Abstract: An improved inflatable seal apparatus (10) is disclosed which includes an annular or closed loop seal element (30, 64) captured during use within an annular supporting channel (20, 54) having a somewhat T-shaped cross-section which is narrowest at its inner, or outer diameter, depending on whether the seal element displaces radially into contact with a body at its outer surface (44) or, inner surface (78), respectively. The seal element is "double-acting" and, when uninflated, is substantially completely positioned within the channel. Upon inflation of the seal element, its inner and outer walls (34, 36 and 68, 70) deflect to essentially the same extent and in the same direction while its radially extending side walls (38, 72) move radially relative to the channel to comply with the simultaneous unidirectional deflection of the inner and outer walls and thus produce a unique "double-acting" displacement.

Abstract: A closure device useable as a test plug to block an extremity of a length of pipe for the pressure testing and repair thereof, including a cylindrical body component formed of two cylindrical half sections operationally readily detachably secured together. The assembled body component of such test plug includes a somewhat T-shaped peripheral channel narrowest at the outer periphery of such test plug body component operationally carrying a circular, inflatable, double acting seal element substantially completely positioned therein when uninflated. On inflation, inner and outer walls of such seal element deform to the same extent, while side walls thereof partially move out of such channel to permit such inner and outer wall deformation; each of such seal element side walls carrying a flange to limit the movement thereof out of such channel.