] S1126: Perform weld 4 on the inner tube 1011 and conduct non-destructive testing on weld 4 of the inner tube 1011 to ensure that weld 4 meets the requirements;

[0083] S1127: The first gas source 102 and the second gas source 103 provide nitrogen-argon mixture through the air inlet pipe 1071 and fill the annular space of the double-walled pipe 101. The fan 107 is started to form negative pressure ventilation. Part of the mixture overflows from the overflow pipe 106 to ensure that no air is mixed into the mixture entering the double-walled pipe 101. By ensuring the composition of the nitrogen-argon mixture, the quality of weld 4 is ensured.

[0084] S1128: Weld the half-pipe segments 1013 on the weld seam 4 of the outer pipe 1012 together, and perform non-destructive testing on the weld seam 4 of the outer pipe 1012 to ensure that the weld seam 4 meets the requirements.

[0085] The construction method for the inner pipe 1011 in step S1000 is as follows:

[0086] S1210: Two semicircular parts 1202 are symmetrically wrapped around the inner tube 1011 and fastened to the inner tube 1011 by fastening parts 1203, thus forming a whole;

[0087] S1220: Using clamp 1205 as an installation tool, wrap around all the arc-shaped elastic parts 1201, and tighten clamp 1205 with bolts to compress the arc-shaped elastic parts 1201.

[0088] S1230: After tightening, make its outer diameter smaller than the inner diameter of the outer tube 1012, then push it into the outer tube 1012, and stop before the edge of the outer tube 1012 touches the edge of the clamp 1205.

[0089] S1240: Loosen the clamp 1205 and push the inner tube 1011, with the flexible support 120 installed, into the outer tube 1012 to reach the designated position.

[0090] After installing the flexible support 120, install the rigid support 121 as follows:

[0091] S1310: First install all the flexible support members 120 on the inner tube 1011 and fit the support ring 1212, but do not weld them;

[0092] S1320: Two half-tube segments 1013 are opened on the outer tube 1012 at the location of the rigid support 121, and several runway holes 1014 are opened on the half-tube segments 1013.

[0093] S1330: Weld the rigid support 121 onto the inner tube 1011;

[0094] S1340: Insert the support plate 1211 into the runway hole 1014 and weld it;

[0095] S1350: Two half-tube segments 1013 are joined together and welded to form a tube;

[0096] S1360: The tube formed in S1350 is joined together with the outer tube 1012 in a ring, and then welded.

[0097] S1370: Perform non-destructive testing on weld 4 on outer tube 1012 to ensure that weld 4 meets the requirements.

[0098] like Figure 4 As shown, the location of the non-destructive testing 210 is for illustrative purposes only and can be used at any weld location where this testing is required.

[0099] Example 2

[0100] like Figure 1-7 As shown, a low flash point fuel double-walled pipe 101 device includes a double-walled pipe 101, a half-pipe segment 1013, a first gas source 102, a second gas source 103, an overflow pipe 106, a blower 107, an air inlet pipe 1071, an air outlet pipe 1072, a pressure test pipe 108, a first valve group 110, a second valve group 111, and a pipe cap. The pipe cap is located at one end of the outer pipe 1012. The pressure test pipe 108 is connected to the air outlet pipe 1072. The blower 107 is connected to one end of the air outlet pipe 1072 through the outer pipe 1012. The blower 107 is also equipped with a differential pressure sensor 201 for monitoring the pressure difference between the inlet and outlet of the blower 107. The first valve assembly 110 and the second valve assembly 111 are respectively connected to both ends of the inner pipe 1011. The first valve assembly 110 is installed between the supply pipe 104 and the inner pipe 1011, and the second valve assembly 111 is installed between the return pipe 105 and the inner pipe 1011. Both the first valve assembly 110 and the second valve assembly 111 are equipped with relief valves. Figure 1 The area within the dashed box is the installation location 3.

[0101] The double-walled pipe 101 includes a first control valve 112, a second control valve 113, a first argon filling pipe 1091, a second argon filling pipe 1092, a first welding position 130, an nth welding position 131, an outer pipe 1012, and an inner pipe 1011 welded inside the outer pipe 1012. The exhaust pipe 1072 is connected to the first control valve 112 and the outer pipe 1012 at both ends. The inner pipe 1011 includes a supply pipe 104 for conveying fuel to the main unit and a return pipe 105 for returning excess fuel. The second control valve 113 is located on the path of the outer pipe 1012 connecting to the overflow pipe 106 (i.e., between the overflow pipe 106 and the flow meter 202 or the last welding position 132; there is no inner pipe 1011 inside this section of the outer pipe 1012, and the inner pipe 1011 has been extended from the flow meter 202 and the last welding position 132 to connect with the second valve group 111).

[0102] The first air source 102 and the second air source 103 are installed side by side in the air inlet pipe 1071 of the double-walled pipe 101. The overflow pipe 106 is installed on the air inlet pipe 1071. The gas is drawn out by the fan 107. The gas originating from the first air source 102 and / or the second air source 103 flows in the annular space of the double-walled pipe 101 under negative pressure.

[0103] Between the inner pipe 1011 and the outer pipe 1012, there are also a number of flexible support members 120 and a number of rigid support members 121. The flexible support members 120 and the rigid support members 121 are combined to provide support, so as to eliminate the uneven force caused by the thermal expansion force when the fuel medium is transported into and out of the engine 100 through the pipeline and the vibration from the engine 100, and prevent the pipeline vibration level from being too high.

[0104] Some flexible support components 120 are located at the front and rear ends of the elbow of the inner tube 1011;

[0105] Rigid support 121 and some flexible support 120 are located in the straight section of the inner tube 1011 and are arranged in sequence at intervals. The maximum support spacing L (or interval length) is L. The value of L is set and adjusted according to the diameter of the double-walled tube 101 so that the double-walled tube 101 can get sufficient and appropriate support in the annular space.

[0106] Depending on the fuel flow direction, there are at least three flexible support members 120. One flexible support member 120 is set at the front end of the elbow and two are set at the rear end of the elbow. The two flexible support members 120 at the rear end of the elbow are installed at an angle that is 90° off from the inner tube 1011 to dissipate the thermal expansion force brought by the fuel to the inner tube 1011, provide radial flexibility, and avoid uneven stress and excessive pipeline vibration from damaging the outer tube 1012.

[0107] The flexible support 120 includes two semi-circular portions 1202 and two fastening portions 1203, with the two ends of the semi-circular portions 1202 extending to form arc-shaped elastic portions 1201;

[0108] Two arc-shaped elastic parts 1201 are symmetrically distributed. Their arc-shaped parts are in contact with the inner wall of the outer tube 1012. The arc-shaped elastic parts 1201 apply elastic force to the inner wall of the outer tube 1012. The arc-shaped elastic parts 1201 can generate radial flexibility, dissipate the expansion force between the inner tube 1011 and the outer tube 1012, and provide effective support.

[0109] An anti-static and low-temperature resistant insulating sheet is also installed on the arc-shaped elastic part 1201 to isolate the arc-shaped elastic part 1201 from the outer tube 1012, so as to avoid frictional sparks and facilitate sliding.

[0110] The rigid support 121 includes a support plate 1211 and a support ring 1212. The outer tube 1012 has two half-tube segments 1013 at the position of the rigid support 121. Several runway holes 1014 are opened on the half-tube segments 1013. The number of support plates 1211 is the same as the number of runway holes 1014 and they are welded together.

[0111] The support ring 1212 is a circular tube, sleeved on the inner tube 1011 and welded. One end of the support plate 1211 is welded to the support ring 1212, and the other end of the support plate 1211 is welded to the runway hole 1014. The support plates 1211 are arranged in a ring array between the inner tube 1011 and the outer tube 1012 to achieve uniform force distribution and rigid support between the inner tube 1011 and the outer tube 1012.

[0112] In the two embodiments described above, the double-walled pipe 101 is connected to the engine 100, and the double-walled pipe 101 device is equipped with a pressure test pipe 108, which has a pressure test function. One end of the pressure test pipe 108 is connected to a second argon filling pipe 1092, and one end of the first valve group 110 is connected to the first argon filling pipe 1091. The first argon filling pipe 1091 and the second argon filling pipe 1092 are connected to the first gas source 102 and the second gas source 103. The pressure test method for the inner pipe 1011 is as follows: the first gas source 102 enters the supply pipe 104 through the first argon filling pipe 1091 for pressure test, and the vent ports of the second valve group 111 and the first valve group 110 are closed during the pressure test. The pressure test method for the outer pipe 1012 is as follows: the first gas source 102 enters the outer pipe 1012 through the second argon filling pipe 1092 and the pressure test pipe 108 for pressure test, and the first control valve 112 and the second control valve 113 are closed during the pressure test. The pressure test should be conducted for at least 15 minutes to check for leaks in weld 4.

[0113] When the engine 100 is working, the first gas source 102 delivers nitrogen into the inner and outer annular spaces of the double-walled pipe 101, and it is drawn out by the fan 107. Some of the nitrogen is discharged through the overflow pipe 106. The annular space of the double-walled pipe 101 is kept under negative pressure so that when there is a fuel leak in the inner pipe 1011, the gas detector 203 (installed on the exhaust pipe 1072) can detect and alarm immediately.

[0114] The negative pressure state of the annular space of the double-walled pipe 101 is monitored by a differential pressure detector. If the pressure exceeds the set threshold when the engine 100 is working, an alarm will be triggered and the first valve group 110 will be shut off to stop supplying low flash point fuel to the engine 100 and switch to supplying other fuels to the engine 100.

[0115] The first gas source 102 provides nitrogen, and the second gas source 103 provides argon. The ratio of nitrogen to argon mixture is controlled by adjusting the opening of their respective outlet valves to improve the quality of weld 4 on the inner tube 1011 and outer tube 1012. Specifically, this improves the mechanical properties and forming quality of weld 4. The double-walled tube 101 is made of austenitic stainless steel to accommodate low-temperature, low-flash-point fuel transportation.

[0116] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 method for assembling a low flash point fuel double-walled tube (101) device, characterized in that, Includes the following steps: S1000: The outer pipe (1012) is pre-cut into two half-pipe segments (1013), and the outer pipe (1012) is welded together after the inner pipe (1011) is completed. Step S1000 includes: S1110: In sequence according to the direction of fuel transportation in the inner tube (1011), the closing positions of the double-walled tube (101) are set as the first welding position (130), the nth welding position (131), and the last welding position (132), where n is a positive integer; S1120: The supply pipe (104) is inserted into the outer pipe (1012) through the pipe cap to form the beginning end of the double-walled pipe (101). Its first closure is the first weld position (130). The return pipe (105) passes through the outer pipe (1012) through the pipe cap. This is the end of the double-walled pipe (101). The last closure before the end is the last weld position (132). The several weld positions in the middle are the nth weld position (131). S1130: The double-walled tube (101) is joined together in sequence according to the first welding position (130), the nth welding position (131) and the last welding position (132); The welding methods for the first weld position (130) and the nth weld position (131) include: S1121: The first gas source (102) and / or the second gas source (103) provide a nitrogen-argon mixture through the first argon filling pipe (1091) connected to the inlet of the first valve group (110), and continuously inject it into the inner tube (1011) to meet the flow rate required for argon arc welding; S1122: Weld the weld (4) of the inner tube (1011) and perform non-destructive testing on the weld (4) of the inner tube (1011) to ensure that the weld (4) meets the requirements; S1123: The second gas source (103) provides argon gas, which is connected to the test tube (108) through the second argon filling tube (1092) and is filled into the annular space of the double-walled tube (101) through the test tube (108); S1124: Weld the half-pipe segment (1013) on the weld (4) of the outer tube (1012) together, and perform non-destructive testing on the weld (4) of the outer tube (1012) to ensure that the weld (4) meets the requirements; The final welding position (132) welding closure method includes the following steps: S1125: The first gas source (102) and / or the second gas source (103) provide nitrogen-argon mixture gas through the first argon filling pipe (1091) connected to the inlet of the first valve group (110), continuously injecting it into the inner pipe (1011) to meet the flow rate required for argon arc welding, and finally discharging it through the vent of the second valve group (111); S1126: Perform weld (4) on the inner tube (1011) and perform non-destructive testing on the weld (4) of the inner tube (1011) to ensure that the weld (4) meets the requirements; S1127: The first gas source (102) and the second gas source (103) provide nitrogen-argon mixture through the air inlet pipe (1071) and fill the annular space of the double-walled pipe (101). The fan (107) is started to form negative pressure ventilation. Part of the mixture overflows from the overflow pipe (106) to ensure that no air is mixed in the mixture entering the double-walled pipe (101). By ensuring the composition of the nitrogen-argon mixture, the quality of the weld (4) is ensured. S1128: Weld the half-pipe segment (1013) on the weld (4) of the outer pipe (1012) together, and perform non-destructive testing on the weld (4) of the outer pipe (1012) to ensure that the weld (4) meets the requirements.

2. The assembly method of a low flash point fuel double-walled tube (101) device according to claim 1, characterized in that, The construction method for the inner pipe (1011) in step S1000 is as follows: S1210: The two semicircular parts (1202) are symmetrically wrapped around the inner tube (1011) and fastened to the inner tube (1011) by the fastening part (1203), and are integrated into one piece; S1220: Using a clamp (1205) as an installation tool, wrap around all the arc-shaped elastic parts (1201) and tighten the clamp (1205) with the bolts to compress the arc-shaped elastic parts (1201); S1230: After pressing, make its outer diameter smaller than the inner diameter of the outer tube (1012), then push it into the outer tube (1012), and stop before the edge of the outer tube (1012) touches the edge of the clamp (1205); S1240: Loosen the clamp (1205) and push the inner tube (1011) with the flexible support (120) installed into the outer tube (1012) to reach the designated position.

3. The assembly method of a low flash point fuel double-walled tube (101) device as described in claim 2, characterized in that, After installing the flexible support (120), install the rigid support (121) as follows: S1310: Insert a support ring (1212) onto the inner tube (1011). S1320: Two half-tube segments (1013) are opened on the outer tube (1012) at the location of the rigid support (121), and several runway holes (1014) are opened on the half-tube segments (1013). S1330: Weld the rigid support (121) onto the inner tube (1011); S1340: Insert the support plate (1211) into the runway hole (1014) and weld it; S1350: Two half-tube segments (1013) are joined together and welded to form a tube; S1360: The tube formed in S1350 is joined together with the outer tube (1012) in a ring, and then welded. S1370: Perform non-destructive testing on the weld (4) on the outer tube (1012) to ensure that the weld (4) meets the requirements.

4. A device for assembling a low flash point fuel double-walled tube (101) according to any one of claims 1-3, characterized in that, It includes a double-walled pipe (101), a half-pipe segment (1013), a first air source (102), a second air source (103), an overflow pipe (106), a fan (107), an air inlet pipe (1071), an air outlet pipe (1072), a pressure test pipe (108), a first valve group (110), a second valve group (111), and a pipe cap. The pipe cap is located at one end of the outer pipe (1012), and the pressure test pipe (108) is connected to the air outlet pipe (1072). The double-walled pipe (101) includes a first control valve (112), a second control valve (113), a first argon filling pipe (1091), a second argon filling pipe (1092), a first welding position (130), an nth welding position (131), a last welding position (132), an outer pipe (1012), and an inner pipe (1011) welded inside the outer pipe (1012). The exhaust pipe (1072) is connected to the first control valve (112) and the outer pipe (1012) at both ends. The inner pipe (1011) includes a supply pipe (104) for conveying fuel to the main unit and a return pipe (105) for returning excess fuel. The first valve group (110) is installed on the supply pipe (104), and the second valve group (111) is installed on the return pipe (105). The first gas source (102) and the second gas source (103) are installed side by side in the air inlet pipe (1071) of the double-walled pipe (101). The overflow pipe (106) is installed on the air inlet pipe (1071). The gas is drawn out by the fan (107). The gas originating from the first gas source (102) and / or the second gas source (103) flows in the annular space of the double-walled pipe (101) under negative pressure.

5. The low flash point fuel double-walled tube (101) device according to claim 4, characterized in that, Several flexible support members (120) and several rigid support members (121) are also provided between the inner tube (1011) and the outer tube (1012). Some of the flexible support members (120) are located at the front end and rear end of the elbow of the inner tube (1011); Rigid support member (121) and some flexible support member (120) are located in the straight section of the inner tube (1011) and are arranged in sequence at intervals.

6. The low flash point fuel double-walled tube (101) device according to claim 5, characterized in that, The flexible support (120) has at least three parts. One flexible support (120) is set at the front end of the elbow and two are set at the rear end of the elbow. The two flexible support (120) located at the rear end of the elbow are installed at an angle that is 90° off from the inner tube (1011).

7. The low flash point fuel double-walled tube (101) device according to claim 6, characterized in that, The flexible support (120) includes two semi-circular portions (1202) and two fastening portions (1203), with the two ends of the semi-circular portions (1202) extending to form arc-shaped elastic portions (1201). Two arc-shaped elastic parts (1201) are symmetrically distributed, and their arc-shaped parts are in contact with the inner wall of the outer tube (1012); An antistatic and low-temperature resistant insulating sheet is mounted on the arc-shaped elastic part (1201).

8. The low flash point fuel double-walled tube (101) device according to claim 7, characterized in that, The rigid support member (121) includes a support plate (1211) and a support ring (1212) component. The outer tube (1012) has two half-tube segments (1013) at the position of the rigid support member (121). Several runway holes (1014) are opened on the half-tube segments (1013). The number of support plates (1211) is the same as the number of runway holes (1014) and they are welded together. The support ring (1212) is a circular tube, sleeved on the inner tube (1011) and welded. One end of the support plate (1211) is welded to the support ring (1212), and the other end of the support plate (1211) is welded to the runway hole (1014). The support plate (1211) is arranged in a ring array between the inner tube (1011) and the outer tube (1012).

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