34 2 34 added seal assembly 220 uses only the rims 262 and 264 providing the pressure enhancement for the sealing against their surfaces 242 and 244 while upper sealing surfaces 234 and 236 are provided on the exterior of hanger 218 and the interior of housing 212 rim 262 is spaced from the exterior of hanger 218 and rim 264 is spaced from the interior of housing 212 to provide the annular recesses 270 and 272 which are exposed to pressure within the annular space below seal assembly 220 another modified form of the invention with sealing enhancement means on the housing only is shown in fig5 and uses similar part numbering but with the prefix 34 3 34 added seal assembly 320 uses only the outer upper and lower rims 360 and 364 this provides the recesses 368 and 372 which provides pressure enhancement for the sealing against the sealing surfaces 336 and 344 in this structure the pressure in the annular space is effective to provide the pressure enhancement from both above and below depending on the source of the pressure still another modified form of the present invention is shown in fig6 using similar numbering with the prefix 34 4 34 added seal assembly 420 utilizes the rim 458 on hanger 418 with the recess 466 exposed to pressure in the annular space above the sealing element 480 which is an annular element of soft.