JPH07133791A - Shaft thrust balancing device of submerged pump for liquefied gas tank - Google Patents

Abstract

PURPOSE:To prolong the life of the bearing of a submerged pump for a liquefied gas tank, prevent injury or seizure of the bearing or a sliding part between a stationary part and a rotary part, and improve shaft thrust balancing function by means of a balance disc, by making the shaft thrust applied on the bearing at starting zero. CONSTITUTION:In a shaft thrust balancing device by means of a balance disc 7 of a submerged pump for a liquefied gas tank which is installed on the seat face on a suction valve brought down in a liquid pumping pipe hung down in a liquefied gas tank, provided with a discharge port on the middle part, a discharge pipe sending liquefied gas outward on the upper part of the liquid pumping pipe, and a head plate having the suspending function for the pump on the top part, an auxiliary impeller 16 is provided in the high pressure chamber of the shaft thrust balancing device, and a release hole 22 communicated to the liquid pumping pipe 2 is provided in a shaft thrust balancing device part. Further, the auxiliary impeller itself is provided with a balance hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft thrust balancing device for a submerged pump for a liquefied gas tank.

[0002]

2. Description of the Related Art A general submerged pump device for a liquefied gas tank will be described with reference to FIGS.

FIG. 4 is a sectional view of a conventional submersible pump device for a liquefied gas tank, and FIG. 5 is a sectional view of a conventional axial thrust balancing device for a submerged pump for a liquefied gas tank.

In FIGS. 4 and 5, 1 is a liquefied gas tank, 2 is a pumping pipe suspended in the liquefied gas tank 1, and 2a.
Is a head plate of a closing plate having a pump suspending function on the top of the pump 2; 3 is a suction valve provided at the bottom of the pump 4; 4 is a suspending wire; 5 is lowered into the pump 2 It is a submersible pump installed on the seat surface 21 on the suction valve 3.

Reference numeral 10 is a discharge pipe provided on the upper part of the pumping pipe 2 and 1
1 is a discharge valve, 12 is a discharge hole provided in an intermediate portion of the submersible pump 5, 18 is a lift bar for lifting the pump, 17 is a motor cable, and 30 is a hoist for lifting.

In the submersible pump device shown in FIG. 4, the submerged pump 5 is installed in the liquefied gas tank 1 inside the pumping pipe 2 hung from the top plate 1a by means of the wire 4 for suspending from the head plate 2a. It is vertically suspended by several tens of meters and is seated on the seat surface 21 below the pumping pipe 2. The liquefied gas sucked from the suction valve 3 is boosted by the pump portion, flows out from the discharge hole 12 provided in the middle portion of the pump into the pumping pipe 2,
The liquid is discharged from the discharge pipe 10 above the pumping pipe 2.

In the sectional view of the submerged pump shaft thrust balancing device shown in FIG. 5, a balance disk 7 and a balance sheet 8 are provided on the upper part of the final stage impeller 6, and the sliding surface thereof is connected to the liquefied gas from the high pressure chamber 13. Is provided with a labyrinth to prevent it from leaking to the top.

During the pump start-up operation, the pressure of the liquefied gas reaches the maximum through the final stage impeller 6. Due to this discharge pressure, an upward force first acts on the balance disk 7. Initially, the pressure in the high pressure chamber 13 below the balance disc 7 becomes higher than that in the upper low pressure chamber 14, so that the balance disc 7 moves upward. Balance disk 7 and balance sheet 8
The pressure between the balance disk 7 and the balance sheet 8 increases as the gap of the low-pressure chamber 14 constituted by the above becomes small, so that the thrust is in equilibrium with the thrust acting downward by the impeller.

In such a conventional device, the submersible pump 5 is used.
When the operation is stopped, the liquefied gas remaining in the pumping pipe 2 flows back from the suction valve 3 to the liquefied gas tank through the discharge hole 12 in the central part of the pump, and the liquid level of the pumping pipe 2 gradually decreases and the liquefied gas tank 1 It is stable at the same level as the liquid surface of. Therefore, when the submerged pump 5 is restarted, the submerged pump 5 is a discharge liquefied gas, and a discharge pressure sufficient to push up the liquefied gas is sufficient until the inside of the pumping pipe 2 is filled and the discharge valve is reached. A predetermined discharge pressure cannot be generated.

In the conventional submerged pump for liquefied gas tank,
For example, as described in Japanese Patent Publication No. 61-5558, there is provided a shaft thrust balancing device that makes the shaft thrust applied to the bearing during pump operation zero. However, since this axial thrust balancer works when the pump is producing a certain discharge pressure,
The bearing 9 in FIG. 5 is loaded with the weight of the pump rotor and the thrust acting downward by the impeller for about 3 minutes until the pressurized liquefied gas fills the pumping pipe 2. It will be.

[0011]

SUMMARY OF THE INVENTION In the above prior art,
Axial thrust acts on the bearing when the submersible pump is started, but the bearing life is greatly affected by the presence or absence of the axial thrust at the time of startup.There was a problem that the submerged pump for a liquefied gas tank significantly shortened the bearing life. .

An object of the present invention is to provide a submerged pump device for a liquefied gas tank with an auxiliary impeller for further increasing the pressure of the high pressure chamber 13 on the high pressure chamber side of the shaft thrust balancing device when the pump is started, and the liquefied gas from the start The axial thrust balancer functions while the pump fills the pumping pipe 2 and generates a predetermined discharge pressure, so that the axial thrust acting on the bearing at the time of start-up is reduced, and wear, burnout, and damage of the bearing are prevented. An object of the present invention is to provide an axial thrust balancer for a submersible pump for a liquefied gas tank, which can extend its life.

[0013]

In order to achieve the above object, an axial thrust balancing device for a submerged pump for a liquefied gas tank according to the present invention is provided with a pump pipe hung in the liquefied gas tank and a lower part of the pump pipe. And a submersible pump that is lowered from the upper part of the liquefied gas tank into the pumping pipe and is installed on the seat surface on the suction valve.The pressure in the pump is increased in the middle of the submersible pump. Of a submerged pump for a liquefied gas tank equipped with a discharge hole for discharging the liquefied gas into the pump, and a discharge pipe for sending the liquefied gas to the outside at the upper part of the pump, and a closing plate having a pump lifting function at the top. In the axial thrust balancer, since the axial thrust balancer functions while the liquefied gas fills the pumping pipe 2 and generates a predetermined discharge pressure from the time of startup, the high pressure chamber on the high pressure chamber side of the axial thrust balancer. Increase the pressure of 13 And an auxiliary impeller for.

Further, a discharge hole is provided for discharging the liquefied gas vaporized in the axial thrust balancer into the pumping pipe.

Further, the auxiliary impeller is provided with a balance hole in order to reduce the axial thrust at the time of starting the auxiliary impeller.

[0016]

The operation of the above technical means is as follows.

According to the present invention, a higher pressure is applied to the axial thrust balancing device by the auxiliary impeller from the time when the pump is activated until the liquefied gas fills the pumping pipe 2 to generate a predetermined discharge pressure. By doing so, the axial thrust acting on the bearing when the submersible pump is started can be made zero by the axial thrust balancer functioning immediately after the startup. This action can prolong the life of the bearing.

Further, the liquefied gas vaporized in the axial thrust balancer portion does not flow into the bearing portion or the sliding portion, but is discharged to release the vaporized liquefied gas provided between the high pressure chamber 13 and the balance disk 7. Since it can be discharged from the hole into the pumping pipe, there is an advantage that it is possible to prevent burning and damage due to gas mixture in the bearing and sliding parts.

Further, since the auxiliary impeller itself also generates axial thrust at the time of starting, by providing an axial thrust balancing device for reducing this axial thrust, the effect of reducing axial thrust applied to the bearing can be increased. .

[0020]

Embodiments of the present invention will be described below with reference to FIGS. 1, 2 and 3.

(Embodiment 1) FIG. 1 is a sectional view of an axial thrust balancer for a submerged pump for a liquefied gas tank according to an embodiment of the present invention.

As shown in FIG. 1, the structure of the axial thrust balancing device of the submerged pump for a liquefied gas tank is such that a rotary body portion composed of a final stage impeller 6, an auxiliary impeller 16, a shaft 15 and a balance disc 7 A bearing (not shown in the figure) for supporting the body, a fixed part including a balance sheet 8, a casing (not shown in the figure), high-pressure chambers 13 and 13
a, the low-pressure chamber 14.

The operation at the time of starting the pump in such an apparatus will be described.

Initially, the balance disk and the entire rotating part are positioned in a lowered state by their own weight.

Immediately after the start-up, the liquefied gas is sucked from the suction valve and is pressurized by the impeller and reaches the highest pressure at the place where it exits the final stage impeller 6. Then, the liquid level rises and the inside of the pumping pipe is filled with liquid, and a predetermined discharge pressure is not generated until it reaches the discharge valve.

The auxiliary impeller 16 for further increasing the pressure in the high pressure chamber is provided in the high pressure chamber of the axial thrust balancing device immediately after the start up until the predetermined discharge pressure is generated, so that the discharge pressure is close to the predetermined discharge pressure. Since the pressure acts on the balance disc 7, an upward thrust force acts on the balance disc. At the same time, the own weight of the rotating body and the downward thrust by the impeller also act.

A labyrinth groove is formed on the sliding surface of the balance disk 7 and the balance sheet 8 to prevent the liquefied gas from leaking from the high pressure chamber to the low pressure chamber.

Further, the low-pressure chamber 14 has a structure in which the upper surface is opened, and the liquefied gas leaking from the high-pressure chamber 13a flows upward through the low-pressure chamber. Although there is a difference in pressure, the upper surface of the low-pressure chamber 14 is open, and in the high-pressure chamber 13a, the auxiliary impeller further increases the pressure, so that the upward force that pushes up the balance disc 7 largely acts. Due to this force, the rotating portion moves upward together with the balance disc 7, and when the balance disc 7 rises, the gap above the low pressure chamber 14 is closed and the liquefied gas is less likely to be discharged, so the low pressure chamber 14
The pressure rises as the balance disc 7 rises, and finally thrusts in both vertical directions are balanced so that the position of the rotating portion remains stable.

That is, the axial thrust balancing device functions at the same time as the pump is started, so that the axial thrust at the time of startup can be made zero and the bearing life can be extended.

According to this embodiment, it is possible to eliminate the disadvantage of the submerged pump for a liquefied gas tank, that is, the adverse effect on the bearing life due to the axial thrust when the pump is started.

(Embodiment 2) FIG. 2 is a sectional view of an axial thrust balancing device of a submersible pump for a liquefied gas tank according to a second embodiment of the present invention.

In the embodiment shown in FIG. 2, in addition to the embodiment shown in FIG. 1, the high-pressure chamber 13a is provided with a hole communicating with the pumping pipe.
This is the difference from the embodiment of FIG.

In this embodiment, in order to prevent liquefied gas vaporized during the process of pressurization or the like from being mixed into the bearing portion or the sliding portion between the fixed portion and the rotating portion to cause burnout or damage, the vaporized vapor is generated. The liquefied gas thus generated is discharged from the high-pressure chamber 13a into the pumping pipe through a hole leading to the pumping pipe, so that damage or burning caused by the vaporized liquefied gas mixed in the bearing part or the sliding part between the fixed part and the rotating part. No scratches will occur.

(Third Embodiment) FIG. 3 is a sectional view of an axial thrust balancer for a submerged pump for a liquefied gas tank according to a third embodiment of the present invention.

The embodiment of FIG. 3 differs from the embodiments of FIGS. 1 and 2 in that the auxiliary impeller of the high pressure chamber 13 itself is provided with a balance hole 23.

At the time of start-up, a downward thrust force is also generated by the auxiliary impeller, so that the axial thrust balancing function of the balance disk 7 is attenuated.
3 is provided, the downward thrust by the auxiliary impeller 16 is eliminated, and the axial thrust balancing function of the embodiment of FIG. 1 is improved.

[0037]

According to the present embodiment, in the shaft thrust balancer of the submerged pump for liquefied gas tank, the shaft thrust balancer functions from the start-up to make the shaft thrust acting on the bearing zero at the start-up. Thus, it is possible to supply a submerged pump for a liquefied gas tank that can extend the life of the bearing.

Further, by providing a discharge hole for discharging the vaporized liquefied gas to the pumping pipe, there is provided a submerged pump for a liquefied gas tank, which is capable of preventing damages and burns of the bearing and the sliding part between the fixed part and the rotating part. Can be supplied.

Further, a submerged pump for a liquefied gas tank can be provided which is provided with a balance hole in the auxiliary impeller itself and eliminates the downward thrust by the auxiliary impeller so as to improve the axial thrust balancing function by the balance disc. it can.

[Brief description of drawings]

FIG. 1 is a sectional view of an axial thrust balancer of a submersible pump for a liquefied gas tank according to an embodiment of the present invention.

FIG. 2 is a sectional view of an axial thrust balancing device of a submersible pump for a liquefied gas tank according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an axial thrust balancing device of a submersible pump for a liquefied gas tank according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a general submerged pump for a liquefied gas tank.

FIG. 5 is a cross-sectional view of a conventional axial thrust balancing device for a submerged pump for a liquefied gas tank.

[Explanation of symbols]

6 ... Final stage impeller, 7 ... Balance disc, 8 ... Balance sheet, 13, 13a ... High pressure chamber, 14 ... Low pressure chamber, 15
... Shaft, 16 ... Auxiliary impeller, 22 ... Emission hole.

Claims (1)

[Claims] 1. A submersible motor type submersible pump which is seated on and installed on a seating surface provided at the bottom of a lift pipe suspended in a liquefied gas tank, wherein a high pressure chamber and a low pressure chamber in the submersible pump are provided. A submerged pump for a liquefied gas tank, characterized in that an auxiliary impeller is provided on the high-pressure chamber side of a pump shaft thrust balancer constituted by a balance cylinder provided between them so as to further increase the pressure in the high-pressure chamber. Axial thrust balancer.