Abstract: A closure for pipelines carrying a fluid under pressure, the closure includes at one or more seals located on a vertical sealing face of the barrel collar along a leak pathway between a horizontal sealing face of the barrel collar and an ambient environment. In some embodiments, the horizontal sealing face includes a primary seal. The one or more seals are adapted to prevent the escape of fluids having a lower molecular weight than that of the main pipeline product or fluid contained by the closure, and is arranged to alter a path of a leak pathway to the ambient environment and to cause at a pressure drop across the one or more seals. The closure may also include a leak check valve for blowdown.

Abstract: Embodiments of a plugging tool (10) of this disclosure a control bar head (20) and at least one sealing head (30, 40) pivotally connected to the control bar head, the control bar head including a stress suppressor (50) located at a lower end (25) of the control bar head, the stress suppressor including an elastomeric element (51). The stress suppressor can act as a dual-stage suppressor, there being a primary (first stage) and a secondary (second stage) stress suppressor or zone (50A, 50B). The primary stress suppressor has an arched-shaped lowermost end (58) located between a pair of spaced-apart feet (21) of the control bar head, the feet having lateral edges (23) and comprising the secondary stress suppressor. During rotation of the tool into the pipe, stress to the pipe is reduced in a range of 5X to 14X relative to a plugging tool without the stress suppressor.