Gas-lubricated slip-ring sealing arrangement

Abstract

The invention relates to a gas-lubricated slip-ring sealing arrangement, comprising a slip-ring seal (2) with a rotating slip-ring (21) and a stationary slip-ring (22), which define a first sealing gap (23) between slip faces (21a), (22a), and comprising a sealing fluid system (100), which is designed to supply a sealing fluid to the sealing gap (23). The stationary slip-ring (22) has a through-opening (25) for conducting the sealing fluid to the sealing gap (23) of the slip-ring seal (2), wherein the through-opening (25) leads from a rear side (22b) to the slip face (22a) of the stationary slip-ring (22), wherein the sealing fluid system (100) comprises a feed line (11) for the sealing fluid, the feed line guiding the sealing fluid to a sealing fluid chamber (50) on the rear side (22b) of the stationary slip-ring (22), and a flow diode (110; 120; 130; 140) which has a first flow resistance in a first throughflow direction A from the sealing fluid system (100) to the slip-ring seal (2) and has a second flow resistance in a second throughflow direction B, which is opposed to the first throughflow direction A, from the slip-ring seal to the sealing fluid system (100), wherein the first flow resistance is smaller than the second flow resistance, and wherein the flow diode is arranged in the feed line (11) between the slip-ring seal (2) and the sealing fluid system (100).

Description

[0001] Gas lubricated mechanical seal arrangement

[0002] Description

[0003] The present invention relates to a gas-lubricated mechanical seal arrangement which has excellent sealing characteristics in all operating situations of a compressor.

[0004] Mechanical seal assemblies are known in various designs from the prior art. A mechanical seal in the mechanical seal assembly must ensure sealing under a wide variety of operating situations of the compressor. Typically, the barrier gas system is operated when the compressor is at a standstill, so that barrier gas is supplied to the mechanical seal at a slightly higher pressure than the gas to be sealed. This allows a minimal leakage of the barrier gas to reach the product chamber via the sealing gap of the mechanical seal. A special situation can arise if a so-called pressurisation of the compressor occurs, i.e. pressurisation of the compressor occurs during a start-up process. In this case, the pressure of the gas to be sealed can briefly become very high and, in particular, greater than the pressure of the barrier fluid at the mechanical seal.Large-volume seal gas lines in the seal gas system encourage this behavior. However, this results in backflow of the gas to be sealed into the seal gas line. This backflow can lead to a significant pressure drop across the sealing gap of the mechanical seal, causing the sealing gap of the mechanical seal to open. This can result in excessive leakage of the gas to be sealed, which is then directed, for example, to a return line (primary vent). This can then result in an alarm threshold being exceeded because too much gas to be sealed enters the return line. This can then lead to the compressor stopping instead of starting up as desired in order to prevent the gas to be sealed, e.g. natural gas, from flowing into the return line. Such compressors are used, for example, in compressor stations in gas pipelines.It is therefore an object of the present invention to provide a mechanical seal arrangement which, with a simple structure and simple, cost-effective manufacture, enables reliable sealing even during a start-up process of a machine to be sealed.

[0005] This object is achieved by a mechanical seal arrangement having the features of claim 1. The subclaims show preferred developments of the invention.

[0006] The mechanical seal arrangement according to the invention with the features of claim 1 has the advantage that reliable sealing is possible in all operating situations, even when starting up a compressor to be sealed by the mechanical seal arrangement. This is achieved according to the invention in that the mechanical seal arrangement comprises a mechanical seal with a rotating and a stationary seal ring, which define a sealing gap between them. The stationary seal ring has a through-opening which leads from a rear side of the stationary seal ring to a sliding surface at the sealing gap. The mechanical seal arrangement further comprises a barrier fluid system which is designed to supply a barrier fluid to the sealing gap at the mechanical seal. The barrier fluid system comprises a supply line for the barrier fluid, which leads barrier fluid to a barrier fluid chamber at the rear side of the stationary seal ring.The mechanical seal arrangement further comprises a flow diode. The flow diode is a fluidic diode through which flow can pass in a first flow direction from the barrier fluid system to the mechanical seal and through which flow can also pass in a second flow direction opposite to the first flow direction from the mechanical seal to the barrier fluid system. The flow diode has a first flow resistance in the first flow direction that is smaller than a second flow resistance in the second flow direction. The flow diode is thus particularly configured to allow a first quantity M1 to flow through in the first flow direction and a second quantity M2 to flow through in the second flow direction. The first quantity M1 is greater than the second quantity M2. The flow diode is arranged in the supply line between the barrier fluid system and the mechanical seal.

[0007] The flow diode is thus a valve device that has a lower flow resistance in a preferred direction than in an opposite direction. The flow diode is installed in the supply line such that a main flow direction of the flow diode leads from the barrier gas system to the mechanical seal, as it must be ensured that a sufficient amount of barrier gas is supplied to the mechanical seal. The first amount M1 in the main flow direction is significantly larger, preferably by at least a factor of 10, than the second amount M2 in the opposite blocking direction of the flow diode. It should be noted that, due to its design, the flow diode can therefore never completely prevent backflow in the opposite direction, but that a small amount of fluid can always flow through in the opposite direction.

[0008] Particularly preferably, the flow diode is designed as a fluidic diode without moving components. Thus, the flow diode has no moving components. This makes it particularly suitable for use in locations where maintenance is rather difficult, for example, at compressor stations of gas pipelines, which can often be several thousand kilometers long and frequently run in difficult-to-access areas.

[0009] A particularly good suitability for preventing pressure surges and leakage of the gas to be sealed during start-up of the compressor is achieved if the flow diode is preferably arranged directly at an outlet of the supply line to the barrier fluid chamber, which is located on a rear side of the stationary seal ring.

[0010] A particularly cost-effective and particularly easy-to-install design is provided by the flow diode preferably having an external thread, allowing the flow diode to be screwed into and out of the supply line. This also makes it easy to retrofit mechanical seal assemblies already in the field. This simply requires cutting a thread into the supply line, into which the flow diode with external thread can then be screwed.

[0011] Particularly preferably, the flow diode is designed as a grub screw with a tool attachment. The grub screw essentially has a cylindrical structure with an external thread, with flow passing through the grub screw through an inner region in the grub screw in the longitudinal direction of the grub screw.

[0012] Particularly preferably, the flow diode is designed such that the flow diode has a conical inlet, an orifice, and a cone with a tip directed toward the conical inlet. The tip of the cone is preferably rounded for optimal flow.

[0013] More preferably, the tip of the cone extends through the orifice plate. The cone preferably has a groove at an end facing away from the tip. The groove is preferably a partially spherical recess. This significantly reduces leakage in the direction opposite to the main flow direction.

[0014] Preferably, the cone is attached to a housing of the flow diode by means of aerodynamically shaped arms.

[0015] The aperture preferably has an undercut in the second flow direction, whereby a counterflow is generated within the flow diode.

[0016] According to a preferred alternative of the invention, the flow diode has a Tesla-like flow region with a linear through-channel and at least one flow loop. The flow loop has an inlet and an outlet arranged on the through-channel. When flowing through the flow diode in the second flow direction, the flow inside the flow diode at the outlet of the flow loop is directed substantially opposite to the flow at the inlet. Preferably, several flow loops are arranged in series in the through-channel.

[0017] The through-channel is preferably provided off-center in the flow diode.

[0018] According to a further preferred alternative of the invention, the flow diode comprises a baffle, wherein the baffle has a sharp-edged outlet in the first flow direction and a streamlined inlet in the first flow direction, e.g., a groove or rounded portion. Thus, the outlet and inlet of the baffle of the flow diode are designed differently. This also defines a main flow direction as the first flow direction, and enables a reduced flow in the opposite direction.

[0019] In addition to the aperture, the flow diode preferably also has a first fluid chamber and a second fluid chamber, with the aperture being arranged between the first and second fluid chambers in the flow diode. Preferably, at least one of the fluid chambers has a tool attachment.

[0020] The mechanical seal arrangement is preferably designed as a tandem arrangement and comprises a first mechanical seal and a second mechanical seal which are connected in series.

[0021] The second mechanical seal thus serves as a safety seal, preventing the product from escaping to the atmosphere in the event of the first mechanical seal failing. The primary vent is located between the first and second mechanical seals.

[0022] The barrier fluid system preferably further comprises a nitrogen source, in particular a nitrogen tank. A nitrogen generator is also preferably provided. This allows nitrogen to be generated from the ambient air and temporarily stored, for example, in the nitrogen tank. Both preferably, the barrier fluid system comprises a differential pressure valve configured to adjust the pressure level of the barrier fluid, which is fed to the supply line of the barrier fluid system and thus to the sliding ring.

[0023] To monitor the mechanical seal arrangement, it preferably comprises a monitoring device which is arranged in the return line and sends a fault signal, e.g. to a control center or the like, when the gas to be sealed is detected.

[0024] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0025] Fig. 1 is a schematic sectional view of a mechanical seal arrangement according to a first preferred embodiment of the invention,

[0026] Fig. 2 is a schematic sectional view of a flow diode of the mechanical seal arrangement of Fig. 1 during a flow in the first flow direction,

[0027] Fig. 3 is a schematic sectional view of a flow diode of the mechanical seal arrangement of Fig. 1 during a flow in the second flow direction,

[0028] Fig. 4 is a sectional view of a flow diode according to a second embodiment of the invention with a flow in the first flow direction,

[0029] Fig. 5 is a sectional view of a flow diode according to a second embodiment of the invention with a flow in the second flow direction,

[0030] Fig. 6 shows a flow diode of a mechanical seal arrangement according to a third embodiment of the invention and

[0031] Fig. 7 shows a flow diode of a mechanical seal arrangement according to a fourth embodiment of the invention.

[0032] Figures 1 to 3 show a gas-lubricated mechanical seal arrangement 1 according to a first embodiment of the invention.

[0033] The mechanical seal assembly 1 comprises a first mechanical seal 2 and a second mechanical seal 3. The two mechanical seals are arranged in series on a shaft 8 and seal a product chamber 40 from an atmosphere 41. This is a so-called tandem arrangement, in which the first and second mechanical seals 2, 3 are arranged in series.

[0034] The first mechanical seal 2 comprises a first rotating seal ring 21 and a first stationary seal ring 22, which define a first sealing gap 23 between their sliding surfaces. The first rotating seal ring 21 has a sliding surface 21a, and the first stationary seal ring 22 has a sliding surface 22a. Furthermore, the first mechanical seal 2 comprises a first preloading element 24, which preloads the first stationary seal ring 22 in the direction of a central axis XX of the mechanical seal assembly. The first stationary seal ring 22 is fixed to a housing 9.

[0035] The second mechanical seal 3 comprises a second rotating seal ring 31 and a second stationary seal ring 32, which define a second sealing gap 33 between their sliding surfaces. The second rotating seal ring 31 is attached to the shaft 8 by means of a second seal ring carrier 36. A second preloading element 34 preloads the second stationary seal ring 32 toward the second rotating seal ring 31.

[0036] The mechanical seal assembly 1 is a gas-lubricated mechanical seal assembly with a barrier fluid system 100, wherein a barrier fluid is provided in the form of nitrogen. For this purpose, the barrier fluid system 100 comprises a nitrogen source 13, which supplies nitrogen to the first mechanical seal 2 via a supply line 11.

[0037] As can be seen from Fig. 1, a through-hole 25 is provided in the first stationary sliding ring 22, which leads from a rear side 22b to the sliding surface 22a of the first stationary sliding ring 22. The through-hole 25 is rectilinear and parallel to the central axis XX.

[0038] Reference numeral 14 denotes a nitrogen generator which can extract nitrogen from the air and supply it to the nitrogen source 13, which is, for example, a nitrogen tank.

[0039] As can be seen from Fig. 1, the supply line opens into a barrier fluid chamber 50 which is arranged on the rear side of the first stationary sliding ring 22.

[0040] In Fig. 1, during normal operation, the flow path of the barrier fluid is shown by the arrows and leads from the nitrogen source 13 via the supply line 11 into the barrier fluid chamber 50 and to the through opening 25. The pressure of the barrier fluid is slightly higher than the pressure of the medium to be sealed in the product chamber 40, so that a small proportion of nitrogen also flows as leakage L to the product chamber 40. Since the product here is a methane-containing gas, the contamination of the product to be sealed caused by the nitrogen is negligible, particularly since the amounts involved are very small. The majority of the barrier fluid exits the radial inside of the first mechanical seal 2 at the first sealing gap 23 and then flows towards the second mechanical seal 3 and from there into a return line (primary vent) 12. The barrier fluid can then be released from the return line 12 to the atmosphere.

[0041] As can be seen from Fig. 1, a first secondary seal 4 and a centering device 5 are arranged on the first rotating slide ring 21. The first secondary seal 4 is arranged on a rear side 21b of the first rotating slide ring 21. The first rotating slide ring 21 is fastened to the shaft 8 by means of a first slide ring carrier 26. A groove 27 is provided in the first slide ring carrier 26, in which the first secondary seal 4 is arranged. In this exemplary embodiment, the first secondary seal 4 is an O-ring with a circular cross-section, which serves exclusively for sealing the rear side 21b of the first rotating slide ring 21.

[0042] The centering device 5 is an annular tension spring. The centering device 5 is arranged on a radially inner surface 21c of the first rotating seal ring 21, which is opposite a radially outer surface 21d. The centering device 5 serves to center the first rotating seal ring 21. Thus, the centering device 5 does not have a sealing function, but only a centering function. Since the centering of the first rotating seal ring is thus achieved by the centering device 5, the first secondary seal 4 can be optimally designed with regard to its sealing function on the rear side 21b.

[0043] A second secondary seal 6 and a third secondary seal 7 are arranged on a rear side 22b of the first stationary sliding ring 22. As can be seen from Fig. 1, a retaining ring 18 is provided on the rear side 22b, each of which has a groove for receiving the second and third secondary seals 6, 7. The second and third secondary seals are arranged such that a fluid path of the barrier fluid leads between the second secondary seal 6 and the third secondary seal 7. A through-opening 18a is also arranged in the retaining ring.

[0044] As can be seen from Fig. 1, the first secondary seal 4 has a first radius R1, measured from the center axis XX of the mechanical seal assembly. The second secondary seal 6 has a second radius R2, and the third secondary seal 7 has a third radius R3. As can be seen from Fig. 1, the first radius R1 lies between the second radius R2 and the third radius R3. This satisfies the inequality R2 < R1 < R3. This prevents, in particular, tilting of the seal rings of the first mechanical seal 2 relative to one another. As a result, the first sealing gap 23 can be maintained constant and with a small dimension during operation, so that the leakage L of the barrier fluid into the product can be minimized. The mechanical seal assembly 1 further comprises a control unit 10 and a differential pressure control valve 17 in the supply line 11.Furthermore, a flow sensor 15 is arranged in the supply line 11, which measures a flow rate through the supply line 11. A pressure sensor 19 is arranged on the product chamber 40 and transmits a product pressure to the control unit 10.

[0045] During normal operation, the control unit 10 is configured to adjust a pressure level in the barrier fluid chamber 50 upstream of the first mechanical seal 2 based on the pressure in the product chamber 40. This automatically results in a pressure in a second chamber 60 between the first mechanical seal 2 and the second mechanical seal 3 that is lower than the pressure in the barrier fluid chamber 50. The control unit 10 can thereby control the degree of opening or closing of the differential pressure control valve 17.

[0046] The degree of opening or closing of the differential pressure control valve 17 is determined based on the product pressure. The pressure in the barrier fluid chamber 50 is adjusted via the adjustable differential pressure control valve 17 such that the pressure in the barrier fluid chamber 50 is always greater than the product pressure in the product chamber 40. Due to the throttling of the barrier fluid path, the pressure in the barrier fluid chamber 50 is also always greater than in the second chamber 60.

[0047] This ensures zero product emissions from the product chamber 40 to the atmosphere 41. This allows the gas-lubricated tandem mechanical seal arrangement to seal off gases containing natural gas or methane, in particular. The simple and robust design of the mechanical seal arrangement 1 ensures maintenance-free operation. The second mechanical seal 3 serves as a safety seal in case the first mechanical seal 2 is damaged or fails for other reasons. Thus, the second mechanical seal 3 ensures sealing against the atmosphere 41 despite the shaft 8 continuing to rotate.

[0048] Furthermore, a monitoring device 16 is arranged in the return line 12. This monitoring device 16 monitors the function of the mechanical seal arrangement and can emit a corresponding fault signal, for example to a control center, in the event of failure or damage to the mechanical seal arrangement. This ensures that, in the event of failure of the first mechanical seal 2, the first mechanical seal 2 can be repaired as quickly as possible. The monitoring device 16 can, for example, determine damage to the first mechanical seal 2 based on a pressure level in the return line 12 and / or a flow rate of the barrier fluid. Furthermore, the mechanical seal arrangement according to the invention can operate without an intermediate seal, for example in the form of a labyrinth seal between the first mechanical seal 2 and the second mechanical seal 3.This further simplifies production and, in particular, reduces manufacturing costs. A further advantage of the mechanical seal assembly 1 according to the invention is its compact design. This makes the mechanical seal assembly 1 particularly suitable for replacing mechanical seal assemblies already installed, for example, in compressor stations of pipelines. In particular, the mechanical seal assembly 1 according to the invention is designed for very high pressures up to approximately 160 bar. 5 Pa suitable.

[0049] As can also be seen from Fig. 1, a flow diode 110 is arranged in the supply line 11. The flow diode is a fluidic diode without moving components. The flow diode 110 is arranged directly at an opening of the supply line 11 at the barrier fluid chamber 50.

[0050] The flow diode 110 is configured to allow a first quantity M1 of the barrier fluid to flow through in a first flow direction A, which corresponds to the flow direction of the barrier fluid during normal operation (main flow direction). This can be seen in detail in Fig. 2, which shows the flow diode 110 in section.

[0051] In a second flow direction B opposite to the first flow direction A, a second quantity M2 of a medium can flow back through the flow diode, so that the flow diode essentially blocks the second flow direction (cf. Fig. 3).

[0052] The first quantity M1 is much larger than the second quantity M2, preferably by at least a factor of 10. The flow diode thus has different flow resistances in the two flow directions.

[0053] As can be seen from the detailed view of Figs. 2 and 3, the flow diode 110 has an external thread 111 and is provided in the form of a grub screw and screwed into the supply line 11. The flow through the flow diode 110 occurs through the interior of the flow diode 110.

[0054] Through the external thread 111, a tool attachment 112 is screwed into the supply line 11, in which a tool can engage.

[0055] The flow diode 110 further comprises a conical inlet 113, an orifice 114, and a cone 116. An undercut 115 is provided on the orifice 114 on the side facing the barrier fluid chamber 50. The cone 116 has a rounded tip 116a and, at the end opposite the tip 116a, a groove 116b. The groove 116b is directed toward the barrier fluid chamber 50. The cone 116 is attached to a substantially cylindrical housing part 118 of the flow diode 110 by means of aerodynamically shaped arms 117, e.g., two, three, or four arms. As can be seen from Fig. 2, the cone 116 is arranged such that the tip 116a extends through the orifice 114 of the flow diode 110 in the axial direction YY of the flow diode.

[0056] Fig. 2 shows the first flow direction A through the flow diode 110 during normal operation. The barrier fluid is guided through the orifice 114 via the conical inlet 113 and, due to the flow-optimized cone 116, is accelerated toward the outlet area into the barrier fluid chamber 50. This allows a large amount of barrier fluid to be supplied to the first mechanical seal 2 through the barrier fluid system 100.

[0057] If an unusual operating situation of the mechanical seal arrangement occurs, for example when starting up a machine, in which the pressure in the product chamber 40 is greater than the barrier fluid pressure, this increased pressure propagates via the first sealing gap 23 and the through-opening 25 to the barrier fluid chamber 50. This creates a backflow from the barrier fluid chamber 50 into the supply line 11. This is indicated in Fig. 3 by the arrows B. Due to the blocking effect of the flow diode 110 in this second flow direction B, only a minimal flow through the flow diode 110 results in this direction, which is indicated by the arrows B. The undercut 115 even results in a backflow in the second flow direction upstream of the orifice plate 114, which very effectively prevents the fluid from flowing further through the flow diode 110 in the direction of the supply line 11.

[0058] Fig. 3 shows the opposite flow direction B through the flow diode 110, which is severely restricted due to the design of the flow diode 100. In particular, the undercut 115 on the aperture 114, which is a circumferential channel with an arcuate cross-section, even causes a backflow, which significantly complicates flow through the flow diode in the direction of the second flow direction B.

[0059] In conjunction with the small flow cross-section at the orifice 114, only a minimal portion of the fluid can flow out of the barrier fluid chamber 50 in the second flow direction B when a machine starts up.

[0060] This prevents a pressure drop in the barrier fluid chamber 50 from becoming too great and the first sealing gap 23 from opening too wide, which could lead to process fluid flowing out via the open sealing gap 23 into the return line 12.

[0061] By designing the flow diode 110 in the form of a grub screw, it is also easily retrofittable to mechanical seal assemblies 1 already in the field. Figures 4 and 5 show a flow diode 120 of a mechanical seal assembly according to a second embodiment of the invention. Identical or functionally equivalent parts are designated by the same reference numerals as in the first embodiment.

[0062] The flow diode 120 of the second embodiment is also designed as a grub screw with an external thread 121. Reference numeral 122 denotes a tool attachment for screwing in the flow diode 120.

[0063] The flow diode 120 has a structure similar to a Tesla valve. The flow diode 120 comprises a linear through-channel 123 and a flow loop 124 arranged on the through-channel. The flow loop has an inlet 124a and an outlet 124b, each arranged on the through-channel 123.

[0064] When flowing through the flow diode 120 of the second embodiment during normal operation, as shown in Fig. 4, a substantially continuous flow through the passage 123 results. The medium is essentially stationary in the flow loop 124. This is indicated in Fig. 4 by the arrows A, which indicate the first flow direction through the flow diode 120.

[0065] However, if the flow direction is reversed by 180°, as shown in Fig. 5, medium flows from the barrier fluid space 50 into both the through-channel 123 and the flow loop 124. In the flow loop 124, the medium is reversed by almost 180°, so that two opposing flows result inside the flow diode 120, which practically prevent large quantities of the medium from flowing through from the barrier fluid space 50 in the direction of the supply line 11.

[0066] It should be noted that it is also possible that several flow loops are provided.

[0067] Thus, the flow diode 120 also has no moving parts and is practically maintenance-free, and since the leakage is minimal and the increase in pressure in the barrier fluid chamber 50 only lasts a very short time, there is also no risk of the first mechanical seal opening and the product medium being able to escape to the atmosphere.

[0068] Fig. 6 shows a flow diode 130 with an external thread 133 according to a third embodiment of the invention. Identical or functionally identical parts are again designated by the same reference numerals as in the previous embodiments.

[0069] The flow diode 130 of the third embodiment is a diaphragm having a sharp-edged outlet 131 at the barrier fluid chamber 50 and a flow-optimized inlet 132 at the opposite end. The inlet 132 is chamfered. This results in a relatively smooth flow through the flow diode 130 of the third embodiment during normal operation shown in Fig. 6, which is represented by the arrows A, which indicate the first flow direction. For simplification reasons, the second flow direction, which is opposite to the first flow direction A, is not shown in Fig. 6.However, the sharp-edged outlet 131, at which the medium would have to flow into the aperture when flowing through the flow diode 130, prevents a smooth transition, so that vortices form here and the amount of medium flowing through in the second flow direction is much smaller than in the first flow direction A. Otherwise, this embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.

[0070] Fig. 7 shows a flow diode 140 with an external thread 145 of a mechanical seal arrangement according to a fourth exemplary embodiment of the invention. Identical or functionally identical parts are designated by the same reference numerals as in the previous exemplary embodiments. The flow diode 140 of the fourth exemplary embodiment is also an orifice plate and is constructed similarly to the flow diode in the third exemplary embodiment. The flow diode 140 has a sharp-edged outlet 141 and a broken inlet 142. The flow diode 140 further comprises a first fluid chamber 143 at the outlet 141 and a second fluid chamber 144 at the inlet 142. As can be seen from Fig. 7, the first fluid chamber 143 is directed towards the barrier fluid chamber 50 and opens into it with a sharp edge. The second fluid chamber 144 is directed towards the supply line 11 and has an aerodynamically shaped inlet edge 144a.The diameters of the first and second fluid chambers 143, 144 are chosen to be the same. Due to the sharp-edged outlet 141 and the broken inlet 142, which again has a conical bevel as in the third embodiment, the flow rates in the first flow direction A are different from those in the second flow direction B. The flow rate in the first flow direction A is significantly greater than the flow in the second flow direction B. Thus, the flow diode 140 of the fourth embodiment is also suitable as a valve without moving parts.

[0071] In addition to the above written description of the invention, reference is hereby explicitly made to the drawings in the figures for its supplementary disclosure. List of reference symbols

[0072] 1 mechanical seal arrangement

[0073] 2 first mechanical seal

[0074] 3 second mechanical seal

[0075] 4 first secondary seal

[0076] 5 Centering device

[0077] 6 second secondary seal

[0078] 7 third secondary seal

[0079] 8 Wave

[0080] 9 housings

[0081] 10 Control unit

[0082] 11 Supply line

[0083] 12 Return line (primary vent)

[0084] 13 Nitrogen source

[0085] 14 nitrogen producers

[0086] 15 Flow sensor

[0087] 16 Monitoring device

[0088] 17 adjustable differential pressure control valve

[0089] 18 Retaining ring

[0090] 18a passage opening

[0091] 19 Pressure sensor

[0092] 21 first rotating seal ring

[0093] 21a Sliding surface

[0094] 21b back

[0095] 21c radial inner surface

[0096] 21 d radial outer surface

[0097] 22 first stationary sliding ring

[0098] 22a Sliding surface

[0099] 22b back

[0100] 23 first sealing gap

[0101] 24 first prestressing element

[0102] 25 passage opening

[0103] 26 first slide ring carrier

[0104] 27 grooves

[0105] 31 second rotating seal ring

[0106] 32 second stationary sliding ring

[0107] 33 second sealing gap 34 second preload element

[0108] 36 second slide ring carrier

[0109] 40 product space

[0110] 41 Atmosphere

[0111] 50 Barrier fluid chamber

[0112] 60 second room

[0113] 100 barrier fluid system

[0114] 110 Flow diode

[0115] 111 external thread

[0116] 112 Tool approach

[0117] 113 conical inlet

[0118] 114 aperture

[0119] 115 Undercut

[0120] 116 cones

[0121] 116a Tip of the cone

[0122] 116b cove

[0123] 117 arms

[0124] 118 Housing part

[0125] 120 flow diode

[0126] 121 external thread

[0127] 122 Tool approach

[0128] 123 Through channel

[0129] 124 flow loop

[0130] 124a Inlet

[0131] 124b Outlet

[0132] 130 flow diode

[0133] 131 Outlet

[0134] 132 Inlet

[0135] 133 external thread

[0136] 140 flow diode

[0137] 141 Outlet

[0138] 142 Inlet

[0139] 143 first fluid chamber

[0140] 144 second fluid chamber

[0141] 144a Leading edge

[0142] 145 external thread

[0143] A first flow direction

[0144] B second flow direction L leakage

[0145] R1 first radius

[0146] R2 second radius

[0147] R3 third radius XX central axis

[0148] YY Axial direction of the flow diode

Claims

Claims 1. Gas-lubricated mechanical seal arrangement comprising - a mechanical seal (2) with a rotating sliding ring (21) and a stationary sliding ring (22), which define a first sealing gap (23) between sliding surfaces (21a), (22a), - a barrier fluid system (100) which is arranged to supply a barrier fluid to the sealing gap (23), - wherein the stationary sliding ring (22) has a through-opening (25) for supplying the barrier fluid to the sealing gap (23) of the mechanical seal (2), wherein the through-opening (25) leads from a rear side (22b) to the sliding surface (22a) of the stationary sliding ring (22), - wherein the barrier fluid system (100) comprises a supply line (11) for the barrier fluid, which leads the barrier fluid to a barrier fluid chamber (50) on the rear side (22b) of the stationary sliding ring (22), - a flow diode (110; 120; 130; 140) which is arranged in a first Flow direction A from the barrier fluid system (100) to the mechanical seal (2) has a first flow resistance and in a second flow direction B opposite to the first flow direction A from the mechanical seal to the barrier fluid system (100) has a second flow resistance, - wherein the first flow resistance is smaller than the second flow resistance, and - wherein the flow diode is arranged in the supply line (11) between the mechanical seal (2) and the barrier fluid system (100).

2. Mechanical seal arrangement according to claim 1, wherein the flow diode (110; 120; 130; 140) has no moving components.

3. Mechanical seal arrangement according to one of the preceding claims, wherein the flow diode (110; 120; 130; 140) is arranged directly at an outlet of the supply line (11) to the barrier fluid chamber (50).

4. Mechanical seal arrangement according to one of the preceding claims, wherein the flow diode (110; 120); (130); (140) has an external thread (111); (121); (133); (145) in order to be able to be screwed into and unscrewed from the supply line (11).

5. Mechanical seal arrangement according to claim 4, wherein the flow diode is a grub screw with a tool attachment (112; 122), and a flow through the flow diode in the axial direction YY of the flow diode through the grub screw.

6. Mechanical seal arrangement according to one of the preceding claims, wherein the flow diode (110) has a conical inlet (113), an orifice (114) and a cone (116) with a tip (116a) directed towards the conical inlet (113).

7. A mechanical seal arrangement according to claim 6, wherein the tip (116a) of the cone (116) is passed through the aperture (114).

8. A mechanical seal assembly according to claim 6 or 7, wherein the tip (116a) of the cone (116) is rounded.

9. Mechanical seal arrangement according to one of claims 6 to 8, wherein the cone (116) has a groove (116b) at an end of the cone facing away from the tip (116a).

10. Mechanical seal arrangement according to one of claims 1 to 5, wherein the flow diode (120) has a straight through-channel (123) and at least one flow loop (124), wherein the flow loop (124) has an inlet and an outlet which are arranged on the straight through-channel, wherein when flowing through the flow diode in the first flow direction A, only the through-channel (123) is flowed through and when flowing through the flow diode in the second flow direction B, the flow is guided into the through-channel (123) and the flow loop (124), wherein the flow direction at the outlet of the flow loop is directed substantially opposite to the flow direction at the inlet of the flow loop.

11. Mechanical seal arrangement according to claim 10, wherein the linear through-channel (123) is arranged off-center of the flow diode (120).

12. Mechanical seal arrangement according to one of claims 1 to 5, wherein the flow diode (130; 140) comprises an orifice, wherein the orifice has a sharp-edged outlet (131; 141) in the first flow direction A and a flow-favorable inlet (132; 142) in the first flow direction A.

13. Mechanical seal arrangement according to claim 12, wherein the flow diode (140) has a first fluid space (143) and a second fluid space (144), wherein the orifice is arranged in the flow direction between the first fluid space (143) and the second fluid space (144).

14. A mechanical seal arrangement according to claim 13, wherein at least one of the fluid spaces (143, 144) has a tool attachment to enable the flow diode to be screwed into the supply line (11).

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