JP2645544B2 - Shaft sealing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft sealing device for a pump mainly used for pumping liquefied gas or hot water which is a high-pressure, low-boiling fluid.

[0002]

2. Description of the Related Art Conventionally, as a shaft sealing device for a pump for pumping a high-pressure low-boiling fluid such as liquid ammonia or hot water, a simple mechanical seal has been realized, knowing that its life and reliability are not ensured. Or use contact type mechanical seals arranged in opposite directions,
A purge fluid chamber is formed between the two mechanical seals,
For example, a shaft seal device of a double seal system in which a purge fluid different from a sealing fluid is supplied to the purge fluid chamber to cool the mechanical seal is used.

In the shaft seal device of the double seal type, a high pressure is applied to the first mechanical seal that seals the sealing fluid side from the sealing fluid side, so that the pressure of the purge fluid is reduced by the pressure of the sealing fluid. Higher to maintain its sealing function. More specifically, in the first mechanical seal, the pressure of the sealing fluid acts on one of the sealing rings pressed and urged toward the sealing fluid by the spring in a direction opposite to the pressing and biasing direction. When the pressure of the sealing fluid becomes high, the sealing ring is pressed against the urging force of the spring, and separates from the other sealing ring, so that the sealing function may be impaired. Therefore, the pressure of the purge fluid is higher than the pressure of the sealing fluid, and this pressure is applied from behind the one sealing ring, that is, the pressure acts as a back pressure,
By pressing and biasing the one sealing ring toward the other sealing ring, the contact state between the two sealing rings is maintained, so that the sealing performance is not impaired. However, in the shaft sealing device, as the pressure of the purge fluid is increased, the differential pressure between the atmosphere side and the purge fluid chamber is increased, so that the sealing function of the second mechanical seal that seals the atmosphere side is easily damaged. There was a problem.

Another example of the shaft sealing device is a tandem type double seal system in which non-contact type mechanical seals are arranged in opposite directions and a purge fluid chamber is formed between the two mechanical seals. However, since the sealing fluid is limited to gas, it cannot be applied to a high-pressure low-boiling fluid.

Therefore, as another shaft sealing device, there has been proposed a device in which a contact-type mechanical seal and a non-contact-type mechanical seal are arranged in tandem, and a purge fluid chamber is formed between the two mechanical seals (see, for example, Japanese Patent Application Laid-Open No. H11-157556). JP 6
-42650). In this shaft sealing device, a contact-type mechanical seal is arranged on the sealing fluid side, and a non-contact type mechanical seal is arranged on the atmosphere side.The pressure of the sealing fluid is pressed and urged by a spring. By acting as a back pressure on the sealing ring, the contact state between the one sealing ring and the other sealing ring is maintained, the pressure of the purge fluid is reduced, and the differential pressure with the atmosphere side is reduced. In addition, the sealing function of the non-contact type mechanical seal is prevented from being impaired.

[0006]

However, in the shaft sealing device using both the contact-type and non-contact-type mechanical seals, the contact-type mechanical seals are sealed with the mechanical seals in order to perform flushing. The need for both a sealed fluid supply system for supplying the fluid and a pressurized supply system for supplying the purge fluid to the purge fluid chamber makes the sealing system complex and bulky and expensive. There was a problem.
The present invention has been made in view of the above problems,
An object of the present invention is to provide a shaft sealing device that does not require a pressurized supply system for supplying a purge fluid to a purge chamber, and can simplify the structure and reduce costs.

[0007]

To solve the above-mentioned problems, a shaft sealing device according to the present invention comprises a contact type mechanical seal disposed on a sealed fluid side and a non-contact type mechanical seal disposed on an atmosphere side. The seal seals a gap between the casing and the rotating shaft, and forms a purge fluid chamber that supplies a purge fluid between the two mechanical seals.The pressure of the sealed fluid is reduced by a contact type. A shaft seal that acts as a back pressure on an axially slidable seal ring of the mechanical seal and applies the pressure of the purge fluid as a back pressure on an axially slidable seal ring of the non-contact type mechanical seal. The apparatus is characterized in that a throttle hole is formed in a predetermined portion of the contact-type mechanical seal to supply a purge fluid to the purge fluid chamber as a purge fluid by vaporizing the sealing fluid.

[0008]

According to the shaft sealing device having the above-described structure, the sealed fluid can be vaporized by the pressure drop when passing through the throttle hole and supplied to the purge chamber as the purge fluid. Therefore, a pressurized supply system for supplying the purge fluid to the purge chamber becomes unnecessary.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing one embodiment of the shaft sealing device of the present invention. This shaft sealing device is used for a pump for pumping a high-pressure low-boiling fluid such as liquid ammonia, for example. The gap between the casing C and the rotating shaft S is sealed by the non-contact type mechanical seal 2 arranged. Also,
A purge fluid chamber 3 for supplying a purge fluid is formed between the two mechanical seals 1 and 2, and a part of the sealing fluid A is supplied to the purge fluid chamber 3 as a purge fluid. I have.

The above-mentioned mechanical seals 1 and 2 are held by casings C via holding members 5 and 6 and rotary sealing rings 11 and 21 held integrally with a rotating shaft S via a shaft sleeve 4. The stationary sealing rings 12 and 22 and springs 13 and 23 for urging the stationary sealing rings 12 and 22 against the rotating sealing rings 11 and 21 are provided. The contact-type mechanical seal 1 slides the respective sealing end faces of the rotary sealing ring 11 and the stationary sealing ring 12 through a lubricating film made of the sealing fluid A, so that the sealing fluid A side and the purge fluid chamber 3 are in contact with each other. Is to be sealed. The stationary sealing ring 1
2 is located on the atmosphere B side with respect to the rotary seal ring 11, and is fitted to the retainer 14 in this state. The retainer 14 is attached to the holding member 5 so as to be slidable in the axial direction.
2 are allowed to move in the axial direction. The spring 13 for pressing and biasing the stationary sealing ring 12 is interposed between the back surface 14 a of the retainer 14 and the holding member 5. In addition, the rotary seal ring 11 is provided with respect to the shaft sleeve 4 fitted to the rotary shaft S so as to be integrally rotatable.
The fitting is performed with the movement in the axial direction restricted.

Further, between the outer periphery of the retainer 14 and the inner periphery of the holding member 5, the sealing fluid A is supplied to the back surface 14a side of the retainer 14, and the pressure of the sealing fluid A is applied to the retainer 14. That is, a gap 15 is provided for the stationary sealing ring 12 to act as a back pressure. A communication hole C1 is formed in the casing C and the holding member 5 so as to face a predetermined portion of the gap 15,
The communication hole C1 is connected to a sealing fluid supply system for taking in the sealing fluid A from a discharge portion of a pump and supplying the sealing fluid A to the gap 15, and the sealing fluid A supplied to the gap 15 through the communication hole C1. Thus, flushing of the contact type mechanical seal 1 can be performed.

The retainer 14 is provided with the clearance 1
A throttle hole H for communicating the purge fluid chamber 5 with the purge fluid chamber 3 is formed to penetrate in the radial direction. The throttle hole H reduces the pressure of the sealed fluid A and supplies the sealed fluid A to the purge fluid chamber 3 in a vaporized state. The diameter and the number of the holes are equal to the pressure P1 on the sealed fluid A side. The pressure difference ΔP from the pressure P2 of the purge fluid chamber 3 is set to, for example, 5 kg / cm ² .

On the other hand, the non-contact type mechanical seal 2
A dynamic pressure generating groove 21a having a spiral shape or the like is formed on the sealing end face of the rotary seal ring 21. The dynamic pressure generated by the relative rotation between the rotary seal ring 21 and the stationary seal ring 22 causes While keeping both in a non-contact state,
The purge fluid chamber 3 and the atmosphere B side can be sealed.

The stationary sealing ring 22 is located on the atmosphere B side with respect to the rotating sealing ring 21, and the inner peripheral side thereof is fitted to a retainer 24. The retainer 24 is attached to the holding member 5 so as to be slidable in the axial direction, whereby the stationary sealing ring 22 is allowed to move in the axial direction. The spring 23 for pressing and biasing the stationary sealing ring 22 is interposed between the back surface 24 a of the retainer 24 and the holding member 6. Further, the outer periphery of the stationary sealing ring 22 is fitted with a gap to the inner periphery of the holding member 6, and supplies the purge fluid in the purge fluid chamber 3 to the back surface 24 a side of the retainer 24, The pressure of the sealing fluid A acts as a back pressure on the retainer 24, that is, on the stationary sealing ring 22. The rotary seal ring 21 is fitted to the shaft sleeve 4 in a state where movement in the axial direction is restricted. The purge fluid chamber 3 is connected to the sealed fluid supply system via a communication hole C2 formed in the casing C and the holding member 5.

With the above configuration, the sealing fluid A can be supplied to the purge fluid chamber 3 as a purge fluid in a state of being vaporized through the throttle hole H, and the sealing fluid supplied to the purge fluid chamber 3 can be supplied. The fluid A can be supplied to the sealed fluid supply system and circulated through the communication hole C2. Therefore, a pressurized supply system for supplying the purge fluid to the purge fluid chamber 3 is not required, and the structure of the shaft sealing device can be simplified by that much, and the cost can be significantly reduced. Further, since the sealing fluid A supplied to the purge fluid chamber 3 is vaporized, there is no possibility that the sealing performance of the non-contact type mechanical seal 2 is adversely affected.

The shaft sealing device of the present invention is not limited to the above embodiment. For example, the throttle hole H may be formed in the rotary seal ring 11 or the stationary seal ring 12, and the rotary seal ring side may be formed. Various design changes can be made, such as a configuration in which the rotary shaft is slidably attached to the rotary shaft and is pressed and urged by a spring. Further, in the above embodiment, a low boiling point fluid such as liquid ammonia is described as an example of the sealing fluid, but the present invention can be similarly applied to a sealing fluid such as hot water.

[0017]

As described above, according to the shaft sealing device of the present invention, a part of the sealing fluid is supplied to the purge fluid chamber in a state of being vaporized through the throttle hole and used as the purge fluid. Therefore, a dedicated pressurized supply system for supplying the purge fluid to the purge fluid chamber is not required. For this reason, it is possible to simplify the structure of the shaft sealing device, and to achieve a unique effect that the cost can be reduced. Also, rather than a single mechanical seal,
There is an effect that the reliability of the shaft sealing device is significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a shaft sealing device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact-type mechanical seal 2 Non-contact-type mechanical seal 3 Purge fluid chamber 11 Rotary seal ring 12 Stationary seal ring 21 Rotary seal ring 22 Stationary seal ring A Sealed fluid B Atmosphere C Casing S Rotating shaft H Restrictor hole

Claims (1)

(57) [Claims] A gap between a casing and a rotating shaft is sealed by a contact type mechanical seal disposed on a sealed fluid side and a non-contact type mechanical seal disposed on an atmosphere side. A purge fluid chamber for supplying a purge fluid is formed between the two mechanical seals, and the pressure of the sealing fluid is applied as a back pressure to a sealing ring slidable in the axial direction of the contact type mechanical seal. In a shaft sealing device for applying a pressure of a purge fluid to a sealing ring slidable in an axial direction of a non-contact type mechanical seal as a back pressure, a predetermined portion of the contact type mechanical seal is vaporized with a sealing fluid. A shaft sealing device having a throttle hole for supplying a purge fluid to a purge fluid chamber.