Dry gas seal including oil-repellent surface

Abstract

A dry gas seal (100) includes a mating ring (114) coupled to a rotating shaft (102) for rotation therewith, a retaining ring (117a) fixedly attached to a compressor (104), and a carrier ring (170) movably coupled to the retaining ring. The carrier ring includes a primary ring bearing surface (202), a rear face (204), and a sealing surface (200) extending between the primary ring bearing surface and the rear face. The sealing surface includes an oleophobic coating (210) disposed thereon.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of the earlier filing dates of U.S. Provisional Application Serial No. 62 / 887837, filed on August 16, 2019, and UK Application No. 1918551.1, filed on December 16, 2019, the entire disclosures of which are incorporated herein by reference. Technical Field

[0003] Exemplary embodiments relate to the field of dry gas seals, and in particular, to dry gas seals that include one or more components having an oil repellent substance disposed thereon. Background Art

[0004] Dry gas seals are typically used to seal centrifugal compressors, which are commonly used in the transportation and distribution of gases such as natural gas. For example, in a natural gas pipeline, compressors may be placed at set intervals to increase the pressure of the gas for processing, offset the effects of flow losses along the transmission pipeline, and generally keep the gas moving toward its destination.

[0005] To move natural gas or other fluids, centrifugal compressors use rotating disks or impellers contained within a casing to increase the pressure of the process gas. The disks / impellers rotate via a rotating shaft driven by an external motor or turbine. The shaft mates with the compressor's rotor, which carries the disks / impellers. A dry gas seal surrounds the rotor at or near where it enters the casing, forming a seal that prevents process gas from escaping at this point.

[0006] Generally speaking, dry gas seals operate by providing a seal between a rotating ring and a stationary ring. The rotating ring is sometimes referred to as the "mating ring" because it mates with the rotating shaft / rotor. The rotating ring may mate with the rotor via a shaft sleeve. The stationary ring is sometimes referred to as the primary ring and does not rotate during operation.

[0007] During operation, a layer of gas is created between the two rings, forming a seal while allowing the rings to move relative to each other without contact. The gas layer is formed by process gas or seal gas injected into the dry gas seal. A groove in the rotating (mating) ring draws process gas from the outer radial edge of the mating ring to a position between the two rings. The process gas drawn into the groove is compressed as it moves toward the radially inward end (or tip) of the groove. The compressed gas creates a pressure dam that causes the primary ring to "lift off" from the mating ring, creating a running gap in the range of a few microns (e.g., 3-10 μm). To allow relative axial movement between the rings, the primary ring is typically mounted to the fixed portion of the dry gas seal via a compressible member such as a spring or other means. After lift-off, a very small amount of process gas flows through the dam area to the low-pressure side of the seal (e.g., outside the compressor), creating a controlled seal leak, and the rings operate as a non-contact seal on a thin film of gas. Summary of the Invention

[0008] In one embodiment, a dry gas seal for sealing process gas in a compressor including a rotating shaft is disclosed. The dry gas seal includes a mating ring coupled to the rotating shaft for rotation therewith, a retaining ring fixedly attached to the compressor, and a carrier ring movably coupled to the retaining ring. The carrier ring includes a primary ring bearing surface, a rear face, and a sealing surface extending between the primary ring bearing surface and the rear face. The sealing surface includes an oleophobic coating disposed thereon.

[0009] In the dry gas seal of any preceding embodiment, the seal may further include: a primary ring attached to the primary ring bearing surface.

[0010] The dry gas seal of any previous embodiment may further include a biasing member movably coupling the carrier ring to the retaining ring; and a sealing element disposed between the retaining ring and the carrier ring, the sealing element contacting the oleophobic coating disposed on the sealing surface.

[0011] In the dry gas seal of any of the previous embodiments, the sealing element may be a polymer seal or an elastomeric seal. In particular, the seal may be a lip seal.

[0012] The dry gas seal of any preceding embodiment, wherein a portion of the retaining ring includes an oleophobic coating disposed thereon.

[0013] In the dry gas seal of any preceding embodiment, the seal may further include a sleeve ring coupled to the rotating shaft and carrying the mating ring.

[0014] In any previous dry gas seal, the radially outward surface of the sleeve ring includes an oleophobic coating disposed thereon.

[0015] The dry gas seal of any embodiment may be provided in conjunction with a separator seal including an oleophobic coating disposed thereon.

[0016] In any of the previous embodiments of the dry gas seal, the seal is integrated with the compressor. In such embodiments, the dry gas seal is disposed in a bore formed in the casing of the compressor and provides process gas received through the compressor casing to the primary ring.

[0017] In a multi-stage dry gas seal embodiment, a dry gas seal for sealing process gas in a compressor including a rotating shaft is disclosed. In such a multi-stage dry gas seal, the dry gas seal includes a first-stage seal and a second-stage seal. The first-stage seal includes: a first mating ring that is coupled to the rotating shaft for rotation therewith; a first retaining ring that is fixedly attached to the compressor; and a first carrier ring that is movably coupled to the first retaining ring, the first carrier ring including a first primary ring bearing surface, a first carrier ring rear face, and a first carrier ring sealing surface extending between the first primary ring bearing surface and the first carrier ring rear face. The second-stage seal includes: a second mating ring that is coupled to the rotating shaft for rotation therewith; a second retaining ring that is fixedly attached to the compressor; and a second carrier ring that is movably coupled to the second retaining ring, the second carrier ring including a second primary ring bearing surface, a second carrier ring rear face, and a sealing surface extending between the second primary ring bearing surface and the rear face. At least one of the first carrier ring sealing surface and the second carrier ring sealing surface includes an oleophobic coating disposed thereon.

[0018] The multi-stage dry gas seal of any preceding embodiment, the seal further comprising: a first primary ring attached to the first primary ring bearing surface; and a second primary ring attached to the second primary ring bearing surface.

[0019] In the multi-stage dry gas seal of any previous embodiment, the first carrier ring sealing surface includes an oleophobic coating, the dry gas seal further comprising: a first biasing member that movably couples the first carrier ring to the first retaining ring; and a first sealing element disposed between the first retaining ring and the first carrier ring, the first sealing element contacting the oleophobic coating disposed on the first carrier ring sealing surface.

[0020] In the multi-stage dry gas seal of any preceding embodiment, the first sealing element is a polymer seal or an elastomeric seal.

[0021] In the multi-stage dry gas seal of any preceding embodiment, the second carrier ring sealing surface includes an oleophobic coating, the dry gas seal further comprising: a second biasing member movably coupling the second carrier ring to the second retaining ring; and a second sealing element disposed between the second retaining ring and the second carrier ring, the second sealing element contacting the oleophobic coating disposed on the second carrier ring sealing surface.

[0022] In the multi-stage dry gas seal of any preceding embodiment, the second sealing element is a polymer seal or an elastomeric seal.

[0023] In the multi-stage dry gas seal of any preceding embodiment, the seal further comprises: a labyrinth seal fluidly disposed between the first seal and the second seal. The labyrinth seal may include an oleophobic coating disposed thereon.

[0024] Also disclosed is a method for repairing a dry gas seal, the dry gas seal comprising: a gas inlet for admitting process gas into the dry gas seal; and a cartridge comprising a mating ring coupled to a rotating shaft for rotation therewith, a retaining ring fixedly attached to a compressor housing, and a carrier ring movably coupled to the retaining ring, the carrier ring comprising a primary ring bearing face, a rear face, and a sealing surface extending between the fixed ring bearing face and the rear face. The method comprises: removing the carrier ring from an outer housing; and replacing the carrier ring with a treated carrier ring comprising an oleophobic coating disposed thereon.

[0025] In any of the previous methods, replacing may include disposing an oleophobic coating on the sealing surface of the carrier ring to form a treated carrier ring.

[0026] In any of the previous methods, replacing may include disposing an oleophobic coating on a sealing surface of the replacement carrier ring to form a treated carrier ring.

[0027] A second dry gas seal embodiment is disclosed, which is used to seal process gas in a compressor including a rotating shaft. The seal of this second embodiment includes a mating ring coupled to the rotating shaft for rotation therewith; a retainer fixedly attachable to the compressor, the retainer including a main body and an extension extending outwardly from the main body; a push ring movably coupled to the retainer; and a sealing element disposed between the push ring and the extension. The extension may include an oleophobic coating disposed thereon.

[0028] In any previous embodiment of the second dry gas seal embodiment, the extension may include a radially outward-facing surface, an axially inward-facing surface, and a radially inward surface.

[0029] In any previous embodiment of the second dry gas seal embodiment, the oleophobic coating may be provided on the radially outward surface.

[0030] In any previous embodiment of the second dry gas seal embodiment, the oleophobic coating may be provided on one or more of the radially outward surface, the axially inward surface, and the radially inward surface.

[0031] In any previous embodiment of the second dry gas seal embodiment, the body includes an axially outward-facing surface, wherein the axially outward-facing surface includes an oleophobic coating disposed thereon.

[0032] In any previous embodiment of the second dry gas seal embodiment, the seal may further include a main ring attached to a push ring.

[0033] In any previous embodiment of the second dry gas seal embodiment, the seal may include a biasing member that movably couples the push ring to the retainer, and the sealing element contacts the oleophobic coating disposed on the extension.

[0034] In any previous embodiment of the second dry gas seal embodiment, the sealing element may be a polymer seal or an elastomeric seal.

[0035] Additional technical features and benefits are achieved through the technology of the present invention. Embodiments and aspects of the present invention are described in detail herein and are considered to be part of the claimed subject matter. For a better understanding, please refer to the detailed description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The details of the proprietary rights described herein are particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the embodiments of the present invention are apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0037] Figure 1 is a cross-sectional view of a single dry gas seal provided into a compressor housing;

[0038] Figure 2 is a cross-sectional view of a carrier ring having an oleophobic coating disposed on the outer diameter of a sealing surface;

[0039] Figure 3A and Figure 3B They are Figure 2 a cross-sectional view of a carrier ring having an oleophobic coating disposed on the rear face of the primary ring bearing surface and on the rear face of the carrier ring;

[0040] Figure 4 is a cross-sectional view of a tandem dry gas seal provided into a compressor housing;

[0041] Figure 5 is a flow chart illustrating a method of repairing a dry gas seal according to one embodiment; and

[0042] Figure 6 is a cross section of another embodiment of a dry gas seal.

[0043] The drawings depicted herein are illustrative. Many variations of the diagrams or the operations described therein may exist without departing from the spirit of the present invention. For example, the actions may be performed in a different order, or actions may be added, deleted, or modified. In addition, the term "connection" and its variations describe a connection path between two elements and do not imply a direct connection between elements without an intervening element / connection between the elements. All such variations are considered part of this specification. DETAILED DESCRIPTION

[0044] A detailed description of one or more embodiments of the disclosed apparatus and methods is presented herein by way of illustration and not limitation with reference to the accompanying figures.

[0045] Various embodiments of the present invention are described herein with reference to the accompanying drawings. Without departing from the scope of the present invention, alternative embodiments of the present invention may be designed. In the following description and in the accompanying drawings, various connections and positional relationships (e.g., above, below, adjacent, etc.) between elements are described. Unless otherwise indicated, these connections and / or positional relationships may be direct or indirect, and the present invention is not intended to be limited in this respect. Therefore, the connection of an entity may refer to a direct or indirect connection, and the positional relationship between the entities may be a direct or indirect positional relationship. In addition, the various tasks and process steps described herein may be incorporated into a more comprehensive program or process with additional steps or functions not described in detail herein.

[0046] Turning now to an overview of technology more particularly related to aspects of the present invention, one or more portions of a dry gas seal may be coated with an oleophobic coating to reduce or eliminate the adhesion of oil or water (or both) thereto.

[0047] The principle behind oleophobic coatings is based on the lotus effect. This refers to the water repellency exhibited by lotus leaves, where dirt is picked up by water droplets due to surface structure that minimizes adhesion between the water and the leaf. This phenomenon is based on changes in the droplet's contact angle, surface tension, and the work of adhesion on the surface.

[0048] In the above description of how dry gas seals operate, it was assumed that the process gas does not contain liquids. However, in some cases, the process gas (or other gas introduced into the dry gas seal) may include fluids (e.g., oil or oil byproducts) that can adhere to metal components in the dry gas seal, leading to the formation of condensate. This problem can be particularly prevalent when the process gas is not adequately heated before being introduced into the dry gas seal.

[0049] Such condensate formation increases component temperatures and, in some cases, causes a buildup of deposits due to fluid adhesion to surfaces in the dry gas seal. In extreme cases, these deposits can restrict the movement of the component and lead to failure of the entire seal. As will be better understood after reviewing the discussion of dry gas seal operation below, the restriction on the movement of the component may be referred to herein as a "hang-up." One or more embodiments herein provide a technical solution that reduces or eliminates the hang-up by providing an oleophobic coating at a location between two components of a dry gas seal, where at least one of the two components moves relative to each other. In this case, the oleophobic coating can reduce the above-mentioned deposits and, therefore, the hang-up.

[0050] Figure 1 is a partial cross-sectional view of a single non-contact dry gas seal assembly 100 (or simply, a dry gas seal assembly). However, the teachings herein are applicable to other dry gas seal configurations. As will be understood after reading the detailed description, the teachings herein are applicable to any type of dry gas seal, including but not limited to single dry gas seals, tandem dry gas seals, tandem dry gas seals with an intermediate labyrinth, triple seals with or without a labyrinth, and dual opposed dry gas seals.

[0051] At least a portion of the dry gas seal assembly 100 is positioned between a rotating compressor shaft 102 and a compressor housing 104. The rotating compressor shaft 102 is typically part of a compressor and is operably coupled to a compressor impeller (not shown) disposed in a process cavity 106 of the compressor and is supported by the housing 104 via bearings (not shown) disposed in a bearing cavity 108 of the housing 104. The rotating compressor shaft 102 is, in most cases, the rotor of the compressor and may sometimes be referred to herein simply as the rotating shaft. It should be understood that the rotating shaft need not be the rotor of the compressor itself, but may be any shaft connected to the rotor that rotates with the rotor and about which a seal needs to be provided.

[0052] The compressor housing 104 includes a bore 109 formed therein that extends between the process cavity 106 and the bearing cavity 108 and defines an annular seal chamber 112 into which the dry gas seal assembly 100 can be inserted. The process cavity 106 contains a gas (typically a hydrocarbon) compressed by the compressor. This gas is referred to herein as process gas.

[0053] A shroud 126, which may include a labyrinth seal and extends over a radially extending opening formed between the rotating shaft 102 and the compressor housing 104, may be provided to prevent process gas from freely flowing from the process chamber 106 into the bore 109. The shroud 126 is disposed within the bore 109 and, as shown, carries a labyrinth seal 128, which is configured to completely or partially prevent process gas from freely flowing from the process chamber 106 into the bore 109. The combination of the shroud 126 and labyrinth seal 128 extends over the radially extending opening formed between the rotating shaft 102 and the compressor housing 104. As shown, the shroud 126 and labyrinth seal 128 are shown as two separate pieces, but in one embodiment, they may be formed as an integrated unit. A seal, such as a radial compression seal 130, may be provided to seal between the shroud 126 / labyrinth seal 128 combination and the compressor housing 104 to ensure that process gas does not escape from the process chamber 106.

[0054] The labyrinth seal 128 includes a plurality of ridges 134 at its radially inner end. In operation, the ridges 134 are disposed proximate to an outer surface 136 of the rotating shaft 102. The plurality of ridges 134 and the corresponding intermediate cavities formed between any two consecutive ridges 134 impede the passage of gas from the process chamber 106 through the rotating shaft 102 into the seal chamber 112.

[0055] Figure 1 The dry gas seal assembly 100 shown in FIG. 1 includes a single dry gas seal, generally referred to as a first seal 110. Typically, the components of the first seal 110 are preassembled into a cartridge and then disposed in a seal chamber 112. The cartridge 118 includes a stator 117, which may be formed from one or more components and, when installed, engages each other and the compressor housing 104 in a fixed relationship. As shown, the stator 117 includes a retaining ring 117a that can be sealed to the compressor housing 104 by a sealing element such as a radial seal 140.

[0056] The barrel 118 may also include a sleeve ring 115, which may be formed from one or more parts and attached to the rotating shaft 102 so that it rotates with the rotating shaft 102. The sleeve ring 115 shown includes Figure 1 1 and 115b. In particular, the sleeve 115 includes a rotating ring 115a that is configured to contact and rotate with the rotating shaft 102. In the illustrated embodiment, a spacer sleeve 115b is included as part of the sleeve 115. Of course, the sleeve ring 115 can be formed as a unitary piece, or can include any number of pieces that are joined together or otherwise held fixed relative to each other during operation (e.g., all pieces rotate together as a unit). Although Figure 1It is not specifically shown, but it should be understood that the oleophobic coating can be applied to any radially outward surface of the sleeve ring 115. For example, the oleophobic coating can be applied to a radially outward surface of the sleeve ring, such as surface 137. This is also true in the embodiments disclosed later.

[0057] The illustrated cartridge 118 also includes what is sometimes referred to as a separator seal 119. Of course, the separator seal 119 generally need not be part of the dry gas seal and can be a separate element joined to the dry gas seal. The separator seal can be used to prevent or reduce oil or other lubricant from a bearing (not shown) disposed in the bearing cavity 108 from entering the first seal 110.

[0058] It should be understood that in certain embodiments, the separator seal 119 is not required. That is, the embodiments herein do not require the separator seal to be part of the barrel 118. Furthermore, as shown in one or more of the following embodiments, if present, the separator seal 119 need not be adjacent to the first seal 110, and one or more other seals may be provided between the first seal 110 and the separator seal 119.

[0059] Assuming that the process gas in process chamber 106 is under pressure, all components of dry gas seal assembly 100 are urged toward thrust rings 121 and 125 during operation. Axial movement of sleeve ring 115 relative to rotating shaft 102 is limited by shaft thrust ring 125, which is received in a groove in rotating shaft 102. Axial movement of stator 117 is limited by stator thrust ring 121, which is received in a groove in housing 104.

[0060] In the above example, it should be understood that the shaft thrust ring 125 can be fixed relative to the sleeve ring 115 so that the two elements rotate together. In addition, for the sake of completeness, it should be understood that other elements can be attached to the sleeve 115 to provide support or other functions, but are not specifically described herein. An optional example is a mating ring position fixing element 115c.

[0061] The sleeve ring 115 carries the rotating ring or mating ring 114 and otherwise mates it to the rotating shaft 102. That is, the sleeve ring 115 being mated to the rotating shaft 102 allows the mating ring 114 to also rotate with 102. The mating ring 114 may include one or more grooves (not shown) formed on its face.

[0062] During operation, the gas present in the process chamber 106, which may reach pressures of 6500 PSI-G (450 BAR-G) or higher, is sealed from the bearing chamber 108 and the environment by the interaction of the mating ring 114 and the main ring 116. The main ring 116 may also be referred to as a stationary ring because it does not rotate with the shaft and is therefore substantially or completely rotationally fixed relative to the housing during operation. Reference numeral 113 identifies the location of the sealing interface formed between the mating ring 114 and the main ring 116.

[0063] As will be understood by those skilled in the art, the primary ring 116 is axially movable relative to the housing 104 during operation so that a controlled distance can be maintained between the mating ring 114 and the primary ring 116 at the sealing interface 113. In the illustrated embodiment, a spring force is applied to the primary ring 116 by one or more biasing members 138 disposed between the retaining ring 117 a and the primary ring 116.

[0064] During operation, a flow of treated process gas, sometimes referred to as "seal gas," is provided into the seal chamber 112. The seal gas is generally indicated by arrow 150, which identifies the path taken by the gas through the dry gas seal assembly 100, and enters via a seal gas inlet 152. The seal gas may be at a pressure greater than the pressure of the process gas in the process chamber 106. This pressure differential prevents untreated process gas from entering the first seal 110 and allows at least some of the seal gas to re-enter the process chamber 106. Typical processing of the process gas to produce the seal gas may include one or both of filtering and heating the process gas.

[0065] The rotation of mating ring 114 due to its connection to rotating shaft 102 causes some of the sealing gas in seal chamber 112 to be drawn from the outer diameter of mating ring 114 into a groove formed therein. The shape of the groove is optimized to enhance sealing performance. As is known in the art, the groove is typically machined only to the radial midpoint of the face of mating ring 114 and has a very shallow depth of only a few microns. The groove is shaped to have a pointed tip, so that gas entering the groove is compressed due to the reduced volume at the tip. This area of slightly higher gas pressure creates a pressure dam and causes so-called "lift-off," resulting in physical separation of primary ring 116 and mating ring 114. Therefore, during operation, gas flows through the dam area (between primary ring 116 and mating ring 114) to the low-pressure side 160 of the sealing interface 113. Gas passing through the sealing interface can exit the dry gas seal assembly 100 via vent holes 174 in the compressor casing 104. As shown, vent holes 174 are in fluid communication with retaining ring vent passages 176 formed in retaining ring 117b. Of course, in different embodiments, the vent 174 may be coupled to other vent passages.

[0066] In order to allow the above-mentioned lifting, a load ring 170 is provided as a means for allowing the required movement. The load ring 170 is coupled to the retaining ring 117a by a biasing member 138. The biasing member 138 can be a single element or composed of multiple elements. In one embodiment, the biasing member 138 is composed of one or more springs.

[0067] During operation, as described above, pressure and heat within process chamber 106 may cause axial movement or expansion of rotating shaft 102. Biasing member 138 may allow primary ring 116 to maintain a constant distance between itself and mating ring 114 during operation, even when mating ring 114 moves axially due to such movement of rotating shaft 102.

[0068] To ensure that the sealing gas 150 cannot travel around the sealing interface 113, one or more radial seals may be provided. The seals may be formed from a polymer or elastomer, and one example of such a seal is a lip seal. Figure 1 , the seal is shown as a lip seal, but this is by way of example only and is not intended to be limiting. As shown, a first seal 172 may be disposed between the retaining ring 117a and the carrier ring 170. In one embodiment, the first seal 172 is fixed relative to the retaining ring 117a. The first seal 172 may be arranged so that the sealing gas 150 expands when the gas impinges on it. Thus, the first seal 172 is a so-called contact seal. When the main ring 116 moves (due to lift-off or shaft movement), the carrier ring 170 will move relative to the first seal 172.

[0069] In operation, when pressurized gas is used, it is not uncommon for at least some of the sealing gas to bypass the sealing interface 113 and travel so that it contacts an external area or diameter or the carrier ring 170. An example of such an external location is shown by the sealing surface 200 of the carrier ring 170. The escaping gas can form a liquid and eventually a solid deposit on this surface. These deposits can create a "snag" in the sliding interface between the carrier ring 170 and the first seal 172 (e.g., at the interface of the sealing surface 200 and the first seal 172). In some cases, the snag can create increased friction between the sealing surface 200 and the first seal 172, making the closing force of the biasing member 138 insufficient to overcome the friction and force the main ring 116 toward the mating ring 114 to maintain the desired clearance during operation or to close the sealing interface when the compressor is not operating.

[0070] According to one embodiment, such deposits may be reduced or avoided by applying an oleophobic coating to the sealing surface 200 .

[0071] Now refer to Figure 2, shows an example of a carrier ring 170. The carrier ring 170 includes a primary ring bearing surface 202, a rear face 204, and a sealing surface 200 extending at least partially between the primary ring bearing surface 202 and the rear face 204. Referring now to Figure 1 and Figure 2 , the main ring 116 can be attached to the main ring bearing surface 202. In this way, when the main ring 116 moves, the carrier ring 170 also moves (e.g., during lift-off). By applying the oleophobic coating 210, deposits on the sealing surface 200 can be reduced and obstruction of such movement can be avoided.

[0072] Coating 210 can be deposited in a variety of ways, including manual deposition or vacuum deposition. In operation, the coating can be selected so that it provides a contact angle of 60 degrees or greater to a liquid droplet. In one embodiment, the coating can provide such a contact angle for at least 100,000 abrasion cycles. Examples of such coatings include Aculon oleophobic coatings from Caplinq BV. Of course, other coatings can also be used.

[0073] In one embodiment, the coating 210 is configured such that it comprises a thickness t. In one embodiment, the thickness t is between 0.1 nanometers and 500 micrometers.

[0074] As will be appreciated, the location of the coating 210 is not limited to the outer diameter 220 of the sealing surface 200. For example, and with reference to Figure 3A and Figure 3B The coating 210 may be located on either or both of the rear face 310 and rear face 204 of the primary ring bearing surface 202, either alternatively or in combination. As described above, those skilled in the art will recognize that the coating 210 may be applied to any or all of the following: rear face 310 of the primary ring bearing surface 202; sealing surface 200; and rear face 204; or any combination thereof. The type and thickness of the coating on each surface may be the same as described above or may differ from one another. That is, when the coating is located on different surfaces, it may have different thicknesses or even be formed from different materials.

[0075] Re-reference Figure 1, a flow of separation gas, typically an inert gas such as nitrogen (N2), is provided to the separation seal 119 through the separation gas inlet 176. The separation gas and its path are shown by arrows 180. As shown, the separation gas 180 exits the dry gas seal assembly 100 via the vent hole 174 in the compressor housing 104. The flow of the separation gas 180 through the separation seal 119 prevents lubricating oil present in the bearing cavity 108 from entering the dry gas seal assembly 100. In one embodiment, the separation seal 119 can be a dual-segmented carbon ring seal designed to prevent bearing oil from migrating to the dry gas seal cartridge 118 on the turbine compressor equipment, such as the "Type 82" or "Type 83" seals manufactured by John Crane, Inc. of Morton Grove, Illinois.

[0076] like Figure 1 As shown in , the secondary leakage path of gas through the sealing assembly is blocked by the radial compression seal between the barrel 118 and the housing 104 or the rotating shaft 102. These seals are shown illustratively and are not mentioned separately in this article. The arrangement structure and materials used for these seals can be optimized based on the application (for example, the operating pressure of the gas and the chemical composition of the gas and / or the operating environment of the compressor). The radial seal may include an O-ring, a composite seal arrangement structure (such as an advanced polymer seal around a seal carrier member) or any other appropriate type of seal.

[0077] As described above, during operation, a flow of processed process gas (seal gas 150) is provided to one side of the sealing interface 113, and a separator gas 180 is provided to the separator seal 119. Those skilled in the art will recognize that properly controlled flow and temperature of the seal gas and separator gas through the sealing element are critical to effective sealing performance and durability. Even with such control, a large number of dry gas seals used in hydrocarbon environments may experience the above-mentioned deposits. Therefore, in one embodiment, any location in the dry gas seal assembly 100 that is contacted by the gas may benefit from the application of the coating described herein. For example, the coating may be applied to the rear face 188 of the retaining ring 117a. In addition, the coating may be placed at the location of the separator seal 119.

[0078] Figure 4 A dry gas seal assembly 400 is shown that includes a first-stage seal 401 and a second-stage seal 402. It should be understood that the combination of the first-stage seal 401 and the second-stage seal 402 forms what is commonly referred to as a tandem seal. The two seals are shown separated from each other by an optional interstage labyrinth 404. Each of the first-stage seal 401 and the second-stage seal 402 operates generally as described above.

[0079] At least a portion of the dry gas seal assembly 400 is positioned between a rotating compressor shaft 410 and a compressor housing 412, which can operate similarly to a compressor. A bore 414 (sometimes referred to as a seal chamber) is formed in the compressor housing 412, extending between a process chamber 416 and a bearing chamber 417 and defining an annular seal chamber into which the dry gas seal assembly 400 can be inserted. A shroud or labyrinth seal 424 extending over a radially extending opening formed between the rotating compressor shaft 410 and the compressor housing 412 prevents process gas from freely flowing from the process chamber 106 into the bore 414. In this embodiment, as in other embodiments, the shroud 424 can be a separate component from the dry gas seal assembly 400, or it can be part of it, depending on the context and configuration. As shown, the shroud 424 is shown as a single component including a labyrinth 427 formed thereon, but it can be composed of a combination of two or more separate components.

[0080] Figure 4 The dry gas seal assembly 400 shown in FIG. 4 includes a first-stage seal 401 and a second-stage seal 402. Typically, the components of the first-stage seal 401 and the second-stage seal 402 are pre-assembled into a cartridge 418 and then positioned within the bore 414. The cartridge 418 includes a stator 417, which may be formed from one or more components and, when installed, engages each other and the compressor housing 412 in a fixed relationship. As shown, the stator 417 includes a first retaining ring 417a and a second retaining ring 417b.

[0081] The barrel 418 may also include a sleeve ring 415, which may be formed of one or more parts and attached to the rotating shaft 410 so that it rotates with the rotating shaft 410. As described above, the rotating shaft may be a compressor shaft (rotor) or a shaft connected thereto. The rotation of the shaft 410 will cause all parts of the sleeve ring and the elements connected thereto (e.g., the main ring) to rotate. The sleeve ring 415 shown includes three parts 415a, 415b, 415c. In particular, the sleeve 415 includes a rotating ring 415a, which is configured to contact and rotate with the rotating shaft 410. In the embodiment shown, a spacer sleeve 415b is included as part of the sleeve 415. The sleeve 415 also includes a second-stage spacer 415c, which defines the interval between the first seal 401 and the second seal 401. Of course, the sleeve 415 may be formed as a unitary piece, or may include any number of pieces that are joined together or otherwise held fixed relative to each other during operation (eg, all pieces rotate together as a unit).

[0082] In contrast to the above, Figure 4The illustrated barrel 418 does not include a separate seal. This is not required, and such a seal may be provided as part of the barrel 418. Axial movement of the sleeve ring 415 relative to the shaft 410 is limited by a shaft thrust ring 425 received in a groove in the shaft 410. Axial movement of the stator 117 is also limited by a thrust ring (not shown) that cooperates with the housing 412.

[0083] The sleeve ring 415 carries the mating rings of the first seal 401 and the second seal 402 and otherwise mates them to the rotating shaft 410. That is, the sleeve ring 415 being mateable to the rotating shaft 410 allows the mating rings to also rotate together with the rotating shaft 410. The mating ring may include one or more grooves (not shown) formed on its surface.

[0084] The primary seal 401 includes a first mating ring 424 carried by the sleeve ring 415 , and the secondary seal 402 includes a second mating ring 434 carried by the sleeve ring 415 and in particular by its secondary spacer 415 c .

[0085] The primary seal 401 also includes a first primary ring 426 carried by and movably coupled to the first retaining ring 417a. To this end, the primary seal includes a first carrier ring 470 connected by a biasing member 438 provided to the first retaining ring 417a. As described above, the biasing member 438 allows the first carrier ring 470 to move relative to the shaft 410 and the first mating ring 424 so that the primary seal 401 can be operated as desired. As described above and again with reference to Figure 2 and Figures 3A to 3B The first carrier ring 470 may include a primary ring bearing surface, a rear face, and a sealing surface extending between the primary ring bearing surface and the rear face. The first primary ring 426 may be fixed to the primary ring bearing surface.

[0086] The secondary seal 402 also includes a second primary ring 436 carried by and movably coupled to the second retaining ring 417b. To this end, the secondary seal includes a second carrier ring 472 connected by a biasing member 438 provided to the first retaining ring 417a. As described above, the biasing member 438 allows the second carrier ring 472 to move relative to the shaft 410 and the second mating ring 424 so that the secondary seal 402 can be operated as desired. As described above and again with reference to Figure 2 and Figures 3A to 3B The second bearing ring 472 may include a primary ring bearing surface, a rear face, and a sealing surface extending between the primary ring bearing surface and the rear face. The second primary ring 436 may be fixed to the primary ring bearing surface.

[0087] Although not in Figure 4It is not explicitly shown, but it should be understood that any portion of, one or both of, the first and second carrier rings 470, 472 may include an oleophobic material disposed thereon.

[0088] As described above, during operation, a flow of treated process gas is provided to one side of the first-stage seal 401. Additionally, the same gas or a different gas (e.g., a barrier gas) may be applied to the second-stage seal 402. Those skilled in the art will recognize that properly controlled flow and temperature of the sealing gas and barrier gas through the seals 401, 402 are critical to effective sealing performance and durability. Even with such control, a large number of dry gas seals used in hydrocarbon environments may exhibit the deposits described above. Therefore, in one embodiment, any location in the seals 401, 402 that is contacted by the gas may benefit from the application of the coating described herein. For example, the coating may be applied to the rear faces 488a, 488b of the retaining rings 117a, 117b.

[0089] In one embodiment, an interstage labyrinth 404 may be disposed between the first stage seal 401 and the second stage seal 402. The labyrinth 404 may include an oleophobic material disposed thereon.

[0090] There are many operational dry gas seals in operation today. The teachings herein are applicable to them as well. For example, and with reference now to Figure 5 An existing dry gas seal can be repaired or maintained by removing the component, applying the oleophobic coating, and replacing it in the seal. Alternatively, the removed component can be replaced with a replacement component that is different from the component removed from the seal and includes an oleophobic coating thereon.

[0091] Although Figure 5 Several process steps are included, but it should be understood that not all steps need to be performed by a single actor. The process begins at block 502, where a dry gas seal (including a cartridge with or without a separate seal as defined above) is removed from an operating machine. Examples of such machines include compressors, but other machines also fall within this definition.

[0092] At block 504, one or more components of the cartridge are removed. This may include removing the stator, a single or all retaining rings, any or all carrier rings, and any of the sleeve rings or portions thereof. In some embodiments, the cartridge may be completely or nearly completely disassembled at this stage.

[0093] At block 506, one or more dry gas seal components may have an oleophobic coating applied to one or more surfaces thereof. This process may include applying the oleophobic coating to one or more of the removed components or the new components. In one embodiment, the oleophobic coating is provided on the sealing surface of at least one carrier ring to form a treated carrier ring.

[0094] At block 508, the cartridge is reassembled such that at least one of the components described with reference to block 406 is included therein. That is, at block 408, a dry gas seal is produced that includes at least one surface having an oleophobic coating. The cartridge can be reassembled outside of the machine or inside the machine. In one embodiment, reassembly includes including the treated carrier ring in the cartridge.

[0095] In the above discussion, certain aspects have been described in the context of dry gas seals that include a balanced diameter carrier (e.g., carrier ring 170). However, it should be understood that the use of oleophobic coatings may find application in other types of dry seals. In such aspects, Figure 5 The method can be applied to such seals.

[0096] exist Figure 6 , an alternative type of dry gas seal assembly 600 is shown, which includes a retainer 602. As shown, retainer 602 is a gland plate. In some cases, such a gland plate may be bolted or otherwise secured to the body of a compressor or other high-pressure device that requires a seal formed around a rotating shaft, such as shaft 604.

[0097] Similar to above, at least a portion of dry gas seal assembly 600 is positioned between rotating compressor shaft 604 and compressor housing 606. Rotating compressor shaft 604 is typically part of a compressor and is operably coupled to a compressor wheel (not shown) disposed in a process cavity 608 of the compressor.

[0098] The compressor housing 606 includes a hole 609 formed therein that extends between the process chamber 608 and an outer wall 610 of the housing 606. The seal assembly 600 is inserted into the hole 609. The process chamber 608 contains a gas (typically a hydrocarbon) compressed by the compressor. This gas is referred to herein as process gas and is used to create a gas film between the rotating (mating) ring and the stationary (primary) ring as described above.

[0099] The assembly 600 may also include a sleeve ring 615, which may be formed from one or more parts and attached to the rotating shaft 604 so that it rotates with the rotating shaft 604. The sleeve ring 615 of this illustration is shown as a single piece, but may include any number of pieces that are joined together or otherwise held fixed relative to each other during operation (e.g., all pieces rotate together as a unit). Figure 6 It is not specifically shown, but it should be understood that the oleophobic coating can be applied to any radially outward surface of the sleeve ring 615. For example, the oleophobic coating can be applied to a radially outward surface of the sleeve ring, such as surface 637. This is also true in the embodiments disclosed later.

[0100] Sleeve ring 615 carries and otherwise mates rotating ring or mating ring 614 to rotating shaft 604. That is, sleeve ring 615, being mated to rotating shaft 604, allows mating ring 614 to also rotate with 604. Mating ring 614 may include one or more grooves (not shown) formed on its face and operates relative to main ring 616 as described above based on process gas introduced into bore 609.

[0101] As described above, during operation, the gas present in process chamber 608, which may reach pressures of 6500 PSI-G (450 BAR-G) or higher, is sealed from the environment by the interaction of mating ring 614 and main ring 616. Main ring 616 may also be referred to as a stationary ring because it does not rotate with the shaft and is therefore substantially or completely rotationally fixed relative to housing 606 during operation.

[0102] As will be understood by those skilled in the art, the main ring 616 can move axially relative to the housing 606 during operation so that a controlled distance can be maintained between the mating ring 614 and the main ring 616 at the sealing interface 613. In the illustrated embodiment, a spring force is applied to the main ring 616 by one or more biasing members 638 attached to the retainer 602. As shown, the main ring 616 is connected to the push ring 660. A sealing element 662 provides a seal between the push ring 660 / main ring 616 combination and an extension 670 of the retaining ring 602. The seal can be formed from a polymer or elastomer and is shown as an O-ring, but other types of seals can also be used.

[0103] Extension 606 generally extends from body 668 of retainer 602. Extension 670 includes a radially outward surface 672, an axially inward surface 674, and a radially inward surface 676. The terms "inward / outward" as used for radially outward surface 672 and radially inward surface 676 are relative to shaft 604. The term "axially inward" as used for axially inward surface 674 refers to being closer to process cavity 608 than body 678 when seal assembly 600 is inserted into cavity 609. Any of radially outward surface 672, axially inward surface 674, and radially inward surface 676 may have an oleophobic coating applied thereto in the manner described above.

[0104] The body 668 may also include an axially outwardly facing surface 678. The axially outwardly facing surface 678 may also have an oleophobic coating applied thereto in the manner described above.

[0105] The term "about" is intended to include the degree of error associated with the measurement of the particular quantity based on the equipment available at the time the application was filed.

[0106] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that when used in this specification, the terms "include" and / or "comprise" specify the presence of stated features, integers, steps, operations, elements, and / or parts, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups thereof.

[0107] Although the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. Furthermore, many modifications may be made to adapt specific situations or materials to the teachings of the present disclosure without departing from the basic scope of the present disclosure. Therefore, it is intended that the present disclosure not be limited to the specific embodiments disclosed as the best mode contemplated for carrying out the present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

1. A dry gas seal for sealing process gas in a compressor including a rotating shaft, the dry gas seal comprising: a mating ring capable of being coupled to the rotating shaft to rotate therewith; a primary ring defining a sealing interface with the mating ring, a retaining ring fixedly attachable to the compressor; and a carrier ring movably coupled to the retaining ring, the carrier ring including a primary ring bearing face attached to the primary ring, a rear face, and a sealing surface extending between the primary ring bearing face and the rear face; a sealing element disposed between the retaining ring and the carrier ring, wherein the sealing surface includes an oleophobic coating disposed thereon and the oleophobic coating is exposed to a sealing gas at a pressure greater than a pressure of the gas in the compressor, and wherein the sealing element slides along the oleophobic coating and relative to the carrier ring as the carrier ring slides relative to the retaining ring.

2. The dry gas seal according to claim 1, further comprising: A biasing member movably couples the carrier ring to the retaining ring.

3. The dry gas seal according to claim 2, wherein: The sealing element is a polymer seal or an elastomeric seal.

4. The dry gas seal according to claim 2, wherein: A portion of the retaining ring includes the oleophobic coating disposed thereon.

5. The dry gas seal of claim 1 , further comprising: A sleeve ring is coupled to the rotating shaft and carries the mating ring.

6. The dry gas seal according to claim 5, wherein: The radially outward surface of the sleeve ring includes the oleophobic coating disposed thereon.

7. The dry gas seal of claim 1 in combination with a separator seal, the separator seal including the oleophobic coating disposed thereon.

8. The dry gas seal according to claim 1, which is combined with a compressor, wherein The dry gas seal is disposed in a hole formed in a housing of the compressor and provides process gas received through the compressor housing to the primary ring.

9. A dry gas seal for sealing process gas in a compressor including a rotating shaft, the dry gas seal comprising: The first-stage seal comprises: a first mating ring capable of being coupled to the rotating shaft for rotation therewith; a first primary ring forming a first sealing interface with the first mating ring; a first retaining ring fixedly attachable to the compressor; and a first carrier ring movably coupled to the first retaining ring, the first carrier ring including a first primary ring bearing face attached to the first primary ring, a first carrier ring back face, and a first carrier ring sealing surface extending between the first primary ring bearing face and the first carrier ring back face; a first sealing element disposed between the first retaining ring and the first carrier ring; wherein the first carrier ring sealing surface includes an oleophobic coating disposed thereon and the oleophobic coating is exposed to a sealing gas at a pressure greater than a pressure of gas in the compressor, and wherein the first sealing element slides along the oleophobic coating and relative to the first carrier ring as the first carrier ring slides relative to the first retaining ring; as well as The secondary seal comprises: a second mating ring capable of being coupled to the rotating shaft for rotation therewith; a second primary ring forming a second sealing interface with the second mating ring; a second retaining ring fixedly attachable to the compressor; and a second carrier ring movably coupled to the second retaining ring, the second carrier ring including a second primary ring bearing face attached to the second primary ring, a second carrier ring back face, and a second carrier ring sealing surface extending between the second primary ring bearing face and the second carrier ring back face.

10. The dry gas seal according to claim 9, wherein: The first carrier ring sealing surface includes the oleophobic coating, and the dry gas seal further includes: A first biasing member movably couples the first carrier ring to the first retaining ring.

11. The dry gas seal according to claim 10, wherein: The first sealing element is a polymer seal or an elastomeric seal.

12. The dry gas seal of claim 10, wherein: The second carrier ring sealing surface includes the oleophobic coating, the dry gas seal and further comprising: a second biasing member movably coupling the second carrier ring to the second retaining ring; and A second sealing element is disposed between the second retaining ring and the second carrier ring, the second sealing element contacting the oleophobic coating disposed on a sealing surface of the second carrier ring.

13. The dry gas seal of claim 12, wherein: The second sealing element is a polymer seal or an elastomeric seal.

14. The dry gas seal of claim 9, further comprising: A labyrinth seal is fluidly disposed between the first and second stage seals.

15. The dry gas seal of claim 14, wherein: The labyrinth seal includes the oleophobic coating disposed thereon.

16. A method of repairing a dry gas seal according to any one of claims 1 to 8, the method comprising: removing the carrier ring from the outer housing; as well as The carrier ring is replaced with a treated carrier ring including an oleophobic coating disposed thereon.

17. The method according to claim 16, wherein Replacements include: The oleophobic coating is disposed on the sealing surface of the carrier ring to form the treated carrier ring.

18. The method according to claim 16, wherein The replacement includes: The oleophobic coating is disposed on a sealing surface of a replacement carrier ring to form the treated carrier ring.

19. A dry gas seal for sealing process gas in a compressor including a rotating shaft, the dry gas seal comprising: a mating ring capable of being coupled to the rotating shaft to rotate therewith; a retainer fixedly attachable to the compressor, the retainer comprising a main body and an extension extending outwardly from the main body; and a push ring movably coupled to the retainer; a main ring attached to the push ring; a sealing element disposed between the push ring and the extension; and a biasing member movably coupling the push ring to the retainer; The extension portion includes an oleophobic coating disposed thereon, and the sealing element contacts the oleophobic coating disposed on the extension portion.

20. The dry gas seal of claim 19, wherein: The extension portion includes a radially outward surface, an axially inward surface, and a radially inward surface.

21. The dry gas seal of claim 20, wherein: The oleophobic coating is disposed on the radially outward surface.

22. The dry gas seal of claim 19, wherein: The oleophobic coating is disposed on one or more of the radially outward surface, the axially inward surface, and the radially inward surface.

23. The dry gas seal of claim 19, wherein: The body includes an axially outward-facing surface, wherein the axially outward-facing surface includes the oleophobic coating disposed thereon.

24. The dry gas seal of claim 19, wherein: The sealing element is a polymer seal or an elastomeric seal.

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