Mechanical seal and cooling state estimation method

Abstract

A mechanical seal (1) is provided with: a rotary-side unit (2) having a rotary seal ring (18); and a stationary-side unit 3 having a stationary sealing ring 33, the rotating sealing ring 18 and the sliding portions 18a, 33a of the stationary sealing ring 33 being cooled by a flushing fluid. A temperature difference detection unit (60) that detects a temperature difference ([Delta] T) between a temperature (T1) of the flushing fluid before the sliding portions (18a, 33a) are cooled and a temperature (T2) of the flushing fluid after the sliding portions (18a, 33a) are cooled is provided to the stationary-side unit (3).

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 structure for sealing a fluid to be sealed inside a rotating instrument, for example, a mechanical seal as shown in Patent Document 1 is known. The mechanical seal of Patent Document 1 has: a rotating seal ring (rotating ring) that is provided on the rotating shaft of the rotating instrument and slides relative to a stationary seal ring; and a stationary seal ring (fixed ring) that is provided on the housing of the rotating instrument. The sliding portions of the rotating seal ring and the stationary seal ring are cooled and lubricated by a flushing fluid.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-060079 Summary of the Invention

[0004] Regarding the mechanical seal of Patent Document 1, in order to determine whether the sliding portions of the rotating seal ring and the stationary seal ring are properly cooled by the flushing fluid, it is necessary to disassemble the mechanical seal and directly observe the sliding portions visually. Therefore, it is difficult to grasp the cooling condition of the sliding portions during the operation of the mechanical seal.

[0005] The present invention 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, which can estimate the cooling condition of the sliding portions of the rotating seal ring and the stationary seal ring by the flushing fluid without directly observing the sliding portions.

[0006] (1) The present invention is a mechanical seal having: a rotating side unit that is provided so as to be able to rotate integrally with a rotating shaft and has a rotating seal ring; and a stationary side unit that is provided in a housing surrounding the rotating shaft and has a stationary seal ring for sealing a fluid to be sealed in an internal region inside the housing and for the rotating seal ring to slide, wherein the sliding portions of the rotating seal ring and the stationary seal ring are cooled by a flushing fluid, and the mechanical seal has a temperature difference detection unit that is provided in the stationary side unit and detects a temperature difference between a first flushing fluid that is the flushing fluid before cooling the sliding portions and a second flushing fluid that is the flushing fluid after cooling the sliding portions.

[0007] In the mechanical seal according to the present invention, a temperature difference detecting unit is used to detect the temperature difference between the temperature of the first flushing fluid before cooling and the temperature of the second flushing fluid after cooling. If the temperature difference is relatively large, it means that the heat generation amount of the sliding part increases due to frictional heat or the like. As the cooling condition of the sliding part, it can be generally presumed that the supply amount of the flushing fluid to the sliding part is insufficient. On the other hand, if the temperature difference is relatively small, the heat generation amount of the sliding part is suppressed to a lower level. As the cooling condition of the sliding part, it can be generally presumed that the sliding part is properly cooled by the flushing fluid. Therefore, by using the temperature difference detecting unit to detect the temperature difference, it is possible to presume the cooling condition of the sliding part by the flushing fluid without directly observing the sliding part of the rotating seal ring and the stationary seal ring.

[0008] (2) Preferably, on the basis of the mechanical seal in (1), it further has a control unit that calculates the dynamic friction coefficient of the sliding part based on the temperature difference.

[0009] In this case, the dynamic friction coefficient calculated by the control unit is closely related to the cooling condition of the sliding part. Therefore, it is possible to more accurately presume the cooling condition of the sliding part of the rotating seal ring and the stationary seal ring by the flushing fluid based on this dynamic friction coefficient.

[0010] (3) Preferably, on the basis of the mechanical seal in (1) or (2), the temperature difference detecting unit is a thermocouple having a reference contact and a temperature measuring contact. The reference contact is arranged to contact one of the first flushing fluid and the second flushing fluid, and the temperature measuring contact is arranged to contact the other of the first flushing fluid and the second flushing fluid.

[0011] 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 flushing fluid before cooling and the temperature of the second flushing fluid after cooling. Therefore, it is possible to use the thermocouple to make the temperature difference detecting unit have a simple structure.

[0012] (4) The present invention is a method for presuming the cooling condition, which is a method for presuming the cooling condition of the sliding part of the rotating seal ring and the stationary seal ring by the flushing fluid for a mechanical seal. The mechanical seal has: a rotating side unit, which is arranged to be able to rotate integrally with the rotating shaft and has the rotating seal ring; and a stationary side unit, which is arranged in a housing surrounding the rotating shaft and has the stationary seal ring for sealing the fluid to be sealed in the internal area in the housing and for the rotating seal ring to slide on. Wherein, the method for presuming the cooling condition includes the following steps: using a temperature difference detecting unit to detect 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.

[0013] According to the cooling condition estimation method of the present invention, a temperature difference detecting unit is used to detect the temperature difference between the temperature of the flushing fluid before cooling and the temperature of the flushing fluid after cooling. If the temperature difference is relatively large, the heat generation amount of the sliding part increases due to frictional heat or the like, and as the cooling condition of the sliding part, it can be generally presumed that the supply amount of the flushing fluid to the sliding part is insufficient. In addition, if the temperature difference is relatively small, the heat generated by the sliding part is suppressed to a lower level, and as the cooling condition of the sliding part, it can be generally presumed that the sliding part is properly cooled by the flushing fluid. Therefore, by using the temperature difference detecting unit to detect the temperature difference, the cooling condition of the flushing fluid on the sliding part can be estimated without directly observing the sliding parts of the rotating seal ring and the stationary seal ring.

[0014] (5) On the basis of the cooling condition estimation method in (4) above, preferably, the following steps are further included: calculating the dynamic friction coefficient of the sliding part based on the detected temperature difference.

[0015] In this case, the dynamic friction coefficient is closely related to the cooling condition of the sliding part, so the cooling condition of the flushing fluid on the sliding parts of the rotating seal ring and the stationary seal ring can be estimated more accurately based on this dynamic friction coefficient.

[0016] (6) On the basis of the cooling condition estimation method in (5) above, preferably, the following steps are further included: estimating the cooling condition of the sliding part based on the calculated dynamic friction coefficient and a characteristic curve, which represents the behavior of the dynamic friction coefficient with respect to a dimensionless coefficient regarding the lubrication characteristics of the sliding part.

[0017] In this case, by using the characteristic curve representing the behavior of the dynamic friction coefficient with respect to a dimensionless coefficient regarding the lubrication characteristics of the sliding part, it is possible to estimate with a high degree of accuracy which lubrication region the sliding part is in. Thus, based on the estimated lubrication region, the cooling condition of the flushing fluid on the sliding parts of the rotating seal ring and the stationary seal ring can be estimated more accurately.

[0018] Effects of the Invention

[0019] According to the present invention, the cooling condition of the flushing fluid on the sliding part can be estimated without directly observing the sliding parts of the rotating seal ring and the stationary seal ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a cross-sectional view of a mechanical seal according to the first embodiment of the present invention.

[0021] Figure 2 is an enlarged cross-sectional view showing the joining ring and its surroundings.

[0022] Figure 3 It is a schematic structural diagram of a thermocouple.

[0023] Figure 4 It is a flowchart of a method for indicating the cooling state of the sliding parts of the rotating seal ring and the stationary seal ring by the presumed flushing fluid.

[0024] Figure 5 It is a graph showing characteristic curves.

[0025] Figure 6 It is a sectional view showing the main part of the mechanical seal related to the second embodiment of the present invention. Detailed implementation mode

[0026] Next, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In addition, at least a part of the embodiments described below can be arbitrarily combined.

[0027] [First Embodiment]

[0028] <Overall Structure>

[0029] Figure 1 It is a sectional view of the mechanical seal 1 according to the first embodiment of the present invention. In Figure 1 the mechanical seal 1 is used for a rotating instrument 70 such as a pump, and seals the fluid to be sealed inside the rotating instrument 70. The mechanical seal 1 is arranged axially along the rotating shaft 71 (hereinafter simply referred to as "axial direction") between the rotating shaft 71 of the rotating instrument 70 and the housing 72 surrounding the rotating shaft 71.

[0030] The mechanical seal 1 of the present embodiment has: a rotating side unit 2 which is arranged to be able to rotate integrally with the rotating shaft 71; and a stationary side unit 3 which is arranged on the housing 72. In addition, in this specification, for convenience, the Figure 1 right side of Figure 1 is called the axial side, and the Figure 2 left side of Figure 6 is called the other axial side (the same applies to

[0031] <Rotating Side Unit>

[0032] The rotating side unit 2 has a sleeve 11, a stop ring 12, a first holder 13, a drive pin 14, a drive collar 15, a spring 16, a second holder 17, and a rotating seal ring 18.

[0033] The sleeve 11 is formed in a cylindrical shape and fits onto the outer circumference of the rotary shaft 71. The retaining ring 12 fits onto the outer circumference on the other axial side of the sleeve 11. A plurality of positioning screws 19 are screwed radially in the circumferential direction of the retaining ring 12. Thereby, the sleeve 11 is fixed to the rotary shaft 71. The inner circumferential surface on one axial side of the sleeve 11 and the outer circumferential surface of the rotary shaft 71 are sealed (secondary seal) by an O-ring 20.

[0034] The first retaining member 13 is a spring retaining member. The first retaining member 13 is formed in an annular shape and fits onto the outer circumference on one axial side of the sleeve 11. A plurality of ( Figure 1 only one is shown in the figure) positioning screws 21 are screwed radially in the circumferential direction of the first retaining member 13. Thereby, the first retaining member 13 is fixed to the sleeve 11. A plurality of ( Figure 1 only one is shown in the figure) drive pins 14 penetrate the first retaining member 13 in the axial direction at intervals in the circumferential direction. The drive pins 14 are held by the first retaining member 13 so as to be movable in the axial direction.

[0035] The drive collar 15 is arranged at intervals on the other axial side of the first retaining member 13. The drive collar 15 is formed in an annular shape and fits onto the outer circumferential surface of the sleeve 11 so as to be movable in the axial direction. The end on the other axial side of the drive pin 14 is fixed (screwed) to the drive collar 15. Thereby, the drive collar 15 is held by the first retaining member 13 via the drive pin 14 so as to be movable in the axial direction, and the relative rotation with respect to the first retaining member 13 is restricted.

[0036] A plurality of ( Figure 1 only one is shown in the figure) springs 16 are provided at intervals in the circumferential direction between the drive collar 15 and the first retaining member 13. The spring 16 pre-tightens the drive collar 15 in the axial direction with respect to the first retaining member 13.

[0037] The second retaining member 17 is arranged adjacent to the other axial side of the drive collar 15. The second retaining member 17 is formed in an annular shape and fits onto the outer circumferential surface of the sleeve 11 so as to be movable in the axial direction. The end on one axial side of the second retaining member 17 is fixed to the drive collar 15. Thereby, the second retaining member 17 together with the drive collar 15 is held by the sleeve 11 so as to be movable in the axial direction, and the relative rotation with respect to the drive collar 15 is restricted. The inner circumferential surface of the second retaining member 17 and the outer circumferential surface of the sleeve 11 are sealed (secondary seal) by an O-ring 22.

[0038] The rotary seal ring 18 is formed in an annular shape and is fixed (shrink-fitted) to the other axial end of the second retaining member 17. A sealing surface 18a is formed on the end face on the other axial side of the rotary seal ring 18 (also refer to Figure 2)。The rotation seal ring 18 is pre-tensioned axially to the other side by means of a spring 16 via a drive collar 15 and a second retaining member 17.

[0039] <Stationary side unit>

[0040] The stationary side unit 3 has a seal housing 31, a bushing 32, a stationary seal ring 33, and a joint ring 50. The seal housing 31 is formed in a cylindrical shape. In order to divide the internal area A and the external area B of the rotary instrument 70, the seal housing 31 surrounds the rotary shaft 71 and is fixed to the housing 72.

[0041] In the present embodiment, the radially outer portion of the seal housing 31 is fixed to the housing 72 by bolts 34 in a state of abutting against the axially other side surface of the housing 72. The axially one side surface of the seal housing 31 and the axially other side surface of the housing 72 are sealed (secondary seal) by an O-ring 35.

[0042] A bushing 32 is installed on the inner circumference of the axially other side of the seal housing 31. The bushing 32 is formed in an annular shape, and a clearance seal is formed between the outer peripheral surface of the bushing 32 and the outer peripheral surface of the sleeve 11. An annular restricting member 36 is fixed to the end surface of the axially other side of the seal housing 31.

[0043] The end surface of the axially other side of the bushing 32 abuts against the restricting member 36. Thereby, the bushing 32 is restricted from disengaging axially to the other side with respect to the seal housing 31. The restricting member 36 has an engaging pin 36a that engages with the bushing 32. Thereby, the restricting member 36 restricts the bushing 32 from rotating together with the sleeve 11.

[0044] The stationary seal ring 33 is formed in an annular shape and is fitted and fixed to the inner peripheral surface of the seal housing 31. The outer peripheral surface of the stationary seal ring 33 and the inner peripheral surface of the seal housing 31 are sealed (secondary seal) by an O-ring 37. A seal surface 33a is formed on the end surface of the axially one side of the stationary seal ring 33 (also refer to Figure 2 )。

[0045] The seal surface 18a of the rotation seal ring 18 slides on the seal surface 33a of the stationary seal ring 33. Thereby, the fluid to be sealed is sealed in the internal area A. For the stationary seal ring 33, relative rotation with respect to the rotation seal ring 18 is restricted by a restricting pin 38 fixed to the inner circumference of the seal housing 31.

[0046] The joint ring 50 is disposed radially outside the sliding portions (seal surfaces 18a, 33a) of the rotation seal ring 18 and the stationary seal ring 33 in the internal area A. Hereinafter, the sliding portions of the rotation seal ring 18 and the stationary seal ring 33 are also referred to as sliding portions 18a, 33a. The joint ring 50 is formed in a cylindrical shape and is detachably provided on the seal housing 31.

[0047] Figure 2 is an enlarged cross-sectional view showing the joining ring 50 and its surroundings. In Figure 1 and Figure 2 , on one axial side of the outer peripheral surface 50a of the joining ring 50, it is fitted with the inner peripheral surface of the seal housing 31. The end surface 50b on the other axial side of the joining ring 50 abuts against a stepped surface 31e extending radially in the inner periphery of the seal housing 31.

[0048] The end surface 50c on one axial side of the joining ring 50 abuts against the collar 39 mounted on the seal housing 31. Thus, the joining ring 50 is held between the stepped surface 31e and the collar 39 and is held so as not to come off from the seal housing 31.

[0049] The collar 39 is detachably fitted into an annular groove 31f formed in the inner periphery of the seal housing 31. Therefore, by removing the collar 39 from the groove 31f, the joining ring 50 can be removed from the seal housing 31.

[0050] <Flow path of flushing fluid>

[0051] In Figure 1 , a flow path for supplying flushing fluid from the external region B to the internal region A is formed in the stationary side unit 3. The flushing fluid cools and lubricates the sliding portions 18a, 33a of the rotary seal ring 18 and the stationary seal ring 33. In the present embodiment, the sealed fluid is used as the flushing fluid.

[0052] In this specification, the flushing fluid before cooling the sliding portions 18a, 33a is referred to as the first flushing fluid. In addition, the flushing fluid after cooling the sliding portions 18a, 33a is referred to as the second flushing fluid. A flow path for the first flushing fluid to flow is formed in the stationary side unit 3. Hereinafter, the flow path of the first flushing fluid will be described.

[0053] On one axial side of the seal housing 31, a plurality of ( Figure 1 two in Figure 2 ) holes 31a are formed at intervals in the circumferential direction. Each hole 31a is formed to penetrate the seal housing 31 in the radial direction. An annular groove 31d communicating with each hole 31a is formed in the inner periphery of the seal housing 31 (also refer to Figure 2 ). Each hole 31a can serve as a first flow path 31b for supplying the first flushing fluid from the external region B to the internal region A.

[0054] A plurality of holes 31a that can serve as the first flow path 31b are formed in the circumferential direction of the seal housing 31 because the circumferential position where the pipe for the first flushing fluid to flow is connected to the seal housing 31 varies depending on the type of the rotary instrument 70 and the like. In the present embodiment, in Figure 1The hole 31a formed on the lower side thereof serves as the first flow path 31b. Therefore, at a specified position in the circumferential direction of the sealing housing 31 ( Figure 1 on the lower side), a first flow path 31b for supplying the first flushing fluid from the outer region B to the inner region A is formed.

[0055] Hereinafter, the other hole 31a that is not used as the first flow path 31b is also referred to as a preliminary hole 31c. The opening on the radially outer side of the preliminary hole 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 preliminary hole 31c; and a second threaded portion 42 that is screwed into the head of the first threaded portion 41. The closing member 40 suppresses the leakage of the first flushing fluid flowing into the preliminary hole 31c from the annular groove 31d to the outside.

[0056] In Figure 2 the joining ring 50 has a second flow path 51 communicating with a plurality of holes 31a (the first flow path 31b and the preliminary hole 31c) of the sealing housing 31. The second flow path 51 is a flow path for supplying the first flushing fluid from the first flow path 31b to a plurality of circumferential portions of the sliding portions 18a, 33a. The second flow path 51 has an annular flow path 52 and a plurality of supply flow paths 53.

[0057] The annular flow path 52 is formed on the outer periphery of the joining ring 50 at a position opposite to the annular groove 31d of the sealing housing 31. The annular flow path 52 of the present embodiment is constituted by an annular cut groove formed on the outer periphery of the joining ring 50. The axial width of the annular flow path 52 is the same as the groove width of the annular groove 31d of the sealing housing 31. As described above, the first flushing fluid from the first flow path 31b flows in the circumferential direction in the flow path constituted by the annular groove 31d and the annular flow path 52.

[0058] In Figure 1 and Figure 2 the plurality of supply flow paths 53 are flow paths for supplying the first flushing fluid from the annular flow path 52 to the inner region A. The supply flow paths 53 are formed to penetrate the joining ring 50 in the radial direction from a plurality of circumferential portions on the bottom surface of the annular flow path 52. Thus, the first flushing fluid is supplied to the inner region A from the plurality of supply flow paths 53, so that the sliding portions 18a, 33a can be cooled and lubricated without omission in the entire circumference.

[0059] Each supply flow path 53 is formed such that the opening 53a on its radially inner side is located on the axially other side (outer region B side) than the sliding portions 18a, 33a. Thus, in the inner region A, the first flushing fluid and the second flushing fluid are roughly divided into two streams in the axial direction with the extended virtual line X of the sliding portions 18a, 33a as the boundary. Specifically, in the inner region A, the first flushing fluid occupies the region on the axially other side than the extended virtual line X, and the second flushing fluid occupies the region on the axially one side than the extended virtual line X.

[0060] <Temperature difference detection unit>

[0061] The mechanical seal 1 further includes: a temperature difference detection unit 60 provided in the stationary side unit 3; and a control unit 4. 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. The temperature difference detection unit 60 of the present embodiment is composed of a single thermocouple 61. The thermocouple 61 of the present embodiment is mounted on the joint ring 50.

[0062] Figure 3 is a schematic structural diagram of the thermocouple 61. In Figure 2 and Figure 3 the thermocouple 61 is a thermocouple utilizing the Seebeck effect. The thermocouple 61 has a first conductor 62 and a second conductor 63 made of different metal materials. The first conductor 62 is made of an alloy mainly composed of nickel and chromium, for example. The second conductor 63 is made of an alloy mainly composed of nickel and aluminum, for example.

[0063] The first conductor 62 and the second conductor 63 are inserted and mounted in a mounting hole 54 formed through the joint ring 50 in the radial direction. The mounting hole 54 is formed at a position corresponding to the preliminary hole 31c in the joint ring 50. In addition, the mounting hole 54 is formed to be inclined from the axial other side to the axial one side as it approaches the inner peripheral surface from the outer peripheral surface of the joint ring 50. The radially inner opening 54a of the mounting hole 54 is located in the internal region A at a position in a region closer to the axial one side than the extended virtual line X (the region occupied by the second flushing fluid).

[0064] In addition, 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 penetrate therethrough. The sealing member is used to prevent the first flushing fluid flowing in the annular flow path 52 from flowing into the region of the second flushing fluid occupying the internal region A through the mounting hole 54.

[0065] One end of the first conductor 62 and one end of the second conductor 63 are joined to each other in a state of protruding into the region on the axial one side of the internal region A from the opening 54a of the mounting hole 54. This joined portion is set as the temperature measurement contact 65 of the thermocouple 61. Therefore, the temperature measurement contact 65 of the thermocouple 61 of the present embodiment is arranged to contact the second flushing fluid.

[0066] The other end of the first conductor 62 and the other end of the second conductor 63 are arranged in the annular flow path 52 through which the first flushing fluid flows in a state of protruding radially outward and being separated from each other. The other end of the first conductor 62 and the other end of the second conductor 63 arranged in the annular flow path 52 are respectively set as the reference contacts 64 of the thermocouple 61. Therefore, the reference contacts 64 of the thermocouple 61 of the present embodiment are arranged to contact the first flushing fluid in the annular flow path 52.

[0067] The other end of the first conductor 62 is connected to a connection wire 5 made of a metal material different from that of the first conductor 62 and the second conductor 63 by welding or the like. The other end of the second conductor 63 is connected to a connection wire 6 made of a metal material different from that of the first conductor 62 and the second conductor 63 by welding or the like. Each of the connection wires 5 and 6 is formed of, for example, a copper wire.

[0068] As Figure 1 and Figure 2 shown, each of the connection wires 5 and 6 extends from the reference contact 64 of the thermocouple 61 through the annular flow path 52 and the preliminary hole 31c, penetrates the closing member 40, and extends to the radially outer side (outer region B) of the sealed housing 31. The ends of the connection wires 5 and 6 in the outer region B are connected to the control unit 4.

[0069] According to the above structure, the thermocouple 61 outputs a thermal electromotive force corresponding to the temperature difference ΔT generated between the temperature T1 of the reference contact 64 (the first flushing fluid) and the temperature T2 of the temperature measurement contact 65 (the second flushing fluid) to the control unit 4 via the connection wires 5 and 6. That is, if 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 (thermal electromotive force) corresponding to the temperature difference ΔT to the control unit 4. The thermocouple 61 detects the temperature difference ΔT at regular intervals and outputs the signal to the control unit 4.

[0070] <Control Unit>

[0071] The control unit 4 is disposed in the outer region B. The control unit 4 is configured to include a computer having a CPU and the like. Each function of the control unit 4 is realized by the CPU executing a control program stored in a storage device of the computer. The control unit 4 calculates the dynamic friction coefficient μ of the sliding portions 18a and 33a based on the thermal electromotive force input from the thermocouple 61 at regular intervals. Hereinafter, a specific calculation method thereof will be described.

[0072] First, the control unit 4 extracts, for example, the temperature difference ΔT corresponding to the thermal electromotive force input from the thermocouple 61 from a table in which the thermal electromotive force and the temperature difference ΔT are associated. In addition, the control unit 4 can calculate the temperature difference ΔT based on the thermal electromotive force input from the thermocouple 61 using a prescribed calculation formula.

[0073] Next, the control unit 4 substitutes the extracted temperature difference ΔT into Equation (3) derived from the following Equations (1) and (2) to calculate the dynamic friction coefficient μ. Equation (1) is an arithmetic expression representing the frictional heat Q [kJ / min] of the sliding portions 18a and 33a. Equation (2) is an arithmetic expression representing the flow rate Wf [L / min] of the flushing fluid required for cooling the sliding portions 18a and 33a.

[0074] Q = (μ·P·V) × 60 ÷ 1000…(1)

[0075] Wf = Q ÷ (Cp·γ·ΔT)…(2)

[0076] μ = Wf × (Cp·γ·ΔT) ÷ (P·V) × 1000 ÷ 60…(3)

[0077] Here, P is the apparent thrust [N] applied to the sliding parts 18a, 33a. V is the average circumferential velocity [m / s] of the sealing surface 18a of the rotary seal 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.

[0078] <Method for estimating the cooling condition of the sliding part>

[0079] Figure 4 is a flowchart showing a method for estimating the cooling condition of the sliding parts 18a, 33a of the rotary seal ring 18 and the stationary seal ring 33 by the flushing fluid. Hereinafter, with reference to Figure 4 the method for estimating the cooling condition will be described.

[0080] First, the temperature difference detector 60 detects the temperature difference before and after the cooling of the flushing fluid, that is, the temperature difference ΔT between the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid (step ST1). The temperature difference detector 60 outputs a thermoelectromotive force corresponding to the temperature difference ΔT to the control unit 4 in the above manner.

[0081] Next, in the control unit 4, the dynamic friction coefficient μ of the sliding parts 18a, 33a is calculated based on the temperature difference ΔT (step ST2). The specific calculation method of the dynamic friction coefficient μ of the control unit 4 is as described above.

[0082] Next, based on the calculated dynamic friction coefficient μ and the characteristic curve CL, the cooling condition of the sliding parts 18a, 33a is estimated (step ST3). The characteristic curve CL is a curve showing the operation of the dynamic friction coefficient μ with respect to the dimensionless coefficient regarding the lubrication characteristics of the sliding parts 18a, 33a. The estimation of the cooling condition of the sliding parts 18a, 33a is performed, for example, by a practitioner who performs maintenance and repair of the mechanical seal 1.

[0083] As the dimensionless coefficient, for example, the duty ratio parameter DP is used. The duty ratio parameter DP represents the characteristics (lubrication characteristics) of the lubricating film of the flushing fluid formed on the sliding parts 18a, 33a. The duty ratio parameter DP is calculated according to the following formula (4).

[0084] DP = (η × ω × b) ÷ W…(4)

[0085] Here, η is the viscosity of the flushing fluid [Pa·s]. ω is the peripheral velocity of the sealing surface 18a of the rotary seal ring 18 [m / s]. b is the radial sliding amplitude of the sealing surface 18a [m]. W is the pressing load [N] on the rotary seal ring 18 by the spring 16 (see Figure 1 ).

[0086] The characteristic curve CL of the present embodiment represents the operation of the dynamic friction coefficient μ with respect to the duty ratio parameter DP. For the characteristic curve CL, it is created in advance by conducting tests such as the static load capacity test of the mechanical seal 1 by changing the duty ratio parameter DP. The characteristic curve CL is a curve that varies depending on the type of the flushing fluid and the like.

[0087] Figure 5 It is a graph showing the characteristic curve CL created by conducting the above tests and the like. The vertical axis of this graph represents the dynamic friction coefficient μ, and the horizontal axis represents the duty ratio parameter DP. As Figure 5 shown, the value of the dynamic friction coefficient μ of the sliding portions 18a and 33a changes substantially along the characteristic curve CL corresponding to the value of the duty ratio parameter DP. By changing the value of the dynamic friction coefficient μ in this way, the state of the lubricating film of the flushing fluid formed in the sliding portions 18a and 33a changes.

[0088] As Figure 5 shown, the state of the lubricating film of the flushing fluid changes to three regions corresponding to the value of the duty ratio parameter DP. Specifically, the state of the lubricating film of the flushing fluid changes in the order of the boundary lubrication region, the mixed lubrication region, and the fluid lubrication region as the value of the duty ratio parameter DP increases.

[0089] In the boundary lubrication region, it is formed into a state where the dynamic friction coefficient μ is relatively large and the thickness of the lubricating film of the flushing fluid is relatively thin. Therefore, in the boundary lubrication region, the supply amount of the flushing fluid to the sliding portions 18a and 33a is insufficient, and the sealing surfaces 18a and 33a are likely to come into direct contact with each other, showing a tendency of an increase in the wear amount. In the mixed lubrication region, the dynamic friction coefficient μ is in an appropriate range, and the thickness of the lubricating film of the flushing fluid is also in an appropriate range. In the fluid lubrication region, it is formed into a state where the dynamic friction coefficient μ is relatively small and the thickness of the lubricating film of the flushing fluid is relatively thick. Therefore, the fluid to be sealed is likely to leak in the sliding portions 18a and 33a.

[0090] In accordance with Figure 5When estimating the cooling condition of the sliding portions 18a and 33a based on the characteristic curve CL, first, the practitioner determines the position of the calculated value of the coefficient of kinetic friction μ based on the control unit 4 on the characteristic curve CL. In addition, the characteristic curve CL is formed in an approximate V shape with a trough at the position where the coefficient of kinetic friction μ is the minimum (near the boundary between the mixed lubrication region and the fluid lubrication region). Therefore, on the characteristic curve CL in the mixed lubrication region and the characteristic curve CL in the fluid lubrication region, the calculated value of the coefficient of kinetic friction μ may show the same value.

[0091] In this case, the practitioner calculates the value of the duty ratio parameter DP corresponding to the used flushing fluid using the above formula (4). Moreover, the practitioner determines the position of the calculated value of the coefficient of kinetic friction μ on the characteristic curve CL based on whether the calculated value of the duty ratio parameter DP is greater than or less than the value of the duty ratio parameter DP (boundary value) corresponding to the minimum coefficient of kinetic friction μ.

[0092] Specifically, when the calculated value of the duty ratio parameter DP is greater than the boundary value, the practitioner can determine that the calculated value of the coefficient of kinetic friction μ is on the characteristic curve CL in the fluid lubrication region. In addition, when the calculated value of the duty ratio parameter DP is less than the boundary value, the practitioner can determine that the calculated value of the coefficient of kinetic friction μ is on the characteristic curve CL in the mixed lubrication region. Moreover, the boundary value of the duty ratio parameter DP is a known value that is approximately constant for each flushing fluid and the like.

[0093] Next, the practitioner confirms the position determined on the characteristic curve CL Figure 5 in which region among the boundary lubrication region, the mixed lubrication region, and the fluid lubrication region is included in the graph. The practitioner can estimate the cooling condition of the sliding portions 18a and 33a based on the region including the position determined on the characteristic curve CL.

[0094] Specifically, when the position determined on the characteristic curve CL is included in the boundary lubrication region, as the cooling condition of the sliding portions 18a and 33a, it can be presumed that the thickness of the lubricating film of the flushing fluid is relatively thin as described above, and the supply amount of the flushing fluid to the sliding portions 18a and 33a is insufficient.

[0095] In addition, when the position determined on the characteristic curve CL is included in the mixed lubrication region, since the thickness of the lubricating film of the flushing fluid is in an appropriate range as described above, as the cooling condition of the sliding portions 18a and 33a, it can be presumed that the cooling of the sliding portions 18a and 33a is appropriately performed.

[0096] In addition, when a point on the determined 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 as the cooling condition of the sliding portions 18a and 33a, it can be presumed that the sealed fluid easily leaks from the sliding portions 18a and 33a.

[0097] In the present embodiment, the practitioner presumes the cooling condition of the sliding portions 18a and 33a based on the dynamic friction coefficient μ calculated based on the temperature difference ΔT and the characteristic curve CL, but the cooling condition of the sliding portions 18a and 33a can also be presumed according to the temperature difference ΔT. In this case, if the temperature difference ΔT is relatively large, the heat generation amount of the sliding portions 18a and 33a increases due to frictional heat or the like, and as the cooling condition of the sliding portions 18a and 33a, it can be roughly presumed that the supply amount of the flushing fluid to the sliding portions 18a and 33a is insufficient. In addition, if the temperature difference ΔT is relatively small, the heat generation amount of the sliding portions 18a and 33a is suppressed to be low, and as the cooling condition of the sliding portions 18a and 33a, it can be roughly presumed that the sliding portions 18a and 33a are appropriately cooled by the flushing fluid.

[0098] In addition, the practitioner can presume the cooling condition of the sliding portions 18a and 33a based on 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 condition of the sliding portions 18a and 33a, the cooling condition of the sliding portions 18a and 33a can also be accurately presumed according to the temperature difference ΔT.

[0099] <Function and effect>

[0100] According to the mechanical seal 1 of the present embodiment, the temperature difference detection unit 60 detects 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. The cooling condition of the sliding portions 18a and 33a of the rotating seal ring 18 and the stationary seal ring 33 can be roughly presumed based on the detected temperature difference ΔT. Therefore, the practitioner can presume the cooling condition of the sliding portions 18a and 33a based on the flushing fluid without directly observing the sliding portions 18a and 33a of the rotating seal ring 18 and the stationary seal ring 33.

[0101] The temperature difference detection unit 60 is a thermocouple 61 having a reference contact 64 and a temperature measurement contact 65. The reference contact 64 is arranged to contact the second flushing fluid, and the temperature measurement contact 65 is arranged to contact the first flushing fluid. Therefore, the temperature difference between the reference contact 64 and the temperature measurement contact 65 of the thermocouple 61 is 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. Therefore, the temperature difference detection unit 60 can be formed into a simple structure by using the thermocouple 61.

[0102] 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 condition of the sliding parts 18a and 33a, if a practitioner uses the calculated dynamic friction coefficient μ, the cooling condition of the sliding parts 18a and 33a can be more accurately estimated. In addition, the formula (3) for calculating the dynamic friction coefficient μ includes the characteristics of the flushing fluid (such as density γ) and the operating conditions of the mechanical seal 1 (thrust P, average peripheral speed V, etc.). Therefore, when compared with the temperature difference ΔT, the calculated dynamic friction coefficient μ becomes a value that further considers the differences in the flushing fluid and operating conditions. Therefore, compared with the temperature difference ΔT, it is easier to compare the cooling conditions of the sliding parts 18a and 33a under various conditions.

[0103] When a practitioner estimates the cooling condition of the sliding parts 18a and 33a, a characteristic curve CL showing the action of the dynamic friction coefficient μ with respect to the duty ratio parameter DP regarding the lubrication characteristics of the sliding parts 18a and 33a is used. By using the characteristic curve CL, it is possible to estimate with high accuracy which of the three lubrication regions (boundary lubrication region, mixed lubrication region, fluid lubrication region) the sliding parts 18a and 33a are in. Thus, based on the estimated lubrication region, a practitioner can more accurately estimate the cooling condition of the sliding parts 18a and 33a. In addition, sometimes it is difficult to estimate which of the mixed lubrication region and the fluid lubrication region the value of the dynamic friction coefficient μ calculated by the control unit 4 is in. In this case, by using the boundary value of the duty ratio parameter DP corresponding to the minimum dynamic friction coefficient μ and the characteristic curve CL, it is possible to easily determine which of the mixed lubrication region and the fluid lubrication region the calculated value of the dynamic friction coefficient μ is in.

[0104] [Second Embodiment]

[0105] Figure 6 is a cross-sectional view showing the main part of the mechanical seal 1 according to the second embodiment of the present invention. In Figure 6 , regarding the mechanical seal 1 of the present embodiment, the installation structure of the thermocouple 61 of the stationary side unit 3 is different from that of the first embodiment. The stationary side unit 3 of the present embodiment has an adjustment ring 56 provided between the seal housing 31 and the housing 72.

[0106] The adjustment ring 56 is formed in a circular ring shape and is fixed to the housing 72 together with the seal housing 31 by bolts 34 (refer to Figure 1 ). When fixing the adjustment ring 56 to the housing 72, adjustment rings 56 of different sizes are used according to the type of the rotating instrument 70. Thus, the mechanical seal 1 can be installed on various rotating instruments 70.

[0107] The inner peripheral surface 56a of the adjusting ring 56 is disposed radially outside the sliding portions 18a and 33a. A gasket 57 seals (secondary seal) between the side surface on the axial one side of the sealing housing 31 and the side surface on the axial other side of the adjusting ring 56. An O-ring 58 seals (secondary seal) between the side surface on the axial one side of the adjusting ring 56 and the side surface on the axial other side of the housing 72.

[0108] In addition, the stationary side unit 3 of the present embodiment does not have a joint ring 50 (refer to Figure 2 ). Further, an annular groove 31d communicating with each hole 31a is not formed on the inner periphery of the sealing housing 31 (refer to Figure 2 ). Therefore, each hole 31a (the first flow path 31b and the reserve hole 31c) of the sealing housing 31 directly communicates with the internal region A.

[0109] The thermocouple 61 of the present embodiment is mounted on the adjusting ring 56. Specifically, the first conductor 62 and the second conductor 63 of the thermocouple 61 are fixed to positions close to the reserve hole 31c on the inner peripheral surface 56a of the adjusting ring 56. Further, in Figure 6 , for easy understanding, the second conductor 63 is shown offset radially inward from the inner peripheral surface 56a of the adjusting ring 56.

[0110] The first conductor 62 and the second conductor 63 are arranged to intersect an extended virtual line X of the sliding portions 18a and 33a in the axial direction. Thereby, the reference contact 64 of the thermocouple 61 is arranged to contact the first flushing fluid, and the temperature measuring contact 65 of the thermocouple 61 is arranged to contact the second flushing fluid.

[0111] Each reference contact 64 of the thermocouple 61 is connected to the corresponding connection wires 5 and 6 in a state protruding more axially on the other side than the adjusting ring 56. Each connection wire 5 and 6 extends from the reference contact 64 of the thermocouple 61 through the reserve hole 31c, penetrates the closing member 40, and extends to the radially outside (external region B) of the sealing housing 31 (refer to Figure 1 ).

[0112] Other structures of the present embodiment are the same as those of the first embodiment, so the same reference numerals are given and their descriptions are omitted. Regarding the mechanical seal 1 of the present embodiment, the same effects as those of the first embodiment can also be achieved.

[0113] [Other]

[0114] Regarding the thermocouple 61 of the above embodiment, the reference contact 64 is arranged to contact the first flushing fluid, and the temperature measuring contact 65 is arranged to contact the second flushing fluid. However, the reference contact 64 may be arranged to contact the second flushing fluid, and the temperature measuring contact 65 may be arranged to contact the first flushing fluid.

[0115] The temperature difference detection unit 60 in the above-described embodiment is constituted by the thermocouple 61, but is not limited thereto. For example, the temperature difference detection unit 60 may have a pair of temperature sensors that respectively detect the temperature T1 of the first flushing fluid and the temperature T2 of the second flushing fluid. Specifically, in the case where the stationary side unit 3 includes through flushing including the self-flushing pipe and the reverse flushing pipe, the temperature difference detection unit 60 may have: a temperature sensor provided in the self-flushing pipe and detecting the temperature T1 of the first flushing fluid in the pipe; and a temperature sensor provided in the reverse flushing pipe and detecting the temperature T2 of the second flushing fluid in the pipe.

[0116] The temperature difference detection unit 60 in the above-described embodiment is mounted on the joining ring 50 or the adjustment ring 56, but may also be mounted on other components constituting the stationary side unit 3. In the above-described embodiment, the connection wires 5 and 6 pass through the preliminary hole 31c of the sealing housing 31, but a dedicated hole for the connection wires 5 and 6 to pass through may also be formed in the sealing housing 31. In addition, the connection wires 5 and 6 may pass through a hole for water injection formed in the housing 72 of the rotating instrument 70 in advance.

[0117] In the above-described embodiment, the dynamic friction coefficient μ is automatically calculated by the control unit 4, but the dynamic friction coefficient μ may also be calculated manually by a practitioner or the like. The mechanical seal 1 in the above-described embodiment is a rotary type mechanical seal, but is not limited thereto. For example, it may be a stationary type, a double seal (series seal, double seal), a single coil type or a bellows type mechanical seal, or may be a mechanical seal such as a double seal using a pressure tank that does not actively circulate the flushing fluid and generates a thermosyphon.

[0118] It should be understood that the embodiments disclosed this time are examples in all aspects and are not limited. The scope of the present invention is not represented by the above-described embodiments, but is represented by the claims, and is intended to include a scope equivalent to the scope of the claims and all modifications within the scope.

[0119] Description of reference numerals

[0120] 1 Mechanical seal

[0121] 2 Rotating side unit

[0122] 3 Stationary side unit

[0123] 4 Control unit

[0124] 18 Rotating seal ring

[0125] 18a, 33a Sliding part

[0126] 33 Stationary seal ring

[0127] 60 Temperature difference detection unit

[0128] 61 Thermocouple

[0129] 64 Reference Contact

[0130] 65 Temperature Measuring Contact

[0131] 71 Rotating Shaft

[0132] 72 Housing

[0133] A Inner Region

[0134] CL Characteristic Curve

[0135] DP Duty Cycle Parameter (Dimensionless Coefficient)

[0136] T1 Temperature

[0137] T2 Temperature

[0138] ΔT Temperature Difference

[0139] μ Coefficient of Kinetic Friction

Claims

1. A mechanical seal having: A rotating side unit configured to rotate integrally with a rotating shaft and having a rotating seal ring; and A stationary side unit provided in a housing surrounding the rotating shaft and having a stationary seal ring for sealing a fluid to be sealed in an internal area within the housing and for sliding contact with the rotating seal ring, wherein a sliding portion of the rotating seal ring and the stationary seal ring is cooled by a flushing fluid, and the mechanical seal has a temperature difference detection unit provided in the stationary side unit for detecting a temperature difference between a first flushing fluid, which is the flushing fluid before cooling the sliding portion, and a second flushing fluid, which is the flushing fluid after cooling the sliding portion.

2. The mechanical seal according to claim 1, wherein the mechanical seal further has a control unit for calculating a dynamic friction coefficient of the sliding portion based on the temperature difference.

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

4. A method for estimating a cooling condition, which is a method for estimating a cooling condition of a flushing fluid for a sliding portion of a rotating seal ring and a stationary seal ring in a mechanical seal, the mechanical seal having: A rotating side unit configured to rotate integrally with a rotating shaft and having the rotating seal ring; and A stationary side unit provided in a housing surrounding the rotating shaft and having the stationary seal ring for sealing a fluid to be sealed in an internal area within the housing and for sliding of the rotating seal ring, wherein the method for estimating the cooling condition includes the step of: detecting, using a temperature difference detection unit, a temperature difference between the flushing fluid before cooling the sliding portion and the flushing fluid after cooling the sliding portion.

5. The method for estimating the cooling condition according to claim 4, wherein the method for estimating the cooling condition further includes the step of: calculating a dynamic friction coefficient of the sliding portion based on the detected temperature difference.

6. The method for estimating the cooling condition according to claim 5, wherein the method for estimating the cooling condition further includes the step of: estimating the cooling condition of the sliding portion based on the calculated dynamic friction coefficient and a characteristic curve representing the behavior of the dynamic friction coefficient with respect to a dimensionless coefficient regarding the lubrication characteristic of the sliding portion.

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