JPH09217693A - Submerged pump device for liquefied gas tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make load applied to each bearing zero at the time of restarting by connecting respective delivery pipes disposed over the upper parts of a plurality of liquid pumping pipes with a mother pipe at the upstream side of each check vale led to the mother pipe by connecting them with a communication pipe, and thereby keeping each liquid pumping pipe full of liquid even when a pump is suspended. SOLUTION: Delivery pipes 10 are connected with the upper part of each liquid pumping pipe 2. The respective delivery pipes 10 of a plurality of liquid pumping pipes 2 are connected with a mother pipe 14 by way of each check valve 11, and liquefied gas delivered out of the respective liquid pumping pipes 2, is joined together. A minimum flow pipeline 13 preventing the occurrence of pump shut-off operation, is provided for each delivery pipe 10 at the upstream side of the check valve 11 for each delivery pipe 10, and the respective delivery pipes 10 are connected with one another by a communication pipe 18. Since the blockade between each check valve and each seat surface is not complete, when a submerged pump is suspended, liquefied gas starts leaking, and its pressure is gradually lowered down. However, since liquefied gas from a separate pump in operation, is fed through the communication pipe 18, the inside of each liquid pumping pipe is kept full of liquid. By this constitution, load applied to each bearing can be made zero at the time of restating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submerged pump device for a liquefied gas tank, and more particularly, it remains in a pumping pipe of a submerged pump with a built-in tank for a liquefied gas tank that stores liquefied gas such as liquefied natural gas. It is equipped with a structure suitable for preventing backflow of liquid, keeping the inside of the pumping liquid full, and reducing the bearing load when the pump is started and stopped.
The present invention relates to a submerged pump device for a liquefied gas tank, which is suitable for reducing the weight of a closing plate at the upper part of a pump.

[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. 6 is a system diagram of a general submerged pump device for a liquefied gas tank, and FIG. 7 is a sectional view of a conventional submerged pump device for a liquefied gas tank.

In FIGS. 6 and 7, 1 is a liquefied gas tank,
2 is a pumping pipe which is suspended in the liquefied gas tank 1 and 2a
Is a head plate related to a closing plate having a pump lifting mechanism at the top of the pumping pipe 2, 3 is a suction valve provided in the lower part of the pumping pipe, 4 is a suspending wire, and 5 is inside the pumping pipe 2. It is a submersible pump that is lowered to the bottom and is installed on the seat surface 21 on the suction valve 3.

Reference numeral 10 denotes a discharge pipe provided above the pumping pipe 2,
Reference numeral 11 is a check valve provided before the plural discharge pipes 10 are connected to the mother pipe 14, 12 is a discharge hole provided in an intermediate portion of the submersible pump 5, and 13 is a minimum flow branched from the discharge pipe 10. Piping, 16 is a lift bar for lifting the pump, 17
Is a motor cable, 18 is a vibrometer cable, and 30 is a hoist for lifting.

That is, in the submersible pump device shown in FIG. 7, the submerged pump 5 has a top plate 1a in the liquefied gas tank 1.
Is suspended vertically from the head plate 2a by a suspending wire 4 in a vertical direction, for example, a length of several tens of meters, and is seated on a seat surface 21 below the pumping pipe 2. There is. The liquefied gas sucked from the suction valve 3 is pressurized by the pump portion, flows out through the discharge hole 12 provided in the middle part of the pump into the pumping pipe 2, flows upward, and is discharged from the discharge pipe 10 above the pumping pipe 2. It

FIG. 6 is a system diagram of a submerged pump device for a liquefied gas tank which has been generally used in the past. One liquefied gas tank 1 is provided with a plurality of pumping pipes 2 and each pumping liquid is pumped. The discharge pipe 10 in the upper part of the pipe 2 is configured to be integrated with the mother pipe 12 via the check valve 11.

In such a conventional device, the submersible pump 5
When the operation is stopped, the liquefied gas remaining in the pumping pipe 2 circulates in the pump through the discharge hole 12 in the center of the pump, and then flows back from the suction valve 3 to the liquefied gas tank 1,
The liquid surface of is gradually lowered and is stabilized at the same level as the liquid surface in the liquefied gas tank 1. Therefore, when the submerged pump 5 is restarted, the submerged pump 5 needs only a slight discharge pressure to push up the liquid until the discharge liquid gas fills the pumping pipe 2. It is not possible to generate a predetermined discharge pressure.

Generally, a submerged pump for a liquefied gas tank is
For example, as described in Japanese Patent Publication No. 61-5558, an axial thrust balancer is provided to make the thrust force applied to the bearing zero during pump operation. However, since this shaft thrust balancer functions when the pump generates a predetermined discharge pressure, the bearing (not shown in FIG. 7) of the submersible pump 5 uses the pumped liquefied gas to lift the pump. The pump rotor weight is applied to the bearing as a thrust load for about 3 minutes until the inside of the bearing 2 is filled.

Preventing backflow of liquefied gas in the pumping pipe 2,
As a submerged pump device for a liquefied gas tank, for example, a technique described in JP-A-1-177493 is known.
In this publication, a check valve is provided in the discharge hole of the submersible pump in order to prevent backflow of the liquefied gas in the pumping pipe when the pump is stopped. However, since this check valve cannot be completely closed, a slight backflow occurs. Further, when the liquefied gas is a gas species that is easily vaporized, it is vaporized by heat input from the surroundings. The liquid level in the pump rises gradually, leaving the pump stopped for a long time, and the liquid level in the pump eventually becomes the same as the liquid level in the liquefied gas tank. I didn't want to give enough consideration.

Further, for example, the drawings of JP-A-1-177493 and JP-A-1-301990 disclose the structure of the closing portion at the top of the pumping pipe 2. As shown in FIG. 7, the structure of the closing portion described in these publications guides the lift bar 16 for hoisting the pump on a flat disc, and also includes a guide support portion for supporting the weight of the pump, a motor cable 17, and a vibrometer cable 18. The head plate 2a having a pipe for drawing out the wiring laid inside the pumping pipe 2 is configured to close the opening at the top of the pumping pipe 2.

[0012]

In the above prior art,
When the submersible pump is started, a thrust load acts on the bearing, and the bearing life is greatly affected by the presence or absence of the bearing thrust load. The submerged pump for a liquefied gas tank has a problem that the bearing life is significantly shortened. Further, since the head plate at the top of the pumping pipe receives the discharge pressure of the pump at the flat disk portion, the plate thickness becomes thick and the weight also becomes large.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and the first object thereof is to fill the inside of the pumping pipe in the submerged pump device for a liquefied gas tank even when the pump is stopped. It is an object of the present invention to provide a submerged pump device for a liquefied gas tank, which can maintain a liquid state so that a load acting on a bearing at the time of restart can be zero and the life of the bearing can be extended.

A second object of the present invention is to provide a submerged pump device for a liquefied gas tank, which is capable of reducing the weight of the head plate, downsizing the hoist, and improving work efficiency and safety. is there.

[0015]

In order to achieve the above first object, the structure of the first invention relating to the submerged pump device for a liquefied gas tank according to the present invention comprises a plurality of lifts suspended in the liquefied gas tank. From liquid pipes, suction valves provided at the bottom of each of these pumps, and a plurality of submersion pumps installed on the seat surface above the suction valves that are lowered from the upper part of the liquefied gas tank into each of the pumps. In the middle of the submersible pump, a discharge hole for discharging the liquefied gas boosted in the pump into the pumping pipe is provided, and a check valve is provided in this discharge hole, and the liquefied gas is provided above each pumping pipe. A discharge pipe for sending liquid to the outside, a closure plate having a pump lifting mechanism at the top, and each discharge pipe of each pumping pipe is configured to be connected to a mother pipe via a check valve. In the submersible pump device, the pumps are arranged above the plurality of pumping pipes. The discharge tube is obtained by connecting the communicating pipe on the upstream side of the check valve leading to the main pipe.

More specifically, a throttle mechanism is provided in the communication pipe, or a control valve is provided in the communication pipe, and the control circuit is configured to open the control valve before operating the pump.

In order to achieve the above second object, the structure of the second invention relating to the submerged pump device for liquefied gas tank of the present invention is such that the closing plate having the pump lifting mechanism is fused with the pumping pipe. A flange, a pressure receiving plate having a curved surface portion for receiving the pressure in the pumping pipe, a guide support portion of the rieto bar penetrating and attached to the pressure receiving plate, and a support for receiving a pump load applied to the guide support portion provided inside the pressure receiving plate. It consists of a board.

[0018]

The functions of the above technical means are as follows.

According to the first aspect of the present invention, the submerged pump can generate a predetermined pump discharge pressure at the same time as the submersible pump is started by preventing the liquid level in the pumping pipe from being lowered and always maintaining a full liquid state. . Therefore, the thrust force acting on the bearing when the submersible pump is started can be made zero by the function of the shaft thrust balancer. This action has an advantage that the bearing life can be extended.

According to the second aspect of the invention, the pressure receiving portion of the head plate is formed of a plate material having a hemispherical curved surface, whereby the wall thickness of the pressure receiving portion can be greatly reduced, and the weight of the pump is added when the pump is lifted. By separately providing a support plate that supports the guide support portion, the weight of the head plate can be significantly reduced. Therefore, it is possible to reduce the size of the hoist for lifting the pump installed on the top plate of the liquefied gas tank, and to improve the efficiency and safety of the lifting work.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

First, an embodiment of the first invention will be described.

FIG. 1 is a vertical sectional view of a submersible pump device for a liquefied gas tank according to an embodiment of the present invention, FIG. 2 is a vertical sectional view of a submerged pump of the device of FIG. 1, and FIG. FIG. 3 is a system diagram of a submerged pump device for a liquefied gas tank according to an embodiment of the present invention. In the figure, the same parts as those in FIGS. 6 and 7 are the same parts, and therefore their explanations are omitted.

As shown in FIG. 1, the submersible pump 5 is installed by being seated on a seating surface 21 provided at the bottom of the pumping pipe 2 suspended in the liquefied gas tank 1.

As shown in FIG. 2, the submersible pump 5 has a structure in which a rotor body including an impeller 5E, a motor rotor 5G, and a shaft 5J, an upper bearing 5K, a middle bearing 5L, and a lower bearing that support the rotor body. 5M, stage 5F, motor stator 5
H, a fixed portion including a casing 5N, and a shaft thrust balance mechanism portion 5P. A plurality of discharge holes 12 are opened in an intermediate portion between the pump portion including the impeller 5E and the motor portion, and the check valve 22 is provided outside the discharge holes 12.
Is equipped.

A suction valve 3 is provided at the bottom of the pumping pipe 2.

The opening at the top of the pumping pipe 2 is closed by a head plate 2A composed of a pressure receiving plate and a supporting plate which will be described later as an embodiment of the second invention. A discharge pipe 10 is connected to the upper part of the pumping pipe 2.

The portion beyond the discharge pipe 10 is shown in FIG. That is, each discharge pipe 10 of the plurality of pumping pipes 2 is connected to the mother pipe 14 via the check valve 11, and joins the liquefied gas discharged from each pumping pipe 2. The check valve 11 prevents the backflow of the high-pressure discharge liquid that is discharged from each pump 2 and merges.

Further, a minimum flow pipe 13 for preventing the shutoff operation of the pump is provided in front of the check valve 11 of the discharge pipe 10 (upstream side) for each discharge pipe 10, and the minimum flow pipe 13 is It leads to the liquefied gas tank 1. Further, each discharge pipe 10 is connected by a communication pipe 18.

The operation of such a device during pump operation will be described.

The flow of liquefied gas during pump operation is
The liquefied gas in the liquefied gas tank 1 is sucked into the submersible pump 5 from the suction valve 3, is pressurized by the rotation of the impeller 5E, and is discharged to the pumping pipe 2 from a discharge hole 12 provided in the center of the pump. The check valve 22 installed in the discharge hole 12 is opened by the discharge pressure. The liquefied gas discharged from the pump passes through the pumping pipe 2 and is delivered from the discharge pipe 10 to the outside of the liquefied gas tank.

From the discharge pipe 10 through the check valve 11,
It is guided to the mother pipe 12 and sent to an evaporator (not shown) that merges with the liquefied gas discharged from another discharge pipe.

When the submersion pump 5 is stopped, the liquefied gas remaining in the pumping pipe 2 remains in the pumping pipe 2 due to the check valve 22 of the discharge hole 12 and the closing of the seat surface 21. . The liquid surface of the liquefied gas remaining in the pumping pipe 2 is gradually leaked due to the check valve 22 of the pump discharge hole 12 and the seat surface 21 not being completely blocked, and vaporization of the liquefied gas due to external heat input. However, since the liquefied gas of another operating pump is supplied from the communication pipe 18, the inside of the pumping pipe 2 is kept in a full state.

When the submersible pump 5 is restarted, the inside of the pumping pipe 2 is full as described above, and therefore the submerged pump 5 is
Can generate a predetermined discharge pressure upon activation.

That is, at the same time as the pump is started, the shaft thrust balance mechanism 5P functions to reduce the bearing thrust load to zero and extend the bearing life.

According to this embodiment, the disadvantage of the submerged pump for the liquefied gas tank, which is a drawback of the bearing load at the time of starting the pump, on the bearing life can be eliminated and the reliability can be improved.

FIG. 4 is a system diagram of a submerged pump device for a liquefied gas tank according to another embodiment of the present invention. In the figure, FIG.
The parts having the same reference numerals as those in the above are the same parts as those in the previous embodiment, and the description thereof will be omitted.

The embodiment of FIG. 4 is different from the embodiment of FIG. 3 in that the communicating pipe 18A has an orifice 19 relating to a throttle mechanism.
That is, This makes it possible to adjust the liquid supply amount to an appropriate level.

FIG. 5 is a system diagram of a submerged pump device for a liquefied gas tank according to still another embodiment of the present invention. In the figure, those having the same reference numerals as those in FIG. 3 are the same parts as those in the previous embodiment, and therefore their explanations are omitted.

The embodiment of FIG. 5 differs from the embodiment of FIG. 3 in that a valve 20 is provided in the communication pipe 18B.

When the submersible pump 5 is stopped for a long period of time, the liquefied gas is slightly supplied to the pumping pipe 2 during which the pump is stopped, but the operation efficiency is lowered, so that as shown in FIG. In addition, the valve 20 is provided in the communication pipe 18B, and the valve 20 is closed to stop the liquid supply during a period in which no operation is planned. Before the operation, the valve is opened and the liquefied gas is supplied to the pumping pipe 2 to fill the liquid. After that, an efficient method of starting the submersible pump 5 can be taken.

Next, an embodiment of the second invention will be described with reference to FIG.

The head plate 2A at the top of the pumping pipe 2 shown in FIG. 1 is formed with a flange 2e that joins the pumping pipe 2 and a hemispherical curved surface that receives the pressure in the pumping pipe 2. The plate 2d, a guide support portion of the lift bar 2b penetrating and attached to the pressure receiving plate 2d, and a support plate 2c that receives a pump load applied to the lift bar 2b provided inside the pressure receiving plate 2d.
It consists of:

Since the pressure receiving portion is constituted by the curved surface portion of the pressure receiving plate 2d and the weight of the pump at the time of lifting is supported by the support plate 2C in the pressure receiving plate 2d, the conventional disc flat plate structure is adopted. The weight can be reduced significantly compared to other head plates. Therefore, the hoist 30 for hoisting above the liquefied gas tank can be downsized, and the hoisting work can be made efficient and the safety can be improved.

The embodiment of the second invention has been described as an example in which the head plate is reduced in addition to the structure of the first invention. It can be applied to the pump without the structure of.

[0046]

As described in detail above, according to the present invention, in the submerged pump device for a liquefied gas tank, the pumping pipe is kept in a full state even when the pump is stopped, so that the bearing is restarted. It is possible to provide a submerged pump device for a liquefied gas tank that can reduce the load acting on the bearing and extend the life of the bearing.

Further, it is possible to provide a submerged pump device for a liquefied gas tank in which the weight of the head plate is reduced, the hoist is downsized, and the work efficiency and safety can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a submersible pump device for a liquefied gas tank according to an embodiment of the present invention.

2 is a vertical sectional view of a submersible pump of the apparatus of FIG.

FIG. 3 is a system diagram of a submerged pump device for a liquefied gas tank according to an embodiment of the present invention.

FIG. 4 is a system diagram of a submerged pump device for a liquefied gas tank according to another embodiment of the present invention.

FIG. 5 is a system diagram of a submerged pump device for a liquefied gas tank according to still another embodiment of the present invention.

FIG. 6 is a system diagram of a general submerged pump device for a liquefied gas tank.

FIG. 7 is a sectional view of a conventional submerged pump device for a liquefied gas tank.

[Explanation of symbols]

1 ... Liquefied gas tank, 2 ... Lifting pipe, 2A ... Head plate, 2b ... Lift bar, 2c ... Support plate, 2d ... Pressure receiving plate,
2e ... Flange, 3 ... Suction valve, 5 ... Submersible pump, 10 ...
Discharge pipe, 11 ... Check valve, 12 ... Discharge hole, 14 ... Mother pipe, 1
8, 18A, 18B ... Communication pipe, 19 ... Orifice, 20
… Valve, 21… Seat surface, 22… Check valve

Claims (5)

[Claims] 1. A plurality of pumping pipes suspended in a liquefied gas tank, suction valves provided in the lower part of each of these pumps, and a suction valve which is lowered from the upper part of the liquefied gas tank into each of the pumping pipes. It becomes a plurality of submersible pumps installed on the seating surface, the middle part of the submersible pump is provided with a discharge amount for discharging the liquefied gas pressurized in the pump into the pumping pipe, and a check valve is provided in this discharge hole. A discharge pipe for sending a liquefied gas to the outside of each of the pumping pipes, a closure plate having a pump lifting mechanism at the top, and each discharge pipe of each pumping pipe through a check valve In a submerged pump device for a liquefied gas tank configured to be connected to, each discharge pipe arranged above the plurality of pumping pipes is connected by a communication pipe upstream of a check valve leading to a mother pipe. A submerged pump device for a liquefied gas tank, which is characterized in that 2. The submerged pump device for a liquefied gas tank according to claim 1, wherein the communication pipe is provided with a throttle mechanism. 3. The submerged pump device for a liquefied gas tank according to claim 1, wherein a control valve is provided in the communication pipe, and the control circuit is configured to open the control valve before the pump is operated. 4. A closure plate having a pump lifting mechanism, a flange for joining with a pump, a pressure receiving plate having a curved surface portion for receiving pressure in the pump, and a guide support for a lift bar penetrating and attached to the pressure receiving plate. 2. The submerged pump device for a liquefied gas tank according to claim 1, wherein the submerged pump device comprises a portion and a support plate that receives a pump load applied to a guide support portion provided inside the pressure receiving plate. 5. A pumping pipe suspended in a liquefied gas tank,
It consists of a submersible pump that is lowered from the top of the liquefied gas tank into the pump and is installed on the seat surface of the bottom of the pump.
In a submerged pump device for a liquefied gas tank provided with a closing plate having a pump lifting mechanism at the top of the pumping pipe, the closing plate includes a flange that joins the pumping pipe, and a curved surface part that receives pressure in the pumping pipe. A liquefied gas tank latent-characterized storage device comprising: a pressure receiving plate, a guide support portion of a lift bar penetrating and attached to the pressure receiving plate, and a support plate for receiving a pump load applied to the guide support portion provided inside the pressure receiving plate. Submersible pump device.