MECHANICAL SEAL AND COOLING CONDITION ESTIMATION METHOD

Abstract

A mechanical seal (1) comprises a rotating side unit (2) with a rotating seal ring (18) and a stationary side unit (3) with a stationary seal ring (33). Sliding portions (18a and 33a) of the rotating seal ring (18) and the stationary seal ring (33) are cooled by a flushing fluid. A temperature difference detection portion (60) configured to detect a temperature difference (ΔT) between a temperature (T1) of the flushing fluid before cooling the sliding portions (18a and 33a) and a temperature (T2) of the flushing fluid after cooling the sliding portions (18a and 33a) is arranged in the stationary side unit (3).

Description

Technical area

[0001] The present invention relates to a mechanical seal and a cooling state estimation method. State of the art

[0002] As a seal for sealing a sealing target fluid in a rotating machine, for example, a mechanical seal described in Patent Literature 1 is known. The mechanical seal according to Patent Literature 1 includes a rotary seal ring (rotatable seal ring) arranged on a rotating shaft of a rotating machine so as to slide on a stationary seal ring, and a stationary seal ring (fixed seal ring) arranged on a casing of the rotating machine. The sliding portions of the rotary seal ring and the stationary seal ring are cooled and lubricated by a flushing fluid. Literature listPatent literature

[0003] PATENT LITERATURE 1: Japanese Patent Application Laid-Open No. JP 2021- 60 079 A Brief description of the inventionTechnical problem

[0004] In the mechanical seal according to Patent Literature 1, to determine whether the sliding portions of the rotary seal ring and the stationary seal ring are adequately cooled by the flushing fluid, it is necessary to disassemble the mechanical seal and visually and directly observe the sliding portions. Thus, it is difficult to determine the cooling status of the sliding portions while the mechanical seal is operating.

[0005] The present invention has been conceived in view of these circumstances, and an object of the present invention is to provide a mechanical seal and a cooling state estimation method that enable estimation of the cooling state of sliding portions of a rotary seal ring and a stationary seal ring caused by a flushing fluid without directly observing the sliding portions. Solution to the problem

[0006] Aspect (1): The present invention relates to a mechanical seal comprising: a rotary side unit arranged on a rotary shaft so as to be rotatable therewith, and having a rotatable seal ring;and a stationary-side unit disposed on a housing surrounding the rotary shaft and having a stationary seal ring on which the rotatable seal ring slides to seal a seal target fluid in an internal region in the housing, wherein sliding portions of the rotatable seal ring and the stationary seal ring are cooled by a flushing fluid, wherein the mechanical seal has a temperature difference detection portion disposed in the stationary-side unit and configured to detect a temperature difference between a temperature of a first flushing fluid, which is the flushing fluid before cooling the sliding portions, and a temperature of a second flushing fluid, which is the flushing fluid after cooling the sliding portions.

[0007] In the mechanical seal according to the present invention, the temperature difference between the temperature of the first flushing fluid before cooling and the temperature of the second flushing fluid after cooling is detected by the temperature difference detection section. When the temperature difference is relatively large, heat generation at the sliding portions due to frictional heat, etc., increases, so the cooling state of the sliding portions can be roughly estimated as a state where the amount of flushing fluid supplied to the sliding portions is insufficient.

[0008] When the temperature difference is relatively small, the heat generation at the sliding portions is small, so the cooling state of the sliding portions can be roughly estimated as a state in which the sliding portions are appropriately cooled by the flushing fluid.

[0009] Thus, by detecting the temperature difference by the temperature difference detection section, the cooling state of the sliding portions caused by the flushing fluid can be estimated without directly observing the sliding portions of the rotary seal ring and the stationary seal ring.

[0010] Aspect (2): Preferably, the mechanical seal according to the above aspect (1) further comprises a control unit configured to calculate a coefficient of kinetic friction of the sliding portions based on the temperature difference.

[0011] In this case, since the coefficient of kinetic friction calculated by the control unit is closely related to the cooling state of the sliding portions, the cooling state of the sliding portions of the rotary seal ring and the stationary seal ring caused by the flushing fluid can be more accurately estimated from the coefficient of kinetic friction.

[0012] Aspect (3): In the mechanical seal according to aspect (1) or (2), the temperature difference detection portion is preferably a thermocouple having a reference contact and a temperature measuring contact, wherein the reference contact is positioned to be in contact with one of the first flushing fluid or the second flushing fluid, and the temperature measuring contact is positioned to be in contact with the other of the first flushing fluid and the second flushing fluid.

[0013] In this case, the temperature difference between the reference contact and the temperature measuring contact of the thermocouple is the temperature difference between the temperature of the first purge fluid before cooling and the temperature of the second purge fluid after cooling. Thus, the temperature difference detection section can have a simple configuration by using the thermocouple.

[0014] Aspect (4): The present invention also relates to a cooling state estimation method for estimating a cooling state of sliding portions of the rotary seal ring and the stationary seal ring caused by a flushing fluid for a mechanical seal, comprising: a rotary side unit arranged on a rotary shaft so as to be rotatable therewith, and having a rotary seal ring; and a stationary side unit arranged on a housing surrounding the rotary shaft and having a stationary seal ring on which the rotary seal ring slides to seal a sealing target fluid in an internal region in the housing, wherein the cooling state estimation method includes a step of detecting a temperature difference between a temperature of the flushing fluid before cooling the sliding portions and a temperature of the flushing fluid after cooling the sliding portions by a temperature difference detection section.

[0015] In the cooling state estimation method according to the present invention, the temperature difference between the temperature of the flushing fluid before cooling and the temperature of the flushing fluid after cooling is detected by the temperature difference detection section. When the temperature difference is relatively large, heat generation at the sliding sections due to frictional heat, etc., increases, so the cooling state of the sliding sections can be roughly estimated as a state where the amount of flushing fluid supplied to the sliding sections is insufficient.

[0016] When the temperature difference is relatively small, heat generation at the sliding portions is low, so the cooling state of the sliding portions can be roughly estimated as a state where the sliding portions are appropriately cooled by the flushing fluid. Thus, by detecting the temperature difference with the temperature difference detection section, the cooling state of the sliding portions caused by the flushing fluid can be estimated without directly observing the sliding portions of the rotary seal ring and the stationary seal ring.

[0017] Aspect (5): Preferably, the cooling state estimation method according to the above aspect (4) further comprises a step of calculating a coefficient of kinetic friction of the sliding portions based on the detected temperature difference.

[0018] In this case, since the coefficient of kinetic friction is closely related to the cooling state of the sliding areas, the cooling state of the sliding areas of the rotary seal ring and the stationary seal ring caused by the flushing fluid can be more accurately estimated from the coefficient of kinetic friction.

[0019] Aspect (6): Preferably, the cooling state estimation method according to the above aspect (5) further comprises a step of estimating the cooling state of the sliding portions based on the calculated kinetic friction coefficient and a characteristic curve representing the behavior of the kinetic friction coefficient with respect to a dimensionless coefficient for lubricating properties of the sliding portions.

[0020] In this case, using the characteristic curve representing the relationship between the kinetic friction coefficient and the dimensionless coefficient for the lubrication properties of the sliding areas, the lubrication zone in which the sliding areas are located can be estimated with high accuracy. Accordingly, the cooling state of the sliding areas of the rotating seal ring and the stationary seal ring caused by the flushing fluid can be more accurately estimated based on the estimated lubrication zone. Advantageous effects of the invention

[0021] According to the present invention, the cooling state of the sliding portions of the rotary seal ring and the stationary seal ring caused by the flushing fluid can be estimated without directly observing the sliding portions. Short description of the drawings

[0022] The drawings show in: Fig. 1 is a cross-sectional view of a mechanical seal according to a first embodiment of the present invention. Fig. 2 an enlarged cross-sectional view of an adapter ring and an area around it. Fig. 3 a schematic representation of the configuration of a thermocouple. Fig. 4 is a flowchart of a method for estimating a cooling state of sliding portions of a rotary seal ring and a stationary seal ring by a flushing fluid. Fig. 5 a diagram showing a characteristic curve. Fig. 6 is a cross-sectional view of a main portion of a mechanical seal according to a second embodiment of the present invention. Detailed description

[0023] Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. At least parts of the embodiments described below can be combined as desired. First embodimentOverall configuration

[0024] Fig. 1 is a cross-sectional view of a mechanical seal 1 according to a first embodiment of the present invention. In Fig. 1, the mechanical seal 1 is used in a rotating machine 70, such as a pump, and seals a sealing target fluid in the rotating machine 70. The mechanical seal 1 is positioned along the axial direction of a rotating shaft 71 of the rotating machine 70 (hereinafter simply referred to as "axial direction") between the rotating shaft 71 and a housing 72 surrounding the rotating shaft 71.

[0025] The mechanical seal 1 according to the present embodiment comprises a rotary side unit 2 arranged on the rotary shaft 71 so as to be rotatable therewith, and a stationary side unit 3 arranged on the housing 72. In the present description, the right side is referred to for the sake of simplicity. Fig. 1 is called one side in the axial direction, and it is called the left side in Fig. 1 is referred to as the other side in the axial direction (this also applies to the two Fig. 2 and Fig. 6). Rotating page unit

[0026] The rotary side unit 2 comprises a sleeve 11, a stop ring 12, a first holder 13, drive pins 14, a drive collar 15, springs 16, a second holder 17 and a rotatable sealing ring 18.

[0027] The sleeve 11 is formed in a cylindrical shape and is attached to the outer periphery of the rotary shaft 71. The stop ring 12 is attached to the outer periphery of the sleeve 11 on the other side in the axial direction. A plurality of locking screws 19 are screwed into the stop ring 12 in the radial direction so that they are arranged in the circumferential direction of the stop ring 12. Accordingly, the sleeve 11 is fixed to the rotary shaft 71. An O-ring 20 seals (secondarily) between the inner peripheral surface of the sleeve 11 on one side in the axial direction and the outer peripheral surface of the rotary shaft 71.

[0028] The first holder 13 is a spring holder. The first holder 13 is formed in a ring shape and is attached to the outer circumference of the sleeve 11 on one side in the axial direction. A plurality of locking screws 21 (in Fig. 1, only one is shown) is screwed into the first holder 13 in the radial direction so that they are arranged in the circumferential direction of the first holder 13. Accordingly, the first holder 13 is fixed to the sleeve 11. The plurality of drive pins 14 (in Fig. 1 (only one is shown) extends in the axial direction through the first holder 13 such that they are spaced apart from each other in the circumferential direction. The drive pins 14 are held such that they are movable in the axial direction relative to the first holder 13.

[0029] The drive collar 15 is positioned on the other side of the first holder 13 in the axial direction so as to be spaced apart therefrom. The drive collar 15 is formed in a ring shape and attached to the outer peripheral surface of the sleeve 11 so as to be movable in the axial direction with respect to this outer peripheral surface. An end portion on the other side of each drive pin 14 in the axial direction is fixed (bolted) to the drive collar 15. Accordingly, the drive collar 15 is held so as to be movable in the axial direction with respect to the first holder 13 by means of the drive pins 14 and is prevented from rotating relative to the first holder 13.

[0030] The majority of springs 16 (in Fig. 1, only one is shown) is arranged between the drive collar 15 and the first holder 13 so that they are spaced apart from each other in the circumferential direction. Each spring 16 biases the drive collar 15 (in the axial direction) toward the other side in the axial direction against the first holder 13.

[0031] The second holder 17 is positioned adjacent to the drive collar 15 on the other side in the axial direction. The second holder 17 is formed in a ring shape and is attached to the outer peripheral surface of the sleeve 11 such that it is movable in the axial direction relative to this outer peripheral surface. An end portion on the one side in the axial direction of the second holder 17 is fixed to the drive collar 15.

[0032] Accordingly, the second retainer 17 is prevented from rotating relative to the drive collar 15 while being held so as to be movable in the axial direction with respect to the sleeve 11 together with the drive collar 15. An O-ring 22 provides a (secondary) seal between the inner peripheral surface of the second retainer 17 and the outer peripheral surface of the sleeve 11.

[0033] The rotatable seal ring 18 is formed in a ring shape and is fixed (fitted by shrinking) to another end portion in the axial direction of the second holder 17. A sealing surface 18a is formed on the end surface on the other side in the axial direction of the rotatable seal ring 18 (see also Fig. 2). The rotatable sealing ring 18 is biased by the springs 16 toward the other side in the axial direction via the drive collar 15 and the second holder 17. Stationary side unit

[0034] The stationary side unit 3 includes a seal housing 31, a bushing 32, a stationary seal ring 33, and an adapter ring 50. The seal housing 31 is formed in a cylindrical shape. The seal housing 31 is attached to the housing 72 so as to surround the rotating shaft 71 to define an inner region A and an outer region B of the rotating machine 70.

[0035] In the present embodiment, a radially outer portion of the seal housing 31 is fixed to the housing 72 with a bolt 34 in a state where it is in contact with the side surface on the other side of the housing 72 in the axial direction. An O-ring 35 seals (secondarily) between the side surface on one side of the seal housing 31 in the axial direction and the side surface on the other side of the housing 72 in the axial direction.

[0036] The bushing 32 is attached to the inner periphery of the seal housing 31 on the other side in the axial direction. The bushing 32 is formed in an annular shape and forms a gap seal between the outer peripheral surface of the sleeve 11 and the bushing 32. An annular restricting member 36 is attached to the end surface on the other side in the axial direction of the seal housing 31.

[0037] The end surface on the other side of the sleeve 32 in the axial direction is in contact with the restricting member 36. Accordingly, the sleeve 32 is prevented from being pulled out of the seal housing 31 to the other side in the axial direction. The restricting member 36 has an engaging pin 36a that engages the sleeve 32. Accordingly, the restricting member 36 prevents the sleeve 32 from rotating together with the sleeve 11.

[0038] The stationary seal ring 33 is formed in a ring shape and is attached and fixed to the inner peripheral surface of the seal housing 31. An O-ring 37 seals (secondarily) between the outer peripheral surface of the stationary seal ring 33 and the inner peripheral surface of the seal housing 31. A sealing surface 33a is formed on the end surface on one side of the stationary seal ring 33 in the axial direction (see also Fig. 2)

[0039] The sealing surface 18a of the rotatable seal ring 18 slides on the sealing surface 33a of the stationary seal ring 33. Accordingly, the sealing target fluid is sealed in the inner region A. The stationary seal ring 33 is prevented from rotating relative to the rotatable seal ring 18 by a restricting pin 38 fixed to the inner periphery of the seal housing 31.

[0040] The adapter ring 50 is positioned radially outward from the sliding portions (sealing surfaces 18a and 33a) of the rotary seal ring 18 and the stationary seal ring 33 in the inner region A. Hereinafter, the sliding portions of the rotary seal ring 18 and the stationary seal ring 33 are also referred to as sliding portions 18a and 33a. The adapter ring 50 is formed in a cylindrical shape and is detachably mounted on the seal housing 31.

[0041] Fig. Figure 2 is an enlarged cross-sectional view of the adapter ring 50 and an area around it. Fig. 1 and Fig. 2, one side of an outer peripheral surface 50a of the adapter ring 50 in the axial direction is attached to the inner peripheral surface of the seal housing 31. An end surface 50b on the other side of the adapter ring 50 in the axial direction is in contact with a step surface 31e extending in the radial direction on the inner periphery of the seal housing 31.

[0042] An end surface 50c on one side in the axial direction of the adapter ring 50 is in contact with a retaining ring 39 attached to the seal housing 31. Accordingly, the adapter ring 50 is held between the step surface 31e and the retaining ring 39 so that the adapter ring 50 is held so that the adapter ring 50 does not move out of the seal housing 31.

[0043] The retaining ring 39 is removably mounted in an annular recessed groove 31f formed on the inner circumference of the seal housing 31. Thus, the adapter ring 50 can be removed from the seal housing 31 by releasing the retaining ring 39 from the recessed groove 31f. Flow passage for the flushing fluid

[0044] In Fig. 1, a flow passage for supplying a flushing fluid from the outer region B to the inner region A is formed in the stationary side unit 3. The flushing fluid cools and lubricates the sliding portions 18a and 33a of the rotary seal ring 18 and the stationary seal ring 33. In the present embodiment, a seal target fluid is used as the flushing fluid.

[0045] In this specification, the flushing fluid before cooling the sliding portions 18a and 33a is referred to as the first flushing fluid. The flushing fluid after cooling the sliding portions 18a and 33a is referred to as the second flushing fluid. A flow passage through which the first flushing fluid flows is formed in the stationary side unit 3. The flow passage for the first flushing fluid is described below.

[0046] A plurality of holes 31a (two in Fig. 1) is formed on one side of the seal housing 31 in the axial direction so that they are spaced apart from each other in the circumferential direction of the seal housing 31. Each hole 31a is formed so that it penetrates the seal housing 31 in the radial direction. An annular groove 31d (see also Fig. 2) communicating with the respective hole 31a is formed on the inner periphery of the seal housing 31. Each hole 31a can be used as a first flow passage 31b for supplying the first flushing fluid from the outer region B to the inner region A.

[0047] The reason why the plurality of holes 31a, each of which can be used as the first flow passage 31b, is formed in the circumferential direction of the seal housing 31 is that the position in the circumferential direction at which a pipe through which the first flushing fluid flows is connected to the seal housing 31 is different depending on the type of the rotating machine 70, etc.

[0048] In the present embodiment, the Fig. 1 bottom side is used as the first flow passage 31b. Thus, the first flow passage 31b for supplying the first flushing fluid from the outer region B to the inner region A is formed at a predetermined position in the circumferential direction of the seal housing 31 (the lower side in Fig. 1) trained.

[0049] The other hole 31a, which is not used as the first flow passage 31b, is also referred to as the auxiliary hole 31c hereinafter. The opening on the radially outer side of each auxiliary hole 31c is blocked by a blocking member 40. The blocking member 40 includes, for example, a first screw portion 41 that is screwed into the auxiliary hole 31c and a second screw portion 42 that is screwed into the head of the first screw portion 41. The blocking member 40 prevents the first flushing fluid flowing from the annular groove 31d into the auxiliary hole 31c from leaking out.

[0050] In Fig. 2, the adapter ring 50 has a second flow passage 51 that communicates with the plurality of holes 31a (the first flow passage 31b and the auxiliary hole 31c) of the seal housing 31. The second flow passage 51 is a flow passage for supplying the first flushing fluid from the first flow passage 31b to a plurality of locations in the circumferential direction of the sliding portions 18a and 33a. The second flow passage 51 includes an annular flow passage 52 and a plurality of supply flow passages 53.

[0051] The annular flow passage 52 is formed on the outer periphery of the adapter ring 50 at a position opposite to the annular groove 31d of the seal housing 31. The annular flow passage 52 according to the present embodiment is formed from an annular cutout groove formed on the outer periphery of the adapter ring 50. The axial width of the annular flow passage 52 is the same as the groove width of the annular groove 31d of the seal housing 31. Thus, the first flushing fluid flows from the first flow passage 31b in the circumferential direction in a flow passage formed by the annular groove 31d and the annular flow passage 52.

[0052] In Fig. 1 and Fig. 2, the plurality of supply flow passages 53 are flow passages for supplying the first flushing fluid from the annular flow passage 52 to the inner region A. The supply flow passages 53 are formed to penetrate the adapter ring 50 in the radial direction from a plurality of locations in the circumferential direction on the bottom surface of the annular flow passage 52. Accordingly, the first flushing fluid is supplied from the plurality of supply flow passages 53 to the inner region A, so that the entire sliding portions 18a and 33a can be uniformly cooled and lubricated in the circumferential direction.

[0053] Each supply flow passage 53 is formed such that an opening 53a is located on the radially inner side thereof on the other side (outer region B side) in the axial direction relative to the sliding portions 18a and 33a. Accordingly, in the inner region A, the first flushing fluid and the second flushing fluid are generally separated on both sides in the axial direction, with a virtual extension line X of the sliding portions 18a and 33a forming a boundary.

[0054] Specifically, in the inner region A, the first flushing fluid occupies the region on the other side with respect to the virtual extension line X in the axial direction, and the second flushing fluid occupies the region on the one side with respect to the virtual extension line X in the axial direction. Temperature difference detection range

[0055] The mechanical seal 1 further includes a temperature difference detection section 60 arranged in the stationary side unit 3 and a control unit 4. The temperature difference detection section 60 detects a temperature difference ΔT between a temperature T1 of the first flushing fluid and a temperature T2 of the second flushing fluid. The temperature difference detection section 60 according to the present embodiment is formed from a single thermocouple 61. The thermocouple 61 according to the present embodiment is attached to the adapter ring 50.

[0056] Fig. 3 is a schematic representation of the configuration of the thermocouple 61. In Fig. 2 and Fig. 3, the thermocouple 61 is a thermocouple that utilizes the Seebeck effect. The thermocouple 61 has a first conductor 62 and a second conductor 63 made of different metallic materials. The first conductor 62 is made, for example, of an alloy consisting primarily of nickel and chromium. The second conductor 63 is made, for example, of an alloy consisting primarily of nickel and aluminum.

[0057] The first conductor 62 and the second conductor 63 are mounted by inserting them into a mounting hole 54 formed to penetrate the adapter ring 50 in the radial direction. The mounting hole 54 is formed at a position in the adapter ring 50 corresponding to the auxiliary hole 31c. Further, the mounting hole 54 is formed to slope from the other side to the one side in the axial direction and to extend from the outer peripheral surface to the inner peripheral surface of the adapter ring 50.

[0058] An opening 54a on the radially inner side of the mounting hole 54 is positioned in the area on the one side with respect to the virtual extension line X in the axial direction (the area occupied by the second flushing fluid) in the inner area A.

[0059] The mounting hole 54 is sealed by a sealing member (not shown) in a state where the first conductor 62 and the second conductor 63 extend through the mounting hole 54. This sealing member prevents the first flushing fluid flowing through the annular flow passage 52 from flowing through the mounting hole 54 into the area occupied by the second flushing fluid in the inner region A.

[0060] One end of the first conductor 62 and one end of the second conductor 63 are connected to each other in a state where they protrude from the opening 54a of the mounting hole 54 into the region on one side of the inner region A in the axial direction. This connection point is defined as the temperature measuring contact 65 of the thermocouple 61. Thus, in the present embodiment, the temperature measuring contact 65 of the thermocouple 61 is arranged to be in contact with the second flushing fluid.

[0061] The other end of the first conductor 62 and the other end of the second conductor 63 are positioned in the annular flow passage 52 through which the first purge fluid flows, projecting radially outward from the mounting hole 54 and separated from each other. The other end of the first conductor 62 and the other end of the second conductor 63 positioned in the annular flow passage 52 are defined as respective reference contacts 64 of the thermocouple 61. Thus, in the present embodiment, the reference contacts 64 of the thermocouple 61 are positioned to be in contact with the first purge fluid in the annular flow passage 52.

[0062] The other end of the first conductor 62 is connected by welding or the like to a conductive connecting wire 5 made of a different metallic material than the first conductor 62 and the second conductor 63. The other end of the second conductor 63 is connected by welding or the like to a conductive connecting wire 6 made of a different metallic material than the first conductor 62 and the second conductor 63. Each conductive connecting wire 5 or 6 is formed of a conductive wire made of, for example, copper.

[0063] As in Fig. 1 and Fig. As shown in Figure 2, each conductive connecting wire 5 or 6 extends from the reference contact 64 of the thermocouple 61 through the annular flow passage 52 and the auxiliary hole 31c, and extends through the blocking element 40 to the radially outer side of the seal housing 31 (outer region B). One end portion of each conductive connecting wire 5 or 6 in the outer region B is connected to the control unit 4.

[0064] Due to the configuration described above, the thermocouple 61 outputs a thermoelectromotive force corresponding to the temperature difference ΔT occurring between the temperature T1 of the reference contact 64 (the first flushing fluid) and the temperature T2 of the temperature measuring contact 65 (the second flushing fluid) to the control unit 4 via the conductive connecting wires 5 and 6.

[0065] That is, when the thermocouple 61 detects the temperature difference ΔT between the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid, the thermocouple 61 outputs a signal (a thermoelectromotive force) corresponding to the temperature difference ΔT to the control unit 4. The thermocouple 61 detects the temperature difference ΔT and outputs the signal to the control unit 4 at every predetermined time. Control unit

[0066] The control unit 4 is positioned in the outdoor area B. The control unit 4 is configured to include a computer with a CPU, etc. Each function of the control unit 4 is performed by the CPU, which executes a control program stored in a memory device of the computer. The control unit 4 calculates a kinetic friction coefficient µ of the sliding portions 18a and 33a based on the thermoelectromotive force input from the thermocouple 61 at each predetermined time. A specific calculation method will be described below.

[0067] First, the control unit 4 extracts the temperature difference ΔT corresponding to the thermoelectromotive force input from the thermocouple 61, for example, from a table in which the thermoelectromotive force and the temperature difference ΔT are registered in association with each other. The control unit 4 can calculate the temperature difference ΔT from the thermoelectromotive force input from the thermocouple 61 using a predetermined calculation formula.

[0068] Next, the control unit 4 calculates the kinetic friction coefficient μ by substituting the extracted temperature difference ΔT into equation (3), which is derived from equations (1) and (2). Equation (1) is an equation representing a frictional heat value Q [kJ / min] of the sliding portions 18a and 33a. Equation (2) is an equation representing the flow rate Wf [L / min] of the flushing fluid required to cool the sliding portions 18a and 33a. Q=(μ⋅P⋅V)×60÷1000 Wf=Q(Cp⋅γ⋅ΔT) μ=Wf×(Cp⋅γ⋅ΔT)÷(P⋅V)×1000÷60

[0069] Where P is an apparent thrust force [N] applied to the sliding areas 18a and 33a, V is the average peripheral speed [m / s] of the sealing surface 18a of the rotatable sealing ring 18, Cp is the specific heat [kJ / kgK] of the flushing fluid, γ is the density [kg / L] of the flushing fluid, ΔT is the temperature difference [K] between the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid, and P, V, Cp and γ are all known values. Method for estimating the cooling state of sliding areas

[0070] Fig. 4 is a flowchart of a method for estimating a cooling state of the sliding portions 18a and 33a of the rotary seal ring 18 and the stationary seal ring 33 caused by the flushing fluid. The method for estimating the cooling state will be described below with reference to Fig. 4 described.

[0071] First, the temperature difference before and after cooling the purge fluid, that is, the temperature difference ΔT between the temperature T1 of the first purge fluid and the temperature T2 of the second purge fluid, is detected by the temperature difference detection section 60 (step ST1). The temperature difference detection section 60 outputs the thermoelectromotive force corresponding to the temperature difference ΔT to the control unit 4 as described above.

[0072] Next, in the control unit 4, the kinetic friction coefficient μ of the sliding portions 18a and 33a is calculated based on the temperature difference ΔT (step ST2). A specific method for calculating the kinetic friction coefficient μ by the control unit 4 is as described above.

[0073] Next, the cooling state of the sliding areas 18a and 33a is estimated based on the calculated kinetic friction coefficient µ and a characteristic curve CL (step ST3). The characteristic curve CL is a curve representing the behavior of the kinetic friction coefficient µ with respect to a dimensionless coefficient for the lubricating properties of the sliding areas 18a and 33a. The estimation of the cooling state of the sliding areas 18a and 33a is performed, for example, by a company that performs maintenance and inspection of the mechanical seal 1.

[0074] For example, an operating parameter DP is used as a dimensionless coefficient. The operating parameter DP represents the properties (lubricating properties) of a lubricating layer of the flushing fluid that forms on the sliding surfaces 18a and 33a. The operating parameter DP is calculated using the following equation (4). DP=(η×ω×b)÷W

[0075] Where η is the viscosity [Pa s] of the flushing fluid, ω is the circumferential speed [m / s] of the sealing surface 18a of the rotatable sealing ring 18, b is the radial sliding width [m] of the sealing surface 18a, W is a pressure load [N] on the rotatable sealing ring 18 by the springs 16 (see Fig. 1) and the sealing target fluid.

[0076] The characteristic curve CL according to the present embodiment represents the behavior of the kinetic friction coefficient μ with respect to the operating parameter DP. The characteristic curve CL is established in advance by conducting a test or the like for the static load capacity of the mechanical seal 1 while varying the operating parameter DP. The characteristic curve CL is a curve that varies depending on the type of flushing fluid, etc.

[0077] Fig. Figure 5 is a graph showing the characteristic curve CL obtained by the test described above or the like. In this graph, the vertical axis represents the coefficient µ of kinetic friction, and the horizontal axis represents the operating parameter DP. As shown in Fig. As shown in Figure 5, the value of the kinetic friction coefficient µ of the sliding areas 18a and 33a generally changes along the characteristic curve CL according to the value of the operating parameter DP. Due to this change in the value of the kinetic friction coefficient µ, the state of the lubricating layer of the flushing fluid formed on the sliding areas 18a and 33a changes.

[0078] As in Fig. As shown in Figure 5, the state of the lubricating layer of the flushing fluid changes in three regions according to the value of the operating parameter DP. Specifically, the state of the lubricating layer of the flushing fluid changes in the order of a boundary lubrication region, a mixed lubrication region, and a fluid lubrication region as the value of the operating parameter DP increases.

[0079] In the boundary lubrication region, the kinetic friction coefficient µ is relatively large, and the thickness of the lubricating layer of the flushing fluid is relatively thin. Thus, the amount of flushing fluid supplied to the sliding areas 18a and 33a in the boundary lubrication region is insufficient, so that the sealing surfaces 18a and 33a easily come into direct contact with each other, and their wear rate tends to increase.

[0080] In the mixed lubrication region, the kinetic friction coefficient µ is within a suitable range of values, and the thickness of the lubricating layer of the flushing fluid is also within a suitable range of values. In the fluid lubrication region, the kinetic friction coefficient µ is relatively small, and the thickness of the lubricating layer of the flushing fluid is relatively thick. Thus, the sealing target fluid easily leaks from the sliding areas 18a and 33a.

[0081] When estimating the cooling state of the sliding areas 18a and 33a using the characteristic curve CL in Fig. 5, the company first identifies the position on the characteristic curve CL where the value of the kinetic friction coefficient µ calculated by the control unit 4 is located. The characteristic curve CL is essentially V-shaped, with a valley at the position where the kinetic friction coefficient µ reaches its minimum value (near the boundary between the mixed lubrication zone and the fluid lubrication zone).

[0082] Thus, the calculated value of the coefficient µ of kinetic friction on the characteristic curve CL in the mixed lubrication range and on the characteristic curve CL in the fluid lubrication range can have the same value.

[0083] In such a case, the company calculates the value of the operating parameter DP corresponding to the flushing fluid used using the above equation (4). Then, the company identifies the position where the calculated value of the kinetic friction coefficient µ is located on the characteristic curve CL by determining whether the calculated value of the operating parameter DP is greater or less than the value (limit value) of the operating parameter DP corresponding to the minimum value of the kinetic friction coefficient µ.

[0084] Specifically, if the calculated value of the operating parameter DP is greater than the limit value, the company can identify that the calculated value of the kinetic friction coefficient µ on the characteristic curve CL is within the fluid lubrication range. If the calculated value of the operating parameter DP is less than the limit value, the company can identify that the calculated value of the kinetic friction coefficient µ on the characteristic curve CL is within the mixed lubrication range. The limit value of the operating parameter DP is a known value, which is generally constant for each flushing fluid, etc.

[0085] Next, the company checks which of the boundary lubrication area, the mixed lubrication area and the fluid lubrication area has the characteristics CL in the diagram in Fig. 5. The company can estimate the cooling state of the sliding areas 18a and 33a based on the area containing the position identified on the characteristic curve CL.

[0086] In particular, when the position identified on the characteristic curve CL is in the boundary lubrication region, the thickness of the lubricating layer of the flushing fluid is relatively thin as described above, so that the cooling state of the sliding portions 18a and 33a can be estimated as a state in which the amount of the flushing fluid supplied to the sliding portions 18a and 33a is insufficient.

[0087] When the position identified on the characteristic curve CL is in the mixed lubrication region, the thickness of the lubricating layer of the flushing fluid is in the proper value range as described above, so that the cooling state of the sliding portions 18a and 33a can be estimated as a state in which the sliding portions 18a and 33a are properly cooled.

[0088] When the point identified on the characteristic curve CL is located in the fluid lubrication region, the thickness of the lubricating layer of the flushing fluid is relatively thick as described above, so that the cooling state of the sliding portions 18a and 33a can be estimated as a state in which the sealing target fluid easily leaks out at the sliding portions 18a and 33a.

[0089] In the present embodiment, the company estimates the cooling state of the sliding portions 18a and 33a based on the characteristic curve CL and the kinetic friction coefficient µ calculated based on the temperature difference ΔT, but the cooling state of the sliding portions 18a and 33a may also be estimated from the temperature difference ΔT.

[0090] In this case, when the temperature difference ΔT is relatively large, the heat generation at the sliding portions 18a and 33a due to frictional heat, etc. is increased, so that the cooling state of the sliding portions 18a and 33a can be roughly estimated as a state in which the amount of flushing fluid supplied to the sliding portions 18a and 33a is insufficient.

[0091] When the temperature difference ΔT is relatively small, the heat generation at the sliding portions 18a and 33a is reduced to a small amount, so that the cooling state of the sliding portions 18a and 33a can be roughly estimated as a state in which the sliding portions 18a and 33a are appropriately cooled by the flushing fluid.

[0092] The company can also estimate the cooling state of the sliding areas 18a and 33a using the kinetic friction coefficient µ, which is calculated based on the temperature difference ΔT. Since the kinetic friction coefficient µ is closely related to the cooling state of the sliding areas 18a and 33a, the cooling state of the sliding areas 18a and 33a can be estimated more accurately in this case than using the temperature difference ΔT. Beneficial effects

[0093] In the mechanical seal 1 according to the present embodiment, the temperature difference ΔT between the temperature T1 of the first purge fluid before cooling and the temperature T2 of the second purge fluid after cooling is detected by the temperature difference detection section 60. The cooling state of the sliding portions 18a and 33a of the rotary seal ring 18 and the stationary seal ring 33 can be roughly estimated using the detected temperature difference ΔT. Thus, the company can estimate the cooling state of the sliding portions 18a and 33a caused by the purge fluid without directly observing the sliding portions 18a and 33a of the rotary seal ring 18 and the stationary seal ring 33.

[0094] The temperature difference detection section 60 is the thermocouple 61 with the reference contacts 64 and the temperature measuring contact 65, wherein each reference contact 64 is positioned to be in contact with the first purge fluid and the temperature measuring contact 65 is positioned to be in contact with the second purge fluid.

[0095] Thus, the temperature difference between the reference contact 64 and the temperature measuring contact 65 of the thermocouple 61 is the temperature difference ΔT between the temperature T1 of the first purge fluid before cooling and the temperature T2 of the second purge fluid after cooling. Thus, the temperature difference detection section 60 can have a simple configuration by using the thermocouple 61.

[0096] The control unit 4 calculates the kinetic friction coefficient µ of the sliding portions 18a and 33a based on the temperature difference ΔT detected by the temperature difference detection portion 60. Since the kinetic friction coefficient µ is closely related to the cooling state of the sliding portions 18a and 33a, the company can more accurately estimate the cooling state of the sliding portions 18a and 33a by using the calculated kinetic friction coefficient µ.

[0097] Furthermore, the above equation (3) for calculating the kinetic friction coefficient µ takes into account the properties (density γ, etc.) of the flushing fluid and the operating conditions (thrust force P, average peripheral speed V, etc.) of the mechanical seal 1. Thus, the calculated kinetic friction coefficient µ is a numerical value that takes the differences in the flushing fluid and the operating conditions more into account than the temperature difference ΔT, so that it is easier to compare the cooling state of the sliding portions 18a and 33a under different conditions than from the temperature difference ΔT.

[0098] When estimating the cooling state of sliding areas 18a and 33a, the company uses the characteristic curve CL, which represents the behavior of the kinetic friction coefficient µ in relation to the operating parameter DP for the lubrication properties of sliding areas 18a and 33a. Using the characteristic curve CL, it is possible to estimate with high accuracy which of the three lubrication zones (boundary lubrication zone, mixed lubrication zone, and fluid lubrication zone) the sliding areas 18a and 33a are located in.

[0099] Accordingly, the company can more accurately estimate the cooling state of the sliding areas 18a and 33a based on the estimated lubrication area. Furthermore, it may be difficult to estimate in which of the mixed lubrication area and the fluid lubrication area the value of the kinetic friction coefficient µ calculated by the control unit 4 is located. In such a case, using the characteristic curve CL and the limit value of the operating parameter DP corresponding to the minimum value of the kinetic friction coefficient µ, it is easy to identify in which of the mixed lubrication area and the fluid lubrication area the calculated value of the kinetic friction coefficient µ is located. Second embodiment

[0100] Fig. 6 is a cross-sectional view of a main portion of a mechanical seal 1 according to a second embodiment of the present invention. Fig. 6, the mechanical seal 1 according to the present embodiment differs from that according to the first embodiment in the mounting structure for the thermocouple 61 in the stationary side unit 3. The stationary side unit 3 according to the present embodiment has an adjusting ring 56 arranged between the seal housing 31 and the housing 72.

[0101] The adjusting ring 56 is formed in a ring shape and is fixed together with the seal housing 31 by means of the screw 34 to the housing 72 (see Fig. 1). When attaching the adjusting ring 56 to the housing 72, an adjusting ring 56 is used that has a different size depending on the type of rotating machine 70. Accordingly, the mechanical seal 1 can be mounted on various rotating machines 70.

[0102] An inner peripheral surface 56a of the adjusting ring 56 is located radially outward from the sliding portions 18a and 33a. A seal 57 provides a (secondary) seal between the side surface on one side of the seal housing 31 in the axial direction and the side surface on the other side of the adjusting ring 56 in the axial direction. An O-ring 58 provides a (secondary) seal between the side surface on the other side of the adjusting ring 56 in the axial direction and the side surface on one side of the housing 72 in the axial direction.

[0103] The stationary side unit 3 according to the present embodiment does not have an adapter ring 50 (see Fig. 2). Furthermore, the annular groove 31d (see Fig. 2) communicating with each hole 31a is not formed on the inner periphery of the seal housing 31. Thus, each hole 31a (the first flow passage 31b, the auxiliary hole 31c) of the seal housing 31 directly communicates with the inner area A.

[0104] The thermocouple 61 according to the present embodiment is attached to the adjusting ring 56. Specifically, the first conductor 62 and the second conductor 63 of the thermocouple 61 are fixed to the inner peripheral surface 56a of the adjusting ring 56 at a position near the additional hole 31c. For clarity, Fig. 6, the second conductor 63 is shown as being displaced radially inward from the inner peripheral surface 56a of the adjusting ring 56.

[0105] The first conductor 62 and the second conductor 63 are positioned to intersect the virtual extension line X of the sliding portions 18a and 33a in the axial direction. Accordingly, the reference contacts 64 of the thermocouple 61 are positioned to be in contact with the first purge fluid, and the temperature measuring contact 65 of the thermocouple 61 is positioned to be in contact with the second purge fluid.

[0106] Each reference contact 64 of the thermocouple 61 is connected to the corresponding conductive connecting wire 5 or 6 in a state where it protrudes from the adjusting ring 56 on the other side in the axial direction. Each conductive connecting wire 5 or 6 extends from the reference contact 64 of the thermocouple 61 through the auxiliary hole 31c and extends through the blocking member 40 to the radially outer side of the seal housing (outside the area B) (see Fig. 1).

[0107] The other components according to the present embodiment are the same as those in the first embodiment and are therefore denoted by the same reference numerals, and their descriptions will be omitted. The mechanical seal 1 according to the present embodiment achieves the same effects as those in the first embodiment. Other

[0108] In the thermocouple 61 according to each of the embodiments described above, each reference contact 64 is positioned to be in contact with the first purge fluid, and the temperature measuring contact 65 is positioned to be in contact with the second purge fluid, but each reference contact 64 may also be positioned to be in contact with the second purge fluid, and the temperature measuring contact 65 may be positioned to be in contact with the first purge fluid.

[0109] The temperature difference detection section 60 according to each embodiment described above is formed of the thermocouple 61, but is not limited thereto. For example, the temperature difference detection section 60 may also include a pair of temperature sensors that detect the temperature T1 of the first purge fluid and the temperature T2 of the second purge fluid, respectively.

[0110] In particular, in a flushing operation in which a self-flushing line and a backflushing line are included in the stationary side unit 3, the temperature difference detection section 60 may include a temperature sensor arranged in the self-flushing line and detecting the temperature T1 of the first flushing fluid in this line, and a temperature sensor arranged in the backflushing line and detecting the temperature T2 of the second flushing fluid in this line.

[0111] The temperature difference detection section 60 according to each of the above-described embodiments is mounted on the adapter ring 50 or the adjustment ring 56, but it may also be mounted on another member of the stationary-side unit 3. In each of the above-described embodiments, each conductive connection wire 5 or 6 passes through the auxiliary hole 31c of the seal housing 31. However, a special hole may be formed in the seal housing 31 through which each conductive connection wire 5 or 6 passes. Alternatively, each conductive connection wire 5 or 6 may pass through a hole formed in advance in the casing 72 of the rotating machine 70 for water injection.

[0112] In each of the above-described embodiments, the kinetic friction coefficient µ is automatically calculated by the control unit 4, but the kinetic friction coefficient µ may also be manually calculated by the company or the like. The mechanical seal 1 according to each above-described embodiment is a rotary-type mechanical seal, but is not limited thereto. For example, the mechanical seal 1 may also be a stationary mechanical seal of the dual seal type (tandem seal, double seal), single-coil type, or bellows type, or may also be a thermosiphon mechanical seal without actively circulating a flushing fluid, such as a double seal with a pressure vessel.

[0113] The embodiments disclosed herein are merely illustrative and not restrictive in all aspects. The scope of the present invention is defined by the scope of the claims, not by the meanings described above, and is intended to include meanings corresponding to the scope of the claims and all modifications within the scope. List of reference symbols 1 Mechanical seal 2 rotating page unit 3 Stationary side unit 4 Control unit 18 Rotatable sealing ring 18a, 33a gliding area 33 Stationary sealing ring 60 temperature difference detection range 61 thermocouple 64 Reference Contact 65 Temperature measuring contact 71 Rotating shaft 72 housings A Interior CL characteristic curve DP operating parameters (dimensionless coefficient) T1 temperature T2 temperature ΔT temperature difference µ Coefficient of kinetic friction QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2021-60 079 A

[0003]

Claims

[1] A mechanical seal comprising: a rotary side unit arranged on a rotary shaft so as to be rotatable therewith, and having a rotary seal ring; and a stationary side unit arranged on a housing surrounding the rotary shaft and having a stationary seal ring on which the rotary seal ring slides to seal a sealing target fluid in an interior region in the housing, wherein sliding portions of the rotary seal ring and the stationary seal ring are cooled by a flushing fluid, the mechanical seal comprising: a temperature difference detection section arranged in the stationary side unit and configured to detect a temperature difference between a temperature of a first purge fluid, which is the purge fluid before cooling the sliding sections, and a temperature of a second purge fluid, which is the purge fluid after cooling the sliding sections. [2] A mechanical seal according to claim 1, further comprising a control unit configured to calculate a coefficient of kinetic friction of the sliding portions based on the temperature difference. [3] Mechanical seal according to claim 1 or 2, wherein the temperature difference detection section is a thermocouple with a reference contact and a temperature measuring contact, the reference contact is positioned so that it is in contact with one of the first rinsing fluid or the second rinsing fluid, and the temperature measuring contact is positioned so that it is in contact with the other of the first flushing fluid and the second flushing fluid. [4] A cooling state estimation method for estimating a cooling state of sliding portions of a rotary seal ring and a stationary seal ring caused by a flushing fluid for a mechanical seal, comprising: a rotary side unit arranged on a rotary shaft so as to be rotatable therewith, and having the rotary seal ring; and a stationary side unit arranged on a housing surrounding the rotary shaft and having the stationary seal ring on which the rotary seal ring slides to seal a sealing target fluid in an interior region in the housing, wherein the cooling state estimation method comprises: a step of detecting a temperature difference between a temperature of the rinsing fluid before cooling the sliding portions and a temperature of the rinsing fluid after cooling the sliding portions by a temperature difference detecting portion. [5] The cooling state estimation method according to claim 4, further comprising a step of calculating a coefficient of kinetic friction of the sliding portions based on the detected temperature difference. [6] The cooling state estimation method according to claim 5, further comprising a step of estimating the cooling state of the sliding portions based on the calculated kinetic friction coefficient and a characteristic curve representing the behavior of the kinetic friction coefficient with respect to a dimensionless coefficient for lubricating properties of the sliding portions.

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