JP6087439B2 - Tandem double seal for nuclear power plant - Google Patents

Description

The present invention relates to nuclear power used as a shaft sealing means for a nuclear power plant rotating device (for example, a coolant recirculation pump of a nuclear power plant) whose pressure or temperature changes greatly when the sealed fluid is a high pressure fluid. the present invention relates to the plant for Tandemuda Breakfast Lucille.

  As a shaft sealing means for nuclear power plant rotating equipment operated under high load conditions such as a coolant recirculation pump of a nuclear power plant, a machine is provided between a cylindrical seal case and a rotating shaft penetrating the cylindrical sealing case. A tandem double seal configured so that the inner mechanical seal and the outer mechanical seal are arranged in tandem in a tandem manner, and the in-machine region and the out-of-machine region are sealed through an intermediate region formed between the two mechanical seals. It is known.

  According to such a tandem double seal, it is possible to seal while reducing the pressure in the in-machine region in a stepwise manner through the intermediate region, and it is possible to suitably perform sealing under high load conditions. As described above, when a floating ring type mechanical seal as disclosed in Patent Document 1 is used, a general mechanical seal (which does not have a floating ring and has a fluid to be sealed by a relative rotational sliding contact between a rotating ring and a stationary ring) It is considered that this is more suitable as a shaft seal means for a nuclear power plant that requires a high degree of safety as compared with the case where a mechanical seal configured to seal the above is used.

  That is, as shown in FIG. 19 (FIG. 1A of Patent Document 1), the idle ring type mechanical seal moves in the axial direction through the O-ring 10 to the rotary ring 3 and the seal case 4 fixed to the rotary shaft 1. Between the stationary ring 5 that is freely held and urged in the direction of the rotating ring by the spring 8, an annular floating ring 6 having substantially symmetrical shapes at both ends is sandwiched and held so as to move freely with the rotating ring 3. Due to the relative rotational sliding action of the seal surfaces 3a, 6a which are contact surfaces with the ring 6, a sealed fluid region H which is an outer peripheral side region of the relative rotational sliding contact portion and an unsealed fluid region which is an inner peripheral side region thereof It is configured to shield and shield L, and more effectively exhibits a sealing function under a high load condition as compared to a general mechanical seal having no idle ring.

  For example, in the case of a general mechanical seal having no idle ring, when the fluid to be sealed is a high-pressure fluid, the parallelism of the seal surface that is the contact surface between the rotating ring and the stationary ring is impaired, and a good sealing function Can not demonstrate. That is, the stationary ring is held in the seal case so as to be movable in the axial direction so that it can follow the rotating ring. Although it is hardly affected by the fluid pressure in the sealed fluid region, the influence (pressure strain) is large at the tip side portion of the stationary ring that is free because it follows the rotating ring, that is, the seal surface side portion. Therefore, the pressure strain distribution in the axial direction in the stationary ring becomes non-uniform, that is, the pressure strain is greatly different between the proximal end portion and the distal end side portion in the stationary ring, and the stationary ring is greatly distorted with respect to the axis. As a result, the sealing surface of the stationary ring is inclined, and the parallelism with the sealing surface of the rotating ring is significantly impaired.

  On the other hand, in the idle ring type mechanical seal, the idle ring 6 for exerting the sealing function by the relative rotational sliding contact action with the rotary ring 3 is composed of the rotary ring 3 and the stationary ring 5 as shown in FIG. Between the two ends (upper and lower ends) and having a symmetrical shape in which a pressing portion 61 and a seal portion 62 having substantially the same shape project from each other. The influence of the fluid pressure (pressure of the sealed fluid) is received in a balanced manner in the axial direction. That is, the pressure strain generated in the idle ring 6 is substantially the same at both end portions 61 and 62, and is not greatly distorted with respect to the axis. Therefore, even under a high pressure condition, the seal surface 6a of the idle ring 6 is not inclined with respect to the seal surface 3a of the rotating ring 3, that is, the parallelism of the seal surfaces 3a and 6a is not impaired and is good. Can exhibit a good sealing function.

JP 2004-293766 A

  However, even in the idle ring type mechanical seal, when used under conditions where the pressure or temperature of the sealed fluid is greatly changed, the parallelism of the seal surfaces 3a, 6a is lost, and the seal surfaces 3a, 6a, There is a possibility that abnormal leakage or abnormal wear may occur from between 6a, and a satisfactory sealing function may not be exhibited.

  That is, since the stationary ring 5 and the idle ring 6 are connected in a frictional engagement state in which they are in direct contact with each other and in a relatively non-rotatable state, their pressure strain or thermal strain is generated at the contact portion between the rings 5 and 6. Will interfere with each other. That is, the rings 5 and 6 are connected in a state where their radial strains interfere with each other.

By the way, the stationary ring 5 and the idle ring 6 are made of different materials due to the difference in function and shape. That is, the idle ring 6 that exhibits a sealing function by the relative rotational sliding contact with the rotating ring 3 is made of a general sealing ring material such as carbon that has excellent sliding characteristics with the counterpart ring 3. On the other hand, the stationary ring 5 that is not directly involved in the sealing function but is directly held by the seal case 4 and directly receives the pressing force of the spring 2a is a metal such as stainless steel that is superior in strength and the like as compared with a general sealing ring material. Consists of materials. Therefore, the Young's modulus and the thermal expansion coefficient (linear expansion coefficient) of both 5 and 6 are greatly different, and the Young's modulus and the thermal expansion coefficient of the metal material constituting the stationary ring 5 are the sealing material that is the constituent material of the idle ring 6. It is extremely large compared to the Young's modulus and thermal expansion coefficient of the ring material. For example, the Young's modulus of carbon, which is a constituent material (general sealing ring material) of the idle ring 6, is 2500 kg / mm ² , and the thermal expansion coefficient is 4 × 10 ^{−6 to} 5 × 10 ⁻⁶ mm / ° C. On the other hand, the Young's modulus of stainless steel which is a constituent material of the stationary ring 5 is 19700 kg / mm ² , and the thermal expansion coefficient is 16 × 10 ^{−6 to} 20 × 10 ⁻⁶ mm / ° C.

  Therefore, under the condition that the pressure of the sealed fluid is greatly changed, the radial strain (pressure strain in the radial direction) of both the rings 5 and 6 is greatly different, and the radial strain of the stationary ring 5 is the diameter of the idle ring 6. Since it is much smaller than the directional strain, the floating ring 6 is strongly influenced by the pressure strain of the stationary ring 5 at the contact portion of both rings 5 and 6, and is completely different from its own pressure strain. Presents a state. As a result, the flatness of the seal surface 6a of the idle ring 6 and the concentricity and parallelism with respect to the mating seal surface (the seal surface of the rotating ring 3) 3a are impaired, and the sealing function due to relative rotation of the seal surfaces 3a and 6a is impaired. There is a possibility that it may become stable or deteriorate, and in an extreme case, the sealing function may be lost. That is, when the sealed fluid is at a high pressure (when the pressure is increased), as shown in FIG. 20, the radial pressure strain (reduced strain) E1 of the stationary ring 5 is the radial pressure strain (reduced strain) of the idle ring 6. (Diameter strain) Since it is significantly smaller than e1, pressure strains E1 and e1 interfere with each other at the contact portions of both rings 5 and 6, and substantial radial strains at the contact portions of the floating ring 6 are obtained. Is significantly reduced from its own radial strain (pressure strain) e1. As a result, a moment (hereinafter referred to as “inner opening moment”) M1 in the direction shown in FIG. 20 acts on the idle ring 6 with respect to the stationary ring 5, and the seal surface 6a of the idle ring 6 As shown in FIG. 6, the inner opening state with respect to the mating seal surface 3a (the seal surface 6a is in contact with the mating seal surface 3a on the outer peripheral side, but is not in contact with the mating seal surface 3a on the inner peripheral side). Will lean on. Further, when the sealed fluid is depressurized from this state, as shown in FIG. 21, the radial pressure strain (expanded strain (restoration deformation amount)) E2 of the stationary ring 5 is in the radial direction of the idle ring 6. Since it is much smaller than the pressure strain (expanded strain (restoration deformation amount)) e2, the pressure strains E2 and e2 interfere with each other at the contact portion of both rings 5 and 6, and the contact of the floating ring 6 The substantial radial strain in the part will be significantly reduced from its own radial strain (pressure strain) e2. As a result, a moment (hereinafter referred to as “outward opening moment”) M2 in the direction opposite to that during the pressure increase acts on the floating ring 6, and the sealing surface 6a of the floating ring 6 is shown by a chain line in FIG. It will be inclined outwardly with respect to the mating seal surface 3a (the seal surface 6a is in contact with the mating seal surface 3a on its inner peripheral side but is not in contact with the mating seal surface 3a on its outer peripheral side).

  Moreover, in the in-machine mechanical seal, when an outward opening moment occurs, the seal surface 6a of the idle ring 6 is in an outwardly open state with respect to the mating seal surface 3a, and a large amount of leakage occurs between the seal surfaces 3a and 6a to the intermediate region. There is a risk of it occurring. In such a case, since the pressure in the intermediate region increases and the differential pressure between the in-machine region sealed by the in-machine mechanical seal and the intermediate region becomes small, the seal surface 6a of the idler ring 6 in the in-machine mechanical seal is more greatly removed. It will tilt to the open state. In addition, if leakage occurs from the intermediate area to the outside area in the outboard mechanical seal, the pressure in the intermediate area decreases and the differential pressure between the inboard area and the intermediate area increases. The seal surface 6a of the idle ring 6 in the seal is largely inclined inwardly. Under such conditions where the pressure of the fluid to be sealed is greatly changed, the tandem double seal composed of two floating ring type mechanical seals is compared with the single seal composed of one floating ring type mechanical seal. Therefore, there is a possibility that the seal surface 6a of the idle ring 6 is more inclined, and a good sealing function cannot be exhibited.

  These problems similarly occur even under conditions where the temperature of the sealed fluid is large and changes in height. That is, under the condition that the temperature of the sealed fluid is greatly changed, the radial strains (thermal strains in the radial direction) of both rings 5 and 6 are greatly different, and the thermal strain of the stationary ring 5 is the thermal strain of the idle ring 6. Therefore, the floating ring 6 is strongly influenced by the thermal strain of the stationary ring 5 at the contact portion of both rings 5 and 6, and has a completely different strain state from its own thermal strain. Will be presented. As a result, the flatness of the seal surface 6a of the idle ring 6 and the concentricity and parallelism with respect to the mating seal surface (the seal surface of the rotating ring 3) 3a are impaired, and the sealing function due to relative rotation of the seal surfaces 3a and 6a is impaired. There is a possibility that it may become stable or deteriorate, and in an extreme case, the sealing function may be lost. That is, when the sealed fluid is hot (when the temperature is raised), as shown in FIG. 22, the radial strain (thermal expansion strain) F1 of the stationary ring 5 is the radial strain (thermal expansion strain) of the idle ring 6. Since it is much larger than f1, the radial thermal strains F1 and f1 interfere with each other at the contact portions of the rings 5 and 6, and the substantial radial strain at the contact portions of the floating ring 6 is substantially reduced. Will be significantly greater than its own radial strain (thermal strain) f1. As a result, the inner ring moment M1 shown in FIG. 22 acts on the stationary ring 5 on the idle ring 6 as in the case of the above pressure increase, and the seal surface 6a of the idle ring 6 is shown by a chain line in FIG. As shown in the drawing, it is inclined inwardly with respect to the mating seal surface 3a. When the temperature of the sealed fluid is lowered from this state, as shown in FIG. 23, the radial thermal strain (thermal contraction strain) F2 of the stationary ring 5 is the radial thermal strain (thermal contraction) of the idle ring 6. Strain) because it is much larger than f2, the thermal strains F2 and f2 interfere with each other at the contact portions of both rings 5 and 6, and the substantial radial strain at the contact portions of the free ring 6 is This is greatly increased from its own radial strain (thermal strain) f2. As a result, the open ring moment (moment in the direction opposite to that at the time of temperature rise) M2 acts on the floating ring 6 in the same manner as when the pressure is lowered, and as shown in FIG. The surface 6a is inclined outwardly with respect to the mating seal surface 3a.

  Further, in the case of a tandem double seal for a nuclear power plant, it is generally used under the condition that the flushing flow rate is reduced, and the flushing fluid is moved from the seal part (the relative rotational sliding contact part between the rotary ring and the idle ring) to the idle ring. Flushing means (hereinafter referred to as “reverse flushing”) that passes and flows to the stationary ring is adopted, but in such reverse flushing, the temperature change of the flushing fluid increases due to sliding heat generation at the seal portion. The effect of sliding heat generation on the stationary ring is also increased. As a result, the inclination of the seal surface 6a of the idle ring 6 described above may be further increased.

  In the present invention, when the fluid to be sealed is a high-pressure fluid, the mating seal surface (seal surface of the rotating ring) is not tilted even under conditions where the pressure or temperature is greatly changed. It is an object to provide a tandem double seal for a nuclear power plant that can properly contact with each other and exhibit a good sealing function.

In the present invention, an in-machine mechanical seal and an out-of-machine mechanical seal are arranged in tandem between a cylindrical seal case and a rotary shaft that penetrates the cylindrical seal case, and both the in-machine region and the out-of-machine region are mechanically arranged. In a tandem double seal for a nuclear power plant configured to seal through an intermediate region formed between the seals, in order to achieve the above object, in particular, each mechanical seal includes a rotary ring fixed to a rotary shaft, Relative rotation between the rotating ring and the idle ring is performed by holding the floating ring in contact with the rotating ring and the stationary ring between the stationary ring and the stationary ring arranged on the outside of the machine. It is a floating ring type mechanical seal configured to exert a sealing function by sliding contact action, and is arranged on the outer ring side of the rotating ring relative to the rotating ring on the floating ring of each mechanical seal in the axial direction. A thin-walled cylinder extending in the axial direction from a thick-walled annular main body portion whose one end portion is in contact with the floating ring and an inner peripheral edge portion of the other end portion thereof, forming a cooling hole penetrating the floating ring. A cylindrical body with an L-shaped cross section consisting of a cylindrical holding part, fitted and held in the inner periphery of the seal case so that it can move in the axial direction with an O-ring interposed between it and the holding part In addition, the stationary ring is composed of a floating ring component and a metal material whose Young's modulus and / or thermal expansion coefficient approximates, and a flushing fluid injection region is formed around the in-machine mechanical seal in the in-machine region. the case, Yes to form an inlet passage for guiding the fluid of the implanted region from the peripheral region of the stationary ring of the inboard mechanical seal to the peripheral region of the rotating ring of the outboard mechanical seal in the intermediate region, the mechanical Sea Floating ring is intended made of carbon, in which a stationary ring of the mechanical seal proposes a nuclear power plant for a tandem double seal, characterized in that it is made of titanium or a titanium alloy.

  In a preferred embodiment of such a tandem double seal for a nuclear power plant, an outflow path is formed in the seal case for guiding the fluid in the intermediate region from the peripheral region of the stationary ring of the outside mechanical seal to the outside of the seal case. The inflow passage and the outflow passage each have a decompression passage in which a plurality of wide and narrow portions are continuous, and the fluid is decompressed by passing through the decompression passage. In this case, the inflow passage and the decompression passage of the inflow passage are respectively a plurality of machine interior cylindrical spaces arranged in parallel in the circumferential direction of the seal case, and the seal case surrounding the seal case. A plurality of outer cylinder spaces having the same diameter as the inner cylinder space parallel to the direction, and a plurality of orifice holes that connect the inner cylinder space and the outer circle so as to form a series of passages. It is preferable that it is configured with an orifice hole having a smaller diameter than the circular hole. Further, the inboard cylinder space and the outboard cylinder space are formed at the same pitch P over the entire circumference of the seal case, and the inboard cylinder space and the outboard cylinder space are half pitch P in the circumferential direction of the seal case. The pressure reducing passage of the inflow passage is formed by an in-machine cylindrical space and an out-of-machine cylindrical space formed in one of the half portions in the circumferential direction of the seal case, and an orifice hole connecting these cylindrical spaces. It is preferable that the decompression passage of the inflow path is configured by an in-machine cylindrical space and an out-of-machine cylindrical space formed in the other half portion and an orifice hole that connects these cylindrical spaces.

  In the tandem double seal for a nuclear power plant according to the present invention, the stationary ring is made of a component material of the floating ring and a metal material whose Young's modulus and / or thermal expansion coefficient approximates (for example, the floating ring is made of carbon. In some cases, the stationary ring is made of titanium). Therefore, even when the pressure or temperature of the fluid to be sealed is high, the pressure at the contact portion between the stationary ring and the free ring is high. A moment that tilts the idler ring due to mutual interference of radial strains does not act, and the seal surface of the idler ring and the rotary ring properly come into contact with each other, so that a good and stable sealing function can be exhibited. In addition, since the flushing fluid is configured to sequentially pass through both mechanical seals from the injection region in the in-machine region by an inflow passage formed in the seal case, both mechanical seals can be cooled without requiring a large amount of flushing fluid. In addition, the sealing surface can be effectively lubricated, and the sealing function of both mechanical seals can be exhibited more satisfactorily and stably. Therefore, according to the tandem double seal for a nuclear power plant of the present invention, a very good sealing function can be exhibited even in a nuclear power plant rotating device that requires strict and high safety.

FIG. 1 is a sectional view showing an example of a tandem double seal for a nuclear power plant according to the present invention. FIG. 2 is an enlarged detail view of the main part (machine-side mechanical seal) of FIG. FIG. 3 is an enlarged detail view of another main part (an outside mechanical seal) of FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is an enlarged detail view of the main part of FIG. FIG. 7 is an enlarged detail view of another main part of FIG. FIG. 8 is a developed sectional view taken along line VIII-VIII in FIG. FIG. 9 is a developed sectional view taken along line IX-IX in FIG. FIG. 10 is an enlarged detail view of the main part of FIG. FIG. 11 is an operation explanatory view showing the main part of FIG. 2 and showing a state during boosting. FIG. 12 is an operation explanatory diagram corresponding to FIG. FIG. 13 is a diagram for explaining the operation corresponding to FIG. FIG. 14 is an operation explanatory view showing the main part of FIG. 2 and showing a state at the time of step-down. FIG. 15 is an operation explanatory diagram corresponding to FIG. FIG. 16 is an operation explanatory view corresponding to FIG. 14 showing a state at the time of step-down that is different from FIGS. FIG. 17 is an action explanatory view showing the main part of FIG. 2 and showing the state at the time of temperature rise. FIG. 18 is an operation explanatory diagram corresponding to FIG. FIG. 19 is a cross-sectional view (corresponding to FIG. 1 (a) of Patent Document 1) showing a main part of a conventional idle ring type mechanical seal. FIG. 20 is an operation explanatory view showing the main part of FIG. 19 and showing a state during boosting. FIG. 21 is an operation explanatory diagram corresponding to FIG. FIG. 22 is an action explanatory view showing the main part of FIG. 19 and showing a state at the time of temperature rise. FIG. 23 is an operation explanatory diagram corresponding to FIG.

  Hereinafter, embodiments of the present invention will be specifically described with reference to FIGS. FIG. 1 is a cross-sectional view showing an example of a tandem double seal for a nuclear power plant according to the present invention, FIG. 2 is an enlarged detail view of the main part (in-machine mechanical seal) of FIG. 1, and FIG. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1, and FIG. 5 is a cross-sectional view taken along line V-V in FIG. 6 is an enlarged detailed view of the main part of FIG. 5, FIG. 7 is an enlarged detailed view of the other main part of FIG. 5, and FIG. 8 is a developed sectional view taken along line VIII-VIII of FIG. 9 is a developed cross-sectional view taken along line IX-IX in FIG. 7, FIG. 10 is an enlarged detail view of the main part of FIG. 2, and FIG. FIG. 12 is a diagram for explaining the operation equivalent to FIG. 11 showing the state during boosting, which is different from FIG. 11, and FIG. FIG. 14 is an operation explanatory diagram equivalent to FIG. 11 showing a state at the time of step-up different from FIG. 14, FIG. 14 is an operation explanatory view showing the main part of FIG. 2 and showing a state at the time of step-down, and FIG. FIG. 16 is an operation explanatory diagram corresponding to FIG. 14 showing a state at the time of step-down different from FIG. 14, FIG. 16 is an operation explanatory view equivalent to FIG. 14 showing a state at the time of step-down different from FIGS. FIG. 18 is an operation explanatory view showing the main part 2 taken out and showing a state at the time of temperature increase, and FIG. 18 is an operation explanatory view corresponding to FIG. 17 showing a state at the time of temperature decrease. In the following description, the top and bottom mean the top and bottom of FIG.

  The tandem double seal for a nuclear power plant shown in FIG. 1 is a vertical nuclear plant rotating device (for example, nuclear power plant) used under the condition that the fluid to be sealed (sealed fluid) is high pressure and its pressure or temperature is greatly changed. Used as a shaft sealing means for a power plant coolant recirculation pump, etc., and a cylindrical sealing case 1 attached to a shaft sealing portion casing 6 of the rotating device and rotation passing through the cylindrical sealing case 1 in the vertical direction. An in-machine region A and an out-of-machine region B are formed between the mechanical seals S1 and S2 by arranging the in-machine mechanical seal S1 and the out-of-machine mechanical seal S2 in tandem between the shafts 3 and the shaft 3. It is configured to seal through C. In this example, the fluid in the in-machine region A (sealed fluid) is demineralized water (canned water), and the out-of-machine region B is the atmospheric region.

  Both mechanical seals S1 and S2 have the same configuration as shown in FIG. That is, as shown in FIG. 2 or FIG. 3, each mechanical seal S1, S2 is arranged on the rotary ring 4 fixed to the rotary shaft 3 and on the outside region side (upper side) thereof, and moves in the axial direction to the seal case 1. A stationary ring 2 that can be held, and a floating ring 5 that is held between the two rings 2 and 4 while being in contact with the upper stationary ring 2 and the lower rotating ring 4. 4 and the floating ring 5 are contact surfaces of the seal surfaces 4a and 53a, and the sealed fluid region (the inboard mechanical seal S1) is the outer peripheral region of the relative rotation and sliding contact portions 4a and 53a. The in-machine region A, and in the in-machine mechanical seal S2, the intermediate region C) and the non-sealed fluid region (in-machine mechanical seal) which is the inner peripheral side region of the relative rotational sliding contact portions 4a and 53a. In S1, it is the middle region C, and the outboard side In the Nikarushiru S2 as a configured floating ring type mechanical seal to shield seals the atmospheric region B is) and is outside the region.

  As shown in FIG. 1, the seal case 1 has a cylindrical shape attached to the shaft seal casing 6 in a state in which the rotary shaft 3 penetrates concentrically. A flange body 11 attached to the upper end portion), a case main body 12 attached to the flange body 11 in a state of being fitted into the shaft seal casing 6, and an inner side of the machine body fixed to the lower end portion of the case main body 12. The holding body 13 and the outside holding bodies 14, 15, 16 that are fitted and fixed to the lower end portion of the flange body 11 and the upper end portion of the case body 12 are provided. The machine-side holding body is divided into three in the axial direction, and the upper first machine-side holding body 14, the intermediate second machine-side holding body 15 and the lower third machine-side holding body 16 are axially arranged. It is closely connected to.

  As shown in FIG. 2 or 3, the stationary ring 2 of each mechanical seal S <b> 1, S <b> 2 includes a thick-walled annular main body 21 whose one end (lower end) contacts the idler ring 5 and the other end (upper end). Is a metal cylindrical body having an L-shaped cross section composed of a thin-walled cylindrical holding portion 22 extending in the axial direction (upward) from the inner peripheral edge of the inner periphery of the seal case 1. O-ring 7a in the inner part (inner side mechanical seal S1 is the inner peripheral part of inner side holder 13 and in outer side mechanical seal S2 is the inner peripheral part of first outer side holder 14). Is fitted and held in the seal case 1 so as to be movable in the axial direction (vertical direction) while being secondarily sealed by the O-ring 7a. One end surface (lower end surface) of the main body 21 is formed on a pressing surface 21a which is a smooth annular plane orthogonal to the axis. A drive pin 23 extending upward is projected from the other end portion (upper end portion) of the main body portion 21, and an engagement recess 17 (in-machine mechanical seal S <b> 1) formed in the seal case 1. The engaging recess 17 formed in the inner holding body 13 and the engaging recess 17 formed in the first outer holding body 14 in the outer mechanical seal S2). By combining, it is devised that the relative rotation with respect to the seal case 1 is disabled while the stationary ring 2 is allowed to move in the axial direction within a predetermined range. Also, the main body 21 of the stationary ring 2 and the seal case 1 (the inner mechanical seal S1 is the inner carrier 13 and the outer mechanical seal S2 is the first outer carrier 14). A plurality of (only one shown) springs (coil springs) 2a are interposed in the circumferential direction of the seal case 1 at equal intervals between the stationary ring 2 and the rotating ring 4 direction (downward direction). ). Note that the thickness (diameter thickness) of the holding portion 22 is smaller than the thickness (diameter thickness) of the main body portion 21, and in this example, as shown in FIG. The wall thickness is set to about ¼ of the wall thickness of the main body 21. In addition, the axial length of the holding portion 22 is larger than that of the main body portion 21. In this example, the axial length of the holding portion 22 is 1.5 times that of the main body portion 21 as shown in FIG. Is set to about.

  As shown in FIG. 1, the rotary shaft 3 includes a shaft body 31, a sleeve 32 inserted and fixed thereto, a pair of L-shaped annular sections fitted and fixed to one end portion (lower end portion) and an intermediate portion of the sleeve 32. The holding bodies 33 and 33 are provided.

  As shown in FIG. 2 or FIG. 3, the rotary ring 4 of each mechanical seal S <b> 1, S <b> 2 is an annular body having a square cross section and is fitted and fixed to the sleeve 32. One end surface (upper end surface) of the rotary ring 4 is configured as a seal surface 4a which is a smooth annular plane orthogonal to the axis, and the outer peripheral edge of the seal surface 4a has FIGS. 2 and 4 or 3 and As shown in FIG. 5, a plurality of concave portions 41 (hydrocuts) that overlap with the outer peripheral edge portion of the seal surface 53 a of the idle ring 5 described later are formed at equal intervals in the circumferential direction. Further, a reinforcing ring 42 made of a metal material such as titanium (in this example, made of titanium) is fitted to the outer peripheral portion of the rotary ring 4 by shrink fitting or the like, and this reinforcing ring 42 and the annular holding body 33 (inside the machine) Relative rotation is prevented by a plurality of keys 43 between the mechanical seal S1 and the lower annular holder 33, and the outer mechanical seal S2 is the upper annular holder 33). .

  As shown in FIG. 2 or 3, the idle ring 5 of each mechanical seal S1, S2 includes a main body 51 having a rectangular cross section and pressing portions projecting from inner peripheral edge portions of both end surfaces 51a, 51b (upper and lower end surfaces). 52 and a seal portion 53, which are substantially vertically symmetrical. The end surface of the pressing portion 52 is formed on a pressing surface 52a that is a smooth annular plane orthogonal to the axis, and the end surface of the sealing portion 53 is formed on a sealing surface 53a that is a smooth annular plane orthogonal to the axis. Yes.

  Thus, as shown in FIG. 2 or 3, the idle ring 5 is in a state where the pressing surface 52a contacts the pressing surface 21a of the stationary ring 2 and the sealing surface 53a contacts the sealing surface 4a of the rotating ring 4. The biasing force of the spring 2a holds the pressure between the stationary ring 2 and the rotating ring 4. As shown in FIG. 2 or FIG. 3, the idle ring 5 is an inner peripheral portion of the seal case 1 (in the case of the in-machine mechanical seal S1, the inner peripheral portion of the in-machine holding body 13 and the in-machine mechanical seal S2. The inner peripheral portion of the second machine outer holding body 15 is fitted and held via an O-ring 7b so as to be displaceable in the axial direction and the radial direction. Further, the floating ring 5 is configured such that a plurality of drive pins 24 projecting from the main body portion 21 of the stationary ring 2 are engaged with engaging recesses 54 formed in the main body portion 51 of the floating ring 5 with respect to the stationary ring 2. They are connected so as not to rotate relative to each other in a state in which the relative displacement in the radial direction and the axial direction is allowed within a predetermined range. Further, as shown in FIG. 2, FIG. 3 or FIG. 4, the main body 51 of the idle ring 5 is arranged on the outer peripheral side from the pressing portion 52 and the seal portion 53, and a plurality of penetrating through the idle ring 5 in the axial direction. The cooling hole 55 is formed. A through hole 56 is formed in the main body 51 of the idle ring 5 so as to penetrate the bottom of each engaging recess 54 in the axial direction. The through hole 56 and the engaging recess 54 also function as cooling holes. Is devised. In this example, as shown in FIG. 4, 24 cooling holes 55 are formed at equal intervals in the circumferential direction of the idle ring 4, including the cooling holes including the through holes 56 and the engaging recesses 54.

  An O-ring 7c that seals between the rings 2 and 5 (secondary seal) is interposed between the stationary ring 2 and the idle ring 5 in each mechanical seal S1 and S2 in a pinched manner. That is, as shown in FIG. 2 or 3, the O-ring 7 c is opposed to the opposing end surface 21 a between the main body portion 21 of the stationary ring 2 and the main body portion 51 of the idle ring 5 in a state where the O-ring 7 c is fitted to the pressing portion 52 of the idle ring 5. , 51a, and seals between the opposed end surfaces 21a, 51a. As shown in FIG. 10, the O-ring 7c of each of the mechanical seals S1 and S2 has a wire diameter D larger than the interval (O-ring loading width) L between the opposed end surfaces 21a and 51a to be sealed. Thus, the mechanical seal is loaded between the opposed end surfaces 21a and 51a in a compressed state in which the crushing ratio ε (or crushing allowance δ) is an appropriate amount in the assembled state (the operation stopped state where the pressure by the sealed fluid is not acting). ing. The crushing ratio ε of the O-ring 7c in this mechanical seal assembly state (operation stop state) is a fluid to be sealed (in the in-machine mechanical seal S1, the fluid in the in-machine region A and in the out-of-machine mechanical seal S2). In both the operation stop state where the pressure of the fluid in the intermediate chamber C) does not act and the operation state where the pressure acts, it is as much as possible within a necessary and sufficient range so that the sealing between the opposed end surfaces 21a and 51a can be performed satisfactorily. Specifically, the crushing ratio ε is preferably set to 30% or less, and more preferably set to 10% or less. The crushing allowance δ is the amount of compressive deformation of the O-ring 7c when loaded between the opposed end faces 21a and 51a, and the distance from the wire diameter D in an unloaded state (free state indicated by a chain line in FIG. 10) The value obtained by subtracting the distance L between the end faces 21a and 51a (δ = D−L), and the crushing ratio ε is the ratio (%) of the crushing margin δ to the O-ring wire diameter D in an unloaded state (ε = (Δ / D) × 100). The constituent materials of all O-rings used in the tandem double seal for the nuclear power plant including the O-rings 7a, 7b, and 7c are appropriately selected according to the sealing conditions (properties of the fluid to be sealed). In general, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluorine rubber (FKM), silicon rubber (VMQ), ethylene propylene rubber (EPDM), chloroprene rubber (CR), acrylic rubber (ACM), Butyl rubber (IIR) or urethane rubber (U) is used.

  By the way, the stationary ring 2 is made of a metal material, and the idle ring 5 is a constituent material of the rotating ring 4 (for example, a ceramic ring such as silicon carbide or a cemented carbide sealing ring material. In this example, the ring is made of silicon carbide. The tandem double seal for a nuclear power plant according to the present invention is stationary in each of the mechanical seals S1 and S2. The ring 2 is formed of a metal material whose Young's modulus and / or thermal expansion coefficient (linear expansion coefficient) approximates that of the constituent material of the idle ring 5.

In this example, in each of the mechanical seals S1 and S2, the idle ring 5 is made of carbon, and the stationary ring 2 is made of titanium whose Young's modulus and thermal expansion coefficient approximate carbon. That is, the Young's modulus of the titanium (11000kg / mm ^2), although larger than the Young's modulus of the carbon (2500 kg / mm ^2), general stainless steel which is the material of the stationary ring (Young's modulus: 19700kg / mm ²⁾ to Compared to carbon. In addition, although the thermal expansion coefficient of titanium (8 × 10 ^{−6 to} 5 × 10 ⁻⁶ mm / ° C.) is larger than that of carbon (4 × 10 ^{−6 to} 5 × 10 ⁻⁶ mm / ° C.), Compared to stainless steel (thermal expansion coefficient: 16 × 10 ^{−6 to} 20 × 10 ⁻⁶ mm / ° C.), it is close to carbon.

  In the tandem double seal for a nuclear power plant of the present invention, the following flushing means (reverse flushing) is provided in order to effectively cool the mechanical seals S1 and S2.

  That is, as shown in FIG. 1, an injection region A1 of the flushing fluid W is formed around the in-machine mechanical seal S1 in the in-machine region A, and the fluid W1 in the injection region A1 is transferred to the seal case 1 of the in-machine mechanical seal S1. The area around the stationary ring 2 (the area between the stationary ring 2 and the inner carrier 13 and hereinafter referred to as the “first peripheral area”) A2 to the intermediate ring C of the rotating ring 4 of the outer mechanical seal S2 in the intermediate area C. An inflow path 8 leading to a peripheral region (a region between the rotary ring 5 and the second and third machine outer side holders 15 and 16, hereinafter referred to as “second peripheral region”) C <b> 1 is formed. As shown in FIG. 1, the injection area A <b> 1 is an upper area of the in-machine area A, and is divided by a rotating body 34 attached to the shaft body 31 of the rotating shaft 3 from the lower area of the in-machine area A. The rotating body 34 is attached to the shaft main body 31 of the rotating shaft 3 at a position close to the inner side mechanical seal S <b> 1 near the inner peripheral surface of the shaft seal casing 6. In the injection region A1, since the flushing fluid W and the fluid (sealed fluid) in the in-machine region A are mixed, the flushing fluid W has no problem even if mixed with the sealed fluid or is the same type as the sealed fluid. The fluid (liquid) is used. In this example, since the sealed fluid is demineralized water, water is used as the flushing fluid W. The fluid in the injection region A1 is a mixed fluid of the fluid (sealed fluid) in the in-machine region A and the flushing fluid W as described above. Since both fluids are water, the injection region A1 will be described below. This fluid will be described as a flushing fluid W.

  The flushing fluid W is injected from the flushing passage 61 provided in the shaft seal casing 6 into the injection region A1, and the sealing portion of the in-machine mechanical seal S1, that is, the relative rotational sliding contact portions 4a and 53a of the rotary ring 4 and the idle ring 5 are provided. Cool down. At this time, as shown in FIGS. 2 and 4, the outer peripheral edge of the seal surface 4 a of the rotary ring 4 of the in-machine mechanical seal S <b> 1 has a plurality of concave portions 41 (overlapping the outer peripheral edge of the seal surface 53 a of the idle ring 5. Since the hydro-cut) is formed, the flushing fluid W is positively introduced between the seal surfaces 4a and 53a which are the relative rotational sliding contact portions of the rotating ring 4 and the idle ring 5, and the sealing surface 4a 53a is effectively cooled and lubricated.

  Then, the flushing fluid W flows from the injection region A1 through the cooling hole 55 (including the through hole 56 and the engagement recess 54) of the idler ring 5 of the in-machine mechanical seal S1, and flows into the first peripheral region A2. Thus, the idle ring 5 is cooled.

  The flushing fluid that has flowed into the first peripheral region A2 (the fluid in the first peripheral region A1, hereinafter referred to as “flushing fluid W1”) passes through the inflow path 8 and passes through the second peripheral region (the outside of the machine in the intermediate region C). The peripheral portion of the mechanical seal S2 around the rotating ring 4) C1 is introduced to cool the seal portion of the outside mechanical seal S2, that is, the relative rotational sliding contact portions 4a and 53a of the rotating ring 4 and the idle ring 5. At this time, as shown in FIGS. 3 and 5, a plurality of recesses 41 (overlapping the outer peripheral edge of the seal surface 53a of the idle ring 5 are formed on the outer peripheral edge of the seal surface 4a of the rotary ring 4 of the machine mechanical seal S2. Since the hydro-cut) is formed, the flushing fluid W is positively introduced between the seal surfaces 4a and 53a which are the relative rotational sliding contact portions of the rotating ring 4 and the idle ring 5, and the sealing surface 4a 53a is effectively cooled and lubricated.

  As shown in FIGS. 1 to 3, the inflow path 8 includes a header chamber 81 formed by closing an annular recess formed in the inner peripheral portion of the case main body 12 of the seal case 1 with an inboard holding body 13, and an inboard holding body. 13, a plurality of inlets 82 that communicate with the header chamber 81 and the first peripheral region A2 in the radial direction, and a first inflow passage 83 that is formed in the case body 12 and that opens at one end to the header chamber 81. A second inflow passage 84 formed on the third machine outer side holding body 16 and having one end portion connected to the other end portion of the first inflow passage 83, and an end portion formed on the third machine outer side holding body 16; The third inflow passage 85 that opens to the second peripheral region C1, and the other end of the second inflow passage 84 and the other end of the third inflow passage 85 that are formed in the second machine outer side holding body 15 are connected to each other. The pressure reducing passages 86, 87, and 88, and the flushing fluid W 1 is supplied from the inlet 82 Header chamber 81, the first inflow passage 83, and a third inlet passage 85 sequentially passes through the second inflow passage 84 and the pressure reducing passage 86, 87, 88 so as to flow into the second peripheral region C1.

  The flushing fluid W1 that has flowed into the second peripheral region C1 cools the seal portion of the outside mechanical seal S2, that is, the relative rotational sliding contact portions 4a and 53a of the rotary ring 4 and the idle ring 5. At this time, as shown in FIGS. 3 and 5, a plurality of recesses 41 (overlapping the outer peripheral edge of the seal surface 53a of the idle ring 5 are formed on the outer peripheral edge of the seal surface 4a of the rotary ring 4 of the machine mechanical seal S2. Since the hydro-cut) is formed, the flushing fluid W1 is positively introduced between the seal surfaces 4a and 53a, which are the relative rotational sliding contact portions of the rotary ring 4 and the idle ring 5, and the seal surface 4a. 53a is effectively cooled and lubricated.

  Then, the flushing fluid W1 passes from the second peripheral region C1 through the cooling hole 55 (including the through hole 56 and the engagement recess 54) of the idle ring 5 of the external mechanical seal S2, and the external mechanical seal in the intermediate region C. S2 flows into the peripheral region C2 of the stationary ring 2 (the region between the stationary ring 2 and the first and second machine outer supports 14, 15 and hereinafter referred to as “third peripheral region”) C2, 3 The floating ring 5 is cooled by the flushing fluid W1 flowing into the peripheral area C2.

  Further, the flushing fluid W1 is decompressed while passing through the decompression passages 86, 87, 88, and the pressure in the intermediate region C is reduced. In this example, the decompression passages 86, 87, 88 are as follows. It is configured.

    That is, as shown in FIG. 3 and FIGS. 5 to 9, the pressure reducing passage of the inflow passage 8 has a plurality of machine-side cylindrical spaces 86 arranged in parallel in the circumferential direction of the seal case 1 and the machine-side cylinder space 86 to the outside of the machine. A plurality of machine-side cylindrical spaces 87 that are positioned and are arranged in parallel in the circumferential direction of the seal case 1, and a plurality of orifice holes 88 that connect these machine-side cylindrical spaces 86 and the machine-side cylindrical spaces 87 so as to form a series of passages. It consists of. As shown in FIG. 5, the machine-side cylindrical space 86 and the machine-side cylindrical space 87 are formed in half portions in the circumferential direction of the second machine-side holding body 15. The machine-side cylindrical space 86 is formed by closing a circular recess formed at an equal pitch P in the circumferential direction at the machine-side end (lower end) of the second machine-side holding body 15 with the third machine-side holding body 16. Has been. The machine-side cylindrical space 87 has a circular recess formed in the machine-side end (upper end) of the second machine-side holding body 15 at an equal pitch (same pitch as the machine-side cylindrical space 86) P in the circumferential direction. It is formed by closing with the outer holding body 14. Although the number of both cylindrical spaces 86 and 87 is the same, the positions in the circumferential direction are half pitch (P / 2) from each other. The cylindrical spaces 86 and 87 have the same diameter, but the axial length of the machine-side cylindrical space 87 is set larger than that of the machine-side cylindrical space 86. Each in-machine cylindrical space 86 and two adjacent in-machine cylindrical spaces 87 are connected to each other by an orifice hole 88 which is a circular hole having a smaller diameter. An inboard cylinder space (hereinafter referred to as “first inboard cylinder space 86a”) located at one end of the inboard cylinder space 86 group arranged in parallel in the circumferential direction is connected to the second inflow passage 84, and the inboard cylinder An inboard cylinder space (hereinafter referred to as “second inboard cylinder space 86 b”) located at the other end of the space 86 group is connected to the third inflow passage 85.

  Accordingly, in the decompression passages 86, 87, 88 of the inflow passage 8, the flushing fluid W1 passes through the orifice hole 88 from the first machine inner cylindrical space 86a and flows into the machine outer cylindrical space 87, and is reversed to be turned on. After passing through the orifice hole 88 from the outer cylinder space 87 and flowing into the machine interior cylinder space 86, the machine interior cylinder space 86 and the machine exterior cylinder space 87 are alternately passed through the orifice holes 88 while being reversed. Then, the air flows out from the second machine inner cylindrical space 86b to the third inflow passage 85, and the pressure is effectively reduced during this time.

  Further, in this example, the seal case 1 is formed with an outflow passage 9 through which the fluid in the intermediate region C flows out from the third peripheral region C2 to the outside of the seal case 1, thereby further reducing and stabilizing the pressure in the intermediate region C. It is devised as follows.

  That is, as shown in FIGS. 1 and 3, the outflow passage 9 is formed in the first outflow passage 91 formed in the first machine outer holding body 14 and opened to the third peripheral region C2, and the second machine outer holding body 15. Decompression passages 92, 93, and 94 that are formed and connected to the first outflow passage 91, and a second outflow passage 95 that is formed in the first machine outer holding body 14 and connected to the decompression passages 92, 93, and 94. And a third outflow passage 96 formed in the flange body 11 and connected to the second outflow passage 94 and opened in the outer peripheral portion of the seal case 1, and the fluid in the third peripheral region C2 (hereinafter referred to as “flushing”). The fluid W <b> 2 ”passes through the pressure reducing passages 92, 93, 94 and the second outlet passage 95 from the first outlet passage 91 and flows out of the seal case 1 from the third outlet passage 96. The flushing fluid W2 that has flowed out of the seal case 1 is circulated to the injection region A1 after passing through a filter or the like.

  As shown in FIGS. 3 and 5 to 9, the decompression passage of the outflow passage 9 is located on the outer side of the plurality of machine interior cylindrical spaces 92 arranged in parallel in the circumferential direction of the seal case 1 and the machine interior cylinder space 92. A plurality of outboard cylindrical spaces 93 arranged in parallel in the circumferential direction of the seal case 1, and a plurality of orifice holes 94 connecting the inboard cylinder spaces 92 and the outboard cylinder spaces 93 so as to form a series of passages. Become. As shown in FIG. 5, the machine-side cylindrical space 92 and the machine-side cylindrical space 93 are half portions in the circumferential direction of the second machine-side outer holder 15 (parts excluding the portions where the decompression passages 86, 87, 88 are formed). Is formed. The machine-side cylindrical space 92 has a third circular recess formed in the machine-side end (lower end) of the second machine-side holding body 15 at an equal pitch (same pitch as the machine-side cylindrical space 86) P in the circumferential direction. It is formed by closing with the outside-side holding body 16. The machine-side cylindrical space 93 has a circular recess formed in the machine-side end (upper end) of the second machine-side holding body 15 at an equal pitch (same pitch as the machine-side cylindrical space 92) P in the circumferential direction. It is formed by closing with the outer holding body 14. Although the number of both cylindrical spaces 92 and 93 is the same, the positions in the circumferential direction are half pitch (P / 2) from each other. The cylindrical spaces 92 and 93 have the same diameter, but the axial length of the outer cylindrical space 93 is set larger than that of the inner cylindrical space 92. Each in-machine cylindrical space 92 and two adjacent in-machine cylindrical spaces 93 are connected to each other by an orifice hole 94 which is a circular hole having a smaller diameter. An outboard column space (hereinafter referred to as “first outboard column space 93a”) located at one end of the outboard column space 93 group arranged in parallel in the circumferential direction is connected to the first outflow passage 91 and is connected to the outboard column space. An outboard cylindrical space (hereinafter referred to as “second outboard cylindrical space 93 b”) located at the other end of the space 93 group is connected to the second outflow passage 95. As shown in FIG. 1, the third outflow passage 96 is provided with a temperature measuring device 97 for measuring the temperature of the flushing fluid W2 passing therethrough. A pressure measuring passage 98 that also serves as a drain is provided in the region C2.

  Accordingly, in the decompression passages 92, 93, 94, the flushing fluid W2 passes through the orifice hole 94 from the first machine-side cylindrical space 93a, flows into the machine-side cylinder space 92, and is inverted to be reversed. Through the orifice hole 94 and flows into the outer cylinder space 93, and after passing through the in-machine cylinder space 92 and the outer cylinder space 93 while alternately inverting through the orifice holes 94, It flows out to the 3rd inflow passage 95 from cylindrical space 93b, and it will be effectively decompressed in the meantime, and it can be made the pressure which can discharge flushing fluid W2 out of seal casing 1 safely.

  The decompression passages 92, 93, 94 in the outflow passage 9 have the same configuration as the decompression passages 86, 87, 88 in the inflow passage 8 except for the circumferential position, including the positional relationship in the axial direction. That is, as shown in FIG. 5, the inboard cylinder spaces 86 and 92 and the outboard cylinder spaces 87 and 93 are formed on the second inboard holder 15 with the same equal pitch P and the inboard cylinder over the entire circumference. The spaces 86, 92 and the machine-side cylindrical spaces 87, 93 are formed in a state where they are half-pitch (P / 2) in the circumferential direction of the second machine-side holding body 15, and the circumferential direction of the second machine-side holding body 15 The decompression passage of the inflow passage 8 is constituted by the in-machine cylindrical space 86 and the out-of-machine cylindrical space 87 formed in one of the half portions and the orifice hole 88 connecting the cylindrical spaces 86, 87, and the half portion. The decompression passage of the outflow passage 9 is constituted by the machine-side cylindrical space 92 and the machine-side cylindrical space 93 formed in the other of the above and the orifice hole 94 connecting these cylindrical spaces 92 and 93. By configuring in this way, the axial length of the second machine outer side holding body 15 forming the pressure reducing passages 86, 87, 88 of the inflow passage 8 and the pressure reducing passages 92, 93, 94 of the outflow passage 9 is made possible. The size of the tandem double seal can be reduced.

  In the floating ring type mechanical seals S1 and S2 configured as described above, the pressing surface 21a of the stationary ring 2 and the pressing surface 52a of the floating ring 5 have radial strain (radial pressure strain or thermal strain). Are in frictional engagement with each other, but the stationary ring 2 is composed of a constituent material (carbon) of the idle ring 5 and a metal material (titanium) whose Young's modulus and thermal expansion coefficient are approximated. Even when the pressure or temperature of the fluid to be sealed is high and changes greatly, an appropriate and good mechanical seal function is exhibited without causing the problems described at the beginning.

  For example, under the condition that the pressure of the sealed fluid (the fluid in the in-machine region A in the in-machine region side mechanical seal S1 and the fluid in the intermediate region C in the out-of-machine region side mechanical seal S2) is greatly changed. When the sealed fluid is pressurized, as shown in FIG. 11, due to the pressure of the sealed fluid, the stationary ring 2 and the idle ring 5 generate pressure strains (reduced strain) E1 and e1 in the inner diameter direction. , 5 contact portions (pressing surfaces) 21a and 52a, the radial pressure strains E1 and e1 interfere with each other. However, although the pressure strain E1 on the pressing surface 21a of the stationary ring 2 is smaller than the pressure strain e1 on the pressing surface 52a of the idle ring 5, both rings 2 and 5 are made of an approximate material of Young's modulus. The difference between the magnitudes of the pressure strains E1 and e1 (strain difference) is very small. Therefore, even when the pressure strains E1 and e1 interfere with each other at the contact portions 21a and 52a of the two rings 2 and 5, the radial strain on the pressing surface 52a of the idle ring 5 is its own radial strain (pressure strain) e1. Therefore, as shown in FIG. 11, a moment (inward opening moment) is applied to the floating ring 5 so that the seal surface 53a is inclined with respect to the mating seal surface (seal surface of the rotating ring 4) 4a. The both seal surfaces 4a and 53a are maintained in an appropriate contact state.

  Further, when the sealed fluid changes in pressure from this state, as shown in FIG. 14, the stationary ring 2 and the idle ring 5 are deformed to expand by restoring the reduced diameter deformation at the time of high pressure. That is, the stationary ring 2 and the idle ring 5 generate pressure strain (expansion strain (restoration deformation amount)) E2 and e2 in the outer diameter direction, and contact portions (pressing surfaces) 21a and 52a of both the rings 2 and 5 are The radial pressure strains E2 and e2 interfere with each other. However, although the pressure strain E2 on the pressing surface 21a of the stationary ring 2 is smaller than the pressure strain e2 on the pressing surface 52a of the floating ring 5, both rings 2 and 5 are made of an approximate material of Young's modulus. The difference in magnitude between the pressure strains E2 and e2 is very small. Therefore, even when the pressure strains E2 and e2 interfere with each other in the contact portions 21a and 52a of the two rings 2 and 5, the radial strain on the pressing surface 52a of the idle ring 5 is its own radial strain (pressure strain) e. And almost the same. As a result, as shown in FIG. 14, a moment (outside opening moment) that tilts the seal surface 53 a with respect to the mating seal surface 4 a does not act on the floating ring 5, and both the seal surfaces 4 a and 53 a are appropriate. Is kept in good contact.

  Further, even under the condition that the temperature of the sealed fluid is greatly changed, the sealing surface of the floating ring 5 is caused by the mutual interference of the thermal strains in the contact portions 21a and 52a of the two rings 2 and 5 as in the case of the pressure change. 53a does not tilt. That is, when the temperature of the sealed fluid is raised, the stationary ring 2 and the idle ring 5 are thermally expanded in the radial direction by the high temperature sealed fluid, and as shown in FIG. In FIG. 2, the thermal strains (thermal expansion strains) F1 and f1 in the radial direction interfere with each other. However, since both rings 2 and 5 are made of an approximate material having a thermal expansion coefficient, these thermal strains F1 and f1 The difference in size is very small. Therefore, even when the radial thermal strains F1 and f1 interfere with each other at the contact portions 21a and 52a of both the rings 2 and 5, the floating ring 5 has its seal surface 53a inclined with respect to the mating seal surface 4a. A moment (inward opening moment) does not act, and as shown in FIG. 17, both seal surfaces 4a and 53a are held in an appropriate contact state. Further, when the temperature of the sealed fluid changes from this state, as shown in FIG. 18, the radial thermal strains (thermal contraction strains) F2 and f2 interfere with each other at the contact portions 21a and 52a of the two rings 2 and 5. However, the difference between the magnitudes of these thermal strains F2 and f2 is very small. Therefore, even when the thermal strains F2 and f2 interfere with each other at the contact portions 21a and 52a of both rings 2 and 5, a moment (external force) causes the floating ring 5 to incline the seal surface 53a with respect to the mating seal surface 4a. The opening moment t) does not act, and as shown in FIG. 18, both the seal surfaces 4a and 53a are held in an appropriate contact state.

  In this way, by configuring the stationary ring 2 and the idle ring 5 with materials having similar Young's modulus and thermal expansion coefficient, even when the sealed fluid is at a high pressure and its pressure and / or temperature changes high and low. In the contact portions 21a and 52a of the two rings 2 and 5, a moment (inward opening moment or outward opening moment) is exerted on the floating ring 5 due to the mutual interference of the radial pressure strain and / or thermal strain. Therefore, the seal surfaces 4a and 5a are held in an appropriate contact state, and a good and stable mechanical seal function is exhibited.

  By the way, even when the stationary ring 2 and the idle ring 5 are made of materials having similar Young's moduli, when the pressure of the sealed fluid is extremely high and the pressure increase or decrease width is extremely large, the contact between both rings 2 and 5 Since the difference in the magnitude of the pressure strains E1, e1 or E2, e2 in the portions 21a, 52a (strain difference (e1-E1 or e2-E2)) increases, the conventional floating ring type mechanical seal described at the beginning Similarly to the above, there is a possibility that a moment for tilting the floating ring 5 may be generated due to mutual interference of radial pressure strains in the contact portions 21a and 52a. That is, when the pressure of the sealed fluid is increased, as shown in the chain line in FIG. 12, the seal surface 53a of the floating ring 5 is caused by the mutual interference of the pressure strains E1 and e1 at the contact portions 21a and 52a of both the rings 2 and 5. The inner surface of the mating seal surface 4a is inclined to be inwardly opened (the seal surface 53a is in contact with the mating seal surface 4a on its outer peripheral side but is not in contact with the mating seal surface 4a on its inner circumferential side). When the opening moment M1 may be applied and the sealed fluid is depressurized, the mutual interference of the pressure strains E2 and e2 at the contact portions 21a and 52a of the two rings 2 and 5 as shown in FIG. As a result, the seal surface 53a of the floating ring 5 is open to the mating seal surface 4a (the seal surface 53a is in contact with the mating seal surface 4a on its inner peripheral side, It is there is a possibility that acts outwardly opening moment M2 to be incline to a state) that does not contact the mating sealing surfaces 4a.

  However, even under such a pressure condition that the moments M1 and M2 act, the stationary ring 2 is a metal cylinder having an L-shaped cross section composed of a thick body portion 21 and a thin holding portion 22. The intermediate portion of the holding portion 22 is configured to be fitted and held in the seal case 1 through the O-ring 7a, thereby preventing the floating ring 5 from tilting and properly contacting the seal surfaces 4a and 53a. I can leave it to you.

  That is, the stationary ring 2 under high pressure conditions (pressurizing conditions) in which the inner opening moment M1 acts on the floating ring 5 due to the mutual interference of the pressure strains E1 and e1 at the contact portions 21a and 52a of both rings 2 and 5. Since the holding portion 22 has a thin cylindrical shape, the holding portion 22 is deformed in a reduced diameter (elastically deformed) because a high-pressure sealed fluid pressure acts on the outer peripheral surface thereof. That is, the holding part 22 has a structure similar to a cantilever support beam that supports an O-ring contact part (an intermediate part of the holding part 22 that contacts the O-ring 7a) in the cross-sectional shape shown in FIG. Therefore, as shown by the chain line in the figure, it is elastically deformed as it is bent and deformed in the inner diameter direction by the sealed fluid pressure. On the other hand, the main body portion 21 connected to the free end of the cantilever support beam has a thick annular shape as compared with the holding portion 22. No deformation occurs. However, since the main body portion 21 and the holding portion 22 are integrally connected, the main body portion 21 is deformed in the inner diameter direction by the deformation of the holding portion 22 as shown in FIG. 21a is displaced in the inner diameter direction. Therefore, the radial distortion of the pressing surface 21a of the main body 21 is substantially increased by the displacement. That is, the substantial radial strain (pressure strain) in the pressing surface 21a of the main body 21 is obtained by adding the radial strain E3 due to the deformation of the holding portion 21 to the radial strain E1 of the main body 21 itself. . As a result, as shown in FIG. 12, the fluid to be sealed is greatly pressurized, so that an inward opening occurs between the radial strain E1 on the pressing surface 21a of the stationary ring 2 and the radial strain e1 on the pressing surface 52a of the idle ring 5. Even when a strain difference (e1-E1) that causes the moment M1 to occur is generated, the strain difference is eliminated or reduced by the radial strain E3 due to the deformation of the holding portion 22 described above. The inward opening moment M1 is not caused by the mutual interference of the radial strains on the pressing surfaces 21a and 52a which are the contact portions of the two rings 2 and 5.

  Further, the pressure is lowered from this state, and as shown in FIG. 15, the floating ring 5 is deformed into the open state by the mutual interference of the radial strains E2 and e2 at the contact portions 21a and 52a of both the rings 2 and 5. Under the pressure condition in which the outward opening moment M2 acts, the holding portion 22 is elastically deformed (restored deformation) in the opposite direction as shown in FIG. Thus, a radial strain E4 in the outer radial direction is generated on the pressing surface 21a, and a substantial radial strain on the pressing surface 21a of the main body 21 is added to the radial strain E2 of the main body 21 itself. The radial strain E4 due to the deformation is weighted. As a result, as shown in FIG. 15, when the fluid to be sealed is greatly depressurized, an outward opening is formed between the radial strain E2 on the pressing surface 21a of the stationary ring 2 and the radial strain e2 on the pressing surface 52a of the idle ring 5. Even when a strain difference (e2-E2) is generated in which the moment M2 acts, the strain difference is eliminated or reduced by the radial strain E4 due to the deformation of the holding portion 22 described above. The outward opening moment M2 does not occur due to the mutual interference of the radial strains on the pressing surfaces 21a and 52a, which are the contact portions of the two rings 2 and 5. Needless to say, the pressure deformation of the stationary ring 2 and the idle ring 5 described above is elastic deformation performed within the elastic limit.

  Thus, even under pressure conditions in which moments M1 and M2 are applied to the free ring 5 due to mutual interference of radial pressure strains in the contact portions 21a and 52a of the two rings 2 and 5, respectively. The amount of strain between the radial strains E1 and E2 on the pressing surface 21a of the stationary ring 2 and the radial strains e1 and e2 on the pressing surface 52a of the idle ring 5 due to the elastic deformation of the holding portion 22 of the ring 2 as described above. Since the difference can be eliminated or reduced, both the sealing surfaces 4a and 53a can be in proper contact with each other without causing the problems described at the beginning under any pressure fluctuation conditions, and a good mechanical sealing function is exhibited. Is done.

  The cross-sectional shape of the stationary ring 2 (thickness dimensions of the main body portion 21 and the holding portion 22) is the size of the radial strains E1 and E2 of the stationary ring 2 and the radial strains e1 and e2 of the idle ring 5. The elastic deformation of the holding portion 22 described above (elastic deformation that causes radial strains E3 and E4) under a pressure condition in which the difference in thickness (difference in strain amount) does not cause the moments M1 and M2 or less. ) Does not occur, and the elastic deformation of the holding portion 22 occurs only under pressure conditions in which the strain difference (e1-E1, e2-E2) increases to such an extent that the moments M1 and M2 are generated. As appropriate, it is set according to the sealing property and the material (particularly Young's modulus) of the stationary ring 2.

  By the way, between the stationary ring 2 and the idle ring 5, as described above, an O-ring 7 c that seals between the rings 2 and 5 (secondary seal) is interposed between the stationary ring 2 and the idle ring 5. If the contact pressure on both rings 2 and 5 of 7c is higher than necessary (that is, if crushing ratio ε or crushing allowance δ of O-ring 7c is higher than necessary), the sealing force by O-ring 7c increases, but both rings Two or five pressure strains and / or thermal strains may interfere with each other even through the O-ring 7c. As a result, the above-described operational effects (see FIGS. 11, 14, 17 and 18) and the cross-sectional shape of the stationary ring 2 due to the fact that both rings 2 and 5 are made of a material having an approximate Young's modulus and / or thermal expansion coefficient. The above-described effects (see FIGS. 13 and 16) due to the L-shaped configuration being hindered, these effects may not be sufficiently exhibited. On the other hand, in order not to cause such a problem, the contact pressure to both the rings 2 and 5 of the O-ring 7c may be lowered (that is, the crushing ratio ε or the crushing allowance δ of the O-ring 7c may be reduced). However, in this case, the sealing force by the O-ring 7c between the two rings 2 and 5 is lowered, and a good idle ring type mechanical seal function cannot be expected.

  However, the crushing ratio ε of the O-ring 7c in the assembled state (operation stopped state) of the idle ring type mechanical seals S1 and S2 is, as described above, between the two rings 2 and 5 in the operation state in which the pressure of the sealed fluid acts. Set as small as possible within a range necessary and sufficient for good sealing (specifically, the crushing ratio ε is preferably set to 30% or less, and set to 10% or less. More preferably), such a problem does not occur, deformation of the floating ring 5 due to the pressure of the sealed fluid acting on the O-ring 7c during operation, poor follow-up of the free ring 5 to the rotating ring 4, etc. The occurrence of trouble can be eliminated as much as possible.

  In addition, as described above, a series of flushing paths through which the flushing fluid W sequentially passes through the mechanical seals S1 and S2 from the injection region A1 are formed by the inflow and outflow paths 8 and 9, so a large amount of flushing fluid W is required. Both the mechanical seals S1 and S2 can be effectively cooled, and the inflow and outflow passages 8 and 9 are provided with pressure reducing passages, so that the pressure in the intermediate region C is reduced as much as possible. It can be stabilized. Further, under the condition that the flow rate of the flushing fluid W is reduced, the flushing fluid W is moved from the seal portion (relative rotational sliding contact portion 4a, 53a between the rotary ring 4 and the idle ring 5) in each of the mechanical seals S1, S2. Since the reverse flushing that flows through 5 to the stationary ring 2 is adopted, the temperature change of the flushing fluid due to the sliding heat generation of the seal portions 4a and 53a increases, and the influence of the sliding heat generation on the stationary ring 2 is also affected. In such a case, the sealing surface 5a of the idle ring 5 is not greatly inclined, and a good sealing function is exhibited.

  Therefore, according to the tandem double seal for a nuclear power plant of the present invention, a very good mechanical seal function can be exhibited even in a nuclear power plant rotating device that requires strict and high safety.

  The configuration of the present invention is not limited to the above-described embodiment, and can be appropriately changed and improved without departing from the basic principle of the present invention. For example, in the case where the idle ring 5 is made of carbon, the constituent material of the stationary ring 2 may be a titanium alloy whose Young's modulus and / or thermal expansion coefficient with respect to carbon is approximately the same as that of titanium. . Further, the constituent materials of both rings 2 and 5 are not limited to the combination of carbon and titanium or a titanium alloy, and the sealing conditions and the like are based on the condition that their Young's modulus and / or thermal expansion coefficient are approximated. It is possible to select appropriately. In addition, the tandem double seal for a nuclear power plant according to the configuration of the present invention is not limited to the above-described shaft-sealing means for a vertical rotating device, but can also be used as a shaft-sealing means for a horizontal rotating device. Needless to say, the same effect as described above is exhibited.

DESCRIPTION OF SYMBOLS 1 Seal case 2 Stationary ring 2a Spring 3 Rotating shaft 4 Rotating ring 4a Seal surface 5 Free ring 6 Shaft seal casing 7a O ring 7b O ring 7c O ring 8 Inflow path 9 Outflow path 11 Flange body 12 Case main body 13 Machine inner side holding | maintenance Body 14 First machine outer holder 15 Second machine outer holder 16 Third machine outer holder 17 Engaging recess 21 Stationary ring body 21a Press surface 22 Stationary ring holder 23 Drive pin 24 Drive pin 31 Shaft body 32 Sleeve 33 Annular holding portion 34 Rotating body 41 Recess 42 Reinforcing ring 43 Key 51 Free ring main body 51a End surface 51b End surface 52 Free ring pressing portion 52a Press surface 53 Free ring seal portion 53a Seal surface 61 Flushing flow path 81 Header Chamber 82 Inlet 83 First inflow passage 84 Second inflow passage 85 Third inflow passage 6 Aircraft inner cylindrical space 86a First Aircraft inner cylindrical space 86b Second Aircraft inner cylindrical space 87 Aircraft outer cylindrical space 88 Orifice hole 91 First outflow passage 92 Aircraft inner cylindrical space 93 Aircraft outer cylindrical space 93a First aircraft outer cylindrical space 93b Cylinder space outside the second machine 94 Orifice hole 95 Second outflow passage 96 Third outflow passage 97 Temperature measuring device 98 Pressure measurement passage also used as a drain A In-machine area A1 Injection area A2 First peripheral area B Outboard area (atmosphere area)
C Intermediate region C1 Second peripheral region C2 Third peripheral region S1 Mechanical seal inside the machine S2 Mechanical seal outside the machine W Flushing fluid W1 Flushing fluid W2 Flushing fluid

Claims (5)

An in-machine area and an out-of-machine area mechanical seal are arranged in tandem between the cylindrical seal case and the rotating shaft that penetrates it, forming an in-machine area and an out-of-machine area between both mechanical seals. A tandem double seal for a nuclear power plant configured to seal through an intermediate region
Each mechanical seal is sandwiched between the rotating ring fixed to the rotating shaft and the stationary ring arranged on the outer side of the machine and held in the seal case in contact with the rotating ring and stationary ring. It is a floating ring type mechanical seal that is configured to exert a sealing function by a relative rotational sliding contact action between the rotating ring and the floating ring while maintaining pressure.
Arranged in the idle ring of each mechanical seal on the outer peripheral side from the relative rotational sliding contact portion with the rotary ring, forming a cooling hole penetrating the idle ring in the axial direction,
The stationary ring of each mechanical seal has an L-shaped cross section composed of a thick-walled annular main body part with one end contacting the floating ring and a thin cylindrical holding part extending in the axial direction from the inner peripheral edge of the other end part. Constructed in a cylindrical body, fitted and held on the inner peripheral part of the seal case so as to be movable in the axial direction with an O-ring interposed between it and the holding part, and the stationary ring is a component of the floating ring And a metal material whose Young's modulus and / or thermal expansion coefficient approximate,
An injecting region for flushing fluid is formed around the in-machine mechanical seal in the in-machine region, and the fluid in the injecting region is rotated in the seal case from the peripheral region of the stationary ring of the in-machine mechanical seal to the outer mechanical seal in the intermediate region. Thea form an inflow path leading to the peripheral region of the ring is,
Each mechanical seal of the floating rings are those made of carbon, a tandem double seal nuclear plant stationary ring of the mechanical seal is characterized in der Rukoto made of titanium or a titanium alloy.   The tandem double for a nuclear power plant according to claim 1, wherein an outflow passage is formed in the seal case for guiding the fluid in the intermediate region from the peripheral region of the stationary ring of the outside mechanical seal to the outside of the seal case. seal.   3. The tandem double seal for a nuclear power plant according to claim 2, wherein each of the inflow path and the outflow path has a decompression path for decompressing a fluid flowing in the inflow path or the outflow path.   The decompression passage of the inflow passage and the decompression passage of the outflow passage are respectively a plurality of in-machine cylindrical spaces arranged in parallel in the circumferential direction of the seal case, and the circumferential direction of the seal case that is located outside the in-machine cylindrical space. A plurality of outer cylinder spaces parallel to each other, and a plurality of orifice holes connecting these inner cylinder spaces and outer cylinder spaces so as to form a series of passages. Item 4. A tandem double seal for a nuclear power plant according to item 3.   The inner cylinder space and the outer cylinder space are formed at the same pitch P over the entire circumference of the seal case, and the inner cylinder space and the outer cylinder space are half pitch P / in the circumferential direction of the seal case. The pressure reducing passage of the inflow passage is constituted by an in-machine cylindrical space and an out-of-machine cylindrical space formed in one of the half portions in the circumferential direction of the seal case, and an orifice hole connecting these cylindrical spaces. And the decompression passage of the inflow / outflow path is constituted by an in-machine cylindrical space and an out-of-machine cylindrical space formed in the other half portion and an orifice hole connecting between these cylindrical spaces. A tandem seal for a nuclear power plant according to claim 4.

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