| 摘要 |
1508624 Laying pipe-lines under water SAIPEM SpA 8 Sept 1975 [27 Sept 1974] 36917/75 Heading F2P A method of laying a pipe-line 3 in the sea by means of a surface vessel 1 having a stringer 2<SP>1</SP> and anchored to the sea bed by cables 6, 7 windable on winches 8, 9, comprises welding on the vessel a length of pipe to the free end of the pipe-line being laid, varying the forces exerted by the winches in such a manner as to impart a rapid movement to the vessel in the longitudinal direction of laying over a distance equal or substantially equal to the length of pipe added and, before termination of the rapid movement, applying to the vessel a compensating force of which the direction, sense and intensity are such that together with the forces exerted by the winches it serves to dampen in a continuous manner any induced oscillatory motion of the vessel, by reducing the amplitude of the oscillation produced. The compensating force is preferably generated by variable direction propulsors 12 the thrust of which can be varied by varying the angle of attack or speed of their blades, the direction, sense and intensity of their thrusts being determined and regulated by an electronic computer on the vessel. The method also preferably includes determining the position of the vessel, the angles and levels of the stinger and/or the pipe-line, the tensions in the anchoring cables and their angles of approach to the vessel, the speed and acceleration of the vessel at least during the rapid movement thereof, the direction sense and intensity of the external above-water forces and underwater currents, the number and indication of engines available for driving the propulsors and their speed, the thrust in direction sense and intensity of the propulsors and the forces exerted by the winches and feeding such data to the computer which processes the data and feeds information to the propulsors and winches in such a manner that the thrusts of the propulsors in direction sense and intensity and the forces exerted by the winches on the cables are varied in a continuous manner in accordance with predetermined adjustment criteria in phase opposition to the longitudinal component of the resultant of the forces which induce the oscillatory motion in the vessel or in phase opposition to said resultant when it is required to oppose transverse thrusts generated by underwater currents or other external forces.
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