Transfer device developer seeks partner to transition to the next phase

UK-based Offshore Transfer Devices has secured further funding from the Carbon Trust Offshore Wind Accelerator to support the commercialisation of its innovative offshore transfer system

Having completed a series of successful trials in 2017, the British company behind the development of the Tube Docking Device (TDD), is seeking an engineering company with whom it can work to bring the transfer system to market.

The TDD has already received support from the OWA, for design, fabrication, installation and sea trials, in order to prove the concept, and has demonstrated it has significant potential to improve the safety and performance of crew transfer vessels (CTVs).

Offshore Transfer Devices director and project manager Daniel James told OWJ that the latest round of support from the OWA aims to help commercialise the TDD by developing a business case and supporting the search for a business partnership to manufacture and supply the product into the offshore wind industry and related sectors.

Speaking to OWJ at the Seawork 2018 exhibition in Southampton, Mr James explained that although the primary goal in the development of the TDD was to create a system which would enable transfers in adverse conditions on offshore windfarms, it can enhance safety in a range of potential applications. These include crew transfer from a CTV to an offshore structure such as a wind turbine or substation but could also include diverse applications such as pilot boats or cargo vessels.

The TDD was designed to be compact, easy to maintain and afford greater access and workable weather windows, resulting in increased productivity and reduced losses caused by failed transfers in conditions where conventional access fender methods are not viable. It was also designed to ensure its use does not reduce the transit capability or cargo capacity of the vessel on which it is installed.

2017 saw the company complete initial sea trials, carried out on the CTV Iceni Courage at Eon’s Scroby Sands offshore windfarm. The trials saw Iceni Marine Services' 15 m vessel reinforced for the installation of the TDD. The company also worked closely with Hercules Hydraulics to integrate and power the system.

Mr James said the TDD “outperformed the expectations of all of the parties involved” during the trials, which demonstrated the TDD could hold its pivoting jaws with negligible vertical movement in wave heights of up to 2.7 m. It did so in seas from ahead, astern and abeam.

“This achievement was deemed ‘outstanding’ by the OWA partners,” said Mr James, “which reinforced the team’s belief that the TDD can make transfers at sea safer, even in challenging conditions.”

Most transfers from CTVs take place when the vessel is pushing against the structure of a turbine. A fender reduces movement between the CTV and the structure but does not eliminate it altogether. Mr James and his colleagues wanted to develop an alternative to this technique.

The key to the way it operates is that intensification of the clamping force it uses is provided by the vessel’s propulsion system. In the initial phase of attachment to a structure, the jaws take the shape of the fender tube. This is followed by a second phase known as ‘thrust out’, when the TDD ‘docks’. The device is designed to ensure that impact loads on the structure, the TDD and vessel are minimised.

The TDD can attach to a tube while a vessel is simultaneously rolling, pitching and off centre while addressing heave, pitch, roll, yaw, sway and surge. The design of the system is such that a vessel can obtain a higher level of grip with a proportionally reduced amount of propulsion, thus minimising the pushing force required to maintain a stable platform against offshore structures.

An optional hydraulic assistance mode can also be implemented, which is similar to applying the brake pedal of a car. This ability to add clamping will also allow substitution or minimal propulsion, enabling transfers to lightly anchored structures such as anchored barges or jack-up vessels. While using little or no propulsion, this mode of operation also enables transfers in adverse weather conditions to ships in dynamic positioning (DP) mode when CTVs are usually instructed to push-on with minimal propulsion as it can upset the mathematical model used in a DP system.

Another key feature of the system is the ability to alter lateral position without disengagement. This can be achieved simply by reducing forward propulsion and re-applying when at the desired height.

Mr James said the priority throughout the development process was to make the TDD fail-safe, ensuring that the risk of mechanical issues with offshore structures is mitigated. Work with Hercules Hydraulics, Offshore Transfer Devices has created a ‘cushioned’ approach to attaching to a structure that minimises impact loads.

Mr James told OWJ that the company is seeking an engineering firm with the resources and expertise to ‘catapult’ the TDD to market. “We have proved that the TDD works,” he told OWJ, “and hope to conduct a further series of trials in parallel with work with a consultant who will help us find the right engineering partner with whom to work.”