During the first quarter of 2017, the TDD endured vigorous trials and tests at EON’s ‘Scroby Sands Offshore Wind farm’ together with vessel owners / operators Iceni Marine Services. The device was installed to vessel ‘Iceni Courage’ (South Cat 15 meter) by vessel builders ‘Alicat Workboats’, integrated and powered by hydraulic specialists ‘Hercules Hydraulics’ in Great Yarmouth, UK.
By the end of stage trials, the TDD outperformed expectations from all parties involved. A wave rider buoy issued by the OWA was deployed to provide accurate feedback and was followed by a thorough trials program carried out by Carbon Trust members.
Results from the OWA trials demonstrated that the TDD could hold its pivoting jaws with negligible vertical movement in wave heights of up to 2.7 meters. Sea states included seas from ahead, astern and a beam. This achievement was deemed ‘outstanding’ by OWA partners which reinforces the team’s belief that an innovative access / transfer system can improve and conduct safer transfers at sea, even in challenging conditions with wave heights of up to 3.1 meters with a CTV as little as 15 meters in length.
We believe the TDD will change the future of offshore transfers…
Although the primary goal was to create a system which would enable transfers in more adverse conditions on Offshore Windfarms, it goes without saying that the key feature of the TDD is its ability to substantially increase safety in all aspects of transfers offshore… Be it from a Crew Transfer Vessel to an offshore structure (windfarm, Sub Stations, Platforms), a small Cargo vessel or Safety Boat aiding Oil and GAS Rigs, a Pilot Vessel transferring a Pilot to a Ship or even being used as an additional feature utilizing a light weight device to aid compensated gangways (Walk2Work).
This mobile, compact, easily maintained system can improve all aspects of transfers conducted at sea with minimal change from current methods to be adapted.
INCREASING WORKABLE WEATHER WINDOWS
That said, it has proved to withstand adverse sea conditions, enabling a stable platform on a 15meter vessel in seas of up to 3.1 meters.
This is a huge accomplishment and increase to the current 1.2 – 1.5meter max wave height enforced by most offshore windfarm sites for similar size vessels.
This will undoubtedly 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.
THE TDD HAS THE POTENTIAL TO INCREASE ACCESSIBILITY TO THE TURBINES OF EXISTING VESSELS, WITHOUT PENALISING THE TRANSIT CAPABILITIES OR CARGO CAPACITY.
IN THE OWA WE ARE PROUD TO SEE HOW INNOVATIONS LIKE THE TDD ARE REACHING THE MARKET. THANKS TO TECHNOLOGIES LIKE THE TDD TURBINE AVAILABILITY WILL INCREASE & THE OVERALL LCOE FOR OFFSHORE WIND WILL CONTINUE TO DECREASE
- DAN KYLE SPEARMAN OF THE CARON TRUST.
OFFSHORE INDUSTRIES WE CAN IMPROVE
HOW IT WORKS
The TDD goes through a primary phase where the jaws take the shape of the cylindrical fender tube. This is shortly followed by a secondary phase known as “thrust-out”. A combined dampened stroke of 750cm enabled by hydraulic rams and accumulators.
The TDD can deploy on to a tube whilst the vessel is simultaneously in a roll, pitch and off centre whilst addressing all 6 motions of freedom – heave, pitch, roll, yaw, sway and surge. Conversely, due to mechanical advantage a vessel can obtain a higher level of grip with a proportionally reduced amount of propulsion, thus minimizing pushing force required to maintain a stable platform against offshore structures.
An additional (but optional) hydraulic assistance mode can be implemented, which operates in a similar mode to applying a brake pedal of a car. This optional ability to add clamping will also allow substitution or minimal propulsion, enabling transfers to light anchored structures such as floating LiDAR’s, anchored barges or jack-up vessels. This optional ability, whilst using little or no propulsion, also enables transfers in adverse weather conditions to ships under DP (where CTV’s / WFSV’s are instructed to push on with minimal propulsion as it can upset the mathematical model of the DP vessel).
Another key feature of the system is the ability to alter the lateral position without disengagement. This can be achieved by simply reducing forward propulsion and re-applying when at the desired height, enabling clamping with its RG Seasight-Fenders.
Concept Trials Footage
The priority throughout the development process has been to make the TDD fail-safe, ensuring that the risk of mechanical entanglement to any offshore structure is completely mitigated. This is achieved by making the amount of grip applied to the offshore structure relative to the propulsion applied not protruding 180 degrees of the receiving cylindrical tube. The key features required from the design and model testing work were to create a simple and lightweight device which can effectively stabilize, pin and grip the transfer position. Offshore Transfer Devices and Hercules Hydraulics have created a cushioned approach which will minimize impact loads and offer protection to the device, vessel and offshore structures in greater wave height conditions. In addition, this will aid fuel economy, as well as wear and tear to vessels engaged in prolonged transfer operations with personnel or equipment.
INVEST IN THE FUTURE OF
SAFE TRANSFERS AT SEA
Together with it’s contractors, Offshore Transfer Devices have now proven that the Tube Docking Device (TDD) can change the way offshore transfers are conducted. We are now looking to partner with an established marine engineering firm who can provide further expertise, venture capital, and assistance in gaining global market exposure.
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