Immersion motors and pumps

Abstract

The immersion motor (12) of this embodiment includes a stator (33) and a rotor (32), each coated with a polyethylene-based heat-sealing material. The immersion pump (10) is an immersion pump equipped with the immersion motor, which includes a motor shaft (31) to which the rotor is fixed, a pump shaft (21) connected to the motor shaft, and a pump body (22) integrally formed with the pump shaft. Therefore, the immersion motor can be operated with high efficiency with the stator and rotor directly immersed in anhydrous ammonia.

Description

[Technical Field]

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

[0002] BACKGROUND 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-061978 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram of the installation state of an anhydrous ammonia submerged pump. [Figure 2] FIG. 2 is a cross-sectional view of an embodiment of an anhydrous ammonia submerged pump. [Figure 3] FIG. 3 is a schematic diagram illustrating the configuration of the anhydrous ammonia immersion-current test device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, preferred embodiments will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram of the installation state of an anhydrous ammonia submerged pump. Anhydrous ammonia immersion 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) inside PC tank 2 to the outside.

[0012] Here, the PC tank 2 includes an outer tank roof 2A, an outer tank liner 2B, a cold insulation material 2C, a cold and heat 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. Because liquefied ammonia can produce hydrogen by catalytic combustion, it is also being studied as an alternative method for storing hydrogen. In this embodiment, as described above, anhydrous liquefied ammonia (anhydrous ammonia) is targeted as the liquefied ammonia.

[0014] FIG. 2 is a cross-sectional view of an embodiment of an anhydrous ammonia submerged pump. An anhydrous ammonia submerged pump 10 as an embodiment of the submerged pump includes a multistage centrifugal pump 11 that discharges anhydrous ammonia in a PC tank to the outside through a column, and an anhydrous ammonia submerged motor 12 that functions as a submerged motor to drive the multistage 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 a plurality of impellers that are integrally arranged with the pump shaft 21, and functions as a pump body. In the example of Fig. 2, five impellers are provided.

[0016] The pump case 23 also includes a pump case 23 that houses the pump shaft 21 and the centrifugal pump 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 includes a motor shaft 31, a rotor 32 fixed to the motor shaft 31, a stator 33 arranged to face 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. The motor shaft 31 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 magnetic body formed in a cylindrical shape concentric with the motor shaft 31, and includes a rotor core 36 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 of attraction to the generated rotating magnetic field is generated in the rotor 32, causing the rotor 32 to rotate.

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

[0022] Here, the problems involved in manufacturing the anhydrous ammonia submerged motor 12 or the anhydrous ammonia submerged pump 10 will be considered. It is known that when resin or the like is immersed in liquefied ammonia, the immersed material may undergo ammonolysis (hereinafter referred to as ammonolysis) as well as hydrolysis.

[0023] For example, when methyl p-nitrobenzoate is immersed in liquefied ammonia (NH3), the 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 material in parentheses is the object of the anhydrous ammonia immersion test. If there is no parenthetical notation, the material itself is the object of the anhydrous ammonia immersion test.

[0027] The insulating materials and conductors tested 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 parts, enamelled wire, Sumitomo Seika Chemicals (Flothane (registered trademark) W380A), and Sumitomo Seika Chemicals (Flothane (registered trademark) 19132 white).

[0028] In the anhydrous ammonia immersion test, the sample was immersed in anhydrous ammonia in a 100cc 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 resin The insulating resins used were V354 resin (epoxy resin), random winding varnish (B21 varnish), enamelled wire coating (polyester amide, etc.), and polyethylene powder (assuming powder coating). In the anhydrous ammonia immersion test, the sample was immersed in anhydrous ammonia in a 100cc SUS container for one week.

[0030] The results of the anhydrous ammonia immersion test showed that V354 resin (epoxy resin) liquefied. The random winding varnish [B21 varnish] decomposed slightly. The coating of the enamelled wire (polyester amide, etc.) decomposed. The polyethylene powder was 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) Insulated conductor The covered conductors were those using polyurethane resin, polyester resin, polyimide resin, PVF (Polyvinyl Fluoride) resin, or PEEK (Poly Ether Ether Ketone) resin as the covering material. In the anhydrous ammonia immersion test, the sample was immersed in anhydrous ammonia in a 100cc SUS container for one week.

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

[0034] (4) Metal materials For metal 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] FIG. 3 is a schematic diagram illustrating the configuration of the anhydrous ammonia immersion-current test device. The anhydrous ammonia immersion-current test device 50 includes a DC power supply 51 , a copper electrode 52 , an electrode connector 53 , test electrodes 54 A and 54 B, a gas introduction pipe 55 , a pressure gauge 56 , and a test container 57 .

[0036] A DC power supply 51 applies a DC voltage between test electrode 54A and test electrode 54B via a pair of copper electrodes 52 and a pair of electrode connectors 53 while increasing the voltage at a predetermined rate. A pair of copper electrodes 52 and a pair of electrode connectors 53 supply DC power from a DC power supply 51 to 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 whose opposing surfaces 54A1 and 54B1 are substantially square. 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. The metal materials used to form the test electrodes 54A and 54B were iron (Fe), copper (Cu), and aluminum (Al).

[0040] The current conditions were a maximum of 1 mA (limit), the voltage was about the rated voltage of the anhydrous ammonia immersed motor (up to 1 kV), and the test temperature was room temperature. The pressure inside the sealed test container 57 was measured in parallel with the test by a pressure gauge 56. In this case, the test electrodes 54A and 54B are arranged in a test container 57 so that their opposing surfaces 54A1 and 54B1 face each other with a predetermined distance between them.

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

[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 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 vessel 57 was constant at about 1 MPa (≈[10 atmospheres]).

[0044] These results indicate that anhydrous ammonia behaves similarly to pure water and may be conductive even when electrolytes such as metals are not 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 above experimental results (1) to (4), it was found that it is best to use a polyethylene-based heat-sealing material (for powder coating) as the insulating material used in 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 to include 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, which has a melting point of 120°C or less and is suitable for powder coating or fluidized bed dipping, is used. 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 that is corrosion-resistant to anhydrous ammonia and is used 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 of impregnation are used.

[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, suitable for fluidized bed dipping, is used.

[0049] Furthermore, to fix the electric wires in the iron core slots, a low melting point thermoplastic resin such as polyethylene resin is used and the wires are fixed by heating and melting. In this case, the melting amount and melting method 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] Other aspects of the embodiment will now 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, the stator and the rotor each being coated with a polyethylene-based heat-sealing material. According to the above configuration, the materials constituting the stator and rotor can be stably maintained even when immersed in anhydrous ammonia, and the immersion motor can be operated with high efficiency with the stator and rotor 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 formal resin, polyether ether ketone resin, or polyethylene resin. According to the above configuration, the coating of the conductors constituting the stator coil can be stably maintained even when the motor is immersed in anhydrous ammonia, and the immersion motor can be operated with high efficiency with the stator and rotor directly immersed in anhydrous ammonia.

[0054] The immersion motor of the third aspect includes a stator having a stator core, and a rotor, and uses thermoplastic polyethylene resin to fix electric wires in slots of the stator core. According to the above configuration, even when immersed in anhydrous ammonia, the wires in the slots of the stator core can be kept fixed, 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 an submersible pump that includes the submersible motor according to any one of the first to third aspects and is used while submerged in anhydrous ammonia, 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 that is integral with the pump shaft. According to the above-described configuration, it is possible to transport anhydrous ammonia with high efficiency and a large transport capacity while the container is immersed in the 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. [Explanation of symbols]

[0057] 1. Liquefied ammonia 2 pcs tank 10 Anhydrous ammonia immersion 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 bearings 36 rotor core 37 Stator coil 38 stator core 50 Anhydrous ammonia immersion-current test equipment 51 DC power supply 52 copper electrode 53 Electrode Connector 54A Test Electrode 54B Test Electrode 54A1, 54B1 opposing surfaces 55 Gas introduction pipe 56 Pressure gauge 57 Test vessel

Claims

1. An immersion motor that is driven by being immersed in anhydrous ammonia, It has a stator and a rotor. The stator and rotor are each coated with a polyethylene-based heat-sealing material. Submersible motor.

2. The stator has a stator coil, For the insulation of the conductors constituting the stator coil, formal resin, polyetheretherketone resin, or polyethylene resin is used. The immersion motor according to claim 1.

3. The stator has a stator core, Thermoplastic polyethylene resin was used to fix the wires in the slots of the stator core. The immersion motor according to claim 1.

4. An immersion pump comprising an immersion motor according to any one of claims 1 to 3, which is used by immersing in anhydrous ammonia, The immersion motor has a motor shaft to which the rotor is fixed, The aforementioned immersion pump is The pump shaft connected to the motor shaft, The pump body is integrally mounted on the pump shaft, A submersible pump equipped with a submersible pump.

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