GB1348318A - Pipe line for the transport of cold liquids - Google Patents

Abstract

1348318 Thermally insulated pipes; pipe joints SHELL INTERNATIONALE RESEAKCH MAATSCHAPPIJ NV 19 April 1971 [28 Jan 1970] 20358/71 Headings F2P and F2G A pipe-line for the transport of cold liquids comprises two rigid coaxial pipes rigidly connected to each other such that at ambient temperature or operating temperature a high axial compression stress is present in one of the pipes, buckling of the pipes being counteracted by heat insulation material in the space between the pipes through which one pipe elastically supports the other. In one embodiment (Figs. 1, 4, not shown) the pipes (1), (2) are welded to each other at the ambient temperature without prestressing and on cooling to the operating temperature an axial tensile is induced in the inner pipe (1) with a corresponding compressive stress in the outer pipe (2). In the other embodiment, Fig. 2, compressive and tensile stresses are respectively induced at the ambient temperature in the inner and outer pipes 11, 12 by means of bolts 18 but on cooling to the operating temperature the thermal contraction of the inner pipe 11 reduces the prestresses in the pipes to substantially zero. The heat insulation material 15 may be a closed cell PVC or polyurethane foam and may be reinforced at 16 with a glass-fibre or natural fibre fabric or a metal matting. A slide layer, which permits the inner pipe to move axially of the insulation material may be provided between the inner pipe and the insulation and may comprise glass-fibre or polypropylene fabric, plastics foil, paper or jute. The inner pipe may be of 9% nickel steel or aluminium and the outer pipe of carbon steel and the outer pipe may be covered with a concrete jacket. Pipe joints.-A joint between two pipe-line sections, Fig. 5, may be made with two preformed connection pieces each comprising an inner pipe 21, a conical section 27, inner ring 28 and outer ring 26 (see also Fig. 3, not shown). Cams 29 are provided for prestressing the pipeline sections. The inner pipe 21 and outer ring 26 of each connection piece are welded at 42 and 41 respectively to the inner and outer pipes 11, 12 of the pipe-line sections. The inner pipes 21 are welded together at 43 and a ring 45 is welded at 46 to the outer ring 26 of one connection piece. The gap X between the ring 45 and the other connection piece is then closed by applying an axial force between the cams 29, 47 and the rings are welded together. In other embodiments (Figs. 6, 7, not shown) joints are made using single connection pieces (50) to (55) and (75) to (79) respectively. The gap X may alternatively be closed by a thermal method, e.g. cooling the inner pipe with solid CO 2 or liquid N 2 , or heating the outer pipe.