Liquid lifting device of low-temperature tank

Abstract

To provide a liquid lifting device of a low-temperature tank capable of synergistically increasing a closing force of a foot valve with a simple structure and reliably preventing infiltration of storage liquid into a pump column when a submerged pump housed in the pump column is pulled out for maintenance.SOLUTION: A liquid lifting device of a low-temperature tank opens a foot valve 6 downward with a weight of a submerged pump 4 when the submerged pump 4 is lowered, and closes the foot valve 6 with the force of a spring 27 when the submerged pump 4 is raised. In the liquid lifting device, when the submerged pump 4 stored in a pump column 5 is pulled out for maintenance, pressurized fluid 29 is supplied to bellows 34 of a closing force applying mechanism 30 by a pressurizing pipe 38 while the foot valve 6 is closed with the force of the spring 27, thereby applying a further force in a direction of closing the foot valve 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquid lifting device used for a cryogenic tank.

Background Art

[0002] A cryogenic tank for storing cryogenic liquids such as ammonia is incorporated with a liquid lifting device for discharging the stored liquid.

[0003] This type of liquid lifting device generally includes a cylindrical pump column having openings above the roof portion and near the bottom of the cryogenic tank, and a submerged pump for discharging the stored liquid in the cryogenic tank housed in the pump column. A lift cable and a support cable connected to a hoisting device such as a hoist installed above the pump column are connected to the submerged pump in the pump column. And, the submerged pump can be raised and lowered as desired within the pump column via the lift cable and the support cable.

[0004] In addition, a foot valve that opens and closes by the raising and lowering of the submerged pump is provided at the lower part of the pump column, and a foot valve adapter portion that supports the foot valve in an operable state of opening and closing is connected. When installing the submerged pump, the lift cable and the support cable are lowered, and when the submerged pump is lowered to the seating portion in the foot valve adapter portion, the tip of the submerged pump is placed on the upper part of the foot valve, and the foot valve opens against the force of the spring above the foot valve by its load (weight). As a result, the liquid suction port at the lower part of the foot valve adapter portion is opened, and the stored liquid flows into the pump column, enabling liquid lifting by the submerged pump.

[0005] When pulling out the submerged pump from the pump column for maintenance, the work is performed, for example, in the following manner. First, in order to prevent the vaporized gas of the stored liquid remaining in the pump column from leaking outside the tank, with the liquid suction port into the pump column closed by a foot valve, the inside of the pump column is purged with a pressurized fluid such as N2 gas. The purge with N2 gas is carried out by enclosing N2 gas in the pump column through a purge pipe connected to the pump column, and by forcibly opening the foot valve with the pressure of the N2 gas, the stored liquid remaining in the pump column is discharged into the cryogenic tank.

[0006] Then, when the pump column is filled with N2 gas and a state is observed where the sound of N2 gas being discharged from the foot valve into the cryogenic tank is heard, the enclosure of N2 gas is stopped and the pressure inside the pump column is released.

[0007] Next, remove the head plate that closes the upper opening of the pump column, disconnect the lift cable suspended from the head plate, connect it to a hoisting device such as a hoist, and operate the hoisting device to pull out the submerged pump suspended from the lift cable from inside the pump column. When performing maintenance on the submerged pump, it is carried out in a state where the inside of the pump column is purged with N2 gas so that the vaporized gas of the stored liquid in the tank does not leak outside the cryogenic tank. In particular, when the cryogenic tank stores ammonia, since ammonia is lighter than air, flammable and toxic, care must be taken not to leak vaporized gas outside the tank during maintenance.

[0008] In this way, the maintenance of the submerged pump is carried out with the liquid suction port of the foot valve adapter part attached to the lower part of the pump column closed by the foot valve. However, if the liquid suction port is not completely closed by the foot valve, the stored liquid in the cryogenic tank will enter the pump column through the gap between the lower end surface of the foot valve adapter part and the upper end surface of the foot valve, and when the head plate is opened, the vaporized gas of the stored liquid that has entered the pump column will leak outside the cryogenic tank.

[0009] Therefore, conventionally, with regard to the closing mechanism of the foot valve during maintenance of a submerged pump, a plurality of prior arts for preventing leakage of vapor gas have been proposed.

[0010] For example, in the first prior art (see Patent Document 1), a fixed plate 9 is fixed by bolts 10 at a distance below the lower opening 7 of a conduit 2 (pump column) inserted into a storage tank 1, and a bellows 11 is fixed at the center of this fixed plate 9. And a bowl-shaped shut-off valve 8 (foot valve) that closes the opening 7 of the conduit 2 is fixed to the free end of this bellows 11. When liquefied gas is press-fitted into the bellows 11 through a thin tube 12 from outside the conduit 2, the bellows 11 extends and presses the shut-off valve 8 against the lower opening 7 at the lower end of the conduit 2.

[0011] Also, similarly in the second prior art (see Patent Document 2), when pulling up the pump 6 from inside the liquid storage tank A during maintenance, it has a structure that closes the opening 5 using a bellows 12. That is, a movable plate 11 (foot valve) for sealing the opening 5 is provided on the lower end wall 4 of the casing 3. When the liquefied gas in the bellows 12 connected to the movable plate 11 is pressurized by a pressurized fluid, the movable plate 11 is pushed up to seal the opening 5.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0013] All of the above-mentioned prior arts attempt to close the foot valve (shut-off valve 8, movable plate 11) with the extension force of the bellows. However, these are merely replacements of the mechanism that had been closing the foot valve solely with the spring force up to that point with another mechanism, and do not multiplicatively increase the closing force of the foot valve. Further, when replacing the mechanism, these prior arts require large-scale modifications such as adopting a structure in which the valve body (shut-off valve 8, movable plate 11) and the bellows are integrated, or involving new structural changes to the submerged pump device itself. Therefore, there is a problem that the hurdle for practical implementation is extremely high.

[0014] Therefore, the present invention provides a liquid lifting device for a cryogenic tank that can multiplicatively increase the closing force of the foot valve with a simple structure and reliably prevent the inflow of the stored liquid into the pump column.

Means for Solving the Problems

[0015] To achieve the above object, the present invention adopts the following configuration. The liquid lifting device for a cryogenic tank of the present invention includes a cylindrical pump column erected through the roof portion of the cryogenic tank, a head plate closing the upper opening of the pump column, a submerged pump accommodated in the pump column so as to be able to ascend and descend, a foot valve disposed between the submerged pump and the inner shell bottom of the cryogenic tank and opened and closed by the ascent and descent of the submerged pump, a foot valve adapter portion connected to the lower portion of the pump column, supporting the foot valve in an operable state of opening and closing, and capable of contacting the foot valve at the lower edge portion, a valve opening and closing mechanism provided in the foot valve adapter portion, closing the foot valve with an urging force when the submerged pump ascends, and opening the foot valve by receiving the weight of the submerged pump against the urging force when descending, a closing force applying mechanism installed on the inner shell bottom of the cryogenic tank, adding a force in the direction of closing the foot valve by supplying pressurized fluid from the outside to the urging force of the valve opening and closing mechanism, and a pressurizing pipe for supplying pressurized fluid to the closing force applying mechanism. With the foot valve closed by the urging force of the valve opening and closing mechanism, pressurized fluid is supplied to the closing force applying mechanism through the pressurizing pipe to further apply a force in the direction of closing the foot valve.

[0016] With such a configuration, according to the present invention, not only is the mechanism that closes the foot valve simply by the force of the valve opening and closing mechanism replaced with a mechanism that closes with a closing force applying mechanism, but also the closing force of the foot valve can be surely increased by the synergistic effect of the force of the valve opening and closing mechanism connected to the foot valve and the fluid pressure. In addition, without particularly modifying the structure in which the foot valve is attached to the lower part of the existing pump column via the foot valve adapter part, the closing force applying mechanism is placed on the bottom of the inner shell below the foot valve, and it can be realized by a simple structure in which only a pressurizing pipe is connected thereto. Therefore, it is useful in that it can be easily installed and introduced into the existing cryogenic tank.

[0017] In addition, the present invention can adopt several preferred configurations as follows. That is, the closing force applying mechanism has a lower contact plate placed on the bottom of the inner shell, a bellow placed on the lower contact plate, an upper contact plate placed on the bellow, and a guide pipe fixed to the upper part of the lower contact plate and slidably disposed in a fitting hole provided in the upper contact plate. The pressurizing pipe is connected to the bellow, and by supplying pressurized fluid into the bellow, as the bellow expands, the upper contact plate is raised, and further force is applied in the direction of closing the foot valve. With such a configuration, when the bellow expands, the upper contact plate is guided by the guide pipe and can surely and efficiently apply force in the direction of closing the foot valve, and the closing force can be increased more synergistically.

[0018] Alternatively, the closing force applying mechanism has a lower contact plate placed on the bottom of the inner shell, an airbag placed on the lower contact plate, an upper contact plate placed on the airbag, and a guide pipe fixed to the upper part of the lower contact plate and slidably disposed in a fitting hole provided in the upper contact plate. The pressurizing pipe is connected to the airbag, and by supplying pressurized fluid into the airbag, as the airbag expands, the upper contact plate is raised, and further force can also be applied in the direction of closing the foot valve. With such a configuration, when the airbag inflates, the upper contact plate can be guided by the guide pipe and apply a force in a direction to reliably and efficiently close the foot valve, and the closing force can be enhanced more synergistically.

[0019] Further, the closing force applying mechanism includes a substrate placed on the bottom of the inner shell, an airbag placed on the substrate, and a frame provided on the substrate and surrounding the airbag with legs provided at the four corners. The frame has an opening through which a part of the foot valve adapter portion and the foot valve can be inserted when the foot valve is opened downward. The pressurizing pipe is connected to the airbag, and by supplying a pressurized fluid into the airbag to inflate the airbag, a further force may be applied in a direction to close the foot valve. With such a configuration, even if an upper contact plate, a guide pipe, etc. are not provided between the foot valve and the airbag, since the foot valve in an inserted state is correctly positioned within the opening of the frame, by inflating the airbag surrounded by the legs of the frame there, a force can be applied in a direction to reliably and efficiently close the foot valve, and the closing force can be enhanced more synergistically.

[0020] In the present invention, the pressurized fluid supplied by the pressurizing pipe is preferably the same type of fluid as the pressurized fluid for purging inside the pump column. In this case, without adding a separate new fluid supply facility, by also using the existing purge fluid supply facility for the operation of the closing force applying mechanism (diverting) in the lift liquid devices of many low-temperature tanks, the present invention can be easily installed and introduced.

Advantages of the Invention

[0021] As described above, according to the present invention, it is possible to provide a lift liquid device for a low-temperature tank that has a simple structure, synergistically enhances the closing force of the foot valve, and can reliably prevent the inflow of the stored liquid into the pump column.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a preferred example of the liquid lifting device applied to the cryogenic tank is given, but the form of the present invention is not limited to the example. Of course, the present invention can be modified by omitting or adding the following components, or changing the embodiments such as the shape of the components without departing from the gist of the invention. The figures show an outline, and only a part is drawn and the detailed structure is omitted. Even with these schematic illustrations, those skilled in the art can fully implement the present invention by referring to the disclosure of the embodiments.

[0024] Figure 1 is a longitudinal sectional view of a low-temperature tank 1 to which a liquid lifting device according to an embodiment is applied. First, the overall configuration of the low-temperature tank 1 will be described.

[0025] 〔Overall configuration of the low-temperature tank〕 The low-temperature tank 1 has an inner shell 2 that forms an inner tank for storing a storage liquid 9, an outer shell 3 that surrounds the inner shell 2 with a gap therebetween to form an outer tank, and a heat insulating material 11 in the space between the inner shell 2 and the outer shell 3. As shown in Figure 1, the low-temperature tank 1 has an inner shell bottom 2a provided via a bottom heat insulating material 11a such as perlite concrete on a concrete foundation 12, an inner shell side portion 2b erected on the inner shell bottom 2a, and an inner shell roof portion 2c provided on the inner shell side portion 2b. The outer shell bottom 3a is laid on the foundation 12. On the outer shell bottom 3a outside the bottom heat insulating material 11a, a PC outer shell side portion 3b serving as a liquid retaining dike is erected, and an outer shell roof portion 3c is provided on the outer shell side portion 3b. A seal metal 3d is attached to the inner peripheral surface of the outer shell side portion 3b, and the peripheral edge of the outer shell roof portion 3c is fixed to the upper end portion of the outer shell side portion 3b. Further, a side heat insulating material 11b is filled between the inner shell side portion 2b and the outer shell side portion 3b. Furthermore, a roof heat insulating material 11c is filled between the inner shell roof portion 2c and the outer shell roof portion 3c. The roof shapes of the inner shell roof portion 2c and the outer shell roof portion 3c can both adopt hemispherical or truncated spherical roofs. Note that the low-temperature tank 1 can have not only a flat-bottomed cylindrical shape as shown in Figure 1, but also shapes such as a vertically placed cylindrical shape, a horizontally placed cylindrical shape, and a spherical shape.

[0026] The storage liquid 9 stored in the low-temperature tank 1 is, for example, liquid ammonia, liquid hydrogen, etc. For each member such as the inner shell 2 and the outer shell 3 constituting the low-temperature tank 1, a material resistant to the storage liquid 9 stored in the low-temperature tank 1 can be used. For example, steel materials for low-temperature pressure vessels, or stainless steel materials, aluminum alloys, etc.

[0027] 〔Configuration of the liquid lifting device〕 Next, the configuration of the liquid lifting device will be described. The liquid lifting device of the low-temperature tank 1 includes a cylindrical pump column 5 standing upright through the inner shell roof part 2c and the outer shell roof part 3c, a head plate 8 closing the upper opening 5a of the pump column 5, a submerged pump 4 connected to the head plate 8 via a support cable 7 and housed in the pump column 5 so as to be able to ascend and descend, a foot valve 6 located between the submerged pump 4 and the inner shell bottom 2a of the low-temperature tank 1 and opened and closed by the ascent and descent of the submerged pump 4, and a foot valve adapter part 17 connected to the lower part of the pump column 5, supporting the foot valve 6 in a state where it can be opened and closed, and capable of contacting the foot valve 6 at the lower edge part.

[0028] 〔Valve opening and closing mechanism〕 Here, a valve opening and closing mechanism 15 is provided in the foot valve adapter part 17. In this valve opening and closing mechanism 15, a plurality of fitting holes 20b (not shown in FIG. 1) penetrate vertically through the lower flange part 20 (not shown in FIG. 1) of the foot valve adapter part 17. In these fitting holes 20b, rod-shaped members 16c (none of which are shown in FIG. 1) between the first end 16a and the second end 16b of the shaft member 16 are slidably arranged. The shaft member 16 has the first end 16a widened into a piston shape, and the foot valve 6 is connected to the opposite second end 16b. And between the upper part of the lower flange part 20 of the foot valve adapter part 17 and the first end 16a of the shaft member 16, a spring 27 that generates a biasing force in a direction (here, upward) to separate the first end 16a from the lower flange part 20 is provided. The valve opening and closing mechanism 15 is a mechanism that, when the submerged pump 4 is lowered, the foot valve 6 is opened downward by the weight of the submerged pump 4 against the biasing force of the spring 27, and when the submerged pump 4 is lifted upward, the foot valve 6 is closed by the biasing force of the spring 27. FIG. 1 shows a state where the foot valve 6 is closed. Note that the upper flange 23 of the pump column 5 and the head plate 8 are fastened by a plurality of flange mounting bolts 21 and a plurality of flange mounting nuts 22.

[0029] In addition, the liquid lifting device of the low-temperature tank 1 includes a closing force applying mechanism 30 placed on the bottom 2a of the inner shell and located below the foot valve 6, a purge pipe 26 connected to the pump column 5 for introducing pressurized fluid into the pump column 5 to push back the stored liquid 9 into the low-temperature tank 1 for purging, and a pressurizing pipe 38 connected to the closing force applying mechanism 30 for supplying pressurized fluid 29 to the bellows 34 of the closing force applying mechanism 30. In this embodiment, the pressurized fluid 29 supplied by the pressurizing pipe 38 and the purge pipe 26 can be common N2 gas to each other.

[0030] The submerged pump 4 is connected to a support cable 7 lowered from a head plate 8 that liquid-tightly closes the upper opening 5a of the pump column 5. When the submerged pump 4 is raised and lowered within the pump column 5, the submerged pump 4 is suspended and supported via the support cable 7. Also, a lift shaft 28 is disposed through the head plate 8. The lift shaft 28 is raised and lowered together when the submerged pump 4 is raised and lowered, and supports the submerged pump 4 via the support cable 7. A connecting member 28a for connecting a cable (not shown) from a hoisting device (not shown) such as a hoist is provided at the upper part of the lift shaft 28. The support cable 7 suspends and supports the submerged pump 4 when the submerged pump 4 is raised and lowered within the pump column 5. The support cable 7 is composed of, for example, a metal wire or the like. The support cable 7 is connected to the lift shaft 28 and a connecting member 4b at the upper part of the submerged pump 4.

[0031] FIG. 2 is a diagram showing the detailed structures of the submerged pump 4 and the foot valve 6 that constitute the liquid lifting device of the low-temperature tank 1 according to an embodiment. (a) in FIG. 2 shows the state when the foot valve is open, and (b) in FIG. 2 shows the state when the foot valve is closed, respectively. A protrusion 25 is formed on the upper end surface 6a of the foot valve 6. When the submersible pump 4 is pushed down to the bottom, the tip 4a of the submersible pump 4 contacts the upper surface 25a of the protrusion 25 of the foot valve 6. At this time, the weight of the submersible pump 4 applied to the foot valve 6 can push down and open the foot valve 6 against the biasing force of the spring 27. As a result, a gap is formed between the upper end surface 6a of the foot valve 6 and the lower end surface 20a of the lower flange portion 20 of the foot valve adapter portion 17. In this state, when the storage liquid 9 in the low-temperature tank 1 is sucked into the pump column 5 from the lower opening 17b of the foot valve adapter portion 17 and the submersible pump 4 in the low-temperature tank 1 is driven, the storage liquid 9 sucked into the pump column 5 is pushed up to the top in the pump column 5 by the submersible pump 4 and drained from the discharge pipe 10 at the upper part of the pump column 5.

[0032] The foot valve adapter portion 17 connected to the lower part of the pump column 5 is composed of an upper flange portion 18, a cylindrical body portion 19, and a lower flange portion 20. The lower flange 24 of the pump column 5 and the upper flange portion 18 of the foot valve adapter portion 17 are fastened by a plurality of flange mounting bolts 21 and a plurality of flange mounting nuts 22. Note that the lower opening 17b of the foot valve adapter portion 17 serves as a liquid suction port for the storage liquid 9 into the pump column 5 when the foot valve 6 is open.

[0033] 〔Closing force applying mechanism〕 Here, in this embodiment, a closing force applying mechanism 30 for improving the closing force of the foot valve 6 is provided between the foot valve 6 and the inner shell bottom 2a. This closing force applying mechanism 30 can be detachably retrofitted, for example, between an existing foot valve 6 and the inner shell bottom 2a, or can be newly installed as a set with the pump column 5 including the submersible pump 4 and the equipment set of the foot valve 6.

[0034] In any case, the closing force applying mechanism 30 for improving the closing force of the foot valve 6 is composed of an upper contact plate 31, a lower contact plate 32, a guide pipe 33, and a bellows 34 (or an airbag 35). The lower contact plate 32 is fixed to the upper surface of the inner shell bottom 2a, and the lower ends of a plurality of guide pipes 33 are fixed to the upper surface of the lower contact plate 32. A plurality of fitting holes 31a (not shown in FIG. 2) are formed in the upper contact plate 31 at positions corresponding to the arrangement of the plurality of guide pipes 33, and the guide pipes 33 are slidably fitted into the respective fitting holes 31a. A pressurizing pipe 38 is connected to the bellows 34 (or the airbag 35), and it can be extended (or inflated) by supplying a pressurizing fluid 29 (hereinafter, N2 gas 29). In order to hold the position of the bellows 34, it is preferable that the bellows 34 is fixed to both the upper contact plate 31 and the lower contact plate 32. Also, the lower contact plate 32 can be eliminated, the lower end of the bellows 34 (or the airbag 35) can be fixed on the inner shell bottom 2a, and the lower end of the guide pipe 33 can be directly fixed on the inner shell bottom 2a.

[0035] 〔Opening and closing mechanism of foot valve〕 In FIG. 2(a), the submerged pump 4 is lowered by suspending the support cable 7 in the pump column 5, and the foot valve 6 is opened by the self-weight of the submerged pump 4. At this time, N2 gas 29 is not supplied to the bellows 34, the bellows 34 is contracted, and no force from the closing force applying mechanism 30 is applied to the foot valve 6. The strength (biasing force) of the spring 27 is adjusted to such an extent that the foot valve 6 is opened by the self-weight of the submerged pump 4. In FIG. 2(b), the submerged pump 4 is lifted by lifting the support cable 7, and the foot valve 6 is closed by the biasing force of the spring 27. At this time, by supplying N2 gas 29 from the pressurizing pipe 38 to the bellows 34, the bellows 34 extends, and accordingly, the upper contact plate 31 above the bellows 34 rises, applying an additional force in the direction of closing the foot valve 6. Here, the outer diameter of the foot valve 6 can vary greatly depending on, for example, the operating conditions of the liquid lifting device. Therefore, for example, when the outer diameter of the foot valve 6 becomes relatively large, a correspondingly large-sized bellows 34 (or airbag 35) is required, and if necessary, the number of pressurizing pipes 38 connected to the bellows 34 (or airbag 35) is increased so as to obtain the pressure required to expand it. A valve 38a (not shown in FIG. 2) for adjusting the supply and stop of the N2 gas 29 to the pressurizing pipe 38 can be provided in the N2 gas supply line.

[0036] Hereinafter, the closing force applying mechanism 30 used in the present embodiment will be further described with reference to a plurality of cases. 〔First case〕 FIG. 3 is a diagram showing a first case of the closing force applying mechanism 30 (a device composed of a single bellows 34). As shown in FIG. 3(a), when the foot valve 6 is open, the spring 27 is contracted by the weight of the submersed pump 4. At this time, the N2 gas 29 is not supplied to the bellows 34, and the bellows 34 is in a contracted state. As shown in FIG. 3(b), when the foot valve 6 is closed, the foot valve 6 is in a closed state by the restoring force (biasing force) of the spring 27. At this time, the N2 gas 29 is supplied to the bellows 34 to such an extent that the upper contact plate 31 does not contact the foot valve 6, so that the bellows 34 is in a state of being extended to a certain extent, or the N2 gas 29 is not supplied to the bellows 34 and the bellows 34 is in a contracted state. Next, as shown in FIG. 3(c), before the N2 gas purge in the pump column 5 is completed and before the head plate 8 is removed and the pump column 5 is opened (hereinafter referred to as time shut), the N2 gas 29 is supplied to the bellows 34 to extend the bellows 34, so that the upper contact plate 31 above the bellows 34 rises. The rising upper contact plate 31 pushes up the foot valve 6 upward, so that a further force can be applied in the direction of closing the foot valve 6.

[0037] In addition, in this embodiment, the height between the upper surface of the bottom 2a of the inner shell and the lower surface of the foot valve 6 when the foot valve 6 is open (when storing liquid is inhaled) is, for example, about 80 to 100 mm during normal times as an example to surely prevent contact between the foot valve 6 and the bottom 2a of the inner shell, but it is not particularly limited to this. When a closing force applying mechanism 30 is provided below the foot valve 6 as in this embodiment, in order to surely prevent contact between the foot valve 6 and the upper contact plate 31 when the foot valve 6 is open, it is necessary to secure a height H1 of about 80 to 100 mm from the upper surface of the upper contact plate 31 to the lower surface of the foot valve 6. Therefore, by selecting the bellows 34 having the smallest possible length during contraction, the lower opening 17b can be brought closer to the bottom 2a of the inner shell while ensuring a sufficient length of the height H1 when the bellows 34 contracts, so that the dead stock can be reduced accordingly. The dead stock here refers to the stored liquid 9 that is not discharged from the cryogenic tank 1 by being stored below the lower end surface 20a of the lower flange portion 20.

[0038] Therefore, when reducing the dead stock of the storage capacity when the submerged pump 4 sucks the stored liquid 9 when the foot valve 6 in FIG. 3(a) is open, the length of the bellows 34 when contracting when the foot valve 6 in FIG. 3(a) is open shall be selected to match the required level of the dead stock of the cryogenic tank 1. In addition, by providing, for example, a recess (not shown) in the upper contact plate 31 or the lower contact plate 32 that can accommodate a part of the bellows 34, the dead stock can be reduced compared to the case where no recess is provided. Note that the material of the bellows 34 is a metal such as stainless steel or a resin that has excellent cryogenic resistance and can maintain flexibility in a cryogenic environment.

[0039] So far, the first case of the closing force applying mechanism 30 has been described with reference to FIGS. 3(a) to 3(c). Hereinafter, FIGS. 4 to 10 will be further added to explain the second to fourth cases of the closing force applying mechanism 30, and further, the closing force applying mechanism 40 as the fifth and sixth cases. In the following description, the basic principles in FIGS. 4 (second case), 6 (third case), 7 (fourth case), 9 (fifth case) and 10 (sixth case), (a) to (c) are common to the case of FIG. 3. Therefore, in the following, the description will focus on the differences from the previous cases, and the description of the overlapping configurations and operating principles in each case will be omitted unless particularly necessary.

[0040] 〔Second case〕 FIG. 4 is a diagram showing a second case of the closing force applying mechanism 30 (a device composed of a plurality of bellows 36). Here, it is different from the first case in that it is composed of a plurality of bellows 36 instead of a single bellows 34. In addition, a pressure pipe 38 is connected to each bellows 36, and by supplying N2 gas 29 to each bellows 36, the plurality of bellows 36 can be evenly extended (FIG. 4(c)). With such a structure, the surface contact between the lower end surface 20a of the lower flange portion 20 and the upper end surface 6a of the foot valve 6 can be made uniform to eliminate the gap, and the inflow of the stored liquid 9 into the pump column 5 can be completely prevented.

[0041] FIG. 5 is a plan sectional view of the closing force applying mechanism 30 of FIG. 4 (X-X sectional view of FIG. 4(c)). As shown in FIG. 5, a plurality of bellows 36 are provided on the lower retaining plate 32 and arranged at equal intervals on the concentric circumferences of the center and the outer edge of the foot valve 6 in plan view, so that the surface contact between the lower end surface 20a of the lower flange portion 20 and the upper end surface 6a of the foot valve 6 can be surely made uniform. Also, the number and arrangement of the plurality of bellows 36 shall be appropriately adjusted according to the outer diameter of the foot valve 6.

[0042] 〔Third case〕 FIG. 6 is a diagram showing a third example of the closing force applying mechanism 30 (an apparatus composed of a single airbag 35). Here, it is different from the first and second examples in that it is composed of a single airbag 35 instead of bellows 34, 36. A pressurizing pipe 38 is connected to the airbag 35, and by supplying N2 gas 29 from the pressurizing pipe 38, the airbag 35 can be inflated (FIG. 6(c)). In addition, by providing recesses (not shown) in the upper contact plate 31 and the lower contact plate 32 that can accommodate a part of the airbag 35, dead stock can be reduced as compared with the case where no recess is provided. Note that the airbag 35 should be made of a material having elasticity and flexibility and should have airtightness. For example, various vulcanized rubbers, thermoplastic elastomers, soft plastics, and various fibers can be used. Note that aromatic polyamide coated with a fluorine-based resin or a silicone-based resin is flexible even at extremely low temperatures.

[0043] 〔Fourth Example〕 FIG. 7 shows a fourth example of the closing force applying mechanism 30 (an apparatus composed of a plurality of airbags 37). Here, it is different from the third example in that it is composed of a plurality of airbags 37 instead of a single airbag 35. Pressurizing pipes 38 are connected to the plurality of airbags 37, and by supplying N2 gas 29 to each of them, the plurality of airbags 37 can be inflated (FIG. 7(c)). As a mode of connecting the pressurizing pipes 38 to the plurality of airbags 37 (supplying N2 gas 29), for example, each airbag 37 may be connected in communication by an air supply pipe 39, or a pressurizing pipe 38 branched to each airbag 37 may be connected. Also, the material of the airbag 37 and the like is the same as that in the third example.

[0044] 〔Fifth Example〕 FIG. 8 is a perspective view showing a fifth example of the closing force applying mechanism 40 (an apparatus composed of a frame body 43 and a single airbag 41). Since the fifth example has a basic configuration different from the conventional closing force applying mechanisms 30 (the first to fourth examples), it is designated as the closing force applying mechanism 40 for distinction. That is, the closing force applying mechanism 40 as the fifth example includes a substrate 44 placed on the inner shell bottom 2a, an airbag 41 placed on the substrate 44, and a frame body 43 surrounding the airbag 41 with legs provided at the four corners. The substrate 44 is provided with a mortar-shaped recess 45 (not shown in FIG. 8) that abuts against the inflated portion of the airbag 41. The substrate 44 is fixed to the upper surface of the inner shell bottom 2a. In addition, an opening 46 is provided in the upper part of the frame body 43. The size of the opening 46 is such that the lower part of the foot valve adapter portion 17 and the foot valve 6 do not contact the frame body 43 and can be fully inserted. Therefore, regardless of the thickness of the upper part of the frame body 43 or the height of the internal space of the frame body 43 formed between the frame body 43 and the substrate 44, the foot valve 6 can be pushed down through the opening 46 to a position between the legs of the frame body 43, that is, near the inner shell bottom 2a of the low-temperature tank 1. By opening the foot valve 6 at this position, the stored liquid 9 stored near the inner shell bottom 2a (very close) can also be sucked, thereby enabling a structure that minimizes dead stock. The lower end portions of the legs of the frame body 43 are fixed to the upper surface of the substrate 44, and the position of the airbag 41 is always held by the frame body 43. Therefore, the airbag 41 does not shift from below the foot valve 6, and a force can be surely applied to close the foot valve 6 during inflation. Also, the lower end portions of the legs of the frame body 43 may be directly fixed to the upper surface of the inner shell bottom 2a, the number of legs may be three, or more than four. Moreover, by making the recess 45 larger than the outer shape of the airbag 41 and having a depth that can completely accommodate the deflated airbag 41, the position of the airbag 41 can be held more stably.

[0045] FIG. 9 is a longitudinal sectional view of the fifth example of the closing force applying mechanism 40 (an apparatus composed of a frame body 43 and a single airbag 41) in FIG. 8. As shown in Fig. 9(a), by using an airbag 41 whose height (thickness) in a deflated state is relatively small or as small as possible when the foot valve 6 is opened, interference with the foot valve 6 during opening can be reliably avoided. As a result, the foot valve 6 can be pushed down to approximately the same extent as in the normal state, and the dead stock during suction of the storage liquid 9 can be reduced as much as possible. When such a closing force applying mechanism 40 is provided, in order to reliably prevent contact between the foot valve 6 and the airbag 41 when the foot valve 6 is opened, the lower opening 17b can be brought closer to the inner shell bottom 2a while ensuring that the height H2 from the upper surface of the airbag 41 to the lower surface of the foot valve 6 is sufficiently long, so that the dead stock can be reduced. Also, by using an airbag 41 whose shape during contraction is as flat as possible, the dead stock can be reduced compared to the case where a bellows 34 is used. As shown in Fig. 9(c), at the time of time shut-off, N2 gas 29 is supplied into the airbag 41 from a pressurizing pipe 47 connected to the airbag 41, and a direct force can be applied in the direction of closing the foot valve 6 by the inflated airbag 41. Regarding other materials of the airbag 41 and the like, they are the same as in the third example.

[0046] 〔Sixth Example〕 Fig. 10 is a longitudinal sectional view of a sixth example of the closing force applying mechanism 40 (frame body 43 and a plurality of airbags 42). Here, it is different from the fifth example in that it is composed of a plurality of airbags 42 instead of a single airbag 41. Pressurizing pipes 47 are connected to the plurality of airbags 42 constituting the closing force applying mechanism 40, and by supplying N2 gas 29 to each of them, the plurality of airbags 42 can be inflated (Fig. 10(c)). As a mode of connecting the pressurizing pipes 47 (supplying N2 gas 29) to the plurality of airbags 42, for example, each airbag 42 may be connected in communication by an air supply pipe 48, or a pressurizing pipe 47 branched to each airbag 42 may be connected. Regarding other materials of the airbag 42 and the like, they are the same as in the third example.

[0047] [[Operation procedure during maintenance]] The operation procedure during maintenance using the closing force applying mechanisms 30 and 40 of the various cases (Case 1 to Case 6) described above will be described. Here, the description will be given using Case 1 shown in FIGS. 1 to 3 as a representative, but the same can be considered for the other Cases 2 to 6.

[0048] When inspecting the submerged pump 4 and pulling it out from inside the pump column 5 to the outside, the operation of the submerged pump 4 is stopped. A cable (not shown) from a hoisting device (not shown) such as a hoist is connected to the connecting member 28a of the lift shaft 28. When the lift shaft 28 is lifted by the hoisting device, the submerged pump 4 rises via the support cable 7 connected to the lift shaft 28. When the foot valve 6 is released from the gravity of the submerged pump 4 and the tip 4a of the submerged pump 4 is separated from the upper surface 25a of the protrusion 25 of the foot valve 6, it is in a closed state by the force (biasing force) of the spring 27 of the valve opening / closing mechanism 15. The position of the lift shaft 28 is fixed at the lifted position by a spacer (not shown). At this time, the inside of the pump column 5 is purged with N2 gas through the purge pipe 26.

[0049] Next, N2 gas 29 is supplied to the bellow 34 of the closing force applying mechanism 30 through the pressure pipe 38 to apply an additional force in the direction of closing the foot valve 6. As a result, in addition to the mechanism that normally closes the foot valve 6 by the biasing force of the spring 27, a mechanism that applies an additional force in the direction of closing the foot valve 6 by the closing force applying mechanism 30 operates. And, by these synergistic effects, the closing force of the foot valve 6 can be increased, and the intrusion of the stored liquid 9 in the low-temperature tank 1 into the pump column 5 and the leakage of the vaporized gas of the stored liquid 9 to the outside of the low-temperature tank 1 can be surely prevented.

[0050] Next, remove the head plate 8 from the upper part of the pump column 5, remove the support cable 7 connected to the head plate 8, wind the lift cable (not shown) suspended from the head plate 8 around a hoisting device (not shown) such as a hoist, and operate the hoisting device to pull out the submerged pump 4 from within the pump column 5.

[0051] A ring plate-shaped seal member 14 for sealing between the lower end surface 20a of the lower flange portion 20 and the upper end surface 6a of the foot valve 6 when the foot valve 6 is closed is attached to the lower flange portion 20 of the foot valve adapter portion 17 attached to the lower part of the pump column 5. This seal member 14 is made of PTFE or the like. This seal member 14 is disposed in a seal groove 13 provided in the lower flange portion 20. Here, if the submerged pump 4 is lifted and the foot valve 6 rises due to the biasing force of the spring 27 in conjunction with the movement of the submerged pump 4, and the surface contact between the lower end surface 20a of the lower flange portion 20 and the upper end surface 6a of the foot valve 6 is uneven, the closing of the lower opening 17b of the foot valve adapter portion 17 by the foot valve 6 will be incomplete, causing the storage liquid 9 such as ammonia to enter from within the low-temperature tank 1 into the pump column 5, and the vaporized gas of the storage liquid 9 to leak outside the low-temperature tank 1. In this regard, in the present embodiment, N2 gas 29 is supplied to the closing force applying mechanism 30 (bellows 34) provided between the upper surface of the inner shell bottom 2a and the lower surface of the foot valve 6, and the closing force of the foot valve 6 is increased by the synergistic effect of the biasing force of the spring 27 connected to the foot valve 6 and the gas pressure (for example, the operation in (c) in FIG. 3). Thus, the surface contact between the lower end surface 20a of the lower flange portion 20 and the upper end surface 6a of the foot valve 6 can be made stronger and more uniform, eliminating the gap, and completely preventing the storage liquid 9 from entering the pump column 5. Regarding the other second to sixth cases, maintenance work is also performed in the same manner as described above, and the same effects can be obtained.

[0052] According to the liquid lifting device of the low-temperature tank 1 of the above-described embodiment, the following advantages can be obtained. (1) An additional closing force applying mechanism 30 (40) can be easily implemented by providing, between the upper surface of the bottom 2a (bottom plate) of the inner shell of the low-temperature tank 1 and the lower surface of the foot valve 6, a simple member such as a bellows 34 (36) or an airbag 35 (37, 41, 42) to increase the closing force of the foot valve 6. (2) With the foot valve 6 closed by the force of the spring 27 of the valve opening / closing mechanism 15 when the submerged pump 4 is lifted, by supplying N2 gas 29 to the bellows 34 (36) or the airbag 35 (37, 41, 42) of the closing force applying mechanism 30 (40) and causing it to expand or inflate, an additional force can be applied in the upward pushing direction of the foot valve 6, and the foot valve 6 can be surely closed by the synergistic effect of the spring force and the gas pressure. (3) Therefore, with the closing force of the foot valve 6 improved, the head plate 8 can be removed, so that the stored liquid 9 (such as ammonia) does not enter the pump column 5 during pump maintenance and does not leak outside the tank. (4) Further, the closing force applying mechanism 30 (40) for improving the closing force of the foot valve 6 is separate from the foot valve 6, and the installation of the existing foot valve 6 and the additional closing force applying mechanism 30 (40) can be carried out simultaneously, leading to a shortening of the construction period. (5) There is no need to modify the existing foot valve 6, and it can be implemented regardless of the specification (structure) of the foot valve 6. Furthermore, by adjusting the number and size of the bellows 34 (36) and the airbag 35 (37, 41, 42) constituting the closing force applying mechanism 30 (40), it can be easily implemented regardless of the size of the foot valve 6 (for example, about 12B to 24B). (6) Furthermore, by using the same type of gas as the gas for purging the inside of the pump column 5 as the pressurized fluid for applying a force in the closing direction of the foot valve 6, it can be easily implemented without preparing another gas for pressurization.

Explanation of reference numerals

[0053] 1 Low-temperature tank 2 Inner shell 2a Bottom of inner shell 2b Side of inner shell Inner shell roof base 3 Outer shell 3a Outer shell bottom 3b Outer shell side 3c Outer shell roof base 3d Seal metal 4 Submerged pump 4a Tip 4b Connecting member 5 Pump column 5a Upper opening 5b Lower opening 6 Foot valve 6a Upper end face 7 Support cable 8 Head plate 9 Storage liquid 10 Discharge pipe 11 Heat insulator 11a Bottom heat insulator 11b Side heat insulator 11c Roof base heat insulator 12 Foundation 13 Seal groove 14 Seal member 15 Valve opening / closing mechanism 16 Shaft member 16a First end 16b Second end 16c Rod-shaped member 17 Foot valve adapter part 17a Upper opening 17b Lower opening (liquid suction port) 18 Upper flange part (of foot valve adapter part) 19 Cylindrical part 20 Lower flange part (of foot valve adapter part) 20a Lower end face 20b Insertion hole 21 Flange mounting bolt 22 Flange mounting nut 23 Upper flange (of pump column) 24 Lower flange (of pump column) 25 Protrusion 25a Upper surface 26 Purge pipe 26a valve 27 spring 28 lift shaft 28a connecting member 29 pressurized fluid (N2 gas) 30 closing force applying mechanism 31 upper contact plate 31a fitting hole 32 lower contact plate 33 guide pipe 34 bellows (singular) 35 airbag (singular) 36 bellows (plural) 37 airbags (plural) 38 pressurizing pipe 38a valve 39 air supply pipe 40 closing force applying mechanism 41 airbag (singular) 42 airbags (plural) 43 frame 44 substrate 45 recess 46 opening 47 pressurizing pipe 48 air supply pipe 49 recess

Claims

1. A cylindrical pump column erected through the roof of a low-temperature tank, a head plate closing the upper opening of the pump column, a submerged pump housed in the pump column so as to be liftable, a foot valve disposed between the submerged pump and the bottom of the inner shell of the low-temperature tank and opened and closed by the lifting of the submerged pump, a foot valve adapter portion connected to the lower portion of the pump column, supporting the foot valve in an operable state of opening and closing, and capable of contacting the foot valve at the lower edge portion, a valve opening and closing mechanism provided in the foot valve adapter portion, closing the foot valve with an urging force when the submerged pump ascends, and opening the foot valve by receiving the weight of the submerged pump resisting the urging force when descending, a closing force applying mechanism installed on the bottom of the inner shell of the low-temperature tank, and further applying a force in the direction of closing the foot valve by adding to the urging force of the valve opening and closing mechanism by supplying pressurized fluid from the outside, a pressurizing pipe for supplying the pressurized fluid to the closing force applying mechanism, A liquid lifting device for a low-temperature tank, which supplies the pressurized fluid to the closing force applying mechanism through the pressurizing pipe in a state where the foot valve is closed by the urging force of the valve opening and closing mechanism, and further applies a force in the direction of closing the foot valve.

2. The closing force applying mechanism is a lower contact plate placed on the bottom of the inner shell, a bellows placed on the lower contact plate, an upper contact plate placed on the bellows, and a guide pipe fixed to the upper part of the lower contact plate and slidably arranged in a fitting hole provided in the upper contact plate. The pressurizing pipe is connected to the bellows, and by supplying the pressurized fluid into the bellows, as the bellows extends, the upper contact plate is lifted, and a further force is applied in the direction of closing the foot valve. The liquid lifting device for a low-temperature tank according to Claim 1.

3. The closing force applying mechanism is a lower contact plate placed on the bottom of the inner shell, an air bag placed on the lower contact plate, an upper contact plate placed on the air bag, and a guide pipe fixed to the upper part of the lower contact plate and slidably arranged in a fitting hole provided in the upper contact plate. The pressurizing pipe is connected to the airbag, and supplies the pressurizing fluid into the airbag. As the airbag expands, the upper contact plate is lifted, and further force is applied in the direction of closing the foot valve. The liquid lifting device for a cryogenic tank according to claim 1.

4. The closing force applying mechanism includes a substrate placed on the bottom of the inner shell, an airbag placed on the substrate, and a frame provided on the substrate and surrounding the airbag with legs provided at four corners thereof. The frame has an opening through which a part of the foot valve adapter portion and the foot valve can be inserted when the foot valve is opened downward. The pressurizing pipe is connected to the airbag, and supplies the pressurizing fluid into the airbag to expand the airbag and further apply force in the direction of closing the foot valve. The liquid lifting device for a cryogenic tank according to claim 1.

5. The pressurizing fluid supplied by the pressurizing pipe is the same type of fluid as the pressurizing fluid for purging inside the pump column. The liquid lifting device for a cryogenic tank according to any one of claims 1 to 4. ​

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