Slide ring seal arrangement, in particular for bearing sealing

Abstract

The invention relates to a slide ring seal arrangement, comprising a slide ring seal (2) with a rotating slide ring (3) and a stationary slide ring (4) which define, between their sliding faces, a sealing gap (5), a sealing fluid supply system (6) for providing sealing fluid to the slide ring seal (2), and a valve arrangement (7) in a supply line (60) for supplying the sealing fluid to the slide ring seal (2), wherein the valve arrangement (7) is configured to control a pressure (P) of the sealing fluid in dependence on operating variables of the slide ring seal (2), and a control unit (9) which is configured to control the valve arrangement (7) in dependence on a circumferential speed (U) of the rotating slide ring (3).

Description

[0001] Mechanical seal arrangement, especially for bearing sealing

[0002] Description

[0003] The invention relates to a mechanical seal arrangement, in particular for sealing a bearing with a significantly reduced barrier fluid consumption.

[0004] Mechanical seal arrangements are known in various designs from the state of the art. When sealing bearings, mechanical seal arrangements are usually operated with a constant pressure of a barrier fluid of approximately 2.7-10 5Pa. This relatively high pressure of the barrier fluid is necessary to ensure that the mechanical seal is safely lifted off even at standstill, so that there is no contact on the sliding surfaces of the seal rings. Furthermore, bearing seals are subject to frequent start-up and standstill processes, or a rotating component is operated at only a very low speed, or one direction of rotation is reversed. The tightness of the bearing is ensured in all operating situations with low speeds by the high pressure of the barrier fluid. During operation, however, this leads to a large leakage of barrier fluid via the open sealing gap on the sliding surfaces.

[0005] It is therefore an object of the present invention to provide a mechanical seal arrangement and a bearing arrangement with a mechanical seal arrangement according to the invention, which has a simple structure and simple, cost-effective manufacture and a significant reduction in the consumption of barrier fluid.

[0006] This object is achieved by a mechanical seal arrangement having the features of claim 1 and a bearing arrangement having the features of claim 10. The subclaims each show preferred developments of the invention.

[0007] The mechanical seal assembly according to the invention with the features of claim 1 has the advantage that the consumption of barrier fluid can be significantly reduced. Although the invention results in increased measurement and control technology expenditure, this expenditure is more than offset by the savings in barrier fluid of at least 50% compared to the prior art. This is achieved according to the invention in that the mechanical seal assembly has a mechanical seal with a rotating seal ring and a stationary seal ring. A sealing gap is defined between a sliding surface of the rotating seal ring and a sliding surface of the stationary seal ring. The mechanical seal assembly further comprises a barrier fluid supply system for providing barrier fluid to the mechanical seal and a valve arrangement.The valve assembly is located in a barrier fluid supply line from the barrier fluid supply system to the mechanical seal. The valve assembly is designed to adjust the barrier fluid pressure depending on the operating parameters of the system.

[0008] Furthermore, the mechanical seal arrangement comprises a control unit which is designed to control the valve arrangement in dependence on a

[0009] The rotating speed of the rotating seal ring is used as the operating variable of the mechanical seal. The rotating speed U is calculated using the following formula:

[0010] U = Dirn, where n is the rotational speed of the rotating seal ring in rpm and D is the maximum outer diameter of the rotating seal ring in mm. Thus, in addition to the rotational speed n, the diameter D of the rotating seal ring is also used to control the pressure of the barrier fluid.

[0011] The control unit is further preferably configured to control the pressure of the barrier fluid such that the pressure is constant from a standstill of the rotating seal ring up to a first threshold value of the circumferential speed. This ensures a secure seal at the sealing gap of the mechanical seal.

[0012] Further preferably, the pressure of the barrier fluid decreases from the first threshold value to a second threshold value of the peripheral speed of the rotating seal ring. This means that the pressure at the second threshold value is lower than the pressure at the first threshold value. Preferably, the pressure of the barrier fluid decreases linearly, or the pressure of the barrier fluid decreases abruptly at the first threshold value. Further preferably, a change in the pressure of the barrier fluid is also possible such that the pressure of the barrier fluid first decreases abruptly and then decreases linearly up to the second threshold value of the peripheral speed.

[0013] According to a further preferred embodiment of the invention, the pressure of the barrier fluid increases again starting from the second threshold value. Preferably, the pressure increases linearly. Further preferably, a gradient of the increase in the pressure of the barrier fluid is greater than a gradient of the decrease in the pressure of the barrier fluid from the first to the second threshold value of the peripheral speed. Further preferably, the control unit is configured to additionally control the valve arrangement as a function of a temperature of components of the mechanical seal. In particular, a temperature of the stationary seal ring and / or rotating seal ring is detected and used to control the pressure of the barrier fluid.By monitoring the temperature of mechanical seal components, this can enable further improvement in the control of the valve arrangement, thereby further reducing barrier fluid consumption, in particular by up to 90% compared to the prior art. Furthermore, monitoring the temperature of mechanical seal components can also prevent the oil in a bearing sealed by the mechanical seal arrangement from overheating. Furthermore, the measurement of temperatures of mechanical seal components, in particular the temperature of the seal rings, is also preferably used to monitor the mechanical seal arrangement. Should the temperature of the seal rings become too high, a warning signal or a command to shut down the system can be issued by the control unit of the mechanical seal arrangement.

[0014] Particularly preferably, the control unit is configured to control the pressure of the barrier fluid such that the pressure of the barrier fluid also increases with increasing temperature of the components of the mechanical seal. This ensures that more barrier fluid is supplied to the mechanical seal, and since the barrier fluid has a low temperature compared to the temperatures of the components of the mechanical seal, in particular ambient temperature, cooling of the components of the mechanical seal can be achieved.

[0015] For a particularly compact design, the barrier fluid is supplied through a bore through one of the seal rings, in particular the stationary seal ring, from a rear side of the seal ring to the sealing gap.

[0016] Furthermore, the present invention relates to a bearing arrangement comprising a mechanical seal arrangement according to the invention and a bearing, wherein the mechanical seal arrangement is preferably arranged directly adjacent to the bearing.

[0017] The barrier fluid is preferably a gas, in particular nitrogen or air. The bearing is preferably oil-lubricated, so that the mechanical seal arrangement provides an oil seal on the bearing.

[0018] The mechanical seal assembly preferably comprises a pressure sensor in the supply line of the barrier fluid to the mechanical seal in order to detect the current pressure of the barrier fluid. Further preferably, the mechanical seal assembly comprises a speed sensor, which detects a speed of the rotating seal ring and / or a rotating component to which the rotating seal ring is connected. Additionally or alternatively, a speed value can also be taken from a system on which the mechanical seal assembly seals. Further preferably, the mechanical seal assembly comprises a temperature sensor, which detects a temperature of components of the mechanical seal, in particular of the stationary and rotating seal rings, and outputs it to the control unit.

[0019] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0020] Fig. 1 is a schematic sectional view of a bearing arrangement with a mechanical seal arrangement according to a first preferred embodiment of the invention,

[0021] Fig. 2 is a diagram of a control function of the pressure P of the barrier fluid over the circumferential speed U of the mechanical seal arrangement of Fig. 1,

[0022] Fig. 3 is a diagram of the mechanical seal arrangement of Fig. 1 , in which the pressure P and the speed n are shown over time t,

[0023] Fig. 4 is a diagram showing a control function of the pressure P of the barrier fluid over the circumferential speed U of a mechanical seal arrangement according to a second embodiment,

[0024] Fig. 5 is a diagram showing the pressure P of the barrier fluid versus the temperature T of the second embodiment, and

[0025] Fig. 6 is a diagram of the second embodiment, showing curves for the pressure P of the barrier fluid, the speed n and the temperature T of the rotating seal ring over time t.

[0026] A bearing arrangement 100 with a mechanical seal arrangement 1 according to a first embodiment of the invention is described in detail below with reference to Figures 1 to 3.

[0027] The bearing assembly 100 includes a bearing 101 that supports a shaft 8 on a housing 10. XX denotes the center axis of the shaft 8.

[0028] The mechanical seal assembly 1 comprises a mechanical seal 2 with a rotating seal ring 3 and a stationary seal ring 4. A sealing gap 5 is defined between the sliding surfaces of the rotating seal ring 3 and the stationary seal ring 4. The rotating seal ring 3 is connected to the shaft 8 by means of a seal ring carrier 30.

[0029] A through-hole 40 is provided in the stationary seal ring 4 to supply barrier fluid from a rear side of the stationary seal ring 4 to the sealing gap 5. The mechanical seal 2 seals an area 12 of a bearing chamber 11.

[0030] The mechanical seal assembly 1 further comprises a barrier fluid supply system 6. The barrier fluid supply system 6 supplies barrier fluid to the mechanical seal 2. In this exemplary embodiment, the barrier fluid is nitrogen. The barrier fluid supply system 6 comprises a barrier fluid source 61, for example, a nitrogen generator, and a supply line 60 connecting the barrier fluid source 61 to the through-opening 40 on the stationary seal ring 4.

[0031] A valve arrangement 7 is arranged in the supply line 60, wherein the valve arrangement 7 is configured to control a pressure P of the barrier fluid as a function of operating variables of the mechanical seal 2. The valve arrangement 7 comprises, for example, a proportional valve.

[0032] The mechanical seal assembly 1 further comprises a control unit 9. The control unit 9 is configured to control the valve assembly 7 as a function of a circumferential speed U of the rotating seal ring 3. This allows the pressure of the barrier fluid in the supply line 60 to be regulated.

[0033] The circumferential speed U of the rotating seal ring 3 is determined using the formula

[0034] U = Dirn, where D is a diameter of the rotating seal ring 3 in mm and n is the speed of the rotating seal ring 3.

[0035] As can be seen from Fig. 1, the mechanical seal arrangement 1 has a pressure sensor 13 on the supply line 60, a temperature sensor 14 for determining a temperature of the stationary seal ring 4 and a speed sensor 15 for determining the speed n of the rotating seal ring 3.

[0036] The three sensors are all connected to the control unit 9.

[0037] A control of the valve arrangement 7 according to the first embodiment is now shown schematically in the diagrams of Figures 2 and 3.

[0038] Fig. 2 shows a control function for the pressure P1 in the supply line 60 over the peripheral speed U. In Fig. 2, a corresponding curve A is shown. In the first embodiment, the curve A is divided into three areas, namely a first area A1, a second area A2 and a third area A3. In the first area A1, the barrier fluid supply system 6 provides a pressure P1 of the barrier fluid of approximately 2.7 ■ 10 5 Pa. This allows a reliable seal to be achieved at the sealing gap 5 of the mechanical seal 2 during standstill (U = 0), ie when the shaft 8 is stationary. However, the high pressure P leads to a relatively high leakage at the sealing gap 5; however, the oil-filled bearing chamber 11 can be reliably sealed from the area 12.

[0039] When the rotating seal ring 3 of the mechanical seal 2 begins to rotate, the pressure P of the barrier fluid in the first region A1 remains constant at the initial pressure P1 up to a first threshold value U1 of the peripheral speed. Starting from the first threshold value U1, the pressure P of the barrier fluid then decreases down to a second threshold value U2.

[0040] As can be seen from Fig. 2, a sudden reduction in the pressure P of the barrier fluid occurs at the first threshold value U1. From the first threshold value U1 to the second threshold value U2 of the peripheral speed, the pressure P is then continuously reduced in a linear manner with increasing peripheral speed (second range A2). Upon reaching the second threshold value U2, the pressure P of the barrier fluid is again increased linearly in the third range A3.

[0041] Fig. 3 shows a diagram in which the pressure P of the barrier fluid (curve A) and the speed n of the rotating seal ring 3 (curve N) are plotted against time t. The speed n increases from a standstill (t = 0) during start-up of the mechanical seal assembly, causing the components of the mechanical seal 2 to heat up. At the beginning of start-up, the pressure P of the barrier fluid is briefly held constant (P1) and then reduced.

[0042] However, if the temperature T increases due to the increasing speed of the rotating components of the mechanical seal 2, the pressure P is also increased again from time t1 to achieve additional cooling of the mechanical seal components. When the speed n is reduced again (time t2), the pressure P of the barrier fluid can also be reduced again, as the temperature of the components of the mechanical seal arrangement drops again. If the speed n is relatively low, the pressure P of the barrier fluid is increased again to the initial pressure P1 to reliably ensure sealing of the bearing chamber 11.

[0043] As shown in Fig. 3, in the operating state example shown there, the rotational speed n continuously increases slightly again after reaching a low point (time t3). Starting at a threshold value n1 at time t4, the pressure P of the barrier fluid can then be reduced by the control unit 9.

[0044] Figures 4 to 6 show diagrams of a mechanical seal arrangement of a bearing arrangement according to a second embodiment.

[0045] Fig. 4 shows a diagram of the pressure P of the barrier fluid versus the peripheral speed U. Fig. 5 shows a diagram of the pressure P of the barrier fluid versus a temperature T.

[0046] Fig. 6 shows a diagram of the pressure P of the barrier fluid, the speed n of the rotating seal ring and a temperature T of one of the components of the mechanical seal 2 over time t.

[0047] In the second embodiment, the control unit 9 is configured to control the pressure P of the barrier fluid as a function of both the peripheral speed U and the temperature T of a component of the mechanical seal 2. Figures 4 and 5 show individual diagrams illustrating how the pressure behaves as a function of the peripheral speed U (Fig. 4) and the temperature T (Fig. 5), respectively. The function in Figure 5 is a quadratic function.

[0048] Fig. 6 shows a combined diagram, where the pressure P of the barrier fluid is indicated by the curve A, a curve of the peripheral speed, which depends on the rotational speed n, is marked with B and a curve of the temperature T is marked with C.

[0049] As shown in Fig. 6, the pressure P of the barrier fluid, starting from an initial pressure P1, is briefly kept constant until time t1 and then decreases linearly to a value P2. At the same time, both the rotational speed n and thus the circumferential speed U as well as the temperature T of components of the mechanical seal 2 begin to increase continuously. From a threshold value TO and at time t2*, a pressure increase begins and at time t2 in Fig. 6 the temperature reaches a maximum value T1. To prevent overheating of the bearing arrangement and the mechanical seal arrangement, the pressure P is briefly increased to a maximum pressure P3 at time t2. This supplies more barrier fluid to the mechanical seal 2, allowing cooling of the heated component(s) of the mechanical seal. The temperature then remains at a constant level from time t3 onwards, whereby the pressure P (cf. curve A in Fig.6) can be maintained at a constant level after a short period of time (time t4). Starting at a speed that exceeds the threshold value n1, the pressure P of the barrier fluid can then be reduced again, similar to the first embodiment (time t5).

[0050] As shown in the two exemplary embodiments, the invention thus enables the pressure P of the barrier fluid to be controlled as a function of various operating variables. The peripheral speed U of the rotating seal ring is used as the main operating variable. This has the advantage that a variable that is easy to determine can be used as the controlled variable for controlling the pressure level of the pressure P of the barrier fluid. As a result, leakage of barrier fluid via the sealing ring, which has previously been present in all operating states in the prior art, can be reduced by at least 50%. If a temperature T of a component of the mechanical seal 2 is additionally used for control by means of the control unit 9, the saving in barrier fluid can be increased to 90%.Since the systems in which the bearing seal and the mechanical seal assembly according to the invention are used often operate continuously, this results in extremely significant savings in operating costs. Nevertheless, the control of the valve assembly 7 can be kept relatively simple. Thus, surprisingly, by using the circumferential speed U of the rotating seal ring 3, a significant reduction in the consumption of barrier fluid can be achieved by adjusting the pressure of the barrier fluid.

[0051] In addition to the above written description of the invention, reference is hereby explicitly made to the graphic representation of the invention in the figures for its supplementary disclosure.

[0052] List of reference symbols

[0053] 1 mechanical seal arrangement

[0054] 2 mechanical seals

[0055] 3 rotating slide ring

[0056] 4 stationary sliding ring

[0057] 5 Sealing gap

[0058] 6 Barrier fluid supply system

[0059] 7 Valve arrangement

[0060] 8 Wave

[0061] 9 Control unit

[0062] 10 housings

[0063] 11 Storage room 12 Area 13 Pressure sensor

[0064] 14 Temperature sensor

[0065] 15 Speed ​​sensor

[0066] 30 sliding ring carriers

[0067] 40 Through hole in the stationary sliding ring

[0068] 60 Supply line 61 Barrier fluid source

[0069] 100 bearing arrangement

[0070] 101 Bearing A Curve of the barrier fluid pressure A1 first area of ​​curve A A2 second area of ​​curve A A3 third area of ​​curve A

[0071] B Curve of peripheral speed C Curve of temperature

[0072] D Outer diameter n Speed ​​n1 Threshold speed N Speed ​​curve P Pressure of the barrier fluid

[0073] P1 first supply pressure / outlet pressure

[0074] P2 second pressure P3 maximum pressure T temperature t time t1 first time t2 second time t2* time of beginning of pressure increase t3 third time t4 fourth time t5 fifth time

[0075] TO Threshold Temperature

[0076] T 1 maximum temperature U peripheral speed

[0077] XX Central axis

Claims

Claims 1. Mechanical seal arrangement, comprising: - a mechanical seal (2) with a rotating seal ring (3) and a stationary seal ring (4), which define a sealing gap (5) between their sliding surfaces, - a barrier fluid supply system (6) for providing barrier fluid to the mechanical seal (2), and - a valve arrangement (7) in a supply line (60) of the barrier fluid to the mechanical seal (2), wherein the valve arrangement (7) is designed to control a pressure (P) of the barrier fluid as a function of operating variables of the mechanical seal (2), and - a control unit (9) which is designed to control the valve arrangement (7) as a function of a circumferential speed (U) of the rotating slide ring (3).

2. Mechanical seal arrangement according to claim 1, wherein the control unit (9) is arranged to control the pressure (P) of the barrier fluid in such a way that the pressure (P) is constant starting from a standstill of the rotating seal ring (3) up to a first threshold value (U1) of the peripheral speed (U).

3. Mechanical seal arrangement according to claim 2, wherein the pressure (P) of the barrier fluid decreases from the first threshold value (U1) to a second threshold value (U2) of the peripheral speed (U) of the rotating seal ring (3).

4. Mechanical seal arrangement according to claim 3, wherein the pressure (P) of the barrier fluid decreases with a constant gradient.

5. Mechanical seal arrangement according to claim 3, wherein the pressure (P) of the barrier fluid decreases abruptly at the first threshold value (U1) of the peripheral speed (U).

6. Mechanical seal arrangement according to one of the preceding claims, wherein the pressure (P) of the barrier fluid increases again starting from the second threshold value (U2).

7. Mechanical seal arrangement according to claim 6, wherein the pressure (P) of the barrier fluid increases with a constant gradient.

8. Mechanical seal arrangement according to one of the preceding claims, wherein the control unit (9) is further configured to regulate the valve arrangement (7) as a function of a temperature (T) of components of the mechanical seal (2).

9. Mechanical seal arrangement according to claim 8, wherein the control unit (9) is arranged to increase the pressure (P) of the barrier fluid with increasing temperature (T) of components of the mechanical seal (2).

10. Bearing arrangement, comprising: - a warehouse (101) and - a mechanical seal arrangement according to one of the preceding claims.

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