Mechanical seal and method for estimating cooling status

Abstract

The present invention provides a mechanical seal and a method for estimating the cooling status of a sliding ring by a flushing fluid, without directly observing the sliding portion between a rotating sealing ring and a stationary sealing ring. [Solution] The mechanical seal 1 comprises a rotating side unit 2 having a rotating sealing ring 18 and a stationary side unit 3 having a stationary sealing ring 33. The sliding portions 18a and 33a between the rotating sealing ring 18 and the stationary sealing ring 33 are cooled by a flushing fluid. A temperature difference detection unit 60 is provided in the stationary side unit 3 to detect the temperature difference ΔT between the temperature T1 of the flushing fluid before cooling the sliding portions 18a and 33a and the temperature T2 of the flushing fluid after cooling the sliding portions 18a and 33a.

Description

Technical Field

[0001] The present invention relates to a mechanical seal and a method for estimating a cooling condition.

Background Art

[0002] As a device for sealing a fluid to be sealed inside a rotating machine, for example, a mechanical seal shown in Patent Document 1 is known. The mechanical seal of Patent Document 1 includes a rotating seal ring (rotating ring) provided on a rotating shaft of a rotating machine and sliding with respect to a stationary seal ring, and a stationary seal ring (fixed ring) provided on a housing of the rotating machine. The sliding portion between the rotating seal ring and the stationary seal ring is cooled and lubricated by a flushing fluid.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the mechanical seal of Patent Document 1, in order to grasp whether the sliding portion between the rotating seal ring and the stationary seal ring is appropriately cooled by the flushing fluid, it is necessary to disassemble the mechanical seal and directly observe the sliding portion visually. Therefore, it has been difficult to grasp the cooling condition of the sliding portion during the operation of the mechanical seal.

[0005] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a mechanical seal and a method for estimating a cooling condition that can estimate the cooling condition of the sliding portion by a flushing fluid without directly observing the sliding portion between a rotating seal ring and a stationary seal ring.

Means for Solving the Problems

[0006] (1) The present disclosure provides a mechanical seal comprising: a rotating side unit provided integrally rotatably on a rotating shaft and having a rotating sealing ring; and a stationary side unit provided in a casing surrounding the rotating shaft and having a stationary sealing ring on which the rotating sealing ring slides to seal a fluid to be sealed in an internal region within the casing, wherein the sliding portion between the rotating sealing ring and the stationary sealing ring is cooled by a flushing fluid, and the stationary side unit is provided with a temperature difference detection unit that detects the temperature difference between the temperature of a first flushing fluid, which is the flushing fluid, before cooling the sliding portion, and the temperature of a second flushing fluid, which is the flushing fluid, after cooling the sliding portion.

[0007] According to the mechanical seal of this disclosure, 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 a temperature difference detection unit. If the temperature difference is relatively large, it can be roughly estimated that heat generation in the sliding part is increasing due to frictional heat, etc., and that the amount of flushing fluid supplied to the sliding part is insufficient. Conversely, if the temperature difference is relatively small, it can be roughly estimated that heat generation in the sliding part is kept low, and that the cooling of the sliding part is being properly performed by the flushing fluid. Therefore, by detecting the temperature difference with the temperature difference detection unit, the cooling status of the sliding part by the flushing fluid can be estimated without directly observing the sliding part between the rotating sealing ring and the stationary sealing ring.

[0008] (2) The mechanical seal in (1) preferably further comprises a control unit that calculates the coefficient of dynamic friction of the sliding portion based on the temperature difference. In this case, the dynamic friction coefficient calculated by the control unit is closely related to the cooling state of the sliding part, and therefore, the cooling state of the sliding part between the rotating sealing ring and the stationary sealing ring by the flushing fluid can be estimated more accurately from the dynamic friction coefficient.

[0009] (3) In the mechanical seal of (1) or (2) above, the temperature difference detection unit is preferably a thermocouple having a reference junction and a temperature measuring junction, wherein the reference junction is arranged to be in contact with one of the first flushing fluid and the second flushing fluid, and the temperature measuring junction is arranged to be in contact with the other of the first flushing fluid and the second flushing fluid. In this case, the temperature difference between the thermocouple's reference junction and the temperature-measuring junction becomes the temperature difference between the temperature of the first flushing fluid before cooling and the temperature of the second flushing fluid after cooling. Therefore, using a thermocouple allows for a simpler configuration of the temperature difference detection unit.

[0010] (4) The present disclosure relates to a mechanical seal comprising a rotating side unit provided integrally rotatably on a rotating shaft and having a rotating sealing ring, and a stationary side unit provided in a casing surrounding the rotating shaft and having a stationary sealing ring on which the rotating sealing ring slides to seal a fluid to be sealed in an internal region within the casing, and a method for estimating the cooling status of the sliding portion between the rotating sealing ring and the stationary sealing ring by a flushing fluid, the method for estimating the cooling status comprising the step of detecting the temperature difference between the temperature of the flushing fluid before cooling the sliding portion and the temperature of the flushing fluid after cooling the sliding portion using a temperature difference detection unit.

[0011] According to the cooling status estimation method of this disclosure, the temperature difference between the temperature of the flushing fluid before cooling and the temperature of the flushing fluid after cooling is detected by a temperature difference detection unit. If the temperature difference is relatively large, it can be roughly estimated that heat generation in the sliding part is increasing due to frictional heat, etc., and that the cooling status of the sliding part is such that the amount of flushing fluid supplied to the sliding part is insufficient. If the temperature difference is relatively small, it can be roughly estimated that heat generation in the sliding part is kept low, and that the cooling status of the sliding part is such that the sliding part is being properly cooled by the flushing fluid. Therefore, by detecting the temperature difference with the temperature difference detection unit, the cooling status of the sliding part by the flushing fluid can be estimated without directly observing the sliding part between the rotating sealing ring and the stationary sealing ring.

[0012] (5) The cooling state estimation method of (4) preferably further includes the step of calculating the coefficient of dynamic friction of the sliding part based on the detected temperature difference. In this case, since the coefficient of dynamic friction is closely related to the cooling state of the sliding part, the cooling state of the sliding part between the rotating sealing ring and the stationary sealing ring by the flushing fluid can be estimated more accurately from the coefficient of dynamic friction.

[0013] (6) The cooling state estimation method of (5) preferably further includes the step of estimating the cooling state of the sliding part based on the calculated dynamic friction coefficient and a characteristic curve showing the behavior of the dynamic friction coefficient with respect to a dimensionless coefficient for the lubrication characteristics of the sliding part. In this case, by using a characteristic curve that shows the behavior of the coefficient of dynamic friction with respect to a dimensionless coefficient for the lubrication characteristics of the sliding part, it is possible to estimate with high accuracy what lubrication region the sliding part is in. As a result, based on the estimated lubrication region, the cooling status of the sliding part between the rotating sealing ring and the stationary sealing ring by the flushing fluid can be estimated more accurately. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to estimate the cooling state of the sliding portion between the rotating seal ring and the stationary seal ring by a flushing fluid without directly observing the sliding portion.

Brief Description of the Drawings

[0015] [Figure 1] It is a cross-sectional view of the mechanical seal according to the first embodiment of the present disclosure. [Figure 2] It is an enlarged cross-sectional view showing the adapter ring and its surroundings. [Figure 3] It is a schematic configuration diagram of a thermocouple. [Figure 4] It is a flowchart showing a method for estimating the cooling state of the sliding portion between the rotating seal ring and the stationary seal ring by a flushing fluid. [Figure 5] It is a graph showing characteristic curves. [Figure 6] It is a cross-sectional view showing the main part of the mechanical seal according to the second embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0016] Next, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that at least a part of the embodiments described below may be arbitrarily combined. [First Embodiment] [Overall Configuration] FIG. 1 is a cross-sectional view of a mechanical seal 1 according to the first embodiment of the present disclosure. In FIG. 1, the mechanical seal 1 is used for a rotating device 70 such as a pump and seals a fluid to be sealed inside the rotating device 70. The mechanical seal 1 is disposed along the axial direction of the rotating shaft 71 (hereinafter simply referred to as the "axial direction") between the rotating shaft 71 of the rotating device 70 and a casing 72 surrounding the rotating shaft 71.

[0017] The mechanical seal 1 of the present embodiment includes a rotating-side unit 2 provided so as to be integrally rotatable with a rotating shaft 71 and a stationary-side unit 3 provided in a casing 72. In this specification, for the sake of convenience, the right side in FIG. 1 is referred to as one axial side, and the left side in FIG. 1 is referred to as the other axial side (the same applies to FIGS. 2 and 6).

[0018] <Rotating-side unit> The rotating-side unit 2 includes a sleeve 11, a stopper ring 12, a first retainer 13, a drive pin 14, a drive collar 15, a spring 16, a second retainer 17, and a rotating seal ring 18.

[0019] The sleeve 11 is formed in a cylindrical shape and is fitted on the outer periphery of the rotating shaft 71. A stopper ring 12 is fitted on the outer periphery of the sleeve 11 on the other axial side. A plurality of sets of screws 19 are tightened in the radial direction in the circumferential direction of the stopper ring 12. Thereby, the sleeve 11 is fixed to the rotating shaft 71. The space between the inner peripheral surface of the sleeve 11 on one axial side and the outer peripheral surface of the rotating shaft 71 is sealed (secondary seal) by an O-ring 20.

[0020] The first retainer 13 is a spring retainer. The first retainer 13 is formed in an annular shape and is fitted on the outer periphery of the sleeve 11 on one axial side. A plurality (only one is shown in FIG. 1) of sets of screws 21 are tightened in the radial direction in the circumferential direction of the first retainer 13. Thereby, the first retainer 13 is fixed to the sleeve 11. A plurality (only one is shown in FIG. 1) of drive pins 14 penetrate axially through the first retainer 13 at intervals in the circumferential direction. The drive pin 14 is held so as to be axially movable with respect to the first retainer 13.

[0021] The drive collar 15 is positioned at a distance from the first retainer 13 on the other axial side. The drive collar 15 is annular in shape and is fitted to the outer circumferential surface of the sleeve 11 so as to be axially movable. The other axial end of the drive pin 14 is fixed (screwed) to the drive collar 15. As a result, the drive collar 15 is held axially movable relative to the first retainer 13 via the drive pin 14, and its relative rotation with respect to the first retainer 13 is restricted.

[0022] Multiple springs 16 (only one is shown in Figure 1) are provided between the drive collar 15 and the first retainer 13 at circumferential intervals. The springs 16 bias the drive collar 15 axially toward the other side relative to the first retainer 13.

[0023] The second retainer 17 is positioned adjacent to the other axial side of the drive collar 15. The second retainer 17 is annular in shape and is fitted axially movably to the outer circumferential surface of the sleeve 11. One axial end of the second retainer 17 is fixed to the drive collar 15. This restricts the relative rotation of the second retainer 17 with respect to the drive collar 15 while holding it axially movably relative to the sleeve 11 together with the drive collar 15. The space between the inner circumferential surface of the second retainer 17 and the outer circumferential surface of the sleeve 11 is sealed (secondary seal) by an O-ring 22.

[0024] The rotating sealing ring 18 is formed in an annular shape and is fixed (shrink-fitted) to the other axial end of the second retainer 17. A sealing surface 18a is formed on the other axial end face of the rotating sealing ring 18 (see also Figure 2). The rotating sealing ring 18 is biased axially to the other side by a spring 16 via the drive collar 15 and the second retainer 17.

[0025] <Stationary Unit> The stationary unit 3 comprises a seal case 31, a bush 32, a stationary sealing ring 33, and an adapter ring 50. The seal case 31 is formed in a cylindrical shape. The seal case 31 surrounds the rotating shaft 71 and is fixed to the casing 72 in order to separate the internal area A and the external area B of the rotating equipment 70.

[0026] In this embodiment, the radially outer portion of the seal case 31 is fixed to the casing 72 by bolts 34, with the seal case 31 in contact with the other axial side surface of the casing 72. The space between the axial side surface of the seal case 31 and the other axial side surface of the casing 72 is sealed (secondary seal) by an O-ring 35.

[0027] A bush 32 is attached to the inner circumference of the other axial side of the seal case 31. The bush 32 is formed in an annular shape and forms a clearance seal between it and the outer circumferential surface of the sleeve 11. An annular regulating member 36 is fixed to the end face of the other axial side of the seal case 31.

[0028] The regulating member 36 is in contact with the other axial end face of the bush 32. This prevents the bush 32 from coming out in the other axial direction relative to the seal case 31. The regulating member 36 has an engaging pin 36a that engages with the bush 32. This prevents the regulating member 36 from rotating the bush 32 together with the sleeve 11.

[0029] The stationary sealing ring 33 is formed in an annular shape and is fitted and fixed to the inner circumferential surface of the seal case 31. The space between the outer circumferential surface of the stationary sealing ring 33 and the inner circumferential surface of the seal case 31 is sealed (secondary seal) by an O-ring 37. A sealing surface 33a is formed on one axial end face of the stationary sealing ring 33 (see also Figure 2).

[0030] The sealing surface 33a of the stationary sealing ring 33 slides against the sealing surface 18a of the rotating sealing ring 18. This seals the fluid to be sealed in the internal region A of the machine. The relative rotation of the stationary sealing ring 33 with respect to the rotating sealing ring 18 is restricted by a regulating pin 38 fixed to the inner circumference of the seal case 31.

[0031] The adapter ring 50 is positioned radially outward from the sliding portion (sealing surfaces 18a, 33a) between the rotating sealing ring 18 and the stationary sealing ring 33 in the internal region A. Hereinafter, the sliding portion between the rotating sealing ring 18 and the stationary sealing ring 33 will also be referred to as the sliding portion 18a, 33a. The adapter ring 50 is formed in a cylindrical shape and is detachably attached to the seal case 31.

[0032] Figure 2 is an enlarged cross-sectional view showing the adapter ring 50 and its surroundings. In Figures 1 and 2, one axial side of the outer peripheral surface 50a of the adapter ring 50 is fitted to the inner peripheral surface of the seal case 31. The other axial end surface 50b of the adapter ring 50 abuts against a stepped surface 31e that extends radially on the inner circumference of the seal case 31.

[0033] The axial end face 50c of the adapter ring 50 is in contact with the snap ring 39 attached to the seal case 31. As a result, the adapter ring 50 is held between the stepped surface 31e and the snap ring 39, preventing it from coming off the seal case 31.

[0034] The snap ring 39 is detachably fitted into an annular groove 31f formed on the inner circumference of the seal case 31. Therefore, by removing the snap ring 39 from the groove 31f, the adapter ring 50 can be removed from the seal case 31.

[0035] <Flow path of flushing fluid> In Figure 1, the stationary unit 3 has a flow path that supplies flushing fluid from the external region B to the internal region A. The flushing fluid cools and lubricates the sliding portions 18a and 33a between the rotating sealing ring 18 and the stationary sealing ring 33. In this embodiment, the fluid to be sealed is used as the flushing fluid.

[0036] In this specification, the flushing fluid before cooling the sliding parts 18a and 33a is referred to as the first flushing fluid. The flushing fluid after cooling the sliding parts 18a and 33a is referred to as the second flushing fluid. A flow path for the first flushing fluid is formed in the stationary unit 3. The flow path for the first flushing fluid will be described below.

[0037] Multiple holes 31a (two in Figure 1) are formed on one axial side of the seal case 31, spaced apart in the circumferential direction. Each hole 31a is formed to penetrate the seal case 31 radially. An annular groove 31d (see also Figure 2) is formed on the inner circumference of the seal case 31, communicating with each hole 31a. Each hole 31a can be used as a first flow path 31b for supplying the first flushing fluid from the external region B to the internal region A.

[0038] Multiple holes 31a that can be used as the first flow path 31b are formed in the circumferential direction of the seal case 31 because the circumferential position where the piping through which the first flushing fluid flows is connected to the seal case 31 differs depending on the type of rotating equipment 70, etc. In this embodiment, the holes 31a formed on the lower side of Figure 1 are used as the first flow path 31b. Therefore, a first flow path 31b for supplying the first flushing fluid from the external region B to the internal region A is formed at a predetermined location in the circumferential direction of the seal case 31 (the lower side of Figure 1).

[0039] Other holes 31a that are not used as the first flow path 31b are hereinafter referred to as spare holes 31c. The radially outer opening of the spare holes 31c is closed by a closing member 40. The closing member 40 has, for example, a first threaded portion 41 that is screwed into the spare hole 31c and a second threaded portion 42 that is screwed onto the head of the first threaded portion 41. The closing member 40 prevents the first flushing fluid that has flowed into the spare hole 31c from the annular groove 31d from leaking to the outside.

[0040] In Figure 2, the adapter ring 50 has a second flow path 51 that communicates with a plurality of holes 31a (first flow path 31b and spare holes 31c) of the seal case 31. The second flow path 51 is a flow path for supplying the first flushing fluid from the first flow path 31b to multiple locations in the circumferential direction of the sliding parts 18a and 33a. The second flow path 51 has an annular flow path 52 and a plurality of supply flow paths 53.

[0041] The annular channel 52 is formed on the outer circumference of the adapter ring 50 at a position opposite to the annular groove 31d of the seal case 31. In this embodiment, the annular channel 52 consists of an annular notched groove formed on the outer circumference of the adapter ring 50. The axial width of the annular channel 52 is the same as the groove width of the annular groove 31d of the seal case 31. As a result, the first flushing fluid from the first channel 31b flows in the circumferential direction within the channel consisting of the annular groove 31d and the annular channel 52.

[0042] In Figures 1 and 2, the multiple supply channels 53 are channels that supply the first flushing fluid from the annular channel 52 to the internal region A of the machine. The supply channels 53 are formed by passing through the adapter ring 50 radially from multiple locations in the circumferential direction on the bottom surface of the annular channel 52. As a result, the first flushing fluid is supplied to the internal region A from the multiple supply channels 53, so that the sliding parts 18a and 33a can be cooled and lubricated evenly over the entire circumferential direction.

[0043] Each supply channel 53 is formed such that its radially inner opening 53a is located on the other axial side (outside the machine region B side) of the sliding portions 18a and 33a. As a result, in the machine region A, the first flushing fluid and the second flushing fluid are generally separated on both sides of the extension of the imaginary line X of the sliding portions 18a and 33a. Specifically, in the machine region A, the first flushing fluid occupies the region on the other axial side of the extension of the imaginary line X, and the second flushing fluid occupies the region on one axial side of the extension of the imaginary line X.

[0044] <Temperature difference detection unit> The mechanical seal 1 further comprises a temperature difference detection unit 60 and a control unit 4, both located on the stationary unit 3. The temperature difference detection unit 60 detects the temperature difference ΔT between the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid. In this embodiment, the temperature difference detection unit 60 consists of a single thermocouple 61. The thermocouple 61 in this embodiment is attached to the adapter ring 50.

[0045] Figure 3 is a schematic diagram of the thermocouple 61. In Figures 2 and 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 of, for example, an alloy mainly composed of nickel and chromium. The second conductor 63 is made of, for example, an alloy mainly composed of nickel and aluminum.

[0046] The first conductor 62 and the second conductor 63 are inserted into mounting holes 54 formed radially through the adapter ring 50. The mounting holes 54 are formed in the adapter ring 50 at a position corresponding to the pre-hole 31c. Furthermore, the mounting holes 54 are formed to incline from one axial side to the other axial side as they move from the outer circumferential surface of the adapter ring 50 toward the inner circumferential surface. The radially inner opening 54a of the mounting hole 54 is located in the machine region A in the region on one axial side of the extended virtual line X (the region occupied by the second flushing fluid).

[0047] The mounting hole 54 is sealed by a sealing member (not shown) with the first conductor 62 and the second conductor 63 passing through it. This sealing member prevents the first flushing fluid flowing through the annular channel 52 from flowing through the mounting hole 54 into the area of ​​the internal region A occupied by the second flushing fluid.

[0048] One end of the first conductor 62 and one end of the second conductor 63 are joined to each other, protruding from the opening 54a of the mounting hole 54 into the region on one axial side of the internal region A. This joint is the temperature sensing junction 65 of the thermocouple 61. Therefore, in this embodiment, the temperature sensing junction 65 of the thermocouple 61 is positioned to be in contact with the second flushing fluid.

[0049] The other ends of the first conductor 62 and the second conductor 63 protrude radially outward from the mounting hole 54 and are positioned in the annular channel 52 through which the first flushing fluid flows, separated from each other. The other ends of the first conductor 62 and the second conductor 63 positioned in the annular channel 52 serve as the reference junctions 64 of the thermocouple 61, respectively. Therefore, in this embodiment, the reference junctions 64 of the thermocouple 61 are positioned in contact with the first flushing fluid in the annular channel 52.

[0050] The other end of the first conductor 62 is connected by welding or the like to a connecting wire 5 made of a different metal 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 connecting wire 6 made of a different metal material than the first conductor 62 and the second conductor 63. Each connecting wire 5 and 6 is made of, for example, copper.

[0051] As shown in Figures 1 and 2, each connecting wire 5 and 6 extends from the reference junction 64 of the thermocouple 61, through the annular channel 52 and the pre-hole 31c, through the closing member 40, to the radially outer side (outside region B) of the seal case 31. The ends of each connecting wire 5 and 6 in the outside region B are connected to the control unit 4.

[0052] With the above configuration, the thermocouple 61 outputs a thermoelectric voltage corresponding to the temperature difference ΔT between the temperature T1 of the reference junction 64 (first flushing fluid) and the temperature T2 of the temperature measuring junction 65 (second flushing fluid) to the control unit 4 via connecting wires 5 and 6. 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, it outputs a signal (thermoelectric voltage) corresponding to that temperature difference ΔT to the control unit 4. The thermocouple 61 detects the temperature difference ΔT at predetermined intervals and outputs the signal to the control unit 4.

[0053] <Department Head> The control unit 4 is located in the external area B. The control unit 4 is configured with a computer that includes a CPU. Each function of the control unit 4 is performed by the CPU executing a control program stored in the computer's storage device. The control unit 4 calculates the dynamic friction coefficient μ of the sliding parts 18a and 33a based on the thermoelectric voltage input from the thermocouple 61 at predetermined intervals. The specific calculation method will be described below.

[0054] First, the control unit 4 extracts the temperature difference ΔT corresponding to the thermoelectric voltage input from the thermocouple 61 from a table in which thermoelectric voltage and temperature difference ΔT are registered in association. Alternatively, the control unit 4 may calculate the temperature difference ΔT from the thermoelectric voltage input from the thermocouple 61 using a predetermined calculation formula.

[0055] Next, the control unit 4 substitutes the extracted temperature difference ΔT into equation (3), which is derived from equations (1) and (2) below, to calculate the dynamic friction coefficient μ. Equation (1) is an equation that represents the frictional heat quantity Q [kJ / min] of the sliding parts 18a and 33a. Equation (2) is an equation that represents the flow rate Wf [L / min] of the flushing fluid required to cool the sliding parts 18a and 33a. Q=(μ·P·V)×60÷1000 ···(1) Wf = Q ÷ (Cp·γ·ΔT) ···(2) μ=Wf×(Cp・γ・ΔT)÷(P・V)×1000÷60 (3)

[0056] Here, P is the apparent thrust [N] acting on the sliding parts 18a and 33a. V is the average peripheral speed [m / s] of the sealing surface 18a of the rotating 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. P, V, Cp, and γ are all known values.

[0057] <Method for estimating the cooling status of sliding parts> Figure 4 is a flowchart showing a method for estimating the cooling status of the sliding portions 18a and 33a between the rotating sealing ring 18 and the stationary sealing ring 33 using a flushing fluid. The method for estimating the cooling status will be described below with reference to Figure 4.

[0058] First, the temperature difference ΔT between the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid is detected by the temperature difference detection unit 60 (step ST1). As described above, the temperature difference detection unit 60 outputs a thermoelectric voltage corresponding to the temperature difference ΔT to the control unit 4.

[0059] Next, the control unit 4 calculates the coefficient of dynamic friction μ of the sliding parts 18a and 33a based on the temperature difference ΔT (step ST2). The specific method for calculating the coefficient of dynamic friction μ by the control unit 4 is as described above.

[0060] Next, the cooling status of the sliding parts 18a and 33a is estimated based on the calculated dynamic friction coefficient μ and the characteristic curve CL (step ST3). The characteristic curve CL is a curve that shows the behavior of the dynamic friction coefficient μ with respect to a dimensionless coefficient for the lubrication characteristics of the sliding parts 18a and 33a. The estimation of the cooling status of the sliding parts 18a and 33a is performed, for example, by a business operator that performs maintenance and inspection of the mechanical seal 1.

[0061] As a dimensionless coefficient, for example, the duty cycle parameter DP is used. The duty cycle parameter DP represents the characteristics (lubrication characteristics) of the lubricating film of the flushing fluid formed on the sliding parts 18a and 33a. The duty cycle parameter DP is calculated from the following equation (4). DP = (η × ω × b) ÷ W ... (4)

[0062] Here, η is the viscosity of the flushing fluid [Pa·s]. ω is the peripheral speed [m / s] of the sealing surface 18a of the rotating sealing ring 18. b is the radial sliding width [m] of the sealing surface 18a. W is the pressing load [N] on the rotating sealing ring 18 by the spring 16 (see Figure 1) and the fluid being sealed.

[0063] The characteristic curve CL of this embodiment shows the behavior of the dynamic friction coefficient μ with respect to the duty cycle parameter DP. The characteristic curve CL is created in advance by testing the static load capacity of the mechanical seal 1 while varying the duty cycle parameter DP. The characteristic curve CL will be different depending on the type of flushing fluid, etc.

[0064] Figure 5 is a graph showing the characteristic curve CL created by the above tests. In this graph, the vertical axis represents the coefficient of dynamic friction μ, and the horizontal axis represents the duty cycle parameter DP. As shown in Figure 5, the value of the coefficient of dynamic friction μ of the sliding parts 18a and 33a changes roughly along the characteristic curve CL depending on the value of the duty cycle parameter DP. As the value of the coefficient of dynamic friction μ changes in this way, the state of the lubricating film of the flushing fluid formed on the sliding parts 18a and 33a changes.

[0065] As shown in Figure 5, the state of the lubricating film of the flushing fluid changes to three regions depending on the value of the duty parameter DP. Specifically, as the value of the duty parameter DP increases, the state of the lubricating film of the flushing fluid changes in the following order: boundary lubrication region, mixed lubrication region, and fluid lubrication region.

[0066] In the boundary lubrication region, the coefficient of dynamic friction μ becomes relatively large, and the thickness of the flushing fluid lubrication film becomes relatively thin. As a result, in the boundary lubrication region, the amount of flushing fluid supplied to the sliding parts 18a and 33a is insufficient, making it easier for the sealing surfaces 18a and 33a to come into direct contact with each other, and tending to increase wear. In the mixed lubrication region, the coefficient of dynamic friction μ is within the appropriate range, and the thickness of the flushing fluid lubrication film is also within the appropriate range. In the fluid lubrication region, the coefficient of dynamic friction μ becomes relatively small, and the thickness of the flushing fluid lubrication film becomes relatively thick. As a result, the sealed fluid is more likely to leak from the sliding parts 18a and 33a.

[0067] When estimating the cooling status of the sliding parts 18a and 33a from the characteristic curve CL in Figure 5, the operator first identifies where the calculated value of the dynamic friction coefficient μ by the control unit 4 is located on the characteristic curve CL. The characteristic curve CL has a roughly V-shape, with the position where the dynamic friction coefficient μ is at its minimum (near the boundary between the mixed lubrication region and the fluid lubrication region) being the valley. Therefore, the calculated value of the dynamic friction coefficient μ may be the same on the characteristic curve CL in the mixed lubrication region and on the characteristic curve CL in the fluid lubrication region.

[0068] In that case, the operator calculates the value of the duty parameter DP corresponding to the flushing fluid being used using equation (4) above. The operator then determines where the calculated value of the kinetic friction coefficient μ is located on the characteristic curve CL, based on whether the calculated value of the duty parameter DP is greater than or less than the value of the duty parameter DP corresponding to the minimum value of the kinetic friction coefficient μ (boundary value).

[0069] Specifically, the operator can determine that if the calculated value of the duty parameter DP is greater than the boundary value, the calculated value of the dynamic friction coefficient μ lies on the characteristic curve CL of the fluid lubrication region. Furthermore, the operator can determine that if the calculated value of the duty parameter DP is smaller than the boundary value, the calculated value of the dynamic friction coefficient μ lies on the characteristic curve CL of the mixed lubrication region. Note that the boundary value of the duty parameter DP is a known value that is approximately constant depending on the type of flushing fluid, etc.

[0070] Next, the operator checks which region—the boundary lubrication region, the mixed lubrication region, or the fluid lubrication region—the location identified on the characteristic curve CL falls into in the graph of Figure 5. The operator can then estimate the cooling status of the sliding parts 18a and 33a based on the region that includes the location identified on the characteristic curve CL.

[0071] Specifically, if the position identified on the characteristic curve CL is included in the boundary lubrication region, the cooling condition of the sliding parts 18a and 33a can be estimated to be such that, as described above, the thickness of the lubricating film of the flushing fluid is relatively thin, and the supply of flushing fluid to the sliding parts 18a and 33a is insufficient.

[0072] Furthermore, if the position identified on the characteristic curve CL is included in the mixed lubrication region, then, as described above, the thickness of the lubricating film of the flushing fluid is within the appropriate range. Therefore, it can be estimated that the cooling of the sliding parts 18a and 33a is being performed appropriately.

[0073] Furthermore, if a point on the identified characteristic curve CL is included in the fluid lubrication region, as described above, the thickness of the lubricating film of the flushing fluid is relatively thick, and it can be estimated that the cooling conditions of the sliding parts 18a and 33a are such that the sealed fluid is prone to leakage at the sliding parts 18a and 33a.

[0074] In this embodiment, the operator estimates the cooling status of the sliding parts 18a and 33a based on the dynamic friction coefficient μ calculated based on the temperature difference ΔT and the characteristic curve CL. However, the cooling status of the sliding parts 18a and 33a may also be estimated from the temperature difference ΔT. In that case, if the temperature difference ΔT is relatively large, it can be roughly estimated that the heat generation in the sliding parts 18a and 33a is increasing due to frictional heat, etc., and the cooling status of the sliding parts 18a and 33a is that the amount of flushing fluid supplied to the sliding parts 18a and 33a is insufficient. On the other hand, if the temperature difference ΔT is relatively small, it can be roughly estimated that the heat generation in the sliding parts 18a and 33a is kept low, and the cooling status of the sliding parts 18a and 33a is that the cooling of the sliding parts 18a and 33a is being properly carried out by the flushing fluid.

[0075] Alternatively, the operator may estimate the cooling status of the sliding parts 18a and 33a from the dynamic friction coefficient μ calculated based on the temperature difference ΔT. In this case, since the dynamic friction coefficient μ is closely related to the cooling status of the sliding parts 18a and 33a, it is possible to estimate the cooling status of the sliding parts 18a and 33a more accurately than with respect to the temperature difference ΔT.

[0076] <Effects and Effects> According to the mechanical seal 1 of this embodiment, the temperature difference ΔT between the temperature T1 of the first flushing fluid before cooling and the temperature T2 of the second flushing fluid after cooling is detected by the temperature difference detection unit 60. Based on this detected temperature difference ΔT, the cooling status of the sliding portions 18a and 33a between the rotating sealing ring 18 and the stationary sealing ring 33 can be roughly estimated. Therefore, the operator can estimate the cooling status of the sliding portions 18a and 33a by the flushing fluid without directly observing the sliding portions 18a and 33a between the rotating sealing ring 18 and the stationary sealing ring 33.

[0077] The temperature difference detection unit 60 is a thermocouple 61 having a reference junction 64 and a temperature-measuring junction 65. The reference junction 64 is positioned to contact the second flushing fluid, and the temperature-measuring junction 65 is positioned to contact the first flushing fluid. Therefore, the temperature difference between the reference junction 64 and the temperature-measuring junction 65 of the thermocouple 61 becomes the temperature difference ΔT between the temperature T1 of the first flushing fluid before cooling and the temperature T2 of the second flushing fluid after cooling. Thus, by using a thermocouple 61, the temperature difference detection unit 60 can be made into a simple configuration.

[0078] The control unit 4 calculates the dynamic friction coefficient μ of the sliding parts 18a and 33a based on the temperature difference ΔT detected by the temperature difference detection unit 60. Since the dynamic friction coefficient μ is closely related to the cooling status of the sliding parts 18a and 33a, the operator can more accurately estimate the cooling status of the sliding parts 18a and 33a by using the calculated dynamic friction coefficient μ. Furthermore, the formula (3) used to calculate the dynamic friction coefficient μ includes the characteristics of the flushing fluid (density γ, etc.) and the operating conditions of the mechanical seal 1 (thrust P, average peripheral speed V, etc.). Therefore, the calculated dynamic friction coefficient μ is a value that takes into account the differences in the flushing fluid and operating conditions more than the temperature difference ΔT, making it easier to compare the cooling status of the sliding parts 18a and 33a under various conditions than with the temperature difference ΔT.

[0079] When estimating the cooling status of the sliding parts 18a and 33a, the operator uses a characteristic curve CL that shows the behavior of the dynamic friction coefficient μ with respect to the duty parameter DP for the lubrication characteristics of the sliding parts 18a and 33a. The characteristic curve CL allows for a highly accurate estimation of which of the three lubrication regions (boundary lubrication region, mixed lubrication region, and fluid lubrication region) the sliding parts 18a and 33a are located in. This allows the operator to more accurately estimate the cooling status of the sliding parts 18a and 33a based on the estimated lubrication region. Furthermore, there are cases where it is difficult to estimate whether the value of the dynamic friction coefficient μ calculated by the control unit 4 is in the mixed lubrication region or the fluid lubrication region. In such cases, by using the boundary value of the duty parameter DP corresponding to the minimum value of the dynamic friction coefficient μ and the characteristic curve CL, it is possible to easily identify whether the calculated value of the dynamic friction coefficient μ is located in the mixed lubrication region or the fluid lubrication region.

[0080] [Second Embodiment] Figure 6 is a cross-sectional view showing the main parts of a mechanical seal 1 according to a second embodiment of the present disclosure. In Figure 6, the mounting structure of the thermocouple 61 in the stationary unit 3 of the mechanical seal 1 of this embodiment differs from that of the first embodiment. The stationary unit 3 of this embodiment includes an adjustment ring 56 provided between the seal case 31 and the casing 72.

[0081] The adjustment ring 56 is formed in an annular shape and is fixed to the casing 72 together with the seal case 31 by bolts 34 (see Figure 1). When fixing the adjustment ring 56 to the casing 72, adjustment rings 56 of different sizes are used depending on the type of rotating equipment 70. This allows the mechanical seal 1 to be attached to various rotating equipment 70.

[0082] The inner circumferential surface 56a of the adjustment ring 56 is positioned radially outward from the sliding portions 18a and 33a. The space between one axial side of the seal case 31 and the other axial side of the adjustment ring 56 is sealed (secondary seal) by a gasket 57. The space between one axial side of the adjustment ring 56 and the other axial side of the casing 72 is sealed (secondary seal) by an O-ring 58.

[0083] In this embodiment, the stationary unit 3 does not have an adapter ring 50 (see Figure 2). Also, there is no annular groove 31d (see Figure 2) that communicates with each hole 31a formed on the inner circumference of the seal case 31. Therefore, each hole 31a (first flow path 31b, reserve hole 31c) of the seal case 31 is in direct communication with the internal area A of the machine.

[0084] In this embodiment, the thermocouple 61 is attached to the adjustment ring 56. Specifically, the first conductor 62 and the second conductor 63 of the thermocouple 61 are fixed to the inner circumferential surface 56a of the adjustment ring 56 in a position close to the pre-hole 31c. In Figure 6, for clarity, the second conductor 63 is shown shifted radially inward from the inner circumferential surface 56a of the adjustment ring 56.

[0085] The first conductor 62 and the second conductor 63 are positioned to intersect the extension of the imaginary line X of the sliding portions 18a and 33a in the axial direction. As a result, the reference junction 64 of the thermocouple 61 is positioned to contact the first flushing fluid, and the temperature sensing junction 65 of the thermocouple 61 is positioned to contact the second flushing fluid.

[0086] Each reference junction 64 of the thermocouple 61 is connected to the corresponding connecting wires 5 and 6, with the wires protruding axially in the opposite direction from the adjustment ring 56. Each connecting wire 5 and 6 extends from the reference junction 64 of the thermocouple 61, through the pre-hole 31c, through the closing member 40, to the radially outer side of the seal case 31 (outside the machine region B) (see Figure 1).

[0087] Other components of this embodiment are the same as those of the first embodiment, and therefore are denoted by the same reference numerals, and their descriptions are omitted. The mechanical seal 1 of this embodiment also provides the same effects as those of the first embodiment.

[0088] [others] In the thermocouple 61 of the above embodiment, the reference junction 64 is positioned to contact the first flushing fluid and the temperature sensing junction 65 is positioned to contact the second flushing fluid. However, the reference junction 64 may be positioned to contact the second flushing fluid and the temperature sensing junction 65 may be positioned to contact the first flushing fluid.

[0089] The temperature difference detection unit 60 in the above embodiment consists of a thermocouple 61, but is not limited thereto. For example, the temperature difference detection unit 60 may include a pair of temperature sensors that detect the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid, respectively. Specifically, in the case of through flushing in which the stationary unit 3 includes a self-flushing pipe and a reverse flushing pipe, the temperature difference detection unit 60 may include a temperature sensor provided in the self-flushing pipe that detects the temperature T1 of the first flushing fluid in the pipe, and a temperature sensor provided in the reverse flushing pipe that detects the temperature T2 of the second flushing fluid in the pipe.

[0090] In the above embodiment, the temperature difference detection unit 60 is attached to the adapter ring 50 or the adjustment ring 56, but it may also be attached to other members constituting the stationary unit 3. In the above embodiment, the connecting wires 5 and 6 pass through the pre-hole 31c of the seal case 31, but a dedicated hole for the connecting wires 5 and 6 to pass through may be formed in the seal case 31. Alternatively, the connecting wires 5 and 6 may pass through a water injection hole that is pre-formed in the casing 72 of the rotating equipment 70.

[0091] In the above embodiment, the dynamic friction coefficient μ is automatically calculated by the control unit 4, but the dynamic friction coefficient μ may be calculated manually by the operator or other party. The mechanical seal 1 in the above embodiment is a rotary type mechanical seal, but is not limited thereto. For example, it may be a stationary type, a dual seal (tandem seal, double seal), a single coil type, or a bellows type mechanical seal, or a mechanical seal that generates a thermosiphon without actively circulating the flushing fluid, such as a double seal using a pressurized tank.

[0092] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not in the sense described above, and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of symbols]

[0093] 1 Mechanical seal 2 Rotating side unit 3 Stationary Unit 4. Control Unit 18 Rotating sealing ring 18a, 33a Sliding parts 33 Stationary sealing ring 60 Temperature difference detection unit 61 Thermocouples 64 Reference contact 65 Temperature sensing junction 71 Rotation axis 72 Casing A. In-flight area CL characteristic curve DP duty cycle parameter (dimensionless coefficient) T1 temperature T2 temperature ΔT temperature difference μ is the coefficient of kinetic friction.

Claims

1. A rotating side unit is provided on the rotating shaft so as to be rotatable integrally with it and has a rotating sealing ring, A mechanical seal comprising: a stationary side unit provided in a casing surrounding the rotating shaft, having a stationary sealing ring on which the rotating sealing ring slides to seal a fluid to be sealed in an internal region within the casing, wherein the sliding portion between the rotating sealing ring and the stationary sealing ring is cooled by a flushing fluid, A mechanical seal provided in the stationary unit, comprising a temperature difference detection unit for detecting the temperature difference between the temperature of a first flushing fluid, which is the flushing fluid, before cooling the sliding portion, and the temperature of a second flushing fluid, which is the flushing fluid, after cooling the sliding portion.

2. The mechanical seal according to claim 1, further comprising a control unit that calculates the coefficient of dynamic friction of the sliding portion based on the temperature difference.

3. The temperature difference detection unit is a thermocouple having a reference junction and a temperature measuring junction. The reference contact is arranged to contact one of the first flushing fluid and the second flushing fluid. The mechanical seal according to claim 1 or 2, wherein the temperature sensing junction is arranged to be in contact with the other of the first flushing fluid and the second flushing fluid.

4. A rotating side unit is provided on the rotating shaft so as to be rotatable integrally with it and has a rotating sealing ring, A mechanical seal comprising a stationary side unit provided in a casing surrounding the rotating shaft, the rotating sealing ring having a stationary sealing ring on which the rotating sealing ring slides to seal a fluid to be sealed in an internal region within the casing, a method for estimating the cooling state of the sliding portion between the rotating sealing ring and the stationary sealing ring by a flushing fluid, A method for estimating cooling conditions, comprising the step of detecting the temperature difference between the temperature of the flushing fluid before cooling the sliding part and the temperature of the flushing fluid after cooling the sliding part, using a temperature difference detection unit.

5. The method for estimating the cooling state according to claim 4, further comprising the step of calculating the coefficient of dynamic friction of the sliding portion based on the detected temperature difference.

6. The method for estimating the cooling status of a sliding part according to claim 5, further comprising the step of estimating the cooling status of the sliding part based on the calculated dynamic friction coefficient and a characteristic curve showing the behavior of the dynamic friction coefficient with respect to a dimensionless coefficient for the lubrication characteristics of the sliding part.

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