JPH11108201A - Shaft-sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a gas leak from a unit by preventing the abnormal wear of a carbon seal ring even when purge gas such as nitrogen gas is used. SOLUTION: This device has a plurality of seal units 3, 4, 5 arranged axially along a rotary shaft 1 in a space 23 defined between the rotary shaft 1 and a seal housing 2 surrounding the rotary shaft 1, and the seal housing 2 has an introduction hole 6 for introducing purge gas and communicating with the space 23 and a discharge hole 7 made inside the introduction hole 6 and for discharging internal gas or the mixed gas of the internal gas and the purge gas. A labyrinth seal 13 or a honeycomb seal is provided inside the unit on the inner peripheral surface of the seal unit 4 arranged between the introduction hole 6 and the discharge hole 7 and a carbon seal ring 15 is fitted in the inner peripheral surface outside the unit such that it can be freely projected and the carbon seal ring 15 is provided with lubricant such as molybdenum disulfide on the inner peripheral surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shaft sealing device used for a high-speed turbo machine such as a centrifugal compressor, and more particularly to a shaft sealing device used in an oil-free environment.

[0002]

2. Description of the Related Art In a conventional shaft sealing device of this type, if the seal gap is made small in order to suppress the leakage of gas inside the machine, the rotation shaft and the seal are raised due to a rise in the temperature of the rotation shaft and the seal and vibration of the rotation shaft. May cause an accident such as image sticking.

In order to cope with this, an injection-ejection seal has been proposed in which the seal gap is enlarged to supply a purge gas to the seal gap and to discharge the in-machine gas or a mixed gas of the gas and the purge gas from the seal gap. However, this requires the pressure of the purge gas to be maintained slightly higher than that of the gas to be discharged, so that there is a problem that the cost is increased and the reliability of the transient characteristic is lacking.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is that a space defined between a rotating shaft and a seal housing surrounding the rotating shaft is limited. A plurality of seal units are disposed along the axial direction of the rotating shaft, and a purge gas introduction hole communicating with the space in the seal housing and an in-machine gas or a mixed gas of the purge gas and the purge gas are discharged inside the machine. Holes are provided, a labyrinth seal or a honeycomb seal is provided on the inner peripheral surface of the inside of the seal unit located between the introduction hole and the discharge hole, and a carbon seal ring is fitted on the inner peripheral surface of the outer side of the machine so as to be freely retractable. The shaft sealing device is characterized in that a lubricant such as molybdenum disulfide is provided on the inner peripheral surface of the carbon seal ring.

[0005]

1 and 2 show an embodiment of the present invention.
Is shown in As shown in FIG. 1, a plurality (three in the figure) of annular seals is provided in a space 23 defined between the rotary shaft 1 and the seal housing 2 surrounding the rotary shaft 1 along the axial direction of the rotary shaft 1. The units 3, 4, and 5 are arranged at predetermined intervals.

In the seal housing 2, a purge gas inlet 6 and a discharge hole 7 for an in-machine gas or a mixed gas of the same and a purge gas are formed inside the machine, and the inlet 6 is formed in a casing 16. The discharge hole 7 communicates with the hole 8, and the discharge hole 7 communicates with the discharge hole 9 formed in the casing 15.

A labyrinth seal 10 is formed integrally on the inner peripheral surface of the first seal unit 3 located inside the discharge hole 7 on the machine side. A plurality of (three in the figure) annular grooves are provided on the inner peripheral surface of the third seal unit 5 located outside the introduction hole 6 on the machine side.
11 are bored at intervals in the axial direction, and a carbon seal ring 12 is fitted in each of the plurality of annular grooves 11 so as to be able to protrude and retract.

[0008] A second one located between the inlet hole 6 and the outlet hole 7
A labyrinth seal 13 is integrally formed on the inner peripheral surface of the inside of the seal unit 4, and a plurality of (two in the figure) annular grooves 14 are formed on the inner peripheral surface of the outer unit at intervals in the axial direction. A carbon seal ring 15 is fitted into each of the plurality of annular grooves 14 so as to be able to protrude and retract.

As shown in FIG. 2A, a plurality (three in the figure) of annular grooves 31 are formed in the inner peripheral surface of the carbon seal ring 15 at intervals in the axial direction. As shown in FIG. 2B, a lubricant 32 made of molybdenum disulfide or the like is rubbed into these grooves 31, and as shown in FIG. It is finished flush with the inner peripheral surface.

Reference numeral 17 denotes carbon seal rings 12 and 15.
, A radial flow labyrinth seal formed on the outer peripheral edge of the inboard end face of the flange portion 2a of the seal housing 2, and 19, 20, and 21 for clearance between the seal housing 2 and the casing 16. An O-ring 22 for sealing is an impeller fixed to the rotating shaft 1.

When the rotary shaft 1 is driven, the in-machine gas is urged by the impeller 22 and then blown out through a blowout flow path (not shown). A part of the in-machine gas pressurized by the impeller 22 enters the space 23 through the seal gap of the radial labyrinth seal 18, and then passes through the seal gap of the labyrinth seal 10 of the first seal unit 3. The pressure is gradually reduced.

On the other hand, a purge gas is supplied into the space 23 through the introduction holes 8 and 6, and a part of the purge gas flows out through the seal gaps of the plurality of carbon seal rings 12 of the third seal unit 5 sequentially, while the remaining gas flows out. Is gradually reduced in the process of flowing through the seal gap of the carbon seal ring 15 of the second seal unit 4 and the seal gap of the labyrinth seal 13 in this order, and then merges with the internal gas to form the discharge holes 7 and 9. It is discharged through.

The pressure of the purge gas is adjusted to be slightly higher than the pressure of the exhaust gas discharged through the discharge holes 7 and 9. However, when a dry gas having a low dew point, such as nitrogen gas, is used as the purge gas. Means that the carbon seal ring 15 is abnormally worn due to its poor slidability.
It becomes difficult to adjust the pressure difference between the purge gas and the exhaust gas, and the gas in the machine leaks to the outside.

However, since the lubricant 32 such as molybdenum disulfide is provided on the inner peripheral surface of the carbon seal ring 15, wear of the carbon seal ring 15 can be prevented. Can be easily adjusted, and it is possible to prevent the in-machine gas from leaking out of the machine.

If the sealing gap of the carbon seal ring 15 is reduced, the flow resistance of the purge gas to the discharge holes 7 and 9 can be increased, so that the flow rate of the purge gas can be reduced. Furthermore, if the seal gap of the labyrinth seal 13 is made larger than the seal gap of the carbon seal ring 15 and the seal gap of the labyrinth seal 10 of the first seal unit 3 is made equal to or larger than the seal gap of the labyrinth seal 13, Even if the shaft 1 vibrates, the labyrinth seals 13 and 10 can be prevented from contacting the rotating shaft 1.

In the above embodiment, three seal units 3, 4, and 5 are provided. However, three or more seal units can be provided. Two or more seal units can be arranged between them.

Further, instead of the labyrinth seal 13 of the second seal unit 4 and the labyrinth seal 10 of the first seal unit 3, a honeycomb seal can be formed.

Further, a lubricant such as molybdenum disulfide may be provided on the inner peripheral surface of the carbon seal ring 12 of the third seal unit 5.

[0019]

According to the present invention, a labyrinth seal or a honeycomb seal is provided on the inner peripheral surface of the inside of the seal unit located between the purge gas inlet and the exhaust gas for the internal gas or a gas mixture of the purge gas. At the same time, a carbon seal ring is fitted on the inner peripheral surface of the
Since a lubricant such as molybdenum disulfide is provided on the inner peripheral surface of the carbon seal ring, abnormal wear of the carbon seal ring can be prevented even when a dry purge gas having a low dew point such as nitrogen gas is used. Therefore, since the differential pressure between the purge gas and the exhaust gas can be easily adjusted, it is possible to reliably prevent the in-machine gas from leaking out of the machine, and to improve the reliability of the shaft sealing device.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing a processing procedure of a carbon seal ring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary shaft 2 Seal housing 3, 4, 5 Seal unit 6, 8 Inlet hole 7, 9 Outlet 10, 13 Labyrinth seal 12, 15 Carbon seal ring 18 Radial flow labyrinth seal 16 Casing 17 Garter spring 19, 20, 21 O Ring 22 Impeller 31 Groove 32 Lubricant

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Naoto Yonemura 1-1, Akunouramachi, Nagasaki City Inside Nagasaki Shipyard, Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A plurality of seal units are disposed in a space limited between a rotation shaft and a seal housing surrounding the rotation shaft along an axial direction of the rotation shaft, and communicate with the seal housing in the space. A purge gas introduction hole and a discharge hole for an in-machine gas or a mixed gas of the purge gas and the purge gas are formed on the inside of the machine, and a labyrinth seal is provided on the inside peripheral surface of the seal unit located between the introduction hole and the discharge hole. A shaft sealing device provided with a honeycomb seal, a carbon seal ring fitted on the inner peripheral surface of the outside of the machine so as to be freely retractable, and a lubricant such as molybdenum disulfide provided on the inner peripheral surface of the carbon seal ring. .