Pump system

Abstract

A pump system according to the present disclosure comprises: a pump that is capable of pumping a low-temperature liquid by forward rotation, and that is incapable of reverse rotation; a liquid tank that can store the low-temperature liquid and causes the pump to be immersed in the low-temperature liquid; and a cooling liquid supply unit that can cause the pump to circulate the low-temperature liquid in a direction opposite the pumping direction. A single pump may be provided. Alternatively, a plurality of pumps may be provided.

Description

Pump System

[0001] This application claims priority to Japanese Patent Application No. 2024-122276, filed on July 29, 2024, the contents of which are incorporated herein by reference.

[0002] For example, Patent Document 1 discloses a pump device that pressurizes a cryogenic liquid to a pressure required on the demand side. The pump device includes a tank that stores the cryogenic liquid and a pump that is immersed in the cryogenic liquid in the tank. The pump sucks the cryogenic liquid from the tank and discharges it to a downstream pump device or the tank.

[0003] Japanese Patent Application Laid-Open No. 2023-173562

[0004] In order to operate a pump device such as that disclosed in Patent Document 1, the pump device must be pre-cooled or kept warm. Pre-cooling refers to lowering the temperature of the pump and tank from ambient temperature to an extremely low temperature at which the pump becomes a liquefied gas before the pump is operated. Keeping the pump and tank at a low temperature when the pump is stopped is another method of pre-cooling or keeping the pump warm. Flowing a cryogenic liquid through a stopped pump, however, can cause the pump's rotating shaft to rotate, potentially damaging the bearings.

[0005] The present disclosure has been made to solve the above-mentioned problems, and provides a pump system that enables quick pre-cooling and heat retention, and can avoid damage to the pump.

[0006] In order to solve the above problems, the pump system of the present disclosure includes a pump that can pump cryogenic liquid by rotating in the forward direction but cannot rotate in the reverse direction, a liquid tank that can store the cryogenic liquid and immerses the pump in the cryogenic liquid, and a cooling liquid supply unit that can circulate the cryogenic liquid through the pump in the direction opposite to the pumping direction.

[0007] The pump system of the present disclosure comprises a pump having a pump body capable of pumping cryogenic liquid when driven to rotate, and an electric motor that drives the pump body to rotate; a liquid tank capable of storing the cryogenic liquid and immersing the pump in the cryogenic liquid; a front-stage pump that is provided upstream of the pump and can sequentially supply the cryogenic liquid to the pump; and a control device that can control the electric motor of the pump, wherein the control device has a pumping control unit that controls the electric motor so that the pump pumps the cryogenic liquid, and a brake control unit that applies an electric brake to prevent the electric motor from rotating.

[0008] The pump system of the present disclosure allows for rapid pre-cooling and warming while avoiding damage to the pump.

[0009] FIG. 1 is a schematic configuration diagram of a pump system according to a first embodiment of the present disclosure. FIG. 2 is a schematic configuration diagram of a pump according to the first embodiment of the present disclosure. FIG. 3 is a diagram showing a switching mechanism according to a first modified example of the first embodiment of the present disclosure. FIG. 4 is a schematic configuration diagram of a pump system according to a second modified example of the first embodiment of the present disclosure. FIG. 5 is a schematic configuration diagram of a pump system according to a fifth modified example of the first embodiment of the present disclosure. FIG. 6 is a schematic configuration diagram of a pump system according to a sixth modified example of the first embodiment of the present disclosure. FIG. 7 is a schematic configuration diagram of a pump system according to a seventh modified example of the first embodiment of the present disclosure. FIG. 8 is a schematic configuration diagram of a pump system according to a second embodiment of the present disclosure. FIG. 9 is a functional block diagram of a control device according to the second embodiment of the present disclosure. FIG. 10 is a schematic configuration diagram of a pump system according to a first modified example of the second embodiment of the present disclosure. FIG. 11 is a schematic configuration diagram of a pump system according to a second modified example of the second embodiment of the present disclosure. FIG. 12 is a schematic configuration diagram of a pump system according to a third modified example of the second embodiment of the present disclosure. FIG. 13 is a functional block diagram of a control device according to a fourth modified example of the second embodiment of the present disclosure.

[0010] First Embodiment (Configuration of Pump System) A pump system 1 according to an embodiment of the present disclosure will be described below with reference to FIGS. 1 and 2. The pump system 1 shown in FIG. 1 is an apparatus that pressurizes a cryogenic liquid L to a target pressure and supplies the pressurized liquid L to equipment or plant equipment (not shown) that utilizes the pressurized cryogenic liquid L. The cryogenic liquid L is a liquefied gas, and in this embodiment, the cryogenic liquid L is liquefied hydrogen. Here, operation of the pump system 1 when the pump system 1 pressurizes the cryogenic liquid L is referred to as normal operation. Meanwhile, operation of the pump system 1 when the pump system 1 pre-cools or warms the pump 30 and the tank is simply referred to as "pre-cooling operation" or "warming operation." Pre-cooling refers to lowering the temperature of the pump 30 and the tank from ambient temperature to an extremely low temperature at which the pump 30 becomes a liquefied gas before operation of the pump 30. Warming refers to maintaining the pump 30 and the tank at a low temperature when the pump 30 is stopped. As shown in Figures 1 and 2, the pump system 1 includes a liquid tank 20, a pump 30, a connecting pipe 2, a supply source 3, a pump supply pipe 4, a pump discharge pipe 5, a cooling liquid supply unit 6, and a tank supply pipe 10.

[0011] (Liquid Tank) The liquid tank 20 is a container capable of storing the cryogenic liquid L. An example of the liquid tank 20 is a sump tank. The liquid tank 20 is thermally insulated, for example, by being covered with a heat insulating material. The liquid tank 20 has a liquid tank main body 21 and a flange 22. The liquid tank main body 21 opens upward. The flange 22 is provided at the top of the liquid tank 20. The flange 22 closes the opening of the liquid tank main body 21. In this embodiment, multiple liquid tanks 20 (three in this embodiment) are provided. The liquid tank 20 maintains a pump 30 (described later) at a low temperature by immersing the pump 30 in the cryogenic liquid L stored therein.

[0012] (Pump) A plurality of pumps 30 (three in this embodiment) are provided. In this embodiment, one pump 30 is housed in each liquid tank 20. The pumps 30 are suspended from the underside of the flange 22. Each pump 30 is immersed in the cryogenic liquid L in the liquid tank 20. The pumps 30 are rotary (turbo) type. Furthermore, the pumps 30 are capable of pumping the cryogenic liquid L by rotating forward, but are unable to rotate reversely. Here, the forward rotation of the pump 30 refers to the rotation of the pump 30 during normal operation, when the pump 30 pumps the cryogenic liquid L. The pump 30 and the liquid tank 20 housing the pump 30 constitute one pump device. Next, the detailed configuration of the pump 30 will be described. The pump 30 includes a pump casing 31 , a suction section 32 , a discharge section 33 , a rotating shaft 34 , a bearing 35 , a pump body 36 , an electric motor 37 , a discharge flow path 38 , and a reverse rotation prevention mechanism 40 .

[0013] (Pump Casing) The pump casing 31 is suspended from the underside of the flange 22. The pump casing 31 extends in the vertical direction. Most of the pump casing 31, except for its upper portion, is immersed in the cryogenic liquid L in the liquid device.

[0014] (Suction Portion) The suction portion 32 is provided at the bottom of the pump casing 31. The suction portion 32 sucks the cryogenic liquid L outside the pump casing 31 and supplies it to the inside of the pump casing 31.

[0015] (Discharge Portion) The discharge portion 33 is provided at the top of the pump casing 31. The discharge portion 33 discharges the cryogenic liquid L pressurized inside the pump casing 31 to the outside of the pump casing 31.

[0016] (Rotating Shaft) The rotating shaft 34 is housed in the pump casing 31. The rotating shaft 34 is disposed between the suction portion 32 and the discharge portion 33. The rotating shaft 34 extends in the vertical direction.

[0017] (Bearings) The bearings 35 rotatably support the rotating shaft 34. In the illustrated example, a radial bearing is used as the bearing 35. For example, one bearing 35 is provided at the top and one at the bottom of the electric motor 37, which will be described later. The upper bearing 35 also functions as a thrust bearing that receives thrust loads in the vertical direction (axial direction). Various types of bearings, such as rolling bearings and magnetic bearings, can be used for the bearings 35.

[0018] (Pump main body) The pump main body 36 is a part that can pump the cryogenic liquid L when driven to rotate. The pump main body 36 is provided directly above the suction section 32. The pump main body 36 includes a plurality of impellers 36a attached to the rotary shaft 34. The plurality of impellers 36a are arranged in a line in the vertical direction. As the plurality of impellers 36a rotate, the cryogenic liquid L that has been sucked into the pump casing 31 from the suction port is pressurized.

[0019] (Electric Motor) The electric motor 37 includes an electric motor 37 that drives the pump body 36 to rotate. The electric motor 37 here is a so-called main motor. The electric motor 37 is provided above the pump body 36. The electric motor 37 includes a stator and a rotor 37b. The stator is fixed to the pump casing 31 and generates a magnetic field. The rotor 37b is fixed to the outer peripheral surface of the rotating shaft 34 and receives the magnetic field from the stator to rotate integrally with the rotating shaft 34. The electric motor 37 rotates the rotating shaft 34, and the rotation of the rotating shaft 34 drives the pump body 36 to rotate.

[0020] (Discharge Flow Passage) The discharge flow passage 38 is provided, for example, inside the pump casing 31. The discharge flow passage 38 extends in the vertical direction and connects the pump main body 36 and the discharge portion 33. The discharge flow passage 38 guides the cryogenic liquid L pressurized by the pump main body 36 to the discharge portion 33.

[0021] (Reverse Rotation Prevention Mechanism) The reverse rotation prevention mechanism 40 prevents the pump 30 from rotating in a direction opposite to the forward rotation. That is, the reverse rotation prevention mechanism 40 exerts a rotation prevention locking function, thereby preventing reverse rotation of the pump 30. For example, the reverse rotation prevention mechanism 40 includes an inner circumferential member 41 and an outer circumferential member 42 fixed to the rotating shaft 34. When the pump 30 rotates forward, the reverse rotation prevention mechanism 40 separates the inner circumferential member 41 from the outer circumferential member 42 to prevent the rotation of the rotating shaft 34. When a force acts on the pump 30 to rotate it in a direction opposite to the forward rotation, the reverse rotation prevention mechanism 40 brings the inner circumferential member 41 and the outer circumferential member 42 into contact with each other to prevent the rotation of the rotating shaft 34. The reverse rotation prevention mechanism 40 can be, for example, a one-way clutch or a ratchet. Note that this configuration is merely an example of the configuration of the reverse rotation prevention mechanism 40, and the configuration of the reverse rotation prevention mechanism 40 can be selected as appropriate. Furthermore, although the reverse rotation prevention mechanism 40 is provided directly below the discharge portion 33, the location is not limited to this. The location of the reverse rotation prevention mechanism 40 can be changed as appropriate.

[0022] Returning to FIG. 1 , the pump system 1 employs a connection method in which multiple pumps 30 are connected in series. The pump system 1 uses the multiple pumps 30 to stepwise increase the pressure of the cryogenic liquid L. Of the multiple pumps 30, the pump 30 located on the lowest pressure side is referred to as the first stage, and the pumps 30 are referred to as the first, second, and third stages in order from the lowest pressure side. Similarly, the liquid tanks 20 in which the pumps 30 are housed are referred to as the first, second, and third stages in order from the lowest pressure side. Furthermore, the pump 30 and liquid tank 20 on the low-pressure side may be referred to as the preceding pump 30 and liquid tank 20, and the pump 30 and liquid tank 20 on the high-pressure side may be referred to as the following pump 30 and liquid tank 20.

[0023] (Connecting Pipe) The connecting pipe 2 connects the plurality of pumps 30 in series in the pumping direction of the cryogenic liquid L. The cryogenic liquid L can circulate through the connecting pipe 2. In this embodiment, in two pumps 30 connected in series, the discharge portion 33 of the low-pressure pump 30 and the suction portion 32 of the high-pressure pump 30 are directly connected by the connecting pipe 2. In this embodiment, one pump system 1 is provided with a plurality of connecting pipes 2. The discharge portion 33 of the first-stage pump 30 and the suction portion 32 of the second-stage pump 30 are directly connected by the connecting pipe 2. Furthermore, the discharge portion 33 of the second-stage pump 30 and the suction portion 32 of the third-stage pump 30 are directly connected by the connecting pipe 2.

[0024] The connecting pipe 2 extends upward from the discharge portion 33 of the low-pressure side pump 30. The connecting pipe 2 penetrates the flange 22 of the low-pressure side liquid tank 20 and is drawn out to the top of the liquid tank 20. The connecting pipe 2 penetrates the flange 22 of the high-pressure side liquid tank 20 and is introduced into the liquid tank 20. The downstream end of the connecting pipe 2 is connected to the suction portion 32 of the high-pressure side pump 30.

[0025] (Supply Source) The supply source 3 is a tank capable of storing the cryogenic liquid L. The supply source 3 stores the cryogenic liquid L to be supplied to the liquid tank 20 and the pump 30. For example, the cryogenic liquid L is supplied from the supply source 3 to the liquid tank 20 via a tank supply pipe 10 (not shown) that connects the supply source 3 and the liquid tank 20, and the cryogenic liquid L is supplied from the supply source 3 to the pump 30 via a pump supply pipe 4 that connects the supply source 3 and the pump 30.

[0026] (Pump Supply Pipe) The pump supply pipe 4 directly connects the supply source 3 and the suction section 32 of the first-stage pump 30. The pump supply pipe 4 supplies the low-pressure cryogenic liquid L stored in the supply source 3 to the first-stage pump 30.

[0027] (Pump Discharge Pipe) The pump discharge pipe 5 extends from the discharge portion 33 of the pump 30 (the third-stage pump 30 in this embodiment) on the highest pressure side among the multiple pumps 30. The pump discharge pipe 5 guides the cryogenic liquid L pressurized by the multiple pumps 30 to equipment or plant equipment (not shown) that utilizes the pressurized cryogenic liquid L.

[0028] (Cooling Liquid Supply Unit) The cooling liquid supply unit 6 is a mechanism that can circulate the cryogenic liquid L in the direction opposite to the pumping direction to the plurality of pumps 30 via the connecting pipes 2. The pumping direction here means the direction in which the cryogenic liquid L pressurized by the pumps 30 flows during normal operation. The pumping direction also means the direction in which the cryogenic liquid L flows from the pumps 30 on the low-pressure side toward the pumps 30 on the high-pressure side during normal operation. The cooling liquid supply unit 6 includes a front-stage pump 7, a cooling pipe 50, a relief pipe 8, a switching mechanism 60, and a check valve 9.

[0029] (Pre-stage Pump) The pre-stage pump 7 is provided in the pump supply pipe 4. The pre-stage pump 7 pumps the cryogenic liquid L from the supply source 3 toward the pump 30.

[0030] (Cooling Pipe) The cooling pipe 50 guides the cryogenic liquid L to the discharge portion 33 of the pump 30. The cooling pipe 50 is provided in a region of the pump supply pipe 4 downstream of the preceding pump 7. The cooling pipe 50 connects the pump supply pipe 4 and the pump discharge pipe 5. The cooling pipe 50 supplies the cryogenic liquid L for pre-cooling from the supply source 3 to the final-stage pump 30. The cryogenic liquid L supplied to the final-stage pump 30 is supplied to each pump 30 in order from the high-pressure side.

[0031] (Relief Pipe) The relief pipe 8 is provided on the pump supply pipe 4 downstream of the cooling pipe 50. During pre-cooling and heat retention operation, the relief pipe 8 flows from the high-pressure side to the low-pressure side and discharges the cryogenic liquid L that has passed through the multiple pumps 30 to the outside. In the illustrated example, the relief pipe 8 is connected to the supply source 3, and the cryogenic liquid L used for pre-cooling and heat retention is returned to the supply source 3. Note that the cryogenic liquid L after pre-cooling may be supplied to another mechanism or discarded.

[0032] (Switching Mechanism) The switching mechanism 60 is a mechanism that switches the flow direction of the cryogenic liquid L between normal operation of the pump system 1 and pre-cooling / heat-retention operation. The switching mechanism 60 opens the cooling pipe 50, thereby allowing the cryogenic liquid L to flow through the cooling pipe 50 in a direction opposite to the pumping direction of the pump 30. During normal operation, the switching mechanism 60 causes the cryogenic liquid L to flow in a direction from the low-pressure side pump 30 toward the high-pressure side pump 30. On the other hand, during pre-cooling / heat-retention operation, the switching mechanism 60 causes the cryogenic liquid L to flow in a direction from the high-pressure side pump 30 toward the low-pressure side pump 30. The switching mechanism 60 has a three-way valve 61, a discharge-side control valve 62, and a relief valve 63.

[0033] The three-way valve 61 is provided at the connection between the pump supply pipe 4 and the cooling pipe 50. The three-way valve 61 can open only one of the pump supply pipe 4 and the cooling pipe 50. During normal operation of the pump system 1, the three-way valve 61 opens the pump supply pipe 4 and closes the cooling pipe 50. On the other hand, during pre-cooling / heat retention operation of the pump system 1, the three-way valve 61 closes the pump supply pipe 4 and opens the cooling pipe 50.

[0034] The discharge side control valve 62 is provided in the pump discharge pipe 5. The discharge side control valve 62 opens and closes the pump discharge pipe 5. During normal operation of the pump system 1, the discharge side control valve 62 opens the pump discharge pipe 5. On the other hand, during pre-cooling / warming operation of the pump system 1, the discharge side control valve 62 closes the pump discharge pipe 5.

[0035] The relief valve 63 is provided in the relief pipe 8. In the illustrated example, the relief valve 63 is provided at the connection between the relief pipe 8 and the pump supply pipe 4. The relief valve 63 opens and closes the relief pipe 8. During normal operation of the pump system 1, the relief valve 63 closes the relief pipe 8. On the other hand, during pre-cooling / warming operation of the pump system 1, the relief valve 63 opens the relief pipe 8.

[0036] (Check Valve) The check valve 9 is provided in the pump supply pipe 4. The check valve 9 is provided downstream of the pre-stage pump 7 and upstream of the cooling pipe 50. The check valve 9 allows the cryogenic liquid L to flow from the supply source 3 to the pump 30, while preventing the cryogenic liquid L from flowing back from the pump 30 to the supply source 3.

[0037] (Operation of Pump System) The operation procedure of the pump system 1 is described below. The flow of the cryogenic liquid L during normal operation is indicated by solid arrows, and the flow of the cryogenic liquid L during pre-cooling and heat retention operation is indicated by dashed arrows. During normal operation, the three-way valve 61 opens the pump supply pipe 4 and closes the cooling pipe 50, the discharge control valve 62 opens the pump discharge pipe 5, and the relief valve 63 closes the relief pipe 8. As a result, the cryogenic liquid L supplied from the supply source 3 is pumped by the pre-stage pump 7 and supplied to the first-stage pump 30 without passing through the cooling pipe 50. The cryogenic liquid L is then pressurized in stages by the multiple pumps 30. The cryogenic liquid L discharged from the highest-pressure pump 30 is sent through the pump discharge pipe 5 to equipment or plant equipment (not shown) that utilizes the pressurized cryogenic liquid L. Note that during normal operation, the reverse rotation prevention mechanism 40 does not perform its rotation prevention locking function, allowing the pump 30 to pump the cryogenic liquid L without any problems.

[0038] During pre-cooling and heat-retention operation, with each pump 30 stopped, the three-way valve 61 closes the pump supply pipe 4 and opens the cooling pipe 50, the discharge control valve 62 closes the pump discharge pipe 5, and the relief valve 63 opens the relief pipe 8. This allows the cryogenic liquid L to be supplied to the pump 30 on the highest pressure side through the cooling pipe 50, and allows the cryogenic liquid L to circulate in a loop from the pump 30 on the highest pressure side toward the pump 30 on the lowest pressure side without being guided to the pump discharge pipe 5. The multiple pumps 30 are cooled by the cryogenic liquid L flowing back from the high-pressure side to the low-pressure side in this manner. At this time, the cryogenic liquid L flows in each pump 30 in the direction opposite to the pumping direction, but the reverse rotation prevention mechanism 40 provided in each pump 30 prevents the pump 30 from rotating reversely due to the cryogenic liquid L. The cryogenic liquid L sent to the first-stage pump 30 on the lowest pressure side is discharged to the outside through the relief pipe 8. In this embodiment, the gas is returned from the first stage pump 30 through the relief pipe 8 to the supply source 3 .

[0039] The opening and closing operations of the valves constituting the switching mechanism 60 may be performed manually by an operator or may be performed remotely by a computer or the like.

[0040] (Effects) The pump system 1 of this embodiment can achieve the following effects. In this embodiment, the pump system 1 includes a pump 30, a liquid tank 20, and a cooling liquid supply unit 6. The pump 30 is capable of pumping the cryogenic liquid L by rotating forward and is not capable of rotating reversely. The liquid tank 20 is capable of storing the cryogenic liquid L, and the pump 30 is immersed in the cryogenic liquid L. The cooling liquid supply unit 6 is capable of circulating the cryogenic liquid L through the pump 30 in the direction opposite to the pumping direction.

[0041] As a result, the pump system 1 can supply the cryogenic liquid L to the pump 30 in the direction opposite to the pumping direction during pre-cooling or warming. Because the pump 30 is designed to be non-reverse rotatable, the flow of the cryogenic liquid L will not cause the pump 30 to rotate during pre-cooling or warming. In other words, the bearing 35 will not be damaged by the unintended flow of the cryogenic liquid L on the rotating shaft 34. This enables rapid pre-cooling and warming, and prevents damage to the pump 30. Furthermore, the life of the bearing 35 is extended by reducing damage and load on the bearing 35. This allows for longer maintenance intervals. In some cases, pre-cooling after warming is not necessary, which shortens the plant startup time and reduces the amount of gasification (boil-off gas) that occurs during re-pre-cooling.

[0042] In this embodiment, a plurality of pumps 30 are provided, and are immersed in the cryogenic liquid L in the liquid tank 20. The cooling liquid supply unit 6 is capable of circulating the cryogenic liquid L through the plurality of pumps 30 in the direction opposite to the pumping direction.

[0043] This allows the pump system 1 to quickly pre-cool and keep warm the multiple pumps 30, while also preventing damage to each pump 30.

[0044] In this embodiment, the pump system 1 includes a connecting pipe 2 that connects multiple pumps 30 in series in the pumping direction of the cryogenic liquid L. The cooling liquid supply unit 6 is capable of circulating the cryogenic liquid L through the multiple pumps 30 via the connecting pipe 2 in the direction opposite to the pumping direction.

[0045] As a result, the pump system 1 can supply the cryogenic liquid L in the direction opposite to the pumping direction to the multiple pumps 30 connected by the connecting pipes 2. Therefore, according to the pump system 1 of this embodiment, pre-cooling and warming of the multiple pumps 30 can be performed collectively. Therefore, even if the multiple pumps 30 are connected in series as in this embodiment, it is possible to quickly cool each pump 30, making it easy to perform pre-cooling and warming operations before starting up the pump system 1.

[0046] In this embodiment, the cooling liquid supply unit 6 includes a cooling pipe 50 and a switching mechanism 60. The cooling pipe 50 guides the cryogenic liquid L to the discharge portion 33 of the pump 30. The switching mechanism 60 opens the cooling pipe 50, thereby allowing the cryogenic liquid L to flow through the cooling pipe 50 in a direction opposite to the pumping direction of the pump 30.

[0047] This allows the cooling liquid supply unit 6 to be provided with a relatively simple configuration.

[0048] In this embodiment, the cooling liquid supply unit 6 has a relief pipe 8 that discharges the cryogenic liquid L that flows from the high-pressure side to the low-pressure side and passes through the pump 30 to the outside during pre-cooling and heat-retention operation. The switching mechanism 60 has a relief valve 63 that opens and closes the relief pipe 8. The relief pipe 8 is connected to the supply source 3.

[0049] This allows the cryogenic liquid L used for pre-cooling and warming to be returned to the supply source 3. Therefore, the utilization efficiency of the cryogenic liquid L can be improved.

[0050] (First Modification) Next, a first modification will be described. In this modification, as shown in FIG. 3 , the switching mechanism 60 has a first control valve 64 and a second control valve 65 instead of the three-way valve 61. The first control valve 64 is provided in the pump supply pipe 4, and is installed downstream of the cooling pipe 50 and upstream of the relief pipe 8. The first control valve 64 opens and closes the pump supply pipe 4. The second control valve 65 is provided in the cooling pipe 50, and opens and closes the cooling pipe 50. During normal operation, the first control valve 64 opens the pump supply pipe 4, and the second control valve 65 closes the cooling pipe 50. On the other hand, during pre-cooling and heat retention operation, the first control valve 64 closes the pump supply pipe 4, and the second control valve 65 opens the cooling pipe 50. Examples of the first control valve 64 and the second control valve 65 include a gate valve and a globe valve.

[0051] The number of pumps 30 and liquid tanks 20 can be changed as appropriate. One or two pumps 30 and liquid tanks 20, or four or more pumps 30 and liquid tanks 20 may be provided.

[0052] (Second Modification) Next, a second modification will be described. In this modification, only one pump 30 and one liquid tank 20 are provided in the pump system 1, as shown in FIG.

[0053] (Third Modification) Next, a third modification will be described. In this modification, only one liquid tank 20 is provided, and multiple pumps 30 are immersed in the cryogenic liquid L within the single liquid tank 20, as shown in FIG.

[0054] (Fourth Modification) Next, a fourth modification will be described. In this modification, as shown in FIG. 6 , a plurality of pumps 30 are connected in parallel via a pump supply pipe 4 and a pump discharge pipe 5. In the illustrated example, the pump supply pipe 4 branches into a first pump supply pipe 4a and a second pump supply pipe 4b downstream of the check valve 9. As in the above-described embodiment, the first pump supply pipe 4a is connected to a plurality of pumps 30 connected in series via a connecting pipe 2. The second pump supply pipe 4b is connected to a single pump 30. Furthermore, the pump discharge pipe 5 branches into a first pump discharge pipe 5a and a second pump discharge pipe 5b. The first pump discharge pipe 5a is connected to the plurality of pumps 30 connected to the first pump supply pipe 4a. The second pump discharge pipe 5b is connected to the pump 30 connected to the second pump supply pipe 4b. In this way, the group of pumps 30 connected to the first pump supply pipe 4a and the pump 30 connected to the second pump supply pipe 4b are connected in parallel. In addition, a single pump 30 may be connected to the first pump supply pipe 4a instead of a group of multiple pumps 30, and conversely, a plurality of pumps 30 connected in series may be connected to the second pump supply pipe 4b instead of a single pump 30.

[0055] A cooling pipe 50 is provided on each of the branched pump supply pipes 4. One cooling pipe 50 connects the first pump supply pipe 4a and the first pump discharge pipe 5a, and another cooling pipe 50 connects the second pump supply pipe 4b and the second pump discharge pipe 5b. A valve mechanism is provided for each group of pumps 30 connected in parallel. That is, one three-way valve 61 and one relief valve 63 are provided on each of the first pump supply pipe 4a and the second pump supply pipe 4b, and one discharge-side control valve 62 is provided on each of the first pump discharge pipe 5a and the second pump discharge pipe 5b.

[0056] (Fifth Modification) Next, a fifth modification will be described. In this modification, as shown in FIG. 7 , a cooling liquid supply unit 6 is provided to be able to circulate the cryogenic liquid L to each of a plurality of pumps 30 connected in series by connecting pipes 2. The cooling pipe 50 has a main cooling pipe 51 and a branch cooling pipe 52. The main cooling pipe 51 connects the pump supply pipe 4 and the pump discharge pipe 5. The branch cooling pipe 52 branches off from the main cooling pipe 51 and supplies the cryogenic liquid L to each pump 30 except for the pump 30 on the highest pressure side. The branch cooling pipe 52 is provided for each corresponding pump 30. In the illustrated example, the branch cooling pipe 52 is provided for each connecting pipe 2 and is connected to the connecting pipe 2 downstream of each pump 30 during normal operation.

[0057] The cooling liquid supply unit 6 further includes a second check valve 11 and a return pipe 55. One second check valve 11 is provided for each connecting pipe 2. The second check valve 11 allows the cryogenic liquid L to flow from the low-pressure side to the high-pressure side during normal operation, while preventing backflow (flow from the high-pressure side to the low-pressure side) of the cryogenic liquid L during pre-cooling and heat-retention operation. The return pipe 55 returns the cryogenic liquid L from each pump 30 in the second stage and subsequent stages to the supply source 3 during pre-cooling and heat-retention operation. The return pipe 55 includes a main return pipe 56 and a branch return pipe 57. The main return pipe 56 extends from the supply source 3. One branch return pipe 57 is provided for each connecting pipe 2. The branch return pipe 57 connects the corresponding connecting pipe 2 and the main return pipe 56. The branch return pipe 57 is provided downstream of the second check valve 11 provided for the corresponding connecting pipe 2 during normal operation.

[0058] The switching mechanism 60 also has a branch control valve 66 and a return control valve 67. The branch control valve 66 is provided in each cooling branch pipe 52. The branch control valve 66 opens and closes the cooling branch pipe 52. During normal operation, the branch control valve 66 closes the cooling branch pipe 52, and during pre-cooling and heat retention operation, the branch control valve 66 opens the cooling branch pipe 52. The return control valve 67 is provided in the return branch pipe 57. The return control valve 67 opens and closes the return branch pipe 57. During normal operation, the return control valve 67 closes the return branch pipe 57, and during pre-cooling and heat retention operation, the return control valve 67 opens the return branch pipe 57.

[0059] In this modification, the pump system 1 can supply the cryogenic liquid L to each of the pumps 30 connected in series. This improves the cooling efficiency. Note that each cooling branch pipe 52 may be provided so that other pumps 30 that require pre-cooling or heat retention are connected in series. This modification will be described in the sixth modification below.

[0060] (Sixth Modification) Next, a sixth modification will be described. In this modification, as shown in FIG. 8 , similar to the fourth modification described above, a group of pumps 30 are connected in parallel by a pump supply pipe 4 and a pump discharge pipe 5. Also, similar to the fifth modification described above, only one cooling pipe 50 is provided, and the cooling pipe 50 includes a main cooling pipe 51 and branch cooling pipes 52. Some of the multiple branch cooling pipes 52 (in the illustrated example, the branch cooling pipe 52 corresponding to the first-stage pump 30) are provided with other pumps 30 connected in parallel to the corresponding pumps 30. In other words, the multiple pumps 30 are connected in series by some of the branch cooling pipes 52. Also, similar to the fifth modification, the cooling liquid supply unit 6 further includes a second check valve 11 and a return pipe 55, and the switching mechanism 60 further includes a branch control valve 66 and a return control valve 67.

[0061] In the above-described first embodiment and each modified example of the first embodiment, the case where the check valve 9 is provided in the pump supply pipe 4 has been described, but the check valve 9 does not have to be provided. In the case where the check valve 9 is provided, the check valve 9 can prevent backflow of the cryogenic liquid L from the pump 30 to the supply source 3 during pre-cooling and heat retention operations.

[0062] (Seventh Modification) Next, a seventh modification will be described. In this modification, the check valve 9 is not provided. Similarly to the first modification (see FIG. 3 ), the switching mechanism 60 includes a first control valve 64 and a second control valve 65 instead of the three-way valve 61. The switching mechanism 60 also includes a third control valve 68. The third control valve 68 is located downstream of the second control valve 65 on the cooling pipe 50. The third control valve 68 opens and closes the cooling pipe 50. During normal operation, the first control valve 64 opens the pump supply pipe 4, and the second control valve 65 and the third control valve 68 close the cooling pipe 50. During pre-cooling and heat retention operation, the first control valve 64 closes the pump supply pipe 4, and the second control valve 65 and the third control valve 68 open the cooling pipe 50. Examples of the third control valve 68 include a gate valve and a globe valve.

[0063] According to this modification, during pre-cooling and normal operation, the cooling pipe 50 can be doubly blocked by the second control valve 65 and the third control valve 68. This more reliably prevents leakage of the cryogenic liquid L. Furthermore, the number of valves provided in the cooling pipe 50 can be changed as appropriate, and the cooling pipe 50 may be provided with three or more valves.

[0064] In the first embodiment and each modified example of the first embodiment, the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 are directly connected to the suction portion 32 of the pump 30, but this is not limited to this. "Pumps 30 connected in series" includes not only cases where the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 are directly connected to the suction portion 32 of the pump 30, but also cases where the downstream ends of the pump supply pipe 4 and the connecting pipe 2 are simply disposed in the liquid tank 20 but are separated from the suction portion 32 and are indirectly connected to the suction portion 32. That is, as long as the cryogenic liquid L can flow from the high-pressure side pump 30 to the low-pressure side pump 30 solely by the pumping force of the preceding pump 7 during pre-cooling and insulation operation, and within one pump 30, the cryogenic liquid L can flow from the discharge portion 33 to the suction portion 32, the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 can be simply disposed in the liquid tank 20 but are separated from the suction portion 32 and are indirectly connected to the suction portion 32.

[0065] Second Embodiment (Configuration of Pump System) A pump system 101 according to an embodiment of the present disclosure will now be described with reference to Figures 10 to 12. As shown in Figure 10, the pump system 101 includes a liquid tank 20, a pump 30, a connecting pipe 2, a supply source 3, a pump supply pipe 4, a pump discharge pipe 5, a pre-pump 7, a check valve 9, a tank supply pipe 10, and a control device 80.

[0066] (Pump) A plurality of pumps 30 (three in this embodiment) are provided. Each pump 30 is immersed in the cryogenic liquid L in the liquid tank 20. The pump 30 includes a pump casing 31, a suction section 32, a discharge section 33, a rotating shaft 34, a bearing 35, a pump body 36, an electric motor 37, a discharge flow path 38, and an electric brake 70.

[0067] (Electric Brake) The electric brake 70 is controlled by the control device 80 (described later) and is a mechanism that brakes the electric motor 37 to disable rotation during pre-cooling and heat-retention operations. For example, the electric brake 70 includes a movable part 71 fixed to the rotating shaft 34 and a stationary part 72 fixed to the pump casing 31. The movable part 71 rotates integrally with the rotating shaft 34. A coil is built into the stationary part 72. When the electric brake 70 is activated, the coil is energized, and the movable part 71 is attracted by the electromagnetic force of the coil. This causes the movable part 71 to adhere to the stationary part 72, and the rotating shaft 34 is braked by friction and magnetic force. In this way, the electric motor 37 is braked, and the electric motor 37 is disabled from rotating. Note that this electric brake 70 is an example of a so-called electromagnetic brake. The electric brake 70 can be selected as appropriate. Although the electric brake 70 is provided directly below the discharge part 33, this is not a limitation. The location of the electric brake 70 can be changed as appropriate.

[0068] (Pre-Pump) The pre-pump 7 is provided upstream of the plurality of pumps 30 and is capable of sequentially supplying the cryogenic liquid L to the plurality of pumps 30 via the connecting pipe 2 .

[0069] (Control Device) The control device 80 can control the electric motor 37 of each pump 30. The control device 80 has functional units, a pumping control unit 81 and a brake control unit 82. The pumping control unit 81 controls the electric motor 37 so that the pump 30 pumps the cryogenic liquid L. The brake control unit 82 operates the electric brake 70, thereby applying the electric brake 70 so that the electric motor 37 cannot rotate. The brake control unit 82 controls the electric brake 70 by, for example, an inverter disposed outside the pump 30.

[0070] (Operation of Pump System) The operation procedure of the pump system 101 will be described below. The flow of the cryogenic liquid L during normal operation and during pre-cooling / warming operation is indicated by solid arrows. During normal operation, the pre-stage pump 7 pumps the cryogenic liquid L from the supply source 3 to the first-stage pump 30. The pumping control unit 81 then operates the electric motors 37 of each pump 30. As a result, the cryogenic liquid L supplied to the first-stage pump 30 is pressurized in stages by the multiple pumps 30. The cryogenic liquid L discharged from the pump 30 with the highest pressure is sent through the pump discharge pipe 5 to equipment or plant equipment (not shown) that utilizes the pressurized cryogenic liquid L.

[0071] During pre-cooling and heat retention operation, first, with each pump 30 stopped, the brake control unit 82 operates the electric brakes 70 of all pumps 30 and applies the electric brakes 70 so that the electric motors 37 of each pump 30 are all unable to rotate. With the electric brakes 70 applied to each electric motor 37, the preceding pump 7 supplies cryogenic liquid L to the first-stage pump 30. The cryogenic liquid L supplied to the first-stage pump 30 is sent via the connecting pipe 2 to the second-stage, third-stage, and high-pressure pumps 30 in this order. In this way, the multiple pumps 30 are cooled by the cryogenic liquid L. At this time, the cryogenic liquid L flows through each pump 30, but because the electric brakes 70 are applied to the electric motors 37 of each pump 30, the pumps 30 are prevented from rotating by the cryogenic liquid L.

[0072] (Operations and Effects) The pump system 101 of the present embodiment can achieve the following operations and effects. In the present embodiment, the pump system 101 includes a pump 30 having a pump main body 36 that can be rotationally driven to pump the cryogenic liquid L and an electric motor 37 that rotationally drives the pump main body 36, a liquid tank 20 that can store the cryogenic liquid L and in which the pump 30 is immersed in the cryogenic liquid L, an upstream pump 7 that is provided upstream of the pump 30 and can sequentially supply the cryogenic liquid L to the pump 30, and a control device 80 that can control the electric motor 37 of the pump 30, and the control device 80 includes a pumping control unit 81 that controls the electric motor 37 so that the pump 30 pumps the cryogenic liquid L, and a brake control unit 82 that applies an electric brake 70 to disable the electric motor 37 from rotating.

[0073] As a result, during pre-cooling or warming, the pump system 101 can operate the upstream pump 7 while applying the electric brake 70 to the pump 30 to pump the cryogenic liquid L to the pump 30. This prevents the pump 30 from rotating due to the flow of the cryogenic liquid L during pre-cooling or warming. In other words, the bearing 35 is not damaged by the unintended flow of the cryogenic liquid L on the rotating shaft 34. This enables rapid pre-cooling and warming, and prevents damage to the pump 30. Furthermore, the life of the bearing 35 is extended by reducing damage and load on the bearing 35. This allows for longer maintenance intervals. In some cases, pre-cooling after warming is not necessary, which shortens the plant startup time and reduces the amount of gasification (boil-off gas) that occurs during re-pre-cooling.

[0074] In this embodiment, a plurality of pumps 30 are provided and are immersed in the cryogenic liquid L in the liquid tank 20, and the control device 80 is capable of controlling the electric motor 37 of each pump 30.

[0075] This allows the pump system 101 to quickly pre-cool and keep warm the multiple pumps 30, while preventing damage to each pump 30.

[0076] In this embodiment, a connecting pipe 2 is provided that connects multiple pumps 30 in series in the direction of pumping the cryogenic liquid L, and the pre-stage pump 7 is provided upstream of the multiple pumps 30 and is capable of sequentially supplying the cryogenic liquid L to the multiple pumps 30 via the connecting pipe 2.

[0077] As a result, the pump system 101 can supply the cryogenic liquid L to the plurality of pumps 30 connected by the connecting pipe 2 while applying the electric brake 70. Therefore, according to the pump system 101 of this embodiment, pre-cooling and heat retention of the plurality of pumps 30 can be performed collectively. Therefore, even if the plurality of pumps 30 are connected in series as in this embodiment, it is possible to quickly cool each pump 30, and pre-cooling and heat retention operations before start-up of the pump system 101 are facilitated.

[0078] (First Modification) Next, a first modification will be described. In this modification, only one pump 30 and one liquid tank 20 are provided in a pump system 101, as shown in FIG.

[0079] 14 , only one liquid tank 20 is provided, and multiple pumps 30 are immersed in the cryogenic liquid L within the single liquid tank 20.

[0080] (Third Modification) Next, a third modification will be described. In this modification, as shown in FIG. 15 , a plurality of pumps 30 are connected in parallel via a pump supply pipe 4 and a pump discharge pipe 5. In the illustrated example, the pump supply pipe 4 branches into a first pump supply pipe 4a and a second pump supply pipe 4b downstream of the check valve 9. As in the above-described embodiment, the first pump supply pipe 4a is connected to a plurality of pumps 30 connected in series via a connecting pipe 2. The second pump supply pipe 4b is connected to a single pump 30. The pump discharge pipe 5 branches into a first pump discharge pipe 5a and a second pump discharge pipe 5b. The first pump discharge pipe 5a is connected to the plurality of pumps 30 connected to the first pump supply pipe 4a. The second pump discharge pipe 5b is connected to the pump 30 connected to the second pump supply pipe 4b. In this way, the group of pumps 30 connected to the first pump supply pipe 4a and the pump 30 connected to the second pump supply pipe 4b are connected in parallel. In addition, a single pump 30 may be connected to the first pump supply pipe 4a instead of a group of multiple pumps 30, and conversely, a plurality of pumps 30 connected in series may be connected to the second pump supply pipe 4b instead of a single pump 30.

[0081] (Fourth Modification) Next, a fourth modification will be described. In this modification, as shown in Fig. 16 , the control device 80 may further include a functional unit of a front-stage pump control unit 83. When the brake control unit 82 applies the electric brake, the front-stage pump control unit 83 causes the front-stage pump 7 to rotate at a lower rotation speed compared to when the brake control unit 82 does not apply the electric brake. The front-stage pump control unit 83 may be installed in a control device separate from the control device 80 that has the pumping control unit 81 and the brake control unit 82.

[0082] In this modification, during pre-cooling / heat-retention operation, the pump system 101 can operate the upstream pump 7 at a lower rotation speed than during normal operation in a pre-cooling mode or a heat-retention mode. This allows the cryogenic liquid L to circulate without rotating the pump 30 during pre-cooling / heat-retention operation. This further reduces the risk of damage to the pump 30.

[0083] In the second embodiment and each modified example of the second embodiment, the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 are directly connected to the suction portion 32 of the pump 30, but this is not limited to this. "Pumps 30 connected in series" includes not only cases where the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 are directly connected to the suction portion 32 of the pump 30, but also cases where the downstream ends of the pump supply pipe 4 and the connecting pipe 2 are simply disposed in the liquid tank 20 but are separated from the suction portion 32 and are indirectly connected to the suction portion 32. That is, as long as the cryogenic liquid L can flow from the low-pressure side pump 30 to the high-pressure side pump 30 solely by the pumping force of the preceding pump 7 during pre-cooling and heat retention operation, and within one pump 30, the cryogenic liquid L can flow from the suction portion 32 to the discharge portion 33, the downstream end of the pump supply pipe 4 and the downstream end of the connecting pipe 2 can be simply disposed in the liquid tank 20 but are separated from the suction portion 32 and are indirectly connected to the suction portion 32.

[0084] (Other Embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope that does not deviate from the gist of the present disclosure are also included.

[0085] In the above embodiment, the cryogenic liquid L is liquid hydrogen, but this is not limiting. For example, the cryogenic liquid L may be liquefied natural gas, liquid helium, or liquid ammonia.

[0086] <Additional Notes> The pump system 1 described in each embodiment can be understood, for example, as follows.

[0087] (1) The pump system 1 according to the first aspect comprises a pump 30 that can pump cryogenic liquid L by rotating in the forward direction but cannot rotate in the reverse direction, a liquid tank 20 that can store the cryogenic liquid L and immerses the pump 30 in the cryogenic liquid L, and a cooling liquid supply unit 6 that can circulate the cryogenic liquid L through the pump 30 in the direction opposite to the pumping direction.

[0088] As a result, the pump system 1 can supply the cryogenic liquid L to the pump 30 in the direction opposite to the pumping direction during pre-cooling or warming. Because the pump 30 is not reversible, the flow of the cryogenic liquid L will not cause the pump 30 to rotate during pre-cooling or warming. This allows for rapid pre-cooling and warming, and prevents damage to the pump 30.

[0089] (2) A second aspect of the pump system 1 is the pump system 1 of (1), in which a plurality of pumps 30 are provided and immersed in the cryogenic liquid L in the liquid tank 20, and the cooling liquid supply unit 6 may be capable of circulating the cryogenic liquid L through the plurality of pumps 30 in a direction opposite to the pumping direction.

[0090] This allows the pump system 1 to quickly pre-cool and keep warm the multiple pumps 30, while also preventing damage to each pump 30.

[0091] (3) A third aspect of the pump system 1 is the pump system 1 of (2), which includes a connecting pipe 2 that connects multiple pumps 30 in series in the pumping direction of the cryogenic liquid L, and the cooling liquid supply unit 6 may be capable of circulating the cryogenic liquid L to the multiple pumps 30 via the connecting pipe 2 in the direction opposite to the pumping direction.

[0092] As a result, the pump system 1 can supply the cryogenic liquid L in the direction opposite to the pumping direction to the multiple pumps 30 connected by the connecting pipes 2. Therefore, according to the pump system 1 of this aspect, the multiple pumps 30 can be pre-cooled and kept warm all at once.

[0093] (4) The pump system 101 relating to the fourth aspect comprises a pump 30 having a pump body 36 that can be driven to rotate to pump the cryogenic liquid L, and an electric motor 37 that drives the pump body 36 to rotate; a liquid tank 20 that can store the cryogenic liquid L and immerse the pump 30 in the cryogenic liquid L; a front-stage pump 7 that is provided upstream of the pump 30 and can sequentially supply the cryogenic liquid L to the pump 30; and a control device 80 that can control the electric motor 37 of the pump 30, wherein the control device 80 has a pumping control unit 81 that controls the electric motor 37 so that the pump 30 pumps the cryogenic liquid L, and a brake control unit 82 that applies an electric brake 70 so that the electric motor 37 cannot rotate.

[0094] As a result, during pre-cooling or warming, the pump system 101 can operate the upstream pump 7 while applying the electric brake 70 to the pump 30, thereby pumping the cryogenic liquid L to the pump 30. As a result, the pump 30 will not rotate due to the flow of the cryogenic liquid L during pre-cooling or warming. This enables rapid pre-cooling and warming, and prevents damage to the pump 30.

[0095] (5) The pump system 101 of the fifth aspect is the pump system 101 of (4), in which the pumps 30 are provided in plurality and immersed in the cryogenic liquid L in the liquid tank 20, and the control device 80 may be capable of controlling the electric motors 37 of each of the pumps 30.

[0096] This allows the pump system 101 to quickly pre-cool and keep warm the multiple pumps 30, while preventing damage to each pump 30.

[0097] (6) A sixth aspect of the pump system 101 is the pump system 101 of (5), and includes a connecting pipe 2 that connects the plurality of pumps 30 in series in the direction of pumping the cryogenic liquid L, and the pre-stage pump 7 is provided upstream of the plurality of pumps 30 and is capable of sequentially supplying the cryogenic liquid L to the plurality of pumps 30 via the connecting pipe 2.

[0098] As a result, the pump system 101 can supply the cryogenic liquid L to the plurality of pumps 30 connected by the connecting pipes 2 while applying the electric brake 70. Therefore, according to the pump system 101 of this aspect, the pre-cooling and warming of the plurality of pumps 30 can be performed collectively.

[0099] (7) The pump system 101 of the seventh aspect is any one of the pump systems 101 of (4) to (6), and the control device 80 may be provided with a front-stage pump control unit 83 that, when an electric brake is applied by the brake control unit 82, causes the front-stage pump 7 to rotate at a lower rotation speed than when the electric brake is not applied by the brake control unit 82.

[0100] As a result, the pump system 101 can operate the pre-stage pump 7 at a lower rotation speed during pre-cooling and heat-retention operation than during normal operation, thereby making it possible to further prevent damage to the pump 30.

[0101] The pump system of the present disclosure allows for rapid pre-cooling and warming while avoiding damage to the pump.

[0102] REFERENCE SIGNS LIST 1 Pump system 2 Connecting pipe 3 Supply source 4 Pump supply pipe 4a First pump supply pipe 4b Second pump supply pipe 5 Pump discharge pipe 5a First pump discharge pipe 5b Second pump discharge pipe 6 Cooling liquid supply section 7 Pre-stage pump 8 Relief pipe 9 Check valve 10 Tank supply pipe 11 Second check valve 20 Liquid tank 21 Liquid tank body 22 Flange 30 Pump 31 Pump casing 32 Suction section 33 Discharge section 34 Rotating shaft 35 Bearing 36 Pump body 36a Impeller 37 Electric motor 37a Starter 37b Rotor 38 Discharge flow path 40 Reverse rotation prevention mechanism 41 Inner peripheral member 42 Outer peripheral member 50 Cooling pipe 51 Main cooling pipe 52 Branch cooling pipe 55 Return pipe 56 Main return pipe 57 Return branch pipe 60 Switching mechanism 61 Three-way valve 62 Discharge side control valve 63 Relief valve 64 First control valve 65 Second control valve 66 Branch control valve 67 Return control valve 68 Third control valve 70 Electric brake 71 Moving part 72 Stationary part 80 Control device 81 Pressure feed control part 82 Brake control part 83 Pre-stage pump control part 101 Pump system L Cryogenic liquid

Claims

1. A pump system comprising: a pump that can pump cryogenic liquid by rotating in the forward direction but cannot rotate in the reverse direction; a liquid tank that can store the cryogenic liquid and immerse the pump in the cryogenic liquid; and a cooling liquid supply unit that can circulate the cryogenic liquid through the pump in the direction opposite to the pumping direction.

2. The pump system according to claim 1, wherein a plurality of the pumps are provided and are immersed in the cryogenic liquid in the liquid tank, and the cooling liquid supply unit is capable of circulating the cryogenic liquid through the plurality of pumps in a direction opposite to the pumping direction.

3. A pump system as described in claim 2, further comprising a connecting pipe that connects the plurality of pumps in series in the direction of pumping of the cryogenic liquid, and the cooling liquid supply unit is capable of circulating the cryogenic liquid to the plurality of pumps via the connecting pipe in the direction opposite to the pumping direction.

4. A pump system comprising: a pump body capable of pumping cryogenic liquid when driven to rotate, and a pump having an electric motor that drives the pump body to rotate; a liquid tank capable of storing the cryogenic liquid and immersing the pump in the cryogenic liquid; a front-stage pump that is provided upstream of the pump and can sequentially supply the cryogenic liquid to the pump; and a control device that can control the electric motor of the pump, wherein the control device has a pumping control unit that controls the electric motor so that the pump pumps the cryogenic liquid, and a brake control unit that applies an electric brake to prevent the electric motor from rotating.

5. The pump system according to claim 4, wherein a plurality of the pumps are provided and are immersed in the cryogenic liquid in the liquid tank, and the control device is capable of controlling the electric motor of each of the pumps.

6. A pump system as described in claim 5, further comprising a connecting pipe that connects the plurality of pumps in series in the direction of pumping of the cryogenic liquid, and the pre-stage pump is provided upstream of the plurality of pumps and is capable of sequentially supplying the cryogenic liquid to the plurality of pumps via the connecting pipe.

7. A pump system as described in any one of claims 4 to 6, wherein the control device is provided with a front-stage pump control unit that rotates the front-stage pump at a lower rotation speed when the electric brake is applied by the brake control unit compared to when the electric brake is not applied by the brake control unit.

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