Study on the Behavior of Under-Water Guide Wires and Cage for Cargo-Handling

Abstract

Guide wire system is a simple method for cargo handling between floating platform and drilling part of remote-controllable deep sea oil drilling units, which consists of a cage and guide wires connected with the auto-tension unit on the floating platform at the upper end and the drilling unit on the sea bed at the lower end. It is considered that this system has some problems with the use of the system in waves and tides as follows. (1) Tangle of the guide wires themselves. (2) Tangle between the guide wires and the cables or anchor chains of the floating platform. (3) Attack angle of the cage to vertical line near the sea bed is extremely large or not. Scale model test and simple theoretical calculations were made to solve the above stated problems and to obtain the data for design. From this study, following points were made clear. (1) As the natural period of guide wires is very large (above 10 sec. in actual case), tangle of the guide wires does not occur in this case. (2) Basic design data of the system may be predicted from the simple theoretical calculations.