Offshore access systems have become increasingly more important to transfer people safely from vessels onto wind turbines. The Dutch have been pioneering in this area and continue to innovate to date. The EAGLE-ACCESS system is a good example of this Dutch innovative spirit.
At the start of October, over 30 invitees gathered at a safe distant to witness the demonstration of the EAGLE-ACCESS system (EAGLE) in Wierden, at the premises of steel manufacturer Staalbouw Boom. It promised to be a rainy day but the occasional ray of sunlight allowed for the demonstration to be observed clearly by the audience.
The EAGLE is a patented integrated electrically driven crane-based type of access system which is advertised by its inventors to be, amongst others, safe, light, simple and quick to use and to maintain, and not unimportantly, price competitive to current access systems in the market.
The brains behind the system are Marco Klitsie and Willem Prins. The two men had one vision from the start: to build an access system specifically for the offshore wind industry and one where its limitations are not determined by the system itself but the vessel it is placed on.
Klitsie, with previous experience in working with access systems, explains: “The current access systems are generally designed for the offshore oil and gas industry. They are the type of transfer systems whereby people cross over from the vessel to an offshore structure by means of a hydraulic, motion compensated gangway/bridge. These systems allow for many people to walk to work and back on a platform. However, the offshore wind industry requires only a few people and small cargoes to be transferred quickly to each turbine. Although fit for use, the current systems tend to be heavy, require a lot of deck space, thus larger vessels, use a lot of fuel and are, as a consequence, relatively expensive.”
One system for all functions
The EAGLE allows for the transfer of up to 4 persons or 1 tonne of cargo. In addition to this, it can also be used for deck handling. All deck handling can be done from 8 to 24 meters from the pedestal. No additional equipment such as lifts or rolling trolleys are required. Combining multiple functions already creates cost savings.
No complex technology
The technology behind the crane-type design is simple. The design only requires 3 electrical drives to control the tip. The system is 100% electrically powered (380 – 480V at 50-60 Hz), making large hydraulic power packs and generators unnecessary. It only needs a maximum power supply of 75 kilowatts from the vessel. At 27 tonnes, this system is much lighter than alternative systems weighing easily over 100 tonnes.
For use on smaller vessels
Due to the multiple use and simple technology, the system requires less deck space. The EAGLE is welded onto the deck of a vessel, or, in case of an integrated application, it needs only space for a pedestal. This is a big advantage over some of the access systems on the market, Klitsie says. In addition it can be placed anywhere on the deck not necessarily in a central space as with other systems. The EAGLE has a large reach, extending 25 metres high with a radius of 27 metres vertically from the pedestal. As a consequence, it can be placed at the aft, where the heave is more evident, and still have an optimised vessel heading. Placing the system at the aft leaves even more deck space, saves fuel and offers comfort. All this enables a large operational window. The large reach and minimal use of deck space allow the system to be used on much smaller vessels than the current transfer systems allow. Klitsie: “We can work from vessels of 65 meters and larger with DP2 systems.”
Easy mobilisation & installation
The system is transported in sections (3) to the port by road, via special transport. Once at the quayside next to a moored vessel , the system is assembled quickly and then lifted onto the vessel in just one lift using a standard mobile crane. Onboad the vessel the pedestal is welded to the deck and electrically connected. Klitsie: “The whole process can be done in one day.”
Quick & safe transfer
The cabin can be entered directly from the fixed landing station on deck or on the TP. No climbing is required. Once inside and with the cabin door closed the cabin frame is already connected. In addition to standard means of communication, the user can rely on the now common traffic-light colours and acoustic signals. Once the cabin has been lifted off the vessel, it is transferred to the TP where the user can step out following the green light. The complete transfer takes only a minute.
The demonstration of the EAGLE in Wierden showed the quick change between people and cargo transfer. If there is cargo that needs to be transferred, the cabin is uncoupled with a quick release and then the load can be latched on directly and transferred using the same procedure.
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No lifting cable is used and beside some winches there are not many moving parts. Using the 3D tip sensor with a damping system the vessel movements can be fully motion compensated during the transfer of either people or cargo, completing the transfer in comfort. In the first design review, performed by Controllab, it became clear that the tip occurrence of the system remains within the sphere of 20 cm during all operational phases. This was confirmed in all following tests and reviews including hardware and the electrical installations. All of this should lead to a high uptime.
In the tip of the crane there are also standardised cameras equipped with object detection from IFM, a well-known supplier of object detection systems. These can detect both people and objects, calculating the distance to the EAGLE. An alarm will alert the operator before any contact between the EAGLE and people or cargo.
One man can do the job
The release of the cargo is activated remotely by the operator. No banks man or for that matter anyone else is needed on the TP to guide the landing and the release of the cargo. This means that the cargo transfer can be made before the crew transfer has been completed thus further widening the operational window of the system. No additional cabin is required for the operation of the system. The EAGLE can be entirely operated from the bridge by the vessel’s crane operator. Only a small control area is needed in the wheelhouse. From the bridge, the operator gets a good overview of the operation and will have good communication with the DP operator or with the deck and people in the cabin. The cameras support the operator visually on a screen and with audio signal. The operation is semi-automatic. The operator can set target points and will have only to control the speed of the movements. The same goes for the landing.
All instructions and information required for the operation and maintenance of the EAGLE are provided. A qualified and experienced crane operator will be familiarized on the system. With no external operators or banksmen required, this contributes to cost savings. The EAGLE has a fully redundant design. If there is a power failure on the vessel there is a battery back-up pack available. The system can therefore be brought back at any time. In case of a repair there is a small set of spare parts available on board or otherwise quickly available from the company’s own stock or supplier. If technical faults occur which cannot be solved by the operator himself, remote support will be provided by one of EAGLE-ACCESS service engineers. All that is required is an internet connection.
All data including camera images is logged for training and work procedures improvement purposes. Klitsie: “We are currently developing a simulator together with Controllab which not only trains the operator but also forms a digital twin of the EAGLE. With the digital twin you can read your data back and learn from it. Combined with the data of a vessel you can also predict the workability of the system in combination with the vessel, a highly useful feature when talking to potential clients.
This article was written just before the EAGLE would complete static testing and start dynamic testing at Staalbouw Boom in Wierden. This next step will compare the expectations from the static tests with the dynamic setup. Klitsie: “We look forward to taking this next step with our partners. We are currently working on some minor open ends. For example, we still have a residual movement in the tip. We aim to work with standard equipment where possible but in this case the dampers we purchased did not perform as well as was expected, consequently we have decided to design and manufacture them ourselves.”
The company hopes to start the port and harbour acceptance assessment and sea trials in early Spring. Ideally they need a work period combined with the sea trials to perform a lot of personnel and cargo transfers provide a track record. The sea trials are supported by the Carbon Trust Offshore Wind Accelerator (OWA) Programme. Companies from around 75 % of the offshore wind market are partners of the programme. One of the programme’s partners will facilitate the offshore tests. At the time of the interview it was not known which company would be supporting the EAGLE. (May 2021 update: the sea trials have in the meantime taken place.)
Text: Sabine Lankhorst This article appeared in the December 2020 edition of the magazine.