JP4300088B2 - Submerged pump - Google Patents

Description

  The present invention relates to a submerged pump in which a pump and a motor for driving the pump are integrally formed and immersed in a stored handling fluid to be used for pumping the handling fluid.

  Submerged pumps are used to pump low-temperature fluids such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG). In the submerged pump, a pump such as a centrifugal pump and a motor that drives the pump are integrally formed, and the submerged pump is used by being immersed in a fluid that handles the whole. For this reason, it is configured such that the handling fluid also enters the periphery of the motor stator and the rotor and the motor and pump shaft bearings, and cooling, lubrication, and the like are performed with this handling fluid.

  In particular, lubrication may be performed by sending a handling fluid discharged by a pump to a bearing near the upper end of the shaft (see, for example, paragraph 0006 of Patent Document 1 below).

CD-ROM of Japanese Patent Application No. 5-26949 (Japanese Utility Model Application No. 6-80896)

  In the submerged pump, if a component that is easily vaporized is contained in the handled fluid, there is a problem in that it may vaporize in the vicinity of the bearing, resulting in poor lubrication of the bearing.

  The present invention provides a submerged pump that is advantageous in preventing poor lubrication of a bearing portion.

Submerged pump of the present invention, the handling fluid pump unit is discharged, and through the bearing supporting the motor shaft near its upper end, has an introduction path for guiding in the housing to pay motor, the introduction path A throttle structure is provided on the downstream side of the bearing.

  By providing a throttle structure on the downstream side of the bearing, the pressure around the bearing is increased and vaporization of the handling fluid around the bearing is prevented.

  Further, the inlet of the annular flow path for returning the handled fluid in the housing for housing the motor to the pump unit is arranged at a position higher than the bearing near the upper end of the motor shaft.

  As a result, even if gas remains in the housing, it is discharged from the housing before reaching the periphery of the bearing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a submerged pump according to the present embodiment. The submerged pump 10 has a structure in which a pump unit 12 including a pump for increasing the pressure of a handled fluid and a motor unit 14 for driving the pump are accommodated in a pot 16. The opening at the top of the pot 16 is covered by a head plate 18. The handling fluid enters the pot 16 from the intake pipe 20, while the gas is discharged from the degassing pipe for extracting the gas in the pot 16, thereby filling the pot 16 with the handling fluid. Even when the submerged pump 10 is actually installed, the submerged pump 10 is arranged so that the vertical direction thereof coincides with the vertical direction of FIG. It arrange | positions so that the motor part 14 may become down.

  The pump unit 12 includes a multistage centrifugal pump in which a plurality of centrifugal pumps 26 are disposed on a common pump shaft 24. A suction pipe 28 is attached below the multistage centrifugal pump, that is, in the suction portion of the first stage centrifugal pump 26, and an inducer 30 attached to the pump shaft 24 and driven is disposed in the suction pipe 28. Has been.

  The motor unit 14 above the pump unit 12 includes a motor 32 that drives a multistage centrifugal pump, and a housing cylinder 34 that is disposed so as to surround the motor 32. The motor 32 includes a motor shaft 36 common to the pump shaft 24, a rotor 38 fixed to the motor shaft 36, and a stator 40 fixed to the housing cylinder 34. An attachment plate 42 is coupled to the lower end of the housing cylinder 34, and the pump unit 12 is attached to the attachment plate 42 and integrated with the motor unit 14. On the other hand, a discharge manifold 44 is coupled to the upper end of the housing cylinder 34, and the housing cylinder 34, the mounting plate 42 and the discharge manifold 44 constitute a housing for housing the motor 32.

  The mounting plate 42 holds a lower bearing 46 that is a rolling bearing that supports the motor shaft 36 in a rotatable manner. Further, the mounting plate 42 is also provided with a lower seal 48 that suppresses the flow of pressurized handling fluid to the motor unit 14 of the pump unit 12. The lower seal 48 has a slight gap with the pump shaft 24, and the handling fluid flows to a housing chamber 49, which is a space in the housing of the pump unit 12, though slightly, from this gap. This handling fluid passes through the lower bearing 46 and at this time lubricates the bearing. The discharge manifold 44 holds an upper bearing 50 that rotatably supports the vicinity of the upper end of the motor shaft 36. Further, the discharge manifold 50 is provided with a discharge port 54 connected to a discharge hole 52 provided in the head plate 18. The handling fluid sent out from the multistage centrifugal pump is sent to the discharge port 54 by the discharge flow path 56 arranged around the stator 40 of the motor unit 14 and the like, and is further sent out to the outside.

  Further, the discharge manifold 44 is provided with an introduction path 58 for introducing the handling fluid from the discharge port 54 to the housing chamber 49. An upper bearing 50 is disposed in the introduction path 58, and an upper seal 60 is further disposed downstream thereof. The configuration related to these introduction paths 58 will be described in detail later. An inlet 62 a of the annular flow path 62 for returning the handling fluid in the housing chamber 49 to the pump unit 12 is provided at a position higher than the upper bearing 50 in the housing chamber 49, preferably at the top. The annular flow path 62 collects the gas accumulated in the housing chamber 49 and sends it to the pump unit 12 together with the handling fluid.

FIG. 2 is a diagram showing details of the configuration related to the introduction path 58. The introduction path 58 first guides the handling fluid from the discharge port 54 to the upper bearing 50. The upper bearing 50 is a rolling bearing, preferably a ball bearing. The handling fluid passes through the gaps between the inner race, the outer race, and the rolling elements of the upper bearing 50 and further flows downward. The handling fluid that passes through the upper bearing 50 functions as a lubricant for the upper bearing. The handling fluid that has passed through the upper bearing 50 reaches the upper seal 60. The upper seal 60 forms a slight gap 64 between the outer periphery of the motor shaft 36 and a structure in which the flow path of the introduction path 58 is narrowed to increase the flow path resistance. This diaphragm structure, causing a pressure difference before and after the gap 64, around the upper bearing 50, is maintained at a pressure close to the elevated pressure by multistage centrifugal pump, whereas in the housing chamber 49, relatively low pressures It has become. Further, the flow rate passing through the introduction path 58 is suppressed by the throttle structure, thereby suppressing the decrease in the discharge amount of the submerged pump 10, that is, the decrease in the flow rate of the handling fluid to be pumped.

  By maintaining the pressure in the vicinity of the upper bearing 50 high, vaporization in the bearing portion is prevented even when a component that is easily vaporized is contained in the handled fluid, so that poor lubrication of the bearing does not occur. Therefore, the dimensions, for example, the gap and the length, of the throttle structure are the dimensions necessary to maintain the pressure that can suppress the vaporization of the handling liquid at the bearing portion. Further, the shape of the flow path at the narrowed portion may be bent in a crank shape in addition to a linear shape, and further, a labyrinth structure in which narrow portions and wide portions are alternately arranged can be adopted.

  Further, since the gas generated in the housing chamber 49 is returned to the annular flow path 62 at a position higher than the upper bearing 50, the liquid level is lowered due to the retention of the gas in the housing chamber 49 and reaches the vicinity of the upper bearing 50. The resulting poor lubrication is prevented.

  The submerged pump 10 of this embodiment is suitable as a pump that handles LNG containing carbon monoxide, for example. When LNG contains carbon monoxide, the boiling point of carbon monoxide is lower than that of other components of LNG or LNG not containing carbon monoxide, and gas (carbon monoxide) is generated at a lower temperature. As in the present embodiment, in the introduction path 58, by providing a throttle structure downstream from the upper bearing 50, gas is prevented from being generated near the upper bearing 50, resulting in poor lubrication.

  In the present embodiment, an example of a three-stage centrifugal pump is shown, but the number of stages can be appropriately selected according to design requirements. Further, as the upper and lower bearings, rolling bearings other than ball bearings can be adopted depending on design requirements.

It is a figure which shows schematic structure of the submerged pump 10 of this embodiment. 2 is a view showing a detailed structure near the upper end of a motor shaft of a submerged pump 10. FIG.

Explanation of symbols

  10 submerged pump, 12 pump section, 14 motor section, 16 pot, 24 pump shaft, 26 centrifugal pump, 32 motor, 34 housing cylinder, 36 motor shaft, 44 discharge manifold, 49 housing chamber, 50 upper bearing, 52 discharge hole , 54 Discharge port, 56 Discharge channel, 58 Inlet channel, 60 Upper seal, 62 Ring channel.

Claims (2)

A submerged pump having a pump that discharges a handling fluid containing a component that easily vaporizes and a motor that is above the pump and drives the pump;
The motor is housed in a housing, the shaft of the motor is supported by a bearing near its upper end,
Furthermore, an introduction path for guiding the handling fluid discharged by the pump from the vicinity of the upper end of the shaft into the housing through the bearing,
A throttle structure that is provided on the bearing downstream side of the introduction path and increases the flow resistance of the introduction path;
Having a submerged pump. 2. The submerged pump according to claim 1, further comprising an annular flow path for returning a handling fluid in the housing to the pump, wherein an inlet on the housing side of the annular flow path is disposed at a position higher than the bearing. Submerged pump.

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