Mechanical seal

Abstract

To suppress occurrence of local wear in a sliding part of a mechanical seal.SOLUTION: A mechanical seal 1 comprises: a rotary ring 13 integrally rotatably disposed at a rotation axis 91 side, and having a seal surface 13a; and a floating ring 35 disposed at a side of a casing 92 surrounding the rotation axis 91, and having a seal surface 353a on which the seal surface 13a of the rotary ring 13 slides. A device inside region A for sealing a sealed fluid is formed radially outward from sliding parts of both seal surfaces 13a, 353a of the rotary ring 13 and the floating ring 35. The floating ring 35 has an annular groove 354 formed along the circumferential direction in the inner periphery.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] As a shaft sealing means used under high load conditions such as a pump that supplies water to a boiler in a thermal power plant, for example, an inside-type mechanical seal as shown in Patent Document 1 is known. As shown in Fig. 4, this mechanical seal includes a stationary ring 102 and a floating ring 103 provided in a seal case 101, and a rotating ring 105 provided on a rotating shaft 104. A seal surface 103a formed on the floating ring 103 slides against a seal surface 105a formed on the rotating ring 105, thereby forming an in-machine area for sealing the sealed fluid radially outward from the sliding portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-060497 A Summary of the Invention [Problem to be solved by the invention]

[0004] A lubricating film is formed between the seal surfaces 103a, 105a of the mechanical seal by the in-machine sealed fluid penetrating from the radial outside to the radial inside. For this reason, a lubricating film is less likely to form and the temperature is more likely to be high on the radial inside than on the radial outside between the seal surfaces 103a, 105a. As a result, as shown in the enlarged view of FIG. 4, a difference in thermal expansion occurs between the radial outside and the radial inside between the seal surfaces 103a, 105a, which increases the seal surface pressure on the radial inside, which may cause local wear.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to suppress the occurrence of localized wear in the sliding portions of a mechanical seal. [Means for solving the problem]

[0006] (1) The mechanical seal disclosed herein comprises a rotating ring provided on the rotating shaft side so as to be rotatable integrally therewith and having a sealing surface, and a fixed ring provided on the casing side surrounding the rotating shaft and having a sealing surface against which the sealing surface of the rotating ring slides, wherein an in-machine area for sealing a sealed fluid is formed radially outward of the sliding portions of the sealing surfaces of the rotating ring and the fixed ring, and the fixed ring has an annular groove formed circumferentially on its inner circumference.

[0007] According to the mechanical seal of the present disclosure, the groove formed on the inner circumference of the stationary ring makes it easy for both axial ends of the stationary ring to deform so as to fall radially inward. Therefore, in the sliding portions of the seal surfaces of the rotating ring and the stationary ring, the surface pressure on the radially inner side is lower than that of a conventional stationary ring (floating ring) that does not have the groove. Therefore, the sealed fluid in the in-machine area is easy to infiltrate from the radially outer side of the sliding portion toward the radially inner side. This makes it easy for a lubricating film to be formed by the sealed fluid over the entire radial direction of the sliding portion, so that the thermal expansion difference between the radially outer side and the radially inner side can be alleviated. As a result, it is possible to suppress local wear from occurring on the radially inner side of the sliding portions of the two seal surfaces.

[0008] (2) In the mechanical seal of (1) above, it is preferable that the groove is located radially inward of a balance line which indicates the boundary between the radial range of the pressure of the sealed fluid acting on the stationary ring as a force tending to close the gap between the two seal faces and the radial range of the pressure of the sealed fluid acting on the stationary ring as a force tending to open the gap between the two seal faces. In this case, even if a groove is formed in the stationary ring, deformation of the stationary ring 48 due to stress transmitted from the other axial side of the stationary ring 48, which receives the pressure of the sealed fluid, can be suppressed, thereby suppressing a deterioration in the sealing performance of the mechanical seal.

[0009] (3) In the mechanical seal of (1) or (2) above, the groove preferably has a curved portion. In this case, the stress concentration occurring in the groove of the fixed ring can be alleviated. Effect of the Invention

[0010] According to the present disclosure, it is possible to suppress local wear from occurring in the sliding portion of the mechanical seal. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a mechanical seal according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing a floating ring of the mechanical seal and its periphery. [Diagram 3] FIG. 6 is a cross-sectional view showing a mechanical seal according to a second embodiment. [Figure 4] FIG. 1 is a cross-sectional view showing a conventional mechanical seal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. First Embodiment [Overall configuration] Fig. 1 is a cross-sectional view showing a mechanical seal 1 according to a first embodiment. In Fig. 1, the mechanical seal 1 is used under high load conditions in a rotating device 90, such as a pump that supplies water to a boiler in a thermal power plant. The rotating device 90 includes a rotating shaft 91 and a casing 92 surrounding the rotating shaft 91. The mechanical seal 1 is disposed mainly between the rotating shaft 91 and the casing 92 along the axial direction of the rotating shaft 91.

[0013] Hereinafter, in this specification, the "axial direction" refers to the direction along the axis C of the rotating shaft 91. In addition, in this specification, the "radial direction" refers to the direction perpendicular to the axis C of the rotating shaft 91, and the "circumferential direction" refers to the direction around the axis C of the rotating shaft 91. In addition, in this specification, for convenience, the left side in Fig. 1 is referred to as one axial side, and the right side in Fig. 1 is referred to as the other axial side (the same applies to Figs. 2 and 3).

[0014] The mechanical seal 1 prevents leakage of a sealed fluid (here, boiler water) in an in-machine area A of a rotating device 90 to an outside machine area B. The mechanical seal 1 of this embodiment is a so-called inside-type mechanical seal in which the in-machine area A is radially outward from a sliding portion between a rotating ring 13 and a floating ring 35 described later, and the outside machine area B is radially inward from the sliding portion. The mechanical seal 1 includes a rotating side unit 2 provided on a rotating shaft 91 so as to be rotatable integrally therewith, and a stationary side unit 3 provided in a casing 92.

[0015] [Rotating unit] The rotating side unit 2 includes a sleeve 11, a stopper ring 12, a rotating annulus 13, and a pumping ring 14. The sleeve 11 includes a cylindrical sleeve main body 11a fitted and fixed to the outer periphery of the rotating shaft 91, a disk-shaped sleeve plate portion 11b extending radially outward from the other axial end portion of the sleeve main body 11a, and a cylindrical sleeve tube portion 11c extending axially from the radial outer end of the sleeve plate portion 11b to one side.

[0016] A stopper ring 12 is fitted on the outer periphery of the rotating shaft 91 on one axial side of the sleeve body 11a. The other axial end of the stopper ring 12 is fitted on the outer periphery of one axial end of the sleeve body 11a, and a set screw 15 is fastened in the radial direction of the stopper ring 12 into the fitted portion. In this manner, the sleeve 11 is fixed to the rotating shaft 91. An O-ring 16 provides a seal (secondary seal) between the inner circumferential surface of the other axial end of the sleeve body 11a and the outer circumferential surface of the rotating shaft 91. A pumping ring 14 is fixed to the other axial side of the sleeve plate portion 11b and to the radial outside of the sleeve cylindrical portion 11c.

[0017] A rotating ring 13 is fitted and fixed between the sleeve body 11a and the sleeve tubular portion 11c. A seal surface 13a is formed on one axial side of the rotating ring 13. An O-ring 17 provides a seal (secondary seal) between the inner circumferential surface of the sleeve tubular portion 11c and the outer circumferential surface of the rotating ring 13. An O-ring 18 provides a seal (secondary seal) between the side surface on one axial side of the sleeve plate portion 11b and the side surface on the other axial side of the rotating ring 13.

[0018] [Stationary unit] The stationary unit 3 includes a seal case 31, a retainer 32, a stationary ring 33, an adapter ring 34, and a floating ring (fixed ring) 35. The seal case 31 is formed in an annular shape. A radially outer portion of the seal case 31 is fixed to the casing 92 by bolts or the like (not shown) in a state of abutting against a side surface on one axial direction side of the casing 92. A seal (secondary seal) is formed between the side surface on the other axial direction side of the seal case 31 and the side surface on the one axial direction side of the casing 92 by an O-ring 36. An annular groove 31a is formed on the other axial direction side of the radial interior of the seal case 31.

[0019] The retainer 32 is fixed to the seal case 31 by bolts 37 while being fitted into the annular groove 31a of the seal case 31. An O-ring 38 provides a seal (secondary seal) between the outer circumferential surface of the retainer 32 and the inner circumferential surface of the annular groove 31a. A stationary ring 33 is attached to the outer periphery on the other axial side of the retainer 32 so as to be axially movable. A pressing surface 33a is formed on the side surface on the other axial side of the stationary ring 33.

[0020] A spring 39 is provided between the retainer 32 and the stationary ring 33. The spring 39 biases the stationary ring 33 and the floating ring 35 toward the other axial direction relative to the retainer 32. An O-ring 40 provides a seal (secondary seal) between the inner peripheral surface of the stationary ring 33 and the outer peripheral surface of the retainer 32.

[0021] The adapter ring 34 is disposed on the other axial side of the seal case 31 within the casing 92. The adapter ring 34 has a cylindrical adapter body 34a and an annular protrusion 34b protruding radially outward from the other axial end of the adapter body 34a.

[0022] One axial end of the adapter body 34a is fitted into the annular groove 31a of the seal case 31 in a state where it is fixed to the outer periphery of the retainer 32 by a bolt (not shown). An annular flow passage 41 is formed between the outer periphery of the adapter body 34a and the inner periphery of the casing 92. A through hole 34c is formed radially penetrating the middle of the axial direction of the adapter body 34a, communicating the annular flow passage 41 with the in-machine area A. A plurality of through holes 34c are formed in the circumferential direction of the adapter body 34a. The outer periphery of the protrusion 34b is fitted into the inner periphery of the casing 92. A seal (secondary seal) is formed between the outer periphery of the protrusion 34b and the inner periphery of the casing 92 by an O-ring 42.

[0023] The casing 92 is formed with a supply passage 93 and a discharge passage 94 through which the flushing fluid flows. The flushing fluid is a fluid that cools the sliding portion between the seal surface 13a of the rotating ring 13 and the seal surface 353a (described later) of the floating ring 35 in the in-machine area A, and is made of, for example, the same fluid as the sealed fluid (boiler water). The flushing fluid is supplied from the supply passage 93 to the in-machine area A through the annular flow path 41 and the through hole 34c. The flushing fluid that has cooled the sliding portion in the in-machine area A is discharged to the outside through the discharge passage 94.

[0024] [Floating Ring] 2 is an enlarged cross-sectional view showing the floating ring 35 and its surroundings. In Fig. 2, the floating ring 35 is clamped and held from both axial sides between the stationary ring 33 and the rotating ring 13. The floating ring 35 has a main body portion 351, a pressing portion 352, and a sealing portion 353.

[0025] The main body 351 is formed in an annular shape. The outer peripheral surface of the main body 351 is formed in a spherical shape and is fitted and supported by the inner peripheral surface of the adapter main body 34a. A plurality of through holes 351a penetrating in the axial direction are formed at intervals in the circumferential direction in the main body 351. A drive pin 43 protruding from the stationary ring 33 to the other axial side is inserted into each through hole 351a of the main body 351. As a result, the floating ring 35 is held movably in the axial direction with respect to the stationary ring 33, while the relative rotation with respect to the stationary ring 33 is restricted.

[0026] The pressing portion 352 is an annular portion that protrudes axially from a radially inner end of a side surface on one axial side of the main body portion 351. A protruding end face of the pressing portion 352 is a pressing surface 352a that contacts a pressing surface 33a of the stationary ring 33. A biasing force of the spring 39 acts on the pressing surface 352a via the stationary ring 33. As a result, the floating ring 35 is pressed axially to the other side via the stationary ring 33 by the biasing force of the spring 39. A seal (secondary seal) is provided by an O-ring 44 between the side surface on one axial side of the main body portion 351 and the pressing surface 33a of the stationary ring 33, radially outward of the pressing portion 352.

[0027] The seal portion 353 is an annular portion that protrudes in the other axial direction from a radially inner end portion of the side surface on the other axial direction side of the main body portion 351. The protruding end face of the seal portion 353 is a seal surface 353a against which the seal surface 13a of the rotating ring 13 slides. As a result, an in-machine area A in which the sealed fluid is sealed is formed radially outward from the sliding portions of both the seal surfaces 13a, 353a of the rotating ring 13 and the floating ring 35 in the casing 92.

[0028] The floating ring 35 is formed so that both sides in the axial direction are substantially symmetrical. Specifically, the entire floating ring 35 including the pressing portion 352 and the seal portion 353 is formed substantially symmetrical in the axial direction with respect to a center line X1 extending in the radial direction. In particular, both axial side surfaces of the floating ring 35 that come into contact with the sealed fluid, i.e., the side surfaces radially outward of the pressing portion 352 and the seal portion 353 on both axial sides of the main body portion 351, are formed substantially symmetrical with respect to the center line X1.

[0029] This allows the floating ring 35 to receive the effect of the pressure of the sealed fluid in a well-balanced manner in the axial direction. In other words, the pressure that the floating ring 35 receives in the axial direction from the sealed fluid is substantially the same on both axial sides, so pressure distortion that would cause the floating ring 35 to tilt with respect to the axis C (see FIG. 1) is unlikely to occur. Therefore, even under high-load conditions with large pressure fluctuations of the sealed fluid, it is possible to prevent the seal surface 353a of the floating ring 35 from tilting with respect to the seal surface 13a of the rotating ring 13, so that good sealing performance can be exhibited.

[0030] An annular groove 354 is formed in the circumferential direction on the inner circumference of the main body 351 of the floating ring 35. As described above, since the entire floating ring 35 needs to be formed substantially symmetrically with respect to the center line X1, the groove 354 is also formed to have a symmetrical shape with respect to the center line X1. The groove 354 in this embodiment is formed, for example, in a U-shaped cross section at the axial center of the inner circumference of the main body 351, and has a curved portion 354a on the bottom side. The curved portion 354a is formed, for example, in a semicircular arc shape.

[0031] The groove 354 is located radially inward from the balance line L1 that passes through the main body 351. "Radially inward from the balance line L1" means not only radially inward from the balance line L1 but also on the balance line L1. The groove 354 in this embodiment is formed so that its bottom (the intersection with the center line X1) is located on the balance line L1.

[0032] The balance line L1 is an imaginary line extending in the axial direction, and indicates the boundary between the radial range of the pressure of the sealed fluid acting on the floating ring 35 as a force to close the gap between the seal faces 13a, 353a of the rotating ring 13 and the floating ring 35, and the radial range of the pressure of the sealed fluid acting on the floating ring 35 as a force to open the gap between the seal faces 13a, 353a. The closing force is a force that the sealed fluid exerts on the side surface of the floating ring 35 on one axial side toward the rotating ring 13 (the other axial side) directly or indirectly (through the stationary ring 33). In the floating ring 35 of this embodiment, the side surface on the other axial side radially outside the balance line L1 is subjected to the pressure of the sealed fluid, and the opening force acts on the floating ring 35.

[0033] [Effects] According to the mechanical seal 1 of the first embodiment, when the floating ring 35 is clamped and held between the stationary ring 33 and the rotating ring 13, the groove 354 formed on the inner circumference of the floating ring 35 makes it easy for both axial ends of the floating ring 35 (the pressing portion 352 and the sealing portion 353) to deform so as to fall radially inward. Therefore, in the sliding portion between the seal surfaces 13a, 353a of the rotating ring 13 and the floating ring 35, the surface pressure on the radially inner side is lower than that of a conventional floating ring that does not have the groove 354. Such a decrease in surface pressure could also be confirmed by structural analysis. Therefore, the sealed fluid in the in-machine area A is easy to infiltrate from the radially outer side of the sliding portion toward the radially inner side. This makes it easy for a lubricating film by the sealed fluid to be formed over the entire radial direction of the sliding portion, so that the thermal expansion difference between the radially outer side and the radially inner side can be alleviated. As a result, it is possible to suppress local wear from occurring on the radially inner side of the sliding portion between the seal surfaces 13a, 353a. In particular, when the mechanical seal 1 is used under high load conditions, there is a strong tendency for a lubricating film to be less likely to form on the radially inner side between both seal surfaces 13a, 353a, so application of the present disclosure becomes even more effective.

[0034] The groove 354 is located radially inward with respect to the balance line L1. This makes it possible to suppress deformation of the floating ring 35 caused by stress transmitted from the other axial side surface of the floating ring 35 that receives the pressure of the sealed fluid, thereby suppressing deterioration of the sealing performance of the mechanical seal 1. In addition, the groove 354 has a curved portion 354a on its bottom side, making it possible to reduce stress concentration occurring in the groove 354 of the floating ring 35.

[0035] <Second embodiment> Fig. 3 is a cross-sectional view showing a mechanical seal 1 according to a second embodiment. In Fig. 3, the mechanical seal 1 of this embodiment differs from the first embodiment mainly in that the stationary unit 3 does not have a floating ring. The mechanical seal 1 of this embodiment will be described below. In the mechanical seal 1 of this embodiment, the area radially outward from the sliding portion between the rotating ring 13 and a stationary ring 48 described later is an in-machine area A, and the area radially inward from the sliding portion is an out-machine area B.

[0036] [Rotating unit] The rotating unit 2 of the mechanical seal 1 includes a sleeve 11 and a rotating ring 13. The sleeve 11 includes a sleeve body 11a, a sleeve plate portion 11b, a sleeve inner cylinder portion 11d, and a sleeve outer cylinder portion 11e. The sleeve inner cylinder portion 11d and the sleeve outer cylinder portion 11e are each formed in a cylindrical shape. The sleeve inner cylinder portion 11d extends from a radial midpoint of the sleeve plate portion 11b to one axial side.

[0037] The sleeve outer cylinder portion 11e extends from the radial outer end of the sleeve plate portion 11b to one axial side radially outward of the sleeve inner cylinder portion 11d. The outer peripheral surface of the sleeve outer cylinder portion 11e is close to the inner peripheral surface of the casing 92. A communication hole 11f is formed in the sleeve outer cylinder portion 11e, penetrating in the radial direction. The communication hole 11f is disposed radially inward of the discharge passage 94 of the casing 92, and communicates with the discharge passage 94.

[0038] A rotating ring 13 is fitted between the sleeve main body 11a and the sleeve inner cylindrical portion 11d. An engagement groove 13b is formed at the other axial end of the rotating ring 13. An engagement pin 19 protruding from the sleeve plate portion 11b to one axial side is inserted into the engagement groove 13b of the rotating ring 13. This restricts the relative rotation of the rotating ring 13 with respect to the sleeve 11. An O-ring 20 provides a seal (secondary seal) between the inner peripheral surface of the sleeve inner cylindrical portion 11d and the outer peripheral surface of the rotating ring 13.

[0039] [Stationary unit] The stationary unit 3 of the mechanical seal 1 includes a seal case 31, a first retainer 46, a second retainer 47, and a stationary ring (fixed ring) 48. The first retainer 46 is fixed to the seal case 31 by bolts 49 while being fitted into the annular groove 31a of the seal case 31. An O-ring 50 provides a seal (secondary seal) between the outer circumferential surface of the first retainer 46 and the inner circumferential surface of the annular groove 31a.

[0040] A second retainer 47 is attached to the outer periphery of the other axial side of the first retainer 46 so as to be axially movable. A spring 51 is provided between the first retainer 46 and the second retainer 47. The spring 51 biases the second retainer 47 and the stationary ring 48 toward the other axial side relative to the first retainer 46. An O-ring 52 provides a seal (secondary seal) between the outer circumferential surface of the first retainer 46 and the inner circumferential surface of the second retainer 47.

[0041] A stationary ring 48 is provided on the other axial side of the second retainer 47. The stationary ring 48 has a main body portion 481 and a seal portion 483. The main body portion 481 is formed in an annular shape. The main body portion 481 is fitted into the inner circumferential surface of the second retainer 47 on the other axial side.

[0042] The biasing force of the spring 51 acts on the main body portion 481 via the second retainer 47. As a result, the stationary ring 48 is pressed to the other axial direction side via the second retainer 47 by the biasing force of the spring 51. A seal (secondary seal) is formed between the main body portion 481 and the second retainer 47 by an O-ring 53.

[0043] The seal portion 483 is an annular portion that protrudes in the other axial direction from a radially inner end portion of the side surface on the other axial direction side of the main body portion 481. The protruding end face of the seal portion 483 is a seal surface 483a against which the seal surface 13a of the rotating ring 13 slides. As a result, an in-machine area A in which the sealed fluid is sealed is formed radially outward from the sliding portions of both the seal surfaces 13a, 483a of the rotating ring 13 and the stationary ring 48 in the casing 92.

[0044] A supply passage 31b through which the flushing fluid flows is formed in the seal case 31. The flushing fluid is a fluid that cools the sliding portion between the seal surface 13a of the rotating ring 13 and the seal surface 483a of the stationary ring 48 in the in-machine area A, and is made of, for example, the same fluid as the sealed fluid (boiler water). The flushing fluid is supplied from the supply passage 31b to the in-machine area A. The flushing fluid that has cooled the sliding portion in the in-machine area A passes through the communication hole 11f of the sleeve 11 and is discharged to the outside from the discharge passage 94 of the casing 92.

[0045] An annular groove 484 is formed along the circumferential direction on the inner circumference of the main body portion 481 of the stationary ring 48. The groove 484 is formed symmetrically with respect to a center line X2 extending in the radial direction of the main body portion 481. The groove 484 in this embodiment is formed, for example, in a U-shaped cross section at the axial center of the inner circumference of the main body portion 481, and has a curved portion 484a on the bottom side. The curved portion 484a is formed, for example, in a semicircular arc shape.

[0046] The groove 484 is located radially inward with respect to the balance line L2 that passes through the main body portion 481. "Radially inward with respect to the balance line L2" means not only radially inward from the balance line L2 but also on the balance line L2. The groove 484 in this embodiment is formed so that its bottom portion (intersection with the center line X2) is located on the balance line L2.

[0047] The balance line L2 is an imaginary line extending in the axial direction, and indicates the boundary between the radial range of the pressure of the sealed fluid acting on the stationary ring 48 as a force to close the gap between the seal faces 13a, 483a of the rotating ring 13 and the stationary ring 48, and the radial range of the pressure of the sealed fluid acting on the stationary ring 48 as a force to open the gap between the seal faces 13a, 483a. The closing force is a force that the sealed fluid exerts on the side surface of the stationary ring 48 on one axial side toward the rotating ring 13 (the other axial side) directly or indirectly (through the second retainer 47). In the stationary ring 48 of this embodiment, the side surface on the other axial side radially outside the balance line L2 is subjected to the pressure of the sealed fluid, and the opening force acts on the stationary ring 48. Other configurations of this embodiment are similar to those of the first embodiment, so the same reference numerals are used and the description thereof is omitted.

[0048] [Effects] According to the mechanical seal 1 of the second embodiment, the groove 484 formed on the inner circumference of the stationary ring 48 makes it easy for both axial ends of the stationary ring 48 (one axial end of the main body 481 and the seal portion 483) to deform so as to fall radially inward. Therefore, in the sliding portion of both seal surfaces 13a, 483a of the rotating ring 13 and the stationary ring 48, the surface pressure on the radially inner side is lower than that of a conventional stationary ring having no groove 484. Such a decrease in surface pressure could also be confirmed by structural analysis. Therefore, the sealed fluid in the in-machine area A is easy to infiltrate from the radially outer side of the sliding portion toward the radially inner side. This makes it easy for a lubricating film by the sealed fluid to be formed over the entire radial direction of the sliding portion, so that the thermal expansion difference between the radially outer side and the radially inner side can be alleviated. As a result, it is possible to suppress local wear from occurring on the radially inner side of the sliding portion of both seal surfaces 13a, 483a. In particular, when the mechanical seal 1 is used under high load conditions, there is a strong tendency for a lubricating film to be less likely to form on the radially inner side between both seal surfaces 13a, 483a, so application of the present disclosure becomes more effective.

[0049] Groove 484 is located radially inward with respect to balance line L2. This makes it possible to suppress deformation of stationary ring 48 caused by stress transmitted from the other axial side surface of stationary ring 48 that receives pressure from the sealed fluid, thereby suppressing deterioration of the sealing performance of mechanical seal 1. In addition, groove 484 has curved portion 484a on its bottom side, making it possible to reduce stress concentration occurring in groove 484 of stationary ring 48.

[0050] <Other> The mechanical seal 1 of the above embodiment can be applied to rotating equipment other than pumps that supply water to boilers in thermal power plants. The grooves 354, 484 are formed in the axial center of the inner circumference of the main body 351, 481, but may be formed over the entire axial length of the inner circumference of the main body 351, 481. The grooves 354, 484 may be formed such that at least a portion of them is located radially outward from the balance lines L1, L2.

[0051] The shape of the grooves 354, 484 is not limited to the above embodiment. For example, the grooves 354, 484 may have a shape with only curved portions, such as a circular arc or elliptical cross section, or may have a shape without curved portions, such as a triangular shape.

[0052] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the scope of the claims and the meaning equivalent thereto. [Explanation of symbols]

[0053] 1 Mechanical seal 13 Rotating Ring 13a Sealing surface 35 Floating ring (fixed ring) 48 Stationary ring (fixed ring) 91 Rotational axis 92 Casing 353a Sealing surface 354 Groove 354a Curved section 483a Sealing surface 484 Groove 484a Curved section A Cabin Area L1 Balance Line L2 Balance Line

Claims

1. a rotating ring provided on the rotating shaft side so as to be integrally rotatable with the rotating shaft and having a sealing surface; a stationary ring provided on a casing side surrounding the rotary shaft and having a seal surface on which the seal surface of the rotary ring slides; A mechanical seal in which an in-machine area for sealing a sealed fluid is formed radially outward from sliding portions of both seal surfaces of the rotating ring and the stationary ring, The stationary ring has an annular groove formed along a circumferential direction on an inner circumference of the stationary ring, the mechanical seal.

2. 2. The mechanical seal according to claim 1, wherein the groove is located radially inward of a balance line which indicates a boundary between a radial range of the pressure of the sealed fluid acting on the stationary ring as a force tending to close the gap between the two seal faces and a radial range of the pressure of the sealed fluid acting on the stationary ring as a force tending to open the gap between the two seal faces.

3. The mechanical seal according to claim 1 or 2, wherein the groove has a curved portion.

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