JPS63665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mechanical seal suitable for sealing a considerably high temperature fluid, such as in a circulation pump in a nuclear power generation facility or a boiler pump in a thermal power generation facility.

Conventionally, when sealing relatively high-temperature fluids, it has been done to increase the circulating flow rate of the cooling liquid (sealing liquid) to cool the sealed end face, or to use a cooler with a large capacity to cool the sealing liquid. ing. However, doing so is undesirable because it makes the equipment and equipment unnecessarily complicated and large. Moreover, when the temperature of the fluid to be sealed rises above a certain level (e.g. 200℃ or higher),
It would be impossible to cool the sealed end surface to an appropriate temperature (for example, below 60°C) by simply implementing the measures described above, as the temperature of the fluid to be sealed would be transmitted to the sealed end surface. .

In view of these points, the present invention provides a method for effectively cooling the sealed end surface by preventing the temperature of the fluid from being transmitted to the sealed end surface as much as possible even if the fluid to be sealed is a high-temperature fluid. This configuration provides a mechanical seal that can exhibit a good sealing function.

The mechanical seal of the present invention that solves this problem includes a seal ring held by an annular retainer attached to a rotating shaft passing through the equipment casing, and a stationary seal ring that contacts the seal ring to form a sealed end surface. In the mechanical seal equipped with the annular retainer, the annular retainer reduces the gap between the inner circumferential surface of the device casing and the outer circumferential surface of the annular retainer in order to partition the sealing liquid side, which is the sealed end surface side, and the high temperature fluid side. a circulation groove is formed on the outer periphery of the sealing liquid side, and an annular heat isolation groove cut in the radial direction with a cutting depth that includes at least the axial extension area of the seal ring in the high temperature fluid side portion. It was formed.

A first embodiment of the present invention will be described below with reference to FIG.

In the figure, reference numeral 2 denotes a rotating shaft, and this rotating shaft 2 passes through the inside of the device casing 4. An annular retainer 8 is attached to the outer periphery of the rotating shaft 2. This annular retainer 8 is formed into an annular shape that closely fits the outer circumferential surface of the rotating shaft 2 and has a small gap between it and the inner circumferential surface 6 of the device casing 4 . A ring groove 10 is provided on the inner peripheral surface of the annular retainer 8, and an O-ring 12 is accommodated in this ring groove 10.
Labyrinth grooves 16 and annular heat shielding grooves 18 are formed alternately in the axial direction from the outer circumferential surface toward the inner diameter on the outer circumferential portion of the annular retainer 8 on the side of the high-temperature fluid 14 that is the fluid to be sealed. Furthermore, an annular recess 22 is formed in the end surface of the annular retainer 8 on the sealing liquid 20 side, and a seal ring 24 is installed in this recess 22 . This seal ring 24 is fixed to the annular retainer 8 with a key 26, and the seal ring 24 and the equipment casing 4
A sealed end face 3 is formed by contact with a stationary sealing ring 28 held at the side. Further, in the figure, 30 is an O-ring, and 32 is a reinforcing ring.

A plurality of circulation grooves 34 are provided in the outer circumference of the annular retainer 8 on the sealing liquid 20 side in the circumferential direction. This circulation groove 34 utilizes the rotation of the annular retainer 8 to form a cooling liquid, that is, a sealing liquid 20, which flows into the equipment casing 4 from an inflow hole (not shown) formed in the equipment casing 4 toward the sealed end surface 3. This is for self-circulation to the outflow hole 36, which cools the sealed end surface 3. The annular heat shielding groove 18 is cut radially inward from the outer periphery of the annular retainer 8, and the depth of the cut is set by positioning the groove bottom on the axial extension of the inner periphery of the seal ring 24. has been done. That is, the heat shielding groove 18 is cut in the radial inward direction with a cutting depth that includes the axially extending region of the seal ring 24 .

The operation of the device configured as above will be explained.

The fluid that has flowed into the heat isolation groove 18 rotates at approximately the same speed as the annular retainer 8 due to its viscosity. Therefore, the relative speeds between the fluid in the heat isolation groove 18 and the inner wall of the heat isolation groove 18 are approximately the same, and the thermal conductivity between the fluid and the inner wall is significantly reduced. Moreover, since the annular heat-insulating groove 18 is cut to a depth such that the groove bottom is located on the axial extension of the inner diameter of the seal ring 24, a large amount of high-temperature fluid is introduced. Therefore, the high temperature fluid 14
The amount of heat transferred from the annular retainer 8 to the sealing end face 3 via the annular retainer 8 and the seal ring 24 is significantly reduced. In other words, the fluid in the heat isolation groove 18 functions as a kind of isolation material, and the temperature of the fluid 14 is hardly transmitted to the sealed end surface 3.

Furthermore, since a labyrinth groove 16 is formed on the outer circumference of the annular retainer 8, the device casing 4
Coupled with the fact that the gap between the inner circumferential surface 6 of the annular retainer 8 and the outer circumferential surface of the annular retainer 8 is small, the high-temperature fluid 14 is prevented from entering the sealed end surface 3 side, that is, the sealing liquid 20 side, through the gap as much as possible.

In this way, the temperature of the high temperature fluid 14 is lowered to the sealed end surface 3.
Since the sealing fluid 20 cools the sealed end face 3 extremely effectively, even if the fluid to be sealed is a high-temperature fluid, the temperature of the sealed end face 3 can be maintained appropriately. This results in a good sealing mechanism.

This is also clear from the experimental results shown in FIG. This experiment was conducted using the mechanical seal having the configuration of the above embodiment and a mechanical seal having a configuration in which the heat isolation groove 18 and the labyrinth groove 16 were eliminated from this configuration, that is, a configuration provided only with the circulation groove.
The temperature distribution in the axial direction from the back surface 8a of the annular retainer 8 to the sealed end surface 3 is compared and measured when a 170° C. fluid is sealed. In FIG. 2, the temperature gradient curve in the former mechanical seal is indicated by _S1 , and the temperature gradient curve in the latter mechanical seal is indicated by _S2 .

According to FIG. 2, although the sealed end surface is cooled by the sealing liquid under the same conditions, in the case of the latter mechanical seal, the back surface 8a of the annular retainer 8
The temperature difference Δt ₂ between and the sealed end surface 3 is small (approximately 50℃)
In this case, the sealed end face 3 was hardly cooled (as a result of measurement, the temperature of the sealed end face 3 was approximately 120°C),
In the case of the former mechanical seal, both of the above 8.
The temperature difference Δt ₁ between a and 3 is large (approximately 110°C), and the sealed end face 3 is effectively cooled to maintain an appropriate temperature (approximately 60°C).
It is understood that this will be maintained. In the case of the former mechanical seal, that is, the mechanical seal of the present invention, the temperature gradient curve S ₁ as shown in FIG.
This is because the heat transfer due to the temperature of the high-temperature fluid is blocked at the location of the heat isolation groove, as is clear from the fact that the curve rapidly falls at the location of the heat isolation groove.

Note that the present invention is not limited to the first embodiment described above. For example, as in the second embodiment shown in FIG. A heat shielding groove 40 may be formed in the inner peripheral portion of the annular retainer 8. In addition, an annular retainer 8 and a seal ring 2
A heat insulating packing 42 made of tetrafluoroethylene or the like may be interposed between the heat insulating packing 42 and the heat insulating packing 42, which can further improve the heat insulating effect. Furthermore, instead of the labyrinth groove 16, an annular retainer 8
The outer periphery may have a screw seal structure.

As explained above, according to the present invention, the high temperature fluid and the sealing liquid side are separated by reducing the gap between the inner peripheral surface of the device casing and the outer peripheral surface of the annular retainer, and at least seal The high-temperature fluid that flows into and accumulates in the annular heat-insulating groove, which is cut in the radial direction with a cutting depth that includes the axial extension area of the ring, functions as a kind of heat insulating material. The transmission of temperature to the sealed end face can be prevented as much as possible, the sealed end face can be effectively cooled by the sealing liquid, and the temperature of the sealed end face can be maintained appropriately. Therefore, it is possible to effectively seal high-temperature fluids that cannot be sealed using conventional mechanical seals.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of the entire mechanical seal showing the first embodiment of the present invention, Fig. 2 is a characteristic diagram showing the temperature gradient due to heat transfer, and Fig. 3 is a mechanical seal showing the second embodiment of the invention. It is a longitudinal cross-sectional view of the whole. 2... Rotating shaft, 4... Equipment casing, 6...
Inner peripheral surface, 8...Annular retainer, 14...High temperature fluid, 16...Labyrinth groove, 18, 40...Heat isolation groove, 20...Sealing liquid, 24...Seal ring, 2
8... Stationary sealing ring.

Claims (1)

[Claims] 1. A mechanical seal comprising a seal ring held by an annular retainer attached to a rotating shaft passing through the inside of an equipment casing, and a stationary seal ring that contacts the seal ring to form a sealed end surface. In order to separate the sealing liquid side, which is the sealed end surface side, from the high-temperature fluid side, the gap between the inner circumferential surface of the device casing and the outer circumferential surface of the annular retainer is made small, and a circulation groove is formed on the outer circumference of the annular retainer on the sealing liquid side. A mechanical seal having an annular heat-insulating groove cut in the radial direction and having a cut depth that includes at least the axially extending region of the seal ring in the high-temperature fluid side portion. .