The range of fibre rope cranes up to 400t combines our field-proven expertise in equipment employing braided fibre ropes in deepwater offshore operations with our offshore crane technology and control systems. Fibre rope cranes retain their full rated capacity down to maximum working depth, whereas a wire crane must be derated due to the weight of the steel wire.
At more than 2,500 metres a 250t fibre rope crane can do the same work as a 400t steel wire crane. The reason is that the braided fibre rope has approximately zero weight in water, whereas with wire the useful lift decreases with depth because of the suspended weight of the wire. Lower crane weight place less demand on ship stability, and also enables the option of using a smaller vessel for the same operation.
Fibre rope handling is taken care of below decks, in a compact system using the Rolls-Royce cable traction control unit (CTCU), which as well as hauling in and paying out the main rope also provides efficient active heave compensation (AHC). Braided fibre rope can easily have new sections spliced in if a part of it is damaged or abraded, and the CTCU is designed to accommodate the increased local rope diameter at the splices. Splicing can be done on board in a few hours.
The Rolls-Royce fibre rope management system is based on more than ten years of experience. This system monitors the condition of fibre rope in use, and manages replacements and inspections. It can be integrated in the Rolls-Royce EHM (equipment health monitoring system) so that information can be made available ashore for analysis.