Placing platform support structure on sea-bed - by lowering on ballasted pontoon via cables paid-out from deck level of lift pontoons

摘要

The structure is placed on a sinkable pontoon and thus taken to near its destination where the pontoon and/or the structure is coupled with floating lift pontoons via cables or the like with a paying-out mechanism e.g. linear hydraulic actuators or step-wise operating hydraulic clamp units. The cables are guided at pontoon deck level and paid-out whilst ballasting the carrier pontoon to lower this, pref. at a point adjacent to the destination, where the pontoon is released to remain in situ, the structure coupled and lightly raised, and the pontoons moved sideways for final placement of the structure. Used for placing e.g. platform support structure on seabed. The arrangement permits placing a heavy structure without the use of a heavy floating crane whilst maintaining full control of stability of the structure at all stages of the operation.