Abstract: A method and apparatus for expanding a replacement thermoplastic pipe installed within an existing conduit is provided. A pipe expansion apparatus having a flexible substantially cylindrical bladder and a relief valve to inflate the bladder to a predetermined gauge pressure and allow fluid to exit the expansion apparatus and fill and pressurize the area behind the apparatus is inserted within the collapsed pipe. Fluid, such as cold water, is introduced into the apparatus to inflate the inflatable section to conform substantially to the interior diameter and configuration of the existing conduit. As the area behind the expander fills with pressurized fluid, the expansion apparatus is pushed forward, thereby pushing and expanding the replacement pipe up against the interior of the existing conduit. Steam is injected ahead of the apparatus to maintain the replacement pipe in a heated flexible condition.

Abstract: In order to effectively seal the space between a preexisting pipe and a repair lining that has been inserted into the pipe and radially expanded in order to generally conform to the interior of the pipe, a form is inserted between the ends of the pipe and lining before the lining is radially expanded, the lining therefore conforms to the interior of the pipe along its length and to the interior of the form at its ends, the form is removed, a sealing ring is inserted into the space left by the form and is there sealingly compressed, and an element is inserted into that space axially outside the sealing ring in order to retain it in position and preferably to compress it axially of the pipe.