Compact unmanned platform

How does Compact unmanned platform work, step by step?

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   Step 1: Decide the manning philosophy first

   The choice between a manned and an unmanned platform is taken at the earliest stage, because everything downstream depends on it. The project weighs the size of the array, the distance from a suitable port, the accessibility of the site through the year, the availability of vessels and helicopters, the operating strategy and the cost of the accommodation against the cost of higher redundancy in the plant. That decision is documented and its consequences flow into the equipment specification, the safety case, the structure and the installation method. Changing it later is a redesign.

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   Step 2: Design for remote operation and infrequent visits

   An unmanned platform is designed on the assumption that nobody is there. Monitoring, control and protection are arranged so that the platform can be operated from shore, condition data is brought back continuously so that developing problems are seen early, and redundancy is provided where a failure would otherwise force an urgent visit. Auxiliary systems are simplified and made self-sufficient for long periods. The designer also thinks about what a visiting crew will need to do and lays the platform out so that routine work can be done quickly by a small team.

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   Step 3: Strip the topside to what is genuinely needed

   Accommodation, catering, permanent lifeboats and the systems that support living offshore come out, and with them a great deal of steel, weight and cost. What stays is the electrical plant and the systems that protect it, the safety systems that protect visiting crews, welfare adequate for a working day and in many designs a temporary refuge. The layout is compacted around the equipment. Weight control is aggressive throughout, because the point of the exercise is to bring the topside within the capacity of smaller and more available installation vessels.

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   Step 4: Match the foundation to the reduced weight

   A lighter topside opens up foundation options that a full collector platform cannot use, including monopile founding in suitable ground rather than a jacket. That in turn means the foundation can sometimes be installed by the same spread that is installing the turbine foundations, using the same equipment and the same crew, which is a real saving in mobilisation. The designer decides on the ground, the water depth and the loads, and confirms the foundation can carry the topside and its own environmental loading for the life of the project.

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   Step 5: Build and test the topside complete in the yard

   As with any offshore platform, the work is front-loaded into the yard. Equipment is set, cabling is installed and terminated, auxiliary and safety systems are installed and tested, and the platform is commissioned as far as it can be on land. On an unmanned platform this matters even more than usual, because the offshore working environment has no accommodation to support extended campaigns. The objective is a topside that arrives finished, with a short and defined offshore scope.

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   Step 6: Install in a single lift

   The reduced weight is the point of the whole design and it shows here. The topside can commonly be installed by a vessel that is smaller, cheaper and easier to book than the heavy-lift vessels a full platform needs, and in some cases by a vessel already on the project. The lift is planned, reviewed and executed like any other heavy lift, with the weather window and the rigging established beforehand. A shorter offshore campaign with fewer vessel dependencies is one of the strongest arguments for the compact approach.

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   Step 7: Hook up, pull in the cables and terminate

   The offshore hook-up completes the structural connections, removes the sea fastening, brings the safety and access systems into service and makes the platform ready for people to work on. Array and export cables are pulled in and terminated by specialist crews, each cable tested before it goes any further. Because there is no accommodation, this work is done by crews transferring daily or living on a vessel alongside, which makes the sequence more sensitive to sea state than it would be on a manned platform.

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   Step 8: Prove remote operation before handover

   Before the platform is handed over, the project proves that it can actually be run from shore, because that is the assumption the whole design rests on. Monitoring and control links are tested end to end, alarms are proved through to the people who will act on them, and the safety systems that protect visiting crews are demonstrated. Access arrangements and the emergency response plan for a platform with nobody on it are confirmed with everyone who has a part in them. Energisation itself is a controlled step carried out with the network operator under a formal authorisation regime.