Foot valve assembly and submerged pump system

Abstract

To provide a submerged pump system which enables a valve body of a foot valve assembly to be stably opened by the self-weight of a pump while ensuring the sealability of the foot valve assembly.SOLUTION: A foot valve assembly 6 according to the present invention includes: a cylindrical adapter 10 attached to a lower opening end 2b of a cylindrical pump column 2 in which a pump 5 submerged in a handling liquid is housed, the adapter 10 configured to house a suction port 5a of the pump; a disc-shaped valve body 20 which opens and closes a lower opening 11a of the adapter according to raising and lowering of the pump; a biasing member 62 that biases the valve body toward the adapter side; and an auxiliary valve 50 which opens and closes according to the pump raising and lowering and assists the valve body to open when the valve body is closed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a foot valve assembly and a submerged pump system. [Background technology]

[0002] Submerged pumping systems are used to extract liquefied gas (such as liquefied natural gas or liquefied ammonia) from storage tanks. The pump (submerged pump) is housed in a pump column that extends from the ceiling of the storage tank into the liquefied gas and is submerged in the liquefied gas. The lower open end of the pump column is opened and closed by a foot valve assembly.

[0003] In a submerged pump system, the pump is removed from the storage tank, for example, for maintenance. When the pump is stopped, the pump column is filled with residual liquefied gas and vaporized liquefied gas (vaporized gas). If the head plate is removed in this state, the liquefied gas and vaporized gas (hereinafter collectively referred to as "residual gas") will leak to the outside. Since most residual gases are flammable and toxic, they must be removed before the head plate is removed. To remove the residual gas, a method is used in which an inert gas such as nitrogen is introduced into the pump column while the valve body of the foot valve assembly is closed (see, for example, Patent Document 1).

[0004] The valve disc is biased upward, i.e., in the valve closing direction, by a spring, and opens under the pump's own weight when the pump is operating (see, for example, Patent Document 2). Therefore, when the pump is lifted, the valve disc is closed by the biasing force of the spring. When inert gas is introduced into the pump column in this state, the residual gas returns to the storage tank while slightly opening the valve disc, and the inside of the pump column is purged with inert gas.

[0005] After purging, the valve disc is biased in the valve closing direction by a spring and hydraulic pressure corresponding to the amount (liquid level) of liquefied gas in the storage tank. As a result, the valve disc closes, and the protrusion on the valve disc presses against the opposing elastic material, sealing the foot valve assembly. In other words, the sealing performance of the foot valve assembly depends on the biasing force and hydraulic pressure. If the amount (liquid level) of liquefied gas in the storage tank decreases, the hydraulic pressure decreases, and the sealing performance of the foot valve assembly may deteriorate. As a result, a small amount of liquefied gas may leak into the foot valve assembly (into the pump column) during maintenance work. If the biasing force is increased to prevent liquefied gas leakage, the valve disc becomes difficult to open under the pump's own weight alone, especially when the hydraulic pressure is high. In this case, auxiliary work is required to increase the pressure inside the pump column by introducing gas into the pump column, thereby assisting the valve disc in opening. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-132619 [Patent Document 2] Japanese Utility Model Application Publication No. 05-78992 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to ensure the sealing performance of a foot valve assembly in a submerged pump system while allowing the valve element of the foot valve assembly to stably open under the weight of the pump. [Means for solving the problem]

[0008] In one embodiment of the present invention, a foot valve assembly is attached to the lower open end of a cylindrical pump column that houses a pump that is immersed in the pumped liquid, and comprises a cylindrical adapter that houses the suction port of the pump, a disk-shaped valve body that opens and closes the lower opening of the adapter in accordance with the rise and fall of the pump, a biasing member that biases the valve body toward the adapter, and an auxiliary valve that opens and closes in accordance with the rise and fall of the pump and assists in opening the valve body when it is closed.

[0009] One implementation of the present invention Aspects The submerged pump system in the above document comprises a pump that is immersed in the pumped liquid, a cylindrical pump column that houses the pump, and the foot valve assembly. [Effects of the Invention]

[0010] According to the present invention, in a submerged pump system, the valve element of the foot valve assembly can be stably opened by the weight of the pump while ensuring the sealing performance of the foot valve assembly. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an embodiment of a submerged pump system according to the present invention. [Figure 2] 1 is a cross-sectional view showing an embodiment of a foot valve assembly according to the present invention. [Figure 3] FIG. 3 is a schematic enlarged cross-sectional view of a portion A of the foot valve assembly of FIG. 2. [Figure 4] 3 is an enlarged schematic cross-sectional view of a portion A of the foot valve assembly of FIG. 2 when the pump included in the submerged pump system of FIG. 1 is in a lowered position. FIG. [Figure 5] 3 is a schematic enlarged cross-sectional view of a portion A of the foot valve assembly of FIG. 2 when the auxiliary valve element of the foot valve assembly is open. FIG. [Figure 6] 3 is a schematic enlarged cross-sectional view of a portion A of the foot valve assembly of FIG. 2 when the auxiliary valve element of the foot valve assembly is closed. FIG. [Figure 7]3 is a schematic enlarged cross-sectional view of part A of the foot valve assembly of FIG. 2 when an inert gas is being introduced. FIG. [Figure 8] 3 is a schematic enlarged cross-sectional view of part A of the foot valve assembly of FIG. 2 at the time when the introduction of the inert gas is completed. FIG. [Figure 9] 7 is a schematic enlarged cross-sectional view of a portion A of the foot valve assembly of FIG. 2 when the auxiliary valve element of FIG. 6 is open. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a submerged pump system and a foot valve assembly according to the present invention will be described with reference to the drawings. In each drawing, the same components and elements are designated by the same reference numerals, and duplicated explanations will be omitted. In addition, in each drawing, the shape and size of each component are intentionally exaggerated compared to their actual dimensions in order to clarify the configuration of each component.

[0013] In the following description and drawings, "downward" refers to the direction of gravity, and "upward" refers to the opposite direction of downward.

[0014] ●Submerged pump system● First, an embodiment of a submerged pump system according to the present invention will be described.

[0015] ●Configuration of submerged pump system FIG. 1 is a schematic cross-sectional view showing an embodiment of a submerged pump system according to the present invention.

[0016] The submerged pump system 1 is attached to a storage tank T in which liquefied gas Lg is stored, and pumps the liquefied gas Lg from the storage tank T to the outside. The submerged pump system 1 comprises a pump column 2, a sealing member 3, a support cable 4, a submerged pump (hereinafter referred to as "pump") 5, and a foot valve assembly 6. In this embodiment, the liquefied gas Lg is transformation Ammonia. Liquefied ammonia is an example of the handled liquid in the present invention.

[0017] In the present invention, the handled liquid is not limited to liquefied ammonia, and may be, for example, liquefied natural gas.

[0018] The pump column 2 houses the pump 5 and functions as a liquid transport path for the liquefied gas Lg discharged from the pump 5. The pump column 2 is cylindrical in shape. The pump column 2 is disposed so as to penetrate the ceiling T1 of the storage tank T and extends from the ceiling T1 into the liquefied gas Lg. A liquid transport path R1 for the liquefied gas Lg is connected to the outer peripheral surface of the upper part of the pump column 2. In the radial direction of the pump column 2, the lower end of the pump column 2 protrudes outward and forms a lower flange portion 2c.

[0019] The sealing member 3 liquid-tightly seals the upper open end 2a of the pump column 2, and supports the pump 5 by suspending it via a support cable 4 when the pump 5 is raised and lowered within the pump column 2. The sealing member 3 includes a head plate 3a that closes the upper open end 2a of the pump column 2, and a lift shaft 3b that is disposed to penetrate the head plate 3a. The lift shaft 3b is raised and lowered when the pump 5 is raised and lowered, and supports the pump 5 via the support cable 4.

[0020] The support cable 4 suspends and supports the pump 5 when the pump 5 is raised and lowered within the pump column 2. The support cable 4 is made of, for example, a metal wire. The support cable 4 is connected to the lift shaft 3b and the pump 5.

[0021] The pump 5 discharges the liquefied gas Lg that has flowed in from the foot valve assembly 6 into the pump column 2. The pump 5 is, for example, a known submerged pump that is configured with a multi-stage centrifugal pump and a motor that drives the multi-stage centrifugal pump. Power for the pump 5 is supplied via a power cable (not shown) that is connected to the sealing member 3. The pump 5 is housed in the lower part of the pump column 2 and is immersed in the liquefied gas Lg. The pump 5 moves between a lowered position and a lowered position in response to the elevation of the lift shaft 3b. riseThe pump column 2 is raised and lowered between the above positions.

[0022] The "lowered position" is a position where the pump 5 is not lifted by the lift shaft 3b and is supported by an inclined surface 14 (described later) of the foot valve assembly 6. The "raised position" is a position where the pump 5 is suspended (lifted) from the lift shaft 3b via the support cable 4 when the lift shaft 3b is lifted to a predetermined height.

[0023] The foot valve assembly 6 opens and closes the lower open end 2b of the pump column 2. The specific configuration of the foot valve assembly 6 will be described later.

[0024] ● Foot valve assembly configuration Next, a specific configuration of the foot valve assembly 6 according to the present invention will be described.

[0025] FIG. 2 is a cross-sectional view showing an embodiment of a foot valve assembly 6 according to the present invention. FIG. 3 is a schematic enlarged cross-sectional view of part A of the foot valve assembly 6 in FIG. Figures 2 and 3 show the foot valve assembly 6 when the pump 5 is in the lowered position. For ease of explanation, Figure 2 also shows the lower part of the pump column 2 and the pump 5. In the following explanation, the bolt holes corresponding to the first mounting bolts B1, which will be described later, are well known and will not be described further. Figure 1 will be referenced as needed in the following explanation.

[0026] The foot valve assembly 6 includes an adapter 10, a valve body 20, a seal member 30, a retainer plate 40, an auxiliary valve 50, a plurality of biasing units 60, a plurality of first mounting bolts B1, a plurality of second mounting bolts B2, and a mounting nut N.

[0027] The adapter 10 is a member that attaches the valve element 20 to the pump column 2 and functions as a housing for the foot valve assembly 6. The adapter 10 includes a cylindrical portion 11, a first flange portion 12, a second flange portion 13, an inclined surface 14, a plurality of insertion holes 15, and a recess 16.

[0028] The cylindrical portion 11 accommodates an intake port (suction manifold) 5a disposed at the lower end of the pump 5. The cylindrical portion 11 is substantially cylindrical in shape. In the following description of the adapter 10, the term "radial direction" refers to the radial direction of the cylindrical portion 11, and the term "circumferential direction" refers to the circumferential direction of the cylindrical portion 11.

[0029] The upper end of the cylindrical portion 11 protrudes outward in the radial direction to form a ring-shaped first flange portion 12. The lower end of the cylindrical portion 11 protrudes outward in the radial direction to form a ring-shaped second flange portion 13. In other words, the cylindrical portion 11 is molded integrally with the first flange portion 12 and the second flange portion 13.

[0030] In the vertical direction, the upper half of the inner circumferential surface of the cylindrical portion 11 continuously increases in diameter from the center toward the upper end, forming an inclined surface 14 .

[0031] The insertion holes 15 are through-holes that pass through the second flange portion 13 in the up-down direction. The insertion holes 15 are arranged at equal intervals around the outer edge of the second flange portion 13 in the circumferential direction.

[0032] The area of ​​the lower end surface 10a of the adapter 10 (the lower surface of the cylindrical portion 11 and the second flange portion 13; the same applies below) on the inner edge side is recessed upward in a ring-like plate shape to form a recess 16. The recess 16 has a plurality of female threaded holes 16a. The female threaded holes 16a are arranged at equal intervals in the circumferential direction in the recess 16.

[0033] The adapter 10 is attached to the lower open end 2b of the pump column 2 by fastening the first flange portion 12 to the lower flange portion 2c of the pump column 2 with first mounting bolts B1 and mounting nuts N.

[0034] The valve element 20 opens and closes the lower opening 11a of the cylindrical portion 11 (i.e., the lower opening of the adapter 10). The shape of the valve element 20 is disk-shaped. The diameter of the valve element 20 is approximately the same as the outer diameter of the second flange portion 13 of the adapter 10. The valve element 20 includes a convex portion 21, a flow rectifying portion 22, a flow path forming portion 23, multiple vortex dissipation plates 24, a protrusion 25, an insertion hole 26, a recess 27, and multiple insertion holes 28. In the following description of the valve element 20, "radial direction" means the radial direction of the valve element 20, and "circumferential direction" means the circumferential direction of the valve element 20.

[0035] The center of the valve body 20 protrudes upward in a generally truncated cone shape (mountain shape), forming a protrusion 21. The protrusion 21 reinforces the valve body 20 and also guides the liquefied gas Lg that has flowed in from the inflow channel FL to the pump 5.

[0036] The flow rectifying portion 22 rectifies the liquefied gas Lg that has flowed in from the inflow channel FL. The flow rectifying portion 22 is a portion of the valve body 20 that extends from the outer edge (foot portion) of the convex portion 21 to a portion inside a flow path forming portion 23, which will be described later.

[0037] The flow path forming portion 23 is a portion of the valve body 20 that is located below the lower end surface 10a of the adapter 10. Body 2 0. As will be described later, an inlet channel FL is formed between the upper surface 23a of the flow path forming portion 23 and the lower end surface 10a, through which the liquefied gas Lg flows toward the pump 5 when the valve body 20 is open (when the valve body 20 is open).

[0038] The vortex suppression plates 24 suppress the generation of vortices in the liquefied gas Lg that flows in from the inflow passage FL. The shape of the vortex suppression plate 24 is a substantially trapezoidal plate. The vortex suppression plates 24 are arranged on the upper surface 22a of the flow straightening section 22 so that the two side surfaces of the vortex suppression plate 24 are aligned in the radial direction. The vortex suppression plates 24 are also arranged at equal intervals in the circumferential direction. The upper surfaces 24a of the vortex suppression plates 24 are located above the top surfaces 21a of the protrusions 21.

[0039] When the valve body 20 is closed (when the valve body 20 is closed), the protrusion 25 seals the inlet channel FL together with the seal member 30. A portion of the flow path forming portion 23 located below the recess 16 protrudes upward in a ring shape to form the protrusion 25. In the radial direction, the cross-sectional shape of the protrusion 25 is a triangle that is convex upward.

[0040] The insertion hole 26 is a through-hole that penetrates the valve body 20 in the vertical direction. The insertion hole 26 is an example of a communication hole in the present invention. The insertion hole 26 is arranged in the flow rectifying section 22 of the valve body 20. In this embodiment, the insertion hole 26 is arranged between two vortex dissipation plates 24. The lower end of the insertion hole 26 continuously increases in diameter, forming a hemispherical recess 27. In other words, the periphery of the insertion hole 26 on the lower surface 20b of the valve body 20 is recessed upward in a hemispherical shape, thereby forming the recess 27. The shape of the inner surface (lower surface) 27a of the recess 27 is hemispherical, following the shape of the upper surface 51a of the auxiliary valve body 51 described later.

[0041] The fitting holes 28 are through-holes that pass through the flow path forming portion 23 in the up-down direction. The fitting holes 28 are arranged at equal intervals in the circumferential direction at positions that face the insertion holes 15.

[0042] The valve element 20 is attached to the adapter 10 so as to be able to open and close the lower opening 11a of the cylindrical portion 11 by the biasing unit 60. At this time, the protrusion 25 is disposed opposite the seal member 30 and protrudes from the upper surface 23a of the flow path forming portion 23 toward the seal member 30.

[0043] The seal member 30 is Valve body 20 When the valve is closed, it seals the inflow channel FL together with the protrusion 25. The seal member 30 is, for example, a ring-shaped gasket. The seal member 30 is made of, for example, a fluororesin such as PTFE (polytetrafluoroethylene). The seal member 30 is disposed in the recess 16. The seal member 30 has a plurality of insertion holes 30a. In the circumferential direction of the seal member 30, the insertion holes 30a are disposed at equal intervals at positions facing the female thread holes 16a.

[0044] The pressing plate 40 fixes the sealing member 30 to the recess 16. The pressing plate 40 is, for example, shaped like a ring plate. The pressing plate 40 is disposed in the recess 16. The pressing plate 40 has a plurality of insertion holes 40a. In the circumferential direction of the pressing plate 40, the insertion holes 40a are disposed at equal intervals at positions facing the insertion holes 30a of the sealing member 30.

[0045] The sealing member 30 and the pressing plate 40 are attached to the recess 16 by threading the second mounting bolt B2, which is inserted through the two insertion holes 30a, 40a, into the female threaded hole 16a. At this time, the sealing member 30 is sandwiched between the recess 16 and the pressing plate 40.

[0046] The auxiliary valve 50 opens and closes the insertion hole 26. The auxiliary valve 50 is, for example, a poppet valve. The auxiliary valve 50 includes an auxiliary valve body 51, a shaft member 52, a spring 53, and a retainer 54.

[0047] The auxiliary valve element 51 opens and closes the insertion hole 26. The auxiliary valve element 51 has a circular shape in a plan view. The upper surface 51a of the auxiliary valve element 51 has a semispherical shape that is convex upward. The central portion of the upper surface 51a of the auxiliary valve element 51 protrudes upward in a cylindrical shape and forms the shaft member 52. In other words, the auxiliary valve element 51 is formed integrally with the shaft member 52.

[0048] The shaft member 52 guides the opening and closing of the auxiliary valve body 51 and the expansion and contraction of the spring 53. The shape of the shaft member 52 is a cylinder extending in the vertical direction. The shaft member 52 is inserted into the insertion hole 26 of the valve body 20 from below. The diameter of the shaft member 52 is smaller than the inner diameter of the insertion hole 26. Therefore, a cylindrical gap (hereinafter referred to as "cylindrical space S1") is formed between the shaft member 52 and the insertion hole 26.

[0049] The spring 53 expands and contracts along the shaft member 52, and biases the auxiliary valve element 51 in the direction in which the auxiliary valve element 51 closes (towards the valve element 20 (upward)). The spring 53 is, for example, a coil spring. The spring 53 is disposed above the flow rectifying portion 22 of the valve element 20. The portion of the shaft member 52 that protrudes above the valve element 20 is inserted into the spring 53. The spring 53 is an example of an auxiliary biasing member in the present invention.

[0050] The retainer 54 fixes the position of one end (upper end) of the spring 53 relative to the shaft member 52. The retainer 54 is, for example, in the shape of a ring plate. The retainer 54 is attached to the upper end of the shaft member 52 in a state in which the upper end of the spring 53 is pressed downward. As a result, the spring 53 is disposed between the retainer 54 and the flow rectifying portion 22. The spring 53 biases the retainer 54 upward, thereby biasing the auxiliary valve element 51 upward, i.e., toward the valve element 20, via the shaft member 52.

[0051] In the vertical direction, the length L1 of the auxiliary valve 50 (i.e., the length from the lower surface 51b of the auxiliary valve element 51 to the upper end surface 52a of the shaft member 52 (the upper surface 54a of the retainer 54)) is longer than the length L2 from the lower surface 20b of the valve element 20 to the upper surface 24a of the vortex dissipation plate 24. In other words, when the auxiliary valve element 51 is closed, the upper part of the shaft member 52 and the retainer 54 protrude above the upper surface 24a of the vortex dissipation plate 24.

[0052] The biasing unit 60 attaches the valve body 20 to the adapter 10 and biases the valve body 20 toward the adapter 10. The biasing unit 60 includes a shaft member 61, a spring 62, and a retainer 63.

[0053] The shaft member 61 guides the expansion and contraction of the spring 62. The shaft member 61 has a cylindrical shape extending in the up-down direction. The shaft member 61 is inserted from below into the insertion hole 28 of the valve body 20 and the insertion hole 15 of the adapter 10. The lower part of the shaft member 61 is inserted into the insertion hole 28. A part of the shaft member 61 protrudes above the second flange portion 13.

[0054] The spring 62 expands and contracts along the shaft member 61, and biases the valve body 20 in the direction in which the valve body 20 closes (towards the adapter 10 (upward)). The spring 62 is, for example, a coil spring. The spring 62 is disposed above the second flange portion 13. A portion of the shaft member 61 that protrudes above the second flange portion 13 is inserted into the spring 62. The spring 62 is an example of a biasing member in the present invention.

[0055] The retainer 63 fixes the position of one end (upper end) of the spring 62 relative to the shaft member 61. The retainer 63 is, for example, shaped like a ring plate. The retainer 63 is attached to the upper end of the shaft member 61 in a state in which the upper end of the spring 62 is pressed downward. As a result, the spring 62 is disposed between the retainer 63 and the second flange portion 13. The spring 62 biases the retainer 63 upward, thereby biasing the valve body 20 upward, i.e., toward the adapter 10, via the shaft member 61.

[0056] ●Operation of the foot valve assembly Next, the operation of the foot valve assembly 6 will be described, focusing on the opening and closing operations of the valve element 20 and the auxiliary valve element 51. In the following description, Figures 1 and 3 will be referred to as appropriate.

[0057] The valve element 20 and the auxiliary valve element 51 open when the weight of the pump 5, i.e., the load from the pump 5 (hereinafter referred to as the "pump load"), is applied, and close when the pump load is removed. In this way, the valve element 20 and the auxiliary valve element 51 open and close in response to the elevation and lowering of the pump 5.

[0058] ● Operation when the pump is in the lowered position

[0059] FIG. 4 is a schematic enlarged cross-sectional view of part A of the foot valve assembly 6 in FIG. 2 when the pump 5 is in the lowered position. In this figure and the following figures (FIGS. 5 to 9), the area where the liquefied gas Lg exists is shown by a dotted pattern in order to clarify the area.

[0060] First, when the pump 5 is in the lowered position, a part of the pump 5 abuts against the inclined surface 14, and the lower end surface 5b of the pump 5 abuts against the upper surface 24a of the vortex dissipation plate 24 and the upper surface 50a of the auxiliary valve 50 (the upper end surface 52a of the shaft member 52 and the upper surface 54a of the retainer 54). At this time, the pump load is applied to the valve element 20 in the valve opening direction (downward), and the biasing force of the spring 62 (hereinafter simply referred to as the "biasing force") is applied to the valve closing direction (upward). The biasing force is smaller than the pump load, and the valve element 20 is opened by the pump load. In addition, the pump load is applied to the auxiliary valve 50. Auxiliary valve element 51 The spring 53 is applied in the valve opening direction (downward), and the biasing force of the spring 53 (hereinafter referred to as the "auxiliary biasing force") is Auxiliary valve element 51 The auxiliary biasing force is applied in the valve closing direction (upward). The auxiliary biasing force is smaller than the pump load and biasing force, and the auxiliary valve element 51 opens due to the pump load.

[0061] When the valve element 20 is open, an inflow path FL is formed between the lower end surface 10a of the adapter 10 and the upper surface 23a of the flow path forming portion 23. As a result, liquefied gas Lg flows from the storage tank T through the inflow path FL into the space between the vortex dissipation plates 24. The liquefied gas Lg is then rectified by the vortex dissipation plates 24 and guided to the pump 5 by the convex portion 21. Furthermore, when the auxiliary valve element 51 is open, a small amount of liquefied gas Lg flows from the storage tank T through the concave portion 27 and the insertion hole 26 (cylindrical space S1) into the space between the two vortex dissipation plates 24, 24.

[0062] ● Operation when the pump is rising from the lowered position to the raised position FIG. 5 is a schematic enlarged cross-sectional view of the portion A of the foot valve assembly 6 in FIG. 2 when the valve body 20 is closed.

[0063] When the pump 5 is raised from the lowered position to the raised position, the valve element 20 is gradually closed by the biasing force in accordance with the rise of the pump 5.

[0064] Next, when the lower end surface 5b of the pump 5 is separated from the upper surface 24a of the vortex dissipation plate 24, the pump load on the valve element 20 is removed, and a biasing force is applied to the valve element 20 in the valve closing direction. Therefore, the valve element 20 is closed by the biasing force. At this time, the protrusion 25 is pressed against the seal member 30 by the biasing force. As a result, the protrusion 25 and the seal member 30 block the inflow passage FL. Meanwhile, the auxiliary valve element 51 is still open due to the pump load.

[0065] Next, when the pump 5 rises further, the pump load applied to the auxiliary valve element 51 decreases, and the auxiliary valve element 51 is gradually closed by the auxiliary biasing force as the pump 5 rises.

[0066] FIG. 6 is a schematic enlarged cross-sectional view of the portion A of the foot valve assembly 6 in FIG. 2 when the auxiliary valve element 51 is closed.

[0067] When the lower end surface 5b of the pump 5 is separated from the upper surface 50a of the auxiliary valve 50, the pump load on the auxiliary valve element 51 is removed, and an auxiliary biasing force is applied to the auxiliary valve element 51 in the valve closing direction. Therefore, the auxiliary valve element 51 is closed by the auxiliary biasing force. When the auxiliary valve element 51 is closed, the upper surface 51a of the auxiliary valve element 51 is in liquid-tight contact with the lower surface 27a of the recess 27. As a result, the auxiliary valve element 51 blocks the insertion hole 26 (cylindrical space S1). At this time, the internal space S2 surrounded by the adapter 10 and the valve element 20 is isolated from the external space S3 (inside the storage tank T) around the adapter 10 and the valve element 20.

[0068] Here, the internal space S2 is also continuous with the space inside the pump column 2. Therefore, in the following description, for convenience of explanation, the internal space S2 and the space inside the pump column 2 will be collectively referred to as the internal space S2.

[0069] Operation from the time of inert gas introduction to the time of introduction completion For example, when the pump 5 is removed from the pump column 2, or when the pump 5 is installed into the pump column 2 from outside the pump column 2, the valve element 20 and auxiliary valve element 51 are closed and the residual gas (liquefied gas Lg and vaporized liquefied gas Lg) in the pump column 2 is removed (purged) with inert gas. The operation of the foot valve assembly 6 from the time the inert gas is introduced until after the introduction is completed will be described below.

[0070] FIG. 7 is a schematic enlarged cross-sectional view of the portion A of the foot valve assembly 6 in FIG. 2 when the inert gas is being introduced. In the figure, the flow of the inert gas is indicated by an outline arrow, and the flow of the residual gas is indicated by a dashed arrow.

[0071] When the inert gas is introduced into the pump column 2, the residual gas in the pump column 2 is pushed downward by the pressure of the inert gas. At this time, the auxiliary valve element 51 opens against the auxiliary biasing force. As a result, the residual gas is released into the external space S3 (storage tank T) through the insertion hole 26 (cylindrical space S1). The valve element 20 also opens slightly against the biasing force. As a result, a small gap is created between the upper end of the protrusion 25 and the seal member 30, and the residual gas is released through this gap into the external space S3 (storage tank T).

[0072] FIG. 8 is a schematic enlarged cross-sectional view of the portion A of the foot valve assembly 6 in FIG. 2 after the introduction of the inert gas has been completed.

[0073] When the introduction of the inert gas into the pump column 2 is completed (when the residual gas is purged), the internal space S2 is filled with the inert gas. At this time, the valve body 20 and the auxiliary valve body 51 are subjected to a liquid pressure (hereinafter referred to as "external liquid pressure") corresponding to the liquid amount (liquid level) of the liquefied gas Lg stored in the storage tank T. Between the valve body 20 and the auxiliary valve body 51The valve element 20 is biased in the valve closing direction by the biasing force and the external hydraulic pressure, and is therefore closed. At this time, the protrusion 25 is pressed against the seal member 30 by the biasing force and the external hydraulic pressure. Meanwhile, the auxiliary valve element 51 is biased in the valve closing direction by the auxiliary biasing force and the external hydraulic pressure, and is therefore closed. Here, the area of ​​the lower surface 20b of the valve element 20 is sufficiently (for example, several tens to several hundreds of times) larger than the area of ​​the lower surface 51b of the auxiliary valve element 51. Therefore, the external hydraulic pressure applied to the auxiliary valve element 51 is sufficiently (for example, several tens to several hundreds of times) smaller than the external hydraulic pressure applied to the valve element 20.

[0074] Next, the head plate 3a is removed from the pump column 2, and the pump 5 is taken out from the pump column 2 and subjected to maintenance. After the maintenance is completed, the pump 5 is returned to the pump column 2 and lowered to the raised position while suspended from the lift shaft 3b. Next, the head plate 3a is attached to the pump column 2.

[0075] ● Operation when the pump is lowered from the raised position to the lowered position FIG. 9 is a schematic enlarged cross-sectional view of the portion A of the foot valve assembly 6 in FIG. 2 when the auxiliary valve element 51 is open.

[0076] When the pump 5 descends from the raised position to the lowered position, the lower end surface 5b of the pump 5 abuts against the upper surface 50a of the auxiliary valve 50. As a result, a pump load is applied to the auxiliary valve 50 in the valve opening direction. At this time, an auxiliary biasing force and external hydraulic pressure are applied to the auxiliary valve element 51 in the valve closing direction, and the pump load is applied to the auxiliary valve element 51 in the valve opening direction. As described above, the auxiliary biasing force is smaller than the pump load and biasing force. Furthermore, the external hydraulic pressure applied to the auxiliary valve element 51 is smaller than the pump load. Furthermore, in the auxiliary valve element 51, the force in the valve opening direction (pump load) is greater than the force in the valve closing direction (auxiliary biasing force and external hydraulic pressure). Therefore, when the pump load is applied to the auxiliary valve 50, the auxiliary valve element 51 begins to open due to the pump load. At this time, the internal space S2 is in communication with the inside of the storage tank T (external space S3) via the insertion hole 26 (cylindrical space S1). As a result, the liquefied gas Lg starts to flow into the internal space S2 through the insertion hole 26 (cylindrical space S1). In this way, the insertion hole 26 functions as a communication hole in the present invention.

[0077] Next, when the pump 5 further descends, the auxiliary valve element 51 opens in response to the descending of the pump 5.

[0078] Next, when the pump 5 further descends, the lower end surface 5b of the pump 5 abuts against the upper surface 24a of the vortex dissipation plate 24. As a result, a pump load is applied to the valve disc 20 in the valve-opening direction. At this time, the biasing force and external liquid pressure are applied to the valve disc 20 in the valve-closing direction, and the pump load and the liquid pressure due to the liquefied gas Lg in the internal space S2 (hereinafter referred to as "internal liquid pressure") are applied to the valve disc 20 in the valve-opening direction. Here, the biasing force is smaller than the pump load. As described above, the external liquid pressure applied to the valve disc 20 is large enough to resist the biasing force and the pump load. When the liquid pressure difference between the external liquid pressure and the internal liquid pressure is large in the valve disc 20, the force in the valve-opening direction (pump load and internal liquid pressure) is smaller than the force in the valve-closing direction (biasing force and external liquid pressure). Therefore, even if the pump load is applied to the valve disc 20, the valve disc 20 does not open.

[0079] When the auxiliary valve element 51 is open and the valve element 20 is closed, the liquefied gas Lg flows into the internal space S2 through the insertion hole 26 (cylindrical space S1). Therefore, the internal liquid pressure applied to the valve element 20 increases as the liquid level of the liquefied gas Lg in the internal space S2 rises, and when this liquid level becomes the same as the liquid level of the liquefied gas Lg in the storage tank T, it becomes approximately equal to the external liquid pressure. In other words, as the liquid level of the liquefied gas Lg in the internal space S2 rises, the liquid pressure difference decreases, and the force acting on the valve element 20 in the valve closing direction decreases. Then, when the difference between the pump load and the biasing force becomes greater than the liquid pressure difference, the valve element 20 begins to open due to the pump load. Finally, when a portion of the pump 5 abuts against the inclined surface 14 and the pump 5 is in the lowered position, the valve element 20 reaches its maximum open state, as shown in FIG. 4.

[0080] In this way, in the foot valve assembly 6, when the pump 5 descends, the auxiliary valve element 51 opens before the valve element 20, reducing the hydraulic pressure difference relative to the valve element 20 and assisting the valve element 20 in opening when the valve is closed. As a result, the biasing force of the foot valve assembly 6 can be increased to a value close to the pump load. Furthermore, in conventional foot valve assemblies without the auxiliary valve 50, increasing the biasing force requires auxiliary work, such as introducing gas into the pump column 2 to increase the pressure inside the pump column 2 and assisting the valve element in opening. However, in the foot valve assembly 6, such auxiliary work is unnecessary, and the valve element 20 opens stably due to the weight of the pump 5 (pump load). Therefore, the biasing force of the foot valve assembly 6 can be set greater than in conventional structures without considering the hydraulic pressure difference or auxiliary work. This improves the sealing performance of the foot valve assembly 6 (the sealing performance of the protrusion 25 and the seal member 30) compared to conventional foot valve assemblies.

[0081] In this embodiment, the handled liquid is liquefied ammonia, and the vaporized liquefied gas Lg is ammonia gas, which is flammable and highly toxic to living organisms. Furthermore, ammonia gas is lighter than air and is therefore easily inhaled by maintenance workers. As described above, the foot valve assembly 6 according to the present invention has higher sealing performance than conventional foot valve assemblies. Therefore, with the submerged pump system 1 according to the present invention, safe maintenance work can be performed even when the handled liquid is difficult to handle, such as liquefied ammonia.

[0082] Summary According to the embodiment described above, the foot valve assembly 6 includes the adapter 10, the valve element 20, the spring 62, and the auxiliary valve 50. The adapter 10 is attached to the lower open end 2b of the pump column 2. The valve element 20 opens and closes the lower opening 11a of the cylindrical portion 11 in response to the elevation and lowering of the pump 5. The spring 62 biases the valve element 20 toward the adapter 10. The auxiliary valve 50 opens and closes in response to the elevation and lowering of the pump 5, assisting the valve element 20 in opening when it is closed. With this configuration, the biasing force of the foot valve assembly 6 can be set greater than that of conventional structures without considering hydraulic pressure differences or auxiliary work. This improves the sealing performance of the foot valve assembly 6 compared to conventional foot valve assemblies. Therefore, the foot valve assembly 6 can stably open the valve element 20 using the weight of the pump 5 (pump load) while maintaining high sealing performance.

[0083] Furthermore, according to the embodiment described above, when the pump 5 descends and contacts the valve disc 20 with the auxiliary valve 50, the auxiliary valve 50 opens before the valve disc 20. With this configuration, the opening of the auxiliary valve 50 allows the liquefied gas Lg to flow into the foot valve assembly 6. As a result, the hydraulic pressure difference on the valve disc 20 decreases, and the force applied to the valve disc 20 becomes dominated by the biasing force in the valve closing direction and by the pump load in the valve opening direction. Therefore, the valve disc 20 is more likely to open due to the pump load. In this way, the auxiliary valve 50 can assist the opening of the valve disc 20 by eliminating the hydraulic pressure difference when the valve disc 20 is closed, without requiring any auxiliary work. Therefore, the foot valve assembly 6 can stably open the valve disc 20 using the weight of the pump 5 (pump load) while maintaining high sealing performance.

[0084] Furthermore, according to the embodiment described above, the foot valve assembly 6 includes the insertion hole 26. The insertion hole 26 connects the internal space S2 and the external space S3 when the valve element 20 is closed. The auxiliary valve 50 opens and closes the insertion hole 26 (cylindrical space S1). With this configuration, the auxiliary valve 50 opens when the valve element 20 is closed, causing the liquefied gas Lg in the external space S3 to flow into the internal space S2. As a result, as described above, the auxiliary valve 50 can assist in opening the valve element 20 by eliminating the hydraulic pressure difference when the valve element 20 is closed, without requiring any auxiliary work. Therefore, the foot valve assembly 6 can stably open the valve element 20 using the weight of the pump 5 (pump load) while maintaining high sealing performance.

[0085] Furthermore, according to the embodiment described above, the insertion hole 26 is located in the valve body 20. With this configuration, the foot valve assembly 6 according to the present invention can be easily realized by simply performing simple processing (forming a through hole and attaching the auxiliary valve 50) on the valve body of a conventional foot valve assembly.

[0086] Furthermore, according to the embodiment described above, the auxiliary valve 50 includes the auxiliary valve element 51 and the spring 53. The auxiliary valve element 51 opens and closes the insertion hole 26, and the spring 53 biases the auxiliary valve element 51 in the valve closing direction. The biasing force is smaller than the pump load and larger than the auxiliary biasing force. With this configuration, when the valve element 20 is closed, the auxiliary valve element 51 can open before the valve element 20. As a result, as described above, the auxiliary valve 50 can assist the opening of the valve element 20 by eliminating the hydraulic pressure difference when the valve element 20 is closed, without requiring any auxiliary work. Therefore, the foot valve assembly 6 can stably open the valve element 20 using the weight of the pump 5 (pump load) while maintaining high sealing performance.

[0087] Other embodiments In the embodiment described above, the adapter 10 may be provided with the insertion hole 26, and the auxiliary valve 50 may be disposed so as to pass through the adapter 10. In this case, for example, the insertion hole 26 may pass through a part of the cylindrical portion 11 (for example, the inclined surface 14).

[0088] Furthermore, in the embodiment described above, the valve body 20 may be provided with a plurality of insertion holes 26. In this case, the foot valve assembly 6 is provided with a plurality of auxiliary valves 50 corresponding to the respective insertion holes 26. Furthermore, the plurality of insertion holes 26 may be arranged at equal intervals in the circumferential direction of the valve body 20. In this configuration, the liquefied gas Lg flows into the internal space S2 through the plurality of insertion holes 26. Therefore, the time required to eliminate the liquid pressure difference is shortened.

[0089] Furthermore, in the embodiment described above, the position of the insertion hole 26 is not limited to this embodiment as long as it is a position where the upper surface 50a of the auxiliary valve 50 can abut against the pump 5 when the pump 5 is lowered. That is, for example, the insertion hole 26 may be disposed in the top surface 21a of the protrusion 21.

[0090] Furthermore, in the above-described embodiment, the configuration of the auxiliary valve 50 is not limited to a poppet valve. That is, for example, the auxiliary valve 50 may be configured as a solenoid valve that opens and closes the insertion hole 26. In this case, for example, the auxiliary valve 50 may be opened and closed manually, or may be opened and closed automatically based on a sensor that detects whether the pump 5 and the valve element 20 are in contact with each other.

[0091] Furthermore, in the embodiment described above, the shaft member 52 may be formed separately from the auxiliary valve element 51 and attached to the upper surface 51 a of the auxiliary valve element 51 .

[0092] Furthermore, in the embodiment described above, the foot valve assembly 6 may include a seal member disposed between the recess 27 and the auxiliary valve element 51. In this case, for example, either the recess 27 or the auxiliary valve element 51 may include a groove in which the seal member is disposed. Also, for example, the seal member may be attached to the auxiliary valve element 51 so as to cover the outer edge of the auxiliary valve element 51.

[0093] Furthermore, in the embodiment described above, the lower end of the insertion hole 26 does not have to have an expanded diameter. That is, the valve element 20 does not have to have the recess 27. In this case, for example, the upper surface 51a of the auxiliary valve element 51 may be plate-shaped and may be in liquid-tight contact with the lower surface 20b of the valve element 20 when the auxiliary valve element 51 is closed.

[0094] Furthermore, in the embodiment described above, the shape of the lower surface 27a of the recess 27 only needs to correspond to the shape of the upper surface 51a of the auxiliary valve body 51, and is not limited to this embodiment.

[0095] Furthermore, in the embodiment described above, the shape of auxiliary valve element 51 (the shape of upper surface 51a) is not limited to this embodiment as long as it is a shape that can block insertion hole 26 when auxiliary valve element 51 is closed. That is, for example, auxiliary valve element 51 may have a spherical, conical, or disc-like shape.

[0096] Furthermore, in each of the above-described embodiments, the cross-sectional shape of the top of the protrusion 25 is not limited to the illustrated shape (triangular shape). That is, for example, the cross-sectional shape may be semicircular or flat.

[0097] Furthermore, in each of the above-described embodiments, the material of the seal member 30 is not limited to PTFE, and may be any material that functions as a sealant for the pumped liquid.

[0098] ●Embodiments of the present invention● Next, the embodiments of the present invention that can be understood from the above-described embodiments will be described below, using the terms and symbols used in the embodiments.

[0099] A first embodiment of the present invention is a foot valve assembly (e.g., foot valve assembly 6) comprising: a cylindrical adapter (e.g., adapter 10) attached to a lower open end (e.g., lower open end 2b) of a cylindrical pump column (e.g., pump column 2) that houses a pump (e.g., pump 5) that is immersed in a handled liquid (e.g., liquefied gas Lg), and that houses a suction port (e.g., suction port 5a) of the pump; a disk-shaped valve element (e.g., valve element 20) that opens and closes the lower opening (e.g., lower opening 11a) of the adapter in accordance with the rise and fall of the pump; a biasing member (e.g., spring 62) that biases the valve element toward the adapter; and an auxiliary valve (e.g., auxiliary valve 50) that opens and closes in accordance with the rise and fall of the pump and assists in opening the valve element when it is closed. With this configuration, the foot valve assembly can ensure high sealing performance while allowing the valve element to stably open under the pump's own weight (pump load).

[0100] A second embodiment of the present invention is a foot valve assembly according to the first embodiment, wherein when the pump descends and contacts the valve body and the auxiliary valve, the auxiliary valve opens before the valve body. With this configuration, when the valve body is closed, the liquefied gas flowing in from the auxiliary valve reduces the liquid pressure difference on the valve body, making it easier for the valve body to open due to the pump load.

[0101] A third embodiment of the present invention is a foot valve assembly according to the first or second embodiment, which has a communication hole (e.g., insertion hole 26) that connects the internal space (e.g., internal space S2) surrounded by the adapter and the valve body when the valve body is closed to the external space (e.g., external space S3) around the adapter and the valve body, respectively, and the auxiliary valve is a foot valve assembly that opens and closes the communication hole. With this configuration, when the valve disc is closed, the auxiliary valve opens, allowing the liquefied gas in the external space to flow into the internal space. As a result, the hydraulic pressure difference decreases when the valve disc is closed, and the foot valve assembly can assist the valve disc in opening without requiring any auxiliary work.

[0102] A fourth embodiment of the present invention is the foot valve assembly of the third embodiment, wherein the communication hole is disposed in the valve body. With this configuration, the foot valve assembly according to the present invention can be easily realized by simply processing only the valve body of a conventional foot valve assembly.

[0103] A fifth embodiment of the present invention is a foot valve assembly according to the third or fourth embodiment, wherein the auxiliary valve comprises an auxiliary valve body (e.g., auxiliary valve body 51) that opens and closes the communication hole, and an auxiliary biasing member (e.g., spring 53) that biases the auxiliary valve body in the direction in which the auxiliary valve body closes, and the biasing force applied to the valve body by the biasing member is smaller than the pump load applied to the valve body by the pump and is larger than the biasing force applied to the auxiliary valve body by the auxiliary biasing member. According to this configuration, when the valve body is closed, the auxiliary valve body can open before the valve body.

[0104] A sixth embodiment of the present invention is a submerged pump system (e.g., submerged pump system 1) comprising a pump immersed in the pumped liquid, a cylindrical pump column accommodating the pump, and a foot valve assembly according to any one of the first to fifth embodiments. According to this configuration, in the submerged pump system, when the valve body is closed, the liquefied gas flowing in from the auxiliary valve reduces the liquid pressure difference on the valve body, making it easier for the valve body to open due to the pump load. [Explanation of symbols]

[0105] 1 Submerged Pump System 2 Pump column 2b Lower open end 5. Pump 5a Intake port 6 Foot valve assembly 10 Adapters 11a Bottom opening 20 Valve body 20b Bottom side 26 Insertion hole (communicating hole) 50 Auxiliary valve 51 Auxiliary valve body 53 Spring (auxiliary biasing member) 62 Spring (biasing member) S2 interior space S3 External Space

Claims

1. a cylindrical adapter attached to a lower open end of a cylindrical pump column that houses a pump that is immersed in the pumped liquid, and that houses a suction port of the pump; a disc-shaped valve body that opens and closes a lower opening of the adapter in response to the elevation and lowering of the pump; a biasing member that biases the valve body toward the adapter; an auxiliary valve that opens and closes in response to the elevation of the pump and assists the valve body in opening when the valve body is closed; consisting of Foot valve assembly.

2. When the pump descends and contacts the valve body and the auxiliary valve, the auxiliary valve opens before the valve body.

2. The foot valve assembly of claim 1.

3. a communication hole that communicates an internal space surrounded by the adapter and the valve body with an external space around the adapter and the valve body when the valve body is closed, The auxiliary valve opens and closes the communication hole.

3. A foot valve assembly according to claim 1 or 2.

4. The communication hole is disposed in the valve body.

4. The foot valve assembly of claim 3.

5. The auxiliary valve is an auxiliary valve body that opens and closes the communication hole; an auxiliary biasing member that biases the auxiliary valve body in a direction in which the auxiliary valve body closes; Equipped with The biasing force applied to the valve body by the biasing member is is smaller than the pump load applied to the valve body by the pump, the biasing force applied to the auxiliary valve body by the auxiliary biasing member is greater than the biasing force applied to the auxiliary valve body by the auxiliary biasing member; 5. A foot valve assembly according to claim 3 or 4.

6. a pump immersed in the handled liquid; a cylindrical pump column that houses the pump; A foot valve assembly according to any one of claims 1 to 5; consisting of Submerged pump system.

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