Abstract: A test plug and method for isolating and testing a connection, such as a welded connection, which interconnects a wall of tank, vessel, or pipe to a branch pipe or nozzle. The test plug isolates the connection from the remainder of the tank, vessel or piping system and enables pressure/leak testing of the connection without requiring pressurization of the entire tank or vessel or a large section of the piping system. Further, the test plug can be utilized during welding operations to isolate harmful materials, vapors or fumes existing within tanks, vessels or piping systems from the weld location and to permit the flow of an inert gas to safely flush any potentially harmful vapors or the like away from the welding area.

Abstract: An outer diameter plug is provided for sealing the open end of a pipe. The plug is capable of being reused on a range of pipe outer diameter tolerances and of providing effective fluid-tight sealing over a range of internal pressures. The plug is particularly suited for use in pressure testing pipes by means of pressure fluids admitted to the pipes through the plug.