Abstract: A downstream plug is disclosed of a simplified structure where a dragging disc is used at a rear end to induce the expansion of locking elements engaging the pipeline. The locking results in an expansion cone being firmly held in place and forming a solid counterpart to the elastomeric seal expanded by the cone.

Abstract: A pipeline plug is disclosed having an elastomeric disc-shaped sealing element provided with deforming means whereby the outside diameter of the elastomeric element is deformed to reduce its outside diameter to facilitate its insertion onto a pipeline. In another embodiment described, the plugging element and the deforming means are so arranged that when the deforming means act on the element, the latter is expanded into a sealing arrangement. The plugging elements are shown at one end of a spool assembly with resilient guide means to permit movement of the plug through a pipeline, but the plugging elements and their deforming means can also be used separately.

Abstract: An ice plug for defining a barrier in a pipeline section filled with water, comprises a hollow, cylindrical body enclosed at a front end and provided with guide means for sliding movement of the plug along and within the pipeline. The body has a diameter smaller than that of the pipeline to define with the latter an annular interspace enclosed at opposed axial ends of the plug. The thickness of the annular space is selected to allow free movement of the body through curves in a pipeline and to form a continuous, annular ice layer firmly engaging the inside wall of the pipeline and the outer surface of said body to thus form, together with the body, a temporary water impermeable barrier within the pipeline. A water supply system fills the interspace with process water.