Mechanical seal

Abstract

To provide a mechanical seal which enables a flushing fluid to be easily discharged without providing a dam member at a casing.SOLUTION: A mechanical seal 1 includes: a rotary side unit 2 integrally rotatably provided at a rotary shaft 71 and having a rotary seal ring 13; and a stationary side unit 3 provided at a casing 72 and having a stationary seal ring 35 on which the rotary seal ring 13 slides on so as to seal a sealed fluid in a device internal area 73. The rotary side unit 2 has a pumping ring 21 which has a ring outer peripheral surface 23a facing a discharge port 72b1 of the casing 72 and causes a flushing fluid in the device internal area 73 to flow along the ring outer peripheral surface 23a in a rotation direction of the rotary shaft 71. The stationary side unit 3 includes a dam part 51 which is disposed at the radial outer side relative to the ring outer peripheral surface 23a and changes flow of the flushing fluid flowing along the ring outer peripheral surface 23a in the rotation direction to flow flowing to the radial outer side toward the discharge port 72b1.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a mechanical seal.

Background Art

[0002] As shaft sealing means used under high-pressure and high-temperature conditions, such as a pump for supplying water to a boiler in a thermal power plant, a mechanical seal shown in Patent Document 1, for example, is known. As shown in FIG. 5, such a mechanical seal includes a stationary seal ring 102 provided on the casing 101 side, a rotating seal ring 104 provided on the rotating shaft 103 side and sliding against the stationary seal ring 102, and a pumping ring 105 that rotates together with the rotating shaft 103. The casing 101 has a supply passage 106 for supplying a flushing fluid to the in-machine area, a discharge passage 107 for discharging the flushing fluid in the in-machine area to the outside, an annular passage 108 formed in an annular shape at the radially inner end of the discharge passage 107, and a weir member 109 provided in the annular passage 108.

[0003] As shown in FIG. 6 (a cross-sectional view taken along the line A-A of FIG. 5), the weir member 109 is disposed in the annular passage 108 at a position slightly shifted downstream in the rotation direction of the rotating shaft 103 (pumping ring 105) from the discharge passage 107. For the sake of convenience, the weir member 109 is shown by cross-hatching in FIG. 6. The flushing fluid supplied from the supply passage 106 to the in-machine area flows near the sliding portion between the stationary seal ring 102 and the rotating seal ring 104, and then is guided to the annular passage 108 by the pumping ring 105 (see FIG. 5). The flushing fluid guided to the annular passage 108 flows in the rotation direction of the rotating shaft 103. The flow of the flushing fluid in the rotation direction is changed by the weir member 109 to a radially outward flow toward the discharge passage 107 (see FIG. 6).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Depending on the casing 101, it may not be possible to provide a weir member 109 in the annular passage 108. In this case, even if the pumping ring 105 guides the flushing fluid into the annular passage 108, the flushing fluid in the annular passage 108 will have difficulty flowing into the discharge passage 107. As a result, the flow rate of the flushing fluid supplied from the supply passage 106 to the machine interior will be insufficient, and the sliding surface between the stationary sealing ring 102 and the rotating sealing ring 104 will experience dry sliding. Dry sliding can accelerate wear on the sliding surface or cause the sliding surface to become rough, reducing sealing performance and potentially drastically shortening the lifespan of the mechanical seal.

[0006] This disclosure has been made in view of these circumstances and aims to provide a mechanical seal that can easily discharge flushing fluid without providing a weir member in the casing. [Means for solving the problem]

[0007] (1) The mechanical seal of the present disclosure comprises a rotating side unit that is integrally rotatable on a rotating shaft and has a rotating sealing ring, and a stationary side unit that is provided on a casing surrounding the rotating shaft and has a stationary sealing ring on which the rotating sealing ring slides to seal a fluid to be sealed in an internal region within the casing, wherein the rotating side unit has a ring outer surface facing a discharge port formed on the inner circumference side of the casing and includes a pumping ring that causes the flushing fluid supplied to the internal region to flow along the ring outer surface in the rotational direction of the rotating shaft, and the stationary side unit is arranged radially outward from the ring outer surface and includes a weir that changes the flow of the flushing fluid flowing along the ring outer surface in the rotational direction to a radially outward flow toward the discharge port.

[0008] According to the mechanical seal described above, as the pumping ring rotates with the rotating shaft, the flushing fluid supplied to the machine area flows along the outer surface of the ring in the direction of rotation of the rotating shaft. This rotational flow of the flushing fluid is changed by the weir of the stationary unit to a radially outward flow toward the outlet. As a result, the flushing fluid flowing along the outer surface of the ring is made more likely to flow toward the outlet by the weir. Therefore, even without providing a weir member in the casing, the flushing fluid can be easily discharged from the outlet by the weir of the stationary unit.

[0009] (2) The stationary unit is preferably provided with an adapter ring that supports the outer circumferential surface of the stationary sealing ring, and the weir portion is preferably a part of the adapter ring. In this case, there is no need to separately provide a weir section on the stationary unit, so the configuration of the stationary unit can be simplified.

[0010] (3) The end face on the upstream side in the rotational direction of the weir is preferably a tapered surface that slopes toward the rotational direction as it extends radially outward. In this case, the tapered end face on the upstream side in the rotational direction of the weir allows the flow of the flushing fluid in the rotational direction to be smoothly changed to a radially outward flow. As a result, the flushing fluid flowing along the outer surface of the ring flows more easily towards the outlet. [Effects of the Invention]

[0011] According to this disclosure, the flushing fluid can be easily discharged without providing a weir member in the casing. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of a mechanical seal according to an embodiment of the present disclosure. [Figure 2] This is a magnified cross-sectional view showing the pumping ring and its surrounding area. [Figure 3]This is a cross-sectional view taken along arrow II in Figure 2. [Figure 4] This is a cross-sectional view showing a modified example of the weir section. [Figure 5] This is a cross-sectional view of a conventional mechanical seal. [Figure 6] This is a cross-sectional view taken along the line AA in Figure 5. [Modes for carrying out the invention]

[0013] Next, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. [Overall structure] Figure 1 is a cross-sectional view of a mechanical seal according to an embodiment of the present disclosure. In Figure 1, the mechanical seal 1 is used, for example, in a pump that supplies water to a boiler in a thermal power plant, and seals the boiler water as a sealed fluid inside the pump. The mechanical seal 1 is positioned between the rotating shaft 71 of the pump and the casing 72 surrounding the rotating shaft 71, along the axial direction of the rotating shaft 71 (hereinafter simply referred to as "axial direction").

[0014] The mechanical seal 1 of this embodiment comprises a rotating-side unit 2 that is integrally rotatable on the rotating shaft 71, and a stationary-side unit 3 provided on the casing 72. For convenience, in this specification, the right side of Figure 1 is referred to as the axial side, and the left side of Figure 1 is referred to as the other axial side (the same applies to Figures 2 and 3).

[0015] [Rotating side unit] The rotating unit 2 comprises a sleeve 11, a stopper ring 12, a rotating sealing ring 13, a reinforcing ring 14, and a pumping ring 21. The sleeve 11 has a cylindrical sleeve body 11a fitted and fixed to the outer circumference of the rotating shaft 71, a disc-shaped sleeve plate portion 11b extending radially outward from the other axial end of the sleeve body 11a, and a cylindrical sleeve tube portion 11c extending axially to one side from the radial outer end of the sleeve plate portion 11b.

[0016] On the inner circumference of one axial end of the sleeve body 11a, a key groove 11d is formed at a predetermined position in the circumferential direction. A key member 15 is inserted between the key groove 11d and the outer peripheral surface of the rotating shaft 71. A stopper ring 12 is fitted onto the outer circumference of the rotating shaft 71 on one axial side of the sleeve body 11a so that the key member 15 does not slip out in the axial one side direction.

[0017] The other axial end of the stopper ring 12 is fitted onto the outer circumference of one axial end of the sleeve body 11a, and a set screw 16 is tightened in the radial direction of the stopper ring 12 at the fitting portion. Thus, the sleeve 11 is fixed to the rotating shaft 71. The space between the inner circumferential surface of the other axial end of the sleeve body 11a and the outer peripheral surface of the rotating shaft 71 is sealed (secondary seal) by an O-ring 17. A pumping ring 21 is disposed on the other axial side of the sleeve plate portion 11b and on the outer side in the radial direction of the sleeve cylinder portion 11c. Details of the pumping ring 21 will be described later.

[0018] A rotating seal ring 13 is disposed between the sleeve body 11a and the sleeve cylinder portion 11c. A seal surface 13a is formed on one axial end face of the rotating seal ring 13. A reinforcing ring 14 is fitted and fixed to the outer peripheral surface of the rotating seal ring 13. The reinforcing ring 14 is connected to the sleeve cylinder portion 11c by a pin 19 while being inserted into the inner peripheral side of the sleeve cylinder portion 11c. The space between the inner circumferential surface of the sleeve cylinder portion 11c and the outer peripheral surface of the rotating seal ring 13 is sealed (secondary seal) by an O-ring 20. The space between one axial side surface of the sleeve plate portion 11b and the other axial end face of the rotating seal ring 13 is sealed (secondary seal) by an O-ring 24.

[0019] [Stationary side unit] The stationary unit 3 includes a seal case 31, a retainer 32, a holding ring 33, an adapting 34, and a stationary seal ring 35. The seal case 31 is formed in an annular shape. The radially outer portion of the seal case 31 is fixed to the casing 72 by bolts (not shown) while being in contact with the axial one-side surface of the casing 72. Between the axial other-side surface of the seal case 31 and the axial one-side surface of the casing 72, it is sealed (secondary seal) by an O-ring 37. An annular groove 31a is formed on the axial other side of the radially inner portion of the seal case 31.

[0020] The retainer 32 is fixed to the seal case 31 by bolts 38 while being fitted into the annular groove 31a of the seal case 31. Between the outer peripheral surface of the retainer 32 and the inner peripheral surface of the annular groove 31a, it is sealed (secondary seal) by an O-ring 39. The holding ring 33 is attached to the outer periphery of the axial other side of the retainer 32 so as to be axially movable. A pressing surface 33a is formed on the axial other-side end surface of the holding ring 33.

[0021] A spring 40 is provided between the retainer 32 and the holding ring 33. The spring 40 biases the holding ring 33 axially to the other side with respect to the retainer 32. Between the inner peripheral surface of the holding ring 33 and the outer peripheral surface of the retainer 32, it is sealed (secondary seal) by an O-ring 41.

[0022] The adapting 34 is disposed on the axial other side of the seal case 31 within the casing 72. The adapting 34 has a cylindrical adapter body 34a, an annular protruding portion 34b protruding radially outward from the axial other end portion of the adapter body 34a, and a weir portion 51 integrally formed on the protruding portion 34b.

[0023] One axial end of the adapter body 34a is fixed to the outer circumference of the retainer 32 by a bolt 36 and fitted into the annular groove 31a of the seal case 31. A through hole 34c is formed in the middle of the adapter body 34a in the axial direction, penetrating radially. Multiple through holes 34c are formed in the circumferential direction of the adapter body 34a. The outer circumferential surface of the projection 34b is fitted to the inner circumferential surface of the casing 72. The space between the outer circumferential surface of the projection 34b and the inner circumferential surface of the casing 72 is sealed (secondary seal) by an O-ring 42. Details of the weir 51 will be described later.

[0024] The stationary sealing ring 35 is held between the retaining ring 33 and the rotating sealing ring 13. The outer circumferential surface of the stationary sealing ring 35 is formed in a spherical shape and is fitted and supported on the inner circumferential surface of the adapter body 34a. On one axial side of the stationary sealing ring 35, a pressing surface 35a is formed that contacts the pressing surface 33a of the retaining ring 33. As a result, the stationary sealing ring 35 is pressed axially to the other side via the retaining ring 33 by the biasing force of the spring 40. The space between the radially outer side of the stationary sealing ring 35a and the pressing surface 33a of the retaining ring 33 is sealed (secondary seal) by the O-ring 43.

[0025] On the other axial side of the stationary sealing ring 35, a sealing surface 35b is formed on which the sealing surface 13a of the rotating sealing ring 13 slides. As a result, an internal region 73 in which the fluid to be sealed is sealed is formed radially outward from both the sealing surfaces 13a and 35b of the rotating sealing ring 13 and the stationary sealing ring 35 within the casing 72. A communication hole 35c is formed in the stationary sealing ring 35, penetrating in the axial direction.

[0026] [Flow path of flushing fluid] The casing 72 has a flow path for flushing fluid that cools and lubricates the sliding portion (sealing surfaces 13a, 35b) between the rotating sealing ring 13 and the stationary sealing ring 35. Hereinafter, the sliding portion between the rotating sealing ring 13 and the stationary sealing ring 35 will also be referred to as the sliding portion 13a, 35b. The flushing fluid in this embodiment is the same fluid (boiler water) as the sealed fluid. The casing 72 has a supply passage 72a, a discharge passage 72b, and an annular passage 72c formed as the flow path.

[0027] The supply passage 72a is a passage that supplies flushing fluid from outside the casing 72 to the internal region 73. The supply passage 72a extends radially within the casing 72 and has a supply port 72a1 that opens on the inner circumferential surface of the casing 72. The supply port 72a1 is located radially outward from the adapter body 34a.

[0028] The discharge passage 72b is a passage for discharging the flushing fluid supplied from the supply passage 72a to the machine interior region 73 to the outside of the casing 72. The discharge passage 72b extends radially on the opposite axial side of the supply passage 72a of the casing 72 and has an outlet 72b1 formed on the inner circumference side of the casing 72.

[0029] The annular passage 72c is a flow path connecting the internal region 73 and the discharge passage 72b. The annular passage 72c is formed in an annular shape in the circumferential direction of the casing 72, radially inward from the discharge passage 72b of the casing 72 (see Figure 3). In this embodiment, the annular passage 72c consists of a groove that opens on the inner circumferential surface of the casing 72. The discharge port 72b1 of the discharge passage 72b opens on the bottom surface (outer circumferential surface) of the annular passage 72c.

[0030] With the above configuration, the flushing fluid supplied from the supply passage 72a to the internal area 73 passes through the through hole 34c of the adapter body 34a and the communication hole 35c of the stationary sealing ring 35, cooling and lubricating the sliding parts 13a and 35b. After that, the flushing fluid flows from the outer circumference of the pumping ring 21 into the annular passage 72c and is then discharged to the outside of the casing 72 through the discharge passage 72b.

[0031] [Pumping ring] Figure 2 is an enlarged cross-sectional view showing the pumping ring 21 and its surroundings. The pumping ring 21 guides the flushing fluid supplied to the machine interior region 73 to the vicinity of the discharge port 72b1 of the discharge passage 72b. The pumping ring 21 in this embodiment has a disc-shaped pumping plate portion 22 and a cylindrical pumping cylinder portion 23.

[0032] The pumping plate portion 22 is positioned along the other axial side of the sleeve plate portion 11b. The pumping plate portion 22 is fixed to the sleeve plate portion 11b by bolts 18. This allows the pumping ring 21 to rotate together with the rotation axis 71. Annular recesses 22a and annular protrusions 22b are formed alternately and continuously along the entire axial direction on the outer circumference of the pumping plate portion 22. The outer diameter of the annular protrusions 22b is slightly smaller than the diameter of the inner surface of the casing 72 facing the pumping plate portion 22. This creates an annular labyrinth gap S between the outer circumference of the pumping plate portion 22 and the inner surface of the casing 72.

[0033] The labyrinth gap S prevents the flushing fluid from flowing axially to the other side of the pumping ring 21. As a result, the area around the sliding parts 13a and 35b can be maintained in an atmosphere of flushing fluid. Furthermore, the labyrinth gap S also prevents the sealed fluid on the other axial side of the pumping ring 21 from flowing axially to the one side of the pumping ring 21.

[0034] The pumping cylinder portion 23 extends from the outer circumference of the pumping plate portion 22 along the outer circumference of the sleeve cylinder portion 11c in one axial direction. The outer circumference 23a of the pumping cylinder portion 23 (hereinafter also referred to as the ring outer circumference 23a) is spaced radially inward from the annular passage 72c. As a result, the ring outer circumference 23a of the pumping cylinder portion 23 is positioned opposite the discharge port 72b1 via the annular passage 72c. The ring outer circumference 23a has a guide surface 23b that slopes radially inward from its axial middle towards one end in the axial direction. Multiple guide surfaces 23b are formed at intervals in the circumferential direction of the ring outer circumference 23a.

[0035] With the above configuration, as the pumping ring 21 rotates together with the rotating shaft 71, the flushing fluid in the internal region 73 is guided from one axial side of the pumping cylinder 23 along each guide surface 23b to the outer ring surface 23a. The flushing fluid guided to the outer ring surface 23a then flows along the outer ring surface 23a in the direction of rotation of the rotating shaft 71 (pumping ring 21) (hereinafter also simply referred to as the direction of rotation).

[0036] [Weir] Figure 3 is a cross-sectional view taken along arrow II in Figure 2. For convenience, the weir portion 51 is shown with cross-hatching in Figure 3 (the same applies to Figure 4). As shown in Figures 2 and 3, the weir portion 51 is a strip-shaped member that extends from one point in the circumferential direction at the other axial end of the projection portion 34b of the adapter ring 34 toward the other axial side. The weir portion 51 is located radially outward from the outer circumferential surface 23a of the ring. In this embodiment, the weir portion 51 is located between the outer circumferential surface 23a of the ring and the annular passage 72c, and extends from one axial side of the outlet 72b1 to the other axial side of the outlet 72b1.

[0037] As shown in Figure 3, the weir 51 is positioned between the outer ring surface 23a and the annular passage 72c, slightly downstream of the outlet 72b1 in the rotational direction (clockwise in Figure 3). In the cross-sectional view of Figure 3, the upstream end face 51a of the weir 51 in the rotational direction is located radially inward of the downstream end of the outlet 72b1 in the rotational direction. The end face 51a of the weir 51 in this embodiment extends straight in the radial direction.

[0038] With the above configuration, the flow of flushing fluid that flows in the rotational direction along the outer circumferential surface 23a of the pumping ring 21 is changed by the end face 51a of the weir 51 to flow radially outward toward the outlet 72b1. As a result, the flushing fluid can easily flow from the end face 51a of the weir 51 through the annular passage 72c to the outlet 72b1.

[0039] [Effects of this embodiment] According to the mechanical seal 1 of this embodiment, as the pumping ring 21 rotates together with the rotating shaft 71, the flushing fluid supplied from the supply passage 72a to the internal region 73 flows along the outer circumferential surface 23a of the ring in the direction of rotation of the rotating shaft 71. This rotational flow of the flushing fluid is changed by the weir portion 51 of the stationary unit 3 to flow radially outward toward the outlet 72b1 of the discharge passage 72b. As a result, the flushing fluid flowing along the outer circumferential surface 23a of the ring is made more likely to flow toward the outlet 72b1 by the weir portion 51. Therefore, even without providing a weir member in the casing 72, the flushing fluid can be easily discharged from the outlet 72b1 by the weir portion 51 of the stationary unit 3.

[0040] Furthermore, since the weir section 51 is part of the adapter ring 34 that supports the outer circumferential surface of the stationary sealing ring 35, there is no need to separately provide the weir section 51 on the stationary unit 3. This simplifies the configuration of the stationary unit 3.

[0041] [Differentiation of the weir section] Figure 4 is a cross-sectional view showing a modified example of the weir 51. In this modified example of the weir 51, the shape of the upstream end face 51a in the rotational direction differs from that of the above embodiment. In this modified example, the end face 51a of the weir 51 has a tapered surface 51b that slopes toward the rotational direction as it extends from the radially inner side to the radially outer side. In this modified example, the tapered surface 51b is formed over the entire end face 51a, that is, from the radially inner end to the radially outer end of the end face 51a. Furthermore, in this modified example, the tapered surface 51b is positioned opposite the discharge port 72b1 via the annular passage 72c. Note that the tapered surface 51b may be formed on a part of the end face 51a.

[0042] According to this modified example, the tapered surface 51b of the upstream end face 51a in the rotational direction of the weir 51 allows the flow of the flushing fluid in the rotational direction to be smoothly changed to a radially outward flow. As a result, the flushing fluid flowing along the outer circumferential surface 23a of the ring flows more easily to the outlet 72b1.

[0043] [others] In this embodiment, the weir portion 51 is part of the adapter ring 34, but it may be provided separately from the adapter ring 34, or it may be provided on other members of the stationary unit 3.

[0044] The mechanical seal 1 of the above embodiment can also be applied to rotating equipment other than pumps that supply water to boilers in thermal power plants. Furthermore, although the mechanical seal 1 of the above embodiment uses the fluid to be sealed as the flushing fluid, other fluids may be used. In that case, any fluid that does not cause problems when mixed with the fluid to be sealed should be used.

[0045] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims, not in the sense described above, and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of Symbols]

[0046] 1 Mechanical seal 2 Rotating Unit 3 Stationary Unit 13 Rotating sealing ring 21 Pumping Ring 23a Outer surface (outer surface of the ring) 34 Adapter Rings 35 Stationary sealing ring 51 Weir 51a End face 51b Tapered surface 71 Rotation axis 72 Casing 72b1 Outlet 73 In-flight area

Claims

1. A rotating side unit is provided on the rotating shaft so as to be rotatable integrally with it and has a rotating sealing ring, A stationary unit is provided in a casing surrounding the rotating shaft, and has a stationary sealing ring on which the rotating sealing ring slides to seal the fluid to be sealed in the internal region of the casing, The rotating unit has a ring outer surface facing a discharge port formed on the inner circumference of the casing, and includes a pumping ring that flows the flushing fluid supplied to the internal region of the machine along the ring outer surface in the direction of rotation of the rotating shaft. The stationary unit is provided on a component of the stationary unit and is positioned radially outward from the outer surface of the ring, and includes a weir that changes the flow of flushing fluid flowing in the rotational direction along the outer surface of the ring to a radially outward flow toward the outlet, in a mechanical seal.

2. The stationary unit comprises an adapter ring having an outer surface that fits into the inner surface of the casing and an inner surface that supports the outer surface of the stationary sealing ring. The mechanical seal according to claim 1, wherein the weir portion is part of the adapter ring.

3. The mechanical seal according to claim 1 or 2, wherein the upstream end face in the rotational direction of the weir portion has a tapered surface that inclins toward the rotational direction as it extends radially outward.

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