JPH06185487A - Submerged pump device for liquefied gas tank - Google Patents

Abstract

PURPOSE:To reduce a bearing load when a pump is started, and improve reliability by constituting respective delivery holes of holes having a high pressure holding valve and holes in an always opening condition in a submerged pump device which is installed in a liquid pumping pipe suspended in a liquefied gas tank and has a large number of delivery holes. CONSTITUTION:A pump 5 is suspended from a head plate 2a by a wire 4 inside of a liquid pumping pipe 2 suspended from a top plate 1a inside of a liquefied gas tank 1, and is seated on a seat surface 23 of the liquid pumping pipe 2. By the way, after liquefied gas is sucked from a suction valve 3 and pressure is increased by the pump 5, it is delivered through a large number of delivery holes 5P and a delivery pipe 10. In this case, the respective delivery holes 5P are constituted of holes having a high pressure holding valve and holes in an always opening condition. The high pressure holding valve is constituted by supporting a valve body Z1 with a spring Z2 and a stay bolt Z3. Thereby, when a delivery flow rate of the pump 5 becomes excessive, the valve body Z1 is blocked up, on the one hand, when an internal and external pressure difference of the pump 5 becomes small, the valve body Z1 is opened.

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 liquefied gas, and more particularly to a submerged pump with a built-in tank for a liquefied gas tank for storing liquefied gas such as liquefied natural gas.
The present invention relates to a submerged pump device for a liquefied gas tank, which is suitable for increasing the pump discharge pressure to a rated pressure at the time of starting the pump to cause the axial thrust balance device to function, reduce the bearing load, and prolong the life of the bearing.

[0002]

2. Description of the Related Art A submerged pump device for a liquefied gas tank, as described in Japanese Patent Application Laid-Open No. 1-301990 and Japanese Patent Publication No. 61-5558, reduces thrust force applied to a ball bearing to zero during pump operation. An axial thrust balancer is provided. Therefore, during normal operation of the pump, the ball bearing has about 5
Only a 0 kg radial load is applied.

[0003]

Since the axial thrust balancer functions when the pump generates a predetermined discharge pressure, the bearing of the pump 5 waits until the discharge liquid fills the pumping pipe 2. For about 3 minutes, a total load of 1000 kg or more is applied to the ball bearing, such as the weight of the pump rotor of about 500 kg and the downward thrust of the impeller of about 500 kg. Since the life of the ball bearing is inversely proportional to the 3rd to 5th power of the load, there is a drawback that the life of the ball bearing is greatly shortened. It was difficult to expect stable operation of the pump, because the bearing was damaged by flaking after 1000 to 2000 starts.

When the submersible pump for a liquefied gas tank is started, an extremely large thrust load is applied to the ball bearings of the pump,
If the number of start-ups is large, there is a drawback that the ball bearing life becomes extremely short. In addition, in a pump using a hydrostatic bearing, the hydrostatic bearing rotates in a state where high-pressure discharge liquid is not supplied, resulting in a large shaft vibration, further shortening the life of the ball bearing. As described above, the conventional submerged pump device for a liquefied gas tank has a problem that the life of the bearing is shortened if the pump is repeatedly started.

An object of the present invention is to provide a submerged pump device for a liquefied gas tank which eliminates the adverse effect on the bearing life due to the bearing load at the time of starting the pump and improves the reliability.

[0006]

The above object is to provide a submerged pump device for a liquefied gas tank, which is installed in a pumping pipe suspended in a liquefied gas tank and has a plurality of discharge holes in a pump body. Is a closed state when the pump discharge flow rate becomes excessive, and a discharge hole with a high pressure holding valve that changes from the closed state to the open state when the pressure difference between the inside and outside of the pump body in the high pressure state becomes small, This is achieved by constructing the discharge hole in the normally open state.

Another object of the present invention is to close the plurality of discharge holes in the vicinity of these discharge holes when the pump discharge flow rate becomes excessively large, so that the pressure difference between the inside and outside of the pump body under high pressure is small. This is achieved by constructing a discharge hole having a high pressure holding valve that changes from a closed state to an open state when it becomes low, and a discharge hole that is normally open.

[0008]

[Function] A plurality of discharge holes are closed when the pump discharge flow rate becomes excessive, and when the pressure difference between the pump main body inside and outside the high pressure state becomes small, the closed state is changed to the open state. Since it is composed of a discharge hole with a valve and a discharge hole that is normally open, the pump is operated at almost the rated flow rate and rated discharge pressure even while the pumping pipe is being filled with discharge liquid. This eliminates the problem that the axial thrust balancer and static pressure bearing of the pump function normally and the thrust load applied to the ball bearing is removed, and the static pressure bearing and impeller bush rotate without contact, shortening the life of the bearing. it can.

[0009]

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

FIG. 1 is an explanatory view of a mounting state of a submerged pump device for a liquefied gas tank, FIG. 2 is a longitudinal sectional view of a submerged pump device for a liquefied gas tank, and FIGS. 3 and 4 are explanatory views of the action of a high pressure holding valve. The pump 5 is provided inside the pumping pipe 2 that is hung along the liquefied gas tank 1 from the top plate 1a along the suspension line 4 from the head plate 2a.
Seating surface 23 at the bottom of the pump 2 that is vertically suspended by several tens of meters
Is seated in. The liquefied gas sucked from the pump suction valve 3 is pressurized by the pump 5, flows through the pump 5 through the discharge hole 5P provided in the central portion of the pump, flows upward in the pumping pipe 2, and is discharged from the discharge pipe 10. Has become.

As shown in FIG. 2, the pump 5 includes a rotating body portion including an impeller 5E, a motor rotor 5G, and a shaft 5J, and bearing portions 5K, 5L, 5 for supporting the rotating body portion.
M, stage 5F, motor stator 5H, casing 5
It is composed of N and. The upper bearing 5K and the middle bearing 5L are
It is a ball bearing, and the middle bearing 5L can receive a thrust load. Further, the high pressure discharge liquid of the pump is introduced to the outer periphery of the upper bearing 5K and the middle bearing 5L to form a hydrostatic bearing. As the lower bearing 5M, a hydrostatic slide bearing is used to suppress the shaft vibration at the lower end of the shaft to a small level and prevent the impeller 5E and the stage 5F from contacting and wearing at the impeller bushing. An axial thrust balancer including a balance disc piston 5C and the like is provided in the middle of the shaft 5J to prevent the ball bearing from being subjected to thrust load.

The flow of discharge liquid during pump operation will be described. The liquid sucked into the pump 5 from the suction valve 3 is pressurized by the rotation of the impeller 5E and is discharged to the outside of the pump from the discharge hole 5P in the central portion of the pump. The discharge hole 5P is
Usually, about 10 to 30 are provided. A high pressure holding valve 30 is provided in most of the discharge hole 5P. Some of the remaining discharge holes 5P are holes that are not provided with a high pressure holding valve. The structure of the high pressure holding valve Z is, as shown in FIGS.
The valve body Z1 is pressed by the spring Z2 and the stay bolt Z3.

The operation is as follows.

When the pump 5 is started, the inside of the pumping pipe 2 is not filled with the liquid. Therefore, when the discharge liquid is about to flow 2 to 3 times as much as the normal discharge liquid, as shown in FIG. The fluid resistance against the body increases, and the valve body Z1 moves upward due to the force of the spring Z2. Then, as shown in FIG. 4, the valve body Z1 closes the discharge hole 5P. The discharge liquid of the pump is
Although it flows out from some of the discharge holes 5P without the high-pressure holding valve Z, the flow passage area becomes small, so that the pressure loss becomes large. For example, it is assumed that there are 24 discharge holes 5P in total, and 20 of them have the high pressure holding valves 30. As described above, the high pressure holding valve Z is closed, and the discharge liquid is discharged from the four discharge holes 5
It flows out from P. Therefore, the pressure of the liquid flowing out from the four discharge holes 5P is 0 to 50 m, which is only the height of the liquid surface, but the pressure in the pump 5 is such that the four discharge holes 5P function as discharge throttle orifices. , A pressure close to the rated discharge pressure of 500 m. Because of the pressure difference between the inside and outside of the pump of 450 to 500 m, the valve body Z1 is maintained in the closed state shown in FIG. At this time, since the discharge pressure is almost the rated discharge pressure, the discharge flow rate of the pump is the rated flow rate, that is, 100% flow rate. When the pump keeps sending the liquid and the discharge liquid is filled up to the discharge valve 11, the throttle of the discharge valve 11 comes to work,
The discharged liquid is squeezed in two stages by the discharge hole 5P and the discharge valve 11. When the pump is started, the discharge valve 11 has an opening that allows 30% of the rated flow rate, which is the minimum flow amount of the pump, to be opened. Therefore, when the discharge valve 11 is filled with the liquid, the pump flow rate is reduced to 30%. . Therefore, the pressure loss flowing through the discharge hole 5P sharply decreases in proportion to the square of the flow rate. Four
The throttle pressure loss of each discharge hole 5P is 500 m at 100% flow rate.
However, since the flow rate is reduced to about 50 m at a flow rate of 30%, the pressure difference between the inside and outside of the high pressure holding valve Z becomes small, and the valve body Z1 moves to the open state in FIG. After this, the discharge valve 1
1 is gradually opened, and the pump 5 is operated at the rated flow rate, but the valve body Z1 is designed to be in the closed state at twice the rated flow rate. Discharge hole 5
From P, it is discharged to the outside of the pump 5.

When the pump 5 is started, the pump 2 is pumped with the discharged liquid.
For a few minutes until the inside is filled, a slight discharge pressure for pumping up the liquid is sufficient, and the pump 5 is operated at a discharge pressure considerably lower than the rated discharge pressure. This is shown in FIG.
Explained by. The right side of FIG. 5 explains the rise of the liquid level after the pump is started, and the left side explains the change of the pump operating point with the rise of the liquid level. The liquid level at the time of normal startup of the pump 5 is set to a depth of 50 m from the discharge valve 11, the rated flow rate of the pump 5 is 100 t / h, and the rated discharge pressure is 500 m. It is known that in the pump 5 having such performance, the flow rate when the discharge pressure of the pump becomes zero is about 2 to 3 times the rated flow rate. Pump 5
Then, it is 250 t / h. When the pump 5 is started, the rotational speed of the pump 5 gradually increases and reaches the rated rotational speed of 3000 rpm in about 2 seconds. The liquid level at this time is as follows, and the pump 5 continues the large flow rate operation of about 250 t / h and raises the liquid level. After about 3 minutes, when the liquid level becomes, the discharge pressure of the pump is 50m, which is the same as the liquid level height.
However, when the discharge liquid reaches the discharge valve 11, the discharge valve 11
As a result, the flow of the discharge liquid is throttled to the rated value of 100 t / h, and the discharge pressure of the pump 5 rapidly becomes the rated value of 500 m.

FIG. 6 shows another embodiment of the high pressure holding valve.

The high-pressure holding valve Z does not use a spring and has a valve body Z1.
The valve body Z1 is opened by moving the valve body Z1 downward by utilizing its own weight, and the valve body Z1 is made of a steel ball. Z4 is a steel ball holder.

FIG. 7 shows still another embodiment of the high pressure holding valve.

The valve element Z1 has a ring shape and is a valve element common to all holes. Z5 is a ring holder.

8 to 10 show another embodiment, in which the ring-shaped valve body Z1 is provided with four holes Z1P. FIG. 9 is a plan view of the valve body Z1. When the valve is closed as shown in FIG. 10, the hole Z1P is connected to the four discharge holes 5P out of the total of 24 holes, and the liquid can be discharged to the outside of the pump 5. 8 is a sectional view taken along the line YY of FIG. 9, and FIG. 10 is a sectional view taken along the line XX of FIG.

FIG. 11 shows still another embodiment.

In the embodiment of FIGS. 3 to 10 described above, the high pressure holding valve Z is mounted on most of the discharge hole 5P of the pump 5, and when the high pressure holding valve Z is closed, a part of the discharge is not mounted. Although the liquid was sent from the hole 5P, all the discharge holes 5
A high-pressure holding valve 30 is attached to P, and liquid is fed from a small bypass hole Z1Q provided in the valve body Z1 when the valve Z is closed. The valve body Z1 having a shape similar to the valve body of the high pressure holding valve Z shown in FIGS. 3 to 11 has 24 small bypass holes Z1Q at the same positions as the 24 discharge holes 5P.
Is provided. When the valve body Z1 is closed, the discharged liquid flows through the bypass hole Z1Q.

[0023]

According to the present invention, the adverse effect of the bearing load upon starting the pump on the service life of the bearing is eliminated, and the reliability of the submerged pump device for a liquefied gas tank is improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a mounted state of an embodiment of a submerged pump device for a liquefied gas tank.

FIG. 2 is a vertical cross-sectional view of the submerged pump device for a liquefied gas tank of FIG.

FIG. 3 is a detailed view of the high pressure holding valve (open state).

FIG. 4 is a detailed view of the high pressure holding valve (closed state).

FIG. 5 is a relationship diagram of a discharge flow rate and a discharge pressure of a submerged pump device for a liquefied gas tank.

FIG. 6 is a detailed view of another embodiment of the high pressure holding valve portion.

FIG. 7 is a detailed view of still another embodiment of the high pressure holding valve portion.

8 is a sectional view taken along the line YY of FIG.

FIG. 9 is a plan view of the valve body Z1.

10 is a sectional view taken along the line XX of FIG.

FIG. 11 is a detailed view of still another embodiment of the high pressure holding valve portion.

[Explanation of symbols]

2 ... Pumping pipe, 5 ... Submersible pump, 5K ... Upper bearing, 5L ... Medium bearing, 5M ... Lower bearing, 10 ... Discharge pipe, 5C ... Balance disc piston, 11 ... Discharge valve, 30 ... High pressure holding valve, Z
1 ... Valve.

Front Page Continuation (72) Inventor Daisaku Tajima, 603 Kandamachi, Tsuchiura City, Ibaraki Prefecture Inside the Hitachi Co., Ltd. Tsuchiura Plant

Claims (4)

[Claims] 1. A submerged pump device for a liquefied gas tank, wherein the pump body is provided with a plurality of discharge holes and is installed in a pumping pipe hung in the liquefied gas tank.
When the pump discharge flow rate becomes excessive, it will be closed, and when the pressure difference between the inside and outside of the high-pressure pump body is small, it will change from the closed state to the open state. A submerged pump device for a liquefied gas tank, characterized in that it is configured with a discharge hole in a state. 2. The submerged pump device for a liquefied gas tank according to claim 1, wherein the high-pressure holding valve has a spring that moves the valve body to the inside of the pump body to open the high-pressure holding valve, and discharges the pump. A submerged pump device for a liquefied gas tank having a structure in which a spring is deformed to be in a closed state when the flow rate becomes excessive. 3. The submerged pump device for a liquefied gas tank according to claim 1, wherein the high-pressure holding valve has a valve body that is dropped due to the weight of the valve body itself to open the high-pressure holding valve, and the discharge flow rate of the pump is excessive. A submerged pump device for a liquefied gas tank, characterized in that, when the flow rate becomes low, the valve body is pushed up by the fluid resistance of the discharge flow and the flow path of the valve is closed. 4. A submerged pump device for a liquefied gas tank, which is installed in a pumping pipe hung in a liquefied gas tank and has a plurality of discharge holes in a pump body.
In the vicinity of these discharge holes, a high-pressure holding valve that closes when the pump discharge flow rate becomes excessive, and changes from the closed state to the open state when the pressure difference between the inside and outside of the pump body under high pressure becomes small. A submerged pump device for a liquefied gas tank, characterized in that it has a discharge hole that has and a discharge hole that is normally open.