Abstract:
An isolation gasket for use between joined pieces in a flow line includes, for example, a flat annular metal plate having an opening formed therethrough with a sheet of dielectric material laminated to its opposing side surfaces and a groove formed on the opposing side surfaces which penetrates through the dielectric material and into the metal plate. Each groove extends completely around the opening in the gasket, and a layer of insulating material, as well as a seal element, is disposed in each of the grooves. An isolation system between joined flange pieces utilizes the isolation gasket in combination, for example, with an insulating sleeve receivable in an aligned bore of each of the joined flange pieces, an elongate metal fastener receivable in the insulating sleeve for connecting the joined flange pieces with the isolation gasket therebetween. A flat metal washer with a sheet of dielectric material laminated to one of its opposing side surfaces is receivable on the elongate metal fastener with the laminated dielectric material abutting one of the flange piece outer faces, and at least one metal spring force exerting component is also receivable on the fastener abutting the flat metal washer.

Description:
PRIORITY APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/594,396 filed Apr. 4, 2005, entitled “Isolation Gasket, System and Method of Manufacture” incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to an isolation gasket which is adapted to be interposed and compressed between joined pieces of pipe in a flow line that is operative for fluid flow therethrough without leakage. More particularly, the present invention is directed to an isolation gasket that is part of a seal system which is particularly useful in high pressure, high temperature and/or highly corrosive environments. The present seal device is specifically adapted to provide electrical isolation between joined pipe sections.  
       BACKGROUND OF THE INVENTION  
       [0003]     Seal systems using gasket devices have been used in a variety applications to prevent fluid from leaking between joined pieces. For example, a seal device is interposed and compressed between flanged end connections of a flow line wherein in-line process control equipment is to be installed. In-line process control equipment may include such things as valves, pumps, flow meters, temperature controllers, pressure controllers and the like. In addition, ends of pipe sections are provided with flanges so that the sections may be connected, end-to-end, to form the flow line. It is known to provide isolation gasket devices at the interfaces of the joined sections to prevent leakage of the fluid at the joint.  
         [0004]     Regardless of the nature of the joint, that is, whether it is between the joined sections of pipe of whether the joint is used to connect in-line process control equipment, several issues must be addressed by the gasket device and seal system. Before selecting a gasket device for a specific application, many factors must be considered. These factors include the corrosive nature of the fluid flowing through the pipe line as well as the physical characteristics of that flowing fluid. Such physical characteristics include the pressure, temperature and velocity of the fluid. Additionally, the transfer of some fluids and/or the nature of fluids can result in the build up of electrical charge across the flange. Electrical discharges caused by difference in electrical potential create two issues. On one hand, electrical discharges can damage the integrity of the seal device. There is also the danger that an electrical discharge will create a spark that can ignite a flammable or explosive fluid in the flow line.  
         [0005]     Therefore, flow line sealing systems face numerous challenges. For example, many materials which resist corrosive gases are not suitable for high pressure applications since the materials deform. Materials which are less prone to deformation, such as a graphite filled spiral wound metal seals, conduct electricity. Many materials that are used to create seal systems may melt at high temperatures, such as those that would result in a fire, so that the seal between flanges is compromised. This is an extremely dangerous situation since compromise of the seal system allows the fluid, such as a petroleum or gas product to rapidly leak from the flow line which can increase the available combustion products for such a fire, thus allowing the fire to feed upon itself.  
       SUMMARY OF THE INVENTION  
       [0006]     It is feature and advantage of the present invention to provide a new and useful isolation gasket and seal system that provides an interface between flange connections and flow line applications.  
         [0007]     It is another feature and advantage of the present invention to provide an isolation gasket that helps eliminate false readings when a flange is undergoing hydrostatic testing.  
         [0008]     It is another feature and advantage of the present invention to provide an isolation gasket that is suitable for use in fire safe applications.  
         [0009]     To achieve the stated and other features, advantages and objects, embodiments of the invention provide an isolation device for use between joined pieces in a flow line that is operative for fluid passage therethrough without leakage comprising, for example, a flat metal plate, such as a flat annular metal plate, having opposing side surfaces and an opening formed in the metal plate to allow passage of fluid therethrough. In addition, a sheet of dielectric material is disposed on at least one side surface of the metal plate, and preferably on both side surfaces of the metal plate, for example, by laminating the sheet to either or both side surfaces of the metal plate. Further, at least one groove is formed on the side surface or surfaces on which the sheet of dielectric material is disposed which penetrates through the dielectric material and into the metal plate and which extends completely around the opening formed in the metal plate, and a layer of insulating material, as well as a seal element, are disposed in each of the grooves.  
         [0010]     In embodiments of the invention in which the layers of dielectric material are disposed on both sides of the metal plate, a radial groove extending radially outwardly from the opening in the metal plate can be formed into the metal plate and into both layers of dielectric material which extends completely around the opening in the metal plate, and the radial groove can likewise have a layer of insulating material disposed therein. In further embodiments of the invention, one or more additional grooves can be formed on the side surface or surfaces on which the sheet of dielectric material is disposed which likewise penetrates through the dielectric material and into the metal plate and which extends completely around the opening and which is spaced apart from one or more other grooves formed on the same side surface or surfaces.  
         [0011]     According to embodiments of the invention, the groove or grooves formed on the side surface or surfaces on which the sheet of dielectric material is disposed can have a cross section that is, for example, a rectangular shape, an isosceles trapezoid shape, a trapezoid shape, or a parallelogram shape. In a preferred embodiment, the layer of insulating material disposed in such grooves is formed, for example, of epoxy resin, is at least 0.005 inch thick, and provides an electrical resistance of at least 2 mega ohms. According to other embodiments of the invention, the seal element disposed in such groove or grooves can be, for example, an O-ring seal element or an annular metal body seal element having, for example, a C-shaped cross-section, and the annular metal body seal element can additionally be provided with a coating of insulating material.  
         [0012]     Other embodiments of the invention provide an isolation system between joined flange pieces, each of which has an inner and an outer face, in a flow line that is operative for fluid passage therethrough without leakage which utilizing, for example, a flat metal gasket with an opening formed therein to allow fluid passage therethrough, which flat metal gasket has opposing side surfaces on which are laminated sheets of dielectric material, each of which side surfaces has portions defining a groove that penetrates through the layer of dielectric material and into the metal plate and extends completely around the opening, and each of which grooves has a layer of insulating material and a seal element disposed therein.  
         [0013]     In addition, such other embodiments involve use of the gasket in combination, for example, with at least one insulating sleeve receivable in an aligned bore formed in each of the joined flange pieces, which sleeve has a length that is substantially equal to a distance between the outer faces of the joined flange pieces with the gasket interposed therebetween. The insulating sleeve can be made, for example, of glass reinforced polymer material, epoxy material, phenolic material, or meta-aramid material. Further, such other embodiments include, for example, at least one elongate metal fastener with opposing ends, such as a headed metal bolt with threads for receiving a nut, which fastener is receivable in the insulating sleeve for connecting the joined flange pieces to one another with the flat metal gasket interposed therebetween.  
         [0014]     Such other embodiments further comprise, for example, at least one washer made wholly or partly of materials having electrical insulation properties, such as a sheet of dielectric material laminated to one side of an annular washer substrate, which washer is receivable on the elongate metal fastener with the electrical insulation material abutting one of the flange piece outer faces. Such other embodiments can also include, for example, at least one spring force exerting component, such as a Belleville washer, receivable on the elongate metal fastener abutting the electrically insulated washer.  
         [0015]     Still another embodiment of the isolation device for embodiments of the invention comprise a flat metal plate having opposing side surfaces and an opening formed therein to allow fluid passage therethrough, a layer of dielectric material disposed on one or both of the opposing side surfaces, at least one groove formed on the side surface or surfaces on which the sheet of dielectric material is disposed which penetrates through the dielectric material and into the metal plate and which extends completely around the opening formed in the metal plate, and an annular metal seal element coated with an insulating material disposed in the groove.  
         [0016]     These and other objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become more apparent to those skilled in the art upon examination of the following detailed description, or may be learned from practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a side view in elevation and partial cross-section showing the isolation gasket and sealing system according to a first exemplary embodiment of the present invention;  
         [0018]      FIG. 2  is an enlarged side view in partial cross-section showing a representative nut and bolt set used with various insulating components for electrically isolating a flange joint for embodiments of the invention;  
         [0019]      FIG. 3  is a perspective view of an isolation gasket according to the first exemplary embodiment of the present invention;  
         [0020]      FIG. 4  is an exploded cross-sectional view of the isolation gasket of  FIG. 3  for embodiments of the invention;  
         [0021]      FIG. 5  is an enlarged cross-sectional view of one of the seal grooves of the isolation gasket of  FIGS. 3 and 4  for embodiments of the invention;  
         [0022]      FIG. 6  is a front view in elevation, partially broken away of an example of one type of insulating washer that could be used with the seal system according to embodiments of the invention;  
         [0023]      FIG. 7  is a cross-sectional view of an edge of an example of one type of insulating washer of  FIG. 6  for embodiments of the invention;  
         [0024]      FIG. 8  is a front view in elevation of a Belleville washer that can be used with alternate embodiments of the isolation system of the present invention;  
         [0025]      FIG. 9  is a cross-sectional view taken about lines  9 - 9  of  FIG. 8 ;  
         [0026]      FIG. 10  is cross-sectional view of a portion of an isolation gasket according to a second exemplary embodiment of the present invention;  
         [0027]     FIGS.  11 ( a )- 11 ( d ) are cross-sectional views diagramming various groove cross-sections that may be used with the isolation gaskets of embodiments of the present invention; and  
         [0028]      FIG. 12  is a cross-sectional view partially broken away of an isolation gasket according to a third exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0029]     Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not as a limitation of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations that come within the scope of the invention.  
         [0030]     The present invention is generally directed to an isolation gasket adapted to be used between two flanges in a flow line application. Such flanges may be the flange connection between two sections of pipeline which are connected in end-to-end relation. Alternatively, such flanges may be those used to connect monitoring equipment to the flow line.  
         [0031]     Accordingly, such a flange connection will be introduced in reference to the end-to-end connection of a pair of pipeline sections, but it should be clearly understood that the present invention is not limited to such applications. Thus, for example, as is shown in  FIG. 1 , an isolation gasket  10  is located in a flange connection  12  between two pipe sections  14  in a flow line application. Each of pipe sections  14  includes flanges  16  which may be placed in confronting relationship with gasket  10  therebetween. Flanges  16  are provided with bores  20  which align with one another so that flanges  16  may be connected by nut and bolt sets  18 , as is known in the art.  
         [0032]     With continued reference to  FIG. 1 , and with further reference to  FIG. 2 , it may be seen that electrical isolation between flanges  16  is accomplished by a plurality of different components associated with each aligned pair of bores  20 . Here, a pair of aligned bores  20  is provided with a sleeve  22  constructed, for example, of a glass reinforced polymer although other materials, such as epoxy, phenolic and nomex materials may be suitably employed. Sleeve  22  is dimensioned to have a length that is about the same as the distance between outer surfaces  24  of flanges  16  and the thickness of gasket  10  interposed therebetween. Once sleeve  22  has been inserted into a pair of aligned bores  20 , insulating washers, as described more thoroughly below, are placed on either side of bores  20  on outer surfaces  24  of flanges  16 . Metal washers  28 , which can take the form of a spring force exerting component such as a Belleville washer, are then positioned against washer  26  and bolt  30  is passed through the washers and sleeve  22  after which it is secured by nuts  32 . This assembly is undertaken for each of the aligned bores  20  after which nuts  32  may be tightened to compress gasket  10  at a desired pressure.  
         [0033]     The present invention contemplates both improvements to isolation gasket  10  as well as to the use of insulating washer  26 . To this end, as is illustrated in  FIGS. 3-5 , the construction of isolation gasket  10  may be appreciated in greater detail. Here, it may be seen that isolation gasket  10  includes the gasket body  38  formed by a flat annular metal plate  40  having an opening  44  therethrough to allow fluid passage in a flow line application. Dielectric linings  42  are laminated on each outer surface of metal plate  40 , as is well known in the art. As is seen in  FIG. 4 , a pair of grooves  46  and  48  are formed in the opposite surfaces of gasket body  38  with each of these grooves penetrating through the dielectric linings  42  and into metal plate  40 . Groove  46 , as illustrated, has a larger diameter than groove  48  so that grooves  42  and  48  are radially offset from one another relative to opening  44 . Suitable seals  50  and  52  are sized and adapted to be nested in respective grooves  46  and  48 .  
         [0034]     An improvement provided by the present invention is illustrated in  FIG. 5  with respect to groove  46 , although it should be understood that groove  48  is similarly treated. As is illustrated in  FIG. 5 , groove  46  has a layer  54  of insulating material placed therein with this insulating material being approximately 0.005 inches thick so as to provide a resistance of approximately 2 mega ohms. Layer  54  is formed by any suitable epoxy resin having such resistance characteristics. In manufacture, after grooves are machined in gasket body  38 , this epoxy resin may be sprayed, painted or otherwise applied and then cured to produce the desired coating.  
         [0035]     Coatings  54  have been found to be an improvement over existing isolation gaskets, especially during conditions of hydrostatic testing. When hydrostatic testing is undertaken, it is possible for water to infiltrate grooves  46  and  48  thus providing an electrical short between flanges  16  at flange connection  12 . Such an electrical short can indicate a failure of the system since electrical conductivity can cause unwarranted electrolysis or corrosion of the flange joint. Moreover, many fluids in the flow line, such as petroleum products, may contain water, and electrical shorting can lead to degradation of the flange joint.  
         [0036]     As noted above, the isolation gasket system according to the present invention utilizes insulation washers  26  and metal washers  28 . A representative insulating washer  26  is illustrated in  FIGS. 6 and 7 . Here, each insulating washer  26  is formed by a metal annulus  60  of any suitable material. A glass reinforced epoxy laminate, similar to dielectric linings  42 , is laminated onto the washer. This glass reinforced epoxy laminate layer  62  may be approximately 0.015 inches thick. In use, laminate layer  62  is placed against the outer surface  24  of a respective flange  16  and pressure is applied thereto by way of nuts  32  acting through metal washers  28  which are placed in abutment with metal annulus  60 . While the glass reinforced epoxy laminated onto a metal annulus  60  is an example of an insulating washer, any washer that provides complete electrical isolation, for example, can be used as well.  FIGS. 8 and 9  illustrate an example of a Belleville washer that can be used in alternate embodiments of the invention.  
         [0037]     In the past, insulating washers have been used wherein such insulating washers are formed by a substantial thickness of insulating material. This material has had some drawbacks since the insulating material is, itself, relatively soft and is subject to deformation upon the application of higher pressures. Moreover, in the event of a fire, such washers either burn or melt which sufficiently loosens the flange connection allowing the flow line products to leak. Where such materials are petroleum products, this can lead to a catastrophic fire.  
         [0038]      FIG. 10  illustrates a modification to the gasket body  38  according to the first exemplary embodiment of the present invention. Here, an isolation gasket  110  is provided with a gasket body  138  formed by a flat annular metal plate  140  that has dielectric linings  142  laminated thereon. Grooves  146  and  148  are again machined through dielectric linings  142  and into metal core  140 . In this embodiment, however, a radial groove or channel  170  extends radially outwardly from opening  144  with this radial channel  170  being formed into both of layers  142  and metal core  140 . Channel  170  is then filled with an insulating epoxy resin of the type similar to that used in grooves  146  and  148 . By providing this channel and filling the channel with insulating material, such structure helps prevent electrical arching across the gasket and therefore reduces the risk of corrosion.  
         [0039]     With reference now to FIGS.  11 ( a )- 11 ( d ), it should be appreciated that various configurations of grooves, such as grooves  46  and  48  may be employed with the present invention. For example, in  FIG. 11 ( a ) groove  80  is a rectangular cross-section groove formed through dielectric material  42  and into metal core  40 . Groove  80  is then coated with the insulating layer  54 , as described above.  FIG. 11 ( b ) provides a groove  82  that is a trapezoidal dovetail configuration. Groove  82  is again cut through dielectric layer  42  and into metal core  40  and is coated with insulative lining  54 . In  FIG. 11 ( c ), groove  84  has the cross-section of a parallelogram and is again formed through insulating layer  42  and into metal core  40 . It is again lined with an insulative coating  54 . finally,  FIG. 11 ( d ) illustrates a trapezoidal groove  86  having one side thereof oriented at a right angle to the base. Groove  86  is cut through dielectric layer  42  and into metal core  40 , and it is lined with insulating coating  54  described above.  
         [0040]     With reference now to  FIG. 12 , a third exemplary embodiment of an isolation gasket  210  is shown according to the present invention. Here, isolation gasket  210  includes a gasket body  238  formed by a flat metal plate  240  having dielectric linings  42  on opposite outer surfaces thereof. Gasket body  238  has an opening  244  to allow fluid flow therethrough and the flow line application. A pair of first grooves  246  and  248  are cut through dielectric layers  242  and into metal core  240  in a manner similar to that described with respect to the first embodiment of the present invention. Seals, such as O-ring seals  250  and  252  may be seated in grooves  246  and  248 , respectively, with each of grooves  246  and  248  being coated with an insulation coating  254 .  
         [0041]     In the embodiment shown in  FIG. 12 , however, a second set of grooves  256  and  258  are machined through dielectric layers  242  and into metal core  240  with each of grooves  256  and  258  being radially spaced outwardly of opening  244 . If desired, each of grooves  256  and  258  may be provided with an insulative coating  254 , all as described above. In  FIG. 12 , a pair of seals  260  and  262  are provided for insertion into grooves  256  and  258 . Here, each of seals  260  and  262  are formed by a C-shaped cross-section annular metal body  264  which is provided with a Teflon coating  266  that provides further insulation. Seals  260  and  262  allow for the application of greater compressive forces between flanges  16  and a joint connection. It should be understood, however, that by providing coatings  254  in grooves  256  and  258 , it may be possible to use a simple C-shaped metal seal without the Teflon coating. Alternatively, by providing the Teflon coating, it may be possible to eliminate coatings  254  in the grooves  256  and  258 .  
         [0042]     As will be appreciated by those skilled in the art, industries such as the oil and gas industry utilize many, many miles of connected metal pipelines that are subjected, for example, to a natural flow of current through the pipeline and across the metal-to-metal flange connections in the pipeline which causes the flange connections to corrode and build up corrosion similar to battery terminals. The isolation gasket for embodiments of the invention interrupts that current flow through a pipeline and prevents the flanges from corroding and building up corrosion in the way in which they would with a metal-to-metal seal.  
         [0043]     It is to be understood that embodiments of the invention cover a wide range of applications, including without limitation, not only insulation but also potential fire safety, such as fire sealing applications. In that regard, combinations including washers for embodiments of the invention are significant aspects of the invention because, for example, if the washer material deforms or begins to flow because of heat, the washers will let go, allowing the bolts to let go. If the bolts let go, there is no longer any compression in the joint between the two flanges in the flow line, which means the gasket no longer seals the joint.  
         [0044]     Thus, alternative embodiments of the invention can employ fastening means utilizing a component that exerts a resilient spring force on the bolt. While the Belleville washer is an example of such a component, according to such alternate embodiment, any component that continues to exert a spring force on the joint, for example, even as the bolt begins to expand with heat, can be used as well. Another aspect of such alternate embodiments is the combination of the spring force-exerting component of the fastening means with an insulating washer that has metal, such as steel, on the face abutting the spring force-exerting component and a high temperature resistant insulating material on the opposite face.  
         [0045]     It is to be further understood that a preferred method of making the gasket material for embodiments of the invention involves bonding the dielectric lining material to both sides of the metal substrate in large sheets to assure uniformity of the lamination. According to such preferred method, a water jet is thereafter utilized to cut appropriately dimensioned I.D and O.D. circles for gaskets out of the large sheets, and the grooves are formed on opposite sides of the cut-out circular gasket material, for example, with the circular gasket material mounted on a lathe. The resulting isolation gasket for embodiments of the invention has the stability and/or rigidity of a metal gasket with a stainless steel core having excellent corrosion resistance properties, while the glass reinforced epoxy laminated to the opposing surfaces of the gasket provides excellent insulating properties.  
         [0046]     As also previously noted, another important aspect of embodiments of the invention is the application of a suitable insulating material to the grooves that are formed in the gasket body. Representative examples of suitable insulating materials include silicon based materials, such as Dow Corning SE9120 cured at room temperature, and epoxy based materials, such as Shell epoxy resin EPON 828 with Shell hardener Epigure 3234 or Shell epoxy resin EPON 828 with polyamide based hardener, both cured at room temperature for 10-15 hours and thereafter at a post cure higher temperature. Preferably, the above insulating materials can be applied with a coating thickness of between 2 mil and 8 mil, for example, by pouring a viscous solution into the groove and allowing it to flow or by continuous injection gun with a rotating table.  
         [0047]     As likewise previously noted, another important aspect of embodiments of the invention is the seating of a suitable type of seal in the grooves of the gasket body. Representative examples of seal options include spring energized Teflon seals, as well as other types of O-ring or soft material as a back-up seal, or metal seals coated, for example, with a softer insulating material, such as PTFE. As similarly previously noted, a further important aspect of embodiments of the invention is the shape of the grooves formed in the gasket body. A factor in selecting one or more of the groove shapes previously described is the particular type of seal that is intended to be used. As internal pressure acts on the seal, the shape of the groove provides support for the seal and, keeps it from blowing out. Thus, a groove with a particular cross section may provide better support and enable better sealing characteristics for a particular type of seal element than a groove with a different cross section.  
         [0048]     Various preferred embodiments of the invention have been described in fulfillment of the various objects of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.