Low-flash-point fuel double-wall pipe device and assembling method thereof

Abstract

The invention relates to the technical field of low-flash-point fuel double-wall pipe devices, provides a low-flash-point fuel double-wall pipe device and an assembly method thereof, and forms a set of high-efficiency welding, folding and mounting process for an inner pipe and an outer pipe of a double-wall pipe to ensure that the welding requirement is fully met so as to improve the mechanical property of a welding seam and improve the forming quality of the welding seam. And the one-time inspection qualification rate is high.

Description

Technical Field

[0001] The invention relates to the technical field of double-walled pipe devices for low-flash-point fuels, and in particular to a double-walled pipe device for low-flash-point fuels and an assembly method thereof. Background Art

[0002] With the frequent occurrence of extreme weather, the global requirements for carbon emission reduction are becoming more and more stringent, and the use of low-carbon clean fuels on ships has become a major trend in the industry. Among them, LPG, LEG, ammonia fuel, etc. have gradually become alternative fuel options recognized by the industry. However, due to the characteristics of low temperature, low flash point, flammability and explosion, these fuels have much higher requirements for their use on ships than general traditional fuels. For example, LPG fuel has a lower explosion limit concentration of 1.5%, and it is heavier than air. It is easy to aggregate and cause explosion after leakage. For example, ammonia fuel, once leaked, the concentration of ammonia in the air reaches 100ppm, which will cause discomfort to the human body, and it will start to cause harm to the human body when it reaches 250ppm. In order to reduce accidents caused by pipeline leakage, the fuel pipelines on ships are generally made of austenitic stainless steel materials. The main connection method is butt welding, and the welding quality needs to be good enough. When RT non-destructive testing is used for filming, the one-time pass rate of the weld is required to reach 99%, and the argon gas flow rate and concentration at the weld are key indicators affecting the weld pass rate.

[0003] According to the needs of the engine, these fuels are all supplied from the fuel tank, and after being temperature-controlled and pressurized by the fuel supply unit, they are supplied to the engine in liquid form for combustion and work. The surplus fuel returns to the fuel tank from the return pipe. In order to enhance safety, in the prior art, the cabin where the engine is located is set as a safe place, and the fuel pipeline uses a double-walled pipe, which has an inner pipe and an outer pipe. The fuel is transported through the inner pipe. Once the inner pipe is damaged and leaks, the leakage can be controlled between the inner and outer pipes for secondary protection to avoid entering the engine compartment and causing fire or explosion accidents. In the actual application of general projects at present, the common double-walled pipe layout has the following problems and disadvantages:

[0004] 1. The welding and closing process of the inner and outer tubes of the double-walled pipe is complicated, inefficient and inconvenient to install.

[0005] 2. When the double-walled pipe is closed and welded, the inner and outer pipes require separate temporary argon-filled fixtures. The temporary fixtures are temporarily sealed with cardboard, which is prone to leakage. The flow is difficult to control, the argon filling is insufficient, and the concentration is often not up to standard without a monitoring device, resulting in low weld quality and a low one-time inspection pass rate.

[0006] 3. It is difficult to fill the last weld with argon, the quality of the closed weld is extremely poor, the pass rate is extremely low, and there is a high possibility of leakage.

[0007] 4. The support between the inner and outer tubes of the double-walled tube is unreasonable, which cannot eliminate the uneven force caused by thermal expansion during fuel transportation and the vibration from the engine, causing the double-walled tube to be easily damaged and leaked, posing a safety risk. Summary of the invention

[0008] One of the purposes of the present invention is to propose a method for assembling a double-walled pipe device for low-flash point fuel, forming a set of high-efficiency welding, closing and installation processes that take into account the inner pipe and outer pipe of the double-walled pipe, ensuring that the welding requirements are fully met to improve the mechanical properties of the weld and improve the forming quality of the weld, with a high one-time inspection pass rate.

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

[0010] A method for assembling a low-flashpoint fuel double-wall pipe device comprises the following steps:

[0011] S1000: The outer tube is cut into two half-tube segments in advance, and the outer tube is welded and closed after the inner tube construction is completed;

[0012] Step S1000 includes:

[0013] S1110: setting the closing positions of the double-walled tube to the first welding position, the nth welding position, and the last welding position in sequence according to the direction in which the fuel is transported in the inner tube, where n is a positive integer;

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

[0015] S1130: The double-walled pipe is closed in sequence at the first welding position, the nth welding position and the last welding position.

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

[0017] S1121: The first gas source and / or the second gas source provides a nitrogen-argon mixed gas which is connected to the inlet of the first valve group through the first argon filling pipe and continuously injected into the inner pipe to meet the flow rate required for argon arc welding;

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

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

[0020] S1124: Weld the half pipe 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 closing method of the last welding position in step S1120 includes the following steps:

[0022] S1125: The first gas source and / or the second gas source provides a nitrogen-argon mixed gas which is connected to the inlet of the first valve group through the first argon filling pipe, is continuously injected into the inner tube to meet the flow rate required for argon arc welding, and is finally discharged through the discharge port of the second valve group;

[0023] S1126: Weld the inner pipe welds and perform nondestructive testing on the inner pipe welds to ensure that the welds meet the requirements;

[0024] S1127: The first gas source and the second gas source provide nitrogen-argon mixed gas through the air inlet pipe and fill it into the annular space of the double-walled pipe. The fan is started to form negative pressure ventilation. Part of the mixed gas overflows from the overflow pipe to ensure that the mixed gas entering the double-walled pipe is not mixed with air. The quality of the weld is ensured by ensuring the composition of the nitrogen-argon mixed gas;

[0025] S1128: Weld the half pipe 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 of the inner tube in step S1000 is as follows:

[0027] S1210: The two semicircular parts are symmetrically wrapped around the inner tube and fastened to the inner tube through the fastening parts to form a whole;

[0028] S1220: Using a clamp as an installation tool to encircle all the arc-shaped elastic parts, and tightening the clamp with a bolt of the clamp to compress the arc-shaped elastic parts;

[0029] S1230: After tightening, make its outer diameter smaller than the inner diameter of the outer tube, and 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 clamp and continue to push the inner tube with the flexible support installed into the outer tube to reach the specified position.

[0031] Further, after the flexible support is installed, the rigid support is installed, and the steps are as follows:

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

[0033] S1320: Open two half-pipe segments on the outer pipe at the location of the rigid support, and open a plurality of runway holes on the half-pipe segments;

[0034] S1330: Welding the rigid support member to the inner tube;

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

[0036] S1350: welding two half pipe segments together to form a pipe;

[0037] S1360: the tube formed in S1350 is butt-jointed with the outer tube, closed, and welded;

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

[0039] Another object of the present invention is to provide a low-flash point fuel double-wall pipe device, comprising a double-wall pipe, a half pipe segment, a first gas source, a second gas source, an overflow pipe, a fan, an air inlet pipe, an exhaust 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 pipe, and the pressure test pipe is connected to the exhaust 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 delivering fuel to the main engine 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 air source and the second air source are installed in parallel on the double-walled tube air inlet pipe, and the overflow pipe is arranged on the air inlet pipe. Through the exhaust of the fan, the gas from the first air source and / or the second air source circulates in the annular space of the double-walled tube under negative pressure.

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

[0043] Some of the flexible support members are respectively located at the front end and the rear end of the inner pipe elbow;

[0044] The rigid support members and part of the flexible support members are located in the straight pipe section of the inner pipe and are arranged in sequence and at intervals.

[0045] Furthermore, there are at least three flexible support members, one of which is arranged at the front end of the elbow and two are arranged at the rear end of the elbow. The installation angles of the two flexible support members located at the rear end of the elbow are staggered by 90° around the inner tube.

[0046] Furthermore, the flexible support member includes two semicircular portions and two fastening portions, and both ends of the semicircular portions extend to form arc-shaped elastic portions;

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

[0048] The arc-shaped elastic part is provided with an antistatic and low-temperature resistant insulating sheet.

[0049] Furthermore, the rigid support member includes a support plate and a support ring member, the outer tube is provided with two half-tube segments at the position where the rigid support member is located, a plurality of runway holes are opened on the half-tube segments, the number of the support plates is the same as the number of the runway holes, and the half-tube segments are welded;

[0050] The support ring is in a circular tubular shape, 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, and the support plate is arranged in a ring array between the inner tube and the outer tube.

[0051] The working principle and beneficial effects of the present invention are:

[0052] 1. Form a set of efficient welding, closing and installation processes that take into account both the inner and outer tubes of double-walled pipes.

[0053] 2. When the double-wall pipe is closed and welded, 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 ratio and concentration are detected by a monitoring device to ensure that the welding requirements are fully met, so as to improve the mechanical properties of the weld and improve the forming quality of the weld, and the one-time inspection pass rate is high.

[0054] 3. The argon filling of the last weld is more reasonable and convenient, and the quality of the closed weld is good.

[0055] 4. Reasonable arrangement of the inner and outer pipes through a combination of flexible and rigid supports can eliminate the uneven force caused by thermal expansion and the vibration from the engine, reduce the risk of damage and leakage of double-wall pipes, and improve safety.

[0056] 5. The flexible support is used to accommodate the low friction sliding and vibration of the thermal expansion of the inner pipe relative to the outer pipe. It is easy to assemble and is used to create radial flexibility in the annular space designated as a hazardous area to accommodate the thermal expansion of the inner pipe relative to the outer pipe at the bend. When subjected to engine room vibration, it can maintain radial flexibility in contact to avoid damage to the outer pipe, thereby minimizing the source of leakage from the outer pipe and preventing excessive vibration levels of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0059] Figure 2 It is a cash register with double-walled tube structure;

[0060] Figure 3 is a schematic diagram of the rigid support structure;

[0061] Figure 4 It is a schematic diagram of assembling the rigid support member and the flexible support member;

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

[0063] Figure 6 A schematic diagram of pre-assembly of a flexible support member;

[0064] Figure 7 This is a schematic diagram of the installation of a flexible support with a 90° rotation.

[0065] In the figure: 100, engine; 101, double-walled pipe; 1011, inner pipe; 1012, outer pipe; 1013, half pipe segment; 1014, runway hole; 102, first gas source; 103, second gas source; 104, supply pipe; 105, return pipe; 106, overflow pipe; 107, fan; 1071, air inlet pipe; 1072, exhaust pipe; 108, pressure test pipe; 1091, first argon filling pipe; 1092, second argon filling pipe; 110, first valve group; 111, second valve group; 112, first control valve; 113, Second control valve; 120, flexible support member; 1201, arc-shaped elastic portion; 1202, semicircular portion; 1203, fastening portion; 1205, clamp; 121, rigid support member; 1211, support plate; 1212, support ring; 130, first welding position; 131, nth welding position; 132, last welding position; L, support spacing; 201, differential pressure sensor; 202, flow meter; 203, gas detector; 210, non-destructive testing; 3, installation location; 4, weld; 5, installation with 90° rotation; 6, fuel flow direction. DETAILED DESCRIPTION

[0066] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0067] Embodiment 1

[0068] like Figure 1-7 As shown, a method for assembling a low-flashpoint fuel double-walled pipe 101 device comprises the following steps:

[0069] S1000: The outer tube 1012 is cut into two half tube segments 1013 in advance, and the outer tube 1012 is welded and closed after the construction of the inner tube 1011 is completed.

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

[0071] S1110: sequentially according to the direction in which the fuel is transported in the inner tube 1011, the closing positions of the double-walled tube 101 are set to 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 starting end of the double-wall pipe 101. The first closing mouth is the first welding position 130. The return pipe 105 passes through the outer pipe 1012 through the pipe cap. This is the end of the double-wall pipe 101. The last closing mouth before the end is the last welding position 132. The several welding positions in the middle are the nth welding positions 131.

[0073] S1130: closing the double-walled tube 101 in sequence at the first welding position 130, the nth welding position 131 and the last welding position 132.

[0074] During welding, when the gas detector 203 detects that the concentration of the nitrogen-argon mixed gas meets the requirements, welding is performed; at the same time, when the differential pressure detector detects negative pressure, welding of the last welding position 132 is performed.

[0075] The welding closing method in step S1120 includes:

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

[0077] S1122: welding the weld 4 of the inner tube 1011, and performing nondestructive testing on the weld 4 of the inner tube 1011 to ensure that the weld 4 meets the requirements;

[0078] S1123: the second gas source 103 provides argon gas which is connected to the test pressure 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 pressure tube 108;

[0079] S1124: The half pipe segments 1013 on the weld seam 4 of the outer pipe 1012 are welded together, and the weld seam 4 of the outer pipe 1012 is subjected to nondestructive testing to ensure that the weld seam 4 meets the requirements.

[0080] The welding closing method of the last welding position 132 in step S1120 includes the following steps:

[0081] S1125: The first gas source 102 and / or the second gas source 103 provides a nitrogen-argon mixed gas which is connected to the inlet of the first valve group 110 through the first argon filling pipe 1091, and is continuously injected into the inner tube 1011 to meet the flow rate required for argon arc welding, and is finally discharged through the discharge port of the second valve group 111;

[0082] S1126: welding the weld 4 of the inner tube 1011, and performing nondestructive testing on the weld 4 of the inner tube 1011 to ensure that the weld 4 meets the requirements;

[0083] S1127: The first gas source 102 and the second gas source 103 provide nitrogen-argon mixed gas through the air inlet pipe 1071, which is filled into the annular space of the double-walled tube 101. The fan 107 is started to form negative pressure ventilation, and part of the mixed gas overflows from the overflow pipe 106 to ensure that the mixed gas entering the double-walled tube 101 is not mixed with air. The quality of the weld 4 is ensured by ensuring the composition of the nitrogen-argon mixed gas;

[0084] S1128: The half pipe segments 1013 on the weld seam 4 of the outer pipe 1012 are welded together, and the weld seam 4 of the outer pipe 1012 is subjected to nondestructive testing to ensure that the weld seam 4 meets the requirements.

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

[0086] S1210: The two semicircular parts 1202 are symmetrically wrapped around the inner tube 1011, and are fastened to the inner tube 1011 through the fastening parts 1203 to form a whole;

[0087] S1220: Using the clamp 1205 as an installation tool, encircling all the arc-shaped elastic parts 1201, and tightening the clamp 1205 using the bolts of the clamp 1205, so that the arc-shaped elastic parts 1201 are compressed;

[0088] S1230: After pressing, the outer diameter of the outer tube 1012 is smaller than the inner diameter, and then the outer tube 1012 is pushed into the outer tube 1012, and the outer tube 1012 stops before the edge of the outer tube 1012 touches the edge of the clamp 1205;

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

[0090] After the flexible support member 120 is installed, the rigid support member 121 is installed, and the steps are as follows:

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

[0092] S1320: Open two half-pipe segments 1013 on the outer pipe 1012 where the rigid support member 121 is located, and open a plurality of runway holes 1014 on the half-pipe segments 1013;

[0093] S1330: Welding the rigid support member 121 to the inner tube 1011;

[0094] S1340: insert the support plate 1211 into the runway hole 1014 for welding;

[0095] S1350: closing and welding two half tube segments 1013 to form a tube;

[0096] S1360: The tube formed in S1350 is butt-jointed with the outer tube 1012, closed, and welded;

[0097] S1370: Perform nondestructive testing on the weld 4 on the outer pipe 1012 to ensure that the weld 4 meets the requirements.

[0098] like Figure 4 As shown, the location of the nondestructive test 210 is for illustration only and can be used at any weld location where such test is required.

[0099] Embodiment 2

[0100] like Figure 1-7 As shown, a low flash point fuel double wall pipe 101 device includes a double wall pipe 101, a half pipe segment 1013, a first gas source 102, a second gas source 103, an overflow pipe 106, a fan 107, an air inlet pipe 1071, an exhaust 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 an outer pipe 1012, the pressure test pipe 108 is connected to the exhaust pipe 1072, the fan 107 is connected to one end of the exhaust pipe 1072, and a pressure difference sensor 201 for monitoring the pressure difference between the inlet and outlet of the fan 107 is also provided on the fan 107. The first valve group 110 and the second valve group 111 are connected to both ends of the inner tube 1011, respectively. The first valve group 110 is installed between the supply pipe 104 and the inner tube 1011, and the second valve group 111 is installed between the return pipe 105 and the inner tube 1011. The first valve group 110 and the second valve group 111 are provided with a discharge valve. Figure 1 The dotted line frame is the installation location 3.

[0101] The double-walled tube 101 includes a first control valve 112, a second control valve 113, a first argon filling tube 1091, a second argon filling tube 1092, a first welding position 130, an nth welding position 131, an outer tube 1012 and an inner tube 1011 welded inside the outer tube 1012. The exhaust tube 1072 is connected to the first control valve 112 and the outer tube 1012 at both ends. The inner tube 1011 includes a supply pipe 104 for delivering fuel to the main engine and a return pipe 105 for returning surplus fuel. The second control valve 113 is arranged on the path where the outer tube 1012 is connected 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 tube 1011 inside this section of the outer tube 1012. The inner tube 1011 has been extended out of the outer tube 1012 and connected to the second valve group 111 in advance between the flow meter 202 and the last welding position 132).

[0102] The first gas source 102 and the second gas source 103 are installed in parallel on the air inlet pipe 1071 of the double-walled tube 101, and the overflow pipe 106 is arranged on the air inlet pipe 1071. The fan 107 draws air, and the gas from the first gas source 102 and / or the second gas source 103 circulates in the annular space of the double-walled tube 101 under negative pressure.

[0103] A plurality of flexible support members 120 and a plurality of rigid support members 121 are also provided between the inner tube 1011 and the outer tube 1012. The flexible support members 120 and the rigid support members 121 are combined for support to eliminate the uneven force and vibration from the engine 100 caused by the thermal expansion force when the fuel medium is transported in and out of the engine 100 through the pipeline, thereby preventing the pipeline vibration level from being too high.

[0104] Part of the flexible support member 120 is located at the front end and the rear end of the elbow of the inner tube 1011;

[0105] The rigid support member 121 and part of the flexible support member 120 are located in the straight section of the inner tube 1011 and are spaced apart in sequence. The maximum support spacing L (or spacing length) is L. The value of L is set and adjusted according to the diameter of the double-walled tube 101 so that the annular space of the double-walled tube 101 can obtain sufficient and appropriate support.

[0106] According to the fuel flow direction, there are at least three flexible support members 120. The three flexible support members 120 are respectively arranged at the front end of the elbow, and two at the rear end of the elbow. The installation angles of the two flexible support members 120 located at the rear end of the elbow are staggered by 90° around 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 force and excessive pipeline vibration to damage the outer tube 1012.

[0107] The flexible support member 120 includes two semicircular portions 1202 and two fastening portions 1203 , and both ends of the semicircular portion 1202 extend to form an arc-shaped elastic portion 1201 ;

[0108] The two arc-shaped elastic parts 1201 are symmetrically distributed, and the arc-shaped parts thereof fit the inner wall of the outer tube 1012. The arc-shaped elastic parts 1201 exert elastic force on the inner wall of the outer tube 1012. The arc-shaped elastic parts 1201 can generate radial flexibility, eliminate 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 to avoid friction sparks and facilitate sliding.

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

[0111] The support ring 1212 is in the shape of a circular tube, which is 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 and rigid support between the inner tube 1011 and the outer tube 1012.

[0112] The double-walled tube 101 in the above two embodiments is connected to the engine 100, and the double-walled tube 101 device is provided with a pressure test tube 108, which has a pressure test function. One end of the pressure test tube 108 is connected to a second argon filling tube 1092, and one end of the first valve group 110 is connected to a first argon filling tube 1091. The first argon filling tube 1091 and the second argon filling tube 1092 are connected to the first gas source 102 and the second gas source 103. The pressure test method of the inner tube 1011 is: the first gas source 102 enters the supply tube 104 through the first argon filling tube 1091 for pressure test, and the discharge ports of the second valve group 111 and the first valve group 110 are closed during the pressure test; the pressure test method of the outer tube 1012 is: the first gas source 102 enters the outer tube 1012 through the second argon filling tube 1092 and the pressure test tube 108 for pressure test, and the first control valve 112 and the second control valve 113 are closed during the pressure test. During the pressure test, the pressure is maintained for no less than 15 minutes to test whether the weld 4 is leaking.

[0113] When the engine 100 is working, the first gas source 102 transports nitrogen into the inner and outer annular spaces of the double-walled tube 101, which is sucked out by the fan 107, and part of the nitrogen is discharged through the overflow pipe 106. The annular space of the double-walled tube 101 maintains a negative pressure state, so that when there is fuel leakage in the inner tube 1011, the gas detector 203 (installed on the exhaust pipe 1072) can detect it and alarm at the first time.

[0114] The negative pressure state of the annular space of the double-walled pipe 101 is monitored by a differential pressure detector. If it exceeds a set threshold when the engine 100 is working, an alarm is triggered and the first valve group 110 is cut off, and the supply of low-flashpoint fuel to the engine 100 is stopped, and other fuels are switched to supply the engine 100.

[0115] The first gas source 102 provides nitrogen, and the second gas source 103 provides argon. The ratio of the nitrogen-argon mixed gas is controlled by adjusting the opening of each outlet valve to improve the quality of the weld 4 on the inner tube 1011 and the outer tube 1012, which is specifically manifested in improving the mechanical properties of the weld 4 and improving the forming quality of the weld 4. The double-walled tube 101 is made of austenitic stainless steel tube to adapt to the transportation of low-temperature and low-flash point fuels.

[0116] The above are only 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 in the protection scope of the present invention.

Claims

1. A method for assembling a low-flashpoint fuel double-walled pipe (101) device, characterized in that: The steps include: S1000: pre-cutting the outer tube (1012) into two half tube segments (1013), and welding and closing the outer tube (1012) after the inner tube (1011) is completed; Step S1000 includes: S1110: sequentially setting the closing positions of the double-walled tube (101) to the first welding position (130), the nth welding position (131), and the last welding position (132) according to the direction in which the fuel is transported in the inner tube (1011), 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 starting end of the double-wall pipe (101). The first closing mouth is the first welding position (130). The return pipe (105) passes through the outer pipe (1012) through the pipe cap. This is the end of the double-wall pipe (101). The last closing mouth before the end is the last welding position (132). The welding positions in the middle are the nth welding positions (131). S1130: The double-walled tube (101) is closed in sequence at the first welding position (130), the nth welding position (131) and the last welding position (132).

2. A method for assembling a low-flashpoint fuel double-walled pipe (101) device, characterized in that: The welding closing method in step S1120 includes: S1121: The first gas source (102) and / or the second gas source (103) provide a nitrogen-argon mixed 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 tube (1011) to meet the flow rate required for argon arc welding; S1122: welding the weld (4) of the inner tube (1011), and performing nondestructive 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 pressure 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 pressure test tube (108); S1124: The half pipe segments (1013) on the weld seam (4) of the outer pipe (1012) are welded together, and the weld seam (4) of the outer pipe (1012) is subjected to non-destructive testing to ensure that the weld seam (4) meets the requirements.

3. The method for assembling a low-flashpoint fuel double-walled pipe (101) according to claim 2, characterized in that: The welding closing method of the last welding position (132) in step S1120 comprises the following steps: S1125: The first gas source (102) and / or the second gas source (103) provide a nitrogen-argon mixed gas which is connected to the inlet of the first valve group (110) through the first argon filling pipe (1091), and is continuously injected into the inner tube (1011) to meet the flow rate required for argon arc welding, and is finally discharged through the discharge port of the second valve group (111); S1126: welding the weld (4) of the inner tube (1011), and performing nondestructive 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 a nitrogen-argon mixed gas through the air inlet pipe (1071) and fill it into the annular space of the double-walled tube (101). The fan (107) is started to form negative pressure ventilation. Part of the mixed gas overflows from the overflow pipe (106) to ensure that no air is mixed into the mixed gas entering the double-walled tube (101). By ensuring the composition of the nitrogen-argon mixed gas, the quality of the weld (4) is ensured. S1128: The half pipe segments (1013) on the weld seam (4) of the outer pipe (1012) are welded together, and the weld seam (4) of the outer pipe (1012) is subjected to non-destructive testing to ensure that the weld seam (4) meets the requirements.

4. The method for assembling a low-flashpoint fuel double-walled pipe (101) according to claim 2, characterized in that: The construction method of the inner tube (1011) in step S1000 is as follows: S1210: The two semicircular parts (1202) are symmetrically wrapped around the inner tube (1011), and are fastened to the inner tube (1011) through the fastening part (1203) to form a whole; S1220: Using the clamp (1205) as an installation tool to encircle all the arc-shaped elastic parts (1201), and tightening the clamp (1205) using the bolts of the clamp (1205) so that the arc-shaped elastic parts (1201) are compressed; S1230: After compaction, the outer diameter of the outer tube (1012) is made smaller than the inner diameter of the outer tube (1012), and then the outer tube (1012) is pushed into the outer tube (1012), and the outer tube (1012) stops before the edge of the outer tube (1012) touches the edge of the clamp (1205); S1240: Loosen the clamp (1205) and continue to push the inner tube (1011) with the installed flexible support member (120) into the outer tube (1012) to reach the specified position.

5. A method for assembling a low-flashpoint fuel double-walled pipe (101) device as claimed in claim 4, characterized in that: After the flexible support member (120) is installed, the rigid support member (121) is installed in the following steps: S1310: inserting a support ring (1212) onto the inner tube (1011); S1320: Opening two half-tube segments (1013) on the outer tube (1012) where the rigid support member (121) is located, and opening a plurality of runway holes (1014) on the half-tube segments (1013); S1330: welding the rigid support member (121) to the inner tube (1011); S1340: inserting the support plate (1211) into the runway hole (1014) for welding; S1350: closing and welding two half tube segments (1013) to form a tube; S1360: The tube formed in S1350 and the outer tube (1012) are butt-jointed, closed, and welded in an annular manner; S1370: Perform nondestructive testing on the weld (4) on the outer pipe (1012) to ensure that the weld (4) meets the requirements.

6. A low-flash point fuel double-wall pipe (101) device assembled according to any one of the methods described in claims 1-5, characterized in that: It comprises a double-walled tube (101), a half tube sheet (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 exhaust pipe (1072), a pressure test pipe (108), a first valve group (110), a second valve group (111), and a pipe cap, wherein the pipe cap is located at one end of the outer tube (1012), and the pressure test pipe (108) is connected to the air exhaust pipe (1072); The double-walled tube (101) comprises a first control valve (112), a second control valve (113), a first argon filling tube (1091), a second argon filling tube (1092), a first welding position (130), an nth welding position (131), an outer tube (1012), and an inner tube (1011) welded inside the outer tube (1012); two ends of the exhaust tube (1072) are respectively connected to the first control valve (112) and the outer tube (1012); the inner tube (1011) comprises a supply tube (104) for conveying fuel to the main engine and a return tube (105) for returning surplus fuel; the first valve group (110) is installed on the supply tube (104), and the second valve group (111) is installed on the return tube (105); The first gas source (102) and the second gas source (103) are installed in parallel on the air inlet pipe (1071) of the double-walled tube (101), and the overflow pipe (106) is arranged on the air inlet pipe (1071). The air is drawn by the fan (107), and the gas originating from the first gas source (102) and / or the second gas source (103) is circulated in the annular space of the double-walled tube (101) under negative pressure.

7. The low-flashpoint fuel double-walled pipe (101) device according to claim 6, characterized in that: A plurality of flexible support members (120) and a plurality of rigid support members (121) are also provided between the inner tube (1011) and the outer tube (1012); Part of the flexible support members (120) are respectively located at the front end and the rear end of the elbow of the inner tube (1011); The rigid support member (121) and part of the flexible support member (120) are located in the straight pipe section of the inner pipe (1011) and are arranged in sequence and at intervals.

8. The low-flashpoint fuel double-walled pipe (101) device according to claim 7, characterized in that: The flexible support members (120) are at least three in number, one of the three flexible support members (120) being arranged at the front end of the elbow and two at the rear end of the elbow, respectively. The two flexible support members (120) located at the rear end of the elbow are installed at an angle of 90° rotated around the inner tube (1011).

9. The low-flashpoint fuel double-walled pipe (101) device according to claim 8, characterized in that: The flexible support member (120) comprises two semicircular portions (1202) and two fastening portions (1203), and both ends of the semicircular portion (1202) extend to form an arc-shaped elastic portion (1201); The two arc-shaped elastic parts (1201) are symmetrically distributed, and the arc-shaped parts thereof 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 portion (1201).

10. The low-flashpoint fuel double-walled pipe (101) device according to claim 9, characterized in that: The rigid support member (121) comprises a support plate (1211) and a support ring (1212) component; the outer tube (1012) is provided with two half-tube segments (1013) at the position where the rigid support member (121) is located; a plurality of runway holes (1014) are opened on the half-tube segments (1013); the number of the support plates (1211) is the same as the number of the runway holes (1014) and they are welded; The support ring (1212) is in the shape of 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), and the support plates (1211) are arranged in a ring array between the inner tube (1011) and the outer tube (1012).

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