Abstract:
Seal assemblies and methods for forming them are described. Aspects of the seal assemblies include a seal ring made of a relative soft material supported by a specially configured backing ring made of a much higher modulus material, such as ferrous and non-ferrous metal or engineered plastic. The seal assemblies may optionally include a retaining ring to prevent slippage relative to the environment or housing in which they are placed and to prevent shuttling. The seal assemblies may also optionally include an energizer to alter the force generating by a sealing lip on the seal ring. The seal assemblies preferably include a rigid hoop ring to minimize shrinkage due to thermal cycling.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This is a regular utility application of provisional application Ser. No. 61/162,554, filed Mar. 23, 2009, the contents of which are expressly incorporated herein by reference. This application may also be related to U.S. patent application Ser. No. 12/329,405, filed Dec. 5, 2008, which is a regular utility application of provisional application Ser. No. 61/012,179, filed Dec. 7, 2007, which bears the title SEAL ASSEMBLY FOR HIGH PRESSURE DYNAMIC AND STATIC SERVICES. The contents of the two applications are expressly incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0002]    Seal assemblies are generally discussed herein for sealing a first environment or chamber from a second environment or chamber of a machinery or equipment with particular discussions extended to shaft seals in which a seal is retained within a housing on a shaft and a constant pressure is exerted by the seal on the shaft to maintain a dynamic seal between the shaft and the seal. Seal assemblies for use in static services are also discussed. 
         [0003]    Seal assemblies for rotating, reciprocating, and face seal applications are well known in the art and are taught by, for example, U.S. Pat. Nos. 4,805,943; 4,830,344; 5,134,244; 5,265,890; 5,979,904; 5,984,316; 5,992,856; 6,050,572; 6,161,838; 6,264,205; and 6,641,141, the contents of each of which are expressly incorporated herein by reference. 
         [0004]    Prior art polytetrafluoroethylene (PTFE) based seals are preferred by some because they provide flexibility, low-friction, and self-lubrication when used in sealing arrangements with a moving shaft, such as a rotating or reciprocating shaft. However, PTFE material used in making seals has a natural tendency to cold-flow and creep, especially in high temperature, pressure, and surface velocity applications, which are common in the oil and gas industry and other applications. Thus, operating life of PTFE-based seals is generally shorter than preferred when placed in these applications and conditions. 
         [0005]    PolyEtherEtherKetone (PEEK) material, on the other hand, is better suited for high pressure, temperature and velocity applications. However, PEEK material is rigid and generally is not applicable or workable as a primary contact seal against moveable shafts, such as rotary or reciprocating shafts. 
       SUMMARY 
       [0006]    An exemplary method of making a seal assembly having shrink resistant support is discussed herein. In one example, a method is described comprising providing a seal ring comprising a holding bore and an inside diameter; placing a first backing ring made from a high tensile strength material adjacent the seal ring and in contact with the seal ring, said first backing ring having a base section having a first thickness; placing a second backing ring adjacent to and in contact with the first backing ring; said second backing ring comprising a base section having a second thickness; and wherein the second thickness is at least three times thicker than the first thickness. 
         [0007]    Another feature discussed herein is a seal assembly. In one example, a seal assembly is described comprising a rigid backing ring made of a first material having an axially extending flange; a seal ring positioned next to the backing ring and in mechanical engagement with the backing ring, placing a rigid hoop ring between the backing ring and the seal ring; said rigid hoop ring in contact with both the seal ring and the backing ring and has a tapered cone section that forms a line contact with the seal ring. 
         [0008]    In yet another example, a seal assembly is provided having alternative features. For example, the seal assembly for sealing engagement with a shaft can include a seal ring comprising an outside flange, an inside flange, a center channel section, and a holding bore; a backing ring in adjacent contact with the center channel section and having a flange extending co-axially with the inside flange of the seal ring; wherein the inside flange further comprises a seal lip comprising an arcuate section overlapping an end edge of the flange of the backing ring; and wherein a metal rigid hoop ring is located between the seal ring and the backing ring. 
         [0009]    Other examples are provided in the detailed description, drawings, and claims. Methods of making and using seal assemblies are also described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a cross-sectional side view of a seal assembly. 
           [0011]      FIG. 2  is a schematic perspective view of a rigid hoop ring. 
           [0012]      FIG. 3  is across-sectional side view of a seal assembly in accordance with a second example. 
           [0013]      FIG. 4  is a cross-sectional side view of a seal assembly in accordance with a third example. 
           [0014]      FIG. 5  is a cross-sectional side view of a seal assembly in accordance with a fourth example. 
           [0015]      FIG. 6  is a cross-sectional side view of a seal assembly in accordance with a fifth example. 
           [0016]      FIG. 7  is a cross-sectional side view of a seal assembly in accordance with a sixth example. 
           [0017]      FIG. 8  is a cross-sectional view of seal assembly in accordance with a seventh example. 
           [0018]      FIG. 9  is a cross-sectional view of seal assembly in accordance with an eight example. 
           [0019]      FIG. 10  is across-sectional view of seal assembly in accordance with a ninth example. 
           [0020]      FIG. 11  is a cross-sectional view of seal assembly in accordance with a tenth example. 
           [0021]      FIG. 12  is a cross-sectional view of seal assembly in accordance with an eleventh example. 
           [0022]      FIG. 13  is a cross-sectional view of seal assembly in accordance with a twelfth example. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiments of seal assemblies and methods related to seal assemblies and are not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the features and the steps for constructing and using the seal assemblies in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like or similar elements or features. 
         [0024]    With reference now to  FIG. 1 , there is shown a cross-sectional side view of a seal assembly  10  mounted in a gland, stuffing box, or sealing cavity  12  of a rotating, oscillating, or static equipment, such as a pump, compressor, turbine, gear box, pipe flange, or engine. The seal assembly  10  is mounted to an equipment housing  14 , which, as non-limiting examples, may be a seal box or a flange groove joining two piping sections together, and is preferably stationarily positioned relative to the equipment housing. A flange or end plate  15  is used to secure the seal assembly in place inside the groove of the equipment housing. The seal assembly  10  is generally circular in nature and comprises an inside diameter  16  designed to face the fluid to be sealed, which is shown schematically with a centerline  and may represent, for example, a pipe under high temperature and pressure, and an outside diameter  18  in static communication with an internal bore  22  of the equipment housing  14 . Known interference requirements between the seal and the equipment housing  14  may be used to implement the preferred seal assembly. 
         [0025]    In the embodiment shown, the seal assembly  10  is formed of several distinct components, namely a seal ring  24 , a rigid hoop ring  50 , a first backing ring  26 , a second or secondary backing ring  28 , and a energizer  30 , which may be a compressible resilient member, a canted-coil spring, cantilever vee spring, or an O-ring (not shown) of suitable resilient characteristics to provide a biasing force, as further discussed below. In the specific embodiment shown, the energizer  30  is a canted coil spring configured to change the resilient characteristic of the seal ring  24 , as further discussed below. In the preferred assembly, the seal ring  24  comprises a first outside flange  32 , a center channel section  34 , and a second outside flange  36 . The seal ring  24  is preferably made from a polymer material, which in one embodiment is a PTFE material. Other polymer and PTFE-based composite materials may be used as sealing components of the assembly, such as ultra high molecular weight polyethylene (UHMWPE). Both outside flanges  32 ,  36  extend axially from the center channel section  34  and terminate in a generally linear lip  38 . The lips  38  are compressed by both the equipment housing  14  and the end plate  15  and are opposed outwardly by the biasing force of the energizer  30  so that a seal is formed to seal the seams of the seal box between the high pressure region  38  and the low pressure region  40 . In a less preferred embodiment, the lips  38  make a single point contact with the equipment housing. Exemplary O-rings or energizers are disclosed in U.S. Pat. Nos. 4,893,795; 4,974,821; 5,108,078; 5,139,276; and 7,175,441, the contents of each of which are expressly incorporated herein by reference. 
         [0026]    In one exemplary embodiment, the second outer flange  36  of the seal ring  24  incorporates a recessed side wall  44  configured for snap-fit arrangement with the rigid hoop ring  50  and the two backing rings  26 ,  28 . The recessed spaced of the recessed side wall  44  is sized and shaped to accommodate the cone sections  46 ,  48 ,  52  of the three rings  50 ,  26 ,  28 , respectively. The mated assembly should be formed so that only the two lips  38  of the two exterior sides  54  project further radially outwardly than the remaining sides to ensure compression at the lips  38  by the end plate  15  and the equipment housing  14 . Alternatively or in addition thereto, the various rings  50 ,  26 ,  28  may be bonded to one another and to the seal ring  24  to ensure a fixed relative orientation between the various components. In the embodiment shown, the backing rings  26 ,  28  are made from a PEEK or a PEEK composite material. More preferably, the second backing ring  28  is made from a higher modulus material than the inside backing ring  26  to provide improved performance under certain conditions, such as elevated temperatures. The rigid characteristics of the two support rings  26 ,  28  allow the first backing ring  26  and the second backing ring  28  to resist pressure force from the higher pressure region  40  that would tend to push the seal ring  24  outwardly to the lower pressure region  42 . Thus, the backing rings  26 ,  28  act to resist distortion, cold flow or creep that may otherwise be experience by the seal ring  24 . In an alternative embodiment, the backing rings  26 ,  28  may be made from a suitably stiff strong material such as stainless steel, ferrous or non-ferrous metals, or engineering plastics. 
         [0027]    In one embodiment, the tapered cone section  62  ( FIG. 2 ) of the rigid hoop ring  50  is in direct contact with the seal ring to provide shrink resistance due to thermal cycling. As shown, the first backing ring  26  is also in direct contact with the seal ring  24  to prevent creep or extrusion of the seal ring along the pressure direction. 
         [0028]    The seal ring  24  has a holding cavity or bore  56  for capturing the energizer  30 , which in the embodiment shown is a canted-coil spring  30 , for example a radial or axial canted coil spring. The holding bore has a contour that is defined, at least in part, by geometry of the interior surface of the holding bore, which may be altered to create different holding space for the energizer  30 . Using the physical contour of the holding bore to modify the spring deflection will in turn allow the radial force acting on the sealing lips  38  to be adjusted upwardly or downwardly. The holding bore  56  further has two retaining lips  58  having a gap therebetween for placement of the energizer  30  into the holding bore. 
         [0029]    Refer now to  FIG. 2 , a schematic view of the rigid hoop ring  50  of  FIG. 1  is shown. In an embodiment, the rigid hoop ring  50  comprises a base  60  and a tapered cone section  62  comprising an opening  64 . With reference also to  FIG. 1 , the upper or first side  66  of the rigid hoop ring  50  is configured to mate directly against the seal ring  24  while the lower or second side  68  is configured to mate against the first backing ring  26 . The base  60  and the tapered cone section  62  are sized and dimensioned appropriately so as to form one of the snap-fit seal components of the seal assembly  10 . Due to its stronger tensile strength characteristic, the base  60  is significantly thinner than the corresponding base of the first backing and/or the second backing ring. In one embodiment, the rigid hoop ring  50  is singularly formed by molding, extrusion, or machining. As the rigid hoop ring provides backing support for the seal ring, it may also be referred to as a rigid hoop backing ring or simply backing ring  50 . 
         [0030]    In an embodiment, the rigid hoop backing ring  50  is made from a rigid metal or composite material. Preferably, the hoop ring is suitably stiff and strong such as stainless steel, ferrous or non-ferrous metals, or metal alloys. In a particular embodiment, the rigid hoop ring  50  has a higher tensile strength than the seal ring and therefore helps the seal ring to resist shrinkage due to thermal cycling. The tensile strength of the hoop ring  50  is preferably also higher than the two backing rings  26 ,  28 . In alternative embodiments, the hoop ring  50  has the same or less tensile strength as the backing rings  26 ,  28  but contribute to the overall strength when compared to similar seal assemblies without a hoop ring. Thus, by incorporating the hoop ring  50 , the seal assembly  10  of  FIG. 1  is understood to be one that is capable of minimizing the transfer of load and stresses from the seal ring  24  to the outer materials, such as the backing rings  26 ,  28 , as compared to the same seal assembly not incorporating a rigid hoop ring. The seal assembly may also be understood as having multiple backing rings for supporting a seal ring and resisting unwanted extrusion of the seal ring in the direction of high pressure to low pressure, said multiple backing rings comprising a backing ring made of a high tensile strength material located between a seal ring and a backing ring. In a particular embodiment, the backing ring made of the high tensile strength material has a base section  60  and a tapered cone section  62  comprising an opening and wherein the base section has a thickness that is less than a corresponding base thickness of the backing ring. In one embodiment, the base thickness of the first backing ring  26  is about 2 to about 5 times thicker than the base thickness of the rigid hoop ring  50  and the base thickness of the second backing ring  28  is about 3-7 times thicker. In yet another embodiment, the backing ring of lower tensile strength material is made of a PEEK or PEEK composite material. 
         [0031]      FIG. 3  shows across-sectional side view of an alternative seal assembly  70 . In one exemplary embodiment, the alternative seal assembly  70  is similar to the seal assembly  10  of  FIG. 1  but with a single backing ring  72  instead of two. Thus, the alternative seal assembly  70  is understood to be usable as a face seal and has a seal ring  24 , a rigid hoop ring  50 , a backing ring  72 , and an energizer  30 . In the embodiment shown, the backing ring  72  has abuse section  74  and a tapered cone section  76 . Because it acts as a single backing ring  72  without a secondary backing ring, the base section  74  of the backing ring  72  preferably has a thickness that is measurably thicker than a corresponding base section thickness of a dual backing ring assembly, as shown in  FIG. 1 . In one embodiment, the thickness of the base section of the backing ring  72  is at least 2 times thicker than the thickness of the base section of the rigid hoop ring  50 . In another embodiment, the thickness is between 2.1 times thicker to 9 times thicker. Most preferably, both the rigid hoop ring  50  and the backing ring  72  directly contact the seal ring  24  to support the seal ring from shrinking due to thermal cycling and from unwanted extrusion due to high temperature and pressure differentials between two different regions of the seal assembly. 
         [0032]    The seal assembly  70  may be used as a face seal by locating the same inside a groove of two stationary elements, such as the equipment housing  14  and the end plate  15 . The seal assembly  70  is configured to seal the equipment housing no that fluid from the high pressure region  40  does not leak across into the low pressure region  42 . 
         [0033]      FIG. 4  is a cross-sectional side view of an alternative seal assembly, which is generally designated as  76 . In one embodiment, the seal assembly is similar to the seal assembly shown in  FIG. 1  and comprises a seal ring  24  having an energizer  30  disposed in a holding cavity, a rigid hoop ring  50 , a first backing ring  26 , and a second backing ring  28 . The seal assembly  76  is understood as having a similar configuration as the seal assembly of  FIG. 1  with the exception of how the assembly is applied. In the present embodiment, the seal assembly  76  is used as an outside face seal in that fluid from the outside high pressure region  40 , such as hydrocarbon gas, is prevented from leaking into the housing or pipe, which has a lower pressure region  42 , for example of another hydrocarbon gas. The housing, pipe, or shaft is shown schematically with a centerline  and is attached to an equipment housing  14  and end plate  15 , such as a pair of mating pipe flanges. 
         [0034]      FIG. 5  is across-sectional side view of yet another seal assembly, which is designated generally as  78 . The seal assembly is similar to the seal assembly of  FIG. 3  but for use as an outside face seal, such as that disclosed with reference to  FIG. 4 . 
         [0035]    With reference now to  FIG. 6 , there is shown a cross-sectional side view of a seal assembly  80  mounted in a gland, stuffing box, or sealing cavity  82  of a rotating, oscillating, or static equipment, such as a pump, compressor, turbine, gear box, or engine. In a particular application, the seal assembly  80  is mounted in a roughneck flange or coupling  84  and is preferably stationarily positioned relative to the flange or coupling. The seal assembly is generally circular in nature and comprises an inside diameter  86  in dynamic sealing communication with a shaft  88 , shown schematically with a centerline and may represent, e.g., a pipe. The seal also has a non-uniform or varying outside diameter  90  in static communication with an internal bore  92  of the equipment housing  84 . Known interference requirements between the seal and the shaft and between the seal and the equipment housing  84  may be used to implement the preferred seal assembly. Although the seal assembly  80  is described for use in a roughneck flange application, such as for joining two pipes or two sections having offset together, it may be used in a rotating or reciprocating shaft application. 
         [0036]    In one embodiment shown, the seal assembly  80  comprises a plurality of distinct components, namely a seal ring  91 , a rigid hoop ring  94 , a first backing ring  96 , a second backing ring  98 , and an energizer  30 , which may be a resilient member, a canted-coil spring, cantilever vee spring, or an O-ring (not shown) of suitable resilient characteristics to provide a biasing force, as further discussed below. In the specific embodiment shown, the energizer  30  is a canted coil spring. In the preferred assembly, the seal ring  91  is similar to the seal ring  24  shown with reference to  FIG. 1  with at least two exceptions. In the present embodiment, the seal ring  91  comprises a projection or bump  100  for mating engagement with a notch or recess  102  formed on the primary backing ring  96 . The engagement between the two secures the seal ring  91  to the backing ring  96  in fixed relative orientation. The centerline of the seal assembly has also changed, which changes the direction of the inside and outside diameters of the present seal assembly compared to the seal assembly of  FIG. 1 . 
         [0037]    In one embodiment, the rigid hoop ring  94  is wedged between the seal ring  91  and the first or primary backing ring  96 . In a particular embodiment, the rigid hoop ring  94  is wedged between the recessed side wall  44  of the outside flange of the seal ring and the backing ring  96 . The two backing rings  96 ,  98  and the rigid hoop ring  94  support the seal ring  91  from creep and cold flow due to elevated temperatures and differential pressure between the higher pressure region  40  that tends to push the seal ring  26  outwardly towards the lower pressure region  42 . Thus, the rigid hoop ring  94  is understood to provide added backing and support to resist distortion, such as shrinkage, compared to similar seal assemblies without a rigid hoop ring. Note also that as the backing ring  96  directly contacts the seal ring, it prevents or reduces the possibility of unwanted extrusion that tends to push the seal ring in the direction of pressure gradient. 
         [0038]    In one embodiment, the primary backing ring  96  incorporates a first outside flange  104  and a second outside flange  106  having a recess  102  formed thereon. The two outside flanges  104 ,  106  support corresponding outside flanges of the seal ring  91  from distortion. However, as the rigid hoop ring  94  contacts a part of the center channel flange and the exterior flange  36  with the recessed side wall  44  but not the other exterior flange, the seal ring  91  has a non-uniform backing configuration. More specifically, the seal ring  91  comprises two outside flanges and wherein a first outside flange is configured for mating against a shaft or pipe and has a backing support structure comprising at least one backing ring and one rigid hoop ring with enhanced back support that is more resistant to distortion and creep than the other outside flange. 
         [0039]    The present seal assembly  80  is further understood to comprise a seal ring having a holding bore and a rigid hoop ring  94  positioned between two outside flanges  104 ,  106  and a center channel flange of a backing ring  96 . In one specific embodiment, the rigid hoop ring  94  is located against a recessed side wall  44  of an outside flange  36  of the seal ring. The seal assembly is further understood to comprise a backing ring that fully circumscribes a rigid hoop ring. Although the rigid hoop ring forms a line contact with the backing ring, in one embodiment, detents or undercuts may be incorporated to inter-engage the two to fix them in relative orientation. 
         [0040]    In one embodiment, a center channel extension  110  extends from the center channel flange  108 . The second backing flange  98  has a similar extension that together with the extension  110  of the first backing flange occupy the enlarged bore section  112  of the equipment housing. To ensure adequate or proper axial positioning of the seal assembly  80  within the stuffing box  82 , an extension shim  114  and a seal shim  116  may be incorporated. 
         [0041]      FIG. 7  is a cross-sectional side view of an alternative seal assembly, which is generally designated  116 . In one embodiment, the seal assembly  116  is similar to the seal assembly  80  of  FIG. 6  with at least one exception. In the present embodiment, a single backing ring  118  having two outside flanges  104 ,  106  is incorporated. The single backing ring  118  has a center channel section having a thickness that is roughly the thickness of the two center channel sections of the two backing rings of  FIG. 6 . 
         [0042]      FIG. 8  is a cross-sectional side view of still yet another seal assembly, which is generally designated  118 . In one embodiment, the seal assembly  118  is similar to the seal assembly  116  of  FIG. 7  but with at least two differences, namely it does not have a center channel extension and its use with reciprocating shaft  120 , applications Thus, an example is understood to include a seal assembly having a first outside flange having a sealing lip  38  for mating with a stationary equipment housing and a second outside flange having a sealing lip  38  for dynamic mating with a reciprocating shaft  120 . In a specific embodiment, a rigid hoop ring  94  is incorporated for reinforcing a recessed side wall  44  of the seal ring  91 . The seal assembly is understood to include rings configured to prevent distortion, creep, shrinkage, and unwanted extrusion of the seal ring that is incrementally better than similar seal assemblies without a rigid hoop ring. In another specific embodiment, the backing ring  119  is singularly formed from a rigid material, such as from a PEEK or a PEEK composite material, having a center channel section having a thickness that is at least 3 times thicker than the thickness of the base section of the rigid hoop ring  94 . More preferably, the thickness is about 6 times to about 12 times thicker. A groove or bump  117  may be incorporated to facilitate alignment of the seal assembly  118  in the stuffing box. 
         [0043]      FIG. 9  is a cross-sectional side view of still yet another seal assembly  122 . The present seal assembly  122  is similar to the seal assembly  116  of  FIG. 8  with at least one exception. In the present embodiment, two backing rings  124 ,  126  are incorporated with the first backing ring  124  having an arcuate back wall  128  for mating with a concave center wall  130  of the second backing ring  126 . The various components may snap-fit together and may optionally be bonded together. 
         [0044]    With reference now to  FIG. 10 , there is shown a cross-sectional side view of a seal assembly  130  mounted in a gland, stuffing box, or sealing cavity  132  of a rotating equipment, such as a pump, compressor, turbine, gear box, or engine. The seal assembly  130  is mounted to a gland or equipment housing  134  and is preferably stationarily positioned relative to the housing. The seal assembly  130  is generally circular in nature and comprises an inside diameter  136  in dynamic sealing communication with a shaft  138  and an outside diameter  138  in static communication with an internal bore  140  of the housing  134 . Known interference requirements between the seal and the shaft and between the seal and the housing may be used to implement the preferred seal assembly. 
         [0045]    In the embodiment shown, the seal assembly  130  is formed of several components, including a backing ring  142 , a seal ring  144 , an inner retaining ring  146 , and an energizer  30 . In one embodiment, a rigid hoop ring  148  is incorporated between the seal ring  144  and the backing ring  142 . In the preferred assembly, the seal ring  144  comprises an outside flange  150 , a center channel section  152 , and an inside flange  154  and is made from a polymer material, which in one embodiment is a PTFE material. The inside flange  154  extends axially internally from the center channel section  152  and terminates in a generally linear lip  156 . The lip  156  is in dynamic contact with the shaft  138 , in a cross-sectional view, along a straight line. In a less preferred embodiment, the lip  156  makes a single point contact with the shaft. 
         [0046]    In one exemplary embodiment, the inside flange  154  further incorporates at least one notch or recess  158  formed along an external surface for mating with corresponding bumps or projections  160  formed on the backing ring  142 . The engagement between the two secures the seal ring  144  to the backing ring  142  in fixed relative orientation. In the embodiment shown, the backing ring  142  is made from a PEEK or a PEEK composite material. Its rigid characteristic allows the backing and support ring to resist pressure force from a higher pressure region  40  that would tend to push or extrude the seal ring  26  outwardly to a lower pressure region  42 . Thus, the backing and support ring  142  acts to resist distortion of the seal ring. In an alternative embodiment, the backing ring  142  may be made from a suitably stiff strong material such as stainless steel, ferrous or non-ferrous metals, or engineering plastics. The backing ring  142  therefore contacts, directly or indirectly, the seal ring to support the seal ring. 
         [0047]    Also shown is a rigid hoop ring  148  incorporated to further reinforce the seal ring  144 . The rigid hoop ring  148  is preferably positioned next to the seal ring  144  and most preferably is located between the backing ring  142  and the seal ring  144 . The rigid hoop ring  148  further supports the inside flange  154  from shrinkage and directly contacts the flange of the seal ring. Thus, the present seal assembly is understood to provide greater resistant to shrinkage and unwanted extrusion, among other things, to the seal ring than a similar seal assembly without a rigid hoop ring. 
         [0048]    The inner retaining ring  148  is configured to mate with the outside flange  150  of the seal ring  144 . In one exemplary embodiment, a snap fit arrangement is provided to engage the two, which when assembled, create a holding bore  160  for capturing the energizer  30 . The energizer  30  may be a radial or axial canted coil spring and the surfaces of the inner retaining ring  146  and the seal ring  144  define the holding bore  160 . The holding bore therefore has a contour that is defined, at least in part, by the inner retaining ring and the seal ring, which may be altered to create different holding space for the energizer  30 . Using the physical contour of the holding bore to modify the spring deflection will in turn allow the radial force acting on the sealing lip  156  to be adjusted upwardly or downwardly. The inner retaining ring  148  may be made from a metal material or other high modulus materials. 
         [0049]      FIG. 11  is across-sectional side view of yet another seal assembly, which is generally designated  162 . The present seal assembly  162  is similar to the seal assembly  130  of  FIG. 10  with at least one exception. In the present embodiment, two backing rings are utilized  164 ,  166  instead of one, similar to the assembly of  FIG. 9 . 
         [0050]      FIG. 12  is across-sectional side view of another example of a seal assembly  168 . In the embodiment shown, the seal assembly does not incorporate a rigid hoop ring but only a single backing ring made of PEEK or PEEK composite material having sufficient center channel thickness and outside channel flange thickness to support the seal ring. The seal assembly may be used as an inside face seal as previously discussed with reference to  FIG. 3 . 
         [0051]      FIG. 13  depicts yet another seal assembly  170 , which is similar to the seal assembly of  FIG. 12 . However, in the present embodiment, the seal assembly  170  is applied as an outside face seal similar to the seal assembly shown and discussed with reference to  FIG. 4 . 
         [0052]    In certain embodiments, instead of using a PEEK or PEEK composite material to form a backing ring, an engineering plastic material may be used. Exemplary engineering plastics include Ultem® (PEI) amorphous polyetherimide polyethersulfone (PES), semi-crystalline polyphenylsulfide (PPS), semi-crystalline polyphthalamide (PPA), among others. Fibers Filler additives may be added to the alternative material to enhance their properties. 
         [0053]    Thus, an aspect of the present example is understood to include a seal assembly comprising a seal ring made of a first material, a first backing ring made of a second high tensile strength material having abuse section of a first thickness, and a second backing ring made of a third high tensile strength material having a base of a second thickness, and wherein the first and the second backing rings both contact the seal ring. In one particular embodiment, the second thickness is at least three times thicker than the first thickness. In another particular embodiment, the seal ring includes a holding bore sized to accommodate an energizer, which in particular embodiments may include a canted coil spring or an O-ring. 
         [0054]    The seal assembly of the present example is further understood to include a seal ring having an inside retaining lip that defines an inside diameter, a first backing ring made of a high tensile strength material in direct contact with the seal ring, and a second backing ring made of a high tensile strength material surrounding, at least in part, the first backing ring and the seal ring, and wherein an exterior wall surface of the second backing ring define an outside diameter. In one embodiment, the materials of the first backing ring and of the second backing ring are different. In one particular embodiment, the first backing ring is made from a metal material and the second backing ring is made from a PEEK or PEEK composite material or alternatively a conventional engineered plastic. 
         [0055]    Although limited embodiments of seal assemblies and their components have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. For example, a different combination of pliable seal ring plastic material and rigid plastic housing structure may be used instead of PTFE and PEEK. Furthermore, it is understood and contemplated that features specifically discussed for one seal embodiment may be adopted for inclusion with another seal embodiment, provided the functions are compatible. The present invention further includes methods for forming the seal assemblies as described. Accordingly, it is to be understood that the seal assemblies and their components constructed according to principles of this invention may be embodied other than as specifically described herein. For example, with reference to  FIG. 1 , the rigid hoop ring  50  may incorporate a rearwardly facing pin that fits into a bore formed on the first backing ring  26  to retain the two in fixed relative orientation. As additional examples, the rigid hoop ring may include a broached or knurled edge or a stepped lip that interlock with the adjacent backing ring. The invention is also defined in the following claims.