Immersion motor and immersion pump

Abstract

An immersion motor (12) according to an embodiment comprises a stator (33) and a rotor (32). The stator and the rotor are each coated with a polyethylene-based heat-fusible material. An immersion pump (10) comprises the immersion motor having a motor shaft (31) to which the rotor is fixed, and the immersion pump comprises a pump shaft (21) connected to the motor shaft, and a pump body (22) formed integrally with the pump shaft. Accordingly, the immersion pump can operate with high efficiency in a state in which the stator and the rotor are directly immersed in anhydrous ammonia.

Description

Immersion motors and pumps

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to immersion motors and immersion pumps.

[0002] 2. Description of the Related Art Conventionally, a submerged pump having a canned motor is known as a submerged pump that is immersed in anhydrous ammonia (dry ammonia) stored in a low-temperature storage tank and used to pump out the anhydrous ammonia.

[0003] JP 2015-061978 A

[0004] In a canned motor, it is necessary to provide a wide gap between the stator and the rotor.

[0005] This resulted in low efficiency as a motor and low pumping capacity as a submerged pump. Furthermore, a casing was required to house the pump and motor in a sealed unit, which increased the manufacturing costs of the canned motor and, ultimately, the submerged pump.

[0006] Furthermore, assuming that a submerged pump is directly immersed in anhydrous ammonia, if an ester amide resin having an amide bond or an ester resin having an ester bond is used as the conventional coating material and impregnating resin, there is a risk that the coating material and the impregnating resin will be decomposed by the anhydrous ammonia, resulting in deterioration of the coating material and the impregnating resin.

[0007] The present invention has been made in view of the above, and has as its object to provide an immersion motor and an immersion pump that can operate with high efficiency with the stator and rotor directly immersed in anhydrous ammonia.

[0008] The immersion motor of the embodiment is an immersion motor that is driven while immersed in anhydrous ammonia, and includes a stator and a rotor, the stator and the rotor each being coated with a polyethylene-based heat-sealing material.

[0009] According to this embodiment, it is possible to provide an immersion motor, and in turn an immersion pump, that can be operated with high efficiency with the stator and rotor directly immersed in anhydrous ammonia.

[0010] Fig. 1 is an explanatory diagram of the installation state of an anhydrous ammonia submerged pump, Fig. 2 is a cross-sectional view of an embodiment of an anhydrous ammonia submerged pump, and Fig. 3 is a schematic explanatory diagram of the configuration of an anhydrous ammonia submerged-current test device.

[0011] Next, a preferred embodiment will be described in detail with reference to the drawings. Figure 1 is an explanatory diagram of the installation state of an anhydrous ammonia submerged pump. The anhydrous ammonia submerged pump 10 is installed in a PC (pre-stressed concrete) tank 2 that stores liquefied ammonia 1, and is a device that pumps the anhydrous liquefied ammonia (anhydrous ammonia) from the PC tank 2 to the outside.

[0012] The PC tank 2 includes an outer tank roof 2A, an outer tank liner 2B, a cold insulation material 2C, a cold resistance mitigation material 2D, an inner tank 2E, a PC liquid barrier 2F, and a base mat 2G. The outer tank roof 2A and the outer tank liner 2B constitute the outer tank, which, together with the inner tank 2E, forms a double-shell structure. The base mat 2G is supported by a plurality of steel pipe piles (not shown) driven into a supporting layer (not shown) underground.

[0013] Liquefied ammonia has a boiling point of −33.34° C. Liquefied ammonia can produce hydrogen by catalytic combustion, and therefore research is being conducted into its use as an alternative method for storing hydrogen. In this embodiment, as described above, anhydrous liquefied ammonia (anhydrous ammonia) is used as the liquefied ammonia.

[0014] 2 is a cross-sectional view of an anhydrous ammonia submerged pump according to an embodiment. The anhydrous ammonia submerged pump 10 includes a multi-stage centrifugal pump 11 that discharges anhydrous ammonia from the PC tank to the outside via a column, and an anhydrous ammonia submerged motor 12 that drives the multi-stage centrifugal pump 11.

[0015] The multi-stage centrifugal pump 11 includes a pump shaft 21, a centrifugal pump 22, and a pump case 23. In the above configuration, the centrifugal pump 22 includes multiple impellers integrally arranged with the pump shaft 21 and functions as a pump body. In the example of Fig. 2, the centrifugal pump 22 includes five impellers.

[0016] The pump case 23 houses the pump shaft 21 and the centrifugal pumps 22. In this case, the number of centrifugal pumps 22 can be determined appropriately based on the required performance.

[0017] The anhydrous ammonia immersion motor 12 comprises a motor shaft 31, a rotor 32 fixed to the motor shaft 31, a stator 33 arranged opposite the circumferential surface of the rotor 32, and a motor case 34 supporting the motor shaft 31, the rotor 32, and the stator 33.

[0018] The motor shaft 31 is made of, for example, stainless steel and is rotatably supported by bearings 35 provided in a motor case 34. The motor shaft 31 is coaxially connected to the pump shaft 21 of the multi-stage centrifugal pump 11 and functions as an output shaft that transmits the output of the anhydrous ammonia immersed motor 12 to the pump shaft 21.

[0019] The rotor 32 is a cylindrical magnetic body that is concentric with the motor shaft 31 and includes a rotor core 36 that is formed by laminating silicon steel plates in the axial direction, for example.

[0020] The stator 33 is disposed around the rotor 32 with a gap therebetween. The stator 33 has a stator coil 37 and a stator core 38, and when electricity is applied to the stator coil 37, a rotating magnetic field is generated in the stator 33. Then, a force is generated in the rotor 32 that is attracted by the generated rotating magnetic field, causing the rotor 32 to rotate.

[0021] As a result, motor shaft 31 to which rotor 32 is fixed rotates in a predetermined direction. At this time, pump shaft 21 is coaxially connected to motor shaft 31, so centrifugal pump 22, which includes a plurality of impellers arranged integrally with pump shaft 21, also rotates in the predetermined direction, transporting the surrounding anhydrous ammonia in the direction indicated by the arrow in Figure 2, and ultimately pumping the anhydrous ammonia in PC tank 2 to the outside.

[0022] Here, we will consider the issues that arise when manufacturing the anhydrous ammonia submerged motor 12 or the anhydrous ammonia submerged pump 10. It is known that when resin or the like is submerged in liquefied ammonia, the immersed material can undergo ammonolysis (hereinafter referred to as ammonolysis) in a similar manner to hydrolysis.

[0023] For example, methyl p-nitrobenzoate is dissolved in liquefied ammonia (NH ３ When the film is immersed in ammonia, ammonia acts on the ester bond of methyl p-nitrobenzoate, causing it to decompose into p-nitrobenzamide and methanol.

[0024] As such, ammonolysis may occur even in an environment where water is not present, and when manufacturing a liquefied ammonia immersion motor or liquefied ammonia immersion pump, an ammonia immersion test (qualitative test) must be performed.

[0025] Therefore, an anhydrous ammonia immersion test was carried out on insulating materials, conductors, insulating resins, coated conductor wires and metal materials.

[0026] (1) Insulating materials and conductors In the following, the items in parentheses are the objects to be tested for anhydrous ammonia immersion. If there are no parentheses, the material itself is the object to be tested for anhydrous ammonia immersion.

[0027] The insulating materials and conductors used were Furukawa Electric cable (cross-linked polyethylene: insulator), Furukawa Electric cable (vinyl: sheath), Furukawa Electric cable (hard aluminum wire: conductor), Junkosha cable (PTFE: insulator), Junkosha cable (tin-plated copper wire: conductor), V354 resin-impregnated mica, electrical steel sheet, DuPont (Nomex (registered trademark)), welded portion, enamelled wire, Sumitomo Seika Chemicals Co., Ltd. (Flothane (registered trademark) W380A), and Sumitomo Seika Chemicals Co., Ltd. (Flothane (registered trademark) 19132 white).

[0028] In the anhydrous ammonia immersion test, the samples were immersed in anhydrous ammonia in a 100 cc SUS container for one week. As a result of the anhydrous ammonia immersion test, no change was observed in the appearance of the immersed samples.

[0029] (2) Insulating resins: The insulating resins used were V354 resin (epoxy resin), random winding varnish (B21 varnish), enameled wire coating (polyester amide, etc.), and polyethylene powder (assuming powder coating). For the anhydrous ammonia immersion test, samples were immersed in anhydrous ammonia for one week in a 100cc SUS container.

[0030] The results of the anhydrous ammonia immersion test showed that the V354 resin (epoxy resin) liquefied, the random winding varnish (B21 varnish) decomposed slightly, the enamelled wire coating (polyester amide, etc.) decomposed, and the polyethylene powder remained unchanged.

[0031] These results indicate that there is a concern about ammonolysis of insulating resins, and that it is necessary to consider changing the material or using powder coating for protection.

[0032] (3) Coated conductor wires were tested using polyurethane resin, polyester resin, polyimide resin, PVF (Polyvinyl Fluoride) resin, or PEEK (Poly Ether Ether Ketone) resin as the coating material. The anhydrous ammonia immersion test involved immersing the wire in an anhydrous ammonia solution for one week in a 100 cc SUS container.

[0033] The results of the anhydrous ammonia immersion test showed that coatings with hydrolyzable structures such as polyurethane resin, polyester resin, and polyimide resin decomposed during anhydrous ammonia immersion. In contrast, coatings made of resins consisting of ketone or ether bonds, such as PVF resin or PEEK resin, were found to be able to withstand anhydrous ammonia immersion.

[0034] (4) Metallic materials For metallic materials, taking into consideration the case where electricity is passed through them as conductors, an anhydrous ammonia immersion-current test was conducted by passing electricity through them during the anhydrous ammonia immersion test to verify the elution and electrolysis of ions in the metal and polar components in the polymer due to the passage of electricity.

[0035] 3 is a schematic diagram illustrating the configuration of an anhydrous ammonia immersion-current test apparatus 50. The anhydrous ammonia immersion-current test apparatus 50 includes a DC power supply 51, a copper electrode 52, an electrode connector 53, test electrodes 54A and 54B, a gas inlet pipe 55, a pressure gauge 56, and a test container 57.

[0036] The DC power supply 51 applies a DC voltage between the test electrodes 54A and 54B while increasing the voltage at a predetermined rate via the pair of copper electrodes 52 and the pair of electrode connectors 53. The pair of copper electrodes 52 and the pair of electrode connectors 53 supply DC power from the DC power supply 51 to the test electrodes 54A and 54B.

[0037] The test electrodes 54A and 54B are made of the same metal material and are configured as flat plate electrodes with their opposing surfaces 54A1 and 54B1 having a substantially square shape. The gas inlet pipe 55 supplies anhydrous ammonia 60 into the test vessel 57 and transmits the pressure inside the test vessel 57 to the pressure gauge 56.

[0038] The pressure gauge 56 measures the pressure inside the test vessel 57. The voltage and current of the DC power supplied by the DC power supply 51 and the pressure measured by the pressure gauge 56 are recorded in chronological order by a logging device (not shown).

[0039] Next, the anhydrous ammonia immersion-current test will be specifically described. Iron (Fe), copper (Cu), and aluminum (Al) were used as the metal materials for forming the test electrodes 54A and 54B.

[0040] The current conditions were a maximum of 1 mA (limit), a voltage of approximately the rated voltage of the anhydrous ammonia immersion motor (up to 1 kV), and a test temperature of room temperature. The pressure inside the sealed test vessel 57 was measured in parallel using a pressure gauge 56. In this case, the test electrodes 54A and 54B were arranged in the test vessel 57 so that their opposing surfaces 54A1 and 54B1 were spaced apart by a predetermined distance.

[0041] Prior to the anhydrous ammonia immersion test, electrical conduction was confirmed. Specifically, before anhydrous ammonia was introduced into the test container 57, the DC power supply 51 started applying a voltage to the empty container, and the voltage was increased at approximately 10 V / sec until it reached 1 kV (requiring approximately 100 sec). During the voltage application period, the current was 0 mA, and the pressure inside the sealed test container 57 was constant at approximately 0.1 MPa (≒ atmospheric pressure [1 atm]).

[0042] Next, anhydrous ammonia was poured into the test container 57 until the opposing surface 54A1 of the iron test electrode 54A and the opposing surface 54B1 of the iron test electrode 54B were immersed, the container was sealed, and a voltage was applied in the same manner as when checking the electrical conductivity.

[0043] As a result, the voltage was maintained at 0 V and the current at 0 mA for approximately 2.5 seconds after the voltage was applied, and then, when the voltage reached 50 V, the current reached the limit current of 1 mA, so the current was stopped. At this time, the pressure inside the sealed test container 57 was constant at approximately 1 MPa (≒ 10 atmospheres).

[0044] These results indicate that anhydrous ammonia behaves similarly to pure water and may be conductive even when no electrolytes such as metals are eluted. The above results were obtained for the iron test electrodes 54A and 54B, but similar results were also obtained for the copper and aluminum test electrodes 54A and 54B.

[0045] (5) Conclusion Based on the experimental results of (1) to (4) above, it was found that it is best to use a polyethylene-based heat-sealing material (for powder coating) as the insulating material for an ammonia immersion motor or ammonia immersion pump, use a resin composed of ketone or ether bonds such as PVF resin or PEEK resin as the copper wire coating material, and mold the metal material with the same resin as the insulating material or conductor coating material.

[0046] For this reason, in the embodiment, the stator coil 37 is configured with a coated conductor wire (e.g., a coated copper wire). The coating of this coated conductor wire can be made of PVF (Polyvinyl Fluoride) resin, which is corrosion-resistant against anhydrous ammonia, or PEEK (Poly Ether Ether Ketone) resin. More preferably, PVF resin is used, which has a melting point of 120°C or less, which is suitable for powder coating or fluidized bed coating. In this case, the coating thickness and coating method are the same as known methods.

[0047] Furthermore, polyethylene (PE) resin, polypropylene (PP) resin, or polystyrene (PS) resin can be used as the resin having corrosion resistance against anhydrous ammonia that is impregnated to fill the gaps between the coated conductor wires of the stator coil 37. More preferably, polyethylene resin (polyethylene-based heat-sealing material) with a melting point of 120°C or less, which is suitable for powder coating or fluidized bed dipping, is used. In this case, known methods and amounts are used for the impregnation method and impregnation amount.

[0048] The stator core (stator iron core) and rotor core (rotor iron core) are also coated with polyethylene (PE) resin, polypropylene (PP) resin, or polystyrene (PS) resin. More preferably, polyethylene resin (polyethylene-based heat-sealing material) with a melting point of 120°C or less, which is suitable for flow dipping, is used.

[0049] Furthermore, the wires are fixed in the core slots by heating and melting a low-melting thermoplastic resin such as polyethylene resin, etc. In this case, the amount and method of melting are the same as known methods.

[0050] As a result, with the ammonia immersed motor or ammonia immersed pump of this embodiment, even when directly immersed in anhydrous ammonia, the insulating material or wire coating material can have a lifespan of more than one year in an environment of −33°C.

[0051] Therefore, it is possible to provide an ammonia submerged motor or an ammonia submerged pump that can be operated while being directly submerged in anhydrous ammonia.

[0052] Here, other aspects of the embodiment will be described. The immersion motor of the first aspect is an immersion motor that is driven while immersed in anhydrous ammonia, and includes a stator and a rotor, and the stator and rotor are each coated with a polyethylene-based heat-sealing material. With this configuration, even when immersed in anhydrous ammonia, the materials constituting the stator and rotor can be stably maintained, and the immersion motor can be operated with high efficiency while the stator and rotor are directly immersed in anhydrous ammonia.

[0053] The immersion motor of the second aspect includes a stator having a stator coil and a rotor, and the conductors constituting the stator coil are coated with a formal resin, a polyether ether ketone resin, or a polyethylene resin. This configuration allows the immersion motor to operate efficiently with the stator and rotor directly immersed in anhydrous ammonia, while maintaining stable coating of the conductors constituting the stator coil.

[0054] The immersion motor of the third aspect includes a stator having a stator core and a rotor, and the thermoplastic polyethylene resin is used to secure the electric wires in the slots of the stator core. With this configuration, the electric wires can be kept secured in the slots of the stator core even when the immersion motor is immersed in anhydrous ammonia, and the immersion motor can be operated stably with the stator and rotor directly immersed in anhydrous ammonia.

[0055] The submersible pump of the first aspect is a submersible pump that is used submerged in anhydrous ammonia and includes the submersible motor according to any one of the first to third aspects, wherein the submersible motor has a motor shaft to which the rotor is fixed, and the submersible pump includes a pump shaft connected to the motor shaft and a pump body integrally provided with the pump shaft. With the above configuration, it is possible to transport anhydrous ammonia with high efficiency and a high transport capacity while the pump is submerged in anhydrous ammonia.

[0056] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0057] REFERENCE SIGNS LIST 1 Liquefied ammonia 2 PC tank 10 Anhydrous ammonia immersed pump 11 Multistage centrifugal pump 12 Anhydrous ammonia immersed motor 21 Pump shaft 22 Centrifugal pump 23 Pump case 31 Motor shaft 32 Rotor 33 Stator 34 Motor case 35 Bearing 36 Rotor core 37 Stator coil 38 Stator core 50 Anhydrous ammonia immersion - current test device 51 DC power supply 52 Copper electrode 53 Electrode connector 54A Test electrode 54B Test electrode 54A1, 54B1 Opposing surface 55 Gas introduction pipe 56 Pressure gauge 57 Test vessel

Claims

1. An immersion motor that is driven while immersed in anhydrous ammonia, comprising a stator and a rotor, the stator and the rotor each being coated with a polyethylene-based heat-sealing material.

2. An immersion motor comprising a stator having a stator coil and a rotor, wherein the conductors constituting the stator coil are coated with formal resin, polyether ether ketone resin or polyethylene resin.

3. An immersion motor comprising a stator having a stator core and a rotor, wherein thermoplastic polyethylene resin is used to fix electric wires in slots of the stator core.

4. An immersion pump equipped with an immersion motor according to any one of claims 1 to 3 and used while immersed in anhydrous ammonia, wherein the immersion motor has a motor shaft to which the rotor is fixed, and the immersion pump comprises: a pump shaft connected to the motor shaft; and a pump body integrally provided on the pump shaft.

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