JP2007162655A - Sealing device of fluid machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize a leakage in a sealing device preventing a fluid from leaking through the clearance between the rotary body and the casing of a fluid machine from the high-pressure side to the low-pressure side. <P>SOLUTION: This sealing device 25B comprises a wear ring 31 and a floating ring 32. The clearance between the peripheral wall of a through hole 32a formed in the floating ring 32 and the outer peripheral surface of the mouth ring part 19 of an impeller 19 is narrower than the clearance 35 between the inner peripheral wall of a through hole 31a in the wear ring 31 and the outer peripheral surface of the mouth ring part 19. The machining to increase the surface roughness such as knurling is applied to the through hole 31a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sealing device that prevents fluid from leaking from a high pressure region to a low pressure region in a casing through a gap between the casing and a rotating body in a fluid machine such as a pump, a water wheel, a compressor, and a gas turbine. .

  As a seal device between a rotating body such as a main shaft or an impeller of a fluid machine and a casing, for example, a device using a wear ring as described in Patent Document 1 is known. A gap is formed between the inner peripheral surface of the wear ring fixed to the casing side and the outer peripheral surface of the rotating body. By setting this gap as small as possible, fluid can flow from the high pressure side through the gap. Prevents leakage to the low pressure side.

  However, this type of conventional sealing device has the following problems.

  First, if the gap between the inner peripheral surface of the wear ring and the rotating body is set too narrow in order to reduce fluid leakage, dimensional errors and assembly accuracy that are unavoidable even if the wear ring and the rotating body are processed with high accuracy. Due to the error, the wear ring and the rotating body may not be assembled. Therefore, it is necessary to set the size of the gap to a certain degree in consideration of assembly, and there is a limit in reducing the amount of fluid leakage.

  Further, when the rotating body and the wear ring come into contact with each other during the operation of the fluid machine, vibration is generated, and the rotating body and the wear ring may be galled or burned. In the sealing device described in Patent Document 1 described above, a lining made of an organic material is provided on the wear ring to prevent seizure. However, since the lining wears due to the contact between the rotating body and the wear ring, when the fluid machine is operated for a long period of time, the metal material covered with the lining is exposed, and as a result, baking may occur.

  Furthermore, the velocity of the fluid flowing from the high pressure side through the gap between the wear ring and the rotating body to the low pressure side has a high flow rate corresponding to the pressure difference between the high pressure side and the low pressure side. Wear of the wear ring is caused by the fluid having a high flow rate passing through the gap. Further, since the flow velocity is particularly high near the outlet of the gap on the low-pressure side, a rapid pressure drop occurs, and cavitation that causes vibration and wear may occur.

Japanese Utility Model Publication No. 6-018649

  The present invention relates to a seal device that prevents fluid from leaking from a high pressure region to a low pressure region in a casing through a gap between a casing and a rotating body of a fluid machine. It is an object to minimize leakage, reduce vibration, prevent seizure, suppress wear, suppress cavitation, and the like while realizing ease.

  The present invention provides a sealing device that prevents fluid from leaking from a high-pressure region in the casing to a low-pressure region through a gap between a casing and a rotating body of a fluid machine. A main through hole into which the rotating body is inserted through the side and the low pressure region side, and a first gap is formed between a peripheral wall of the main through hole and an outer peripheral surface of the rotating body. A main ring having an integral structure, and an annular housing groove formed on the peripheral wall of the main through hole of the main ring on the high pressure region side, and the high pressure region side and the low pressure region side are An auxiliary through hole having a diameter smaller than the diameter of the main through hole through which the rotating body is inserted is formed, and the first through hole is formed between a peripheral wall of the auxiliary through hole and the outer peripheral surface of the rotating body. 2nd narrower than 1 gap During it is formed, and a thin auxiliary ring of integral structure, to provide a seal device of the fluid machine.

  Since the thin auxiliary ring is provided separately from the main ring, the diameter of the auxiliary through hole formed in the thin auxiliary ring is made significantly smaller than the diameter of the main through hole formed in the main ring, and the second gap is formed. It can be significantly narrower than the first gap. As a result, the amount of fluid leaking from the high pressure region to the low pressure region through the first and second gaps can be minimized. By minimizing the amount of leakage, leakage loss can be reduced and the efficiency of the fluid machine can be improved.

  A thin auxiliary ring is provided separately from the main ring, and is formed in the thin auxiliary ring rather than a gap (first gap) between the peripheral wall of the main through hole formed in the main ring and the outer peripheral surface of the rotating body. A gap (second gap) between the peripheral wall of the auxiliary through hole and the outer peripheral surface of the rotating body is set narrow. As a result, the rotating body and the main ring (hole peripheral wall of the main through hole) do not come into contact with each other, so that vibrations caused by the rotating body colliding with the main ring can be prevented, and the rotating body and the main ring can be prevented from being galled or seized. it can.

  The first gap on the main ring side is on the low pressure region side than the second gap on the thin auxiliary ring side, and the first gap is wider than the second gap. Therefore, since the flow velocity of the fluid flowing through the first gap from the high pressure region side toward the low pressure region side is reduced, the main ring can be prevented from being worn (the wear of the peripheral wall of the main through hole). In addition, since the flow velocity of the fluid in the vicinity of the outlet on the low pressure region side of the first gap is reduced, a sudden pressure drop does not occur in this portion, and the occurrence of cavitation can be prevented.

  Both the main ring and the thin auxiliary ring are not a structure in which multiple parts are assembled, but a single structure consisting of a single part. The main ring is bent by fitting the thin auxiliary ring into the annular receiving groove of the main ring. A thin auxiliary ring can be attached to the. Therefore, the sealing device of the present invention is easy to manufacture. If necessary, the thin auxiliary ring can be removed from the main ring simply by bending it out of the main ring annular receiving groove, and the replacement thin auxiliary ring can also be bent into the annular receiving groove. Can be attached to the main ring. In this respect, the sealing device of the present invention can be easily maintained.

  The sum of the dimension of the second gap and the dimension of the third gap formed between the bottom wall of the annular housing groove and the outer periphery of the thin auxiliary ring is smaller than the first gap. Is preferred.

  The thin auxiliary ring can move in the annular housing groove in a direction (radial direction) perpendicular to the axis of the rotating member by a distance corresponding to the dimension of the third gap at the maximum. Even if the rotating body contacts or collides with the thin auxiliary ring, this movement can reduce damage and wear of the thin auxiliary ring. On the other hand, even if the thin auxiliary ring pushed by the rotating body moves in the direction perpendicular to the rotating direction of the rotating member, the thin plate assists before the rotating body collides with the main ring (the peripheral wall of the main ring through hole). The outer periphery of the ring contacts the bottom wall of the annular receiving groove. Therefore, generation of vibration due to collision between the rotating body and the main ring and seizure of the rotating body and the main ring can be reliably prevented.

  It is preferable that a distance between a pair of opposite side walls of the annular housing groove is larger than a thickness of the thin auxiliary ring.

  The thin auxiliary ring is accommodated in the annular accommodating groove so as to be movable in the axial direction of the rotating body by a distance corresponding to the difference between the distance between the side walls of the annular accommodating groove and the thickness of the thin auxiliary ring. The thin auxiliary ring is pressed against the main ring with a force corresponding to a differential pressure between the pressure acting on the surface on the high pressure region side and the pressure acting on the surface on the low pressure region side (main through hole side). Therefore, when the rotating body contacts or collides with the thin auxiliary ring, a frictional force proportional to the pressing force is generated between the thin auxiliary ring and the main ring, and this frictional force is a resistance against the radial movement of the thin auxiliary ring. Become. As a result, the auxiliary ring functions as a damping frictional force against the vibration of the rotating body, and reduces the vibration of the rotating body.

  It is preferable that an enlarged-diameter portion is formed in a portion of the main ring through hole facing the low pressure side of the thin auxiliary ring. By changing the size and shape of the enlarged diameter portion, the force for pressing the thin auxiliary ring against the main ring can be adjusted. Therefore, the damping frictional force against the vibration of the rotating body can be adjusted by adjusting the size and shape of the enlarged diameter portion.

  It is preferable that the hole peripheral wall of the main through hole is processed to increase the surface roughness. Since the fluid frictional resistance in the first gap, which is the gap between the hole peripheral wall of the main through hole and the outer peripheral surface of the rotating body, increases, the fluid leaks from the high pressure region to the low pressure region through the first and second gaps. The amount of leakage of the fluid machine can be further reduced, the leakage loss can be further reduced, and the efficiency of the fluid machine can be further improved. Examples of this type of processing include knurling, but are not particularly limited as long as the processing can sufficiently increase the fluid frictional resistance.

  The sealing device for a fluid machine of the present invention has a relatively simple structure and is easy to manufacture and maintain, while minimizing leakage, reducing vibration, preventing seizure, suppressing wear, suppressing cavitation, and the like. Can do.

  FIG. 1 shows a two-stage centrifugal pump 1 having a sealing device according to an embodiment of the present invention. In the casing 2 of the centrifugal pump 1, two spiral chambers 4A and 4B partitioned by an inter bush 3 are formed. In the spiral chambers 4A and 4B, the first stage impeller 5A and the second stage impeller 5B are arranged in a symmetrical manner. These impellers 5A and 5B are fixed to a main shaft 6 extending in the horizontal direction. The main shaft 6 extends through the casing 2. A pair of bearing brackets 7A and 7B are fixed to the casing 2, and both ends of the main shaft 6 are rotatably supported by bearings 8A and 8B accommodated in these bearing brackets 7A and 7B. Further, sealing gland packings 9 </ b> A and 9 </ b> B are disposed at portions where the main shaft 6 penetrates the casing 2. The right end of the main shaft 6 is connected to a prime mover (not shown).

  When the main shaft 6 is rotated by the prime mover, the impellers 5A and 5B are rotated in the spiral chambers 4A and 4B. The water flowing into the spiral chamber 4A from the suction port 11 is pressurized by the first stage impeller 5A and then flows into the spiral chamber 4B through the flow path 12 schematically shown. The water flowing into the spiral chamber 4B is further pressurized by the second stage impeller 5B and then discharged from the discharge port 13.

  The impellers 5 </ b> A and 5 </ b> B include a boss portion 15 fixed to the main shaft 6 and a circular main plate 16 extending from the boss portion 15 in the radial direction of the main shaft 6. To the main plate 16, the base end sides of the plurality of blades 17 are fixed. Further, the tip ends of these blades 17 are connected by a side plate 18. The side plate 18 has a circular outer periphery, and is provided with a mouth ring portion 19 that protrudes in the direction away from the main plate 16 in a cylindrical shape with openings at both ends. An opening surrounded by the mouth ring portion 19 constitutes an impeller inlet 21. Further, the portion sandwiched between the outer periphery of the main plate 16 and the side plate 18 constitutes the impeller outlet 22. The main plate 16 and the side plate 18 are arranged coaxially with the main shaft 6. Therefore, the axis L of the main shaft 6 is also the rotation center of the main plate 16 and the side plate 18. Water in the spiral chambers 4A, 4B is sucked into the impellers 5A, 5B rotating from the impeller inlet 21, pressurized by the vanes 17, and discharged from the impeller outlet 22. Accordingly, in the spiral chambers 4A and 4B, the impeller inlet 21 side is the low pressure region 4a and the impeller outlet 22 side is the high pressure region 4b.

  The sealing devices 25A and 25B prevent water in the spiral chambers 4A and 4B from leaking from the high pressure region 4b to the low pressure region 4a. Specifically, in the sealing devices 25A and 25B, water in the high pressure region 4b in the spiral chambers 4A and 4B leaks into the low pressure region 4a through the gap between the casing 2 and the outer peripheral surface of the mouth ring portion 19 of the impeller 5. To prevent it. The sealing device 25A disposed in the first-stage spiral chamber 4A and the sealing device 25B disposed in the second-stage spiral chamber 4B have the same structure and function, and in the drawing, only the mounting orientation in the left-right direction is shown. Different. Hereinafter, the sealing device 25B disposed in the second-stage spiral chamber 4B will be described in detail.

  With further reference to FIGS. 2, 3, and 5, the seal device 25 </ b> B has a wear ring (main ring) 31 whose outer periphery is fixed to the casing 2 with screws, and an axis of the main shaft 6 with respect to the wear ring 31. And a floating ring (thin auxiliary ring) 32 that is attached so as to be movable to some extent in the direction orthogonal to L and the direction in which the axis L extends. The wear ring 31 is made of, for example, stainless steel, cast iron, bronze casting, or the like, and is not a structure in which a large number of parts are assembled, but a single structure made of a single part. On the other hand, the floating ring 32 is made of a material that is excellent in sliding performance and wear resistance and has some degree of elastic deformation. For example, various synthetic resins such as fluororesin such as tetrafluoroethylene (PTFE) and polyamide resin such as polyester ether ketone (PEEK), hard rubber, light metal, leather, etc. can be used as the material of the floating ring 32. Like the wear ring 31, the floating ring 32 is not a structure in which a large number of parts are assembled, but a single structure composed of a single part.

  The wear ring 31 has a thin annular shape as a whole, and has a circular through-hole (main through-hole) penetrating from an end surface on the low pressure region 4a side (left end surface in the drawing) to an end surface on the high pressure region 4b side (right end surface in the drawing). Hole) 31a is formed. The mouth ring portion 19 of the impeller 5B is inserted into the through hole 31a from the high pressure region 4b side. In addition, an annular housing groove 31b is formed in the hole peripheral wall of the through hole 31a on the high pressure region 4b side, specifically, in the hole peripheral wall of the through hole 31a near the end surface on the high pressure region 4b side of the wear ring 31. The floating ring 32 is accommodated in the annular accommodating groove 31b. The portion of the through hole 31a facing the end surface of the floating ring 32 on the low pressure region 4a side, that is, the connection portion between the peripheral wall of the through hole 31a and the side wall on the low pressure region 4b side of the pair of side walls of the annular housing groove 31b A chamfered portion 31c whose diameter gradually increases from the region 4a side toward the high pressure region 4b side is formed. As indicated by the symbol δ, the protruding amount of the side wall on the high pressure region 4a side of the annular housing groove 31b from the bottom wall of the annular housing groove 31b is the minimum necessary to prevent the floating ring 32 from dropping from the annular housing groove 31b. The amount is set.

  The floating ring 32 has an annular shape that is significantly thinner than the wear ring 31, and has a circular cross section that extends from an end surface on the low-pressure region 4a side (left end surface in the drawing) to an end surface on the high-pressure region 4b side (right end surface in the drawing). A through hole (auxiliary through hole) 32a is formed. The mouth ring portion 19 of the impeller 5B passes through the through hole 32a from the high pressure region 4b side. The floating ring 32 is fitted into the annular housing groove 31b from the end surface of the wear ring 31 on the high-pressure region 4b side by bending itself.

  Next, the dimensions of the wear ring 31 and the floating ring 32 will be described in detail. In the description of the dimensions, it is assumed that the through hole 31a, the through hole 32a, and the mouth ring portion 19 are coaxial.

The diameter _{D m1} of the through hole 31a of the wear ring 31 is set larger than the diameter (outer diameter) _{D r} of the mouth ring portion 19 of the impeller 5B. Thus, between the outer peripheral surface of the hole wall and the mouth ring portion 19 of the through-hole 31a is an annular gap (first gap) 35 having a width C ₂ corresponding to the difference between the diameter D _m1 and the diameter D _r Is formed. The end portion of the high pressure area 4b side of the chamfered portion 31c has a larger diameter _{D c} than the diameter _{D m1} of the through hole 31a. Furthermore, since the protrusion amount δ of the side wall of the annular housing groove 31b on the high pressure region 4b side is set to the minimum as described above, the opening of the through hole 31a on the end surface of the wear ring 31 on the high pressure region 4b side is It has a diameter D _m3 that is significantly larger than the diameters D _m1 and D _c of the other part (including the chamfered part 31 _c ) of the through hole 31 a.

The diameter _{D a1} of the through hole 32a of the floating ring 32 is set larger than the diameter _{D r} of the mouth ring portion 19 of the impeller 5B. Thus, between the outer peripheral surface of the hole wall and the mouth ring portion 19 of the through hole 32a is an annular gap (second gap) 36 having a width C ₁ corresponding to the difference between the diameter D _a1 and the diameter D _r Is formed. The diameter D _a1 of the through hole 32a is set smaller than the diameter D _m1 of the through hole 31a. Accordingly, the width C _{1 of the} gap 36 is narrower than the width C _{2 of the} gap 35.

The outer diameter (diameter) D _a2 of the floating ring 32 is set to be smaller than the diameter D _m2 of the bottom wall of the annular housing groove 31b formed in the wear ring 31. Therefore, an annular gap (third gap) 37 having a width C _s (which is sufficiently larger than the width C _{1 of the} gap 36) is formed between the bottom wall of the annular housing groove 31 b and the outer periphery of the floating ring 32. Has been. Therefore, the floating ring 32 can move in the direction perpendicular to the axis L (the radial direction of the floating ring 32 itself) by a distance corresponding to the width C _s of the gap 37 at the maximum. The width C _{2 of the} gap 35 is set larger than the sum of the width C ₁ of the gap 36 and the width C _s of the gap 37. In other words, the widths C ₁ , C ₂ , and C _s have the relationship of the following formula (1).

A distance t ₁ between a pair of opposite side walls of the annular housing groove 31 b is set to be larger than a thickness t ₂ of the floating ring 32. Therefore, floating ring 32 can move by a distance corresponding to a difference between distances t ₁ and the thickness t ₂ axis L direction (floating ring 32 itself in the thickness direction).

  Referring to FIG. 3, knurling 38 is applied to the peripheral wall of the through hole 31 a, specifically, a portion of the peripheral wall of the through hole 31 a in the low pressure region 4 a rather than the chamfered portion 31 c to increase the surface roughness. The fluid frictional resistance acting on the water passing through the gap 35 is increased. In FIG. 3, for the sake of simplification, the knurl process 38 is illustrated only in a part of the circumferential direction of the peripheral wall of the through hole 31a. Is knurled 38. As shown in FIG. 4A, the knurling process 38 may be such that a rectangular recess 38a is surrounded by a linear protrusion 38b, or a triangular protrusion 38b is surrounded by a linear protrusion as shown in FIG. 4B. If the fluid frictional resistance acting on the water passing through the gap 35 can be sufficiently increased, the surface roughness of the peripheral wall of the through hole 31a may be increased by a process other than the knurling process 38.

  Next, how the sealing device 25B performs the sealing function during the operation of the centrifugal pump 1 will be described.

Since the floating ring 32 can move to some extent in the radial direction as described above, the floating ring 32 autonomously moves to the hydrostatic balance position with respect to the rotating mouth ring portion 19 and maintains this position. In this balanced position, a gap 36 having a width C ₁ that is substantially equal to the entire circumference is formed between the hole peripheral wall of the through hole 32 a of the floating ring 32 and the outer peripheral surface of the mouth ring portion 19.

Further, as described above, the floating ring 32 is also movable in the thickness direction, and the high pressure region 4a side is caused by the pressing force Fa generated by the pressure difference between the pressure acting on the end surface on the high pressure region 4b side and the end surface on the low pressure region 4a side. To the low pressure region side 4b. As a result, as shown in FIG. 6, the floating ring 32 is pressed against one side wall (left side wall in the figure) of the annular housing groove 31b. The pressing force _Fa is expressed by the following formula (2).

In the formula (2), the _{P H} at a pressure of the high pressure area 4b, the _{P C} is the pressure of the chamfer portion 31c.

As is apparent from reference to the equation (2), the pressing force F _a can be adjusted by changing the pressure P _c of the chamfer portion 31c. The pressure of the chamfer portion 31c can be adjusted by varying the diameter D _c of the right end portion in FIG chamfer 31c _(ratio of the diameter towards the low pressure area 4a side to the high pressure area 4b side). Therefore, the pressing force Fa can be easily adjusted by changing the size and shape of the chamfered portion 31c.

The differential pressure of the pressure P _L of the pressure P _H and the low pressure region 4a of the high pressure area 4b, water leakage occurs towards the low pressure area 4a from the high pressure area 4b. The leaked water first flows from the high pressure region 4a into the gap 36 between the through hole 32a of the floating ring 32 and the mouth ring portion 19, and further from the chamfered portion 31c to the through hole 31a and mouth ring portion of the wear ring 31. It flows to the low-pressure area | region 4a through the clearance gap 35 between. The sealing device 25B includes a floating ring 32 that is separate from the wear ring 31, and the diameter D _a1 of the second through hole formed in the floating ring 32 is the diameter D _{m1 of} the through hole 31a formed in the wear ring 31. The gap 36 is set narrower than the gap 35 (widths C ₁ and C ₂ ). As a result, the amount of fluid leaking from the high pressure region 4b to the low pressure region 4a via the gap 36 and the gap 35 can be minimized. By minimizing the leakage amount, leakage loss can be reduced and the efficiency of the centrifugal pump 1 can be improved. Moreover, since the fluid frictional resistance which acts on the water which flows through the clearance gap 35 is increased by giving the knurling process 38 to the hole surrounding wall of the through-hole 31a, the amount of water leaking from the high pressure region 4b to the low pressure region 4a is further increased. It can be further reduced. As a result, leakage loss is further reduced and efficiency is further improved.

Than the width C ₁ of the gap 36 of the floating ring 32 positioned high pressure area 4b side, the width C ₂ of the gap 35 of the wear ring 31 located low pressure area 4a side is wide, reducing the flow velocity of water flowing through the gap 35 Is done. Explaining this point, the flow velocity V of the fluid is generally a quotient obtained by dividing the volumetric flow rate Q per unit time by the cross-sectional area A (V = Q / A), so the flow velocity V ₁ in the gap 36 and the flow velocity V in the gap 35. ₂ has the following equation (3).

In this formula (3), A ₁ is the cross-sectional area of the gap 36, and A ₂ is the cross-sectional area of the gap 35. As described above, since the width C ₁ of the gap 36 is smaller than the width C _{2 of the} gap 35 and the cross-sectional area A ₁ is smaller than the cross-sectional area A ₂ , the flow velocity V ₂ in the gap 35 is larger than the flow velocity V ₁ in the gap 36. slow. By thus reducing the flow velocity V ₁ at the gap 35, thereby preventing the wear of the hole wall of the through hole 31a of the wear ring 31. Since general wear amount is proportional to the fifth power of the flow velocity can be effectively prevent wear of the wear ring 31 by reducing the flow velocity V _1. Further, since the flow rate of water near the outlet on the low pressure region side of the gap 35 is reduced, a sudden pressure drop does not occur in this portion, and cavitation can be prevented.

Since than the width C ₂ of the gap 35 of the wear ring 31 is set narrower C ₁ of the gap 36 of the floating ring 32, before mouth ring portion 19 which contacts the wear ring 31 is first brought into contact with the floating ring 32 To do. However, the floating ring 32 because it moves up distance in the radial direction corresponding to the width C _s of the gap 37 in as described above, can reduce damage and wear of the floating ring 32 due to this movement. On the other hand, the width C ₂ of the gap 35 is moved so is set larger than the sum of the width C _s of width C ₁ and the gap 37 of the gap 36, the floating ring 32 is radially pressed by the mouth ring portion 19 Even before, as shown in FIG. 7, before the mouth ring portion 19 collides with the peripheral wall of the through hole 31a of the wear ring 31, the outer periphery of the floating ring 32 comes into contact with the bottom wall of the annular housing groove 31b. Therefore, it is possible to reliably prevent the occurrence of vibration due to the collision between the mouth ring portion 19 and the wear ring 31 and the scoring or burning of the mouth ring portion 19 and the wear ring 31.

Since floating ring 32 is pressed against the side wall of the annular accommodation groove 31b by a pressing force F _a by the differential pressure of the high pressure region 4b and the low pressure area 4a, the mouth ring portion 19 is in contact with the floating ring 32, the pressing force F _a frictional force F _[nu proportional to _{(F ν = μ × F a} : μ is the friction coefficient) with respect to occur, moving the frictional force F _[nu radial floating ring 32 between the floating ring 32 and wear ring 31 It becomes resistance. As a result, the floating ring 32 functions as a damping frictional force with respect to the vibration of the mouth ring portion 19 and reduces the vibration of the mouth ring portion 19. Further, the frictional force _Fv can automatically prevent the floating ring 32 from being rotated by the rotation of the mouth ring portion 19. Since the pressing force F _a as described above can be adjusted in size and shape of the chamfered portion 31c, the frictional force F _[nu easily adjustable in size and shape of the chamfer portion 31c.

  Each of the wear ring 31 and the floating ring 32 is not a structure in which a plurality of parts are assembled, but is an integrated structure composed of a single part, and the floating ring 32 is bent and fitted into the annular receiving groove 31b of the wear ring 31. Thus, the floating ring 32 can be assembled to the wear ring 31. Therefore, the sealing device 25B is easy to manufacture. Further, if necessary, the floating ring 32 can be bent and removed from the wear ring 31 by simply pulling it out of the ring receiving groove 31b of the wear ring 31, and the new replacement floating ring 32 can also be bent into the ring receiving groove 31b. It can be attached to the wear ring 31 simply by fitting. In this respect, the sealing device 25B can be easily maintained.

  The present invention is not limited to the embodiment, and various modifications are possible. For example, the present invention can be applied to other type pumps other than centrifugal pumps, and other fluid machines other than pumps such as compressors and gas turbines. The present invention can also be applied to a seal inside the bush, a portion where the rotating shaft passes through the casing, and the like. Further, a plurality of floating rings 32 may be provided. Furthermore, as shown in FIG. 8, instead of the chamfered portion 31c of the embodiment, a step portion 31d may be provided in a portion connected to the annular accommodating groove 31b of the through hole 31a.

Sectional drawing which shows a centrifugal pump provided with the sealing device concerning embodiment of this invention. The elements on larger scale of the part II of FIG. The disassembled perspective view which shows a wear ring and a floating ring. The elements on larger scale which show an example of the knurling process of a wear ring. The elements on larger scale which show the other example of the knurling of a wear ring. FIG. 4 is a partially enlarged view of a wear ring viewed from an arrow V in FIG. 3. The elements on larger scale of a sealing device (the state where the floating ring was pressed by the wear ring). Partial enlarged view of the sealing device (the state where the outer periphery of the floating ring is in contact with the wear ring). The partial expanded sectional view which shows the alternative of a sealing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal pump 2 Casing 3 Inter bush 4A, 4B Swirl chamber 4a Low pressure region 4b High pressure region 5A, 5B Impeller 6 Main shaft 7A, 7B Bearing bracket 8A, 8B Bearing 9A, 9B Gland packing 11 Suction port 12 Flow path 13 Discharge port 15 Boss portion 16 Main plate 17 Blade 18 Side plate 19 Mouth ring portion 21 Impeller inlet 22 Impeller outlet 25A, 25B Sealing device 31 Wear ring (main ring)
31a Through hole (main through hole)
31b Annular groove 31c Chamfer 32 Floating ring (thin auxiliary ring)
32a Through hole (auxiliary through hole)
35 gap (first gap)
36 gap (second gap)
37 gap (third gap)
38 Knurling 38a Concave part 38b Convex part

Claims (5)

In a sealing device for preventing fluid from leaking from a high pressure region to a low pressure region in the casing through a gap between a casing and a rotating body of a fluid machine,
A main through hole fixed to the casing and penetrating the high pressure region side and the low pressure region side and into which the rotating body is inserted is formed, and a hole peripheral wall of the main through hole and an outer peripheral surface of the rotating body An integral main ring with a first gap formed therebetween;
The main ring is housed in an annular housing groove formed in the peripheral wall of the hole on the high pressure region side of the main through hole, and the rotating body is inserted through the high pressure region side and the low pressure region side. An auxiliary through hole having a diameter smaller than the diameter of the main through hole is formed, and a second gap that is narrower than the first gap is formed between the hole peripheral wall of the auxiliary through hole and the outer peripheral surface of the rotating body. And a thin auxiliary ring having a monolithic structure.   The sum of the dimension of the second gap and the dimension of the third gap formed between the bottom wall of the annular housing groove and the outer periphery of the thin auxiliary ring is smaller than the first gap. The sealing device for a fluid machine according to claim 1.   3. The sealing device for a fluid machine according to claim 1, wherein a distance between a pair of opposing side walls of the annular housing groove is larger than a thickness of the thin auxiliary ring.   The sealing device for a fluid machine according to any one of claims 1 to 3, wherein a diameter-expanded portion is formed in a portion of the main ring through hole facing the low-pressure side of the thin auxiliary ring.   The sealing device for a fluid machine according to any one of claims 1 to 4, wherein the hole peripheral wall of the main through hole is processed to increase surface roughness.

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