Submersible pump

Abstract

Provided is a submersible pump in which a liquefied gas remaining in a motor chamber can be removed.　A submersible pump 1 according to the present invention has a housing 2 that accommodates a rotary shaft 4 and an impeller 6. The housing comprises a motor chamber 21, a pump chamber 20, a recess 24 that is positioned in the motor chamber, a first flow passage 23, 52, 7 that is positioned below a motor 3 and is in communication with the motor chamber and the pump chamber, a second flow passage 25 that is positioned above the motor and is in communication with the motor chamber and an external space S on the exterior of the housing, and a third flow passage 26 that is in communication with the recess and the external space. The third flow passage is opened in a lowermost-positioned section 24a of the inner surface of the recess. The flow rate in the third flow passage is lower than the flow rate in the second flow passage. When the submersible pump is discharging a liquid to be pumped, a portion of the liquid to be pumped that has been discharged from the impeller passes through the first flow passage and is introduced into the motor chamber from the pump chamber. The liquid being pumped that has been introduced into the motor chamber passes through the motor, the second flow passage, and the third flow passage, and is led out from the motor chamber to the external space.

Description

Submerged pump

[0001] The present invention relates to a submerged pump.

[0002] Submerged pumps are used to extract liquefied gas (e.g., liquefied natural gas, etc.) from a storage tank in which the liquefied gas is stored (see, for example, Patent Document 1). The submerged pump is immersed in the liquefied gas stored in the storage tank. The submerged pump includes a pump chamber in which an impeller is accommodated and a motor chamber in which a motor is accommodated. The impeller sucks in and discharges the handling liquid from a suction port disposed at the lower end of the pump chamber. A part of the handling liquid discharged from the impeller is used for lubricating and cooling the bearing, and passes through an introduction path (e.g., a bearing, etc.) and is introduced into the motor chamber, and is also used for cooling the motor.

[0003] The submerged pump is taken out of the storage tank, for example, for maintenance. When the operation of the submerged pump stops, the inside of the submerged pump is filled with the remaining liquefied gas. When the submerged pump is pulled upward above the liquid level, the liquefied gas remaining in the pump chamber is discharged from the suction port, and the liquefied gas remaining in the motor chamber passes through the introduction path and the pump chamber and is discharged from the suction port.

[0004] Japanese Unexamined Patent Application Publication No. 2013-83172

[0005] A part of the housing partitioning the motor chamber functions as a bearing bracket that holds a bearing. The bearing bracket is formed, for example, in a cylindrical shape in order to hold the outer ring of the bearing and the holder. Further, the housing has a structure to which accessories (e.g., a vibration sensor of the bearing, etc.) can be attached in the motor chamber. Thus, irregularities are formed in the housing partitioning the motor chamber. As a result, a part of the liquefied gas remaining in the motor chamber remains in the recess formed by the irregularities. In this state, when the submerged pump is maintained, the liquefied gas and the vaporized gas leak to the outside. Most of the remaining gas has flammability and toxicity. Therefore, when the submerged pump is pulled upward above the liquid level, it is necessary to remove the liquefied gas remaining in the motor chamber (recess).

[0006] The present invention aims to provide a submerged pump capable of removing liquefied gas remaining in the motor chamber.

[0007] A submerged pump in one embodiment of the present invention is a submerged pump that is immersed in a handling fluid, and comprises a motor, a rotating shaft attached to the motor, an impeller attached to the rotating shaft, and a housing that houses the rotating shaft and the impeller, wherein the housing comprises a motor chamber housing the motor, a pump chamber located below the motor chamber and housing the impeller, a recess located in the motor chamber and concave downward, a first flow path located below the motor and communicating with the motor chamber and the pump chamber, and a motor located above the motor The submerged pump comprises a chamber and a second flow path communicating with the external space of the housing, and a third flow path communicating with the recess and the external space, wherein the third flow path opens to the lowest part of the inner surface of the recess, the flow rate of the third flow path is smaller than the flow rate of the second flow path, and when the submerged pump is discharging the handling fluid, a portion of the handling fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber to the motor chamber, and the handling fluid introduced into the motor chamber passes through the motor, the second flow path and the third flow path and is led out from the motor chamber to the external space.

[0008] The present invention provides a submerged pump capable of removing liquefied gas remaining in the motor chamber.

[0009] This is a schematic cross-sectional view showing the usage state of the submerged pump according to the present invention. This is a cross-sectional view of the submerged pump in Figure 1. This is a partially enlarged cross-sectional view of part A in Figure 2. This is a schematic diagram showing the flow of the handled liquid when the submerged pump in Figure 1 is discharging the handled liquid. This is a partially enlarged schematic cross-sectional view of the submerged pump in Figure 1 showing a portion of the flow of the handled liquid when the submerged pump in Figure 1 is discharging the handled liquid. This is a schematic diagram showing the flow of the handled liquid when the submerged pump in Figure 1 is pulled up above the liquid surface. This is a partially enlarged schematic cross-sectional view of the submerged pump in Figure 1 showing a portion of the flow of the handled liquid when the submerged pump is pulled up above the liquid surface.

[0010] Embodiments of the submerged pump according to the present invention are described below. In the following description, the drawings are referenced as appropriate. In the drawings, the same reference numerals are used for the same members and elements, and redundant descriptions are omitted. In addition, the dimensional ratios of each element may be exaggerated for the sake of explanation and are not limited to the ratios shown in the drawings.

[0011] ●Submerged Pump● ●Diagram 1 of the submerged pump configuration is a schematic cross-sectional view showing the operating state of the submerged pump according to the present invention.

[0012] The submerged pump 1 (hereinafter referred to as "the pump 1") is located inside the storage tank T in which the liquid being handled is stored, and it pumps the liquid being handled from the storage tank T to the outside. The pump 1 is immersed in the liquid being handled.

[0013] The "handled liquid" is the liquid handled (transported) by this pump 1. The handled liquid is, for example, a liquefied gas such as liquefied natural gas or liquefied ammonia.

[0014] Figure 2 is a cross-sectional view of the pump 1. In the following description, Figure 1 will be referred to together with Figure 2 as appropriate.

[0015] This pump 1 comprises a housing 2, a motor 3, a rotating shaft 4, bearings 5, an impeller 6, and a thrust balance mechanism 7.

[0016] In the following explanation, "radial direction" refers to the radial direction of the rotation axis 4. "Circumferential direction" refers to the circular direction of the rotation axis 4.

[0017] The housing 2 accommodates the motor 3, rotating shaft 4, bearing 5, impeller 6, and thrust balance mechanism 7. The shape of the housing 2 is substantially cylindrical along the vertical direction. The housing 2 includes a peripheral wall portion 2a, an upper wall portion 2b, a lower wall portion 2c, a partition wall portion 2d, a pump chamber 20, a motor chamber 21, two bearing brackets 22 and 23, a recess 24, an outlet hole 25, a drain hole 26, an orifice member 27, an inlet 28, a discharge passage 29, and an outlet (not shown; the same applies hereinafter).

[0018] In the following explanation, "upstream side" refers to the upstream side of the flow of the handling fluid inside the housing 2, and "downstream side" refers to the downstream side of the flow of the handling fluid inside the housing 2.

[0019] The peripheral wall portion 2a is a substantially cylindrical wall. The peripheral wall portion 2a separates the internal space of the housing 2 (pump room 20 and motor room 21) from the external space S of the housing 2.

[0020] "External space S" is the space outside (around) the housing 2 (the pump 1). In this embodiment, external space S is the internal space of the storage tank T. When the pump 1 is operating, at least the area around the pump 1 within external space S is filled with the liquid being handled.

[0021] The upper wall portion 2b is a wall located above the peripheral wall portion 2a. The upper wall portion 2b partitions the motor room 21 and is located above the motor 3.

[0022] The lower wall section 2c is a wall located below the partition wall section 2d. The lower wall section 2c partitions the pump room 20.

[0023] The partition wall 2d is located below the peripheral wall 2a and is positioned between the pump chamber 20 and the motor chamber 21. The partition wall 2d separates the pump chamber 20 and the motor chamber 21. The partition wall 2d is positioned below the motor 3. The partition wall 2d has an upper surface 2e and a retaining hole 2f (see Figure 3 for both; the same applies hereinafter). The retaining hole 2f is located in the center of the partition wall 2d and is a through hole that penetrates the partition wall 2d in the vertical direction. The partition wall 2d is an example of a partition wall in the present invention.

[0024] The pump chamber 20 houses the impeller 6. The pump chamber 20 is located in the lower half of the housing 2.

[0025] The motor room 21 houses the motor 3. The motor room 21 is located in the upper half of the housing 2. In other words, the motor room 21 is located above the pump room 20.

[0026] A portion of the upper wall 2b protrudes downward in a cylindrical shape, forming a bearing bracket 22. The bearing bracket 22 holds the bearing 51 (described later).

[0027] The bearing bracket 23 holds the bearing 52 (described later). The bearing bracket 23 has a two-stage cylindrical shape. The bearing bracket 23 comprises an upper part 23a and a lower part 23b (see Figure 3 for both; the same applies hereafter). The inner diameter of the upper part 23a is smaller than the inner diameter of the lower part 23b. The bearing bracket 23 is held in the partition wall portion 2d (holding hole 2f). The bearing bracket 23 is positioned below the motor 3. The upper part 23a protrudes upward from the partition wall portion 2d.

[0028] In the radial direction, a recess 24 is defined on the outer side of the bearing bracket 23 by the housing 2 (partition wall 2d, upper part 23a, and peripheral wall 2a). The shape of the recess 24 is a ring groove that is concave downwards. In a vertical view, the shape of the recess 24 is ring-shaped. That is, the recess 24 is open only upwards and has a shape that allows liquid to remain. In other words, a part of the housing 2 (near the partition wall 2d) is concave downwards, forming the recess 24. The recess 24 is located in the motor chamber 21 radially outward from the bearing bracket 23 and below the motor 3. The recess 24 has a bottom surface 24a.

[0029] The bottom surface 24a has a planar shape parallel to the horizontal direction. The bottom surface 24a is located at the lowest point of the recess 24. The bottom surface 24a is formed by the upper surface 2e of the partition wall portion 2d.

[0030] The outlet hole 25 is a through-hole that penetrates the peripheral wall portion 2a in the radial direction. The outlet hole 25 communicates with the motor chamber 21 and the external space S of the housing 2. The outlet hole 25 is located at the upper part of the peripheral wall portion 2a. In the vertical direction, the outlet hole 25 is located above the motor 3. The outlet hole 25 is an example of a second flow path in the present invention.

[0031] Figure 3 is a partially enlarged schematic cross-sectional view of section A in Figure 2. In the following description, Figures 1 and 2 will be referred to together with Figure 3 as appropriate.

[0032] The drain hole 26 is a through-hole that penetrates the partition wall 2d. The drain hole 26 opens to the upper surface 2e (bottom surface 24a of the recess 24) of the partition wall 2d and to the outer peripheral surface 2g of the partition wall 2d. That is, the drain hole 26 is located in the partition wall 2d and communicates with the recess 24 (motor room 21) and the external space S. In radial view, the shape of the drain hole 26 is approximately "L-shaped". The drain hole 26 comprises a first drain hole 26a, a second drain hole 26b, and two openings 26c and 26d. The cross-sectional area "A1" of the drain hole 26 is smaller than the cross-sectional area "A2" of the outlet hole 25. The "cross-sectional area" is the area of ​​a virtual cross-section (cross-section) perpendicular to the direction of flow of the liquid being handled inside each hole. The drain hole 26 is an example of a third flow path in the present invention.

[0033] The first drain hole 26a is the portion of the drain hole 26 that runs vertically. The second drain hole 26b is the portion of the drain hole 26 that runs radially (horizontally). The second drain hole 26b is located downstream (at the lower end) of the first drain hole 26a and is adjacent to the first drain hole 26a. The opening 26c opens into the bottom surface 24a and is located at the upstream end (upper end) of the first drain hole 26a. The opening 26d opens into the peripheral wall portion 2a and is located at the downstream end (outer radial end) of the second drain hole 26b.

[0034] The orifice member 27 restricts the flow rate of the liquid being handled through the drain hole 26. The orifice member 27 is, for example, a plug that is screwed into the drain hole 26 (first drain hole 26a). The shape of the orifice member 27 is, for example, cylindrical. The orifice member 27 has a restricting hole 27a. The orifice member 27 is detachably attached to the end of the drain hole 26 on the opening 26c side.

[0035] The aperture hole 27a is a through hole that penetrates the orifice member 27 in the vertical direction. The aperture hole 27a communicates with the recess 24 (motor chamber 21) and the portion of the drain hole 26 downstream of the aperture hole 27a. The cross-sectional area "A3" of the aperture hole 27a is smaller than the cross-sectional area "A1" of the drain hole 26. Here, the ratio of the cross-sectional area "A3" of the aperture hole 27a to the cross-sectional area "A2" of the outlet hole 25 (A3 / A2) is preferably "0.3" or less, and more preferably designed to be "0.1" or less. The aperture hole 27a is an example of a communication passage in the present invention.

[0036] In the following explanation, the drawing primarily referred to will be Figure 2. The lower part of the lower wall portion 2c is reduced in diameter, forming the suction port 28. That is, the suction port 28 is located at the lower end of the housing 2.

[0037] The discharge channel 29 is the channel through which the liquid being handled, discharged from the impeller 6, flows. The discharge channel 29 is located inside the peripheral wall 2a and the partition wall 2d.

[0038] Motor 3 is driven under predetermined operating conditions to rotate the impeller 6. Motor 3 is a known motor comprising a rotor 31 and a stator 32.

[0039] The rotating shaft 4 rotates due to the rotation of the motor 3 and transmits rotational power to the impeller 6. The rotating shaft 4 has a cylindrical shape that is aligned vertically. The rotating shaft 4 is attached to the rotor 31. The lower half 4a of the rotating shaft 4 extends downward from the motor 3 into the pump chamber 20.

[0040] The bearing 5 rotatably supports the rotating shaft 4. The bearing 5 is, for example, a rolling bearing. The bearing 5 comprises bearings 51 and 52. Bearing 51 is held in the bearing bracket 22. Bearing 52 is held in the upper part 23a of the bearing bracket 23.

[0041] The impeller 6 is attached to the lower half 4a of the rotating shaft 4 and discharges the liquid being handled, which is drawn in from below, radially outward. The impeller 6 is housed in the pump chamber 20 and is positioned above the suction port 28 in the vertical direction.

[0042] The thrust balance mechanism 7 reduces the thrust force (the force pushing the impeller 6 downward) generated by the pressure difference between the lower side and the upper side of the impeller 6. The thrust balance mechanism 7 is a known thrust balance mechanism used in known pumps. The thrust balance mechanism 7 is attached to the rotating shaft 4 and housed in the lower part 23b of the bearing bracket 23.

[0043] ● Flow of the liquid to be handled in the submerged pump Next, the flow of the liquid to be handled in this pump 1 when this pump 1 discharges the liquid to be handled (when this pump 1 is operating), and when this pump 1 is pulled upward above the liquid level, will be described below. In the following description, FIGS. 1 to 3 are referred to as appropriate.

[0044] ● Flow of the liquid to be handled when the submerged pump discharges the liquid to be handled FIG. 4 is a schematic diagram showing the flow of the liquid to be handled when this pump 1 discharges the liquid to be handled. FIG. 5 is a partially enlarged schematic cross-sectional view of this pump 1 showing a part of the flow of the liquid to be handled when this pump 1 discharges the liquid to be handled.

[0045] When this pump 1 discharges the liquid to be handled (when this pump 1 is operating), the liquid to be handled in the external space S (the internal space of the storage tank T) is sucked into this pump 1 from the suction port 28 (flow F1). The liquid to be handled sucked into the suction port 28 is sucked into the impeller 6 and discharged to the downstream side of the impeller 6 in the pump chamber 20. Most of the liquid to be handled discharged from the impeller 6 is discharged from the discharge port to the liquid delivery destination (not shown) through the discharge flow path 29 (flow F2).

[0046] A part of the liquid to be handled discharged from the impeller 6 passes through the thrust balance mechanism 7 and the bearing 52 inside the bearing bracket 23 and is introduced into the motor chamber 21 (flow F3). That is, the bearing bracket 23, the thrust balance mechanism 7, and the bearing 52 form a flow path for introducing a part of the liquid to be handled discharged from the impeller 6 from the pump chamber 20 into the motor chamber 21. The bearing bracket 23, the thrust balance mechanism 7, and the bearing 52 are an example of the first flow path in the present invention. At this time, the liquid to be handled functions as a lubricating liquid and a cooling liquid for the bearing 52.

[0047] Most of the handling liquid introduced into the pump chamber 20 passes through the motor 3 and is introduced upward of the motor 3 (flow F4). At this time, the handling liquid functions as a coolant for the motor 3. The handling liquid that has passed through the motor 3 passes through the outlet hole 25 and is discharged into the external space S (flow F5).

[0048] A part of the handling liquid introduced into the pump chamber 20 passes through the recess 24, the throttle hole 27a of the orifice member 27, and the drain hole 26 and is discharged into the external space S (flow F6).

[0049] A part of the handling liquid flowing through the discharge flow path 29 passes through the bearing 51 and is introduced into the motor chamber 21 (flow F7). At this time, the handling liquid functions as a lubricant and a coolant for the bearing 51.

[0050] Thus, the flows F1, F3, F4, and F5 form a circulating flow Fc that lubricates and cools the bearing 52 and cools the motor 3. On the other hand, the flow F6 does not contribute to the cooling of the motor 3 and is a flow that does not occur in a conventional pump (hereinafter referred to as "conventional pump") that does not have the drain hole 26. If the flow rate of the flow F6 increases and the circulating flow Fc is inhibited or greatly disturbed by the flow F6, the performance of the pump 1 will deteriorate. Therefore, the flow F6 is originally an unnecessary flow. Therefore, the flow rate of the flow F6 (in other words, the flow rate "Q1" of the handling liquid flowing through the drain hole 26 throttled by the throttle hole 27a) is designed to be sufficiently smaller than the flow rate of the circulating flow Fc (in other words, the flow rate "Q2" of the flow F5).

[0051] As mentioned above, the cross-sectional area "A3" of the throttling hole 27a is smaller than the cross-sectional area "A1" of the drain hole 26 and the cross-sectional area "A2" of the outlet hole 25. The cross-sectional area "A1" of the drain hole 26 is smaller than the cross-sectional area "A2" of the outlet hole 25. Therefore, the internal resistance of the throttling hole 27a (drain hole 26) is greater than the internal resistance of the outlet hole 25. As a result, the flow rate "Q1" of the handled fluid (flow F6) flowing through the drain hole 26, which is restricted by the throttling hole 27a, is smaller than the flow rate "Q2" of the handled fluid (flow F5) flowing through the outlet hole 25. This pump 1 limits the flow rate "Q1" by utilizing this difference in internal resistance. Specifically, the difference in internal resistance is designed so that the ratio of the flow rate "Q1" to the flow rate "Q2" (Q1 / Q2) is preferably "0.1" or less (for example, "0.01" to "0.05"). As a result, in this pump 1, the flow rate "Q1" is suppressed to an acceptable range that does not degrade the performance of this pump 1. Therefore, even if flow F6 occurs during the operation of this pump 1, the performance of this pump 1 does not degrade (even if the performance does degrade, the degradation is suppressed to an acceptable range).

[0052] ●The flow of the handled fluid when the submerged pump is lifted above the liquid surface. Figure 6 is a schematic diagram showing the flow of the handled fluid when the pump 1 is lifted above the liquid surface. Figure 7 is a partially enlarged schematic cross-sectional view of the pump 1 showing a portion of the flow of the handled fluid when the pump 1 is lifted above the liquid surface.

[0053] Pump 1 is removed from the storage tank T for maintenance, for example. At this time, the operation of pump 1 is stopped. When the operation of pump 1 is stopped, the inside of pump 1 is filled with residual handling fluid. When pump 1 is lifted above the liquid level, the handling fluid remaining in the pump chamber 20 is discharged downward (to the external space S) from the suction port 28 (flow F11). Also, the handling fluid remaining in the motor chamber 21 is discharged into the pump chamber 20 through the bearing bracket 23, bearing 52, and thrust balance mechanism 7 (flow F12), and then discharged downward (to the external space S) through the suction port 28 (flow F11) after passing through the pump chamber 20.

[0054] As mentioned above, the recess 24 is recessed downwards. Therefore, some of the handling fluid remaining in the motor chamber 21 remains in the recess 24. The handling fluid remaining in the recess 24 is discharged into the external space S through the throttling hole 27a and the drain hole 26 (flow F13). In this way, when the pump 1 is pulled up above the liquid level, the handling fluid remaining in the motor chamber 21 (recess 24) is removed. Therefore, during maintenance of the pump 1, the handling fluid and its vaporized gas do not leak to the outside of the pump 1.

[0055] Thus, the pump 1 does not have an opening / closing mechanism that closes the drain hole 26 when the pump 1 is operating and opens the drain hole 26 only when discharging the handling liquid remaining in the recess 24. In other words, in the pump 1, the drain hole 26 is always in communication with the recess 24 and the external space S. The handling liquid of the pump 1 is mostly cryogenic liquefied gas. When the pump 1 is operating, the pressure of the handling liquid introduced into the motor chamber 21 is increased by the impeller 6. Therefore, if an opening / closing mechanism for opening and closing the drain hole 26 were to be attached to the pump 1, the opening / closing mechanism would need to be liquid-tight to prevent the cryogenic and high-pressure handling liquid from leaking into the external space S, and to operate normally and reliably at cryogenic temperatures. Consequently, the manufacture of such an opening / closing mechanism is not easy, and the man-hours and processing required to attach the opening / closing mechanism to the pump 1 would be considerable, resulting in high manufacturing costs. In this pump 1, the handling fluid remaining in the recess 24 can be discharged simply by forming a through hole in the housing 2 (partition wall 2d) that communicates with the recess 24. Therefore, this pump 1 does not require any additional work or processing for the installation of an opening / closing mechanism. As a result, in this pump 1, the flow rate "Q1" of the flow F6 when the pump 1 is operating is limited, so there is no decrease in the performance of the pump 1, and the handling fluid remaining in the motor chamber 21 is easily discharged into the external space S without the need for the aforementioned opening / closing mechanism.

[0056] Furthermore, the orifice member 27 is detachable from the drain hole 26. Therefore, the internal resistance of the throttling hole 27a (drain hole 26) (flow rate "Q1" of flow F6) can be easily adjusted simply by replacing the orifice member 27 with one of a different size throttling hole 27a.

[0057] ●Summary According to the embodiment described above, the pump 1 comprises a bearing bracket 23, a recess 24, an outlet hole 25, a drain hole 26, a bearing 52, and a thrust balance mechanism 7. The recess 24 is located in the motor chamber 21. The shape of the recess 24 is a ring groove that is concave downwards. The bearing bracket 23, the bearing 52, and the thrust balance mechanism 7 are located below the motor 3 and function as a first flow path communicating between the motor chamber 21 and the pump chamber 20. The outlet hole 25 is located above the motor 3 and functions as a second flow path communicating between the motor chamber 21 and the external space S. The drain hole 26 functions as a third flow path communicating between the recess 24 and the external space S. The drain hole 26 opens into the bottom surface 24a, which is the lowest part of the inner surface of the recess 24. When the pump 1 is discharging the handling fluid (operating), a portion of the handling fluid discharged from the impeller 6 passes through the thrust balance mechanism 7 and the bearing 52 (first flow path) inside the bearing bracket 23 and is introduced into the motor chamber 21. The handling fluid introduced into the motor chamber 21 is then discharged from the motor chamber 21 to the external space S by passing through the motor 3, the outlet hole 25, and the drain hole 26. With this configuration, the drain hole 26 is always in communication with the recess 24 and the external space S. When the pump 1 is operating, at least the flow F5 in the outlet hole 25 is ensured, and the circulating flow Fc is also ensured. Furthermore, when the pump 1 is pulled up above the liquid level, any handling fluid remaining in the motor chamber 21 (recess 24) is removed. Therefore, during maintenance of the pump 1, the handling fluid and its vaporized gas do not leak to the outside of the pump 1.

[0058] Furthermore, according to the embodiment described above, the flow rate "Q1" of flow F6 is smaller than the flow rate "Q2" of flow F5. With this configuration, it is easy to secure the circulating flow Fc, and the deterioration of the performance of the pump 1 is suppressed.

[0059] Furthermore, according to the embodiment described above, the ratio of the flow rate "Q1" of flow F6 to the flow rate "Q2" of flow F5 (Q1 / Q2) is designed to be "0.1" or less. With this configuration, the flow rate "Q1" is suppressed to within an acceptable range that does not degrade the performance of the pump 1. Therefore, even if flow F6 occurs during the operation of the pump 1, the performance of the pump 1 does not degrade (even if the performance does degrade, the degradation is suppressed to an acceptable range).

[0060] Furthermore, according to the embodiment described above, the housing 2 is equipped with an orifice member 27. The orifice member 27 is detachably attached to the drain hole 26 and restricts the flow rate of the drain hole 26. With this configuration, the internal resistance of the drain hole 26 (flow rate "Q1" of flow F6) can be easily adjusted by attaching or detaching the orifice member 27.

[0061] Furthermore, according to the embodiment described above, the orifice member 27 is provided with a throttling hole 27a that communicates with the pump chamber 20 and the drain hole 26. The cross-sectional area of ​​the throttling hole 27a is smaller than the cross-sectional area of ​​the drain hole 26. With this configuration, the internal resistance of the throttling hole 27a (drain hole 26) (flow rate "Q1" of flow F6) can be easily adjusted simply by replacing the orifice member 27 with an orifice member 27 having a throttling hole 27a of a different size.

[0062] Furthermore, according to the embodiment described above, the housing 2 includes a partition wall 2d that separates the pump chamber 20 and the motor chamber 21. The recess 24 and the drain hole 26 are located in the partition wall 2d. With this configuration, the drain hole 26 can be formed simply by forming a through hole in the partition wall 2d. In other words, the formation of the drain hole 26 does not require the installation of an opening / closing mechanism or complex processing.

[0063] ●Other Embodiments In this invention, the pump 1 may be housed in a cylindrical pump column located in the internal space of the storage tank T.

[0064] Furthermore, in the present invention, the configuration of the first flow path (bearing bracket 23, bearing 52, and thrust balance mechanism 7) is not limited to this embodiment.

[0065] Furthermore, in the present invention, the number of recesses 24 is not limited to "1". In this case, the housing 2 may be provided with a drain hole 26 for each recess 24.

[0066] Furthermore, in the present invention, the position of the recess 24 is not limited to the radially outward direction of the bearing bracket 23.

[0067] Furthermore, in the present invention, the housing 2 may be provided with a flow path (outlet flow path) located inside the housing 2 instead of the outlet hole 25. In this case, the outlet flow path communicates with the motor chamber 21 and the external space S. The outlet flow path is an example of a second flow path in the present invention.

[0068] Furthermore, in the present invention, the number of outlet holes 25 is not limited to "1".

[0069] Furthermore, in the present invention, the number of drain holes 26 is not limited to "1".

[0070] Furthermore, the shape of the drain hole 26 in the radial view is not limited to an "L" shape. That is, for example, the second drain hole 26b does not have to be arranged along the radial direction. That is, for example, the second drain hole 26b may be inclined with respect to the radial direction such that the opening 26d is at the lowest end of the drain hole 26.

[0071] Furthermore, in the present invention, the aperture hole 27a is not limited to a through hole. That is, for example, the aperture hole 27a may be formed by a groove arranged on the outer circumferential surface of the orifice member 27.

[0072] Furthermore, in the present invention, if the pipe resistance of the drain hole 26 exceeds the required value, the housing 2 does not need to be provided with the orifice member 27.

[0073] Furthermore, in the present invention, the orifice member 27 may be attached to the end of the drain hole 26 on the opening 26d side.

[0074] Furthermore, in the present invention, the ratio of flow rate "Q1" to flow rate "Q2" is not limited to "0.1" or less, as long as the flow F6 does not significantly disturb the circulating flow Fc (i.e., the performance degradation of the pump 1 is kept within an acceptable range).

[0075] Furthermore, in the present invention, the number of impellers 6 is not limited to "1".

[0076] ●Embodiments of the Invention● Next, embodiments of the invention as understood from the embodiments described above will be described below, with reference to the terms and reference numerals described in each embodiment.

[0077] A first embodiment of the present invention is a submerged pump (e.g., submerged pump 1) immersed in a handling fluid, comprising: a motor (e.g., motor 3); a rotating shaft (e.g., rotating shaft 4) attached to the motor; an impeller (e.g., impeller 6) attached to the rotating shaft; and a housing (e.g., housing 2) housing the rotating shaft and the impeller, wherein the housing comprises: a motor chamber (e.g., motor chamber 21) housing the motor; a pump chamber (e.g., pump chamber 20) located below the motor chamber and housing the impeller; a recess (e.g., recess 24) located in the motor chamber and concave downwards; and a first flow path (e.g., bearing bracket 23, bearing 52) located below the motor and communicating with the motor chamber and the pump chamber. The submerged pump comprises a thrust balance mechanism 7), a second flow path (e.g., outlet hole 25) positioned above the motor and communicating with the motor chamber and the external space of the housing (e.g., external space S), and a third flow path (e.g., drain hole 26) communicating with the recess and the external space, wherein the third flow path opens to the lowest part of the inner surface of the recess (e.g., bottom surface 24a), and when the submerged pump is discharging the handling fluid, a portion of the handling fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber to the motor chamber, and the handling fluid introduced into the motor chamber passes through the motor, the second flow path, and the third flow path and is led out from the motor chamber to the external space.

[0078] A second embodiment of the present invention is a submerged pump in which, in the first embodiment, the flow rate of the third flow path (e.g., flow rate "Q1") is smaller than the flow rate of the second flow path (e.g., flow rate "Q2"). With this configuration, it is easy to ensure circulating flow and the deterioration of the pump's performance is suppressed.

[0079] A third embodiment of the present invention is a submerged pump in which, in the second embodiment, the ratio of the flow rate of the third flow path to the flow rate of the second flow path is 0.1 or less. With this configuration, the performance of the pump does not deteriorate even if flow occurs during the operation of the pump.

[0080] A fourth embodiment of the present invention is a submerged pump in which, in the second embodiment, the housing is detachably attached to the third flow path and includes an orifice member (for example, an orifice member 27) that restricts the flow rate of the third flow path. With this configuration, the resistance inside the drain hole can be easily adjusted by attaching or detaching the orifice member.

[0081] A fifth embodiment of the present invention is a submerged pump in which, in the fourth embodiment, the orifice member comprises a communication passage (e.g., a throttling hole 27a) communicating with the pump chamber and the third flow path, and the cross-sectional area of ​​the communication passage (e.g., cross-sectional area "A3") is smaller than the cross-sectional area of ​​the third flow path (e.g., cross-sectional area "A1"). With this configuration, the internal resistance of the throttling hole (drain hole) can be easily adjusted simply by replacing orifice members with throttling hole sizes.

[0082] A sixth embodiment of the present invention is a submerged pump in which, in the first embodiment, the housing includes a partition wall (for example, partition wall portion 2d) that separates the pump chamber and the motor chamber, and the recess and the third flow path are arranged in the partition wall. With this configuration, a drain hole can be formed simply by forming a through hole in the partition wall portion.

[0083] 1 Submerged pump 2 Housing 2d Partition (partition) 20 Pump chamber 21 Motor chamber 23 Bearing bracket (first flow path) 24 Recess 24a Bottom surface (part) 25 Outlet hole (second flow path) 26 Drain hole (third flow path) 27 Orifice member 27a Restriction hole (communication passage) 3 Motor 4 Rotating shaft 52 Bearing (first flow path) 6 Impeller 7 Thrust balance mechanism (first flow path) S External space

Claims

1. A submerged pump immersed in a handling fluid, comprising: a motor; a rotating shaft attached to the motor; an impeller attached to the rotating shaft; and a housing housing the rotating shaft and the impeller, wherein the housing comprises: a motor chamber housing the motor; a pump chamber located below the motor chamber and housing the impeller; a recess located in the motor chamber and facing downwards; a first flow path located below the motor and communicating with the motor chamber and the pump chamber; a second flow path located above the motor and communicating with the motor chamber and the external space of the housing; and a third flow path communicating with the recess and the external space, wherein the third flow path opens to the lowest part of the inner surface of the recess, the flow rate of the third flow path is less than the flow rate of the second flow path, and when the submerged pump is discharging the handling fluid, A submerged pump wherein a portion of the handling fluid discharged from the impeller passes through the first passage and is introduced from the pump chamber to the motor chamber, and the handling fluid introduced into the motor chamber passes through the motor, the second passage and the third passage and is led out from the motor chamber to the external space.

2. The submerged pump according to claim 1, wherein the ratio of the flow rate of the third channel to the flow rate of the second channel is 0.1 or less.

3. The submerged pump according to claim 1, wherein the housing comprises an orifice member detachably attached to the third flow path for restricting the flow rate of the third flow path.

4. The submerged pump according to claim 3, wherein the orifice member comprises a communication passage communicating with the motor chamber and the third flow path, the cross-sectional area of ​​the communication passage being smaller than the cross-sectional area of ​​the third flow path.

5. The submerged pump according to claim 1, wherein the housing comprises a partition wall separating the pump chamber and the motor chamber, and the recess and the third flow path are arranged in the partition wall.

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