JPH07317695A - Submerged pump device for liquified gas tank - Google Patents

Abstract

PURPOSE:To provide a maintenance-free submerged pump device for a liquefied gas tank having bearings for reducing the thrust force applied at the time of a start. CONSTITUTION:This submerged pump device is provided with a pump main body 5 having an impeller 5C suspended in a lifting pipe 2 and boosting the liquefied gas sucked into a casing and a discharge hole 12 discharging the boosted liquefied gas, static pressure bearings 5E, 5F, 5G supporting a rotary shaft 5A, a shaft thrust balancing device having a balance disk 5J, a one-side suction type active axial magnetic bearing supporting the rotary shaft 5A, a displacement sensor 5N provided in the casing to detect the position of the rotary shaft 5A, and a controller controlling the magnetic bearing based on the output of the displacement sensor 5N.

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 to a submerged pump with a built-in tank used in a liquefied gas tank for storing a liquefied gas such as liquefied natural gas. A submerged pump for a liquefied gas tank suitable for supporting the unbalanced axial thrust in the pump that occurs during excessive discharge operation until the liquid pipe is filled with liquid, and significantly reducing the load on the bearing and extending the life of the bearing. It relates to the device.

[0002]

2. Description of the Related Art A conventional submerged pump device for a liquefied gas tank will be described with reference to FIGS. FIG. 5 is a liquefied gas tank piping system diagram including a conventional liquefied gas tank submersible pump device, and FIG. 6 is a cross-sectional view of the liquefied gas tank submerged pump device of FIG. In FIGS. 5 and 6, 1 is a liquefied gas tank, 1 a is a ceiling plate of the gas tank 1, 2 is a pump pipe suspended in the tank 1, 2 a is a pump lifting mechanism provided at the top of the pump pipe 2. A head plate 3 is provided, 3 is a suction valve attached to the lower end of the pump, 4 is a submersible pump main body 5 (described later) wire for lifting, and 5 is a submersible pump arranged in the pump. Body, 1
Reference numeral 1 is a check valve, 12 is a discharge port, 14 is a mother pipe, 17 is a power supply cable, 21 is a valve seat surface of the suction valve 3, and 30 is a hoist.

In FIG. 5, a submersible pump device comprises a pumping pipe 2 suspended in a liquefied gas tank 1, a suction valve 3 attached to the lower end of the pumping pipe 2, and an upper part of the suction valve 3. In addition, the submerged pump main body 5 is provided inside the pumping pipe 2, and is connected to the check valve 11, the mother pipe 14, and the power supply cable 17 via the discharge pipe 10.

This will be described in more detail with reference to FIG. In the submersible pump device, a pumping pipe 2 hangs down in the liquefied gas tank 1, a suction valve 3 is attached to the hanging lower end, and a submersible pump main body 5 is installed on a valve upper seat surface 21 of the suction valve 3. The submersible pump main body 5 has a wire 4 for hoisting it, a head plate 2a having a pump hoisting mechanism at the top of the pumping pipe 2, and a hoisting machine 30.

The submersible pump main body 5 is provided inside the pumping pipe 2 vertically hung from the ceiling plate 1a of the liquefied gas tank 1 by a hanging wire 4 from the head plate 2a, for example, a depth. It is suspended by 50 m, and is installed by being seated on the seat surface 21 below the pumping pipe 2.

When power is supplied to the submersible pump main body 5 by the power supply cable 17 and the operation is started, the liquefied gas is sucked from the suction valve 3 and the pressure thereof is increased, and the inside of the pumping pipe 2 is liquefied. It rises and is delivered to the discharge pipe 10. As shown in FIG. 1, a plurality of such submerged pump devices for a liquefied gas tank are usually installed in the liquefied gas tank 1.

In such a submerged pump device, when the submerged pump main body 5 stops operating, the liquefied gas remaining in the pumping pipe 2 is discharged through the discharge port 12 provided inside the pump.
Through the suction valve 3 and returned to the liquefied gas tank 1. Then, the liquid level of the liquefied gas in the pumping pipe 2 drops to the same level as the liquid level of the tank 1. Therefore, when the submersible pump body 5 is restarted, the operation is continued in a state where the discharge pressure is not secured until the pumping pipe 2 is filled with the liquefied gas. Normally, the operating time in this state is several minutes.

On the other hand, a conventional submerged pump for a liquefied gas tank is disclosed in, for example, Japanese Patent Publication No. 61-5558. The above-mentioned technology is such that a motor is housed in a casing of a vertical shaft pump, a shaft of the pump and an impeller are rotated, and a mechanical bearing carrying a shaft to which a balance cylinder for axial thrust is fixed is provided on an upper part of the impeller. A cylindrical shaft sleeve is attached to the outer peripheral surface.

A hydrostatic bearing is arranged on the outer circumference of the shaft sleeve,
At the lower end of the hydrostatic bearing, a protrusion is formed to support the shaft sleeve in the axial direction, and the protrusion and the shaft sleeve are brought into or out of contact with each other, whereby the shaft is hydrostatically pressed through the shaft sleeve. The bearing is carried. With such an axial thrust (hereinafter referred to as thrust force) balancing device, the thrust force applied to the bearing during pump operation is made zero, and a submersible pump having a long bearing life is obtained.

[0010]

In the prior art, since the axial thrust balancing device is designed so as to function with the pump generating a predetermined discharge pressure, in the case of starting the submersible pump. As described above, in the operation in which the discharge pressure is not secured, the thrust force is applied to the bearing, and the life of the bearing is significantly shortened. This thrust force is composed of the weight of the pump rotating shaft system and the fluid force acting on the impeller. When the submersible pump becomes larger, the thrust force increases more and more, and there is a problem that the bearing life tends to be shortened. The present invention has been made to solve the above problems, and its object is to reduce the thrust force acting on the bearing at the time of starting the submersible pump to reduce the latent life for the liquefied gas tank equipped with the bearing having a long life. It is to provide a submersible pump device.

A position detection sensor is provided to detect the vertical position of the pump rotation shaft. The position detection sensor is an output caused by a temperature error based on a change in the mounting position, the fluid state around the extraction cable, the temperature of the entire circumference, the temperature distribution, etc. in a transient state such as when the submersible pump is started. There is a problem that it is difficult to secure the detection accuracy due to drift. The present invention is
The present invention has been made to solve this problem, and its purpose is to minimize the temperature drift of the displacement sensor and improve its detection accuracy.

[0012]

In order to achieve the above object, the structure of the submersible pump device for a liquefied gas tank according to the present invention is configured so that it is seated on the bottom seating surface of the pumping pipe suspended in the tank, Further, a pump main body having an impeller connected to a motor through a rotary shaft to pressurize the liquefied gas sucked therein, a plurality of discharge holes for discharging the pressurized liquefied gas into a pumping pipe, and a thrust supporting the rotary shaft. In a submerged pump device for a liquefied gas tank equipped with a bearing and a radial bearing, and a shaft thrust balancer having a balance disk, a one-sided suction type active axial thrust magnetic bearing and the casing for detecting the vertical position of a rotary shaft It is characterized in that it is provided with a displacement sensor provided inside and a control unit for controlling the magnetic bearing by an output of the displacement sensor. In the submerged pump device for a liquefied gas tank according to the preceding paragraph, the in-liquid displacement sensor includes a position detection unit in the vertical direction of the rotating shaft and an electronic circuit of the detection output in a case hermetically sealed against gas and liquid. And the position detecting section is configured to detect the eddy current generated in the rotating shaft.

To explain more simply, a one-sided suction type active thrust magnetic bearing for supporting the thrust force in the axial direction generated when the submerged pump for the liquefied gas tank is started is provided, and the displacement constituting the displacement sensor of this magnetic bearing is provided. The detection coil and an electronic circuit for detecting and amplifying its output are integrated and housed in a case hermetically sealed against gas and liquid.

[0014]

The above-mentioned technical means are as follows. According to the configuration of the present invention, a one-sided suction type active axial thrust magnetic bearing that supports the thrust force generated at the time of starting the submerged pump for the liquefied gas tank is provided. When activated,
The attractive force of the magnetic bearing causes the ferromagnetic rotating body to levitate. During the operation after the start, the displacement sensor measures the gap between the detecting portion of the displacement sensor and the rotation shaft to indirectly measure the displacement of the rotation shaft in the axial direction, and the gap is constant. Therefore, the magnetic bearing is actively controlled so as to support the own weight of the rotating shaft system and the thrust force composed of the fluid force acting on the impeller.

Further, the displacement sensor is usually composed of a displacement detecting coil, a signal cable and an electronic circuit including a detection circuit and an amplification circuit. The detection accuracy of the displacement gauge is affected by the temperature drift of each element of the displacement gauge.
The temperature drift can be roughly classified into a temperature change of each element of the displacement meter and a temperature difference between the elements.

The temperature change of each of the former elements is indicated by a temperature sensor.
This can be dealt with by incorporating a circuit for performing correction by incorporating the so-called temperature compensation circuit, but the temperature difference between the latter elements cannot be removed by the method of providing the temperature compensation circuit. Therefore, the displacement detection coil, the signal cable and the electronic circuit are integrated to be housed in a closed case for gas and liquid to minimize the temperature difference between each element,
It is possible to reduce the amount of temperature drift and improve the accuracy of detecting the axial displacement of the rotary shaft.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the submerged pump device for a liquefied gas tank according to the present invention will be described with reference to FIGS. [Embodiment 1] FIG. 1 is a sectional view of a submerged pump device for a liquefied gas tank according to an embodiment of the present invention, and FIG. 2 is a sectional view of a submerged pump main body in the submerged pump device for a liquefied gas tank of FIG. 3 is an internal schematic structural diagram of a displacement sensor in the submerged pump device for liquefied gas tank of FIG.

In FIGS. 1, 2, and 3, the same reference numerals as those in FIGS. 5 and 6 denote the same parts, and thus the description thereof will be omitted.
Only new symbols will be described. 50 is a magnetic bearing control device,
5A is a pump shaft, and 5B is an inductor for improving suction performance.
5C is a plurality of impellers, 5D is a submerged motor rotor, 5E, 5F and 5G are hydrostatic bearings that are self-lubricated.
5H, 5I are auxiliary ball bearings, 5J are balance discs, 5
K is the electromagnet of the thrust magnetic bearing, 5L is the ferromagnetic material
5M is a magnetic bearing terminal block, 5N is a displacement sensor, 18
Is a magnetic bearing power supply cable and displacement sensor signal cable.
, 42 is a terminal for removing the magnetic bearing cable,
Reference numeral 101 is a displacement detection coil, and 102 is a semiconductor circuit element including a displacement signal detection circuit and a modulation circuit.

As shown in FIG. 1, the submerged pump body 5 is
It is disposed by being seated on a seat surface 21 provided at the bottom of the liquid pump 2 that hangs in the liquefied gas tank 1. On the other hand, the head cover-2a at the uppermost end of the pumping pipe 2 has a magnetic bearing power supply cable and a displacement sensor signal cable 18a.
Is provided with a terminal terminal block 42 so that these cables can be separated from the submersible pump device through the magnetic bearing terminal block 5M. And the cables 18
Is connected and wired to the magnetic bearing control device 50 installed outside the tank 1 through the terminal terminal block 42.

As shown in FIG. 2, the submersible pump body 5
In the structure of No. 5, an inducer 5B attached to the pump rotating shaft 5A for improving suction performance, a plurality of impellers 5C and a sub-merged motor rotor 5D are fixed, and these are an integrated structure, It is supposed to do. The rotary shaft 5A, the inducer 5B, the plurality of impellers 5C, and the submerged motor rotor 5D are radially supported by static pressure bearings 5E, 5F, and 5G that are self-lubricated.

On the other hand, with respect to the axial direction, the axial balance is self-balanced by the thrust balancer consisting of the balance disk 5J fixed to the rotary shaft, the pump rotor floats up in the liquid, and the axial thrust force support auxiliary. No thrust force acts on the ball bearings 5H and 5I. When the pump is stopped, the weight of the pump rotating body is supported by the auxiliary bearing 5I.

At the uppermost end of the pump rotating shaft 5A, an attraction type active axial magnetic bearing is arranged, which is composed of an electromagnet 5K of a thrust magnetic bearing portion and a ferromagnetic rotor 5L. An exciting current controlled by the magnetic bearing control device 50 flows through the power feeding cable 18 in the electromagnet 5K of the thrust magnetic bearing portion.

When the submersible pump main body 5 is started, the pumping pipe 2 is empty, so that a large discharge amount operation state occurs and the axial thrust balance mechanism does not operate. Therefore, the dead weight of the pump rotating body and the impeller 5C. And the total thrust of the fluid force acting on the balance disk 5J acts vertically downward. Therefore, the magnetic bearing electromagnet 5K is provided only on one side, and the electromagnetic force of the magnetic bearing electromagnet 5K causes the rotor 5L made of a ferromagnetic material to be pulled upward by an attractive electromagnetic force corresponding to the thrust force acting downward. Controlled.

The attracting electromagnetic force is affected by the face-to-face dimension between the magnetic bearing electromagnet 5K and the rotor 5L. Therefore, in order to indirectly detect the face-to-face dimension, the vertical position of the rotary shaft 5A is determined. Displacement sensor-5N for detecting is arranged.
The magnetic bearing control device 5 is controlled by the output of the displacement sensor-5N.
0 controls the attracting electromagnetic force of the electromagnet 5K of the magnetic bearing, and prevents the residual thrust force from being applied to the auxiliary ball bearings 5H and 5I.

Control of the attraction electromagnetic force of the electromagnet 5K of the magnetic bearing by the displacement sensor 5N and the magnetic bearing control device 50 will be described with reference to FIG. FIG. 3 shows a displacement sensor-5N.
It is a schematic structure drawing of an inside. The displacement sensor-5N is constructed by an eddy current method. As shown in FIG. 3, the displacement is a change in the inductance, and the detection coil 101 and the semiconductor circuit element 102 including a detection circuit, a modulation circuit, an amplification circuit for the displacement signal of the detection coil 101 are sealed against gas and liquid. It is stored in the existing case.

Now, when the rotary shaft 5A moves upward in the drawing and the slit δ between the coil 101 for detection and the rotary shaft 5A becomes small, the detection coil 101 causes the end face 5S of the rotary shaft 5A in the radial direction of the shaft. A large eddy current is generated, and the inductance of the detection coil 101 increases. When the inductance of the detection coil 101 increases, the magnetic bearing control device 50 decreases the exciting current of the electromagnet 5K of the magnetic bearing, the attracting electromagnetic force decreases, and the rotary shaft 5A moves downward in the drawing. When the rotary shaft 5A moves downward in the drawing and the slit δ becomes large, the inductance of the detection coil 101 becomes large, and the magnetic bearing control device 50 increases the exciting current of the electromagnet 5K of the magnetic bearing to increase the attractive electromagnetic force. It becomes large, and the rotary shaft 5A moves upward in the drawing. In this way, the slit δ is controlled to a predetermined state so that the residual thrust force is not applied to the auxiliary ball bearings 5H and 5I.

Since this displacement sensor-5N is installed inside the submersible pump main body 5 and exposed to a low temperature environment, I
Resin is used to protect C from condensation and thermal deformation of the element.
It has been killed. By using the magnetic bearing in which the displacement sensor-5N is incorporated, the control accuracy during the transition at the time of starting the pump is ensured.

[Embodiment 2] Next, another embodiment of the present invention will be described. FIG. 4 is an internal schematic structural diagram of a displacement sensor in a submerged pump device for a liquefied gas tank according to another embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 indicate the same parts, and the explanation thereof will be omitted. In this embodiment, a detection coil 101 and a semiconductor circuit element 102 including a modulation circuit and a detection circuit are housed in respective independent cases sealed for gas and liquid, and both are connected by a connector 103. . This shows the same function as the displacement sensor shown in FIG. 3 of [Example 1].

As described above, the present invention is not limited to the above-described embodiments of the present invention, and the detection coil 101 and the semiconductor circuit element 102 can be arranged in the vicinity of the pump main body 5 without any problem. Instead, variations of various embodiments are contemplated. Although the displacement sensor-5N may be larger than that of the conventional structure due to its function and configuration, a small IC can be obtained due to the progress of IC manufacturing technology, so that it can be sufficiently installed in the submersible pump device. Is obtained. Further, the drift of the output signal due to the temperature change of the signal cable 18 from the displacement sensor 5N to the magnetic bearing cable take-out terminal terminal 42 is caused by the semiconductor circuit element 1
Since it is impedance-converted at 02 and amplified to a signal level capable of long-distance transmission, it can be ignored.

[0030]

As described in detail above, according to the present invention, the temperature drift of the displacement sensor at the vertical position of the rotating shaft is provided by providing the bearing having a long life by reducing the thrust force acting on the bearing at the time of starting. Minimize and control the bearing accurately,
It is possible to provide a submerged pump device for a liquefied gas tank in which the function of the shaft thrust balancing device is improved and the bearing portion, which is the weakest part of the device, is maintenance-free.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a submersible pump main body in the submerged pump device for a liquefied gas tank of FIG.

3 is a schematic internal structural diagram of a displacement sensor in the submerged pump device for a liquefied gas tank of FIG.

FIG. 4 is a schematic internal structural diagram of a displacement sensor in a submerged pump device for a liquefied gas tank according to another embodiment of the present invention.

FIG. 5 is a liquefied gas tank piping system diagram including a conventional submerged pump device for liquefied gas tank.

6 is a sectional view of the submerged pump device for the liquefied gas tank of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tank for liquefied gas 1a ... Tank ceiling plate 2 ... Pumping pipe 2a ... Head plate 3 ... Suction valve 4 ... Suspension wire 5 ... Submersible pump main body 5A ... Pump shaft 5B ... Inducer 5C ... Impeller 5D ... Motor rotor 5E, 5F, 5G ... Static pressure bearing 5H, 5I ... Auxiliary ball bearing 5J ... Balance disk 5K ... Thrust magnetic bearing electromagnet 5L ... Ferromagnetic rotor 5M ... Magnetic bearing terminal block 5N ... Displacement sensor 5S ... End face where eddy current is generated 10 ... Discharge pipe 11 ... Check valve 12 ... Pump discharge port 14 ... Liquefied gas collecting pipe 17 ... Power supply cable 18 ... Power supply cable for magnetic bearing cable and displacement Sensor signal cable 21 ... Submersible pump seating surface 30 ... Winding machine 42 ... Magnetic bearing cable take-out terminal terminal 50 ... Magnetic bearing control device 101 ... Displacement sensor-coil 102 ... Conductive circuit elements 103 ... Connector

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Genichiro Nakamura Genrichiro Nakamura 603, Kandachi-cho, Tsuchiura-shi, Ibaraki Hitate Factory Tsuchiura Plant

Claims (2)

[Claims] 1. An impeller that is seated on the bottom seating surface of a lift pipe that hangs in a tank and that is connected to a motor by a rotary shaft to boost the pressure of the sucked liquefied gas in the casing and lifts the boosted liquefied gas. A submerged pump device for a liquefied gas tank, comprising: a pump main body having a plurality of discharge holes for discharging into a liquid pipe; a thrust bearing and a radial bearing supporting the rotating shaft; and a shaft thrust balancing device having a balance disc. , A one-sided suction type active axial thrust magnetic bearing that supports the rotating shaft, a displacement sensor provided inside the casing that detects the vertical position of the rotating shaft, and the magnetic sensor is controlled by the displacement sensor output. A submersible pump device for a liquefied gas tank, comprising: 2. The submerged pump device for a liquefied gas tank according to claim 1, wherein the displacement sensor includes a position detection unit in the vertical direction of the rotation shaft and an electronic circuit unit for the position output for gas and liquid. Stored in a sealed case,
The submerged pump device for a liquefied gas tank, wherein the position detector is configured to detect the eddy current generated in the rotating shaft.