Patent Publication Number: US-2023133675-A1

Title: Gasket with electrical isolating coatings

Description:
The present application is a continuation of U.S. patent application Ser. No. 17/234,013, filed Apr. 19, 2021, which is a continuation of U.S. patent application Ser. No. 15/996,975, filed Jun. 4, 2018, which is a continuation in part of U.S. patent application Ser. No. 15/726,080, filed Oct. 5, 2017, through which it claims priority to U.S. Provisional Patent Application No. 62/404,673, filed Oct. 5, 2016, both of which are hereby incorporated by reference as if set out in full. The present application is also a continuation in part of U.S. patent application Ser. No. 29/640,610, filed Mar. 15, 2018, the disclosure of which is incorporated herein by reference as if set out in full. 
    
    
     BACKGROUND 
     Providing gaskets with electrically isolating properties is desired in a variety of different industries and applications. However, many limitations exist with respect to previously known gaskets having electrical isolating properties. 
     For example, in some cases, the electrical isolation properties of these gaskets are not high enough for a given application or industry. This may be because the material used to provide electrically isolating properties is not a high dielectric material. 
     In some instances, gaskets with electrically isolating properties are limited to lower temperature applications because they are not capable of withstanding exposure to high temperatures. In one example, gaskets with electrical isolating properties use glass reinforced epoxy (GRE). However, GRE has a maximum glass transition temperature in the range of from 250 to 350° F. When gaskets with GRE are exposed to temperatures above this range, the GRE becomes soft and rubber-like, and the GRE subsequently lacks the strength to properly support the sealing elements, thus leading to gasket failure. Additionally, GRE is typically adhered to a core of a gasket through the use of adhesive. This adhesive may fail at elevated temperatures and pressures, which can result in delamination. 
     Many gaskets incorporating materials having electrically isolating properties have larger thicknesses due to the material that is added to the core of the gasket in order to impart electrically isolating properties. Many common isolation materials have a dielectric strength value of between 400 and 800 volts/mil. Accordingly, a thick gasket is necessary to develop enough voltage resistance for common applications. These higher-thickness gaskets result in limitations on where the gaskets can be used. 
     Other problems associated with previously known gaskets having electrically isolating properties include structure complexity, limited dimensional stability, and limited chemical resistance. Thus, a need exists for an improved gasket having electrically isolating properties. 
     SUMMARY 
     Described herein are various embodiments of a gasket having electrically isolating properties. In some embodiments, the gasket includes a core gasket component having a coating or film of dielectric material provided on at least one surface of the core gasket component. In some embodiments, the coating or film comprises polyimide, ceramic, or aluminum oxide. In some embodiments, the coating or film is formed on all surfaces of the core gasket component, including on the surfaces of any grooves and/or protrusions formed in/on the axial surfaces of the core gasket component. A core gasket component fully encapsulated by the coating or film is also described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a top plan view of a gasket according to various embodiments described herein. 
         FIG.  2 A  is a cross-sectional view of the gasket shown in  FIG.  1    taken along line  2 - 2 . 
         FIG.  2 B  is a cross-sectional view of a gasket according to various embodiments described herein. 
         FIG.  2 C  is a cross-sectional view of a gasket according to various embodiments described herein. 
         FIG.  3 A  is a top plan view of a gasket according to various embodiments described herein. 
         FIG.  3 B  is a cross-sectional view of the gasket of  FIG.  3 A  along line A-A 
         FIG.  3 C  is a detail of a portion of the cross-section of  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG.  1   , a gasket  100  having improved electrically isolating properties according to various embodiments described herein is illustrated. The gasket  100  generally includes a core gasket component  110  (also referred to as a retainer) and a dielectric coating  120  formed on at least one surface of the core gasket component  110  (formed on at least the top axial surface of the core gasket component  110  as shown in  FIG.  1   ). The dielectric coating  120  may be formed on both surfaces of the core gasket component  110 . The core gasket component  110  may include one or more grooves formed in the axial surfaces of the core gasket component  110 , with each groove having a sealing element  130 ,  140  disposed therein. 
     The core gasket component  110  can generally have a disc shape such that the gasket  100  is suitable for placement between, e.g., flanges of adjacent pipe segments. The dimensions of the core gasket component  110  (e.g., outer diameter, inner diameter, thickness between axial surfaces, etc.) are generally not limited and may be selected based on the specific application in which the gasket is to be used. 
     The material of the core gasket component  110  is generally not limited provided the core gasket component  110  is suitable for use in a gasket, including meeting or exceeding the properties required for the specific application in which the gasket  100  is used. The material of the core gasket component  110  will typically be an electrically conductive material because an object of the present application is to provide an electrically isolating coating to the core gasket component. In some embodiments, the material of the core gasket component  110  is a metal. In some embodiments, the material of the core gasket component  110  is stainless steel. 
     As noted above, the core gasket component  110  may include one or more grooves formed in one or more axial surface of the core gasket component  110 . In some embodiments, the grooves are circular grooves aligned concentrically with the core gasket component  110 , though other configurations can be used. In some embodiments, the grooves formed in one axial surface are identical to the grooves formed in the opposing axial surface, though other, non-symmetric configurations are also possible. In  FIG.  1   , the core gasket component  110  includes two concentrically aligned grooves formed in at least a top axial surface of the core gasket component  110 , with each groove having a sealing element  130 ,  140  disposed therein. 
     While grooves are specifically mentioned above and throughout this document, the core gasket component  110  may include raised features in place of or in addition to grooves. Raised features can be used to, for example, lock a seal in place or serves as stress concentrators. 
     With reference now to  FIGS.  2 A- 2 C , a cross-sectional view of the gasket  100  of  FIG.  1    taken along line  2 - 2  is shown, with each of  FIGS.  2 A,  2 B, and  2 C  showing a different embodiment of the gasket  100 . In  FIG.  2 A , the dielectric coating  120  is formed on at least one surface of the core gasket component  110 ; in  FIG.  2 B , the dielectric coating  120  is formed on at least one surface of the grooves  115  formed in the core gasket component  110 ; and in  FIG.  2 C , the dielectric coating  120  is formed on all surfaces of the core gasket component  110 , including the surfaces of the grooves  115 . 
     While not shown in any of  FIGS.  2 A- 2 C , the core gasket component  110  may also include one or more features that protrude away from the axial surfaces  111  of the core gasket component  110 . In embodiments where such features are included, the dielectric coating  120  may be disposed on one or more surfaces of the raised features. 
     The specific number of grooves  115  provided in the core gasket component  110  is not limited. Furthermore, the cross-sectional shape, depth, width, and placement (e.g., radial distance away from the inner diameter) of each groove is generally not limited. As shown in  FIGS.  2 A- 2 C , two grooves  115  are included in each axial surface  111 , the grooves  115  have a generally square cross-sectional shape, the grooves  115  are located in close proximity to the inner diameter of the core gasket component  110 , and the grooves  115  formed in one axial surface are identical in shape, depth, and location to the grooves  115  formed in the opposing axial surface. 
     In some embodiments, the grooves  115  formed in the core gasket component  110  are used as sealing grooves. These sealing grooves are configured such that one or more sealing elements can be disposed within the sealing grooves  115 . Any type of sealing element can be disposed in the sealing grooves  115 , including for example E-rings, C-rings, O-rings, and spiral wound-type seals. In some embodiments, and as shown in  FIGS.  2 A- 2 C , an E-ring  130  can be disposed in the radially outer groove  115  and a lip seal  140  can be disposed in the radially inner groove  115 . 
     In some embodiments, the grooves  115  are shaped and dimensioned such that only a single sealing element fits within the groove. For example, the radially outer groove  115  can be shaped and dimensioned such that an E-ring disposed therein occupies the entirety of the groove  115  and leaves no additional space for other components, such as a compression limiter. The groove  115  can be shaped and dimensioned in this manner because in the embodiments described herein, the gasket retainer (i.e., core gasket component  110 ) itself may act as the compression limiter, thereby eliminating the need for a separate compression limiter component being incorporated into the gasket  100 . 
     The gasket  100  further includes a dielectric coating  120 . As noted above, the dielectric coating  120  is applied to at least one surface of the core gasket component  110 , either partially (such as is shown in  FIGS.  2 A and  2 B ) or completely covering the surface (such as is shown in  FIG.  2 C ) to which it is applied. As shown in  FIG.  2 C , in some embodiments, the dielectric coating  120  is applied completely to every surface of the core gasket component  110 , including the surfaces of any grooves  115  (and/or raised features) formed in/on the core gasket component  110 . In other words, the dielectric coating  120  can be formed on the core gasket component  110  so as to fully envelope the core gasket component  110 . In this manner, this dielectric coating  120  can electrically isolate the metallic core gasket component  110  and increase the range of applications in which the gasket  100  can be used. 
     In some embodiments, the dielectric coating  120  formed on the one or more surfaces of the core gasket component  110  is formed with a uniform thickness, including when the dielectric coating  120  is provided on all surfaces of the core gasket component  110 . The thickness of the dielectric coating is generally not limited. In some embodiments, the thickness of the dielectric coating is in the range of less than 6 mm. In some embodiments, the thickness of the coating is 0.381 mm or less, such as 0.127 mm or less. 
     In some embodiments, the thickness of the dielectric coating  120  may vary, such as in a scenario where the thickness of the coating on the groove surfaces (or on raised feature surfaces) is less than the thickness of the coating on other surfaces (axial or radial) of the core gasket component  110 . Alternatively, the thickness of dielectric coating on groove and/or raised feature surfaces can be greater than on the other surfaces of the core gasket component  110 . The thickness of the dielectric coating can also vary from groove to groove. 
     In some embodiments, the dielectric coating  120  is polyimide, polyamide, ceramic, or aluminum oxide, with polyimide being a preferred material. 
     In some embodiments, the gasket  100 , including any coating material, is free of glass reinforced epoxy (GRE). 
     The coating  120  may be applied to the core gasket component  110  using any known technique for applying a coating to a base substrate. In some embodiments, the coating  120  is applied to the core gasket component  110  in a liquid form and then cured to form a solidified coating. In some embodiments, the curing is carried out in a continuous manner, which improves the throughput of the manufacturing process and makes the process more economically feasible. In some embodiments, the continuous curing process is carried out using a continuous infrared process or by continuously passing the core gasket component having liquid coating disposed therein through a convection oven. In some embodiments, the coating  120  is applied directly to the core gasket component  110  without the need for an intermediate adhesive or bonding layer. 
     The dielectric coating  120  being applied to all surfaces of the core gasket component  110  provides a gasket  100  that is electrically isolated from both any seals used with the gasket as well as from metallic flange surfaces that the gasket may be disposed between. 
     In some embodiments, the gasket described herein may further include an inner diameter seal, such as the inner diameter seal described in U.S. Published Application No. 2015/0276105, which application is incorporated herein by reference as if set out in full. Other inner diameter seals may also be used. 
     The gasket described herein may be thinner, seal better, improve electrical isolation, and/or provide a more robust and reliable platform for fire-safe gaskets than previously known gasket materials. The gasket material described herein also advantageously eliminates any need for glass reinforced epoxy (GRE) in the gasket material. The gasket material described herein also provides stabilized material thickness and tolerance controls. The gasket material described herein expands the operating temperatures and electrical resistance of the product and allows for entry into new spaces of development, such as steam and nuclear service. The gasket described herein also expands pressure capabilities. 
     The gasket described herein further provides high dielectric strength, permeation resistance, tight tolerance capabilities, impact resistance, strong environmental protection, improved chemical resistance, and a simplified structure (i.e., less components to the overall gasket). 
     Problems that may be solved and/or advantages that may be achieved by the gasket described herein include, but are not limited to: improving electrical isolation properties of the dielectric components of the gasket through the use of high dielectric material; reducing external corrosion through complete encapsulation of the gasket retainer; increasing temperature ranges, allowing for use in wider variety of applications where current offerings of isolating gaskets include GRE; eliminating observed problem of failure of adhesive between GRE and retainer material commonly seen at elevated temperatures and pressures; decreasing gasket thickness and thereby allowing for use in a wider variety of applications through the use of thinner dielectric materials, which allows for ease in installation; decreasing the number of gasket components and thereby reducing complexity by eliminating, e.g., a backup ring compression limiting device as what is currently seen in similar isolating gasket configuration; increasing dimensional stability through use of materials that have controlled tolerances; increasing the ability to hold tight tolerances throughout the manufacturing process; improving sealing performance through the elimination of permeation in current gasket facing material as well as providing a more dimensionally stable gasket sealing surface; reducing exposed metal and electrical conduction points by being fully encapsulated in a dielectric material; providing a variety of coatings that can be applied for gasket use in a wider variety of applications; providing the ability to vary coating thickness to accommodate different applications and flange faces; eliminating GRE from the gasket; providing coatings that allow for better sealing in the event of exposure to media that is not compatible with GRE; controlling gasket colorations to thereby allow for different colors to signify different coatings; allowing for use of varied metallic retainers; metallic retainer coated with dielectric barrier will continue to act as compression limiter in the event of fire preventing leakage due to loss of stress of the gasket or possible expansion and over compression of the seal; non-permeable coating mitigates explosive decompression in systems where drastic pressure changes can occur; and; ability to utilize conductive sealing elements such as explosive decompression resistant O-rings. 
     Advantageously, the spray coating of the dielectric material on the core gasket component has provided a thin profile for the resultant isolation gasket, which profile has a thickness or axial height of less than about 5 mm, and in some cases less than about 4.7 mm. Disadvantageously, however, gaskets having the thin profile make providing grooves for E-rings, C-rings, O-rings or the like difficult.  FIGS.  3 A- 3 C  provide a gasket  200  that allows for a thin profile but provides an adequate primary seal and secondary seal without the necessity of grooves to hold additional seal elements and/or compression limiters. 
       FIG.  3 A  shows an elevation view of a gasket  200  with a gasket core  202  (or retainer  202 ).  FIG.  3 B  shows a cross-sectional view of the gasket  200 .  FIG.  3 C  shows a detail of the cross-section of  FIG.  3 B . The gasket  200  has the gasket core  202 , as mentioned above, and an inner seal element  204 . The gasket  200  also has a C-ring  206  interspersed between the gasket core  202  and the inner seal element  204 . 
     The inner seal element  204  is typically formed from a chemically inert material, as well as a non-conducting material. While not to be considered limiting, the inner seal element  204  may be formed from polytetrafluoroethylene (PTFE) or other fluro polymers. 
     The gasket core  202  and C-ring  206  may be formed from a non-conductive material, but typically are formed of a base metal, such as, for example, stainless steel to name but one possible material. The gasket core  202  and C-ring  206  may be spray coated with the dielectric material coating  120  as described above. The dielectric coating  120  may be any of a number of materials. In some embodiments, the dielectric coating may be polyimide, polyamide, ceramic, aluminum oxide, fluoropolymers (such as, for example, PFA, PTFE, etc), and the like. It has been found that polyimide coatings work well for the technology disclosed herein. The dielectric coating  120  is may be applied as described above. 
     With reference to  FIG.  3 C , the gasket core  202  is shown having a first axial height of H 1 . The retaining ring  202  has an inner core surface  208  that has a first shape  210 . The shape  210  in this exemplary embodiment is a concave shape, which will be explained further below. The inner core surface  208  defines an inner diameter D 1  ( FIG.  2 B ) of the gasket core  202 . 
     The C-ring  206  correspondingly has an outer C-ring surface  212  that defines an outer diameter D 2 . The outer C-ring surface  212  is convex to cooperatively engage the inner core surface  208 . Other shapes of the inner core surface  208  and outer C-ring surface  212  are possible. Also, while matching shapes in this exemplary embodiment, the shapes are not necessarily reciprocal as shown. For example, the C-ring  206  may be replaced by an E-ring or other convoluted shape seal. The inner core surface  208  would be designed to wrap around the convoluted outer surface of the seal. 
     The C-ring  206  comprises an opening  214 , which is located opposite the outer C-ring surface  212 . The opening  214  defines an inner diameter D 3 . The C-ring  206  has a pair of seal arms  216  extending from the outer C-ring surface  212  to the opening  214 . The seal arms  216  have an apex  218 . The apex  218 , which is shown about midway along the seal arms  216 , has an uncompressed height of H 2 , which is greater than the axial height H 1 . When the gasket  200  is compressed between flanged surfaces, the seal arms  216  at apex  218  form a seal interface with the flanged surfaces. Moreover, the opening  214  will decrease in size causing ends  220  of the seal arms  216  to approach each other. 
     The inner seal element  204 , in this exemplary embodiment, is a pressure activated element where the inner seal element surface  222  provides a chevron shape. The inner seal element  204  has an uncompressed height of H 3 , which is greater than H 2  Other pressure activated shapes are possible. Also, the inner seal element  204  could have a flat inner seal element surface in certain embodiments. 
     The inner seal element  204  also has an outer surface  224  that defines an outer diameter D 4 , which is substantially the same as the inner diameter D 3 . An engagement protrusion  226  (or annular ridge  226 ) extends from the outer surface  224  and extends into the opening  214 . Rather than a single protrusion  226 , the protrusion may comprise multiple legs. The protrusion  226  generally has a height that is less than the size of the uncompressed opening  214  such that the protrusion  226  freely fits within the opening  214 . However, the protrusion  226  could be designed such that a snap fit or friction fit is established between the surfaces  228  of the protrusion  226  and the ends  220  of the C-ring  206 . When compressed, the ends  220  of the C-ring  206  may grip the surfaces  228  of the protrusion  226  or, in some instances, pierce the surface  228  to form a positive lock with the C-ring  206 . 
     The inner seal element  204  can be snapped into the C-ring  206  by pushing the inner seal element  204  until the protrusion  226  plasticly deforms. Once in place, the protrusion  226  would return to its original shape and extend into the opening  214 . To facilitate insertion, the inner seal element  204  may be compressed radially to make the insertion easier. For example, the inner seal element  204  may be cooled to condense and shrink the diameter of the inner seal element  204 . When returned to installation temperature (or operating temperature), the inner seal element  204  would expand as it warms to engage the C-ring  206 . 
     The technology described herein is disclosed in the context of a gasket. However, the same principles can be applied to other types of pipe isolation components. For example, the features described herein, including coating a pipe isolation component partially or fully with a dielectric material such as a polyimide, could be applied to the flanges of a monolithic isolation joint, such as the ElectrosStop® Monolithic Isolation Joint manufactured by Garlock Pipeline Technologies, Inc. in Houston Tex. 
     From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.