Lloyd's Register and Gaz Transport & Technigaz (GTT) have jointly commissioned MARINTEK to carry out a series of model tests to investigate the effects of sloshing in partially filled prismatic LNG tanks. A typical four-tank ship design with a capacity of 140,500 cu m has been used for the purposes of the study.
For the moment, the results show that:
for the filling levels below 10% of tank length and over 70% of tank height the tests showed good results
based on the test results, it is possible to increase the currently accepted authorised filling range and to decrease the upper limit to 70% of tank height. This new limitation allows any amount of cargo to be carried in a 140,500 cu m LNG carrier by suitable distribution between cargo tanks.
The recent work carried out at MARINTEK involved the use of a 1:60 scale model to determine the pressure loads from sloshing-induced impacts. The model testing is built on the previous work commissioned by Lloyd’s Register
at MARINTEK to identify the potentially critical load cases for a typical 140,500 cu m LNG carrier and modeled on the behaviour of a No. 2 tank, which is considered to be the tank generally most exposed to potential sloshing damage on an LNG carrier. The tank was tested for a full range of filling levels.
Lloyd’s Register and GTT have reached an agreement to carry out additional testing to confirm the loads that were predicted during this recent series of experiments for filling heights below 70% of the tank height. When these tests are completed, Lloyd’s Register and GTT will issue a further joint statement.