Slipline adjustable manhole seal

An arrangement for providing substantially liquidtight seals between a pair of nested generally coaxial elongated pipes near the respective pipe ends while allowing limited relative axial motion of the pipes as might occur due to temperature changes and dissimilar coefficients of thermal expansion for the pipes comprising:

• an outer pipe;
• an inner pipe axially extending in said inner pipe;
• said inner and outer pipes having dissimilar coefficients of thermal expansion;
• a pair of pliable sleeve-like gaskets having an outer circumference near one end approximately the same as the inner circumference of the outer pipe and an inner circumference near the opposite end approximately the same as the outer circumference of the inner pipe;
• each said gasket being situated in axially spaced locations on said inner and outer pipes to define an annular chamber between the outer pipe inner surface and the inner pipe outer surface;
• an expandable ring for forcing the sleeve one end radially outwardly into sealing engagement with the outer pipe inner surface;
• and a contractable ring for constricting the sleeve other end radially inwardly into sealing engagement with the inner pipe outer surface, said gasket sealing said annular space and permitting said inner pipe to convey fluids past any break in said outer pipe.