JPH0211890A - Reverse preventing device for internal pump - Google Patents

Abstract

PURPOSE:To surely prevent a pump shaft from reversely rotating by providing a flow path of motor cooling water so as to prevent dust from jamming in a jam block rotating part in a reversing side. CONSTITUTION:An internal pump forms its reverse preventing device 23a, mounting a rotating side cylinder 19a to a disk-shaped thrust disk 15 fixed to a pump shaft 2. The rotary side cylinder 19a comprises an inner cylinder 27 and an outer cylinder 28, having an inside diameter larger than the outside diameter of this inner cylinder 27, being fixed, and a flow path 29 of motor cooling water is formed between the inner cylinder 27 and the outer cylinder 28. Two or more through holes 30 are provided in the inner cylinder 27. Jam blocks 24, which freely rotate with a rotary shaft 25 serving as the center, are pressed to a stationary side cylinder 22 by a rotary spring 26 mounted to the periphery of the rotary shaft 25 when the pump is in stopping.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides an internal pump that prevents reverse rotation when a vertical shaft internal pump that is directly incorporated into a nuclear reactor pressure vessel is stopped. Related to pump anti-reverse device.

(Prior Art) Generally, a plurality of internal pumps (recirculation pumps) are directly incorporated into a nuclear reactor pressure vessel.

FIG. 8 shows an example of a conventional internal pump, in which an impeller 3 is attached to the upper end of a pump shaft 2 that passes through a pressure vessel 1, and a diffuser 4 for rectification provided on the outside of the impeller 3 is a stretch tube. 5 and is pulled downward and fixed to the pressure vessel 1.

A motor section 8 consisting of a rotor 6 and a stator 7 is connected below the pump shaft 2, and motor cooling system pipes 10 and 11 are provided at the upper and lower ends of a vertically long casing 9, respectively, to cool the motor section 8. It is open, and a heat exchanger (not shown) is connected in the middle.

There is no sealing mechanism between the stretch tube 5 and the pump shafts 1 to 2, and the internal pressures of the pressure vessel 1 and the motor section 8 are almost equal, but heat transfer from the pressure vessel 1 side to the motor section and fine dust may occur. In order to prevent the inflow, a purge water system piping 12 is installed in the middle of the pipe to supply cold water.

A coupling stud 13 is attached to the lower end of the pump shaft 2.
The upper end of the coupling stud 13 is fixed, and a disk-shaped thrust disk 15 is connected to the lower end of the coupling stud 13 via a nut 14.
is fixed.

The thrust disk 15 is provided with a plurality of through holes 16 in the radial direction, and upper and lower thrust bearings 17 and lower thrust bearings are provided at the top and bottom of the thrust disk 15 to stabilize the vertical movement of the pump shaft 2 when the pump rotates. Bearing 1
8 is provided.

Roughly below the thrust disk 15, there is provided a reverse rotation preventer 23 consisting of a rotating cylinder '19 and a cylindrical stationary cylinder 22 installed on an auxiliary cover 21 fixed to a motor cover 20.

The motor cooling water flows into the casing 9 through the motor cooling system piping 11 at the lower end of the casing 9, and flows into the casing 9 through the
When the pump is in operation, the pressure increases through the through hole 16 provided in the ice disk 15, rises, and flows out through the motor cooling system piping 10 at the upper end of the casing 9.

9 shows a detailed cross section of the vicinity of the anti-reverse device 23 in FIG.
In addition, the top surface of the reverse rotation preventer 23 is shown in FIG.

That is, a plurality of rotatable jam blocks 24 are arranged circumferentially in the rotating cylinder 19, and are pressed against the stationary cylinder 22 by a rotation spring 26 provided around the jam block rotating shaft 25 when the pump is stopped.

When the pump is started from this state, the jam block 24 is in contact with the stationary cylinder 22 at the beginning of rotation;
As the pump speed increases, the centrifugal force of the jam block 24 becomes greater than the pressing force of the spring 26, the jam block 24 comes out of contact with the stationary cylinder 22, and there is no resistance to the rotation of the pump shaft 2.

On the other hand, when the pump shaft 2 attempts to rotate in the reverse direction from the state shown in FIG.
2. Resistance to rotation increases depending on the positional relationship between which contact portion and the rotating shaft 25, thereby preventing reverse rotation.

(Problem to be solved by the invention) Generally, multiple internal pumps are installed in a nuclear reactor, so even if some internal pumps stop operating for some reason, other internal pumps continue to operate as they are. There is a case to continue.

However, in this case, a backflow occurs at the opening between the impeller 3 and the differential user 4 of the stop pump, and the fluid force of this backflow causes the stop pump to rotate in the opposite direction, thereby reducing the core flow rate compared to the case without reverse rotation. This may lead to a decrease in plant output.

Further, if the pump rotates in the opposite direction, abnormal vibrations may occur in the pump shaft, and the pump body may be damaged due to bearing wear and the like. For this reason, the internal pump is provided with the above-mentioned reverse rotation preventer 23 to prevent reverse rotation of the pump shaft 1 and 2.

However, the conventional reverse rotation preventer 23 has a structure in which minute dust present in the cooling water tends to accumulate, and when the dust accumulates near the rotating shaft 16, the rotation of the jam block 24 is hindered, and the jam block 24 is moved to the stationary side. cylinder 22
The pump shaft 2 is stuck in a non-contact state, and reverse rotation of the pump shaft 2 cannot be prevented.

The purpose of the present invention is to provide a reverse rotation preventer for an internal pump that can reliably prevent reverse rotation of the stopped pump when some of the internal pumps are stopped for some reason during Plan 1 operation. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a pump shaft having a motor section in which a rotor and a stator are incorporated along the inner axis direction of a vertically elongated casing, and a pump shaft to which the rotor is attached. In the reverse rotation preventer for an internal pump, a thrust disk is attached to the lower end of the thrust disk, a rotation side cylinder is provided on the lower surface of the thrust disk, and a stationary side cylinder is fitted to the rotation side cylinder via a jam block. The rotating cylinder is composed of an inner cylinder and an outer cylinder, and the inner cylinder is provided with a through hole in the radial direction, and a motor cooling water flow path is formed between the inner cylinder and the outer cylinder.

A stationary cylinder consisting of the inner cylinder and the outer cylinder is disposed on the outer periphery of the rotating cylinder via a jam block, and a motor cooling water flow path is formed between the inner cylinder and the outer cylinder, and the motor cooling water flow path is connected to this flow path. It is characterized in that a plurality of communicating through holes are formed in the inner cylinder.

(Function) While the pump shaft is rotating, motor cooling water flows through the through hole provided in the inner cylinder of the rotating cylinder due to centrifugal force, and descends through the annular flow path between the inner cylinder and outer cylinder of the rotating cylinder. do. This flow path prevents crud contained in the motor cooling water from accumulating on the rotating side of the pump during operation. Therefore, rotation of the jam block can be prevented from being obstructed, and a stopped internal pump can be prevented from rotating in reverse due to backflow from other rotating internal pumps.

(Example) A first example of the present invention will be described with reference to FIGS. 1 and 2. Incidentally, FIG. 2 is a cross-sectional view taken along the direction of arrows ``■=■'' in FIG. 1.

In Figures 1 and 2, Figures 9 and 10 of the conventional example
The same parts as in the figures are given the same reference numerals, and the explanation of the overlapping parts will be omitted.

In FIG. 1, a reverse rotation preventer 23a of the internal pump in the first embodiment has a rotation side cylinder 19a attached to a disk-shaped thrust disk 15 fixed to the pump shaft 2 by a coupling stud 13a and a nut 14. There is. The rotating cylinder 19a consists of an inner cylinder 27 and an outer cylinder 28 having an inner diameter larger than the outer diameter of the inner cylinder 27, which are fixed to each other. A flow path 29 is formed. A plurality of through holes 30 are provided in the inner cylinder 27 . As shown in FIG. 2, the jam block 24 is freely rotatable about a rotating shaft 25, and is pressed against the stationary cylinder 22 by a rotating spring 26 attached around the rotating shaft 25 when the pump is stopped.

When the pump rotation speed increases, the centrifugal force applied to the jam block 24 becomes greater than the pressing force of the rotation spring 26, the jam block 24 comes out of contact with the stationary cylinder 22, and there is no resistance to the rotation of the pump shaft 2. While the pump is rotating, the motor cooling water near the rotation side cylinder 9a is supplied to the inner cylinder 27 by centrifugal force (passes through the cut through hole 30, descends through the flow path 29, and flows between the lower end of the inner cylinder 27 and the motor cover 2).
It flows out to the lower side of the inner cylinder 27 through the gap 0.

Therefore, even if the motor cooling water contains dust such as crud, the dust is less likely to accumulate in the rotating portion of the jam block 24, and malfunctions due to jam block 24 sticking are prevented.

According to this embodiment, if the internal pump stops for some reason, the jam block 24 installed on the rotating cylinder 19a is reliably pressed against the stationary cylinder 22 by the spring 17, and the friction force causes the pump shaft to 2 can be reliably prevented from rotating in reverse.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 to 6.

In the drawings, the same or corresponding parts as in FIGS. 1 and 2 will be described with the same reference numerals. In this second embodiment, the rotating cylinder 19a shown in FIG. 3 and the stationary cylinder 22a shown in FIG. 4 are combined to form a reverse rotation preventer.

That is, in the second embodiment, as shown in FIG. 3, the rotating cylinder 19a has a jam block 24 attached to its outer surface, and as shown in FIG. 4, the stationary cylinder 22a has an inner cylinder. 27a and an outer cylinder 28a, and an inner cylinder 27a.
A plurality of through holes 30a are provided in the inner cylinder 27a and a motor cooling water passage 29a is formed between the inner cylinder 27a and the outer cylinder 28a. In addition to the through hole 30a, the inner cylinder 27a has a vertical hole 30b1, a horizontal hole 30c, and a motor cooling water passage hole 30d on the bottom surface. 3 in the figure indicates the lid. The lid 31 can be removed and washed with water together with the auxiliary cover at the lower end of the motor case during regular inspections.

Next, the operation will be explained with reference to FIGS. 5 and 6. However, when the pump is stopped, the jam block 24 is in light contact with the stationary cylinder 22a due to the rotation spring 26. The jam block 24 is manufactured so that its center of gravity is located on the left side of the jam block rotating shaft 25. When the pump starts rotating in the forward direction as shown in FIG.
Under the contact action with a, it rotates clockwise around the rotating shaft 25, creating a gap 32. At this time, the side of the jam block 24 remote from the rotating shaft 25 is the stationary side cylinder 22.
A first stop pin 33 is provided so as not to come into contact with a. Crud, dirt, rust, etc. that have entered the gap 32 pass through a plurality of vertical holes 30b provided in the stationary cylinder 22a and are deposited in the flow path 29a due to the action of centrifugal force. When the pump starts to rotate in the opposite direction as shown in FIG. 6, the jam block 24 rotates counterclockwise around the rotating shaft 25 due to the action of contact with the stationary cylinder 22a, and rotates from the stationary cylinder 22a. This serves as a mechanism for transmitting a large braking force to the side cylinder 19a. Also, jam block 24
a second stop pin 34 to prevent excessive rotation of the
is set up.

FIG. 7 shows the change in plant heat output when the reverse rotation preventer malfunctions and the reverse rotation occurs and the reverse rotation is operated normally. If a tripped pump can be reliably prevented from rotating in reverse according to the present invention, a significant economic effect can be expected compared to the case where a tripped pump rotates in the opposite direction.

If the tripped pump is not fixed, it is expected that the tripped pump will reverse at a high speed that exceeds the normal pump rotation speed, and there is a strong possibility that the rotation will become extremely unstable fluid-dynamically, and in some cases, other health problems may occur. It also becomes necessary to lower the rotation speed of the operating pump. In this case, the effect of the present invention is even greater because the heat output is further reduced.

[Effects of the Invention] According to the present invention, a flow path for motor cooling water is provided to prevent dirt from accumulating in the jam block rotating portion on the reverse rotation side, so that the rotation of the jam block is no longer restricted by dirt, and the pump shaft is free to flow. Reverse rotation can be reliably prevented. Therefore, it is possible to reduce the backflow from the stopped pump section and suppress a decrease in plant output due to a decrease in core flow rate.

Furthermore, damage to the stopped pump body, such as abnormal vibration of the pump shaft and wear of the bearings due to reverse rotation, can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view partially showing a side view of a first embodiment of a reverse rotation preventer for an internal pump according to the present invention, and FIG. A cross-sectional view shown in
3 to 6 are for explaining the second embodiment of the present invention, in which FIG. 3 is a longitudinal sectional view of a rotating cylinder, FIG. 4 is a longitudinal sectional view of a stationary cylinder, and FIG. 5 is a longitudinal sectional view of a stationary cylinder. Figure 6 is a cross-sectional view showing only the main parts of the state during forward rotation, Figure 7 is a cross-sectional view showing only the main parts of the state during reverse rotation, and Figure 7 shows the effect of the present invention.Thermal output and number of trips Bar graph diagram showing the relationship between
The figure is a vertical cross-sectional view showing an internal pump, Figure 9 is a vertical cross-sectional view showing a partial side view of a conventional internal pump anti-reverse device, and Figure 10 is an enlarged view in the X-X arrow direction of Figure 9. FIG. 1...Pressure vessel, 2...Pump shaft 3
... Impeller, 4... Differential user 5...
・Stretch tube 6...Rotor, 7...Stator 8...
Motor part, 9... Casing 10... Motor cooling system piping 11... Motor cooling system piping 12... Purge water system piping 13... Coupling stud 14... Nut, 15... Thrust disk 16・
...Through hole, 17...Upper thrust bearing 18...Lower thrust bearing 19...Rotating side cylinder 20...Motor cover 21...Auxiliary cover, 22...Stationary side cylinder 23
...Reversal preventer, 24...Jam block 25...
・Rotation shaft, 26...Rotation spring 27...Inner cylinder, 28.
... Outer cylinder 29 ... Channel, 30 ... Through hole 31 ... Lid, 32 ... Gap 33 ... First stop pin 34 ... Second stop pin

Claims (2)

[Claims] (1) It has a motor section in which a rotor and a stator are installed along the axial direction in a vertically elongated casing, a thrust disk is attached to the lower end of the pump shaft to which the rotor is attached, and the thrust disk rotates on the lower surface of the thrust disk. In the reverse rotation preventer for an internal pump in which a side cylinder is provided and a stationary side cylinder is fitted to the rotating side cylinder via a jam block, the rotating side cylinder is composed of an inner cylinder and an outer cylinder, and the rotating side cylinder is composed of an inner cylinder and an outer cylinder. A reverse rotation preventer for an internal pump, characterized in that a through hole is provided in the radial direction in the inner cylinder and a motor cooling water flow path is formed between the inner cylinder and the outer cylinder. (2) A stationary cylinder consisting of the inner cylinder and the outer cylinder is arranged on the outer periphery of the rotating cylinder via a jam block, and a motor cooling water flow path is formed between the inner cylinder and the outer cylinder. The internal pump reverse rotation preventer according to claim 1, wherein a plurality of through holes are formed in the inner cylinder and communicate with the passages.