Low-temperature immersed pump for unloading liquid cargo tank for LNG (Liquefied Natural Gas) ship and floating device

Abstract

The invention discloses a low-temperature immersed pump for unloading of a liquid cargo tank for an LNG (Liquefied Natural Gas) ship and a floating device, and relates to the technical field of low-temperature immersed pumps, in particular to the low-temperature immersed pump for unloading of the liquid cargo tank for the LNG ship and the floating device. The device comprises an immersed pump, a pump support, a low-temperature cable, a cable fixing device, a deck, a low-temperature cable deck guide pipe, a cable penetrating connector, a normal-temperature cable and a junction box. A filter is arranged at a suction inlet in the bottom of the immersed pump and is fixedly assembled with a pump tower on the cabin bottom through a pump bracket; the low-temperature cable junction box is fixedly arranged on the immersed pump and is connected with a motor cable and a low-temperature cable; the low-temperature cable penetrates through the low-temperature cable fixing device, the deck and the low-temperature cable deck guide pipe and then is connected with the normal-temperature cable through the cable penetrating connector. And the normal-temperature cable is connected with a junction box fixed on the deck. According to the technical scheme, the problems that in the prior art, an existing LNG pump is poor in cavitation resistance, and the balance capacity cannot meet the ocean swing working condition are solved.

Description

Technical Field

[0001] The invention discloses a cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices, and relates to the technical field of cryogenic submersible pumps, and in particular to a cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices. Background Art

[0002] At present, cryogenic pumps are required to transport cryogenic media in LNG cryogenic medium transport ships and floating devices. Since the medium has the characteristics of low temperature, flammability, explosion and easy vaporization, the pump equipment for transporting such medium is required to have reliable sealing, small medium vaporization volume and safe, stable and reliable structure. This type of pump is difficult to design, manufacture and test. Therefore, at present, this type of vertical cryogenic marine submersible pump in China relies on imports, and there are problems such as expensive products and slow service response. The localization of vertical cryogenic marine submersible pump equipment is conducive to cost control in the LNG transportation link, and is conducive to the application expansion of vertical cryogenic marine submersible pumps in the fields of propane, ethylene and other transport ships, and is conducive to the improvement of the design and manufacturing level of large-scale cryogenic submersible pumps in China. Liquid cargo pumps for LNG ships and floating devices are blank in China.

[0003] The existing LNG pumps have the following problems:

[0004] 1. The existing LNG pump has poor anti-cavitation ability. The present invention designs the impeller and guide shell hydraulics of the large specific speed pump and the high anti-cavitation inducer to achieve the ultra-low suction level capability of the liquid cargo pump

[0005] 2. The balancing capacity of existing LNG pumps cannot meet the requirements of ocean swaying conditions. Under swaying and shaking conditions in the ocean environment, it is necessary to ensure that the axial force of the rotor is completely balanced within a wide operating range. The liquid cargo pump of the present invention is provided with an axial force balancing device, which solves the problem of complete balancing of the axial force under the conditions of overall shaking and tilting of the pump.

[0006] In view of the problems existing in the above-mentioned prior art, it is very necessary to study and design a new type of cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices, so as to overcome the problems existing in the prior art. Summary of the invention

[0007] According to the technical problems of the existing LNG pumps, such as poor anti-cavitation ability and inability to meet the balancing ability of ocean swaying conditions, a low-temperature submersible pump for unloading liquid cargo tanks for LNG ships and floating devices is provided. The present invention mainly solves the above-mentioned existing problems by arranging an axial force balancing device, a high specific speed pump, an impeller, a guide shell hydraulic and a high cavitation resistance inducer in the liquid cargo pump.

[0008] The technical means adopted by the present invention are as follows:

[0009] A cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices comprises: a submersible pump, a pump bracket, a cryogenic cable, a cable fixing device, a deck, a cryogenic cable deck conduit, a cable penetration joint, a normal temperature cable and a junction box;

[0010] Furthermore, a filter is provided at the bottom suction port of the submersible pump and is fixedly assembled with the pump tower on the bilge through a pump bracket;

[0011] Furthermore, a cryogenic cable junction box is fixedly mounted on the submersible pump to connect the motor cable and the cryogenic cable;

[0012] Furthermore, the cryogenic cable is connected to the normal temperature cable through a cable penetration joint after passing through the cryogenic cable fixture, the deck and the cryogenic cable deck conduit;

[0013] Furthermore, the normal temperature cable is connected to a junction box fixed on the deck.

[0014] Furthermore, the submersible pump comprises: a guide shell, an axial force balancing device, a submersible motor, a shaft, a motor housing, and a motor end cover;

[0015] Furthermore, the motor end cover is installed on the upper part of the motor housing, and a liquid outlet channel is arranged inside, and the medium enters the outlet pipe through the liquid outlet channel;

[0016] Furthermore, a bearing housing is arranged inside the motor end cover, and the upper bearing is mounted on the motor housing; a junction box bracket is designed on the side of the motor end cover for installing a low-temperature cable junction box;

[0017] Furthermore, the guide shell is installed at the bottom end of the motor housing;

[0018] Furthermore, the submersible motor is installed in the motor housing, the pump and the motor are coaxial, and the whole is immersed in the low-temperature medium. The medium is insulated and oxygen-free, and the motor does not need to be explosion-proof; the motor is cooled by the low-temperature medium, and there is no need to provide additional heat dissipation for the pump motor, so the cooling effect is better, saving space and cost;

[0019] Furthermore, the shaft is an integrated stepped structure, with both ends mounted on the motor end cover and the guide shell through bearing seats, and the submersible motor is mounted thereon;

[0020] Furthermore, the axial force balancing device is installed at the bottom end of the shaft and fixedly mounted on the guide shell;

[0021] Further, the inducer is mounted on the shaft and is located in front of the axial force balancing device;

[0022] Furthermore, a filter is installed at the bottom of the guide shell.

[0023] Further, the submersible motor comprises: a motor rotor and a motor stator;

[0024] Further, the motor rotor is assembled on the shaft;

[0025] Furthermore, the motor rotor is supported by two-point bearings, which are located at the upper and lower ends of the motor respectively. The bearings are deep groove bearings, which are fixed to the shaft by locking nuts and are lubricated and cooled by low-temperature media during operation.

[0026] Furthermore, the motor stator is assembled in the motor housing.

[0027] Further, the motor housing is composed of an inner motor housing and an outer motor housing;

[0028] Furthermore, a boss is provided on the inner circumference of the lower part of the inner motor housing, and the motor stator is mounted on the boss;

[0029] Further, guide vanes are provided on the outer circumference of the inner motor housing;

[0030] Furthermore, the outer motor housing is installed outside the inner motor housing, and together with the inner motor housing forms a liquid outlet channel.

[0031] Further, the axial force balancing device comprises: a balancing disc and an impeller;

[0032] Furthermore, the impeller is mounted on the shaft, leaving a gap between the impeller and the body ring on the guide shell; due to the structure of the impeller itself, the area of ​​the impeller rear cover is larger than the area of ​​the front cover, and a downward axial force is generated during operation.

[0033] Furthermore, the balancing plate is fixedly mounted on the guide shell;

[0034] Furthermore, the balancing disc adopts a cone-shaped structure, the upper end area is larger than the lower end area, and the balancing disc is located between the impeller rear cover and the guide shell. The function of the balancing disc is to balance the axial force of the impeller by reducing the medium pressure at the impeller rear cover and reducing the thrust generated by the impeller rear cover.

[0035] Furthermore, the inducer is located before the impeller. The inducer is a cylindrical equal pitch structure, which adopts a larger inlet flow area, a smaller inlet angle of attack, and a thinner blade inlet thickness, so that the speed of the medium at the inlet of the inducer is small, the pressure around the inducer blades is uniform, and the medium flowing out of the inducer directly enters the impeller. The impeller is a closed impeller structure, which consists of a front cover plate, middle blades, and a rear cover plate. The submersible pump adopts an impeller without a mouth ring structure to prevent the mouth ring from loosening and falling due to mechanical friction during the operation of the pump. The impeller is installed on the shaft and rotates with the pump shaft. Due to the action of the blades, the medium rotates in the impeller, flows out at a certain speed, and enters the guide shell.

[0036] Furthermore, the guide shell is composed of a shell and guide vanes, and the guide shell is divided into several independent flow channels by the guide vanes. The guide shell collects the liquid flowing out of the impeller and transports it to the liquid outlet channel in the motor shell, converting the velocity energy of the liquid into pressure energy.

[0037] Furthermore, the cryogenic cable junction box is composed of an outer shell and terminal blocks. The connection position between the submersible motor end cable and the cryogenic cable is located inside the cryogenic cable junction box. The cryogenic cable junction box can protect the cable connection position to prevent the impact of the medium in the cabin on the joint.

[0038] Further, the filter is a metal frame structure;

[0039] Furthermore, the circumference and bottom surface of the filter are welded frames, and the surrounding and bottom surface frames are covered with a filter screen, which is a perforated plate. Bolt holes are provided on the upper flange of the filter, and the upper part of the filter is connected to the pump housing by bolts. The liquid enters the pump inlet through the filter orifice plate, enters the impeller flow channel after passing through the inducer, and then enters the guide housing flow channel. After the liquid is discharged from the guide housing, it passes through the liquid outlet flow channels on both sides of the motor housing, flows to the liquid outlet flow channel at the motor end cover, and is discharged from the outlet pipe.

[0040] Furthermore, the electrical penetration joint adopts the gas sealing technology of metal and ceramic welding and metal and glass packaging, which prevents the pumped flammable and explosive medium from leaking along the low-temperature cable to the junction box outside the cabin while transmitting electricity, achieving zero leakage of the medium and making the sealing safer and more reliable, thus improving the safety and reliability of the whole machine operation.

[0041] Furthermore, the submersible pump and the pump tower are connected by a pump bracket, which fixes the submersible pump and the pump tower. The pump bracket mainly includes a pump bracket, a sliding bracket and connecting bolts. An oblong hole is set at the connection. Under low temperature conditions, the pump bracket can slide radially and axially, which solves the problem of different shrinkage amounts of the pump shell and the bracket under low temperature conditions and reduces the stress caused by deformation. The upper support plate of the pump bracket is connected to the pump cover through studs, the lower part of the pump bracket is connected to the pump tower through bolts, the sliding bracket is connected to the lower part of the pump through studs, and the sliding bracket is fixed to the pump bracket through bolts. Through the above connection, the pump and the pump bracket can be firmly fixed on the pump tower.

[0042] Furthermore, in order to prevent the fasteners from loosening or falling off during swinging or surging, the fasteners of the present invention adopt an anti-loosening structure, the connecting fasteners are locked with steel wire locks, and the fasteners are prevented from loosening in pairs instead of being connected in series as a whole. When a steel wire lock breaks, the other fasteners can still be reliably prevented from loosening.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The low-temperature submersible pump for unloading liquid cargo tanks for LNG ships and floating devices provided by the present invention is characterized by a small number of parts, a compact structure, and a short axial distance of the balancing mechanism. By increasing the diameter of the body opening ring and reducing the inner diameter of the balancing disc, the balancing mechanism can be automatically balanced in a wider range. At the same time, the balancing gap between the balancing disc and the body opening ring is small. For every small change in the balancing gap, the medium pressure between the impeller and the balancing disc will change greatly, thereby the force acting on the impeller rear cover plate will change greatly, that is, the sensitivity of the balancing disc is very high. Due to the small balancing gap, the medium leaking from the gap is also small. In the balancing mechanism of the inlet pump, the balancing medium passes through the outlet side filter screen, flows through the intermediate bearing, and then passes through the axial gap formed by the guide shell and the impeller, and finally flows to the outside of the pump. Only the axial gap formed by the guide shell and the impeller is throttled once, so the axial gap is large and the leakage is large.

[0045] 2. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices provided by the present invention has a bearing box structure arranged in the guide shell, which eliminates the independent bearing box body, sets a position for bearing installation in the guide shell, installs a bearing bushing at the bearing installation position, and the bearing is installed on the shaft and installed in the guide shell through the bearing bushing. The guide shell structure integrates the shell, guide vane, and bearing box body into one, has a compact structure, reduces the height of the pump body, reduces the weight of the equipment, and is suitable for the requirements of equipment size and weight in ships.

[0046] 3. The low-temperature submersible pump for unloading liquid cargo tanks for LNG ships and floating devices provided by the present invention can bear the weight of the submersible pump through the filter frame. During temporary storage, transportation, installation, etc., the submersible pump can be supported by the filter frame and placed on a plane without the need for additional supporting tools. The filter mesh of the filter is distributed on the circumference and bottom surface of the filter. The medium can enter the pump through the filter mesh holes. At the same time, the filter mesh can prevent large-sized impurities from entering the pump, which can prevent possible impurities from entering the pump and effectively prevent impurities in the medium from damaging the internal parts of the pump, thereby extending the maintenance cycle of the pump; the filter 11 is a half-structure. After the pump is installed, the filter can be removed without disassembling the pump; there is a support structure in the filter 11, which can serve as a temporary support during the disassembly and assembly of the pump to place the pump upright.

[0047] 4. The present invention provides a low-temperature submersible pump for unloading liquid cargo tanks for LNG ships and floating devices. The submersible motor is installed in the motor housing. The pump and the motor are coaxial and immersed in a low-temperature medium as a whole. The medium is insulated and oxygen-free, and the motor does not need to be explosion-proof. The motor is cooled by the low-temperature medium and there is no need to provide additional heat dissipation for the pump motor. The cooling effect is better, saving space and cost.

[0048] 5. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices provided by the present invention has an integrated structure with no connecting shaft structure in the middle of the shaft, does not require a coupling, has a compact structure, effectively reduces the height of the pump, improves the reliability of the pump operation, and is suitable for installation in a compact space in a cabin.

[0049] Comparison between this case and the existing imported cryogenic submersible pump axial force balance principle:

[0050]

[0051] Comparison between this case and the existing imported low-temperature submersible pump upper bearing seat positioning method:

[0052]

[0053] Comparison between this case and the existing imported low-temperature submersible pump lower bearing seat positioning method:

[0054]

[0055] In summary, the technical solution of the present invention solves the problems in the prior art such as poor anti-cavitation capability of the existing LNG pump and inability of the balancing capability to meet the ocean swaying conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0057] Figure 1 It is a schematic diagram of the structure of the present invention;

[0058] Figure 2 It is a schematic diagram of the structure of the submersible pump of the present invention;

[0059] Figure 3 For the present invention Figure 2 Magnified view of part II;

[0060] Figure 4 This is a schematic diagram of the existing imported pump structure.

[0061] In the figure: 1, bilge 2, submersible pump 3, pump bracket 4, cryogenic cable 5, cable fixing device 6, deck 7, cryogenic cable deck duct 8, cable penetration joint 9, normal temperature cable 10, junction box 11, filter 12, inducer 13, guide shell 14, axial force balancing device 15, motor rotor 16, motor stator 17, shaft 18, inner motor housing 19, outer motor housing 20, motor end cover 21, cryogenic cable junction box 22, balance disk 23, body mouth ring 24, impeller. DETAILED DESCRIPTION

[0062] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0063] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0065] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0066] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0067] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0068] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0069] As shown in the figure, the present invention provides a low-temperature submersible pump for unloading liquid cargo tanks for LNG ships and floating devices, including: a submersible pump 2, a pump bracket 3, a low-temperature cable 4, a cable fixing device 5, a deck 6, a low-temperature cable deck conduit 7, a cable penetration joint 8, a normal temperature cable 9 and a junction box 10; a filter 11 is provided at the bottom suction port of the submersible pump 2, and is fixedly assembled with the pump tower on the bottom of the cabin 1 through the pump bracket 3; the low-temperature cable junction box 21 is fixedly mounted on the submersible pump 2, connecting the motor cable and the low-temperature cable 4; the low-temperature cable 4 passes through the low-temperature cable fixing device 5, the deck 6 and the low-temperature cable deck conduit 7, and is connected to the normal temperature cable 9 through the cable penetration joint 8; the normal temperature cable 9 is connected to the junction box 10 fixed on the deck 6.

[0070] The submersible pump 2 includes: a guide shell 13, an axial force balancing device 14, a submersible motor, a shaft 17, a motor housing, and a motor end cover 20; the motor end cover 20 is installed on the upper part of the motor housing, and a liquid outlet channel is arranged inside, and the medium enters the outlet pipe through the liquid outlet channel; a bearing housing is arranged inside the motor end cover 20, and the upper bearing is installed on the motor housing; a junction box bracket is designed on the side of the motor end cover 20 for installing a low-temperature cable junction box 21; the guide shell 13 is installed at the bottom end of the motor housing; the submersible motor is installed in the motor housing, the pump and the motor are coaxial, and the whole is immersed in the low-temperature medium; the shaft 17 is an integrated stepped structure, and both ends are installed on the motor end cover 20 and the guide shell 13 through bearing seats, and the submersible motor is assembled thereon; the axial force balancing device 14 is installed at the bottom end of the shaft 17 and fixedly mounted on the guide shell 13; the inducer 12 is installed on the shaft 17 and is located in front of the axial force balancing device 14; the filter 11 is assembled at the bottom of the guide shell 13.

[0071] The submersible motor includes: a motor rotor 15 and a motor stator 16; the motor rotor 15 is assembled on the shaft 17; the motor rotor 15 is supported by two-point bearings, which are respectively located at the upper and lower ends of the motor, and the bearings are deep groove bearings, which are fixed to the shaft by locking nuts and are lubricated and cooled by low-temperature media during operation; the motor stator 16 is assembled in the motor housing.

[0072] The motor housing is composed of an inner motor housing 18 and an outer motor housing 19; a boss is arranged on the lower inner circumference of the inner motor housing 18, and the motor stator 16 is mounted on the boss; guide vanes are arranged on the outer circumference of the inner motor housing 18; the outer motor housing 19 is installed on the outside of the inner motor housing 18, and together with the inner motor housing 18, forms a liquid outlet channel.

[0073] The axial force balancing device 14 includes: a balancing disc 22 and an impeller 24; the impeller 24 is mounted on the shaft 17, and a gap is left between the impeller 24 and the body ring 23 on the guide shell 13; the balancing disc 22 is fixedly mounted on the guide shell 13; the balancing disc 22 adopts a conical structure, the upper end area is larger than the lower end area, and the balancing disc 22 is located between the rear cover plate of the impeller 24 and the guide shell 13.

[0074] Inducer 12 is located before impeller 24 .

[0075] The cryogenic cable junction box 21 is composed of an outer shell and wiring terminals. The wiring position of the submersible motor end cable and the cryogenic cable 4 is located inside the cryogenic cable junction box 21. The cryogenic cable junction box 21 can protect the cable wiring position to prevent the impact of the medium in the cabin on the joint.

[0076] The filter 11 is a metal frame structure; the circumference and bottom surface of the filter 11 are welded frames, and the surrounding and bottom frames are covered with a filter screen, which is a perforated plate.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices, characterized in that: The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices comprises: a submersible pump (2), a pump bracket (3), a cryogenic cable (4), a cable fixing device (5), a deck (6), a cryogenic cable deck conduit (7), a cable penetration joint (8), a normal temperature cable (9) and a junction box (10); A filter (11) is provided at the bottom suction port of the submersible pump (2), and is fixedly assembled with the pump tower on the bilge (1) via a pump bracket (3); The cryogenic cable junction box (21) is fixedly mounted on the submersible pump (2) and connects the motor cable and the cryogenic cable (4); The low-temperature cable (4) passes through the low-temperature cable fixing device (5), the deck (6) and the low-temperature cable deck conduit (7) and is connected to the normal temperature cable (9) through the cable penetration joint (8); The normal temperature cable (9) is connected to a junction box (10) fixed on the deck (6).

2. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to claim 1, characterized in that: The submersible pump (2) comprises: a guide shell (13), an axial force balancing device (14), a submersible motor, a shaft (17), a motor housing, and a motor end cover (20); The motor end cover (20) is installed on the upper part of the motor housing, and a liquid outlet channel is arranged inside, and the medium enters the outlet pipe through the liquid outlet channel; A bearing housing is arranged inside the motor end cover (20), and an upper bearing is mounted on the motor housing; a junction box bracket is designed on the side of the motor end cover (20) for mounting a low-temperature cable junction box (21); The guide shell (13) is installed at the bottom end of the motor housing; The submersible motor is installed in the motor housing, the pump and the motor are coaxial, and the whole is immersed in the low-temperature medium; The shaft (17) is an integrated stepped structure, with both ends mounted on the motor end cover (20) and the guide shell (13) through bearing seats, and the submersible motor is mounted thereon; The axial force balancing device (14) is mounted on the bottom end of the shaft (17) and fixedly mounted on the guide housing (13); The induction wheel (12) is mounted on the shaft (17) and is located in front of the axial force balancing device (14); The bottom of the guide shell (13) is equipped with a filter (11).

3. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to claim 2, characterized in that: The submersible motor comprises: a motor rotor (15) and a motor stator (16); The motor rotor (15) is assembled on the shaft (17); The motor rotor (15) is supported by two-point bearings, which are respectively located at the upper and lower ends of the motor. The bearings are deep groove bearings, which are fixed to the shaft by locking nuts and are lubricated and cooled by low-temperature medium during operation. The motor stator (16) is assembled in the motor housing.

4. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to claim 2, characterized in that: The motor housing is composed of an inner motor housing (18) and an outer motor housing (19); A boss is provided on the inner circumference of the lower part of the inner motor housing (18), and a motor stator (16) is mounted on the boss; Guide vanes are arranged on the outer circumference of the inner motor housing (18); The outer motor housing (19) is installed outside the inner motor housing (18) and together with the inner motor housing (18) forms a liquid outlet channel.

5. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to claim 2, characterized in that: The axial force balancing device (14) comprises: a balancing disc (22) and an impeller (24); The impeller (24) is mounted on the shaft (17) and a gap is left between the impeller and the body opening ring (23) on the guide shell (13); The balancing plate (22) is fixedly mounted on the guide shell (13); The balancing disc (22) adopts a cone-shaped structure, the upper end area is larger than the lower end area, and the balancing disc (22) is located between the rear cover plate of the impeller (24) and the guide shell (13).

6. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to claim 2, characterized in that: The inducer (12) is located before the impeller (24).

7. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to any one of claim 1, characterized in that: The cryogenic cable junction box (21) is composed of a shell and wiring terminals. The wiring position of the submersible motor end cable and the cryogenic cable (4) is located inside the cryogenic cable junction box (21). The cryogenic cable junction box (21) can protect the cable wiring position to prevent the impact of the medium in the cabin on the joint.

8. The cryogenic submersible pump for unloading liquid cargo tanks for LNG ships and floating devices according to any one of claim 1, characterized in that: The filter (11) is a metal frame structure; The circumference and bottom surface of the filter (11) are welded frames, and the surrounding and bottom frames are covered with a filter screen, which is a perforated plate.

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