Patent GB-1201530-A (GB)
Title: Marine apparatus for supporting a flexible elongate pipe during underwater laying thereof
IPC: F16L1/225
Filed: 1968-12-24
Abstract: 1,201,530. Underwater laying of pipe. BROWN & ROOT Inc. 24 Dec, 1968 [5 Jan., 1968], No. 61343/68. Heading F2P. Marine apparatus for supporting flexible pipeline during underwater laying thereof from a vessel 4 floating on the surface of a body of water comprises a longitudinally extending ramp 2 adapted to be secured, e.g. by a universal joint 8, at one end thereof to the vessel and to extend away therefrom generally downwardly into the water, the ramp including a plurality of pairs of longitudinally-spaced support members 6, 10, 12, each including at least one closed hollow chamber portion 20 to provide the support member with at least partial bouyancy; a pivotal connection positioned between each pair of adjacent support members for permitting relative vertical motion therebetween about a generally horizontal pivot axis; torque-applying means for applying torque at each pivot axis and varying the relative inclination of the adjacent support members; pipe contacting means secured to and spaced along the ramp, and adapted to underlie and support the pipe-line; and buoyancy control means connected with said support members for selectively and separately causing the passage of water between the interior and exterior of the hollow portion of at least one of the support members to selectively and separrately vary the buoyancy thereof. The buoyancy control means and the torque applying means co-operate to define means operable to selectively adjust the pivot inducing load imposed from the pipe through the adjacent support members on the pivotal connection means positioned therebetween and the buoyancy control means and the torque applying means are concurrently, and independently operable to cause the buoyancy of the ramp to be adjusted longitudinally along at least a portion of the ramp independently of the profile of the ramp while the torque applying means remains operable to constrain the support members to define a ramp profile of predetermined, and selectively adjustable, configuration. Each intermediate support 12 consists of a pair of hollow tubes 18 divided into flotation chambers 20 laterally aligned pairs of which are interconnected by hollow U-shaped cross tubes 19, each connected to a flooding valve 22, the upper ends of the laterally opposite pairs of chambers 20 being alternately connected, through manually operated valves 26, to air lines 24, 28. Each of the latter can be connected on board the vessel 4, with a source of compressed air, or to atmosphere, so that a diver can manipulate the values 22, 26 to individually adjust the buoyancy of the interconnected pairs of chambers 20. Double-sized buoyancy chambers 142on the lowermost, intermediate support 12 are connected to a valve 146 which is controlled by a pneumatic actuator 148 having air lines 156 leading to controls on board ship, the valve 146 being connected to the air lines 24, 28 through valves 158, 160, one of which is left open and the other closed. A pneumatic actuator 154, connected to the air lines 156, also controls a flooding valve 152 for the buoyancy chambers 142. The bottom support member 10 carries a supplementary buoyancy platform 60, the buoyancy of which is controlled, from the vessel, through a valve and control arrangement 166, 176, 178, 168, 172 and 174 similar to that used for the double-sized chambers 142. A pivot 14, with a horizontal axis, is located between each pair of longitudinally aligned tubes 18 and a mechanical jack 80, driven by a pneumatic, reversible, impact wrench 110, is connected between adjacent cross-tubes 19 and is controllable from the vessel to provide adjustable back-up support for the buoyant hollow tubes 18. The pipe-line is adapted to be supported on spaced pairs of rollers 50, which are arranged in V-form and are associated with pressure transducers 32, 34 which indicate, on board the vessel, the downward pressure of the pipe-line on the support rollers. Side indicator units 36, 38 also show whether the pipe-line is properly centred along the ramp. Each of the support members is also provided with an inclinometer 190, the buoyancy platform 60 being provided with a fathometer 194 and depth gauges, indicating the depth from the surface, may also be provided.