Smaller subsea construction vessels equipped with fibre rope can operate heavier equipment in deeper waters than their steel-wire crane-equipped counterparts
Subsea construction vessels can deploy heavier equipment in deeper waters using cranes with fibre rope, according to experts discussing the topic during Riviera Maritime Media’s Do more with less: with high-performance fibre rope for efficient subsea hoisting webinar, on 2 September.
Energy companies could employ smaller vessels for installing and removing subsea systems in deepwater oil and gas construction and decommissioning projects if these vessels employed cranes equipped with fibre rope instead of steel wire.
During the NOV Rig Technologies-sponsored webinar, TechnipFMC presented its motivation to use fibre rope solutions, based on its operational experiences. DNV GL talked about the safety aspects of using fibre rope for subsea installations and developments in certification.
“Fibre rope improves vessel operations and lowers lifetime maintenance costs”
Hampiðjan Offshore outlined specific requirements for ropes in subsea applications and NOV described specific lifting equipment solutions.
The panel consisted of TechnipFMC UK research and development technical manager for structures and lifting David Cannell, DNV GL senior principal specialist for fracture mechanics and non-metallics Vidar Åhjem, Hampiðjan director David Waage and NOV product line manager for lifting and handling Ronny Hoff.
Mr Cannell said: “Fibre rope buoyancy means it is neutral [weight] in water, increasing the capacity in deep water.”
Another benefit of fibre rope is the ability to replace sections of it during maintenance, without impacting performance or causing lengthy vessel downtime.
“Fibre rope improves vessel operations, lowers costs, reduces lifetime maintenance costs and creates significant time savings,” said Mr Cannell.
He said these advantages will drive more interest in using fibre rope for subsea lifting. “Our industry needs to work together to get the technology adapted,” he said. “Then the floodgates will open. We are getting there – we want to make sure fibre rope works properly.”
There was consensus from the panel for wider industry adoption of this technology. For this to happen, existing vessels would need to be upgraded, instead of owners ordering newbuild systems.
Mr Waage explained the performance of fibre rope, Hampidjan’s DynIce Warp, of which more than 12 km are now in use in maritime sectors.
He said the optimal wire rope should have low weight and high strength, good cycling bending performance, minimum temperature-induced elongation and good spooling performance.
Mr Waage said: “If we look at the construction, the optimised properties would be: high lateral stiffness, steel-like properties, high cross-sectional stiffness and strength member protected from particle ingression and abrasion with tightly braided cover.”
Optimal materials would have good abrasion resistance, bending properties, limited temperature-induced creep and be able to withstand long-term loads at higher temperature.
Mr Holt explained further how fibre rope has major weight benefits over steel wire, which leads to lower emissions from offshore construction projects.
“For deepsea operations, a traditional steel wire rope will add significantly to the working load of the crane with increasing depth,” he said.
“Neutrally-buoyant fiber rope enables a given deepsea lifting operation to be performed with a smaller crane and a smaller vessel” said Mr Holt.
He added: “Smaller vessels typically translate to lower vessel dayrates and reduced energy consumption, which in turn leads to reduced costs and CO2 footprint.”
Mr Åhjem explained how standards for fibre rope lifting systems were being developed to enable owners to retrofit existing vessels and cranes.
DNV GL’s E407 standard was developed with functionality assurance in mind. Mr Åhjem said there would be further developments to ensure these standards are not equipment specific.
“E407 standard currently takes a standard approach, but we want to make it modular,” Mr Åhjem said.
“We want full freedom of choice in functional assurance for equipment that is fit for purpose, to enable retrofitting,” he said.