JPS58184369A - Leak prevention device of shaft seal portion - Google Patents

Abstract

PURPOSE:To automatically prevent the fluid leak from a shaft seal portion while a pump is at halt by controlling a clearance between a piston and a sleeve fitted to a shaft by means of a pump discharge pressure. CONSTITUTION:During a pump operation, a discharge side pressure higher than that of a suction side flows into the right side opposite to an impeller of a cylinder 5 through a pressure guide pipe 10 by means of the pumping-up action of the impeller 4, thereby a piston 6 is moved to the left against the force of a spring 7, and a clearance 11 with a sleeve 2 is expanded. On the other hand, when the pump is stopped, the impeller 4 ceases its pumping-up action, the suction pressure and discharge pressure of the pump become equal, thus pressures applied to both sides of the piston 6 become equal. Accordingly, the piston 6 is moved to the right by means of the force of the spring 7 and is brought into close contact with the left end face of the sleeve 2 to close the clearance 11. Therefore, the inside of the pump is cut off from the atmosphere, and the fluid in the pump is prevented from leaking into the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing fluid in a pump from leaking from a shaft seal when the pump is stopped.

As shown in Fig. 1, as a means to prevent the fluid inside the pump from leaking to the outside from the shaft seal when the pump is stopped,
A seal ring 12t is attached to the sleeve 2 attached to the shaft 1 of the pump 7 via a key 13 and a spring 14 so as to be able to swing in the axial direction, and the surface 12a of the seal ring 12 facing the pressure reducing case 15 is sealed. A leakage prevention device consisting of a structure formed on a surface was previously submitted.

In such a structure, the mass of the seal ring 12 must be sufficiently large in order to overcome the wear force of the key 13 and the force of the spring 114 and move the seal ring 12 in the axial direction. Also, sleeve 2 and seal ring 1
2, a gap is required to facilitate movement of the seal ring 12.

However, if a gap like the one above is provided, seal ring 1
Since the shaft 2 rotates eccentrically from the center of the shaft by the amount of the clearance, there is a risk that the balance of the shaft system may be lost and a fii movement may occur. Furthermore, since the spring 14 is attached to a rotating body, it is affected by centrifugal force, making it difficult to analyze the water sealing effect due to the spring force.

In view of the above, an object of the present invention is to provide a device that prevents fluid from leaking from the shaft seal when the pump is stopped without being operated from outside by human power or a special signal. A cylinder containing a freely movable piston is provided in the pump casing, the cylinder is communicated with the pump discharge side, and a spring metal is provided to constantly bias the piston in a direction opposite to the pump, and the cylinder is attached to the piston and the shaft. The feature is that the gap between the sleeve and the sleeve is controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS All drawings of an embodiment of the present invention will be described below.

In Fig. 2, 1 is a pump shaft, 2 is a sleeve attached to the pump shaft 1, and 3 is a pump casing that houses an impeller 4 attached to the pump shaft 1. A labyrinth seal 3a is provided opposite to. 5 is a cylinder provided in the axial direction within the pump casing 3; 6 is a piston housed in the cylinder 5 so as to be slidable in the axial direction;
The head 6a of the piston 6 forms an appropriate gap 11ffi with the sleeve 2 during pump operation. 7 is a spring provided between the pump casing 3 and the cylinder head 6a, 8 is a sealing gasket provided between the sliding part of the piston 6a and the pump casing 3, and 10 is a cylinder 50 on the discharge side of the impeller pump. 9 through a pressure impulse pipe.

Next, the operation of this embodiment configured as described above will be explained.

During pump operation, due to the pumping action of the impeller 4, the pressure on the discharge side, which is higher than the suction side, is transferred to the cylinder 5 via the impulse pipe 10f.
0 Since the flow flows to the opposite side of the impeller (right side), the piston 6 moves to the left against the force of the spring 7, so the gap 1 with the sleeve 2 is reduced.
1 is expanded.

On the other hand, when the pump stops, the impeller 4 ceases to pump water, so the suction side pressure and the discharge side pressure of the pump become equal, so the pressures acting on both sides of the piston 6 also become equal. For this reason, the piston 6 is moved to the right by the force of the spring 7 and comes into close contact with the left end surface of the sleeve 2, closing the gap 11, so that the inside of the pump and the atmosphere are cut off.
．． It is possible to prevent the fluid inside the pump from leaking to the atmosphere.

1.1 In particular, the fluid handled by nuclear reactor feed water pumps and boiler feed water pumps is expensive water whose quality has been adjusted to protect nuclear reactors, boilers, and the like. Furthermore, although the amount of water handled by the reactor feed pump is small, it is a fluid containing radioactive substances with a long half-life, so water leaking from the shaft seal also needs to be treated to reduce radioactivity. It is desirable that leakage from the shaft seal is as small as possible. Therefore, this embodiment is most suitable for the water supply pump.

By preventing leakage from the shaft seal when the pump is stopped, various effects include reducing the amount of water fed by the pump, reducing water quality adjustment costs, reducing water supply power and ease of water supply equipment, and reducing leakage treatment costs. You can wander around.

[Brief explanation of the drawing]

Figure 1 is a schematic cross section showing the previously proposed shaft seal leakage prevention device.
FIG. 2 is a sectional view showing an embodiment of the shaft seal leakage prevention device according to the present invention. 2...Sleeve, 3...Pump casing, 5...
・Cylinder, 6... Piston, 7... Spring, 11.
··gap. 1st item

Claims (1)

[Claims] A cylinder containing a piston movable in the axial direction is provided in the pump casing, the cylinder is communicated with the pump discharge side, the piston is provided with a spring that constantly biases it toward the opposite side of the pump, and the piston and the shaft A leakage prevention device for a shaft seal, characterized in that the gap between the shaft seal and the sleeve attached to the shaft is controlled.