METHOD OF DIMINISHING THE CROSS SECTION OF AN OPENING OF A HOLLOW DEVICE LOCATED IN A FLOW PIPE

A method of diminishing the size of the cross section of an opening of a first hollow device located in an undersea flow pipe through which passes a fluid flow uses a second hollow device to be inserted into the undersea flow pipe, the second hollow device being provided with a leading portion and a trailing portion, the leading portion being of a smaller external diameter than the trailing portion, the second hollow device being provided with a passage extending longitudinally theretrough. Next a foam pig is inserted immediately after the second hollow device. Urged by the fluid flow, the foam pig displaces the second hollow device along said undersea flow pipe, until the second hollow device encounters the first hollow device. The leading portion of the second hollow device is then inserted into an opening of the first device, thereby diminishing the size of a cross section of the opening.