Internal seal for insulated steam injection casing assembly

Claim 1

An insulated casing assembly for conveying a high temperature fluid, said assembly comprising, in combination, a pair of casings each including concentric inner and outer tubular sections joined at their corresponding ends by separate ring members, the annular space between said inner and outer tubular sections being filled with thermal insulation material, the interior surfaces of said inner tubular section adjacent its ends being tapered to provide recessed sealing seats and the exterior surfaces of said outer tubular section being threaded adjacent its ends, a sealing ring having a radially outwardly extending rib and flexible oppositely axially extending sealing lips having tapered sealing surfaces, the inner diameter of said sealing ring being substantially equal to the inner diameter of said inner tubular sections, said sealing ring being positioned between adjacent ends of said pair of casings with said rib extending into the space between adjacent ends of said pair of casings, said sealing surfaces of said lips engaging said sealing seats of said annular tubular sections, and a threaded coupling sleeve engaging said threaded ends of said outer tubular sections and adapted when tightened to force said sealing surfaces of said lips into fluid and thermal sealing relation with said sealing seats, the width of said rib being such that the ends of said casings are out of contact with said rib when said seal is effected between said sealing ring and said casings.