JPH07113892A - Water seal for internal pump - Google Patents

Abstract

PURPOSE:To provide a water seal for internal pump without leaking of reactor water during maintenance. CONSTITUTION:A long size hollow pipe shaft 30 is inserted in a casing 3 and the upper end of the hollow pipe shaft 30 is inserted in a plug 31. The plug 31 is attached water-sealed into a diffuser boss 13. The lower end of the hollow pipe shaft 30 penetrates the bottom of the casing 3 and extends from the cylinder 35 provided below the casing 3 to outside. The lower end side of the hollow pipe shaft 30 is water-sealed to the lower part of the cylinder 35 putting an end plug 37 in between. To the hollow pipe shaft 30 inside the cylinder 35, a piston 38 is attached, which is raised by the pressurized water from a pressurized water inlet pipe 39 and lowered by that from a pressurized water outlet pipe 40. A large diameter shaft end 32 is placed at the upper end of the hollow pipe shaft 30, where pure water flows in.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a watertight device for an internal pump used in an improved boiling water nuclear reactor to prevent leakage of reactor water during maintenance of the internal pump.

[0002]

2. Description of the Related Art An internal pump conventionally used in an improved boiling water reactor will be described with reference to FIG.

As shown in FIG. 5, the internal pump is roughly divided into a pump section 2 located inside the reactor pressure vessel 1, and a motor section 4 housed in a casing 3 located outside the reactor pressure vessel 1. It consists of The pump unit 2 includes a diffuser 6 provided inside the shroud 5 and the reactor pressure vessel 1, and an impeller 7 provided in the diffuser 6.

The impeller 7 is connected to the upper end of the pump shaft 8, and the lower part of the pump shaft 8 is the motor unit 4.
It is inserted inside. The motor unit 4 rotates the pump shaft 8 and the impeller 7, and is composed of a rotor 11 and a stator 12 provided between an inner can 9 and an outer can 10 inside the casing 3.

The diffuser 6 is mounted on the upper end surface of a stub tube 14 which is erected from the inner surface of the reactor pressure vessel 1 via a diffuser boss 13 via packing (not shown), and the diffuser boss 13 is a stretch tube 15 It is pressed down and fixed by the to seal the reactor water in a watertight manner.

Stretch tube 15 is a tightening nut at the bottom
It is fastened by 16 and fixed to the inner surface of the casing 3. A secondary seal 17 is provided below the tightening nut 16, and a pressurized water pipe 18 is connected to the secondary seal 17.
A leak water pipe 19 is provided above the pressurized water pipe 18.

A motor flange 20 is attached to the lower end flange portion of the casing 3 with stud bolts 21, and a small flange 22 is attached to the lower surface of the motor flange 20 with bolts 23. A coupling stud 24 is connected to the lower end of the pump shaft 8. In the lower part of the shroud 5, a reactor water flow hole 25 is formed. Reference numeral 26 is a key provided on the pump shaft 8, 27 is a cooling water inlet pipe connected to the lower portion of the casing 3, 28 is a cooling water outlet pipe connected to the upper portion of the casing 3, and 29 is a fixed impeller 7. It is a stud.

In the internal pump, however, the stretch tube 15 and the tightening nut 16 seal the reactor water in a watertight manner through the packing between the lower surface of the diffuser boss 13 and the upper surface of the stub tube 14. Also a secondary seal
The gap flow between the pump shaft 8 and the stretch tube 15 is sealed by 17 and a watertight seal is provided so that the reactor water does not enter the motor section 4.

[0009]

However, in the conventional watertight means for the internal pump, a shock due to air bubbles is generated when the pump shaft 8 is inserted during assembly, and it is difficult to easily position the pump shaft 8 at the allowable position. There is a problem that the secondary seal 17 is damaged due to these and the reactor water leaks.

If the residual reactor water is not noticed in the casing 3 and the motor flange 20 or the small flange 22 is removed, the residual reactor water leaks from the lower surface of the casing 3 and is rotated during operation. When the secondary seal comes into contact with the pump shaft 8 that operates, there is a problem that the sealing water leaks.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a watertight device for an internal pump that does not leave bubbles in the casing and is easy to handle.

[0012]

According to the present invention, a long hollow tube shaft is inserted in a casing, a plug is put on the end of the hollow tube shaft, and the lower end surface of the plug is set on the upper end surface of a stretch tube. The lower portion of the hollow tube shaft is closely contacted and extends through the flange closing the lower end surface of the casing, and the lower end surface of the flange surrounds the lower portion of the hollow tube shaft to provide a cylinder. And an outer peripheral surface of the lower end portion of the hollow tube shaft, an end plug is provided in the cylinder, and a pressurizing water inlet / outlet pipe is provided in the cylinder, and a piston is provided in the hollow tube shaft in the cylinder. .

Further, according to the present invention, a hollow cylindrical holder into which a pump shift is inserted is provided in a casing, and a large diameter flange having a through hole in a central portion is provided at a lower end of the holder, and the lower end surface of the large diameter flange is provided with the above-mentioned structure. A small diameter flange for closing the through hole is provided, and a tapered surface is formed on the inner surface of the upper end of the holder.

Further, according to the present invention, a backup seal is provided inside the diffuser boss and between the stepped portion of the pump shaft and the upper end surface of the stretch tube, and a closing flange is provided on the lower end surface of the casing, and the drain is provided on the closing flange. A hole is provided, a drain pipe is connected to the drain hole, a bottom plate communicating with the drain hole is provided on a lower surface of the closing flange, and a guard rising from the bottom plate is provided on an outer peripheral surface of the closing flange. To do.

[0015]

In the first aspect of the present invention, the plug is inserted inside the diffuser boss, and the hollow tube shaft is inserted into the casing before it is filled with fresh water, and the flange of the casing is sealed on the flange side. A fresh water pump injects water into the casing inlet pipe with a circulating water circuit installed on the casing inlet side.
Close the valve on the return side of the circulating water to fill the casing with fresh water.

Since the tip of the hollow pipe shaft is open in the plug, the hollow pipe shaft serves as a drainage channel. As for the method of filling the inside of the casing with fresh water, the water level gradually rises from below and the waste water begins to pass through the hollow tube shaft near the full level. Since the end of the hollow tube shaft is open to almost atmospheric pressure, all bubbles are drained.

Next, the waste water is continued while the hollow tube shaft is being lowered by water pressure, and if the opening surface coincides with the bottom surface of the flange at the lowermost end, the drainage system valve is closed. Then, the valve of the water supply system is closed and the fresh water pump is stopped. Then remove the plug and insert the propeller and pump shaft. In this way, the impeller and pump shaft can be attached without being affected by bubbles.

In the second invention, when the impeller and the pump shaft are attached, the impeller and the pump shaft are attached from above the furnace and are hung by their own weight. If a holder that can be supported from the tip of the pump shaft is installed in the casing, interference from the pump shaft will be eliminated, installation of the secondary seal will immediately prevent reactor water from entering the casing, and the shaft guide by the holder will prevent reactor water leakage. Be useful.

In the third aspect of the invention, when the stud is loosened and overflow water is generated from the flange joint surface, it is received by the guard and is guided to the drainage port of the flange to prevent scattering. As a result, it is not necessary to discharge again after a lapse of time.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the watertight device for an internal pump according to the present invention will be described with reference to FIGS. In FIG. 1, the same parts as those in FIG. 5 are designated by the same reference numerals, and the description of the overlapping parts will be omitted.

In FIG. 1, reference numeral 30 is a long hollow tube shaft,
The tip of the hollow tube shaft 30 is inserted into a plug 31 that is previously inserted into the diffuser boss. The plug 31 is inserted in contact with the inner surface of the diffuser boss 13, and its lower end surface is in close contact with the upper end surface of the stretch tube 15. A large-diameter shaft end 32 is provided at the tip of the hollow pipe shaft 30, and the plug 31
A stud 33 is attached to the upper end surface of the. A flange 34 having the same diameter as this flange portion is attached to the lower end flange portion of the casing 3, and a thin cylinder 35 is connected to the lower surface of the flange 34. The lower portion of the hollow tube shaft 30 is inserted into the center of the flange 34 via a seal 36, and the end of the hollow tube shaft 30 projects inside the cylinder 35.

A space between the cylinder 35 and the hollow tube shaft 30 is sealed by an end plug 37. A piston 38 is attached to the outer peripheral surface of the hollow tube shaft 30 in the cylinder 35. The cylinder 35 is provided with a pressurized water inlet pipe 39 at the lower part and a pressurized water outlet pipe 40 at the upper part, but water can be supplied and drained from any of the pipes 39, 40. Lower support on outer surface of flange 34
41 are attached, and upper supports 42 are attached to the lower end flanges of the casing 3, respectively.

In FIG. 1, before the impeller 7 and the pump shaft 8 are mounted, the inside of the diffuser boss 13 is closed with a plug 31 to seal the reactor water, and then a tightening nut 16 is fitted into the stretch tube 15 and the secondary nut is inserted. Provide a seal 17,
The leak pipe 19 and the pressurized water pipe 18 do not pass water, respectively. In addition, while the pressurized water is being supplied to the piston 38 from the pressurized water inlet pipe 39, the upper and lower supports 41, 42
Is engaged with a pair of screw rods (not shown), and the screw rods are rotated to incorporate the hollow tube shaft 30 into the casing 3.

The end plug 37 closes the cylinder 35, but the hollow tube shaft 30 can slide. Similarly, a portion where the hollow tube shaft 30 penetrates the flange 34 can slide, but does not leak. The end plug 37 is also sealed so as not to leak.

When fresh water is passed through the cooling water inlet pipe 39 and the cooling water outlet pipe 40 is closed, the casing 3 is filled with fresh water, but overflows from the shaft end 32 of the hollow pipe shaft 30 and is discharged.
Along with that, the bubbles are drained. Provide an appropriate orifice, etc. at the shaft end 32, and use a hollow pipe shaft when the drainage increases.
The pressurized water is sent from the pressurized water outlet pipe 40 to push down 30. A hose is connected to the end of the hollow pipe shaft 30, and the hollow pipe shaft 30 is lowered to the flange 34 without restriction so that the throttle valve is closed and the valve of the cooling water inlet pipe 27 is closed. Can fill with no fresh water. FIG. 2 is a piping system diagram showing the water supply / drainage system of the fresh water.

That is, the cooling water inlet pipe 27 of the casing 3
A normally open valve 43 is attached to the cooling water outlet pipe 28, and a cooling water return pipe 44 is connected to the cooling water outlet pipe 28 side to cool and return the pipe 44.
The terminal of is provided in the water tank 45. A foot valve 46 is immersed in the water tank 45, and the foot valve 46 is connected to a cooling water pump 47.

The discharge side of the cooling water pump 47 is connected to the cooling water inlet pipe 27 via two normally open valves 43, 43 cooler 48 and a normally open valve 43. A normally open valve 49 branches between the two normally open valves 43, 43 between the cooling water pump 47 and the cooler 48, and the normally open valve 49 is the cooling water return pipe 44.
Connected to.

On the other hand, the fresh water circulation flow path into the casing 3 is from the foot valve 46 of the fresh water tank 50 to the fresh water pump 51,
Cooling water inlet pipe via normally open valve 43 and normally closed valve 49
A fresh water supply pipe 54 connected to 27, and a fresh water return pipe that returns from the discharge side of the hollow pipe shaft 30 in the casing 3 to the fresh water tank 50.
It consists of 52.

Inlet branch pipe 55 branched from the fresh water supply pipe 54
Is connected to the inlet side of the cooler 48 via the normally open valve 43, and the outlet side of the cooler 48 is connected to the fresh water return pipe 52 via the check valve 53 by the outlet branch pipe 56.

Next, a second embodiment of the watertight device for an internal pump according to the present invention will be described with reference to FIG.

FIG. 3 shows a state in which the hollow cylindrical holder 57 is incorporated in the casing 3 when the impeller 7 and the pump shaft 8 are inserted. That is, a holder 57 for inserting the pump shaft 8 is provided in the casing 3, and this holder 57
A large diameter flange 59 having a through hole 58 in the center is provided at the lower end of 57, and a small diameter flange 60 for closing the through hole 58 is attached to the lower end surface of the large diameter flange 59 with a bolt 62.

A taper surface 61 is formed on the inner surface of the upper end of the holder 57. A stud 63 protruding from the bottom surface of the pump shaft 8 into the through hole 58 is provided, and a screw rod 64 is screwed into and engaged with the upper support 41. The lower flange of the casing 3 and the large-diameter flange 59 are fastened and fixed by a stud 65.

The impeller 7 and the pump shaft 8 are fitted integrally, but the impeller 7 is fitted inside the inlet of the diffuser 6, and the pump shaft 8 passes from the inside of the diffuser boss 13 through the inside of the stretch tube 15. Pressurized water is added to the secondary seal 17 to seal the minute gap between the stretch tube 15 and the pump shaft 8 and leakage, and the clean water in the casing 3 is discharged.

Next, the holder 57 is inserted, the pressurized water is slightly lowered, the pump shaft 8 is lowered along the Taber surface 61 of the holder 57, and the center of the pump shaft 8 is corrected and attached. The small-diameter flange 60 is a central pipe plug that is used to take out the holder 57 after checking for leaks, and a hose can be attached to the small-diameter flange 60 in advance.

Next, a third embodiment of the watertight device for an internal pump according to the present invention will be described with reference to FIG.

In the third embodiment, a closing flange 66 is provided on the lower end surface of the casing 3, a drain hole 67 is provided in the closing flange 66, a drain pipe 68 is connected to the drain hole 67, and the drain hole 67 is connected to the drain hole 67. A bottom plate 69 that communicates is provided on the lower surface of the closing flange 66, and the bottom plate 69 is provided on the outer peripheral surface of the closing flange 66.
It is provided with a guard 70 that stands up from.

Further, a backup seal 71 is provided inside the diffuser boss 13 and between the stepped portion of the pump shaft 8 and the upper end surface of the stretch tube 15, and the secondary seal 17 is provided.
Are backing up.

The secondary seal 17 injects pressurized water from the pressurized water pipe 18 to seal the outer circumference of the pump shaft 8 and the inner circumference of the casing 3 while the pump shaft 8 is stopped.
When the secondary seal 17 is worn, for example, the backup seal 71 seals. The backup seal 71 is an umbrella-shaped elastic body, and the lower part is an open enclosure.

When the stretch tube 15 is crowned from above, before the reactor water leaking from the gap between the pump shaft 8 and the diffuser boss 13 flows into the gap between the outside of the pump shaft 8 and the inside of the stretch tube 15, The backup seal 71 functions to seal on the upper surface of the stretch tube 15.

The wear of the secondary seal 17 is mainly caused by sliding or rotating with respect to the pump shaft 8 side, and is caused at the contact surface between the secondary seal 17 and the pump shaft 8. Similarly, the backup seal 71 is also considered so as not to come into contact with the stationary stretch tube when the pump shaft 8 rotates.

That is, during operation, the pump shaft 8 rises, the backup seal 71 does not contact the stretch tube 15, and when stopped, the pump shaft 8 descends due to reactor water pressure and its own weight. Cover with 15 and heat the secondary seal 17 to enhance the sealing effect.

When the tightening stud of the closing flange 66 is loosened when there is residual water in the casing 3, the closing flange 66 overflows from the loose portion of the contact surface and scatters around.
It is received by the guard 70 and made to flow down the drain pipe 68 along the outer periphery of the closing flange 66. The bottom plate 69 is integral with the guard 70 and also with the outer periphery of the closing flange 66. In FIG. 4, reference numeral 72 is a thrust bearing box, 73 is a nut box, and the nut box 73 is moved up and down by a screw rod 64.

[0043]

In the conventional example, the air bubbles trapped by the fresh water stored in the closed casing floats up at any time, which is not preferable for inserting the impeller and the pump shaft, but according to the first invention, Air bubbles can be removed in advance by the hollow tube shaft, which is effective for maintaining stretch tubes and secondary seals when inserting the pump shaft, and prevents reactor water from leaking during maintenance of the internal pump.

According to the second aspect of the invention, by providing the holder inside the casing, the interference by the pump shaft is eliminated, and the secondary seal can be maintained normally. The secondary seal contributes to the prevention of reactor water entry into the casing, and the guide of the pump shaft by the holder has the effect of preventing reactor water leakage.

According to the third invention, by providing the backup seal, it is possible to prevent the reactor water from flowing into the casing, and by using the closing flange, the leakage of the residual water is prevented and the environmental pollution is prevented. It can be prevented.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a watertight device for an internal pump according to the present invention.

FIG. 2 is a system diagram showing a fresh water circulation path of the watertight device in FIG.

FIG. 3 is a vertical sectional view showing a second embodiment of the watertight device for an internal pump according to the present invention.

FIG. 4 is a longitudinal sectional view showing a third embodiment of the watertight device for an internal pump according to the present invention.

FIG. 5 is a vertical sectional view showing a conventional internal pump.

[Explanation of Codes] 1 ... Reactor pressure vessel, 2 ... Pump section, 3 ... Casing,
4 ... Motor part, 5 ... Shroud, 6 ... Diffuser, 7
… Impeller, 8… Pump shaft, 9… Inner can, 10
... outer can, 11 ... rotor, 12 ... stator, 13 ... diffuser boss, 14 ... stub tube, 15 ... stretch tube, 16 ... tightening nut, 17 ... secondary seal, 18 ... pressurized water tube,
19 ... Leak water pipe, 20 ... Motor flange, 21 ... Stud bolt, 22 ... Small flange, 23 ... Bolt, 24 ... Coupling stud, 25 ... Flow hole, 26 ... Key, 27 ... Cooling water inlet pipe,
28 ... Cooling water outlet pipe, 29 ... Stud, 30 ... Hollow pipe shaft, 31 ...
Plug, 32 ... Shaft end, 33 ... Stud, 34 ... Flange, 35 ...
Cylinder, 36 ... Seal, 37 ... End plug, 38 ... Piston, 39 ...
Pressurized water inlet pipe, 40 ... Pressurized water outlet pipe, 41 ... Lower support,
42 ... Top support, 43 ... Normally open valve, 44 ... Cooling water return pipe, 45 ... Cooling water tank, 46 ... Foot valve, 47 ... Cooling water pump, 48 ... Cooler, 49 ... Normally closing valve, 50 ... Fresh water tank , 51 ... Fresh water pump, 52 ... Fresh water return pipe, 53 ... Check valve, 54 ... Fresh water supply pipe, 55 ... Inlet branch pipe, 56
… Outlet branch pipe, 57… Holder, 58… Through hole, 59… Large diameter flange, 60… Small diameter flange, 61… Tapered surface, 62… Bolts, 63… Studs, 64… Screw rods, 65… Studs, 66… Closure Flange, 67 ... Drain, 68 ... Drain pipe, 69
… Bottom plate, 70… Guard, 71… Backup seal, 72… Thrust bearing box, 73… Nut box.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Watanabe 4-7-7 Shiba, Minato-ku, Tokyo Aitel Technology Services Co., Ltd.

Claims (3)

[Claims] 1. A long hollow tube shaft is inserted into a casing,
A plug is placed on the end of the hollow tube shaft, the lower end surface of the plug is brought into close contact with the upper end surface of the stretch tube, and the lower portion of the hollow tube shaft extends through a flange that closes the lower end surface of the casing. The lower end surface of the flange is provided with a cylinder surrounding the lower portion of the hollow tube shaft, and an end plug is provided between the cylinder and the outer peripheral surface of the lower end portion of the hollow tube shaft, and the cylinder is provided with pressurized water. A watertight device for an internal pump, wherein an inlet / outlet pipe is provided, and a piston is provided on the hollow pipe shaft in the cylinder. 2. A hollow cylindrical holder into which a pump shaft is inserted is provided in a casing, a large diameter flange having a through hole in the center is provided at the lower end of the holder, and the through hole is provided at the lower end surface of the large diameter flange. Provide a small diameter flange to close,
A watertight device for an internal pump, wherein a taper surface is formed on an inner surface of an upper end portion of the holder. 3. A backup seal is provided inside the diffuser boss and between the stepped portion of the pump shaft and the upper end surface of the stretch tube, a closing flange is provided at the lower end surface of the casing, and a drain hole is provided in this closing flange. ,
An internal pump characterized in that a drain pipe is connected to the drain hole, a bottom plate communicating with the drain hole is provided on a lower surface of the closing flange, and a guard rising from the bottom plate is provided on an outer peripheral surface of the closing flange. Watertight device.