High-pressure carbon ring seal

Abstract

The high-pressure carbon ring seal comprises a sealing cavity, a plurality of carbon ring assemblies, a plurality of exhaust rings, an end cover, a shaft sleeve and a sealing ring, the outer circle of the sealing cavity is a stepped shaft, the boss side of the sealing cavity is an equipment side, and the other side of the sealing cavity is an atmosphere side; the sealing cavity is installed in the equipment cavity, and the outer circle of the atmosphere side is matched with the inner wall of the equipment cavity. The carbon ring assemblies and the exhaust rings are installed in the sealing cavity at intervals. The end cover is buckled on the end face of the sealing cavity, and the carbon ring assembly and the exhaust ring are pressed and fixed at the bottom of the sealing cavity; the outer circles of the sealing cavity, the end cover and the carbon ring assembly are respectively provided with a sealing groove and a sealing ring; the shaft sleeve is sleeved on the outer circle of the equipment spindle and penetrates through the end cover, the sealing cavity, the carbon ring assembly and the inner hole of the exhaust ring. On the premise that the whole sealing length is not prolonged, the number of the carbon ring assemblies and the number of the isolation gas inlets are increased as much as possible, pressure is slowly reduced for multiple times for sealing, and the situation that sealing fails due to the fact that the carbon rings are crushed under the high-pressure working condition is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of sealing, and in particular relates to a high-pressure carbon ring seal for use in a high-pressure working compressor. Background Art

[0002] In modern industry, steam turbines, gas turbines, compressors, and blowers are increasingly used. As a leading international gas seal, carbon ring seals are gaining widespread adoption in these applications due to their ease of installation, excellent sealing, simplified maintenance, and the lack of complex external systems like lubrication and cooling. The seals in carbon ring seals are made of carbon graphite, which is inherently weaker than metals. Limited by the properties of the carbon ring material, carbon ring seals are generally only used in low- and medium-pressure applications under 100 kg. However, with technological advancements, the operating conditions of equipment like compressors are becoming increasingly complex and demanding, placing increasing demands on seals. High-pressure equipment is increasing, some exceeding 130 kg. To prevent toxic and hazardous gases from escaping the atmosphere, the equipment requires the application of a barrier gas at a pressure higher than the sealed gas to prevent leakage. This pressure exceeds the maximum pressure that graphite carbon rings can withstand.

[0003] Aside from material limitations, the carbon ring seal is a floating ring seal, a gas-throttling, non-contact seal. Its sealing principle relies on the formation of an air film of sealing gas between the floating ring and the shaft sleeve, creating a throttling pressure drop and preventing the high-pressure side from flowing to the low-pressure side. During operation, leaking gas and isolation gas from the inside of the equipment will press the carbon ring toward the low-pressure side of the carbon ring mounting groove. The carbon ring's side surface adheres tightly to the inner surface of the mounting groove, preventing the high-pressure side from leaking along the side. While the carbon ring's side surface adheres to the inner surface of the mounting groove, it also floats up and down under the action of the air film within the shaft bore, ensuring there is no contact between the inner bore and the shaft surface. This, in turn, eliminates friction between the shaft and the carbon ring, preventing damage to the shaft surface. If the medium pressure is too high, the carbon ring will be pressed tightly against the side of the mounting groove, preventing it from floating up and down with the shaft's vibrations. This can cause severe friction between the shaft and the carbon ring's inner bore, enlarging the carbon ring's inner bore. Leakage levels exceed the specified value, rendering the carbon ring ineffective. In order to reduce the pressure difference before and after a single carbon ring, the only way is to increase the number of carbon rings and add an isolation gas inlet. The isolation gas is depressurized multiple times inside the seal to reduce the pressure difference before and after the carbon ring close to the compressor side. However, due to the limitation of the total length of the equipment, it is difficult to increase the number of carbon rings and isolation gas inlets. Therefore, the conventional structure of the carbon ring seal can no longer be used normally under this working condition. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a high-pressure carbon ring seal, which can ensure that the number of carbon ring components and isolation gas inlets is increased as much as possible without extending the entire sealing length, so as to ensure that the seal is slowly depressurized multiple times, thereby avoiding the carbon ring being crushed due to excessive pressure difference before and after the carbon ring under high-pressure working conditions, resulting in seal failure.

[0005] A high-pressure carbon ring seal comprises a sealing cavity, multiple groups of carbon ring assemblies, multiple exhaust rings, an end cover, a shaft sleeve and a sealing ring, wherein the outer circle of the sealing cavity is a stepped shaft, the boss side of which is the equipment side, and the other side is the atmosphere side; the sealing cavity is installed in the equipment cavity, and the outer circle of the atmosphere side cooperates with the inner wall of the equipment cavity; multiple carbon ring assemblies and exhaust rings are installed in the sealing cavity at intervals; the end cover is closed on the end face of the sealing cavity, and the carbon ring assembly and the exhaust ring are pressed and fixed on the bottom of the sealing cavity; the outer circles of the carbon ring assembly, the exhaust ring and the end cover cooperate with the inner hole of the sealing cavity, and the outer circles of the sealing cavity, the end cover and the carbon ring assembly are all processed with sealing grooves and installed with sealing rings; the shaft sleeve is sleeved on the outer circle of the equipment main shaft and passes through the end cover, the sealing cavity, the carbon ring assembly and the inner hole of the exhaust ring.

[0006] The sealing ring includes a common standard O-type sealing ring and a special-shaped sealing ring. The special-shaped sealing ring is formed by connecting a plurality of O-type sealing rings with two or more connecting ribs.

[0007] There are multiple sealing grooves on the outer circle of the atmospheric side of the sealing cavity, and external isolation gas inlet cavities are processed between adjacent sealing grooves. The external isolation gas inlet cavities are connected to the isolation gas inlet ports opened on the equipment cavity one by one; several internal isolation gas inlet cavities are processed in the inner hole of the sealing cavity, and each internal isolation gas inlet cavity is connected to the corresponding external isolation gas inlet cavity through an air hole.

[0008] Several groups of partitions are provided in one or more of the external isolation gas inlet cavities to divide an inlet cavity into several independent spaces, which are respectively connected to different isolation gas inlets; between each group of partitions is a groove with the same width and depth as the sealing grooves on both sides, and the two ends of the groove are respectively connected to the sealing grooves on both sides to form a special-shaped sealing ring groove.

[0009] Each set of baffles includes two baffles, and each baffle is arranged axially parallel.

[0010] The inner hole of the sealing cavity is a stepped tapered structure, which is divided into three sections from the equipment side to the atmosphere side, with diameters decreasing successively, and the inner isolation gas inlet cavity is processed in the inner hole of the middle section.

[0011] The carbon ring assembly includes a friction ring, multiple tower springs, a cylindrical pin and a sealing ring. A sealing ring countersink is processed on one side of the friction ring, and multiple tower spring countersinks are evenly distributed at the bottom of the sealing ring countersink. The tower spring countersink and the sealing ring countersink of the friction ring are installed in sequence. The bottom end of the tower spring rests on the bottom of the tower spring countersink, and the top end of the tower spring is tightly attached to the back of the sealing ring. The cylindrical pin is installed at the bottom of the friction ring and inserted into the waist-shaped groove on the back of the sealing ring; a threaded hole is processed on the back of the friction ring, and a cylindrical pin is installed in the threaded hole.

[0012] The exhaust ring and the end cover are machined with countersunk holes on the atmosphere side end faces, and the cylindrical pin on the back of the friction ring is inserted into the countersunk hole to ensure that the carbon ring assembly and the exhaust ring do not rotate axially.

[0013] The atmosphere side end face of the end cover and the outer circle of the exhaust ring are both machined with air holes that pass directly through the outer circle of the shaft sleeve.

[0014] By means of the above technical solution, the present invention has at least the following beneficial effects:

[0015] 1. The present invention divides one air intake cavity into two or more cavities by adding a partition in one or more isolation air intake cavities of the sealing cavity, and installs a special-shaped sealing ring between the partitions for sealing, thereby transforming the original sealing cavity into multiple completely independent air intake spaces, increasing the number of air intake channels, and supplying isolation air of different pressures to the sealing rings in different divided areas of the special-shaped sealing ring through different isolation air inlets, so as to ensure that the number of sealing rings and isolation air inlets is increased as much as possible without extending the entire sealing length, thereby slowly reducing the pressure of the seal multiple times. The above improvements can prevent the pressure before and after the sealing ring from directly dropping from high pressure to atmospheric pressure. The pressure difference before and after the sealing ring is too large. The excessive pressure difference presses the sealing ring tightly against the exhaust ring. The friction between the sealing ring and the exhaust ring is too large. Under the action of friction, the sealing ring cannot float freely with the main shaft beating, and the inner hole of the sealing ring and the shaft sleeve are severely worn. The inner hole of the sealing ring becomes larger and loses its sealing function. The sealing ring may even be crushed due to the hardness of the material and cannot withstand the huge pressure.

[0016] 2. The present invention has a compact structure, does not require major modifications to the original equipment, and has low manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of a high-pressure carbon ring seal provided by the present invention;

[0018] Figure 2 This is a front view of the special-shaped sealing ring in the present invention;

[0019] Figure 3 It is a side view of the special-shaped sealing ring in the present invention;

[0020] Figure 4 is a schematic diagram of a sealed cavity of the present invention;

[0021] Figure 5 Schematic diagram of the carbon ring assembly structure of the present invention;

[0022] in:

[0023] 1-end cover, 11-air hole, 2-carbon ring assembly, 21-tower spring, 22-cylindrical pin, 23-friction ring, 24-sealing ring, 3-sealing cavity, 31-first sealing groove, 32-external isolation gas inlet cavity I, 33-second sealing groove, 34-atmospheric side inlet cavity, 341-external isolation gas inlet cavity II, 342-external isolation gas inlet cavity III, 35-third sealing groove, 36-internal isolation gas inlet cavity III, 37-internal isolation gas inlet cavity II, 38-internal isolation gas inlet cavity I, 39-partition, 310-special-shaped sealing groove, 4-exhaust ring, 5-equipment cavity, 51-isolation gas inlet port I, 52-isolation gas inlet port II, 53-isolation gas inlet port III, 6-sealing ring, 61-special-shaped sealing ring, 611-connecting rib, 7-screw, 8-sleeve, 9-spindle. DETAILED DESCRIPTION

[0024] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below with reference to the accompanying drawings through specific implementation methods.

[0025] like Figures 1-4 As shown, a high-pressure carbon ring seal includes a sealing cavity 3, three groups of carbon ring assemblies 2, two exhaust rings 4, an end cover 1, a sleeve 8 and a sealing ring 6. The outer circle of the sealing cavity 3 is a stepped shaft, the boss side of which is the equipment side, and the other side is the atmosphere side. The boss end face of the sealing cavity 3 is provided with a screw mounting hole, and the screw passes through the screw mounting hole to fix the sealing cavity 3 in the equipment cavity 5. The outer circle of the atmosphere side matches the inner wall of the equipment cavity 5. The three groups of carbon ring assemblies 2 and the two exhaust rings 4 are installed in the sealing cavity 3 at intervals and arranged along the axial direction of the main shaft of the equipment; the end cover 1 is fastened to the end face of the sealing cavity 3 by screws 7, and the carbon ring assembly 2 and the exhaust ring 4 are pressed and fixed to the bottom of the sealing cavity 3 to ensure that they cannot move axially. The outer circumferences of the carbon ring assembly 2, exhaust ring 4, and end cap 1 mate with the inner bore of the sealing chamber 3. Seal grooves are machined on the outer circumferences of the sealing chamber 3, end cap 1, and carbon ring assembly 2, and a sealing ring 6 is installed to prevent gas from leaking out through the gaps between the components. The shaft sleeve 8 fits over the outer circumference of the device's main shaft 9 and passes through the inner bores of the end cap 1, sealing chamber 3, carbon ring assembly 2, and exhaust ring 4.

[0026] The sealing ring 6 includes a standard O-ring and a special-shaped sealing ring 61. In this embodiment, the special-shaped sealing ring 61 is H-shaped and consists of two standard O-rings and two intermediate O-shaped connecting ribs 611. In this embodiment, standard O-rings are installed in the sealing grooves on the outer circumference of the end cap 1 and the carbon ring assembly 2.

[0027] On the outer circle of the atmospheric side of the sealing cavity 3, a first sealing groove 31, an external isolation gas inlet cavity I 32, a second sealing groove 33, an atmospheric side air intake cavity 34 and a third sealing groove 35 are processed in sequence from the equipment side to the atmospheric side. The external isolation gas inlet cavity I 32 is connected to the isolation gas inlet port I 51 opened on the equipment cavity 5. Two groups of partitions 39 are arranged in the atmospheric side air intake cavity 34, each group includes two partitions 39, and the four partitions 39 are arranged axially in parallel. There is a groove with the same width and depth as the second sealing groove 33 and the third sealing groove 35 between each group of partitions 39. The two ends of the groove are respectively connected to the second sealing groove 33 and the third sealing groove 35, and together with the second sealing groove 33 and the third sealing groove 35, they form a special-shaped sealing ring groove 310. The two groups of partitions 39 divide the atmospheric side air inlet cavity 34 into two independent spaces, namely the external isolation air inlet cavity II 341 and the external isolation air inlet cavity III 342, wherein the external isolation air inlet cavity II 341 is communicated with the isolation air inlet port II 52 opened on the equipment cavity 5, and the external isolation air inlet cavity III 342 is communicated with the isolation air inlet port III 53 opened on the equipment cavity 5.

[0028] In this embodiment, an ordinary standard O-ring is installed in the first sealing groove 31, and an H-shaped special-shaped sealing ring 61 is installed in the special-shaped sealing ring groove. The two sealing rings ensure that the isolation gas introduced into each air inlet cavity will not leak along the gap between the outer circle of the sealing cavity 3 and the inner hole of the equipment cavity 5.

[0029] The inner hole of the sealing cavity 3 is a stepped tapered structure, which is divided into three sections from the equipment side to the atmosphere side, and the diameters decrease successively. The inner hole of the middle section is processed with inner isolation gas inlet cavity I 38, inner isolation gas inlet cavity II37 and inner isolation gas inlet cavity III 36 in sequence from the equipment side to the atmosphere side. Air holes 11 are provided between the outer isolation gas inlet cavity I 32 and the inner isolation gas inlet cavity I 38, the outer isolation gas inlet cavity II 341 and the inner isolation gas inlet cavity III36, and the outer isolation gas inlet cavity III 342 and the inner isolation gas inlet cavity II 37. The air holes 11 respectively introduce the isolation gas introduced from the isolation gas inlet port I 51, the isolation gas inlet port II 52 and the isolation gas inlet port III 53 into the corresponding positions of the outer circle of the end cover 1 and the exhaust ring 4.

[0030] The atmosphere side end face of the end cover 1 and the outer circle of the exhaust ring 4 are both machined with air holes 11 that pass directly through the outer circle of the shaft sleeve 8. The air holes 11 guide the isolation gas in the internal isolation gas inlet cavity I38, the internal isolation gas inlet cavity II 37 and the internal isolation gas inlet cavity III 36 to the gap between the outer circle of the shaft sleeve 8 and the inner hole of the carbon ring assembly 2.

[0031] like Figure 5As shown, the carbon ring assembly includes a friction ring 23, multiple tower springs 21, a cylindrical pin 22, and a sealing ring 24. A sealing ring countersink is machined on one side of the friction ring 23, and multiple tower spring countersinks are evenly distributed at the bottom of the sealing ring countersink. The tower springs 21 and sealing ring 24 are sequentially installed in the tower spring countersinks and sealing ring countersinks of the friction ring 23. The bottom end of the tower spring 21 rests on the bottom of the tower spring countersink, and the top end of the tower spring 21 is tightly attached to the back of the sealing ring 24. The cylindrical pin 22 is installed at the bottom of the friction ring 23 and inserted into the waist-shaped groove on the back of the sealing ring 24 to prevent the sealing ring 24 from rotating. The back of the friction ring 23 is machined with a threaded hole, and the cylindrical pin 22 is installed in the threaded hole.

[0032] The exhaust ring 4 and the end cover 1 have countersunk holes on their atmospheric side end faces, and the cylindrical pin 22 on the back of the friction ring 23 in the carbon ring assembly 2 is inserted into the countersunk hole to ensure that the carbon ring assembly 2 and the exhaust ring 4 do not rotate axially.

[0033] The working process and principle of the above-mentioned high-pressure carbon ring seal are as follows:

[0034] The device cavity is sequentially fed with isolation gas of decreasing pressure through each isolation gas inlet from the device side to the atmosphere side, wherein the isolation gas pressure fed through isolation gas inlet I is higher than the medium pressure in the device, thereby ensuring that the medium gas in the device can only flow into the device and cannot leak to the atmosphere. The isolation gas pressure fed through isolation gas inlet III is lower than the isolation gas pressure fed through isolation gas inlet I, and the isolation gas pressure fed through isolation gas inlet II is lower than the isolation gas pressure fed through isolation gas inlet III. Each time the isolation gas passes through an isolation gas inlet, the pressure is reduced from the original high pressure to a lower pressure. The pressure before and after the sealing ring 24 is reduced step by step and finally drops to atmospheric pressure.

[0035] The present application divides one air intake cavity into two or several cavities by adding a partition in one or several isolation air intake cavities of the sealing cavity 3, and processes the original ordinary standard O-ring into a special-shaped sealing ring 61: such as the H-type used in the above embodiment, that is, two O-rings are connected into a whole with two connecting ribs 611, thereby dividing the air intake groove formed by a sealing groove into two or even several separate air intake spaces, increasing the number of air intake channels, and supplying isolation gases of different pressures between the two isolation air intake cavities separated by an H-shaped special-shaped sealing ring 61 connecting rib through different isolation air inlets, so as to ensure that the number of sealing rings 24 and isolation air inlets is increased as much as possible without extending the entire sealing length, and the seal is slowly depressurized multiple times.

[0036] The above improvements can prevent the pressure before and after the sealing ring 24 from dropping suddenly from high pressure to atmospheric pressure. The pressure difference before and after the sealing ring 24 is too large. The excessive pressure difference presses the sealing ring 24 tightly against the exhaust ring. The friction between the sealing ring 24 and the exhaust ring is too large. The sealing ring 24 cannot float with the vibration of the main shaft. The inner hole of the sealing ring 24 and the shaft sleeve are severely worn. The inner hole of the sealing ring 24 becomes larger and cannot be sealed. The sealing ring 24 may even be crushed due to the hardness of the material and cannot withstand the huge pressure.

Claims

1. A high-pressure carbon ring seal, characterized by: It includes a sealing cavity, multiple groups of carbon ring components, multiple exhaust rings, end covers, shaft sleeves and sealing rings. The outer circle of the sealing cavity is a stepped shaft, the boss side of which is the equipment side, and the other side is the atmosphere side; the sealing cavity is installed in the equipment cavity, and the outer circle of the atmosphere side cooperates with the inner wall of the equipment cavity; multiple carbon ring components and exhaust rings are installed in the sealing cavity at intervals; the end cover is closed on the end face of the sealing cavity, and the carbon ring component and the exhaust ring are pressed and fixed on the bottom of the sealing cavity; the outer circle of the carbon ring component, the exhaust ring and the end cover are matched with the inner hole of the sealing cavity, and the outer circle of the sealing cavity, the end cover and the carbon ring component are all processed with sealing grooves and installed with sealing rings; the shaft sleeve is mounted on the outer circle of the equipment main shaft and passes through the end cover, the sealing cavity, the carbon ring component and the inner hole of the exhaust ring.

2. A high pressure carbon ring seal according to claim 1, characterized in that: The sealing ring includes a common standard O-type sealing ring and a special-shaped sealing ring. The special-shaped sealing ring is formed by connecting a plurality of O-type sealing rings with two or more connecting ribs.

3. A high pressure carbon ring seal according to claim 1, characterized in that: There are multiple sealing grooves on the outer circle of the atmospheric side of the sealing cavity, and external isolation gas inlet cavities are processed between adjacent sealing grooves. The external isolation gas inlet cavities are connected to the isolation gas inlet ports opened on the equipment cavity one by one; several internal isolation gas inlet cavities are processed in the inner hole of the sealing cavity, and each internal isolation gas inlet cavity is connected to the corresponding external isolation gas inlet cavity through an air hole.

4. A high pressure carbon ring seal according to claim 3, characterized in that: Several groups of partitions are provided in one or more of the external isolation gas inlet cavities to divide an inlet cavity into several independent spaces, which are respectively connected to different isolation gas inlets; between each group of partitions is a groove with the same width and depth as the sealing grooves on both sides, and the two ends of the groove are respectively connected to the sealing grooves on both sides to form a special-shaped sealing ring groove.

5. A high pressure carbon ring seal according to claim 4, characterized in that: Each set of baffles includes two baffles, and each baffle is arranged axially parallel.

6. The high-pressure carbon ring seal according to claim 1, characterized in that: The inner hole of the sealing cavity is a stepped tapered structure, which is divided into three sections from the equipment side to the atmosphere side, with diameters decreasing successively, and the inner isolation gas inlet cavity is processed in the inner hole of the middle section.

7. The high-pressure carbon ring seal according to claim 1, characterized in that: The carbon ring assembly includes a friction ring, multiple tower springs, a cylindrical pin and a sealing ring. A sealing ring countersink is processed on one side of the friction ring, and multiple tower spring countersinks are evenly distributed at the bottom of the sealing ring countersink. The tower spring countersink and the sealing ring countersink of the friction ring are installed in sequence. The bottom end of the tower spring rests on the bottom of the tower spring countersink, and the top end of the tower spring is tightly attached to the back of the sealing ring. The cylindrical pin is installed at the bottom of the friction ring and inserted into the waist-shaped groove on the back of the sealing ring; a threaded hole is processed on the back of the friction ring, and a cylindrical pin is installed in the threaded hole.

8. A high pressure carbon ring seal according to claim 7, characterized in that: The exhaust ring and the end cover are machined with countersunk holes on the atmosphere side end faces, and the cylindrical pin on the back of the friction ring is inserted into the countersunk hole to ensure that the carbon ring assembly and the exhaust ring do not rotate axially.

9. The high-pressure carbon ring seal according to claim 1, characterized in that: The atmosphere side end face of the end cover and the outer circle of the exhaust ring are both machined with air holes that pass directly through the outer circle of the shaft sleeve.

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