Abstract:
An electrical feed-through assembly and method of making an electrical feed-through assembly provide an electrical feed-through assembly that can survive exposure in a high pressure liquid, for example, seawater at least 9000 psi, for substantial periods of time, for example, twenty years, without substantial leakage of the high pressure liquid into or through the electrical feed-through assembly.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     This invention was made with government support. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to sealed electrical feed-through assemblies and, more particularly, to a sealed electrical feed-through assembly that has features configured to stop leaks from one or more potential leak paths. 
     BACKGROUND OF THE INVENTION 
     As is known, electrical feed-through assemblies are used in some applications under harsh environmental environments. For example, underwater electrical feed-through assemblies are used underwater in a variety of applications and to great depths and associated great pressures. Underwater, and in any high pressure fluid environment, it is recognized to be a very difficult problem to achieve an electrical feed-through assembly that does not leak, particularly when the electrical feed-through assembly is exposed to the high pressure environment for long periods of time, for example, for twenty years. 
     Conventional rubber O-ring seals are known to be able to survive high pressure environments without substantial leakage for shorter periods of time, but it is known that such seals tend to leak over longer periods of time. 
     It would, therefore, be desirable to provide an electrical feed-through assembly that can survive exposure in a high pressure liquid, for example, seawater at least 9000 psi, for substantial periods of time, for example, twenty years, without substantial leakage of the high pressure liquid into or through the electrical feed-through assembly. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, an electrical feed-through assembly includes a header having first and second opposing surfaces and having one or more sealed feed-through conductors passing through the header at least from the first surface to the second surface. The electrical feed-through assembly also includes a housing coupled to the header and a cured epoxy having solid glass beads mixed therein and disposed between the header and the housing. 
     In some embodiments, the electrical feed-through assembly can also include one or more wires coupled to the one or more sealed feed-through conductors adjacent to the first surface of the header. The one or more wires can have a wire insulation comprised of a fluorocarbon, an ethylene, a polyethylene, a propylene, a polypropylene, an olefin, a polyolefin, or an olefinic copolymer thereof. The electrical feed-through assembly can also have a cured adhesive-lined heat shrink tubing surrounding a portion of at least one of the one or more wires and a polyurethane potted structure coupled to the first surface of the header, the potted structure surrounding the one or more wires and the cured adhesive-lined heat shrink tubing. The heat shrink tubing can be comprised of a polyolefin. 
     In accordance with another aspect of the present invention, a method of making an electrical feed-through assembly includes providing a header having first and second opposing surfaces and having one or more sealed feed-through conductors passing through the header at least from the first surface to the second surface. The method also includes providing a housing and coupling the header to the housing with an epoxy having solid glass beads mixed therein and disposed between the header and the housing. 
     In some embodiments, the method can also include coupling one or more wires to the one or more feed-through conductors adjacent to the first surface of the header. The one or more wires can have a wire insulation comprised of a fluorocarbon, an ethylene, a polyethylene, a propylene, a polypropylene an olefin, a polyolefin, or an olefinic copolymer thereof. The method can also include applying an adhesive-lined heat shrink tubing to surround a portion of at least one of the one or more wires and potting a polyurethane potted structure potted to the first surface of the header, the potted structure surrounding the one or more wires and the cured adhesive-lined heat shrink tubing. The heat shrink tubing can be comprised of a polyolefin. 
     The above-described electrical feed-through assembly and method of making an electrical feed-through assembly provide an electrical feed-through assembly that can survive exposure in a high pressure liquid, for example, seawater at least 9000 psi, for substantial periods of time, for example, twenty years, without substantial leakage of the high pressure liquid into or through the electrical feed-through assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the invention, as well as the invention itself may be more fully understood from the following detailed description of the drawings, in which: 
         FIG. 1  is a pictorial section drawing showing an electrical feed-through assembly capable of surviving long periods of time in a high pressure liquid, wherein the electrical feed-through assembly includes a header, a housing, a boot, and one or more cables; 
         FIG. 2  is a cross section of an electrical feed-through assembly the same as or similar to the electrical feed-through assembly of  FIG. 1  showing potential leak paths and showing again a header, a housing, a boot, and one or more cables; 
         FIG. 3  is a flow chart showing a process for preparing the cables of the electrical feed-through assemblies of  FIGS. 1 and 2 ; 
         FIG. 3A  is a flow chart showing a process for preparing the headers of the electrical feed-through assemblies of  FIGS. 1 and 2 ; 
         FIG. 3B  is a flow chart showing a process for preparing the housings of the electrical feed-through assemblies of  FIGS. 1 and 2 ; 
         FIG. 3C  is a flow chart showing a process for preparing the boots of the electrical feed-through assemblies of  FIGS. 1 and 2 ; and 
         FIG. 4  is a flow chart showing a process for assembling the electrical feed-through assembly of  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an exemplary electrical feed-through assembly  10  includes a header  26  having first and second opposing surfaces  26   a ,  26   b , respectively, and having one or more sealed feed-through conductors. e.g., feed-through conductor  22 , passing through the header  26  at least from the first surface  26   a  to the second surface  26   b . The electrical feed-through assembly  10  also includes a housing  28  coupled to the header  26  and a cured epoxy  30  having solid glass beads mixed therein and disposed between the header  26  and the housing  28 . The cured epoxy  30  can be disposed on a variety of surfaces as shown. 
     In some embodiments, the electrical feed-through assembly  10  can also include one or more wires, e.g., wire  12   a , coupled to the one or more feed-through conductors  22  adjacent to the first surface  26   a  of the header  26 . The one or more wires  12   a  can have a wire insulation  14  comprised of a fluorocarbon, an ethylene, a polyethylene, a propylene, a polypropylene, an olefin, a polyolefin, or an olefinic copolymer thereof. For example, in some embodiments, the wire insulation  14  can be comprised of a selected one of polytetrafluoroethylene, polytetrafluoroethene, perfluoroalkoxy, fluorinated ethylene propylene, ethylene-tetrafluoroethylene, or polyvinylidene fluoride. 
     The electrical feed-through assembly  10  can also have a cured adhesive-lined heat shrink tubing (see,  66 ,  FIG. 2 ) surrounding a potion of at least one of the one or more wires  12   a  and a polyurethane potted structure  20  coupled to the first surface  26   a  of the header  26 . The potted structure  20  surrounds the one or more wires  12   a  and the cured adhesive-lined heat shrink tubing. 
     The electrical feed-through assembly  10  can also include a boot  18  disposed over the potted structure  20  and a band  24  coupling the boot  18  to the housing  28 . The boot  18  can have one or more finger-like extensions of the boot  18 , e.g., finger  18   a . In some arrangements, the wires, e.g., the wire  12   a , are within a cable  12  having a cable belt  12   b  or covering over the wires  12   a . In some arrangements, there are two or more wires, e.g.,  12   a , within the cable belt  12   b . In some arrangements, the two or more wires are arranged as twisted pairs of wires. 
     The electrical feed-through assembly  10  is described in greater detail in conjunction with  FIG. 2 . 
     Referring now to  FIG. 2 , an electrical feed-through, assembly  50  can be the same as or similar to the electrical feed-through assembly  10  of  FIG. 1 . In  FIG. 2 , physical elements are indicated by reference designations with solid leader lines and potential leak paths or potential leak path entry points are indicated by reference designations with dashed leader lines. 
     The electrical feed-through assembly  50  includes a header  82  having first and second opposing surfaces  82   a ,  82   b , respectively, and having one or more sealed feed-through conductors, e.g., feed-through conductor  80 , passing through the header  82  at least film the first surface  82   a  to the second surface  82   b . The electrical feed-through assembly  50  also includes a housing  112  coupled to the header  82  and a cured epoxy  106  having solid glass beads mixed therein and disposed between the header  82  and the housing  112 . In some arrangements the epoxy  106  is made by Magnolia Plastics under part number 55-2. 
     In some embodiments as shown, the housing  112  can be joined to a pressure vessel  116  by way of a continuous weld  114  or an epoxy. However, in other embodiments, there is no such weld  114  and the housing  112  is instead a part of the pressure vessel  116 . 
     In some embodiments, the electrical feed-through assembly  50  can also include one or more wires, e.g., wire  70 , coupled to the one or more feed-through conductors, e.g. feed-through conductor  80 , adjacent to the first surface  82   a  of the header  82 . The one or more wires  70  can have a wire insulation  70   a  comprised of a fluorocarbon, an ethylene, a polyethylene, a propylene, a polypropylene, an olefin, a polyolefin, or an olefinic copolymer thereof. For example, in some embodiments, the wire insulation  70   a  can be comprised of a selected one of polytetrafluoroethylene, polytetrafluoroethene, perfluoroalkoxy, fluorinated ethylene propylene, ethylene-tetrafluoroethylene, or polyvinylidene fluoride. 
     The electrical feed-through assembly  50  can also have a cured adhesive-lined heat shrink tubing, e.g., heat-shrink tubing  66 , surrounding a portion of at least one of the one or more wires  70 . The heat shrink tubing  66  can be a polyolefin heat shrink tubing lined with a heat-cured adhesive, for example, S1030 adhesive, as manufactured by Tyco-Raychem under part number S1030. 
     The electrical feed-through assembly  50  can also include a polyurethane potted structure  62  coupled to the first surface  82   a  of the header  82 . The potted structure  62  surrounds the one or more wires  70  and the cured adhesive-lined heat shrink tubing  66 . The polyurethane used for the potted structure  62  can be, for example, made by PRC-DeSoto International under part number PR-1574. 
     The material of the potted structure  62  is selected to not stress wires, e.g., the wire  70 , within the potted structure  62  when the feed-through assembly  50  is subjected to high pressure fluids. The material of the potted structure  62  is also selected to bond well to heat-shrink tubings  54 ,  66  and to the header  82 . 
     The electrical feed-through assembly  50  can also include a boot  58  disposed over the potted structure  62  and a band  110  coupling the boot  58  to the housing  112 . The boot  58  can have one or more fingers, e.g., finger  58   a . In some arrangements, the boot  58  is comprised of a polyolefin material. In some embodiments, the boot  58  is heat shrinkable when exposed to heat. 
     The electrical feed-through assembly  50  can also include a cured adhesive-lined heat shrink tubing  54  surrounding a selected part of the cable belt  52   a , in particular, a part of the cable belt passing through a finger  58   a  of the boot  58 . The heat shrink tubing  54  can be a polyolefin heat shrink tubing lined with a heat-cured adhesive, for example, S1030 adhesive, as described above in conjunction with the heat-shrink tubing  66 . 
     The boot  58  can be coupled with an adhesive  64  to the potted structure  62 , coupled with the adhesive  64  to the header  82 , coupled with the adhesive  64  to the housing  112 , and coupled with the adhesive  64  to the heat-shrink tubings  54 ,  66 . In some embodiments, the adhesive is the S1030 adhesive described above. 
     In some arrangements, the wires, e.g., the wire  70 , are within a cable  52  having a cable belt  52   a  or covering over the wires  70 . In some arrangements, there are two or more wires, e.g.,  70 , within the cable belt  52   a . In some arrangements, the two or more wires are arranged as twisted pairs of wires. 
     In some arrangements, the cable belt  52   a  is comprised of a selected one of a fluorocarbon, an ethylene, a polyethylene, a propylene, a polypropylene, or a copolymer thereof. For example, in some embodiments, the wire cable belt  52   a  can be comprised of a selected one of polytetrafluoroethylene, polytetrafluoroethene, perfluoroalkoxy, fluorinated ethylene propylene, ethylene-tetrafluoroethylene, or polyvinylidene fluoride. 
     In some embodiments, the header  82  can include a header body  84  having one or more holes, e.g., hole  98 , through the header body  84 , wherein the one or more feed-through conductors, e.g.,  80 , are disposed within respective ones of the one or more holes, e.g.,  98 . A non-conductive coating (NCC)  86  can be disposed on at least the first surface  82   a  of the header  82 . However, the NCC  86  can also be applied to other surface of the header  82  to which materials must bond, for example, the epoxy  106  and the adhesive  64 . 
     The non-conductive coating  86  can include a metal matching layer  88  comprised of a material selected to bond to the material of the header body  84 , and a ceramic layer  90  comprised of non-conducting ceramic disposed on the metal matching layer  88 . The header  82  can also include an epoxy  92  impregnating pores of the ceramic layer  90 . 
     The non-conductive coating  86  can be of a type made by TRI/Austin, Inc. under the name BOND-COAT™, wherein the metal matching layer  88  can be made by Sulzer Metco under part number 450NS for application to an aluminum substrate, Sulzer Metco part number 43C NS for application to a stainless or alloy steel substrate, or Praxair Surface Technologies part number CU-104-2 or Cu-103 for application to a copper beryllium alloy substrate. The ceramic layer can be made by Saint-Gobain Coating Solutions under part number 107. In some embodiments, the metal matching layer  88  can be about four mils thick and the ceramic layer  90  can be about ten mils thick. The epoxy  92  can be of a type made by Polyscience under the name EMBED-IT™. In some arrangements, the header body  84  is comprised of steel or aluminum, and the NCC coating  86  is selected accordingly. 
     In some embodiments, the header  82  can also include glass, e.g., glass  100 , disposed within the one or more holes, e.g.,  98 , and surrounding the one or more feed-through conductors, e.g.,  80 , so that the one or more feed-through conductors, e.g.,  80 , are not in direct contact with the header body  84 . The glass, e.g.,  100 , forms glass-to-metal seals  102 ,  104  at the header body  84  and at the one or more feed-through conductors, e.g.,  80 , respectively. 
     A primer layer  94  can be disposed upon the epoxy impregnation  92  of the ceramic layer  90  before the potted structure  62  is formed. The primer layer  94  can be of a type made by PRC-DeSoto International as part number PR-420, and can be applied to avoid the glass, e.g.,  100 . A primer layer, e.g.,  96 , can similarly be disposed upon an exposed surface of the glass, e.g.,  100 , before the potted structure  62  is formed. The primer layer  96  can be of a type made by Dow Chemicals as pail number Q1-6132, and can be applied to avoid the header body  84 . 
     Now turning to potential leak paths identified by reference designators with dashed leader lines, potential leak paths or potential leak path entry points are described on the left hand side of  FIG. 2 , but in relation to corresponding physical structures on the right hand side of  FIG. 2  merely to avoid overly densely spaced reference designations. Where a potential leak path entry point is shown, it will be understood that the potential leak can occur along a joint between materials at the potential leak path entry point. 
     A potential leak path  119  through the cable belt, e.g.,  52   a , in the absence of a breach of the cable belt  52   a , will have a low permeability of the surrounding fluid, for example, seawater, due to the above described selection of the material for the cable belt  52   a . However, if the cable belt  52   a  is breached, resulting in fluid leaking into the cable, e.g. the cable  52 , then the wires. e.g., the wire  70 , still has a low permeability of the surrounding fluid due to the above described selection of the material for the wire insulation  70   a.    
     However, if the cable belt is breached, a leak path  130  exists between the wires, e.g., the wire  70 , and the potted structure  62 . The wire insulation  70   a , which is selected to have low permeability to fluid by itself, can form a relatively weak bond to the potted structure  62 , resulting in the leak path  130  having a relatively high permeability to the fluid if the cable belt  52   a  is breached. However, the leak path  130  is blocked by the adhesive-lined heat-shrink tubing, e.g.,  66 , such that leak paths  132 ,  134  into and around the heat shrink tubing have very low permeability to the fluid. Essentially, the leak path  132  is blocked by the heat-cured adhesive, e.g.,  68 , and the leak path  134  at the outside of the heat-shrink tubing  66  is blocked by a superior bond between the material of the heat shrink tubing and the potted structure  62 . 
     It will be recognized that if the cable belt  52   a  is breached to the point where the wire insulation  70   a  is also breached, a conductor within the wire  70  will contact the surrounding fluid, resulting in low electrical resistance to fluid ground. However, other conductors (solid or stranded) will maintain a high electrical resistance to fluid ground due to the lack of leak path  140 . This is blocked by the bonded interface between the potted structure  62  and the glass  100  and between the potted structure  62  and the header body  84 . 
     A potential leak path  120  between the heat shrink tubing  54  and the cable belt  52   a  is blocked by the heat-cured adhesive within the heat shrink tubing  54 . A potential leak path  122  around the heat shrink tubing  54  is blocked by the adhesive  64  between the boot finger  58   a  and the heat shrink tubing  54 . 
     As is known, some materials tend to be permeable, meaning that they tend to transmit or leak gases or vapors such as water vapor on a molecular level. A potential leak path  128  is indicative of a vapor transmission path directly through the boot  58 . The above-described material of the boot  58  is selected to have very low permeability to water vapor. A potential leak path  126  is indicative of a vapor transmission path directly through the potted structure  62 . The above-described material of the potted structure  62  also has very low permeability to water vapor. 
     A potential leak path  146  is blocked by the adhesive  64 . A potential leak path  144  existing if the potential leak path  146  or other potential leak paths fails, is blocked by the above-described epoxy  106  filled with solid glass beads. 
     An epoxy tends to have the greatest bond strengths for bond thicknesses within certain minimum and maximum bounds that depend upon the type of epoxy. The solid glass beads within the epoxy  106  assure that the bond thickness of the epoxy  106  stays within those bounds, even when under the continual load of long-term exposure to high pressure. In some embodiments, the glass beads have a diameter of between about five and seven mils, which is suited for the above-described Magnolia 55-2 epoxy. However, glass beads with diameters greater than seven mils and less then five mils can also be used. In some embodiments, the amount of glass beads within the epoxy adhesive  106  is selected to be about four percent by weight, that having been determined to be an optimum concentration for bearing very high loadings. However, percentages higher or lower than four percent can also be used. It will be understood that, for the exemplary epoxy, Magnolia 55-2, a concentration of four percent by weight is equivalent to a concentration of about 1.8 percent by volume. 
     A potential leak path  142  is blocked by the adhesive  64  and a leak path  140  is blocked by adherence of the potted structure  62  to the header body  84 , which is enhanced by use of the NCC coating  86  and the above-described primer  94 . 
     Potential leak paths  136  and  138  are blocked by the glass-to-metal seals  102 ,  104 . 
     A region  118  within the housing  112  can be hollow or can be filled or partially filled with another polyurethane potted structure (not shown) to provide strain relief for inboard wiring, e.g., wire  108 . 
     A potential leak path  148  can be sealed by the weld  114  or it cannot exist at all in embodiments where the housing  112  is part of the pressure vessel  116 . 
       FIGS. 3-3C  show flow charts representative of steps that can be taken to prepare pairs of the feed-through assembly  50  of  FIG. 2 .  FIG. 4  shows a flow chart representative of a final assembly of the feed-through assembly  50 . While preparation steps of  FIGS. 3-3C  are indicative of preparation steps being performed prior to final assembly for clarity, it should be recognized that some of these steps can be performed during final assembly of  FIG. 4  rather than before final assembly. Order of steps associated with  FIGS. 3-3C  and  4  can be modified without departing from the spirit of the invention. 
     Referring now to  FIG. 3  and to  FIG. 2 , a process  150  is indicative of preparation of the cable  52  of  FIG. 2 . At block  152 , the cable  52  is cut and stripped to provide the wires, e.g., the wire  70 , exposed from the cable belt  52   a . End of the wires  70  are stripped to allow solder joints to the feed-through conductors, e.g.,  80 . 
     At block  154 , the cable belt  52   a  and the wire jackets  70   a  are cleaned with a solvent, for example, isopropyl alcohol. 
     At block  156 , for embodiments in which the wire jackets are fluoropolymer wire jackets, the wire jackets  70   a  can be etched, for example, with Fluoroetch by Acton Technologies, part number 41TCM-368. However, at block  156 , for embodiments in which the wire jackets are ethylene or propylene polymer wire jackets, the wire jackets  70   a  can be abraded, for example, with emery cloth having a grit between about 120 and 240. 
     At block  158 , the adhesive-lined heat shrink tubings, e.g.,  54 ,  66 , are applied and heat cured to the cable belt  52   a  and to the wires  70 , respectively. 
     At block  160 , the outer surface of the heat shrink tubings  54 ,  66  can be abraded, for example, with emery cloth having a grit between about 120 and 240, or alternatively, etched. 
     Referring now to  FIG. 3A  and to  FIG. 2 , a process  170  is indicative of preparation of the header  82  of  FIG. 2 . The process  170  does not show steps to install the glass  100  and pins  80  within the header body  84 . The metal of the header body  82  is sandblasted after the glass  100  is disposed in the holes  98  in block  172 . 
     At block  174 , the NCC coating  86  is applied as a metal matching layer  88  and a ceramic layer  90  (Sulzer Metco 450NS for aluminum substrates. Sulzer Metco 43C NS for steel alloy substrates, Praxair CU-104-2 for copper beryllium alloy substrates, and Saint-Gobain 107, respectively) and at block  176 , the ceramic layer  90  is impregnated, for example with the above described epoxy  92 . The impregnation can be formed in a multistep process. For example, the epoxy impregnation  92  can be applied to selected surfaces of the header  82  having the ceramic layer  90  and a vacuum can then be applied to draw gasses out of the porosity of the ceramic layer  90 . Subsequent relaxation of the vacuum forces the epoxy  92  into the ceramic layer  90 . Once cured, the epoxy impregnation  92  can be cleaned from the surface of the ceramic layer  90 , for example, by abrading or by light sand blasting. 
     At block  178 , selected surfaces of the header  82  are primed, for example with the above-described primer coating  94 . 
     At block  180 , selected surfaces of the glass  100  are primed, for example, with the above-described primer coating  96 . 
     Optionally, selected surfaces of the header  82  can be pre-coated with polyurethane, for example, the same material as the potted structure  62 , before the potted structure  62  is formed. 
     Referring now to  FIG. 3B  and to  FIG. 2 , a process  190  is indicative of preparation of the housing  112  of  FIG. 2 . At block  192 , the housing  112  can be sandblasted. At blocks  194 - 198  the housing  112  can be NCC coated, impregnated, and primed in the same way at that described above in conjunction with boxes  174 - 178  of  FIG. 3A . 
     Referring now to  FIG. 3C  and to  FIG. 2 , a process  210  is indicative of preparation of the boot  58  of  FIG. 2 . At block  212 , interior surfaces of the boot  58  can be cleaned with a solvent, for example with isopropyl alcohol. 
     Referring now to  FIG. 4  and to  FIG. 2 , a process  220  is indicative of an assembly of the prepared parts, prepared in the processes of  FIGS. 3-3C . At block  222 , the cable  52  can be installed through the boot  58 , i.e. through the boot fingers  58   a.    
     At block  226 , outboard wires, e.g., wire  70 , can be attached with solder to the header  82 , i.e., to the feed-through conductor  80 . 
     At block  228 , the outboard solder joints can be cleaned with a solvent, for example, isopropyl alcohol. 
     At block  230 , the potted structure  62  is formed. The potting can occur in a vacuum, to ensure that gasses in the potting material are expelled and do not form voids in the potted structure  62 . 
     At block  232 , inboard wires, e.g., wire  108 , can be attached with solder to the other ends of the feed-through conductors, e.g.,  80 . The inboard wires are within the pressure vessel  116 . 
     At block  234 , the inboard solder joints can be cleaned with a solvent, for example, isopropyl alcohol. 
     At block  236 , the header  82  can be bonded to the housing  112  with solid glass bead filled epoxy  106  described more fully above. 
     At block  238 , the surfaces of the potted assembly  58 , and selected surfaces of the housing  112  and the header  82  can be coated with adhesive  64 , for example, the above described heat-cured or heat-reflowed S1030 adhesive, or the adhesive  64  can be pre-applied to the inside surfaces of the heat shrink boot  58 , and the adhesive can be heat cured or reflowed to the potted structure  62 , header  82 , and housing  112 . When heat curing, the cables  52  can be protected from the applied heat. In some embodiments, prior to heat curing the boot  58 , the adhesive can also be applied to the inside of the boot fingers, e.g.,  58   a , and/or to the heat shrink tubing, e.g.,  54  over the cable belts, e.g.,  52   a.    
     At block  240 , the boot  58  can be further coupled to the housing  112  with a band  110 . 
     At block  242 , for arrangements is which the housing  112  is not a part of the pressure vessel, the housing  112  can be welded to the pressure vessel  116  with a weld  114 . 
     While certain materials and material layers are described above, it will be appreciated that other materials and material layers can be used so long as bonds between the various parts of the feed-through assembly  50  have sufficient strength to form water blocks under desired combinations of type of fluid and fluid pressure. The above described materials, material layers, and preparations can be used for the feed-through assembly  50  when used in seawater to a pressure of at least 9000 psi for a time period of at least twenty years. 
     All references cited herein are hereby incorporated herein by reference in their entirety. 
     Having described preferred embodiments of the invention, it will now become apparent to one of ordinary skill in the art that other embodiments incorporating their concepts may be used. It is felt therefore that these embodiments should not be limited to disclosed embodiments, but rather should be limited only by the spirit and scope of the appended claims.