Patent GB-1189622-A (GB)
Title: Improvements in or relating to Arrangements for Transferring Articles Between Two Stations.
Inventor: INGRAM DAVID JOHN
IPC: B66C21/00
Filed: 1968-02-29
Abstract: 1,189,622. Transhipping at sea; tension-regulating winding and paying-out apparatus. GENERAL ELECTRIC & ENGLISH ELECTRIC COMPANIES Ltd. 4 Feb., 1969 [29 Feb.. 1968], No. 9874/68. Headings B8B and B8E. A transfer arrangement for transferring pipes 10 between a supply vessel 1 and an oil drilling rig 2 comprises a winch unit 3 on the rig 2 with two main hydraulically driven winch drums 4, 5. A support cable, for a trolley 8, in the form of a loop passes from the rig 2 to the vessel 1 and comprises a cable 6 from the winch drum 4 passing over a pulley 7 on the vessel 1 and secured to the trolley 8. A further cable 15 passes from the winch drum 5 to the trolley 8 where it is secured. The trolley 8 comprises two pulley blocks 11,12 supported on the cable 6 by pulleys 9 connected by an adjustable distance bar 38. Each pulley block 11, 12 is associated with a lifting adapter 13, 14 supported by the cable 15, which passes over one of two support pulleys 16 on the block 11, around pulley 17 on adapter 13, over the other pulley 16, over support pulley 18 on the block 12, around pulley 19 on the adapter 14 and being finally attached to the block 12. Each of the adapters 13, 14 is arranged to support a pipe-lifting clamp 20. The cables 6. 15 together form a loop and both support the trolley 8 during transfer of a load, the tension in the cable 15 holding the adapters 13, 14 tightly against the blocks 11, 12. Transfer is accomplished by driving the winch drums 4, 5 in opposite directions. When the trolley 8 reaches a loading position over the deck of the vessel 1 a clamping device (not shown) clamps the support cable loop to the pulley 7 and prevents rotation of the latter. The winch drum 5 pays out the cable 15 and thus lowers the adapters 13, 14 with the clamps 20 to the deck of the vessel 1. The pipe clamps 20 are then attached to a pipe 10 and the procedure reversed. At the rig 2 the trolley 8 is clamped, by means not shown, and the pipe 10 lowered by paying out the cable 15 from the winch drum 5. A cable 22 carried by a drum 23 is connected directly to the supply ship 26 and is used to monitor the distance, and the rate of change of the distance, of the vessel 1 from the rig 2, the drum 23 being driven by a constant tension hydraulic power supply and coupled to a revolution counter and tachogenerator unit 27. During a transfer operation signals generated by the unit 27 are fed to a control system where they are used to control the swash-plate angles of the respective pumps to determine the cable pay-out and draw-in velocities of the winch drums 4, 5. In addition the tension in the upper and lower sections of the support cable loop are continuously monitored by tension sensors 24, 25 respectively associated with the winch drums 4, 5 and signals corresponding to these tensions are compared with nominal tension signals to produce tension error signals used to modify the control signals in such a manner that vertical load oscillations resulting from fluctuations in the movement of the vessel 1 relative to the rig 2 are damped. The apparatus may be used from ship to ship at sea and a hook 31 substituted for the pipe clamp 20, one load adapter only being used.