Flow path switching device and pump system

Abstract

To provide a flow path switching device that can reliably perform flow path switching operations when the pump stops operating. [Solution] The flow path switching device 5 is equipped with a valve body 42 that selectively connects the outlet flow path 35 to either the first inlet flow path 31 or the second inlet flow path 32. The first inlet flow path 31, the second inlet flow path 32, the outlet flow path 35, and the pressurizing chamber 38 are all connected to the valve chamber 37. When the valve body 42 is in the open position, the pressurizing chamber 38 is connected to the second inlet flow path 32. The pressurizing chamber 38, the valve chamber 37, and the first inlet flow path 31 are aligned along the direction of movement of the valve body 42. When the valve body 42 is in the open position, it is located between the pressurizing chamber 38 and the first inlet flow path 31.

Description

Technical Field

[0001] The present invention relates to a technique for preventing the idling of a submersible pump used for transferring liquefied gases such as liquid hydrogen, liquid nitrogen, liquefied ammonia, liquefied natural gas, liquefied ethylene gas, and liquefied petroleum gas.

Background Art

[0002] In order to pressurize the liquefied gas to the pressure required on the demand side, as shown in FIG. 18, a plurality of pumps 500 may be connected in series. The liquefied gas is sequentially pressurized by the plurality of pumps 500. Each pump 500 is installed in a suction container 505. The liquefied gas in the liquefied gas storage tank 502 is introduced into the suction container 505 through a suction port 501, and the entire pump 500 is immersed in the liquefied gas. Therefore, the pump 500 is a submersible pump that can operate in the liquefied gas. When the pump 500 is operated, the liquefied gas is sucked into the suction port 500a of the pump 500 and discharged by the pump 500 through a flow path switching device 510 and a liquefied gas discharge pipe 511.

[0003] FIG. 19 is a diagram showing the configuration of the flow path switching device 510. The flow path switching device 510 is a device for bypassing the liquefied gas through the pump 500 and transferring it to the liquefied gas discharge pipe 511. As shown in FIG. 19, the flow path switching device 510 includes a flow path structure 525 having a pump-side flow path 521, a container-side flow path 522, and an outflow flow path 523, and a valve body 527 disposed in the flow path structure 525. The pump-side flow path 521 communicates with the discharge port 500b of the pump 500, the container-side flow path 522 communicates with the pump chamber 530 in the suction container 505, and the outflow flow path 523 communicates with the liquefied gas discharge pipe 511.

[0004] The valve body 527 is positioned to selectively connect the outflow passage 523 to either the pump-side passage 521 or the container-side passage 522. In other words, the flow path switching device 510 is configured to selectively connect the liquefied gas discharge pipe 511 to either the discharge port 500b of the pump 500 or the pump chamber 530 in the suction container 505.

[0005] Figure 19 shows the state of the flow path switching device 510 when the pump 500 is in operation, and Figure 20 shows the state of the flow path switching device 510 when the pump 500 is not in operation. As shown in Figure 20, when the pump 500 is not in operation, the valve body 527 is pressed against the flow path structure 525 by a spring 531 to close the pump-side flow path 521. More specifically, the flow path structure 525 has a valve seat 532 formed around the outlet of the pump-side flow path 521, and the valve body 527 is pressed against the valve seat 532 by a spring 531. Therefore, while the valve body 527 is pressed against the valve seat 532, the pump-side flow path 521 is closed, and the container-side flow path 522 and the outflow flow path 523 are in communication. The container-side flow path 522 opens in the pump chamber 530 of the suction container 505 and communicates with the suction port 501 through the pump chamber 530.

[0006] When the pump 500 is operating, as shown in Figure 19, the liquefied gas is discharged from the outlet 500b of the pump 500 and flows into the pump-side flow path 521 of the flow path switching device 510. The liquefied gas flowing through the pump-side flow path 521 moves the valve body 527 against the force of the spring 531, opening the pump-side flow path 521 and closing the container-side flow path 522 with the valve body 527. As a result, the pump-side flow path 521 and the outflow flow path 523 are connected.

[0007] When the pump 500 stops operating, the valve body 527 is pressed against the valve seat 532 by the spring 531. As a result, as shown in Figure 20, the pump-side flow path 521 is closed, and the container-side flow path 522 and the outflow flow path 523 are connected. Thus, the flow path switching device 510 of this embodiment operates solely by the spring 531 and the flow of liquefied gas.

[0008] When the pump 500 stops operating, the flow path switching device 510 transitions from the open state shown in Figure 19 to the closed state shown in Figure 20. In the closed state shown in Figure 20, the pump-side flow path 521 is closed by the valve body 527. Therefore, as shown in Figure 21, the liquefied gas does not flow inside the pump 500, and the liquefied gas does not forcibly rotate the impeller of the pump 500 while it is stopped. As a result, unintended rotation of the pump 500's impeller is prevented, and damage to sliding parts such as bearings can be prevented. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2022 / 113450 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, immediately after one of the pumps 500 stops, the other pumps 500 are still operating, so the liquefied gas flows through the stopped pump 500. As a result, the flow path switching device 510 may not transition from the open state shown in Figure 19 to the closed state shown in Figure 20. That is, the liquefied gas flows from the stopped pump 500 to the pump-side flow path 521, pushing up the valve body 527 against the force of the spring 531. Therefore, the valve body 527 may not be able to close the pump-side flow path 521. One solution is to use a stronger spring 531, but such a spring 531 would obstruct the flow of liquefied gas when the pump 500 is operating normally, increasing fluid losses.

[0011] Therefore, the present invention provides a flow path switching device that can reliably perform a flow path switching operation when the pump stops operating. The present invention also provides a pump system equipped with such a flow path switching device. [Means for solving the problem]

[0012] In one embodiment, a flow path switching device is provided for preventing idling of a submersible pump used for transferring liquefied gas and located in a suction container, comprising a flow path structure having a first inlet flow path, a second inlet flow path, an outlet flow path, a valve chamber, and a pressurizing chamber, and a valve body located in the valve chamber for selectively connecting the outlet flow path to either the first inlet flow path or the second inlet flow path, wherein the first inlet flow path, the second inlet flow path, the outlet flow path, and the pressurizing chamber are in communication with the valve chamber, the valve body in the valve chamber is movable between an open position where the valve body opens the first inlet flow path and a closed position where the valve body closes the first inlet flow path, when the valve body is in the open position the pressurizing chamber is in communication with the second inlet flow path, the pressurizing chamber, the valve chamber, and the first inlet flow path are aligned along the direction of movement of the valve body, and the valve body in the open position is located between the pressurizing chamber and the first inlet flow path.

[0013] In one embodiment, the connection point between the outlet passage and the valve chamber is located between the pressurizing chamber and the first inlet passage. In one embodiment, the valve body has a recessed passage formed on its outer circumferential surface, and when the valve body is in the closed position, the second inlet passage and the outlet passage are in communication through the recessed passage. In one embodiment, the recessed channel has a cylindrical shape. In one embodiment, the flow path structure includes a cartridge that forms the valve chamber and a main body that houses the cartridge, and the cartridge is removable from the main body. In one embodiment, the cartridge is made of resin. In one embodiment, the valve body is made of metal. In one embodiment, the flow path switching device further includes a valve body guide that guides the movement of the valve body within the valve chamber.

[0014] In one aspect, a pump system is provided that includes a submerged pump for transferring liquefied gas, a suction vessel within which the submerged pump is housed, and the flow path switching device for preventing the submerged pump from idling.

Advantages of the Invention

[0015] Since the valve body is positioned between the pressurizing chamber and the first inlet flow path in the moving direction of the valve body, when the valve body is in the open position, the pressure of the liquefied gas in the pressurizing chamber applies a force toward the first inlet flow path to the valve body. When the operation of the pump connected to the first inlet flow path stops, the pressure of the liquefied gas in the first inlet flow path becomes smaller than the pressure of the liquefied gas in the pressurizing chamber. Due to this pressure difference, the valve body is pressed against the first inlet flow path, and the valve body becomes closed. Thus, the pressure of the liquefied gas in the pressurizing chamber can move the valve body to the closed position.

Brief Description of the Drawings

[0016] [Figure 1] It is a figure which shows one Embodiment of the pump system for transferring liquefied gas. [Figure 2] It is sectional drawing which shows one Embodiment of the detailed structure of a flow path switching device. [Figure 3] It is a perspective view of the valve body shown in FIG. 2. [Figure 4] It is an enlarged sectional view of the valve body shown in FIG. 2. [Figure 5] It is a figure which shows the state of a flow path switching device when a submerged pump is operating. [Figure 6] It is sectional drawing which shows other Embodiment of a flow path switching device. [Figure 7] FIGS. 7(a) and 7(b) are diagrams for explaining how to remove the cartridge forming the valve chamber from the main body. [Figure 8] It is sectional drawing which shows still another Embodiment of a flow path switching device. [Figure 9] It is a figure which shows the state of a flow path switching device when a submerged pump is operating. [Figure 10]This is a diagram showing an embodiment of a valve body that is a shuttle valve. [Figure 11] This is a diagram showing another embodiment of a valve body that is a shuttle valve. [Figure 12] This is a cross-sectional view showing yet another embodiment of a flow path switching device. [Figure 13] This is a cross-sectional view showing yet another embodiment of a flow path switching device. [Figure 14] This is a cross-sectional view taken along line A-A of FIG. 13. [Figure 15] FIG. 15(a) is a cross-sectional view showing yet another embodiment of a flow path switching device, and FIG. 15(b) is a cross-sectional view showing an embodiment of the valve body shown in FIG. 15(a). [Figure 16] This is a cross-sectional view showing yet another embodiment of a flow path switching device. [Figure 17] FIGS. 17(a) and 17(b) are diagrams for explaining the state of removing a cartridge forming a valve chamber from a main body portion. [Figure 18] This is a diagram showing a plurality of pumps connected in series. [Figure 19] This is a diagram showing the configuration of a conventional flow path switching device. [Figure 20] This is a diagram showing the state of a conventional flow path switching device when the pump is not operating. [Figure 21] This is a diagram showing the flow of liquefied gas when one of a plurality of pumps stops.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a pump system for transferring liquefied gas. Examples of liquefied gas transferred by the pump system shown in FIG. 1 include liquid hydrogen, liquid nitrogen, liquefied ammonia, liquefied natural gas, liquefied ethylene gas, liquefied petroleum gas, and the like.

[0018] As shown in Figure 1, the pump system comprises a submersible pump 1 for transferring liquefied gas, a suction container 2 in which the submersible pump 1 is housed, and a flow path switching device 5 for preventing the submersible pump 1 from running dry. The suction container 2 has a suction port 7 and a discharge port 8. Liquefied gas is introduced into the suction container 2 through the suction port 7, and the suction container 2 is filled with liquefied gas. During operation of the submersible pump 1, the entire submersible pump 1 is immersed in the liquefied gas. Therefore, the submersible pump 1 is configured to operate in liquefied gas.

[0019] The submersible pump 1 includes an electric motor 11 having a motor rotor 11A and a motor stator 11B, a rotating shaft 12 connected to the electric motor 11, bearings 14A, 14B, and 14C that rotatably support the rotating shaft 12, an impeller 15 fixed to the rotating shaft 12, and a pump casing 16 that houses the impeller 15. The flow path switching device 5 is located inside the suction container 2. More specifically, the flow path switching device 5 is connected to both the discharge port 1b of the submersible pump 1 and the discharge port 8 of the suction container 2. The specific configuration of the flow path switching device 5 will be described later.

[0020] When power is supplied to the electric motor 11 via a power cable (not shown), the electric motor 11 rotates the rotating shaft 12 and the impeller 15 together. As the impeller 15 rotates, the liquefied gas is drawn into the submersible pump 1 through the suction port 1a and discharged into the flow path switching device 5 through the discharge flow path 17 and discharge port 1b formed in the electric motor 11. Furthermore, the liquefied gas flows through the flow path switching device 5 and flows into the discharge port 8 of the suction container 2. A discharge pipe 20 is connected to the discharge port 8, and the liquefied gas that has flowed through the discharge port 8 is transferred through the discharge pipe 20.

[0021] A suction valve 22 is connected to the suction port 7, and a discharge valve 23 is connected to the discharge port 8. A drain line 25 is connected to the bottom of the suction container 2, and a drain valve 26 is connected to the drain line 25. The suction port 7 is located on the side wall of the suction container 2 and is positioned higher than the bottom of the suction container 2. The discharge port 8 is located on the top of the suction container 2 and is positioned higher than the suction port 7. While the submersible pump 1 is in operation, the suction valve 22 and discharge valve 23 are open, and the drain valve 26 is closed.

[0022] A vent line 27 is connected to the top of the suction container 2. During operation of the submersible pump 1, some of the liquefied gas vaporizes into gas due to the heat generated by the submersible pump 1, and this gas is discharged from the suction container 2 through the vent line 27. A vent valve 28 is connected to the vent line 27.

[0023] Figure 2 is a cross-sectional view showing one embodiment of the detailed configuration of the flow path switching device 5. As shown in Figure 2, the flow path switching device 5 comprises a flow path structure 40 having a first inlet flow path 31, a second inlet flow path 32, an outlet flow path 35, a valve chamber 37, and a pressurizing chamber 38, and a valve body 42 disposed within the valve chamber 37. The first inlet flow path 31 communicates with the discharge port 1b of the submersible pump 1, the second inlet flow path 32 communicates with the inside of the suction container 2, and the outlet flow path 35 communicates with the discharge port 8 of the suction container 2. The second inlet flow path 32 opens inside the suction container 2 and communicates with the suction port 7 through the inside of the suction container 2. The valve body 42 is arranged to selectively connect the outlet flow path 35 to either the first inlet flow path 31 or the second inlet flow path 32. The configuration of the flow path switching device 5 is not limited to the embodiment shown in Figure 2, as long as its intended function is achieved.

[0024] The first inlet passage 31, the second inlet passage 32, the outlet passage 35, and the pressurizing chamber 38 are in communication with the valve chamber 37. The pressurizing chamber 38 is in communication with the second inlet passage 32 through a connecting passage 45. Therefore, the liquefied gas in the suction container 2 is introduced into the pressurizing chamber 38 through the second inlet passage 32 and the connecting passage 45. The pressure of the liquefied gas in the pressurizing chamber 38 is the same as the pressure of the liquefied gas in the second inlet passage 32 and the suction container 2. The cross-sectional area of ​​the valve chamber 37 is larger than the cross-sectional area of ​​the first inlet passage 31. The valve body 42 is configured to selectively connect the outlet passage 35 to either the first inlet passage 31 or the second inlet passage 32. The valve body 42 in the valve chamber 37 is movable between an open position in which the valve body 42 opens the first inlet passage 31 and a closed position in which the valve body 42 closes the first inlet passage 31.

[0025] Figure 2 shows the state of the flow path switching device 5 when the submersible pump 1 is not operating. That is, the valve body 42 shown in Figure 2 is in the closed position. The end of the valve chamber 37 is composed of a valve seat 46, which surrounds the outlet of the first inlet flow path 31. As shown in Figure 2, when the valve body 42 is in the closed position, the valve body 42 is in surface contact with the valve seat 46, and thereby the valve body 42 closes the first inlet flow path 31.

[0026] The valve body 42 is a piston valve and is movable in the longitudinal direction of the valve chamber 37. The pressurizing chamber 38, the valve chamber 37, and the first inlet passage 31 are aligned along the direction of movement of the valve body 42. The valve chamber 37 is located between the pressurizing chamber 38 and the first inlet passage 31 in the direction of movement of the valve body 42. In the closed position, the valve body 42 is located between the pressurizing chamber 38 and the first inlet passage 31. The pressurizing chamber 38 opens at one end of the valve chamber 37, and the first inlet passage 31 opens at the opposite end of the valve chamber 37. The second inlet passage 32 opens on the side of the valve chamber 37, and the outlet passage 35 also opens on the side of the valve chamber 37. The connection point between the outlet passage 35 and the valve chamber 37 is located between the pressurizing chamber 38 and the first inlet passage 31. The connection position between the second inlet passage 32 and the valve chamber 37 is different from the connection position between the outlet passage 35 and the valve chamber 37 in the direction of movement of the valve body 42.

[0027] The force that moves the valve body 42 is generated by the pressure difference between the pressure of the liquefied gas in the pressurizing chamber 38 and the pressure of the liquefied gas in the first inlet passage 31. Specifically, when the pressure of the liquefied gas in the pressurizing chamber 38 is higher than the pressure of the liquefied gas in the first inlet passage 31, the pressure difference moves the valve body 42 toward the first inlet passage 31. On the other hand, when the pressure of the liquefied gas in the first inlet passage 31 is higher than the pressure of the liquefied gas in the pressurizing chamber 38, the pressure difference moves the valve body 42 toward the pressurizing chamber 38.

[0028] When the valve body 42 is in the closed position shown in Figure 2, the pressurizing chamber 38 is in communication with the second inlet passage 32 through the connecting passage 45. Therefore, the inside of the suction container 2 is in communication with the pressurizing chamber 38 through the second inlet passage 32. The pressure of the liquefied gas in the pressurizing chamber 38 acts on the valve body 42, generating a force in the direction of closing the valve body 42. The flow path switching device 5 of this embodiment has a spring 48 that pushes the valve body 42 toward the first inlet passage 31. This spring 48 is for assisting the movement of the valve body 42 toward the first inlet passage 31, and the force of the spring 48 does not need to be strong. As described above, the force that moves the valve body 42 is generated by the difference between the pressure of the liquefied gas in the pressurizing chamber 38 and the pressure of the liquefied gas in the first inlet passage 31, so in one embodiment, the spring 48 may not be necessary.

[0029] The valve body 42 has a recessed passage 50 formed on its outer circumferential surface. In this embodiment, the outer circumferential surface of the valve body 42 has a cylindrical shape, and this recessed passage 50 also has a cylindrical shape extending in the circumferential direction of the valve body 42. As shown in Figure 2, when the valve body 42 is in the closed position, the recessed passage 50 communicates with both the second inlet passage 32 and the outlet passage 35. Therefore, when the valve body 42 is in the closed position, the second inlet passage 32 and the outlet passage 35 are in communication through the recessed passage 50. The liquefied gas flows from the second inlet passage 32 through the recessed passage 50 to the outlet passage 35.

[0030] Figure 3 is a perspective view of the valve body 42 shown in Figure 2. The valve body 42 has a first flange 51 and a second flange 52 positioned at both ends thereof, and the recessed flow path 50 is located between the first flange 51 and the second flange 52. The outer circumferential surface 51a of the first flange 51 and the outer circumferential surface 52a of the second flange 52 are in contact with the wall surface of the flow path structure 40 that forms the valve chamber 37 shown in Figure 2. The valve body 42 has a hole 53 that opens at the end of the valve body 42 where the second flange 52 is formed. A spring 48 shown in Figure 2 is inserted into this hole 53. In one embodiment, the hole 53 may not be provided.

[0031] Figure 4 is an enlarged cross-sectional view of the valve body 42 shown in Figure 2. As shown in Figure 4, the valve body 42 has a first pressure-receiving surface S1 facing the first inlet passage 31 and a second pressure-receiving surface S2 facing the pressurizing chamber 38. When the submersible pump 1 is not operating, the pressure of the liquefied gas in the first inlet passage 31 is the same as the pressure of the liquefied gas in the pressurizing chamber 38. Even in this state, since the second pressure-receiving surface S2 is larger than the first pressure-receiving surface S1, the valve body 42 can maintain a closed position that closes the first inlet passage 31. The first flange 51 has a contact surface 51b that contacts the valve seat 46 shown in Figure 2. This contact surface 51b has the same shape as the valve seat 46. Therefore, the contact surface 51b can make surface contact with the valve seat 46.

[0032] Figure 5 shows the state of the flow path switching device 5 when the submersible pump 1 is in operation. That is, the valve body 42 shown in Figure 5 is in the open position. When the submersible pump 1 is in operation, liquefied gas is discharged from the discharge port 1b of the submersible pump 1 and flows into the first inlet flow path 31 of the flow path switching device 5. Since the pressure of the liquefied gas in the first inlet flow path 31 is higher than the pressure of the liquefied gas in the pressurizing chamber 38 (i.e., the pressure of the liquefied gas in the suction container 2), the valve body 42 moves toward the pressurizing chamber 38, opening the first inlet flow path 31 and closing the second inlet flow path 32 with the valve body 42. As a result, the first inlet flow path 31 and the outlet flow path 35 are in communication.

[0033] When the valve body 42 is in the open position, the second inlet passage 32 communicates with the recessed passage 50 of the valve body 42, but the recessed passage 50 does not communicate with the outlet passage 35 by the first flange 51 of the valve body 42. Therefore, the valve body 42 can close the second inlet passage 32. Since the outlet passage 35 extends from the side of the valve chamber 37, as shown in Figure 5, the valve body 42 in the open position does not obstruct the flow of liquefied gas. That is, the valve body 42 is not located in the flow of liquefied gas. Therefore, a smooth flow of liquefied gas from the first inlet passage 31 to the outlet passage 35 can be ensured.

[0034] As shown in Figure 5, when the valve body 42 is in the open position, the pressurizing chamber 38 is in communication with the second inlet passage 32. Therefore, the inside of the suction container 2 is in communication with the pressurizing chamber 38 through the second inlet passage 32. The pressure of the liquefied gas in the pressurizing chamber 38 acts on the valve body 42, generating a force that pushes the valve body 42 toward the first inlet passage 31.

[0035] Since the valve body 42 is located between the pressurizing chamber 38 and the first inlet passage 31 in the direction of movement of the valve body 42, when the valve body 42 is in the open position, the pressure of the liquefied gas in the pressurizing chamber 38 applies a force to the valve body 42 toward the first inlet passage 31. When the operation of the submersible pump 1 connected to the first inlet passage 31 stops, the pressure of the liquefied gas in the first inlet passage 31 decreases. As a result, as shown in Figure 2, the valve body 42 is pressed against the first inlet passage 31, and the valve body 42 becomes closed. The pressure of the liquefied gas in the pressurizing chamber 38 generates a force that moves the valve body 42 to the closed position.

[0036] As shown in Figure 18, when multiple submersible pumps connected in series are in operation, if one of them stops, the liquefied gas continues to flow to the stopped submersible pump because the other submersible pumps are still operating. Even in such cases, the flow path switching device 5 can quickly switch from the open state to the closed state.

[0037] In other words, when the submersible pump 1 stops operating in the open state shown in Figure 5, the liquefied gas continues to flow through the submersible pump 1 while it is stopped due to the operation of other submersible pumps connected to the suction port 7 or discharge port 8. However, as shown in Figure 1, several structural elements such as the impeller 15 are located inside the submersible pump 1 while it is stopped, resulting in pressure loss. As a result, the pressure of the liquefied gas in the first inlet passage 31 shown in Figure 5 becomes lower than the pressure of the liquefied gas in the pressurizing chamber 38. The difference between the pressure of the liquefied gas in the first inlet passage 31 and the pressure of the liquefied gas in the pressurizing chamber 38 causes the valve body 42 to move toward the first inlet passage 31, and the valve body 42 moves to the closed position shown in Figure 2. Thus, since the pressure of the liquefied gas in the pressurizing chamber 38 acts on the valve body 42 in the open position, the valve body 42 can be quickly moved to the closed position.

[0038] The pump system shown in Figure 1 is used for transferring cryogenic liquefied gases such as liquid hydrogen. Therefore, the flow path switching device 5 comes into contact with the cryogenic liquefied gas, and the flow path switching device 5 is also cooled to a cryogenic temperature. In order to ensure the operation of the flow path switching device 5, the flow path structure 40 and valve body 42 must be designed to minimize the effects of deformation due to temperature drop.

[0039] Therefore, the material constituting the valve body 42 has a coefficient of linear expansion that is the same as or smaller than that of the material constituting the flow channel structure 40. In one embodiment, the valve body 42 is made of a metal such as stainless steel, and the flow channel structure 40 is made of a resin such as polytetrafluoroethylene (PTFE). Generally, the coefficient of linear expansion of resin is greater than that of metal. When the flow channel structure 40 made of resin and the valve body 42 made of metal are cooled by liquefied gas, the flow channel structure 40 constituting the valve chamber 37 contracts more than the valve body 42. Therefore, the dimensions of the valve body 42 and the flow channel structure 40 at room temperature are designed so that the clearance between the flow channel structure 40 and the valve body 42 is optimal when the valve body 42 and the flow channel structure 40 are cooled by liquefied gas.

[0040] In other embodiments, the valve body 42 and the flow path structure 40 are made of the same material. For example, both the valve body 42 and the flow path structure 40 are made of a resin such as polytetrafluoroethylene (PTFE). In yet another embodiment, both the valve body 42 and the flow path structure 40 may be made of a metal such as stainless steel.

[0041] Figure 6 is a cross-sectional view showing another embodiment of the flow path switching device 5. The configuration of this embodiment, which is not specifically described, is the same as that of the embodiment described with reference to Figures 1 to 5, so the redundant description is omitted. The flow path structure 40 has a cartridge 54 that forms a valve chamber 37 and main body parts 40A and 40B that house the cartridge 54. The main body parts 40A and 40B are divisible into a first main body part 40A and a second main body part 40B. The cartridge 54 is removable from the main body parts 40A and 40B. The valve seat 46 is formed from a part of the cartridge 54.

[0042] In this embodiment, the cartridge 54 is made of a resin such as polytetrafluoroethylene (PTFE). Therefore, when wear of the cartridge 54 progresses due to sliding contact between the valve body 42 and the cartridge 54, the cartridge 54 can be removed from the main body parts 40A and 40B and a new cartridge 54 can be attached to the main body parts 40A and 40B.

[0043] Figures 7(a) and 7(b) illustrate the process of removing the cartridge 54, which forms the valve chamber 37, from the main body parts 40A and 40B. First, as shown in Figure 7(a), the second main body part 40B is separated from the first main body part 40A. Then, as shown in Figure 7(b), the cartridge 54, along with the valve body 42 and spring 48, is removed from the first main body part 40A. A new cartridge (not shown) is then inserted into the insertion hole 55 of the first main body part 40A and attached to the first main body part 40A.

[0044] This embodiment is suitable when the valve body 42 is made of metal. That is, the resin cartridge 54 is prone to wear due to sliding contact with the metal valve body 42. Therefore, when the cartridge 54 is excessively worn, the smooth movement of the valve body 42 can be ensured by replacing the cartridge 54 with a new one.

[0045] When the resin cartridge 54 and the metal valve body 42 are cooled by liquefied gas, the cartridge 54, which forms the valve chamber 37, contracts more than the valve body 42. The dimensions of the valve body 42 and cartridge 54 at room temperature are designed to optimize the clearance between the cartridge 54 and the valve body 42 when the valve body 42 and cartridge 54 are cooled by liquefied gas.

[0046] Figure 8 is a cross-sectional view showing yet another embodiment of the flow path switching device 5. The configuration of this embodiment, which is not specifically described, is the same as that of the embodiment described with reference to Figures 2 and 5, so a redundant explanation is omitted.

[0047] The flow path switching device 5 comprises a flow path structure 40 having a first inlet flow path 31, a second inlet flow path 32, an outlet flow path 35, a valve chamber 37, and a pressurizing chamber 38, and a valve body 60 located in the valve chamber 37. The first inlet flow path 31 communicates with the discharge port 1b of the submersible pump 1, the second inlet flow path 32 communicates with the inside of the suction container 2, and the outlet flow path 35 communicates with the discharge port 8 of the suction container 2. The second inlet flow path 32 opens inside the suction container 2 and communicates with the suction port 7 through the inside of the suction container 2.

[0048] The first inlet passage 31, the second inlet passage 32, the outlet passage 35, and the pressurizing chamber 38 are all connected to the valve chamber 37. The pressurizing chamber 38 is located between the second inlet passage 32 and the valve chamber 37, and the second inlet passage 32 is connected to the valve chamber 37 via the pressurizing chamber 38. Therefore, the liquefied gas in the suction container 2 is introduced into the pressurizing chamber 38 through the second inlet passage 32. The pressure of the liquefied gas in the pressurizing chamber 38 is the same as the pressure of the liquefied gas in the second inlet passage 32 and the suction container 2. The cross-sectional area of ​​the valve chamber 37 is larger than the cross-sectional area of ​​the first inlet passage 31. The valve body 60 is configured to selectively connect the outlet passage 35 to either the first inlet passage 31 or the second inlet passage 32. The valve body 60 in the valve chamber 37 is movable between an open position where the valve body 60 opens the first inlet passage 31 and a closed position where the valve body 60 closes the first inlet passage 31.

[0049] Figure 8 shows the state of the flow path switching device 5 when the submersible pump 1 is not operating. That is, the valve body 60 shown in Figure 8 is in the closed position. The end of the valve chamber 37 is composed of a valve seat 46, which surrounds the outlet of the first inlet flow path 31. As shown in Figure 8, when the valve body 60 is in the closed position, the valve body 60 is in surface contact with the valve seat 46, and thereby the valve body 60 closes the first inlet flow path 31.

[0050] The valve body 60 is a spherical shuttle valve and is movable in the longitudinal direction of the valve chamber 37. The pressurizing chamber 38, the valve chamber 37, and the first inlet passage 31 are aligned along the direction of movement of the valve body 60. The valve chamber 37 is located between the pressurizing chamber 38 and the first inlet passage 31 in the direction of movement of the valve body 60. In the closed position, the valve body 60 is located between the pressurizing chamber 38 and the first inlet passage 31. The pressurizing chamber 38 opens at one end of the valve chamber 37, and the first inlet passage 31 opens at the opposite end of the valve chamber 37. The second inlet passage 32 opens on the side of the pressurizing chamber 38, and the outlet passage 35 opens on the side of the valve chamber 37.

[0051] The force that moves the valve body 60 is generated by the pressure difference between the pressure of the liquefied gas in the pressurizing chamber 38 and the pressure of the liquefied gas in the first inlet passage 31. Specifically, when the pressure of the liquefied gas in the pressurizing chamber 38 is higher than the pressure of the liquefied gas in the first inlet passage 31, the pressure difference moves the valve body 60 toward the first inlet passage 31. On the other hand, when the pressure of the liquefied gas in the first inlet passage 31 is higher than the pressure of the liquefied gas in the pressurizing chamber 38, the pressure difference moves the valve body 60 toward the pressurizing chamber 38.

[0052] The pressurized chamber 38 is in communication with the second inlet passage 32. Therefore, the inside of the suction container 2 is in communication with the pressurized chamber 38 through the second inlet passage 32. The pressure of the liquefied gas in the pressurized chamber 38 acts on the valve body 60, generating a force in the direction of closing the valve body 60. The flow path switching device 5 of this embodiment does not have the spring 48 shown in Figure 2. As described above, the force that moves the valve body 60 is generated by the difference between the pressure of the liquefied gas in the pressurized chamber 38 and the pressure of the liquefied gas in the first inlet passage 31, so the valve body 60 can move between the closed position and the open position even without the spring 48. In one embodiment, the spring 48 shown in Figure 2 may be provided to assist the movement of the valve body 60.

[0053] As shown in Figure 8, when the valve body 60 is in the closed position, the second inlet passage 32 and the outlet passage 35 are in communication through the pressurizing chamber 38 and the valve chamber 37. The liquefied gas flows from the second inlet passage 32 through the pressurizing chamber 38 and the valve chamber 37 to the outlet passage 35.

[0054] Figure 9 shows the state of the flow path switching device 5 when the submersible pump 1 is in operation. That is, the valve body 60 shown in Figure 9 is in the open position. When the submersible pump 1 is in operation, liquefied gas is discharged from the discharge port 1b of the submersible pump 1 and flows into the first inlet flow path 31 of the flow path switching device 5. Since the pressure of the liquefied gas in the first inlet flow path 31 is higher than the pressure of the liquefied gas in the pressurizing chamber 38 (i.e., the pressure of the liquefied gas in the suction container 2), the valve body 60 moves toward the pressurizing chamber 38, opening the first inlet flow path 31 and closing the pressurizing chamber 38, which is connected to the second inlet flow path 32, with the valve body 60. As a result, the first inlet flow path 31 and the outlet flow path 35 are connected.

[0055] When the valve body 60 is in the open position, the second inlet passage 32 communicates with the pressurizing chamber 38, but since the pressurizing chamber 38 is blocked by the valve body 60, the pressurizing chamber 38 does not communicate with the valve chamber 37. Therefore, the valve body 60 can close the second inlet passage 32. Since the outlet passage 35 extends from the side of the valve chamber 37, as shown in Figure 9, the valve body 60 in the open position does not obstruct the flow of liquefied gas. That is, the valve body 60 is not located in the flow of liquefied gas. Therefore, a smooth flow of liquefied gas from the first inlet passage 31 to the outlet passage 35 can be ensured.

[0056] As shown in Figure 9, when the valve body 60 is in the open position, the pressurizing chamber 38 is in communication with the second inlet passage 32. Therefore, the inside of the suction container 2 is in communication with the pressurizing chamber 38 through the second inlet passage 32. The pressure of the liquefied gas in the pressurizing chamber 38 acts on the valve body 60, generating a force that directs the valve body 60 toward the first inlet passage 31.

[0057] Since the valve body 60 is located between the pressurizing chamber 38 and the first inlet passage 31, when the valve body 60 is in the open position, the pressure of the liquefied gas in the pressurizing chamber 38 applies a force to the valve body 60 toward the first inlet passage 31. When the operation of the submersible pump 1 connected to the first inlet passage 31 stops, the pressure of the liquefied gas in the first inlet passage 31 decreases. As a result, as shown in Figure 8, the valve body 60 is pressed against the first inlet passage 31, and the valve body 60 becomes closed. The pressure of the liquefied gas in the pressurizing chamber 38 generates a force that moves the valve body 60 to the closed position.

[0058] The shape of the valve body 60, which is a shuttle valve, is not limited to a spherical shape. For example, as shown in Figure 10, the valve body 60 may have a cylindrical shape. In another example, as shown in Figure 11, the valve body 60 may have a frustoconical valve head.

[0059] In one embodiment, to reduce the impact when the valve body 60 contacts the valve seat 46, the valve body 60 is made of a resin such as polytetrafluoroethylene (PTFE). Both the valve body 60 and the flow path structure 40 may be made of a resin such as polytetrafluoroethylene (PTFE). In one embodiment, to prevent changes in the clearance between the valve body 60 and the flow path structure 40 due to temperature decrease when the flow path switching device 5 comes into contact with liquefied gas, the valve body 60 and the flow path structure 40 are made of the same material.

[0060] In one embodiment, the valve body 60 may be made of a resin such as polytetrafluoroethylene (PTFE), and the flow channel structure 40 may be made of a metal such as stainless steel. However, as the temperature decreases, the valve body 60 made of resin shrinks more than the flow channel structure 40 made of metal. As a result, the clearance between the valve body 60 and the wall surface of the valve chamber 37 increases, which may impair the smooth movement of the valve body 60.

[0061] Therefore, as shown in Figure 12, the flow path switching device 5 may be equipped with a valve body guide 65 that guides the movement of the valve body 60 within the valve chamber 37. In the embodiment shown in Figure 12, the valve body guide 65 extends in the direction of movement of the valve body 60 and penetrates the valve body 60. One end of the valve body guide 65 is fixed to the flow path structure 40, and the other end of the valve body guide 65 is fixed to a support member 66 located in the first inlet flow path 31. The support member 66 is fixed to the flow path structure 40 and has a through hole (not shown) that allows the passage of liquefied gas. The valve body 60 moves along the valve body guide 65, thereby ensuring the smooth movement of the valve body 60.

[0062] Figure 13 shows another embodiment of the valve guide, and Figure 14 is a cross-sectional view taken along line AA of Figure 13. In this embodiment, the multiple valve guides 65 engage with guide grooves 68 formed on the outer circumferential surface of the valve body 60. The multiple valve guides 65 extend in the direction of movement of the valve body 60. Smooth movement of the valve body 60 is ensured as the valve body 60 moves along the valve guides 65. In the embodiments shown in Figures 13 and 14, two valve guides 65 are provided, but in other embodiments, three or more valve guides 65 may be provided.

[0063] Figure 15(a) is a cross-sectional view showing yet another embodiment of the flow path switching device 5, and Figure 15(b) is a cross-sectional view showing one embodiment of the valve body 60 shown in Figure 15(a). The configuration of this embodiment, which is not specifically described, is the same as that of the embodiment described with reference to Figures 8 to 11, so the redundant explanation is omitted.

[0064] In this embodiment, the valve body 60 (shuttle valve) has a hollow structure 71 made of a metal such as stainless steel and an outer layer 72 made of a resin such as polytetrafluoroethylene (PTFE). The outer layer 72 covers the outer surface of the hollow structure 71. In one example, the outer layer 72 can be formed by vapor-depositing resin onto the outer surface of the hollow structure 71.

[0065] To eliminate differences in thermal shrinkage, the flow channel structure 40 is made of the same type of resin as the outer layer 72. In one embodiment, the flow channel structure 40 and the outer layer 72 of the valve body 60 are made of polytetrafluoroethylene (PTFE). When the flow channel switching device 5 shrinks due to contact with liquefied gas, the clearance between the wall surface of the flow channel structure 40 constituting the valve chamber 37 and the valve body 60 does not change substantially. As a result, smooth movement of the valve body 60 is ensured.

[0066] Figure 16 is a cross-sectional view showing yet another embodiment of the flow path switching device 5. The configuration of this embodiment, which is not specifically described, is the same as that of the embodiment described with reference to Figures 8 to 11, so a redundant explanation is omitted. The flow path structure 40 has a cartridge 80 that forms a valve chamber 37 and main body parts 40A and 40B that house the cartridge 80. The main body part is divisible into a first main body part 40A and a second main body part 40B. The cartridge 80 is removable from the main body parts 40A and 40B. The valve seat 46 is formed from a part of the cartridge 80.

[0067] In this embodiment, the cartridge 80 is made of a resin such as polytetrafluoroethylene (PTFE). Therefore, when wear of the cartridge 80 progresses due to sliding contact between the valve body 60 and the cartridge 80, the cartridge 80 can be removed from the main body and a new cartridge 80 can be attached to the main body.

[0068] Figures 17(a) and 17(b) illustrate the process of removing the cartridge 80, which forms the valve chamber 37, from the main body. First, as shown in Figure 17(a), the second main body 40B is separated from the first main body 40A. Then, as shown in Figure 17(b), the cartridge 80, along with the valve body 60, is removed from the first main body 40A. A new cartridge (not shown) is then inserted into the insertion hole 82 of the first main body 40A and attached to the first main body 40A.

[0069] This embodiment is suitable when the valve body 60 is made of metal. That is, the resin cartridge 80 is prone to wear due to sliding contact with the metal valve body 60. Therefore, when the cartridge 80 becomes excessively worn, the smooth movement of the valve body 60 can be ensured by replacing the cartridge 80 with a new one.

[0070] When the resin cartridge 80 and the metal valve body 60 are cooled by liquefied gas, the cartridge 80, which forms the valve chamber 37, contracts more than the valve body 60. The dimensions of the valve body 60 and cartridge 80 at room temperature are designed to optimize the clearance between the cartridge 80 and the valve body 60 when the valve body 60 and cartridge 80 are cooled by liquefied gas.

[0071] In the embodiments described with reference to Figures 1 to 17, the flow path switching device 5 and the submersible pump 1 are vertically mounted. However, the arrangement of the flow path switching device 5 and the submersible pump 1 is not limited to these embodiments, and they may be arranged horizontally or diagonally. Even in this case, the valve bodies 42 and 60 can move between the open and closed positions depending on the difference between the pressure of the liquefied gas in the pressurizing chamber 38 and the pressure of the liquefied gas in the first inlet flow path 31.

[0072] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of symbols]

[0073] 1 Submersible pump 1a Inlet 1b Discharge port 2. Suction container 5. Flow path switching device 7. Intake port 8 Discharge Ports 11 Electric motor 11A Motor Rotor 11B Motor Stator 12 rotation axes 14A, 14B, 14C bearings 15 Impeller 16 Pump Casing 17 Discharge channel 20 Discharge pipe 22 Suction valve 23 Discharge valve 25 Drain Line 26 Drain valve 27 Ventline 28 Vent valve 31 1st inlet channel 32 2nd inlet channel 35 Outlet channel 37 Valve chambers 38 Pressurized chamber 40 Flow channel structure 40A, 40B Main Unit 42 Valve body 45 Connecting Channels 46 valve seats 48 springs 50 Recessed channel 51 First flange 51a Outer surface 51b Contact surface 52 Second flange 52a Outer surface 53 holes S1 First pressure-receiving surface S2 Second pressure-receiving surface 54 cartridges 55 Insertion hole 60 valve body 65 Valve body guide 66 Support Member 68 Guide grooves 71 Hollow structure 72 Outer layer 80 cartridges 82 Insertion holes

Claims

1. A flow path switching device for preventing dry running of a submersible pump used for transferring liquefied gas and located inside a suction container, A flow channel structure having a first inlet channel, a second inlet channel, an outlet channel, a valve chamber, and a pressurizing chamber, The valve chamber is provided with a valve body that selectively connects the outlet passage to either the first inlet passage or the second inlet passage. The first inlet passage, the second inlet passage, the outlet passage, and the pressurizing chamber are in communication with the valve chamber. The valve body within the valve chamber is movable between an open position in which the valve body opens the first inlet passage and a closed position in which the valve body closes the first inlet passage. When the valve body is in the open position, the pressurizing chamber is in communication with the second inlet passage. The pressurizing chamber, the valve chamber, and the first inlet passage are arranged along the direction of movement of the valve body. A flow path switching device in which the valve body in the open position is located between the pressurizing chamber and the first inlet flow path.

2. The flow path switching device according to claim 1, wherein the connection point between the outlet flow path and the valve chamber is located between the pressurizing chamber and the first inlet flow path.

3. The valve body has a recessed channel formed on its outer surface, The flow path switching device according to claim 1, wherein when the valve body is in the closed position, the second inlet flow path and the outlet flow path are in communication through the recessed flow path.

4. The channel switching device according to claim 3, wherein the recessed channel has a cylindrical shape.

5. The flow path structure comprises a cartridge forming the valve chamber and a main body in which the cartridge is housed, and the cartridge is removable from the main body, as described in claim 1.

6. The flow path switching device according to claim 5, wherein the cartridge is made of resin.

7. The flow path switching device according to claim 6, wherein the valve body is made of metal.

8. The flow path switching device according to claim 1, further comprising a valve body guide for guiding the movement of the valve body within the valve chamber.

9. A submersible pump for transferring liquefied gas, The aforementioned submersible pump is housed inside a suction container, A pump system comprising a flow path switching device according to any one of claims 1 to 8 for preventing the submersible pump from running dry.

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