Patent Publication Number: US-9835252-B2

Title: Multi-elastomer seal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and benefit of U.S. application Ser. No. 12/669,037, entitled “Multi-Elastomer Seal,” filed Jan. 13, 2010, which is herein incorporated by reference in its entirety, which claims priority to and benefit of PCT Patent Application No. PCT/US2008/075620, entitled “Multi-Elastomer Seal,” filed Sep. 8, 2008, which is herein incorporated by reference in its entirety, and which claims priority to and benefit of U.S. Provisional Patent Application No. 60/972,049, entitled “Multi-Elastomer Seal”, filed on Sep. 13, 2007, which is herein incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     This invention relates to seals within a fluid system. More particularly, the present invention relates to an elastomeric seal suitable for use in the harsh environment, temperatures, and pressures of mineral extraction systems, for example. 
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Fluid systems, such as mineral extraction systems (e.g. oil and gas) and transport systems, typically include multiple segments of tubing, valves, and connectors that are sealed together by various seals. These seals are often subjected to harsh environmental conditions, such as corrosive fluids, extreme pressures, and extreme temperatures. Moreover, seals are often disposed in remote equipment, such as a marine (e.g., subsea) wellhead, which can make access and repair difficult and expensive. In mineral extraction applications, seals are typically constructed of a metal or an elastomer. Metal seals provide long-term resistance to well bore fluids, temperatures and pressures, but often rely on high installation forces and complicated design and geometry to provide reliable sealing. Elastomeric seals typically have a simple design that can be installed with low installation forces. Further, elastomeric seals may provide a seal across imperfections (e.g., damage, concentricity and ovalities) on sealing surfaces, and have larger manufacturing tolerances, concentricity and ovalities allowances. Elastomeric seals are generally formed from a single elastomer that is designed for use in a particular environment. For example, an electrometric seal including specific material may be employed based on the seal&#39;s anticipated operating temperature, pressure and chemical exposure. Accordingly, the electrometric seal is often limited to use in a given range of pressures, temperatures, surrounding chemicals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a block diagram of a multi-elastomer seal disposed in a fluid system, in accordance with embodiments of the present technique; 
         FIG. 2  is a partial cross-section of an exemplary embodiment of the multi-elastomer seal of  FIG. 1 ; 
         FIG. 3  is a plot of stiffness versus temperature for two elastomers used to form the multi-elastomer seal; and 
         FIGS. 4-23  are partial cross-sections of alternate exemplary embodiments of the multi-elastomer annular seal of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
       FIG. 1  is a partial cross-sectional view of an embodiment of a fluid system  10  having one or more seals  12  between an inner body  14  and an outer body  16 . In certain embodiments, the fluid system  10  includes a mineral extraction system for the extraction of subterranean natural resources, such as oil and gas. For example, in the illustrated embodiment, the outer body  16  includes a wellhead  18  coupled to a mineral deposit  20  via a well  22 . The inner body  14  includes a hanger  24  disposed in a wellhead bore  26  and supported by the wellhead  18 , for example. It will be appreciated that in the case of mineral extraction systems, the inner and outer bodies  14  and  16  may include any number of components, such as christmas trees, casing hangers, casing heads, casing strings, tubing hangers, tubing heads, tubing strings, running tools, blowout preventers, valves, flanges, and the like. In mineral extraction and similar systems, the seal  12  may be used with working pressures including 20,000 pounds per square inch (psi). In other words, in certain embodiments, the seal  12  may be used to isolate regions of gasses or fluids with pressure differentials across the seal  12  of 15,000 psi or greater. Further, the operating environment of such systems may include temperatures ranging from −50° F. to 350° F. 
     As discussed in further detail below, embodiments of the seal  12  generally include a plurality of elastomers. For example, the seal  12  may include different portions made of different elastomers having different characteristics, such as stiffness, chemical resistance, behavior as a function of temperature, and so forth. In some embodiments, the plurality of elastomers may be formed into a single body. The illustrated seal  12  includes a combination of an outer elastomer and an inner elastomer formed into a homogeneous body (e.g., single common/solid body). In certain embodiments, the outer elastomer includes a hard material, and the internal elastomer includes a relatively soft material, or vice-versa. The hard outer elastomer possesses properties that are conducive to sealing in high-pressure and high-temperature environments, and the inner elastomer possesses properties that are conducive to sealing in high-pressure and low-temperature environments. Accordingly, in certain embodiments, the outer elastomer is used for sealing, protecting, and isolating the inner elastomer from high-pressure media in high-temperature environments, and the inner elastomer is used for sealing at high temperatures and/or when the environmental temperatures are below effective sealing temperatures of the outer elastomer. In other words, the seal  12  includes a first material or property that is effective to seal mutually exclusively without the second material or property in certain conditions, while the second material or property is effective to seal mutually exclusively without the first material or property in other conditions. Thus, the embodiments of the seal  12  described in detail below are particularly well suited for use in a wide range of temperatures (e.g., high and low temperatures) and chemical environments. 
       FIG. 2  illustrates a cross-sectional view of an exemplary embodiment of the seal  12 . The illustrated embodiment includes the annular seal  12  having a body  50 , a first elastomer portion  52 , a second elastomer portion  54 , an inner face  56 , an outer face  58 , a top face  60 , a bottom face  62 , and a longitudinal axis  64 . As will be appreciated, the body  50  of the annular (e.g., radial) seal  12  includes a ring-like member centered about the longitudinal axis  64 . The inner face  56  includes the innermost diameter of the body  50  that generally interfaces with (e.g., contacts) the inner body  14 . The outer face  58  includes the face of the seal  12  on the outermost diameter of the body  50  that generally interfaces with (e.g., contacts) the outer body  16 . Accordingly, the inner face  56  and the outer face  58  provide a fluid seal between the annular seal  12  and the inner body  14  and the outer body  16 , respectively. 
     In an annular seal configuration, the seal  12  is generally set by a radial load that compresses or expands the seal into contact with complementary sealing surfaces (e.g., inner and outer bodies  14  and  16 ). For example, the inner body  14  may include a section with a smaller diameter, a section with a larger diameter, and a tapered section between the two sections. Thus, urging the seal  12  onto the inner body  14  and over the tapered section from the small diameter section to the large diameter section provides an axial loading that biases the seal  12  outward and compresses the seal  12  against the outer body  16 . Similarly, a taper on the outer body  16  may provide a compressive load on a seal  12  to generate an inward radial loading that compresses the seal  12  against the inner body  14 . In general, the top face  60  and the bottom face  62  generally do not seal with a complementary surface. However, in a packer arrangement, the top face  60  and the bottom face  62  may generally be used as locations to apply loads to seat, set, and/or lock the seal  12  in place. In other words, the top and bottom faces  60  and  62  may experience axial loads to push the seal  12  into position, to compress the seal  12  such that it expands radially between the inner body  14  and the outer body  16 , and to hold the seal  12  in place. For example, a tool may be forced against the top face  60  until the bottom face  62  contacts a surface and/or another tool, and to load the top face  60  in a direction parallel to the longitudinal axis  64  to compress the seal  12 , causing the seal  12  to expand radially. The radial expansion may cause the outer and inner faces  56  and  58  to bias against the outer body  16  and the inner body  14 , creating a fluid seal between the respective interfaces. Continuing to apply the axial force (e.g., locking the seal  12 ) may maintain the radial expansion and, thus, maintain the fluid seal. 
     The portion of the seal  12  (e.g., the seal interface) that engages the complementary surfaces (e.g., the inner body  14  and the outer body  16 ) may be may include a variety of shapes and configurations. For example, the seal interface may include a continuous surface that is formed from one or more materials. In an embodiment wherein the complementary sealing surface generally conforms to the contour of the seal  12  (e.g., a relatively flat surface), the sealing interface may include a single engagement portion that extends across a surface of the seal  12 . In an embodiment where the complementary surface includes a surface that does not conform to a surface of the seal  12  (e.g., an interrupted surface), the seal interface may include one or more engagement portions at each location where the seal  12  contacts the complementary surface. Further, the seal  12  may include a plurality of interruptions along its sealing surface. For example, the seal  12  may include one ore more bumps, protrusions, indentations, recesses, or similar features. Accordingly, where the complementary surface does not conform to the contour of the seal  12 , the seal interface may include one or more engagement portions at each of the location where the seal  12  contacts the complementary surface. Further, each of the seal engagement portions may include the same or even different types of materials depending on the composition and arrangement of the materials used to form the seal  12 . 
     In the illustrated embodiment, the seal  12  includes the body  50  having the first elastomer portion  52  flanking the second elastomer portion  54 . The body  50  includes the first elastomer portion  52  having a generally rectangular shape (e.g., cross-sectional profile) and the nested second elastomer portion  54 . In one embodiment, nested refers to a set of items or parts forming a hierarchical structure with larger parts (e.g., the first elastomer portion  52 ) enclosing smaller ones (e.g., the second elastomer portion  54 ). The second elastomer portion  54  includes an outer second elastomer  66  adjacent (e.g., sharing a boundary with) the outer face  58  and an inner second elastomer  68  adjacent the inner face  56 . Accordingly, each of the outer soft elastomer  66  and the inner soft elastomer  68  include a band of material that is disposed in the outer and inner diameter of the first elastomer portion  52 . In other words, the first elastomer portion  52  includes an “I” shaped cross-section with the second elastomer portion  54  embedded into the outer face  58  and the inner face  56  of the body  50 . 
     As will be appreciated, the shape of the first elastomer portion  52  and the second elastomer portion  54  may be varied to accommodate specific applications. For example, the first elastomer portion  52 , in one embodiment, includes a shape (e.g., cross-sectional profile) that includes chamfers or other features conducive to seating, setting and locking the seal  12 . Another embodiment includes only one of the second elastomer portions  54 . For example, an embodiment includes only the outer soft elastomer  66 , and another embodiment includes only the second soft elastomer  68 . Further, the shape and location of each of the first and second sealing portions  52  and  54  may be varied. For instance, the second elastomer portions  54  may not be disposed symmetrically about the body  50 . In one embodiment, the outer soft elastomer  66  is offset from the inner soft elastomer  68  in a direction generally parallel to the longitudinal axis  64 . Further, the size and shape of each of the outer soft elastomer  66  and the inner soft elastomer  68  may be varied. For example, in one embodiment, the height and/or width of the outer portion  66  is less than or greater than the height and/or width of the inner portion  68 . Similarly, an embodiment may include varying the shapes of the soft elastomer portions  54 . For example, in one embodiment, the outer soft elastomer  66  includes a generally rectangular shape (e.g., a profile similar to those depicted) and the inner soft elastomer  68  has a semi-circular shape, or vice-versa. Further, embodiments include the first elastomer portion  52  and/or the second elastomer portion  54  including indentations and protrusions (e.g., bumps) that extend radially from the faces  56  and  58  the seal  12 . Embodiments including the varied cross-sectional geometry of the seal  12  are discussed in further detail below with regard to  FIGS. 4-23 . 
     The first elastomer portion  52  and the second elastomer portion  54  include different materials that work cooperatively to provide the desired fluid seal in a range of environments. In one embodiment, the seal  12  includes a first elastomer portion  52  formed from a hard elastomer that is resistant to corrosive attacks and conducive to use in high-temperature environments, and includes a second elastomer portion  54  conducive to sealing in low-temperature environments. Thus, the seal  12  may effectively seal over a broader range of temperatures and pressures as compared to a single elastomer seal. For example, at high temperatures, the hard first elastomer portion  52  is conducive to sealing between the inner and outer faces  56  and  58  of the seal  12 , and the inner and outer bodies  14  and  16 , respectively. Accordingly, in embodiments including the first elastomer portion  52  flanking (e.g., surrounding) the second elastomer portion  54 , as discussed with regard to  FIG. 2 , the first elastomer portion  52  effectively prevents corrosive fluids and/or high temperature and pressure fluids from engaging the second elastomer portion  54 . At low temperatures (e.g., those below the effective sealing temperature of the first elastomer portion  52 ), the softer second elastomer portion  54  maintains the desired fluid seal between the inner and outer faces  56  and  58  of the seal  12 , and the inner and outer bodies  14  and  16 , respectively. For example, at low temperatures, the harder first elastomer portion  52  may not provide an effective fluid seal and, thus, expose the softer second elastomer portion  54  to the environment, including the sealing temperatures, pressure and corrosive chemicals proximate to the seal  12 . However, at reduced temperatures, the softer elastomer maintains its leathery/rubbery state and conforms to the sealing surfaces (e.g., inner body  14  and outer body  16 ). Further, it will be appreciated that at lower temperatures, the threat of corrosive (e.g., chemical) attack on elastomers is reduced, thus, making the soft elastomer suitable for sealing the corrosive low temperature environment. Accordingly, at low temperatures, the soft second elastomer portion  54  can provide the desired fluid seal, and the hard first elastomer portion  52  can provide the fluid seal at higher temperatures. 
     The combination of the harder first elastomer portion  52  and the softer second elastomer portion  54  may enable the seal  12  to maintain a fluid seal during rapid pressure fluctuations. For example, the seal  12  may be resistant to failures associated with explosive decompression. Explosive decompression (ED) refers to a sudden marked drop in the pressure of a system, associated with explosive violence. The pressure drop may occur over several minutes, and in an extreme case may occur in less than 0.1 seconds. Generally ED results from some sort of material fatigue or engineering failure, causing a contained system to suddenly vent into the external atmosphere. Seals  12  in high-pressure vessels (e.g., mineral extraction systems  10 ) are susceptible to explosive decompression. For example, a porous elastomer of the seals  12  can become saturated with high-pressure gases, and if the pressure inside the vessel is suddenly released, then the gases within the elastomeric seal  12  may expand violently, causing blistering or explosion of the material. Embodiments of the seal  12 , including the first elastomer portion  52  flanking the second elastomer portion  54 , help to prevent or reduce the effects of explosive decompression. In one embodiment, the first elastomer portion  52  effectively seals off the second elastomer portion  54  from the surrounding high pressure. In other words, the first elastomer portion  52  does not fail due to ED and, thus, protects the softer (e.g., porous) second elastomer portion  54  from the rapid drop in pressure associated with ED. The resistance from explosive decompression failure may be attributed to the lower permeability, and increased fracture resistance of the hard elastomer with respect to service media. For example, the lower permeability of the hard elastomer prevents the elastomer from becoming saturated with a significant amount of high-pressure gas. Accordingly, during ED, the first elastomer portion  52  may isolate the second elastomer portion  54  from the rapid change in pressure. Further, even if the first elastomer portion  52  fails due to ED, the second elastomer portion  54  may not have become saturated with a high-pressure gas due to the first elastomer portion  52  isolating the second elastomer portion  54  from high pressure over the period preceding ED. Thus, decompression of the surrounding environment may not be fatal to the seal  12  because there is not a significant amount gas internal to the second elastomer portion  54 . In addition, the presence of the first elastomer portion  52  may slow the sequence of decompression, preventing failure of the seal  12  due to ED. In other words, if there is a failure in the first elastomer portion  52 , the rate of the pressure drop experienced by the second elastomer portion  54  may be reduced due to the additional buffer provided by the first elastomer portion  52 . For example, the strength, stiffness and resilience of the outer elastomer portion  52  may prevent a rapid pressure drop in the second elastomer portion  54 . 
     The first and second elastomer portions  52  and  54  may be characterized as hard and/or soft by a variety of metrics. In one embodiment, the hardness of the elastomers may be characterized by the resistance to indentation, otherwise referred to as the materials Durometer (D) denoted in the Shore A scale. In another embodiment, the elastomers may be characterized as hard or soft based on their stiffness (e.g., glass transitions temperature). However, despite the metric, the first and second elastomer portions  52  and  54  may simply have different characteristics, properties, or responses to various conditions (e.g., temperatures, pressure, corrosive materials, etc.) in a mineral extraction system. 
     In a characterization including the Durometer, materials are generally characterized based on ranges. Hard elastomers generally include those having a Durometer greater than about 80 Shore A, soft elastomers generally include those having a Durometer of about 60 Shore A to about 80 Shore A, and super-soft elastomers generally include those having a Durometer below about 60 Shore A. It will be appreciated that super-soft elastomers are rarely used in oil-field and other mineral extraction systems  10 ; however, the inclusion of a protective first elastomer portion  52  may enable these super-soft elastomers to be included in the seal  12 . 
     In one embodiment of the seal  12 , the first elastomer portion  52  includes a hard elastomer having a Durometer of about 90 Shore A, and the second elastomer portion  54  includes a soft elastomer portion  54  having a Durometer of about 70 Shore A. For example, in one embodiment, the first elastomer portion  52  includes a hydrogenated nitrile butadiene rubber (HNBR) having a Durometer of about 90 Shore A, and the second elastomer portion  54  includes a nitrile rubber (NBR) having a Durometer of about 70 Shore A. Other embodiments may include various combinations of hard, soft and super-soft materials. For example, one embodiment includes two hard elastomers, wherein the second elastomer portion  54  has a Durometer below the Durometer of the first elastomer portion  52 . Another embodiment includes a hard or soft first elastomer portion  52  and a super-soft second elastomer portion  54 . As is discussed below with regard to  FIGS. 4-23 , the seal  12  may includes various combinations of hard, soft and super-soft elastomers. Further, an embodiment may include the first elastomer portion  52  and/or the second elastomer portion  54  formed from a CAMLAST™ or a DUROCAM™ material manufactured by Cameron with headquarters in Houston, Tex. 
     In a seal  12  including materials characterized by stiffness, the first elastomer portion  52  may include an elastomer having a high stiffness in a particular (e.g., operating) temperature range and the second elastomer portion  54  may include an elastomer having a relatively low stiffness in the similar temperature range. Turing now to  FIG. 3 , a plot  80  illustrates stiffness (e.g., elastic modulus stiffness (E)) versus temperature for two elastomers. The first curve  82  is indicative of the stiffness versus temperature plot for a relatively hard first elastomer, and the second curve  84  is indicative of the stiffness versus temperature plot for a relatively soft second elastomer. The first curve  82  indicates the first elastomer having a first glass transition temperature (TG 1 )  86 , and the second curve  84  is indicative of the second elastomer having a second glass transition temperature (TG 2 )  88  that is below the first glass transition temperature (TG 1 )  86 . The glass transition temperature is the temperature below which the physical properties of amorphous materials vary in a manner similar to those of a crystalline phase (glassy state), and above which amorphous materials behave like liquids (rubbery/leathery state). Accordingly, the first elastomer includes a glassy region  90  below the first glass transition temperature (TG 1 )  86  and the second elastomer includes a glassy region  92  below the second glass transition temperature (TG 2 )  88 . Further, the plot  80  includes a region  96  that is above the glass transition temperature (e.g., TG 1 ) of both elastomers. Thus, in the temperature region  92  both elastomers may include a glassy state. When the elastomers are in a temperature region  94 , the first elastomer may include glassy state, and the second elastomer may include an amorphous (e.g., rubbery/leathery) state. Finally, in the temperature region  96 , both elastomers may include an amorphous state. 
     The inclusion of at least a first elastomer (e.g.,  82 ) and a second elastomer (e.g.,  84 ) enables the seal  12  to operate effectively over a wider range of temperatures, pressures, and other environmental conditions. For example, in a seal  12  including only the first elastomer, the seal  12  may be ineffective at about or below the first glass transition temperature TG 1  ( 86 ). In other words, at or below the first glass transition temperature (TG 1  ( 86 )), the first elastomer may transition to a glassy state, and seal  12  is unable to conform to the sealing surfaces (e.g., the hanger  24  and the wellhead bore  26 ). For instance, the first elastomer may shrink, retract, and/or embrittle due to the low temperatures, until it is unable to seal against a complementary surface. However, the inclusion of the second elastomer (e.g.,  84 ) may provide for sealing at or below the first glass transition temperature (TG 1  ( 86 )). For example, at a temperature in the region  94  (e.g., between TG 1  ( 86 ) and TG 2  ( 88 )) the first elastomer may transition into glassy state enabling fluids to pass, and the second elastomer remains in an amorphous state conducive to sealing. In other words, the inclusion of the second elastomer widens the operating temperature range of the seal  12  to include temperatures in the region  94 . For example, in one embodiment, the difference between the first glass transition temperature (TG 1 )  86  and the second glass transition temperature (TG 2 )  88  is approximately 10 degrees Fahrenheit (° F.). Accordingly, the seal  12  may be rated for use in environmental conditions that are ten degrees Fahrenheit below that of a seal incorporating only the first elastomer. For example, in one embodiment the glass transition temperature of the first elastomer may be approximately 0° F. and the glass transition temperature of the second elastomer may be approximately −40° F., thus expanding the effective operating range of the seal  12  by approximately 40° F. 
     As will be appreciated, the potential for chemical attack on an elastomer increases as the temperature increases. Further, softer materials are generally more susceptible to chemical attack and may degrade or loose physical properties at lower temperature than relatively hard elastomers. Thus, similar to the second elastomer extending the lower operating range of the seal  12 , the first elastomer extends the upper operating range of the seal  12 . In other words, where the second elastomer is heated to a temperature that causes it to fail due to a chemical attack, or the elastomer transitions from a leathery/rubbery amorphous state to a degraded state, the first elastomer continues to provide an effective fluid seal. Accordingly, as discussed above, the seal  12  in certain embodiments enables the first elastomer to protect the second elastomer at elevated operating temperatures. For example, in an embodiment where the first elastomer flanks the second elastomer, the first elastomer isolates the second elastomer from the chemical attack and/or the elevated temperatures and pressures proximate to the seal  12 . 
     An exemplary embodiment of the seal  12  includes a first elastomer portion  52  including high-temperature, 90 Shore A Durometer FKM (e.g., a type of fluorinated elastomer) and the second elastomer including low-temperature, 90 Shore A Durometer FKM. The first elastomer portion  52  formed from high-temperature, 90 Shore A Durometer FKM includes an operating range of approximately 35° F. to 350° F., and the second elastomer portion  54  formed from low-temperature, 90 Shore A Durometer FKM includes an operating range of approximately −50° F. to 250° F. Accordingly, the seal  12  includes an operating temperature range of approximately −50° F. to 350° F. Further, the seal  12  may effectively seal pressures up to and exceeding approximately 20,000 pounds per square inch (PSI). Other embodiments include various elastomers and combinations of elastomers to effectively increase or decrease the operating range of the seal  12 . 
     Forming the seal  12  may include a variety of process to effectively interface the elastomer portions  52  and  54 . In one embodiment, each of the elastomer portions  52  and  54  are extrusion molded separately and, subsequently compression molded together to provide the body  50 . Accordingly, the body  50  includes a homogeneous structure that includes an interface between the elastomer portions that does not include auxiliary shear stresses (e.g., friction) between the portions. In other words, there is no boundary layer between the two materials. Another embodiment includes vulcanizing the first elastomer portion  52  and the second elastomer portion  54  to one another. For instance, in one embodiment, after each of the elastomer portions  52  and  54  are formed, they are cured in a vulcanization process. Curing the seal  12  in the vulcanization process includes exposing the elastomer portions  52  and  54  to high temperature, high pressure, and catalysts (e.g., sulfur) to cross-link the molecules of the elastomers  52  and  54 . As a result, the seal  12  forms a homogeneous body  50  more resistant to chemical attack. Other embodiments of forming the seal  12  include a variety of processes. For example, one embodiment includes the use an adhesive to adhere the elastomer portions  52  and  54  to one another. Further, certain embodiments include machining the elastomers to the desired shape before or after coupling the elastomers to one another. In addition, the above discussed processes may be employed to couple (e.g., vulcanize) a plurality of elastomers to one another to form the seal  12 . For example, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more different elastomers may be vulcanized to form the seal  12  with an increased operating range. 
     In addition to the embodiments of seal  12  discussed with regard to the cross-section illustrated in  FIG. 2 , other embodiments include alternate configurations and geometries of the elastomer portions  52  and  54  including similar materials and forming techniques. For example, certain embodiments include more than two elastomer portions integral to the seal  12 . Further, embodiments include T-seals, S-seals, Metal-End-Cap seals, face seals, and the like. 
     Turning now to  FIG. 4 , an embodiment of the seal  12  including a first elastomer portion  52  and second elastomer portion  54  extending through the body  50 , is illustrated. The second elastomer portion  54  includes a single layer disposed directly between and separating a first elastomer top layer  100  and a first elastomer bottom layer  102 . The second elastomer portion  54  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . In other words, the second elastomer portion  54  includes a layer of elastomer that is sandwiched between the first elastomer portions  52 . “Sandwiched” refers to the disposition of the first elastomer portion  52  about at least two sides of the second elastomer portion  52 . In one embodiment, the first elastomer portions  52  include a hard elastomer, and the second elastomer portion  54  includes a soft elastomer. In other embodiments, each portion of the seal  12  includes a different material and/or properties, e.g., differing hardness/stiffness/Durometer. For example, in one embodiment, the first elastomer top portion  100  includes a hard elastomer, the second elastomer portion  54  includes a soft elastomer, and the first elastomer bottom portion  102  includes a super-soft elastomer. 
       FIG. 5  illustrates an embodiment of the seal  12  including a plurality of elastomer layers in the body  50  of the seal  12 . In the illustrated embodiment, the seal  12  includes a third elastomer portion  104 , the second elastomer portion  54  and the first elastomer portion  52 . The third elastomer portion  104  includes a single layer, the second elastomer portion  54  includes a second elastomer top layer  106  and a second elastomer bottom layer  108  disposed about the third elastomer portion  104 , and the first elastomer portion  52  includes the first elastomer top layer  100  and the first elastomer bottom layer  102  disposed about the second elastomer portion  54 . Each of the first elastomer portion  52 , the second elastomer portion  54  and the third elastomer portion  104  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . In other words, the seal  12  includes a plurality of elastomer layers sandwiched between outer elastomer layers. 
       FIG. 6  illustrates an embodiment of the seal  12  including a plurality of elastomer portions nested in the body  50  of the seal  12 . In the illustrated embodiment, the seal  12  includes the first elastomer portion  52 , the second elastomer portion  54  and the third elastomer portion  104 . The first elastomer portion  52  includes a rectangular body similar to that discussed with regard to  FIG. 2 . Further, the second elastomer portion  54  includes the inner and outer second elastomer portions  68  and  66  similar to those discussed with regard to  FIG. 2 . The third elastomer portion  104  includes an inner third elastomer  106  and an outer elastomer portion  108 . As illustrated, the inner third elastomer  106  is immediately surrounded by the inner second elastomer portion  68 , and the outer third elastomer portion  108  is immediately surrounded by the outer second elastomer portion  66 . Further, the inner third elastomer  106  includes a face adjacent the inner face  56  of the seal  12 , and the outer third elastomer  108  includes a face adjacent the outer face  58  of the seal  12 . In other words, the body  50  of the seal  12  includes the first elastomer portion  52 , a plurality of bands of the second elastomer portion  54  nested in the inner and outer diameter of the first elastomer portion  52 , and a plurality of bands of the third elastomer portion  104  nested in each of the second elastomer portions  54 . In one embodiment, the seal  12  includes only one of the inner second and third elastomer portions  68  and  106  or the outer second and third elastomer portions  66  and  108 . Further, other embodiments may include any combination of the first, second and third elastomer portions  52 ,  54 ,  104 . 
       FIG. 7  illustrates an embodiment of the seal  12  including a plurality of elastomer portions offset and integral to the body  50  of the seal  12 . In the illustrated embodiment, the seal  12  includes the first elastomer portion  52 , the second elastomer portion  54 , the third elastomer portion  104  and a fourth elastomer portion  110 . Each of the second, third and fourth elastomer portions  54 ,  104 ,  110  are disposed in series along the face of the faces  56  and  58  of the seal  12 . For example, the second elastomer portion  52  includes the inner and outer second elastomer  68  and  66 , the third elastomer portion  104  includes the inner and outer third elastomers  106  and  108 , and the fourth elastomer portion  110  includes an inner fourth elastomer  112  adjacent the inner face  56  of the seal  12 , and an outer fourth elastomer  114  adjacent the outer face  58  of the seal  12 . Accordingly, each of the second, third and fourth elastomers include separate rings disposed proximate to one another in the inner and outer diameters of the seal  12 . In one embodiment, the second and fourth elastomer portions  54  and  110  include the same type of elastomer. For example, in one embodiment, the first elastomer portion  52  includes a hard elastomer, the second and fourth elastomer portions  54  and  110  include a soft elastomer, and the third elastomer portion  104  includes a super-soft elastomer. 
     As mentioned previously, embodiments of the seal  12  include employing similar techniques in various types of seals  12 .  FIG. 8  illustrates an S-seal in accordance with embodiments of the present technique. The seal  12  includes the body  50  having a protrusion  120  in the outer diameter (OD), and integral anti-extrusion springs  122 . Similar to the embodiments described with regard to  FIG. 2 , the seal  12  includes the first elastomer portion  52  flanking the second elastomer portion  54 . For example, the body  50  includes the first elastomer portion  52  having a generally rectangular shape (e.g., cross-sectional profile), including the protrusion  120  extending from the outer diameter of the seal  12 , and the nested second elastomer portion  54 . The second elastomer portion  54  includes the outer second elastomer  66  adjacent (e.g., sharing a boundary with) the outer face  58  and the inner second elastomer  68  adjacent the inner face  56 . For example, each of the outer second elastomer  66  and the inner second elastomer  68  includes a band of material that is disposed in the outer and inner diameters of the first elastomer portion  52 . As will be appreciated, similar to the discussion regarding  FIG. 2 , the cross-section of the first elastomer portion  52  and the second elastomer portion  54  may be varied to accommodate specific applications. For example,  FIG. 9  illustrates the seal  12  including an S-seal having the protrusion  120  and the anti-extrusion springs  122  disposed on the internal diameter of the seal  12 . 
     Further, embodiments including an S-seal  12  may incorporate any of the features discussed with regard to  FIGS. 4-7 . For example, similar to the embodiment illustrated and discussed with regard to  FIG. 4 ,  FIG. 10  illustrates an S-seal including a layer of the second elastomer  54  extending between the inner face  56  and the outer face  58 . In the illustrated embodiment, the second elastomer portion  54  includes a single layer disposed directly between and separating the first elastomer top layer  100  and the first elastomer bottom layer  102 , wherein the second elastomer portion  54  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . Further, the embodiment includes the protrusion  120  in the outer diameter (OD), and integral anti-extrusion springs  122 . Other embodiments include a cross-section of the seal  12  including multiple elastomer layers (see  FIG. 5 ), multiple elastomer layers (see  FIG. 6 ), multiple elastomers offset and integral to the body  50  (see  FIG. 7 ), and the like. 
       FIG. 11  illustrates a T-seal in accordance with embodiments of the present technique. The seal  12  includes a protrusion  130  in the outer diameter (OD), and extrusion rings  132  disposed integral to the protrusion  130 . The extrusion rings  132  may include PEEK (polyetheretherketone), metal, or other hard plastic materials, for instance. Similar to the embodiments described with regard to  FIGS. 2 and 8 , the seal  12  includes the first elastomer portion  52  flanking the second elastomer portion  54 . For example, the body  50  includes the first elastomer portion  52  having a generally rectangular shape (e.g., cross-sectional profile) including the protrusion  130  extending from the outer diameter of the seal  12  and the integral second elastomer portion  54 . The second elastomer portion  54  includes the outer second elastomer  66  adjacent (e.g., sharing a boundary with) the outer face  58  and the inner second elastomer  68  adjacent the inner face  56 . For example, each of the outer second elastomer  66  and the inner second elastomer  68  includes a band of material that is disposed in the outer and inner diameters of the first elastomer portion  52 . As will be appreciated, similar to the discussion regarding  FIGS. 2 and 8 , the cross-section of the first elastomer portion  52  and the second elastomer portion  54  can be varied to accommodate specific applications. For example,  FIG. 12  illustrates the seal  12  including a T-seal having the protrusion  130  and the extrusion rings  122  disposed on the internal diameter of the seal  12 . 
     Further, embodiments of the T-seal  12  may incorporate any of the features discussed with regard to  FIGS. 4-7 . For example, similar to the embodiment illustrated and discussed with regard to  FIGS. 4 and 10 ,  FIG. 13  illustrates a T-seal including a layer of the second elastomer  54  extending between the inner face  56  and the outer face  58 . In the illustrated embodiment, the second elastomer portion  54  includes a single layer disposed directly between and separating the first elastomer top layer  100  and the first elastomer bottom layer  102 , wherein the second elastomer portion  54  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . Further, the embodiment includes the protrusion  130  in the outer diameter (OD), and extrusion rings  132 . Other embodiments may include a cross-section of the seal  12  including multiple elastomer layers (see  FIG. 5 ), multiple elastomer layers (see  FIG. 6 ), multiple elastomers offset and integral to the body  50  (see  FIG. 7 ), and the like. 
       FIG. 14  illustrates a Metal-End-Cap seal in accordance with embodiments of the present technique. The seal  12  includes metal caps  140  disposed on the top and bottom faces  60  and  62  of the seal  12 . Further, the seal  12  includes a cross-section having chamfers  142  defining a first protrusion  144  including the outer face  58 . The internal diameter includes a second protrusion  146  that defines the inner face  56 . Similar to the embodiments described with regard to  FIGS. 2, 8 and 11 , the seal  12  includes the first elastomer portion  52  flanking the second elastomer portion  54 . For example, the body  50  includes the first elastomer portion  52  having a generally rectangular shape (e.g., cross-sectional profile) including the protrusions  144  and  146  and the nested second elastomer portion  54 . The second elastomer portion  54  includes the outer second elastomer  66  integral to the first protrusion  144  and adjacent (e.g., sharing a boundary with) the outer face  58 , and the inner second elastomer  68  integral to the second protrusion  146  and adjacent the inner face  56 . For example, each of the outer second elastomer  66  and the inner second elastomer  68  includes a band of material that is disposed in the outer and inner diameters of the first elastomer portion  52 . As will be appreciated, similar to the discussion regarding  FIGS. 2, 8 and 11 , the cross-section of the first elastomer portion  52  and the second elastomer portion  54  may be varied to accommodate specific applications. 
       FIG. 15  illustrates the Metal-End-Cap seal  12  having the first protrusion  144  and the chamfers  142  disposed on the internal diameter of the seal  12 . Further, the shape and location of each of the first and second sealing portions  52  and  54  may be varied. For instance, the second elastomer portions  54  may not be disposed symmetrically about the body  50 . In one embodiment, the outer second elastomer  66  is offset from the inner second elastomer  68  in a direction generally parallel to the longitudinal axis  64 . Further, the size and shape of each of the outer second elastomer  66  and the inner second elastomer  68  may be varied. For example,  FIG. 16  illustrates an embodiment of the Metal-End-Cap seal  12 , wherein the height  148  and width  150  of the inner second elastomer  68  is greater than the height  152  and width  154  of the outer second elastomer  66 . 
     Further, the Metal-End-Cap seal  12  may incorporate any of the embodiments of the seal  12  discussed with regard to  FIGS. 4-7 . For example, similar to the embodiments illustrated and discussed with regard to  FIGS. 4, 10 and 13 ,  FIG. 17  illustrates the Metal-End-Cap seal  12  including a layer of the second elastomer  54  extending between the inner face  56  and the outer face  58 . In the illustrated embodiment, the second elastomer portion  54  includes a single layer disposed directly between and separating the first elastomer top layer  100  and the first elastomer bottom layer  102 , wherein the second elastomer portion  54  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . 
     Other embodiments include a cross-section of the seal  12  including multiple elastomer layers. For example, similar to the embodiment of the seal illustrated in  FIG. 5 ,  FIG. 18  illustrates an embodiment of the Metal-End-Cap seal  12  including a plurality of elastomer layers in the body  50  of the seal  12 . In the illustrated embodiment, the seal  12  includes the third elastomer portion  104 , the second elastomer portion  54  and the first elastomer portion  52 . The third elastomer portion  104  includes a single layer, the second elastomer portion  54  includes the second elastomer top layer  106  and the second elastomer bottom layer  108  disposed about the third elastomer portion  104 , and the first elastomer portion  52  includes the first elastomer top layer  100  and the first elastomer bottom layer  102  disposed about the second elastomer portion  54 . Each of the first elastomer portion  52 , the second elastomer portion  54  and the third elastomer portion  104  extends adjacent to the inner surface  56  and the outer surface  58  of the seal  12 . In other words, the seal  12  includes a plurality of elastomer layers sandwiched between outer elastomer layers. 
       FIG. 19  illustrates an embodiment of the Metal-End-Cap seal  12  including multiple nested elastomer layers similar to the embodiment of the cross-section illustrated in  FIG. 6 . In the illustrated embodiment, the seal  12  includes the first elastomer portion  52 , the second elastomer portion  54  and the third elastomer portion  104 . The first elastomer portion  52  includes the rectangular body  50 , and the second elastomer portion  54  includes the inner and outer second elastomer portions  66  and  68 . The third elastomer portion  104  includes the inner third elastomer  106  and the outer elastomer portion  108 . As illustrated, the inner third elastomer  106  is immediately surrounded by the inner second elastomer portion  68 , and the outer third elastomer portion  108  is immediately surrounded by the outer second elastomer portion  66 . Further, the inner third elastomer  106  includes a face adjacent the inner face  56  of the seal  12 , and the outer third elastomer portion  108  includes a face adjacent the outer face  58  of the seal  12 . Another embodiment of the Metal-End-Cap seal  12  may includes multiple elastomers offset and integral to the body  50  (see  FIG. 7 ), and the like. 
     In addition, to the previously discussed features, the seal  12  may incorporate additional features to improve the seal. For example, embodiments of the seal  12  include a cross-section including a plurality of indentations. Indentations in the cross-section translate into grooves that extend about the internal and external diameter of the seal (e.g., faces  56  and  58 ). The grooves effectively create ridges that provide areas of increased contact stress to maintain a fluid seal between the seal  12  and the internal and external bodies  14  and  16 . For instance,  FIG. 20  illustrates an embodiment of the seal  12  including a plurality of indentations  160 . The indentations include inner diameter indentations  162  and outer diameter indentation  164 . Further, the indentations  160  are disposed in a plurality of the elastomers. For instance, the indentations  160  may include annular grooves in the first elastomer portion  52  and the second elastomer portion  54 . In the illustrated embodiment of  FIG. 20 , the inner and outer indentations  162  and  162  are generally symmetrical about an axis  160  running down the center of the cross-section of the seal  12 . In other words, the geometries of the indentations  160  are identical on the inner face  56  and the outer face  58 . 
     Other embodiments of the seal  12  include asymmetrical profiles on the internal diameter and the external diameter of the seal  12 .  FIG. 21  illustrates an embodiment including a Metal-End-Cap seal  12  having an asymmetrical profile on the inner face  56  and the outer face  58 . For example, the illustrated embodiment includes two indentations  162  on the inner face  56  of the seal  12 , and a single indentation  164  on the outer face  58  of the seal  12 . In other words, the seal  12  cross-section includes a first geometry on the internal diameter and a second geometry on the external diameter that is different from the first geometry. Similar features may be incorporated into a variety of seals. For example, embodiments include the asymmetric or symmetric profile employed in a T-seal, an S-seal, and the like. 
     Although the above discussion focuses primarily on annular (e.g., radial) seals  12 , similar techniques may be employed in the design and use of face seals. Face seals generally include seals  12  that provide a fluid seal between two generally flat surfaces. For example,  FIG. 22  illustrates an embodiment of a face seal  12  in accordance with techniques of the present technique. The seal  12  includes the body  50 , the first elastomer portion  52 , the second elastomer portion  54 , the inner face  56 , the outer face  58 , the top face  60  and the bottom face  62 . In operation, the top face  60  is mated to a first body and the bottom face  62  is mated to a second body to provide a fluid seal between the first and second bodies. Accordingly, embodiments include the addition of sealing features conducive to sealing via the top and bottom faces  60  and  62 . For example, as illustrated in  FIG. 22 , the second elastomer portion  54  includes a top second elastomer  170  adjacent the top face  60  and a bottom second elastomer  172  adjacent bottom face  62 . Thus, the first elastomer portion  52  flanks the second elastomer portion  54  in a similar manner to that discussed with regard to  FIG. 2 . 
     In another embodiment, the second elastomer portion includes a single layer passing through the cross-section of the seal  12 . For example,  FIG. 23  includes an embodiment similar to those illustrated and discussed with regard to  FIGS. 4, 10, 13 and 17 . As illustrated in  FIG. 23 , the seal  12  includes a first elastomer portion  52 , and a second elastomer portion  54 . The second elastomer portion  54  includes a single layer disposed between a first elastomer inner layer  176  and a first elastomer outer layer  178 . The second elastomer portion  54  extends adjacent to the top face  60  and the bottom face  62  of the seal  12 . Other embodiments include the face seal  12  having cross-sections similar to those discussed with regard to  FIGS. 4-21 . 
     Each of the above discussed embodiments of the seal  12  may include any combination of elastomers and cross-sections conducive to providing a fluid seal. For example, each separate portion may include an elastomer having a different hardness, stiffness or glass transition temperature. Further, embodiments may include combinations of the embodied cross-sections. For example, an embodiment includes a cross-section including a profile similar to  FIG. 2  at the inner face  56 , and a cross-section including a profile similar to  FIG. 6  on the outer face  58 . 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.