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New generation natural gas ship interfaces (NG²SHIPI/F)

Periodic Report Summary - NG2SHIPI/F (New Generation Natural Gas Ship Interfaces)

The goal of the NG2 SHIP I/F project has been to improve the effectiveness of Liquified natural gas (LNG) transportation from exporting countries to receiving ones. Many interfaces are used throughout the LNG voyage, such as:
- loading arms to load - unload the liquid gas;
- on-board pipes to transfer LNG from tanks to shore;
- specific submerged pumps and electrical system to operate it;
- high insulated tanks of LNG carriers.

The project purpose is to improve this LNG transfer chain through the following studies:
- improve LNG cargo pumps, by an increase of their unloading capacity, and the use of variable speed to optimise the system;
- improve piping thermal performance by using new foam formulation, insulating the whole transfer lines, which is not state of the art (on-board lines as well as loading arms insulation to be studied);
- reduce the cost of the on-board cargo piping system, thanks to the use of pre-insulated pipes including other pipes and services, and using new pipe support technology;
- reduce the excess boil-off gas naturally produced during ship voyage thanks to the use of argon in replacement of nitrogen for the insulation of insulation volumes;
- creation of a new power interface which goal is to use diesel electric propulsion systems when the ship is at anchor in order to provide the shore with this electricity, either to sell it or to use it for the LNG transfer process.

The cargo pump scale prototype has been designed, mounted, shipped to the United States for its first series of tests, whose goal is to assess its hydraulic performances. After this successful first campaign, the second phase consisted in the specific tests of the new electrical motor designed by Wroclaw University of Technology and made by Mikroma, which took place end of March 2006. The tests were successful and showed perfect correlation compared to simulations made at design stage. Pump and motor expertise after test confirmed the good pump and motor behaviour.

The design of a powerful variable speed system for this type of pump has been deeply studied thanks to the use of dedicated models. Conclusion is that it is possible to integrate pump variable speed systems on-board LNG carriers at low cost, using propulsion VFD systems, taking into account the different networks and unloading scenarios.

Argon filled foam insulation tests have been carried out, but did not show expected results. The study has been moved on tests and studies with argon filled perlite insulation system, whose results are positive, as they present a 10 % reduction in thermal conductivity when using argon. Simulations carried out by Sintef for the different insulating boxes match well the tests results and confirm the influence of the plywood thermal coefficient. Finally, the argon supply system preliminary study has been performed, starting with a trade-off between various solutions. A closed argon supply system (ASU) based on liquefied argon storage and argon / CH4, argon / nitrogen cryogenic separation has been selected on the basis of economical and environmental considerations. This solution is easily applicable for new or existing LNG carriers.

Loading arms insulation studies have shown interesting gains by using double wall and vacuum insulated pipes, solution that has been manufactured and tested with positive results.

Use of pre-insulated valves was studied, but it was soon realised that this technical solution could not be finalised with a commercially satisfying result and the work was discontinued.

Instead all efforts were used to finish the two remaining tasks:
- a new and more flexible PUR foam formulation;
- new lighter and more cost effective pipe support design.

The power interface study has been completed, leading to a high potential gain by using power interface either by selling electricity to the grid when the ship is processing, or by using the grid as power source in case of maintenance of the ship engines, or for environmental issues.

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