Apparatus and method for damming a pipeline

Claim 1

A puncture-resistant apparatus for temporarily damming, in its expanded configuration, the flow of fluid through a conduit of predetermined size to permit repairs to be made downstream of said apparatus, and being adapted to be passed into and out of said conduit in a collapsed condition, comprising the elements of: (a) a flexible, expandable outer bag having an ellipsoidal shape in its expanded configuration, the distance between elongate sides thereof being equal to or greater than the interior diameter of said conduit of predetermined size, said outer bag being formed of rubber or polymeric material and being adapted to flexibly conform to and seal tightly against a length of the interior surface of said conduit; (b) an inner, inflatable bladder having an ellipsoidal shape in its expanded configuration, the distance between elongate sides thereof being less than the interior diameter of said conduit of predetermined size, said inner inflatable bladder being substantially concentrically disposed within said outer bag so as to create an annular space between said bladder and bag and being formed of rubber or polymeric material; (c) a pressure transmitting liquid in the said annular space defined between said outer bag and inner bladder, said pressure transmitting liquid consisting essentially of water and a viscosity increasing agent; (d) an umbilical tube attached to said bladder adapted to convey pressurizing air to and from said bladder, said umbilical tube comprising a length of flexible tubing communicating at one end with said bladder and including valve means at the end remote from said bladder for controlling passage of pressurizing air; and (e) a lanyard for pulling the apparatus from said conduit of predetermined size, said lanyard being connected at one end thereof to said outer bag and extending along said umbilical tube to the end thereof remote from said bag.