Patent GB-1250032-A (GB)
Title: Floating device for laying a pipe on the bottom of the sea
IPC: B63B35/04
Filed: 1969-09-26
Abstract: 1,250,032. Laying underwater pipe-lines. INDUSTRIEELE HANDELSCOMBINATIE HOLLAND N.V. 26 Sept., 1969 [14 Oct., 1968], No. 47444/69. Heading F2P. A floating device for laying a pipe on the bottom of the sea consists of a vessel with a guide device for the pipe, and a device to keep the pipe under tensile stress, comprising a number of rotatable elements gripping on the outside of the pipe, such as wheels, said elements being located in planes running through the centre line of the pipe. Each wheel is coupled by a brake or clutch to an axle and thence to a power source such as an hydraulic cylinder, so that a tensile force may be applied to the pipe, energy being supplied to move the pipe in the direction of the tensile force and energy being accumulated when the pipe moves in the opposite direction. Fig. 1 shows an end view of the preferred embodiment, which shows four of the fourteen wheels 11 gripping pipe 15. The wheels, which turn about axles 19, Figs. 3, 4, may be moved towards or away from the pipe by means of screwed spindle 12 and hand wheel 13, in order to accommodate various sized pipes and to adjust the tension. The wheels in the two planes are staggered with respect to each other (Fig. 2, not shown) so that only two wheels contact any transverse pipe section, and therefore only two wheel units need to be disengaged at any one time when a weld or other discontinuity is moved through the tensioning device. Brake shoes (not shown) are secured to brake anchoring plate 21, Fig. 4, mounted on axle 19, and grip brake drum 22 which is secured to the rim 23 of the wheel. Hydraulic cylinder 26 and spring 27, mounted on plate 21 by means of holder 25, act on the brake control lever 29 via the rod 28 so that the brake is normally in its operating position and the whole combination of wheel, brake anchoring plate and axle 19 is supported freely rotatable in the fork legs 18. Two cylinders 31 and 32 are provided in the chamber 16 and the piston-rods of the pistons of said cylinders are connected to one another via the chain 33 which is in contact with the gear segments 30. Pressure in cylinder 31 is normally maintained above that in cylinder 32 by auxiliary cylinder 35. The cylinders thus apply a net tensile force to the pipe 15 through the wheels 11, expending energy to draw in the pipe when the stern of the ship sinks in a wave trough, and storing energy as the pipe is played out when the stern is raised by a wave crest, the energy required to meet frictional losses being supplied by motors 42 and 51 driving pumps 41 and 50. As the movement of the pipe takes the cylinder pistons to the extremity of their travel, projection 47 of the brake control mechanism abuts stop 48 and momentarily releases the brake, causing cylinder 31 to begin to reverse the movement of the axle and thus remove projection 47 from stop 48. This results in an equilibrium condition in which the brake slips but the torque, creating the tensile stress in the tube, is still transmitted. Because slippage between pipe and wheel occurs to a certain extent it is also necessary to disconnect the brake at intervals in order to set back the cylinder to its starting position. This is done separately with each wheel in order to minimize the decrease in the tensile force acting on the pipe. High pressure fluid is applied from pump 50 to the cylinder 32 of the relevant wheel through sliding means 46.