Overview
The increase of traffic, together with the presence of many old and not always well-maintained vessels, on the seas quite close to European coasts will increase the risk of having human, ecological but also economical disasters. The consequences of tanker accidents are often catastrophic, raising the issue of oil spills to the highest priority for the EU community.
Analysing accidents like the Erika and the Prestige, a clear need emerged for vessels specifically designed to recover oil pollution at sea (with efficient recovery tools, decantation and storage capacities), which have onboard tools to help them detect and track the pollutants. Also a clear need emerged to have a fast ship in transit in order to arrive quickly at the scene of the accident to operate oil recovery when the spill is still concentrated. It is also necessary to have a stable ship for rough weather conditions, which has oil recovery tools as well protected as possible from the sea in order to be able to operate in high seas.
The objectives of the OSH project were:
- to define the requirements of the OSH concept to respond to oil spill scenarios;
- to develop a trimaran vessel adapted for the OSH requirements;
- to develop and/or validate hydrodynamic simulations and optimisations of the performance of the OSH platform;
- to develop a recovery tool and a carriage that are adapted to the ship;
- to develop or further develop and integrate tools dedicated to oil recovery for different viscosity of pollutants;
- to evaluate/validate experimentally the ability of the tools to recover the pollutants;
- to develop and/or validate scenarios of oil recovery with the OSH system;
- to assess the final integration of the OSH concept;
- to study the possibilities of having a decision-support and mission-planning tool for OSH;
- to evaluate the price of the OSH system and its maintenance costs;
- to establish a technical and commercial documentation dedicated to promoting the system on the market and presenting the system to the European Safety Agency.
The following work was carried out:
- an adjustment of the OSH capacities and features to the identified situations of pollution and taking into account operational lessons from past accidents;
- the definition of a preliminary ship design regarding hull line definition and general arrangements, including the main design options (platform, hull form, propulsion and manoeuvring, functional area arrangement, stability in rough weather and speed for the recovery operations);
- the design of oil recovery tools (brush type skimmer, oil separator), tool carriage and their integration on an OSH vessel;
- hydrodynamic calculations and tank tests aimed at optimising ship design in sea keeping (recovery operation) and powering (transit);
- experimental tests in oil recovery performance for the skimmer (with different viscosities of oil);
- the definition of an oil-spill mission and other complementary missions as the OSH is a multipurpose vessel;
- the development of a prototype of a mission-planning tool;
- the assessment of the economical potentials of the OSH;
- final project integration, including a parametric study, final technical definition, overall performance of the OSH system, virtual 3D prototype for demonstrations of the concept;
- the development of the OSH project documentation for promotional and exploitation purposes.
Funding
Results
In particular, the OSH project addressed the need for vessels specifically designed to recover oil pollution at sea. The intention was to have a ship that essentially forms a complete and self-containing system with the purpose of attacking an oil spill and has a number of positive features, including:
- high transit speed, in order to arrive quickly on the scene of the accident and operate oil recovery tools when the spill is still well concentrated;
- good sea-keeping performance at that speed, allowing minimal effect of weather conditions on the required transit time;
- good sea-keeping performance at very low (recovery) speed, enabling recovery operation in high sea states;
- good manoeuvrability at same speed, enhancing the functionality and recovery efficiency;
- a specialised and efficient oil recovery system that can tackle oil slicks of all types and viscosities at very high recovery rates and oil separating levels;
- a hull arrangement that facilitates the installation of the above system and its performance under adverse weather/sea conditions;
- high carrying capacity and autonomy, leading to increased efficiency in combating large oil spills; and
- a versatile multi-purpose configuration featuring specialised equipment, enabling the vessel to perform a number of varying missions and thus enhancing her potential in terms of both usability and commercial viability.
All these goals have been approached with a view to generating feasible and efficient solutions.
As an overall conclusion, it can be said that all the studies and final tests have clearly demonstrated that the OSH can sail in high sea states, and thanks to its excellent behaviour in sea keeping its tools can operate efficiently in harsh conditions to recover oil at sea, even the very viscous oils like the Erika one. It therefore represents a very comprehensive, efficient and feasible solution that is believed to be of great benefit and interest to the European Agency for Safety at Sea.
Technical Implications
The exploitation of the OSH while not involved in oil spill recovery operations, in order to improve her profitability, was investigated through a study of other possible missions, taking into account the compatibility of these missions with oil spill combating availability and operational constraints. The optimisation of the efficiency of the OSH while performing an oil recovery mission was of course tackled through the design of a prototype mission planning system, it was however important to expand the overall operational profile as it is conceivable that oil recovery missions may employ the vessel only for a small percentage of time. This led to the generation of a multi-purpose final version of the vessel, featuring forward superstructure with large deck areas carrying various equipment and tools as well as a helideck.
It appears from this study that several missions can be envisaged for the OSH, apart from her main oil recovery mission. The design of the ship allows her to perform, with no major design modification, tanker activities, supply and more general support missions. Besides, the time of operation of the ship can be shared between these different alternative missions. Furthermore, the open deck area makes possible to adapt a number of specific tools (winches, cranes, etc.) and turns the OSH into a very flexible platform. The best optimised use of the OSH, considering the OSH constraints and taking advantages of the ship specificities, appears to be a supply ship, with the ability to deal with emergency situations such as rescue and fire-fighting. The economical analysis determines the most profitable combination of these possible missions to make the OSH economically attractive during her non-pollution-related activities.
It has therefore been demonstrated that the OSH concept possesses a number of positive features making it a particularly attractive tool in the fight against the increasingly important problem of marine oil pollution. Its merits include: a high transit speed; good sea-keeping performance at that speed as well as at very low speeds; good manoeuvrability at very low speeds; high recovery rates combined with large carrying capacity and autonomy; ability to handle oil slicks of all types; and a multi-purpose configuration. These give the OSH significant advantages such as: quick arrival on the incident scene; extended scope of efficient oil recovery operations, both in terms of weather conditions or sea states and in terms of type and size of oil spills; and versatil
