Patent Publication Number: US-2020300367-A1

Title: Seals

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. § 119(e) to U.S. Patent Application No. 62/821,246 entitled “SEALS,” by Simone CAGLIO et al., filed Mar. 20, 2019, which is assigned to the current assignee hereof and incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to seals, and more particularly to energized seals. 
     RELATED ART 
     Seals are typically used to prevent leakage from occurring within an annulus between two or more components. For example, a seal may be used in hardware between inner and outer components, such as a shaft and a bore. The seal may be positioned between the shaft and the bore to maintain different fluidic pressures or to separate different fluidic components on opposing sides of the seal. 
     In many applications, for instance in oil and gas drilling and refining operations, it is necessary for seals to withstand wide temperature ranges while maintaining effective sealing characteristics. Industries utilizing seals continue to demand improved seal performance over a wide range of environmental conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are illustrated by way of example and are not intended to be limited in the accompanying figures. 
         FIG. 1  includes a partial cross-sectional view of a seal in accordance with an embodiment. 
         FIG. 2  includes a cross-sectional view of the seal in accordance with an embodiment. 
         FIG. 3  includes an enlarged cross-sectional view of a portion of a seal in accordance with an embodiment. 
         FIG. 4  includes a cross-sectional view of a seal in accordance with another embodiment. 
         FIG. 5  includes a chart plotting leakage performance of an exemplary seal in accordance with an embodiment herein as measured over a range of low temperature cycles. 
         FIG. 6  includes a chart plotting leakage performance of the exemplary seal in accordance with an embodiment herein as measured over a range of high temperature cycles. 
     
    
    
     DETAILED DESCRIPTION 
     The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings. However, other embodiments can be used based on the teachings as disclosed in this application. 
     The terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     Also, the use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one, at least one, or the singular as also including the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and may be found in textbooks and other sources within the sealing arts. 
     Seals are generally used in hardware to isolate volumes and pressures from one another. In particular, seals can be used in hardware adapted for use in harsh environmental conditions, such as at low temperatures, and required to meet certain leakage performance metrics. 
     In one or more embodiments, a seal can include an annular body adapted to fit around an inner component and within an outer component. In particular, the seal can fit within an annulus defined between the inner and outer components. In certain instances, the seal can be adapted to have a fugitive emission measured leakage rate, as measured according to ISO 15848-1, less than 0.00001 mg*s −1 *m −1 . In a more particular embodiment, the seal can be certified as Class AH compliant, as measured according to ISO 15848-1. 
     In one or more embodiments, the seal can include a plurality of rings stacked together in axial alignment. The plurality of rings can include, for example, a first energized jacket, a second energized jacket, and a plurality of seal rings. The first and second energized jackets can be stacked adjacent to one another. In an embodiment, the second energized jacket can be disposed between the first energized jacket and the plurality of seal rings. A spacer can be positioned between the first and second energized jackets and extend at least partially into the second energized jacket. 
     In an embodiment, the first and second energized jackets can include different types of energizing elements. For example, the first energized jacket can include a coiled spring having a generally “O” shaped cross-sectional profile and the second energized jacket can include a cantilevered spring having a generally U-shaped cross-sectional profile. 
     In certain instances, the first and second energized jackets can operate differently. For example, the first energized jacket can operate under axial pressure generated within the annulus on a first axial end of the seal. The pressure can cause the first energized jacket to radially bias into the hardware, thus generating a primary effective sealing condition. Meanwhile, the second energized jacket can operate under mechanical loading caused by the first energized jacket (or the spacer disposed between the first and second energized jackets). That is, the first energized jacket (or the spacer disposed between the first and second energized jackets) can mechanically load the second energized jacket to generate a secondary effective sealing condition. 
       FIGS. 1 and 2  include cross-sectional views of a seal  100  in accordance with an embodiment. The seal  100  includes a first energized jacket  102  and a second energized jacket  104 . In an embodiment, the first energized jacket  102  can define a first axial end  106  of the seal  100 . The first axial end  106  of the seal  100  can be adapted for use on a relatively high-pressure region of a hardware (not illustrated). The resulting load from the high-pressure region can bias the first energized jacket  102  toward a relatively low-pressure side of the hardware. 
     The first energized jacket  102  can include a body  108  defining a volume  110  at least partially containing a first energizing element  112 . 
     In an embodiment, the body  108  can include a polymeric material. Exemplary polymers include tetrafluoroethylene (TFE) such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), polychlorotrifluoroethylene (PCTFE), polyethylenetetrafluoroethylene (ETFE), vinylidene fluoride (THV), polyethylenechlorotrifluoroethylene (ECTFE), polyether ether ketone (PEEK), or any combination thereof. The scope of the disclosure is not intended to be limited to those exemplary polymers listed above. In a particular embodiment, the body  108  includes PTFE, such as, for example, FLUOROLOY® A02 (available from Saint-Gobain Performance Plastics). FLUOROLOY® A02 exhibits a tensile strength, as measured according to ASTM D4894, of 36.5 MPa, an elongation, as measured according to ASTM D4894, of 500%, a compressive modulus, as measured according to ASTM D695, of 572 MPa, a deformation under load, as measured according to ASTM D621 and as tested at 2,000 PSI for 24 hours, of 4.6%, a Shore D hardness, as measured according to ASTM D2240, of between 50 and 65, and a coefficient of linear thermal expansion, as measured according to ASTM E831 between 26° C. and 200° C., of 12.6 m/m/° C. 
     One or more fillers can be included in the body  108  of the first energized jacket  102 . For instance, exemplary fillers include glass fibers, carbon fibers, silicon, PEEK, aromatic polyester, carbon particles, bronze, fluoropolymers, thermoplastic fillers, aluminum oxide, polyamidimide (PAI), PPS, polyphenylene sulfone (PPSO2), LCP, aromatic polyesters, molybdenum disulfide, tungsten disulfide, graphite, grapheme, expanded graphite, boron nitride, talc, calcium fluoride, or any combination thereof. Additionally, the filler can include alumina, silica, titanium dioxide, calcium fluoride, boron nitride, mica, Wollastonite, silicon carbide, silicon nitride, zirconia, carbon black, pigments, or any combination thereof. 
     In an embodiment, the first energizing element  112  can be fully contained within the volume  110  of the body  108  such that the first axial end  106  of the seal  100  is defined by one or more portions of the body  108 . In a more particular embodiment, at least a portion of the first energizing element  112  can be visible from the first axial end  106  of the seal  100 . In certain instances, at least 10% of the first energizing element  112  can be disposed in the volume  110 , at least 25% of the first energizing element  112  can be disposed in the volume  110 , at least 50% of the first energizing element  112  can be disposed in the volume  110 , or at least 75% of the first energizing element  112  can be disposed in the volume. In a more particular embodiment, the entire first energizing element  112  can be disposed in the volume  110 . 
     The first energizing element  112  can include a deformable energizer, such as a spring, adapted to bias the body  108  of the first energized jacket  102  into the hardware. In an embodiment, first energizing element  112  can include a double coiled spring, a single coiled spring, an advanced pitch spring, a cantilevered spring, or a plurality of cantilevered springs. In a particular embodiment, the first energizing element  112  can have a generally “O” shaped cross-sectional profile. In an embodiment, the first energizing element  112  can be formed from a metal, alloy, or other resilient material. Exemplary alloys may include cobalt and nickel. In certain instances, the first energizing element  112  can be heat treated to increase mechanical properties. 
     The second energizing jacket  104  can include a body  114  defining a volume  116  at least partially containing a second energizing element  118 . In an embodiment, the body  114  can include a polymeric material. Exemplary polymers include tetrafluoroethylene (TFE) such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), polychlorotrifluoroethylene (PCTFE), polyethylenetetrafluoroethylene (ETFE), vinylidene fluoride (THV), polyethylenechlorotrifluoroethylene (ECTFE), polyether ether ketone (PEEK), or any combination thereof. The scope of the disclosure is not intended to be limited to those exemplary polymers listed above. In a particular embodiment, the body  114  includes PTFE, such as, for example, FLUOROLOY® A02 (available from Saint-Gobain Performance Plastics). 
     One or more fillers can be included in the body  114  of the second energized jacket  104 . For instance, exemplary fillers include glass fibers, carbon fibers, silicon, PEEK, aromatic polyester, carbon particles, bronze, fluoropolymers, thermoplastic fillers, aluminum oxide, polyamidimide (PAI), PPS, polyphenylene sulfone (PPSO2), LCP, aromatic polyesters, molybdenum disulfide, tungsten disulfide, graphite, grapheme, expanded graphite, boron nitride, talc, calcium fluoride, or any combination thereof. Additionally, the filler can include alumina, silica, titanium dioxide, calcium fluoride, boron nitride, mica, Wollastonite, silicon carbide, silicon nitride, zirconia, carbon black, pigments, or any combination thereof. 
     In an embodiment, the second energizing element  118  can be fully contained within the volume  116  of the body  114 . In certain instances, at least 10% of the second energizing element  118  can be disposed in the volume  116 , at least 25% of the second energizing element  118  can be disposed in the volume  116 , at least 50% of the second energizing element  118  can be disposed in the volume  116 , or at least 75% of the second energizing element  118  can be disposed in the volume  116 . In a more particular embodiment, the entire first energizing element  112  can be disposed entirely in the volume  110 . 
     In a particular embodiment, the body  114  can include one or more retention features  120  adapted to prevent extrusion of the second energizing element  118  from the volume  116 . The retention feature  120  can include, for instance, a notch or structure extending into the volume  116  to prevent axial translation of the second energizing element  118  from the volume  116 . The exemplary embodiment illustrated in  FIG. 2  includes the retention feature  120  on an outer surface  122  of the volume  116 . However, in other embodiments, the retention feature  120  can be disposed on an inner surface  124  of the volume  116  or the body  114  can include a plurality of retention features (e.g., one retention feature on the inner surface  124  and one retention feature on the outer surface  122 ). 
     The second energizing element  118  can include a deformable energizing element, such as a spring, adapted to bias the body  114  of the second energized jacket  104  into the hardware. The second energizing element  118  can include a double coiled spring, a single coiled spring, an advanced pitch spring, a cantilevered spring, or a plurality of cantilevered springs. In an embodiment, the first and second energizing elements  112  and  118  can include different types of energizing elements, as compared to one another. For instance, the first energizing element  112  can include a double coiled spring and the second energizing element  118  can include a cantilever spring. The cantilever spring can have a generally “U” shaped cross-sectional profile. In another embodiment, the first and second energizing elements  112  and  118  can include the same type of energizing elements, as compared to one another. The second energizing element  118  can be formed from a metal, alloy, or other resilient material. Exemplary alloys may include cobalt and nickel. 
     The body  114  of the second energized jacket  104  can define a radially inner surface  126  and a radially outer surface  128 . At least one of the radially inner and outer surfaces  126  and  128  can include one or more sealing features  130  adapted to create enhanced fluidic sealing characteristics. In an embodiment, the one or more sealing features  130  can include at least one sealing feature, at least two sealing features, at least three sealing features, at least four sealing features, or at least five sealing features. The sealing features  130  can include ridges, bumps, dimples, scrapers, edges, castellation, another radially projecting surface feature, or any combination thereof. In an embodiment, the sealing features  130  can extend around at least a portion of a circumference of the body  114 . In a particular embodiment, at least one of the sealing features  130  can extend continuously around the entire circumference of the body. That is, the at least one sealing feature  130  can have an uninterrupted and similar shaped profile around the entire circumference of the body  114 . For instance, in the illustrated embodiment ( FIG. 1 ), the sealing features  130  extend around the entire circumference of the body  114  of the second energized jacket  104 . 
     In the illustrated embodiment, the sealing feature  130  includes a first sealing feature  130 A and a second sealing feature  130 B disposed on the radially outer surface  128  of the body  114 . In the uninstalled state illustrated in  FIG. 2  (i.e., prior to installation of the seal  100  within hardware), the first and second sealing features  130 A and  130 B can have different heights as compared to one another and as measured from the radially outer surface  128  of the body. For instance, in the illustrated embodiment, the first sealing feature  130 A is taller than the second sealing feature  130 B. By way of example, the first sealing feature  130 A can be at least 1.01 times taller than the second sealing feature  130 B, at least 1.05 times taller than the second sealing feature  130 B, at least 1.1 times taller than the second sealing feature  130 B, or at least 1.5 times taller than the second sealing feature  130 B. 
     During installation, the body  114  of the second energized jacket  104  may deform to fit within the annulus of the hardware. More particularly, axial extensions  132 A and  132 B of the body  114  may deform toward one another from a hub  134  of the body  114  in a generally cantilevered manner. Such deformation may alter the relative, effective difference in height of the first and second sealing features  130 A and  130 B. That is, the perceived heights (i.e., the distance from central axis A) of the first and second sealing features  130 A and  130 B may be more similar in the installed state as compared to the uninstalled state. In a particular embodiment, the perceived height of the first and second sealing features  130 A and  130 B, as measured in the installed state, may be approximately the same as measured from the central axis A. In an embodiment, sealing load applied between the first sealing feature  130 A and hardware can be approximately equal to sealing load applied between the second sealing feature  130 B and the hardware. In another embodiment, sealing load between the hardware and the first sealing feature  130 A may be different from sealing load between the hardware and the second sealing feature  130 B. For instance, sealing load generated between the first sealing feature  130 A and the hardware may be greater than sealing load generated between the second sealing feature  130 B and the hardware. The plurality of sealing features  130  can provide redundant sealing characteristics. A pocket formed between the sealing features  130 A and  130 B may trap leaked fluids and prevent egress thereof from the relatively low-pressure side of the hardware. In an embodiment, the radially inner and outer surfaces of the body  114  can define a different number of annular ridges  130  as compared to one another. For by way of non-limiting example, the radially inner surface can have one or three annular ridges  130  and the radially outer surface can have two or four annular ridges  130 . It is noted that the body  114  can include a different number of annular ridges  130  arranged on the radially inner and outer surfaces. 
     As illustrated, the first and second energized jackets  102  and  104  can be disposed adjacent, or nearly adjacent to one another. The first energized seal  102  can form a primary sealing interface adapted to handle relatively high-pressure within the hardware. Pressure from the contained liquid can cause the body  108  of the first energized jacket  102  to bias radially into the hardware. The second energized jacket  104  can be mechanically biased by the first energizing jacket  102  or a spacer  136  disposed between the first and second energized jackets  102  and  104 . 
     In an embodiment, the spacer  136  can be disposed between the first and second energized jackets  102  and  104 . The spacer  136  can transmit axial loading from the first energized jacket  102  to the second energized jacket  104 . In an embodiment, the spacer  136  can include a base  138  and a support  140 . The support  140  can extend from the base  138  in a direction toward the second energized jacket  104 . In a more particular embodiment, the support  140  can define a height, H S , as viewed in cross section and measured parallel with a central axis A of the seal  100 , generally perpendicular to a thickness, T B , of the base  138 . 
     In an embodiment, H S  can be no less than 0.5 T B . In a more particular embodiment, H S  can be no less than 0.75 T B , no less than 1 T B , no less than 1.1 T B , or no less than 1.25 T B . In another embodiment, H S  can be no greater than 10 T B , no greater than 5 T B , or no greater than 2 T B . In a particular embodiment, and as described in greater detail below, the support height, H S , can be sized to fit within the volume  116  of the second energized jacket  104 . 
     In an embodiment, the thickness, T B , of the base  138  may lie along a plane oriented perpendicular to the central axis A of the seal  100 . The base  138  thickness, T B , as measured between radially inner and outer locations, can be less than a thickness of the annulus adapted to receive the seal  100 . In such a manner, the spacer  136  can be adapted to be spaced apart from the hardware in the installed state. 
     In an embodiment, the spacer  136  may include a single, monolithic body. The spacer  136  can be formed from a resilient material, such as a resilient polymer. In an embodiment, the spacer  136  can include a material having a higher strength as compared to the material of the first and second energized jackets  102  and  104 . By way of non-limiting example, the spacer  136  can include an aramid, such as an aromatic polyamide, an aromatic polyester, an aromatic polyether, or an aromatic polyurethane, as these materials exhibit a low coefficient of linear thermal expansion and a low elongation at break. Other exemplary polymers include: polyimides (such as, for example, the KAPTON brand polyimide available from E.I duPont deNemours and Co., Wilmington, Del.), polyparaphenylene (PPP, available from Maxdem, Inc., San Dimas, Calif.), poly (ethylene naphthalene 2,6-dicarboxylate, PEN), poly(ethylene naphthalate-co-2,6-bibenzoate, PENBB), polyethylene terephthalate (PET), polycarbonate (PC), cycloolefin copolymers (COC, such as, for example, TOPAS® available from Hoechst Technical Polymers), polyphenylene sulfide (PPS), PES (polyether sulfone), polyaryletherketone (PAEK), polysulfones, polyacrylates (e.g., crosslinked polymethyl methacrylate, PMMA) and the like and mixtures thereof. In a particular embodiment, the spacer  136  can include Meldin. It will be recognized that this list is not exhaustive and that other materials can also be used in the composition of the spacer  136 . 
     In a non-illustrated embodiment, the spacer  136  can be integral with the first energized jacket  102 . That is, the spacer  136  can be integral, or monolithic, with the body  108  of the first energized jacket  102 . In certain instances, the spacer  136  may be defined as the portion of the body  108  that acts primarily to space apart the first and second energized jackets  102  and  104 . 
     Referring to  FIG. 2 , the spacer  136  can define a first axial end surface  142  adapted to contact the body  108  of the first energized jacket  102 . In a more particular embodiment, the first axial end surface  142  of the spacer  136  can be adapted to contact a surface of a hub  144  of the first energized jacket  102 . In the illustrated embodiment, the first axial end surface  142  of the spacer  136  contacts the hub  144  of the first energized jacket  102  along a planar contact interface  146 . In an embodiment, the interface  146  can lie along a plane generally perpendicular with the central axis A of the seal  100 . As illustrated, the interface  146  can extend across an entire thickness of the spacer  136 . Use of a planar interface  146  between the first energized jacket  102  and the spacer  136  may enhance sealing characteristics of the seal  100  as compared to non-planar interfaces, such as arched interfaces, multi-planar interfaces, or both. In certain embodiments, the interface  146  can be approximately uniform in shape, size, or both, as measured around the circumference of the seal  100 . In a non-illustrated embodiment, the interface  146  between the first energized jacket  102  and the spacer  136  can be non-planar. 
       FIG. 3  includes an enlarged view of the spacer  136  and second energized jacket  104  of a seal  100  in accordance with an embodiment. As illustrated, the support  140  of the spacer  136  can define a tapered profile extending into the volume  116  of the second energized jacket  104 . In an embodiment, the support  140  can contact the second energizing element  118  in the installed state. In a more particular embodiment, a tip  152  of the support  140  can contact the second energizing element  118  in the installed and uninstalled states. In a more particular embodiment, side surfaces  154  of the support  140  can be spaced apart from the second energizing element  118  at least when the seal  100  is in the uninstalled state (i.e., prior to deflection caused by installation force from the hardware). 
     In a particular embodiment, the support  140  can define a first thickness, T S1 , as measured at a first axial location  148  along the support  140 , and a second thickness, T S2 , as measured at a second axial location  150  along the support  140 , where T S1  is not equal to T S2 . For instance, T S1  can be less than T S2 . By way of example, T S1  can be no greater than 0.99 T S2 , no greater than 0.98 T S2 , no greater than 0.97 T S2 , no greater than 0.96 T S2 , no greater than 0.95 T S2 , no greater than 0.9 T S2 , no greater than 0.75 T S2 , or no greater than 0.5 T S2 . In another embodiment, T S1  can be no less than 0.01 T S2 , no less than 0.1 T S2 , or no less than 0.25 T S2 . In an embodiment, the first axial location  148  can be disposed closer to the first axial end  106  of the seal  100  than the second axial location  150 . 
     In an embodiment, the support  140  can have a generally linear taper. That is, at least a portion of at least one side surface  154  of the support  140 , as viewed in cross section, can lie along a straight line L. In another embodiment, the support  140  can define an arcuate cross-sectional profile, a multi-faced polygonal cross-sectional profile, or both. In certain instances, the tip  152  of the support  140  can define a radius of curvature less than a radius of curvature of the second energizing element  118 . In an embodiment, the support  140  can extend from the base  138  at a curved or fileted interface to reduce cracking and interfacing issues therebetween. 
     In an embodiment, axial extensions  132 A and  132 B of the body  114  may deform toward one another as the seal  100  is installed within hardware. For instance, the first and second axial extensions  132 A and  132 B can define a first angle, as measured with respect to the central axis A of the seal  100  in the uninstalled state, and a second angle, as measured in the installed state, that are different from one another. In an embodiment, the first angle can be less than the second angle. In an embodiment, the second angle may be closer to a side angle, a, of the side surface  154  of the support  140  than the first angle. In an embodiment, the side angle, a, of the side surface  154  can be at least 1°, at least 2°, at least 3°, at least 4°, at least 5°, at least 10°, at least 15°, or at least 20°. Deflection of the axial extensions  132 A and  132 B exhibited during installation can be at least 1°, at least 2°, at least 3°, at least 4°, at least 5°, at least 10°, at least 15°, or at least 20°. That is, deflection can cause the axial extensions  132 A and  132 B to move toward the support  140 . In a particular embodiment, deflection of the axial extensions  132 A and  132 B is no greater than the side angle, a, of the side surface  154  of the support  140 . At maximum deflection, which may not be required for effective sealing characteristic, at least one of the first and second axial extensions  132 A and  132 B (or at least a portion of the second energizing element  118  associated therewith) may contact the support  140 . In this regard, the support  140  may define a maximum deflection capability of axial extensions  132 A and  132 B. 
     In a particular embodiment, the second energizing element  118 , one or both of the axial extensions  132 A and  132 B, or a combination thereof, may contact the side surface  154  of the support  140  when the seal  100  is fully installed within the hardware. That is, for example, inner surfaces  122  or  124  of the volume  116  may contact the side surface  154  of the support  140 . The second energizing element  118  can resist the deformation of the axial extensions  132 A and  132 B, generating a loading force of the second energized jacket  104  with respect to the hardware. 
     It is noted that the second energized jacket  104  illustrated in  FIG. 2  includes rounded sealing features  130  whereas the second energized jacket  104  in  FIG. 3  includes non-rounded sealing features  130 . The seal  100  can utilize a second energized jacket  104  including either rounded sealing features  130 , non-rounded sealing features  130 , or both. The uninstalled height of the sealing features  130  illustrated in  FIG. 3  may be measured by a relative height from the central axis A of the seal  100  instead of the height from the radially outer surface  128  ( FIG. 2 ). In this regard, the sealing feature  130 A in  FIG. 3  is taller than sealing feature  130 B. 
     As illustrated in  FIG. 2 , the seal  100  can further include a plurality of seal rings  156 . In an embodiment, the seal rings  156  can define a chevron style packing. The seal rings  156  can be disposed on a relatively low-pressure side of the seal  100 . In an embodiment, the plurality of seal rings  156  can define a second axial end  158  of the seal  100 . The plurality of seal rings  156  can include, for example, a first axial end seal ring  160  and a second axial end seal ring  162  disposed on axial ends of the plurality of seal rings  156 . Second axial end seal ring  162  can define the second axial end  158  of the seal  100 . In an embodiment, an axial end of the second axial seal ring  162  can be planar. That is, for instance, the axial end of the second axial seal ring  162  can be oriented normal to the central axis A of the seal  100 . In certain instances, the axial end of the second axial seal ring  162  can be adapted to engage with a stop feature in the annulus of the hardware. The stop feature can prevent extrusion of the seal  100  from the hardware through the low pressure side. In an embodiment, the stop feature can be a projection extending into the annulus of the hardware. In another embodiment, the stop feature can include an end surface of the annulus. 
     One or more intermediary seal rings  164  can be disposed between the first and second axial end seal rings  160  and  162 . In certain instances, the one or more intermediary seal rings  164  can include at least one seal ring, at least two seal rings, at least three seal rings, at least four seal rings, or at least five seal rings. In an embodiment, the intermediary seal rings  164  can include first seal ring(s)  166  and second seal ring(s)  168 . In a particular embodiment, the first and second seal rings  166  and  168  can be alternated. The first and second seal rings  166  and  168  can have same or different properties (e.g., size, material composition, shape) as compared to one another. For instance, in an embodiment, the first seal rings  166  can include a first material and the second seal rings  168  can include a second material different from the first material. By way of non-limiting example, the first seal rings  166  can have a lower coefficient of friction and be adapted to flow more readily upon application of loading forces while the second seal rings  168  can be more ridged and adapted to contain the flowing first seal rings  166  during loading. 
     In an embodiment, the first and second axial end seal rings  160  and  162  can include a first material composition and the intermediary seal rings  164  can include a second material composition different than the first material composition. By way of example, the first material composition can include a more resilient material and the second material composition can have a lower coefficient of friction. 
     In an embodiment, the first axial end seal ring  160  can define a first axial end surface  170  adapted to contact the body  114  of the second energized jacket  104 . In a more particular embodiment, the first axial end surface  170  of the first axial end seal ring  160  can be adapted to contact a surface of a hub  172  of the second energized jacket  104 . In the illustrated embodiment, the first axial end surface  170  of the first axial end seal ring  160  contacts the hub  172  of the second energized jacket  104  along a planar contact interface  174 . In an embodiment, the interface  174  can lie along a plane generally perpendicular with a central axis A of the seal  100 . As illustrated, the interface  174  can extend across an entire thickness of the first axial end seal ring  160 , hub  172 , or both. Use of a planar interface  174  between the second energized jacket  104  and the first axial end seal ring  160  may enhance sealing characteristics of the seal  100  as compared to non-planar interfaces, such as arched interfaces, multi-planar interfaces, or both. In certain embodiments, the interface  174  can be approximately uniform in shape, size, or both, as measured around the circumference of the seal  100 . In a non-illustrated embodiment, the interface  174  can be non-planar. 
     In a non-illustrated embodiment, the first axial end seal ring  160  can be integral with the second energized jacket  104 . That is, the first axial end seal ring  160  can be integral, or monolithic, with the body  114  of the second energized jacket  104 . In certain instances, the first axial end seal ring  160  may be defined as the portion of the body  114  that acts primarily to interface the second jacket  104  with the plurality of seal rings  156 . 
     In certain instances, elements of the seal  100  may freely float with respect to one another. That is, at least two of the first energized jacket  102 , the second energized jacket  104 , the spacer  136 , and the plurality of seal rings  156  may be adapted to axially translate with respect to one another. In an embodiment, at least two of the first energized jacket  102 , the second energized jacket  104 , the spacer  136 , and the plurality of seal rings  156  may be installed independently (i.e., at different times—e.g., in succession) with respect to one another. The elements of the seal  100  can be stacked prior to insertion into the hardware to ensure proper orientation during installation. 
       FIG. 4  includes a cross-sectional view of a seal  400  in accordance with another embodiment. The first energized jacket  402  can be similar to the first energized jacket  102  previously described. A spacer  404  can be disposed between the first energized jacket  402  and a second energized jacket  406 . 
     The second energized jacket  406  can include a first sealing element  408  defining a concavity  410  recessed from an axial surface  412  thereof and a second sealing element  414  disposed at least partially within the concavity  410 . The second sealing element  414  can define a concavity  416  recessed from an axial surface  418  thereof. An energizing element  420  can be disposed at least partially within the concavity  416  of the second sealing element  414 . 
     In an embodiment, at least 10% of the second sealing element  414  can be disposed within a volume defined by the concavity  410 , at least 25% of the second sealing element  414  can be disposed within a volume defined by the concavity  410 , at least 50% of the second sealing element  414  can be disposed within a volume defined by the concavity  410 , or at least 75% of the second sealing element  414  can be disposed within a volume defined by the concavity  410 . 
     In an embodiment, the second sealing element  414  can contact the first sealing element  408  along a surface of the first sealing element  408  defining the concavity  410 . In a more particular embodiment, the first and second sealing elements  408  and  414  can be close-fit with respect to one another. That is, for example, the contours of the mating surfaces of the first and second sealing elements  408  and  414  can be adapted to have similar shapes for close arrangement between the two parts. 
     In an embodiment, the concavity  416  of the second sealing element  414  can have a profile adapted to retain the energizing element  420  therein. For instance, the thickness of the concavity  416  can be less than the thickness of the energizing element  420  at, or near, the opening of the concavity  416 . 
     In an embodiment, the first and second sealing elements  408  and  414  can include complementary retention features  422  adapted to secure the first and second sealing elements  408  and  414  together. By way of non-limiting example, the complementary retention feature  422  can include a notch and groove adapted to snap fit together. 
     In an embodiment, the second sealing element  414  can include a multiple-piece construction. For instance, the second sealing element  414  can include a radially inner portion  424  and a radially outer portion  426  spaced apart from one another by the concavity  416 . The complementary retention feature  422  can prevent relative axial translation between the radially inner and outer portions  424  and  426 . 
     In an embodiment, the second sealing element  414  can define an axial end  428  having a profile adapted to mate with a surface  430  of the spacer  404 . Loading applied on the second sealing element  414  by the spacer  404  can bias the second sealing element  414  radially outward toward the hardware. In such a manner, the second sealing element  414  can either contact the hardware, bias the first sealing element  408  into the hardware, or both to form an effective sealing condition. 
     In an embodiment, the spacer  404  is axially spaced apart from the concavity  410  of the first sealing element  408 . In another embodiment, the spacer  404  is spaced apart from at least a majority of the concavity  416  of the second sealing element  414 . Use of a spacer  404  without support (e.g., support  140  previously described) may be suitable for applications where the energizing element  420  is a spring having a non-cantilevered profile. Use of a spacer support for non-cantilevered springs may result in damage to the non-cantilevered spring during high loading conditions. 
     EXAMPLES 
     A seal is installed in an assembly between a bore having a 46 mm diameter and a shaft having a 34.91 mm diameter. The seal has a central opening with a diameter of 33.78 mm and an outer diameter of 47.02 mm. The seal comprises the design illustrated in  FIGS. 1 to 3 . Specifically, the seal includes a first energized jacket  102 , a second energized jacket  104 , a plurality of seal rings  156  including two intermediary seal rings  164 , and a spacer  136  between the first and second energized jackets  102  and  104 . 
     To test fugitive emissions leakage, the assembly is cycled between room temperature (approximately 22° C.) and a cold temperature (−44° C.) at the rate illustrated in Chart 1 below. Helium is used as the test fluid with measurements made using a vacuum method defined in Annex A of ISO 15848-1. Leakage is measured per mm of stem diameter. 
     
       
         
           
               
             
               
                 CHART 1 
               
             
            
               
                   
               
               
                 assembly leakage rate measured according to ISO 15848-1 
               
            
           
           
               
               
               
               
            
               
                 Temperature 
                   
                 Cycle 
                 Leakage 
               
               
                 (° C.) 
                 Cycling 
                 Count 
                 (mbar*l/s) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 20.2 
                 before 50 cycles 
                 0 
                 6.1 × 10 −7   
               
               
                 20.4 
                 after 50 cycles 
                 50 
                 1.7 × 10 −9   
               
               
                 −44 
                 before 50 cycles 
                 50 
                     2.7 × 10 −10   
               
               
                 −44 
                 after 50 cycles 
                 100 
                     2.5 × 10 −10   
               
               
                 22.3 
                 before 50 cycles 
                 100 
                 1.3 × 10 −9   
               
               
                 22.9 
                 after 50 cycles 
                 150 
                 2.2 × 10 −9   
               
               
                 −44 
                 before 50 cycles 
                 150 
                 2.2 × 10 −9   
               
               
                 −44 
                 after 50 cycles 
                 200 
                 2.6 × 10 −9   
               
               
                 22.3 
                 before 5 cycles 
                 200 
                 6.1 × 10 −6   
               
               
                 22.6 
                 after 5 cycles 
                 205 
                 5.9 × 10 −6   
               
               
                   
               
            
           
         
       
     
       FIG. 5  includes a graph  500  depicting assembly leakage  502  as a function of temperature cycle. The temperature profile  504  is adjusted according to Chart 1 above. Class AH sealing performance is indicated by line  506 . Class BH sealing performance is indicated by line  508 . As illustrated, the assembly leakage  502  performed within both Class AH and Class BH criteria. More specifically, the sample seal exhibited a fugitive emission measured leakage rate (mass flow) less than 1×10 −5  mg*s −1 *m −1  per stem perimeter, as measured according to ISO 15848-1. The sample seal may exhibit the above leakage rate or better over endurance classes of CO1 (205 cycles), CO2 (1500 cycles), and CO3 (2500 cycles). 
     To test fugitive emissions leakage, the assembly is cycled between room temperature (approximately 22° C.) and an elevated temperature (160° C.) at the rate illustrated in Chart 2 below. Helium is used as the test fluid. Leakage is measured per mm of stem diameter. 
     
       
         
           
               
             
               
                 CHART 2 
               
             
            
               
                   
               
               
                 assembly leakage rate measured according to ISO 15848-1 
               
            
           
           
               
               
               
               
            
               
                 Temperature 
                   
                 Cycle 
                 Leakage 
               
               
                 (° C.) 
                 Cycling 
                 Count 
                 (mbar*l/s) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 22 
                 before 50 cycles 
                 0 
                     4.4 × 10 −10   
               
               
                 22 
                 after 50 cycles 
                 50 
                     3.7 × 10 −10   
               
               
                 160 
                 before 50 cycles 
                 50 
                 1.9 × 10 −7   
               
               
                 160 
                 after 50 cycles 
                 100 
                 8.4 × 10 −7   
               
               
                 22 
                 before 50 cycles 
                 100 
                 2.6 × 10 −7   
               
               
                 22 
                 after 50 cycles 
                 150 
                 1.7 × 10 −7   
               
               
                 160 
                 before 50 cycles 
                 150 
                 6.4 × 10 −7   
               
               
                 160 
                 after 50 cycles 
                 200 
                 1.2 × 10 −6   
               
               
                 22 
                 before 5 cycles 
                 200 
                 5.2 × 10 −8   
               
               
                 22 
                 after 5 cycles 
                 205 
                 1.0 × 10 −8   
               
               
                   
               
            
           
         
       
     
       FIG. 6  includes a graph  600  depicting assembly leakage  602  as a function of temperature cycle. The temperature profile  604  is adjusted according to Chart 1 above. Class AH sealing performance is indicated by line  606 . Class BH sealing performance is indicated by line  608 . As illustrated, the assembly leakage  602  performed within both Class AH and Class BH criteria. More specifically, the sample seal exhibited a fugitive emission measured leakage rate (mass flow) less than 1×10 −5  mg*s −1 *m −1  per stem perimeter, as measured according to ISO 15848-1. The sample seal may exhibit the above leakage rate or better over endurance classes of CO1, CO2, and CO3. 
     In an embodiment, the annular seal is adapted to have a fugitive emission measured leakage rate (volumetric flow) less than 1.78×10 −7  mbar*1*s −1 *mm of stem, as measured according to ISO 15848-1. The measured leakage rate (volumetric flow) can be determined per mm of stem diameter through the stem seal system. In an embodiment, the annular seal is adapted to exhibit the above leakage rate or better over endurance classes of CO1 (205 cycles), CO2 (1500 cycles), and CO3 (2500 cycles). Such performance is typically only achievable using bellow-type seals. 
     In an embodiment, a seal in accordance with one or more embodiments described herein can be used in a valve, such as a control valve or an on-off valve. More specifically, the seal can be disposed between a shaft and bonnet of the valve, sealing an annulus therebetween. In certain instances, seals in accordance with one or more embodiments described herein can be used in oil and gas, such as on drilling rigs or in refining operations. Seals in accordance with embodiments described herein can operate with low fugitive emissions, meeting Class AH requirements as defined under ISO 15848-1. 
     Embodiment 1 
     An annular seal comprising:
         a first energized jacket defining a first axial end of the annular seal;   a plurality of seal rings defining a second axial end of the annular seal;   a second energized jacket disposed between the first energized jacket and the plurality of seal rings; and   a spacer disposed between the first and second energized jackets.       

     Embodiment 2 
     The annular seal of embodiment 1, wherein the annular seal is adapted to be installed within a hardware between a relatively high pressure region and a relatively low pressure region such that the first axial end of the annular seal is proximate the relatively high pressure region. 
     Embodiment 3 
     The annular seal of any one of the preceding embodiments, wherein the first and second energized jackets comprise different types of energizing elements as compared to one another, or wherein the first and second energized jackets comprise same types of energizing elements as compared to one another. 
     Embodiment 4 
     The annular seal of any one of the preceding embodiments, wherein the first energized jacket comprises a first body defining a volume at least partially containing a first energizing element. 
     Embodiment 5 
     The annular seal of embodiment 4, wherein the first energizing element comprises a double coiled spring, a single coiled spring, an advanced pitch spring, a cantilevered spring, or a plurality of cantilevered springs. 
     Embodiment 6 
     The annular seal of any one of the preceding embodiments, wherein the second energized jacket comprises a second body defining a volume containing a second energizing element. 
     Embodiment 7 
     The annular seal of embodiment 6, wherein the second energizing element comprises a double coiled spring, a single coiled spring, an advanced pitch spring, a cantilevered spring, or a plurality of cantilevered springs. 
     Embodiment 8 
     The annular seal of any one of embodiments 6 and 7, wherein the first and second bodies have different cross-sectional shapes as compared to one another, or wherein the first and second bodies have same cross-sectional shapes as compared to one another. 
     Embodiment 9 
     The annular seal of any one of embodiments 6-8, wherein at least one of a radially inner surface and a radially outer surface of the second body define an annular ridge. 
     Embodiment 10 
     The annular seal of embodiment 9, wherein the annular ridge comprises at least two annular ridges extending along the radially inner or outer surfaces of the second body. 
     Embodiment 11 
     The annular seal of embodiment 10, wherein the at least two annular ridges having different heights, as measured from the radially inner or outer surfaces. 
     Embodiment 12 
     The annular seal of any one of embodiments 9-11, wherein the radially inner and outer surfaces define a different number of annular ridges. 
     Embodiment 13 
     The annular seal of any one of the preceding embodiments, wherein the spacer comprises a base. 
     Embodiment 14 
     The annular seal of embodiment 13, wherein the spacer further comprises a support, as viewed in cross section, and wherein at least a portion of the support extends into a volume of the second energized jacket. 
     Embodiment 15 
     The annular seal of embodiment 14, wherein the support comprises a tapered profile defining a first thickness at a first axial location and a second thickness at a second axial location, wherein the first thickness is less than the second thickness, and wherein the first axial end of the annular seal is closer to the first axial location than the second axial location. 
     Embodiment 16 
     The annular seal of any one of the preceding embodiments, wherein the first energized jacket and the spacer are integral with one another. 
     Embodiment 17 
     The annular seal of any one of the preceding embodiments, wherein the first energized jacket and spacer contact one another along a planar interface disposed perpendicular with a central axis of the annular seal. 
     Embodiment 18 
     The annular seal of any one of the preceding embodiments, wherein, in an installed state, the spacer is adapted to contact only the first and second energized jackets, wherein, in an installed state, the spacer is adapted to be spaced apart from hardware into which the annular seal is installed, or both. 
     Embodiment 19 
     The annular seal of any one of the preceding embodiments, wherein the second energized jacket comprises an axially extending arm defining a first angle, as measured with respect to a central axis of the annular seal in an uninstalled state, and a second angle, as measured in the installed state, wherein the spacer comprises a support defining a side angle, as measured with respect to the central axis of the annular seal, and wherein the side angle of the support is closer to the second angle than the first angle. 
     Embodiment 20 
     The annular seal of any one of the preceding embodiments, wherein the plurality of seal rings comprise first and second axial end seal rings disposed on axial ends of the plurality of seal rings and one or more intermediary seal rings disposed therebetween. 
     Embodiment 21 
     The annular seal of embodiment 20, wherein the first axial end seal ring and the second energized jacket are integral with one another. 
     Embodiment 22 
     The annular seal of any one of the preceding embodiments, wherein the plurality of seal rings define a chevron style packing. 
     Embodiment 23 
     The annular seal of any one of the preceding embodiments, wherein the second energized jacket contacts the first axial end seal ring along a planar interface disposed perpendicular with respect to a central axis of the annular seal. 
     Embodiment 24 
     The annular seal of any one of the preceding embodiments, wherein the second energized jacket comprises:
         a first sealing element defining a concavity recessed from an axial surface thereof;   a second sealing element disposed at least partially within the concavity of the first sealing element, wherein the second sealing element defines a concavity recessed from an axial surface thereof; and   an energizing element disposed at least partially within the concavity of the second sealing element.       

     Embodiment 25 
     The annular seal of embodiment 24, wherein the second sealing element comprises a radially inner portion and a radially outer portion spaced apart from one another by the concavity of the second sealing element. 
     Embodiment 26 
     The annular seal of any one of embodiments 24 and 25, wherein the first and second sealing elements comprise complementary retention features adapted to prevent relative axial translation between the first and second sealing elements. 
     Embodiment 27 
     The annular seal of any one of embodiments 24-26, wherein the spacer is axially spaced apart from the entire concavity of the first sealing element. 
     Embodiment 28 
     The annular seal of any one of embodiments 24-27, wherein the second sealing element defines an axial end profile adapted to mate with a surface of the spacer. 
     Embodiment 29 
     The annular seal of any one of embodiments 24-28, wherein the energizing element of the second sealing element comprises a same type of energizing element as the first energized jacket, or wherein the energizing element of the second seal element comprises a different type of energizing element as the first energized jacket. 
     Embodiment 30 
     The annular seal of any one of the preceding embodiments, the annular seal of any one of the preceding embodiments, wherein the annular seal is adapted for use at temperatures in a range of −200° C. and 300° C., −50° C. and 200° C., or −46° C. and 200° C. 
     Embodiment 31 
     The annular seal of any one of the preceding embodiments, wherein the annular seal is adapted to have a fugitive emission measured leakage rate (mass flow) less than 1×10 −5  mg*s −1 *m −1  per stem perimeter through stem seal system, as measured according to ISO 15848-1. 
     Embodiment 32 
     The annular seal of any one of the preceding embodiments, wherein the annular seal is adapted to have a fugitive emission measured leakage rate (volumetric flow) less than 1.78×10 −7  mbar*1*s −1 *mm of stem, as measured according to ISO 15848-1. 
     Embodiment 33 
     The annular seal of any one of the preceding embodiments, wherein the annular seal is Class AH compliant, as measured according to ISO 15848-1. 
     Embodiment 34 
     The annular seal of embodiment 33, wherein the annular seal is Class AH CO1 compliant, wherein the annular seal is Class AH CO2 compliant, or wherein the annular seal is Class AH CO3 compliant, as measured according to ISO 15848-1. 
     Embodiment 35 
     The annular seal of any one of the preceding embodiments, wherein at least one of the first energized jacket, second energized jacket, or at least one of the plurality of seal rings comprises tetrafluoroethylene (TFE), polytetrafluoroethylene (PTFE), filled PTFE, modified PTFE, virgin PTFE, polyether ether ketone (PEEK), or any combination thereof. 
     Embodiment 36 
     The annular seal of embodiment 35, wherein at least one of the first energized jacket, second energized jacket, or at least one of the plurality of seal rings comprises a filler material. 
     Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed. 
     Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. 
     The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Separate embodiments may also be provided in combination in a single embodiment, and conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.