An emergency disconnection and unloading arm system and method for LNG transportation

Abstract

The present invention relates to an emergency disconnection and unloading arm system for LNG transportation. The LNG unloading arm is disposed between an LNG carrier and an LNG storage tank, and includes a support column, an inner arm, a first outer arm, a second outer arm, and a conveying pipe passing through the support column, the inner arm, the first outer arm, and the second outer arm. There is a first rotary joint between the support column and the inner arm, a second rotary joint between the inner arm and the first outer arm, an emergency disconnection device between the first outer arm and the second outer arm, and a third rotary joint between the emergency disconnection device and the first outer arm. The emergency disconnection device separates the conveying pipe into a first conveying pipe and a second conveying pipe. The present invention has the following advantages: By means of an emergency disconnection method of first performing emergency disconnection and then closing the ball valve with an emergency disconnection device of a special structure, the ejection of the medium during emergency disconnection is avoided, and environmental pollution and accidental safety accidents are reduced.

Description

Technical Field

[0001] The present invention relates to the field of LNG, and specifically to an emergency disconnection unloading arm system and method for LNG transportation. Background Art

[0002] The safety condition of the LNG unloading arm operation determines whether the LNG on the transport ship can be smoothly transported to the LNG storage tank. However, if the LNG transport ship encounters uncontrollable factors, such as leakage of the unloading arm, conveying pipeline and valve, or the LNG transport ship drifts away from the safe working area due to factors such as waves and typhoons, it will cause the LNG transport ship to pull the unloading arm, resulting in damage to the unloading arm and LNG leakage, and even the unloading arm may topple, causing incalculable losses. At this time, the LNG transport ship and the unloading arm must be quickly separated. Otherwise, the volatile, ultra-low temperature, inflammable and explosive LNG will cause frostbite and asphyxiation to the staff, and even cause fire and explosion accidents. Usually, an emergency disconnection device is installed on the unloading arm to protect the safety of LNG unloading and personal safety, avoid environmental pollution and economic losses, and reduce the probability of LNG accidents.

[0003] In the existing LNG unloading arm, ball valves are respectively arranged on both sides of the emergency disconnection device. The emergency disconnection device docks the conveying pipes through structures such as a clamp body. During emergency disconnection, first start the ball valves on both sides of the emergency disconnection device, and then separate the two docked conveying pipes through the emergency disconnection device. However, there is a certain distance between the two ball valves. When the ball valves are suddenly closed, the medium flowing in the LNG unloading arm is blocked. However, there is a lot of medium between the two ball valves and in the emergency disconnection device. At this time, when the first conveying pipe and the second conveying pipe are quickly separated through the emergency disconnection device, the medium remaining between the two ball valves will be ejected outward as the unloading arm separates. Although the amount of ejection will not cause fire or explosion, it will cause a certain amount of LNG energy waste and pose a threat to personal safety. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above deficiencies, and provide an emergency disconnection unloading arm system and method for LNG transportation. Through an emergency disconnection method in which the emergency disconnection device with a special structure and the ball valve are opened simultaneously, the ejection of the medium during emergency disconnection is avoided, and environmental pollution and accidental safety accidents are reduced.

[0005] The object of the present invention is achieved by the following technical solutions: An emergency disconnection and unloading arm system for LNG transportation, where the unloading arm is placed between the LNG carrier and the LNG storage tank, and includes a support column, an inner arm, a first outer arm, a second outer arm, and a conveying pipe passing through the support column, the inner arm, the first outer arm, and the second outer arm. There is a first rotary joint between the support column and the inner arm, a second rotary joint between the inner arm and the first outer arm, an emergency disconnection device between the first outer arm and the second outer arm, a third rotary joint between the emergency disconnection device and the first outer arm, and the emergency disconnection device separates the conveying pipe into a first conveying pipe and a second conveying pipe;

[0006] The emergency disconnection device includes a first ball valve placed near the output end of the first conveying pipe and a second ball valve placed near the input end of the second conveying pipe. Inside the output end of the first conveying pipe, there is a jacking block. The inside of the jacking block is a hollow structure, and the upper end of the jacking block has a limiting plate that is in limiting cooperation with the output end of the first conveying pipe. The side end of the jacking block has a plurality of equally circumferentially distributed flow holes. The edge of the output end of the first conveying pipe extends vertically outward with a hollow guiding column. Inside the input end of the second conveying pipe, there is a spherical valve core and a spring. The inner wall of the second conveying pipe near the input end has a limiting ring for limiting the lower end of the hollow guiding column and the lower end of the jacking block. Outside the output end of the first conveying pipe, there is a first flange, and outside the input end of the second conveying pipe, there is a second flange. The first flange has a plurality of equally circumferentially distributed electromagnets, and the second flange has permanent magnets that are attracted to the plurality of electromagnets. The emergency disconnection device further includes a control unit electrically connected to the electromagnets. In the energized state, the polarity of the electromagnets is the same as the polarity of the permanent magnets;

[0007] At the central position of the lower end of the spherical valve core, there is a vertically arranged nested telescopic column. The spring is sleeved on the outer circumference of the nested telescopic column. The lower end of the nested telescopic column is fixedly connected to the inner wall of the second conveying pipe. When the spherical valve core is forced to compress the spring, the nested telescopic column telescopically moves inward to ensure the verticality of the movement of the spherical valve core.

[0008] A further improvement of the present invention is that when the first conveying pipe and the second conveying pipe are connected, the lower end of the hollow guiding column extends into the second conveying pipe and contacts the limiting ring, the lower end of the jacking block contacts the limiting ring, and the flow holes on the jacking block are placed inside the first conveying pipe, so as to realize the medium flow between the first conveying pipe and the second conveying pipe.

[0009] A further improvement of the present invention is that when the first conveying pipe and the second conveying pipe are disconnected, the hollow guiding column on the first conveying pipe disengages from the second conveying pipe, and the output end of the first conveying pipe is in limiting cooperation with the limiting plate at the upper end of the jacking block. At this time, the flow holes on the jacking block are placed at the outer side end of the first conveying pipe, so as to realize the medium blockage between the first conveying pipe and the second conveying pipe.

[0010] A further improvement of the present invention lies in that: the inner side of the hollow guide column has a first sealing layer.

[0011] A further improvement of the present invention lies in that: the inner end of the limit ring has a sealing surface that is in close fit contact with the spherical valve core.

[0012] A further improvement of the present invention lies in that: the lower end surface of the limit plate placed outside the hollow guide column has a second sealing layer.

[0013] An emergency disconnection method for an emergency disconnection and unloading arm system for LNG transportation, the specific steps include:

[0014] S1. When the LNG unloading arm is working normally, the control unit sends a power-off signal command to the electromagnet. After power-off, the electromagnet and the permanent magnet are fixed by magnetic attraction. At this time, the hollow guide column of the first delivery pipe is embedded in the second delivery pipe, and the lower end of the first delivery pipe is in limit contact with the upper end surface of the limit ring in the second delivery pipe. The lifting block in the first delivery pipe is lifted in the first delivery pipe under the limit contact of the limit ring, so that the flow hole on the lifting block is placed inside the first delivery pipe. When the medium flows in the delivery pipe of the LNG unloading arm, the medium flows into the lifting block through the flow hole of the first delivery pipe and presses the spherical valve core in the second delivery pipe, so that the spherical valve core is separated from the limit ring, and the medium flows into the second delivery pipe, thus realizing the medium circulation;

[0015] S2. When the LNG unloading arm is emergently disconnected, the control unit sends a power-on signal command to the electromagnet. At this time, the polarity of the electromagnet after power-on is the same as that of the permanent magnet, and the first delivery pipe and the second delivery pipe are quickly separated. At this time, the first delivery pipe and the hollow guide column are separated from the second delivery pipe, and the lifting block in the first delivery pipe is displaced downward relative to the first delivery pipe under the action of its own gravity and the flow force of the medium in the first delivery pipe until all the flow holes on the lifting block are placed outside the first delivery pipe. At this time, the medium circulation in the first delivery pipe is blocked; after the emergency disconnection, the residual medium in the first delivery pipe continues to flow into the second delivery pipe and continues to have a certain thrust on the spherical valve core, and the residual medium continues to be output to the second delivery pipe. When the medium thrust at the input end of the second delivery pipe is less than the reset elastic force of the spring, the spherical valve core moves upward under the elastic force of the spring and is in sealing contact with the limit ring. At this time, the medium circulation in the second delivery pipe is blocked;

[0016] S3. While the control unit sends a power-on signal command to the electromagnet in step S2, the control unit sends a closing signal command to the first ball valve and the second ball valve to block the medium in the first delivery pipe and the second delivery pipe.

[0017] The present invention has the following advantages compared with the prior art:

[0018] The emergency release device of the present invention comprises a lifting block placed in the first delivery pipe, a spherical valve core and a spring placed in the second delivery pipe. When the emergency release is in effect, the flow hole on the lifting block is placed outside the first delivery pipe as the first delivery pipe is released and the flow of the medium exerts a thrust on the lifting block, thereby blocking the flow of the medium in the first delivery pipe. The residual medium in the first and second delivery pipes in the emergency release device continues to exert a certain thrust on the spherical valve core in the second delivery pipe, thereby flowing into the second delivery pipe. When the medium in the second delivery pipe between the second ball valve and the spherical valve core exerts a thrust on the spherical valve core and the elastic force of the spring itself, the spherical valve core is released. The core cooperates with the limiting ring to achieve the blocking of the medium in the second delivery pipe; most importantly, the setting of the hollow guide column at the lower end of the first delivery pipe plays a certain guiding role when the first delivery pipe is connected to the second delivery pipe. Secondly, the setting of the first sealing layer on the inner side of the hollow guide column effectively avoids the leakage of the medium, and when the first delivery pipe is separated from the second delivery pipe, the hollow guide column is not completely separated from the second delivery pipe, and the injection of the medium is also avoided at the moment of emergency separation, which has a certain blocking effect on the medium. The present invention uses a special structure of emergency separation device to perform an emergency separation method in which the ball valve is opened at the same time, thereby avoiding the injection of the medium during emergency separation and reducing environmental pollution and accidental safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the LNG unloading arm in the present invention.

[0020] Figure 2 for Figure 1 Schematic diagram of the structure after the first delivery pipe and the second delivery pipe are connected through the emergency release device.

[0021] Figure 3 for Figure 1 Schematic diagram of the structure after the first conveying pipe and the second conveying pipe are separated by the emergency separation device.

[0022] Numbers in the figure:

[0023] 1-LNG carrier, 2-LNG storage tank, 3-support column, 4-inner arm, 5-first outer arm, 6-second outer arm, 7-transmission pipe, 8-first rotary joint, 9-emergency release device, 10-second rotary joint, 11-first transmission pipe, 12-second transmission pipe, 13-third rotary joint;

[0024] 91 - First ball valve, 92 - Second ball valve, 93 - Lifting block, 94 - Limiting plate, 95 - Flow hole, 96 - Hollow guiding column, 97 - First sealing layer, 98 - Spherical valve core, 99 - Spring, 910 - Limiting ring, 911 - First flange, 912 - Second flange, 913 - Electromagnet, 914 - Permanent magnet, 915 - Sealing surface, 916 - Second sealing layer, 917 - Nested telescopic column. Detailed implementation manner

[0025] To deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0026] An emergency disconnection and unloading arm system for LNG transportation in this embodiment, as Figure 1 shown, the unloading arm is placed between the LNG carrier 1 and the LNG storage tank 2, and includes a support column 3, an inner arm 4, a first outer arm 5, a second outer arm 6, and a conveying pipe 7 passing through the support column 3, the inner arm 4, the first outer arm 5, and the second outer arm 6. There is a first rotary joint 8 between the support column 3 and the inner arm 4, and a second rotary joint 10 between the inner arm 4 and the first outer arm 5. There is an emergency disconnection device 9 between the first outer arm 5 and the second outer arm 6. There is a third rotary joint 13 between the emergency disconnection device 9 and the first outer arm 5. The emergency disconnection device 13 separates the conveying pipe 7 into a first conveying pipe 11 and a second conveying pipe 12;

[0027] As Figure 2 , Figure 3 shown, the emergency disconnection device 9 includes a first ball valve 91 placed near the output end of the first conveying pipe 11 and a second ball valve 92 placed near the input end of the second conveying pipe 12. There is a lifting block 93 inside the output end of the first conveying pipe 11. The inside of the lifting block 93 is a hollow structure, and the upper end of the lifting block 93 has a limiting plate 94 that is limitedly matched with the output end of the first conveying pipe 11. The side end of the lifting block 93 has a plurality of flow holes 95 distributed equidistantly in a circumferential manner. The edge of the output end of the first conveying pipe 11 extends vertically outwards with a hollow guiding column 96. The inner side of the hollow guiding column 96 has a first sealing layer 97. There is a spherical valve core 98 and a spring 99 inside the input end of the second conveying pipe 12. The inner wall of the second conveying pipe 12 near the input end has a limiting ring 910 that limits the lower end of the hollow guiding column 96 and the lower end of the lifting block 93. The outside of the output end of the first conveying pipe 11 has a first flange 911, and the outside of the input end of the second conveying pipe 12 has a second flange 912. The first flange 911 has a plurality of electromagnets 913 distributed equidistantly in a circumferential manner, and the second flange 912 has permanent magnets 914 that are attracted to the plurality of electromagnets 913. The emergency disconnection device 9 further includes a control unit electrically connected to the electromagnets 913. In the energized state, the polarity of the electromagnets 913 is the same as the polarity of the permanent magnets 914;

[0028] When the first delivery pipe 11 is connected to the second delivery pipe 12, the lower end of the hollow guiding column 96 extends into the second delivery pipe 12 and contacts the limiting ring 910, the lower end of the jacking block 93 contacts the limiting ring 910, and the flow hole 95 on the jacking block 93 is placed inside the first delivery pipe 11, so as to realize the medium flow between the first delivery pipe 11 and the second delivery pipe 12; when the first delivery pipe 11 is separated from the second delivery pipe 12, the hollow guiding column 96 on the first delivery pipe 11 is separated from the second delivery pipe 12, and the output end of the first delivery pipe 11 is in limit cooperation with the limiting plate 94 at the upper end of the jacking block 93. At this time, the flow hole 95 on the jacking block 93 is placed at the outer end of the first delivery pipe 11, so as to realize the medium block between the first delivery pipe 11 and the second delivery pipe 12.

[0029] Further, a vertically arranged nested telescopic column 917 is provided at the central position of the lower end of the spherical valve core 98. The spring 99 is sleeved on the outer circumference of the nested telescopic column 917. The lower end of the nested telescopic column 917 is fixedly connected to the inner wall of the second delivery pipe 12. When the spherical valve core 98 is forced to compress the spring 99, the nested telescopic column 917 telescopically moves inward to ensure the verticality of the movement of the spherical valve core 98.

[0030] Further, the inner side end of the limiting ring 910 has a sealing surface 915 that is in close fit contact with the spherical valve core 98. The setting of the sealing surface 915 ensures the sealing fit between the limiting ring 910 and the spherical valve core 98. At the same time, the medium in the second delivery pipe 12 has a certain thrust on the spherical valve core 98, making the spherical valve core 98 and the sealing surface 915 more tightly sealed, and avoiding the leakage and spraying of the medium in the second delivery pipe 12 after separation.

[0031] Further, the lower end surface of the limiting plate 94 placed outside the hollow guiding column 96 has a second sealing layer 916. The setting of the second sealing layer 916 avoids the leakage of the medium in the first delivery pipe 11 after separation.

[0032] An emergency disconnection method for an emergency disconnection unloading arm system for LNG transportation, the specific steps include:

[0033] S1. When the LNG unloading arm is working normally, the control unit sends a power-off signal command to the electromagnet 913. After power-off, the electromagnet 913 and the permanent magnet 914 are fixed by magnetic attraction. At this time, the hollow guide column 96 of the first delivery pipe 11 is embedded in the second delivery pipe 12, and the lower end of the first delivery pipe 11 is in limit contact with the upper end face of the limit ring 910 in the second delivery pipe 12. The lifting block 93 in the first delivery pipe 11 is lifted in the first delivery pipe 11 under the limit contact of the limit ring 910, so that the through hole 95 on the lifting block 93 is placed in the first delivery pipe 11. When the medium flows in the delivery pipe 7 of the LNG unloading arm, the medium flows into the lifting block 93 through the through hole 95 of the first delivery pipe 11 and presses the spherical valve core 98 in the second delivery pipe 12, so that the spherical valve core 98 is separated from the limit ring 910, and the medium flows into the second delivery pipe 12, thus realizing the medium circulation;

[0034] S2. When the LNG unloading arm is emergently disengaged, the control unit sends a power-on signal command to the electromagnet 913. At this time, the polarity of the electromagnet 913 after power-on is the same as that of the permanent magnet 914, and the first delivery pipe 11 and the second delivery pipe 12 are quickly separated. At this time, the first delivery pipe 11 and the hollow guide column 96 are disengaged from the second delivery pipe 12, and the lifting block 93 in the first delivery pipe 11 is displaced downward relative to the first delivery pipe 11 under the action of its own gravity and the flow force of the medium in the first delivery pipe 11 until the through hole 95 on the lifting block 93 is completely outside the first delivery pipe 11. At this time, the medium circulation in the first delivery pipe 11 is blocked; after the emergency disengagement, the residual medium in the first delivery pipe 11 continues to flow into the second delivery pipe 12 and still has a certain thrust on the spherical valve core 98. The residual medium continues to be output to the second delivery pipe 12. When the medium thrust at the input end of the second delivery pipe 12 is less than the reset elastic force of the spring 99, the spherical valve core 98 moves upward under the elastic force of the spring 99 and is in sealing contact with the limit ring 910. At this time, the medium circulation in the second delivery pipe 12 is blocked;

[0035] S3. When the control unit sends a power-on signal command to the electromagnet 913 in step S2, the control unit sends a closing signal command to the first ball valve 91 and the second ball valve 92 to block the medium in the first delivery pipe 11 and the second delivery pipe 12.

[0036] The emergency disconnection device 9 in the present invention includes a jacking block 93 placed inside the first conveying pipe 11, a spherical valve core 98 and a spring 99 placed inside the second conveying pipe 12. When in emergency disconnection, the flow hole 95 on the jacking block 93 is placed outside the first conveying pipe 11 under the thrust action generated by the disconnection of the first conveying pipe 11 and the flow of the medium, thereby blocking the flow of the medium inside the first conveying pipe 11. The medium remaining in the emergency disconnection device 9 between the first conveying pipe 11 and the second conveying pipe 12 continues to generate a certain thrust on the spherical valve core 98 inside the second conveying pipe 12, and thus flows into the second conveying pipe 12. When the thrust of the medium placed between the second ball valve 92 and the spherical valve core 98 inside the second conveying pipe 12 on the spherical valve core 98 and the elastic force of the spring 99 itself act, the spherical valve core 98 cooperates with the limit ring 910, thereby realizing the blocking of the medium inside the second conveying pipe 12. Most importantly, the setting of the hollow guide column 96 at the lower end of the first conveying pipe 11 plays a certain guiding role when the first conveying pipe 11 is connected to the second conveying pipe 12. Secondly, the setting of the first sealing layer 97 inside the hollow guide column 96 effectively avoids the leakage of the medium. Moreover, when the first conveying pipe 11 is disconnected from the second conveying pipe 12, the hollow guide column 96 is not completely disconnected from the second conveying pipe 12, and the jet of the medium is also avoided at the moment of emergency disconnection, which has a certain blocking effect on the medium. The present invention adopts a disconnection method of simultaneous emergency disconnection and opening of the ball valve through the emergency disconnection device 9 with a special structure, avoiding the jet of the medium during emergency disconnection, reducing environmental pollution and accidental safety accidents.

[0037] In the present invention, the materials of the first flange 911 and the second flange 912 are iron that can be attracted by the permanent magnet 914. When the electromagnet 913 is not energized, the permanent magnet 914 of the second flange 912 is magnetically attracted to the first flange 911. After the electromagnet 913 is energized, since the polarity of the electromagnet 913 is the same as that of the permanent magnet 914, the repulsive force generated between the first flange 911 and the second flange 912 at this time is greater than the attractive force between the permanent magnet 914 and the first flange 911, thereby realizing the rapid separation of the first conveying pipe 11 and the second conveying pipe 12.

[0038] Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An emergency disconnection and unloading arm system for LNG transportation, the unloading arm is placed between the LNG carrier (1) and the LNG storage tank (2), characterized in that, It includes a support column (3), an inner arm (4), a first outer arm (5), a second outer arm (6), and a conveying pipe (7) passing through the support column (3), the inner arm (4), the first outer arm (5), and the second outer arm (6). There is a first rotary joint (8) between the support column (3) and the inner arm (4), a second rotary joint (10) between the inner arm (4) and the first outer arm (5), an emergency disconnection device (9) between the first outer arm (5) and the second outer arm (6), a third rotary joint (13) between the emergency disconnection device (9) and the first outer arm (5), and the emergency disconnection device (9) separates the conveying pipe (7) into a first conveying pipe (11) and a second conveying pipe (12); The emergency disconnection device (9) includes a first ball valve (91) placed near the output end of the first conveying pipe (11) and a second ball valve (92) placed near the input end of the second conveying pipe (12). Inside the output end of the first conveying pipe (11), there is a jacking block (93). The inside of the jacking block (93) is a hollow structure, and the upper end of the jacking block (93) has a limiting plate (94) that is in limiting fit with the output end of the first conveying pipe (11). The side end of the jacking block (93) has a plurality of equally circumferentially distributed flow holes (95). The edge of the output end of the first conveying pipe (11) extends vertically outwards with a hollow guide column (96). Inside the input end of the second conveying pipe (12), there is a spherical valve core (98) and a spring (99). The inner wall of the second conveying pipe (12) near the input end has a limiting ring (910) that limits the lower end of the hollow guide column (96) and the lower end of the jacking block (93). The outside of the output end of the first conveying pipe (11) has a first flange (911), and the outside of the input end of the second conveying pipe (12) has a second flange (912). The first flange (911) has a plurality of equally circumferentially distributed electromagnets (913), and the second flange (912) has permanent magnets (914) that are attracted to the plurality of electromagnets (913). The emergency disconnection device (9) also includes a control unit electrically connected to the electromagnets (913). In the energized state, the polarity of the electromagnets (913) is the same as the polarity of the permanent magnets (914); The center position of the lower end of the spherical valve core (98) has a vertically arranged nested telescopic column (917). The spring (99) is sleeved on the outer circumference of the nested telescopic column (917). The lower end of the nested telescopic column (917) is fixedly connected to the inner wall of the second conveying pipe (12). When the spherical valve core (98) is forced to compress the spring (99), the nested telescopic column (917) telescopically moves inwards to ensure the perpendicularity of the movement of the spherical valve core (98).

2. The emergency disconnection and unloading arm system for LNG transportation according to claim 1, characterized in that, When the first delivery pipe (11) is connected to the second delivery pipe (12), the lower end of the hollow guide post (96) extends into the second delivery pipe (12) and contacts the limit ring (910). The lower end of the lifting block (93) contacts the limit ring (910), and the flow hole (95) on the lifting block (93) is placed inside the first delivery pipe (11), so as to realize the medium flow between the first delivery pipe (11) and the second delivery pipe (12).

3. The emergency disconnection and unloading arm system for LNG transportation according to claim 2, characterized in that, When the first delivery pipe (11) is separated from the second delivery pipe (12), the hollow guide post (96) on the first delivery pipe (11) is separated from the second delivery pipe (12), and the output end of the first delivery pipe (11) is in limit fit with the limit plate (94) at the upper end of the lifting block (93). At this time, the flow hole (95) on the lifting block (93) is placed at the outer end of the first delivery pipe (11), so as to realize the medium block between the first delivery pipe (11) and the second delivery pipe (12).

4. The emergency disconnection and unloading arm system for LNG transportation according to claim 3, wherein The inner side of the hollow guide post (96) has a first sealing layer (97).

5. The emergency disconnection and unloading arm system for LNG transportation according to claim 4, wherein The inner end of the limit ring (910) has a sealing surface (915) that is in close fit contact with the spherical valve core (98).

6. The emergency disconnection and unloading arm system for LNG transportation according to claim 5, wherein, The limit plate (94) is placed on the lower end surface outside the hollow guide post (96) and has a second sealing layer (916).

7. An emergency disconnection method for an emergency disconnection unloading arm system for LNG transportation using any one of claims 1 to 6, characterized in that The specific steps include: S1. When the LNG unloading arm is working normally, the control unit sends a power-off signal command to the electromagnet (913). After power-off, the electromagnet (913) is magnetically attracted and fixed to the permanent magnet (914). At this time, the hollow guide post (96) of the first delivery pipe (11) is embedded in the second delivery pipe (12), and the lower end of the first delivery pipe (11) is in limit contact with the upper end surface of the limit ring (910) in the second delivery pipe (12). The lifting block (93) in the first delivery pipe (11) is lifted in the first delivery pipe (11) under the limit contact of the limit ring (910), so that the flow hole (95) on the lifting block (93) is placed inside the first delivery pipe (11). When the medium flows in the delivery pipe (7) of the LNG unloading arm, the medium flows into the lifting block (93) through the flow hole (95) of the first delivery pipe (11) and presses the spherical valve core (98) in the second delivery pipe (12), so that the spherical valve core (98) is separated from the limit ring (910), and the medium flows into the second delivery pipe (12), thus realizing the medium flow; S2. When the LNG unloading arm is emergently disengaged, the control unit sends a signal command to energize the electromagnet (913). At this time, the polarity of the energized electromagnet (913) is the same as that of the permanent magnet (914), and the first delivery pipe (11) is quickly separated from the second delivery pipe (12). At this time, the first delivery pipe (11) and the hollow guide column (96) are disengaged from the second delivery pipe (12), and the lifting block (93) in the first delivery pipe (11) moves downward relative to the first delivery pipe (11) under the action of its own gravity and the flow force of the medium in the first delivery pipe (11) until all the through holes (95) on the lifting block (93) are outside the first delivery pipe (11). At this time, the medium flow in the first delivery pipe (11) is blocked; after the emergency disengagement, the remaining medium in the first delivery pipe (11) continues to flow into the second delivery pipe (12) and continues to have a certain thrust on the spherical valve core (98). The remaining medium continues to be output to the second delivery pipe (12). When the medium thrust at the input end of the second delivery pipe (12) is less than the reset elastic force of the spring (99), the spherical valve core (98) moves upward under the elastic force of the spring (99) and is in sealed contact with the limit ring (910). At this time, the medium flow in the second delivery pipe (12) is blocked; S3. While the control unit sends a signal command to energize the electromagnet (913) in step S2, the control unit sends a signal command to close the first ball valve (91) and the second ball valve (92) to block the medium in the first delivery pipe (11) and the second delivery pipe (12).

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