GB1268232A - Improvements in and relating to the method of laying underwater pipes - Google Patents

Abstract

1,268,232. Laying pipes under water; tools for coupling pipes; pipeline pigs. COMPAGNIE FRANCAISE DES PETROLES S.A. 15 July, 1969[14 Nov., 1968], No. 35547/69. Headings F2G, F2N and F2P. A method of laying underwater pipes comprises providing them with floats to give positive buoyancy to each pipe length, towing the lengths to the submersion site, injecting fluid of a density slightly greater than water into the first pipe length for submersion so as to render its buoyancy progressively negative, maintaining one end of the first pipe length for connection to a subsequent pipe length at a given depth, submerging the end of the second pipe length to the same depth by reducing its buoyancy, connecting the two submerged pipe lengths, expelling into the second pipe length the fluid contained in the first pipe length by injecting water, and repeating the process for each successive pipe length. The method may be preceded by laying a mooring cable for the pipe. A plug (Fig. 5, not shown) may be used to expel the fluid from one pipe to the next under hydraulic pressure and a plug stopping device is attached to the remote end of the particular pipe length to secure the plug after it has passed therethrough. The plug may also be used to assist in lining up successive pipe lengths and the pipe ends may be provided with traction arms (Fig. 6, not shown) for connecting to a traction system to bring the ends of successive pipe lengths together for connecting-up, and means (Fig. 8, not shown) for relatively rotating the ends of pipe lengths to align them may also be provided.