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LNG Carrier - Model Tests in Ice - LNG Review 2005
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HSVA
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Originally printed in:
LNG Review
- 2005
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Approximately one-third of the world's known and not yet exploited reserves of natural gas are in Russia. The overwhelming majority of these reserves are in Artic and Sub-Arctic areas.
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Approximately one-third of the world’s known and not yet exploited reserves of natural gas are in Russia. The overwhelming majority of these reserves are in Artic and Sub-Arctic areas. Not only in Russia, also in other areas like Canada, natural gas reserves are found in harsh and ice covered environments. As a consequence, LNG ship technology is heading towards Arctic LNG carriers. New developments in ice navigation, winterisation and tanker sizes are generating a new exciting challenges for shipping and ship building industries worldwide.
The existing ice class regulations should only be considered as a first guide for designing such vessels. In the future, performance of new developed vessels needs to be investigated in much more detail, therefore ice model tests are imperative.
At the Hamburg Ship Model Basin (HSVA) LNG carriers are investigated and developed, not only for their use in ice, but also demands and requirements for open water performance are considered. With more than 90 years of experience and expertise of developing open water vessels and more than 50 years of experience and expertise in ice engineering, HSVA started 20 years ago to look closer into the hull shape design and power and navigation requirements of LNG carriers. Furthermore, HSVA is involved in the main recent European ice related research projects like Arctic Operational Platform (ARCOP), SAFEICE and STANDICE.
It is common practice to guide ships in ice-covered waters by using an icebreaker. The vessel is led through the ice by the icebreaker, with the icebreaker breaking the ice and the vessel following in the broken channel. This traditional way of guiding vessels in ice fails when the beam of the vessel (LNG carrier) is larger than the beam of the icebreaker, which is in the range of about 20–30m. In the case that the LNG carrier’s beam is larger than that of the icebreaker, the broken channel is not wide enough and the vessel would have to widen the channel by breaking ice with its forward shoulders. This will increase the resistance dramatically. In this cases a possible way to guide such vessels would be the use of two icebreakers, with the first one breaking the channel and the second widening it. The vessel follows in a channel approximately 1.25 to two times the widths of its beam. In this ice channel, both smaller and larger ice floes contribute to the ice resistance of the following vessel. In order to investigate the speed, resistance and power in different ice thicknesses a comprehensive ice modeltesting programme should be carried out.
For the model tests, a parental level ice sheet of target ice thickness will be prepared according to HSVA’s standard model ice preparation procedure. After a predefined level ice thickness has been reached, the air temperature in the ice tank will be raised in order to adjust the flexural strength of the model to the required value. In order to obtain a defined friction coefficient between the ice and the model hull, HSVA applies a special paint composition to the models of ice-going vessels. In order to achieve a most realistic wide ice channel the channel will be broken with the help of two HSVA stock icebreakers towed through the level ice as it is shown in Figure 1.
Figure 1: Generation of a Wide Ice Channel with Two Icebreakers
Categories:
Transportation
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LNG
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