Full-scale sloshing tests underway at MARIN
MARIN is carrying out full-scale sloshing tests for the validation of sloshing assessment tools on behalf of the Sloshel project group. Report unveils the until-now, confidential work of Sloshel.
Mirek Kaminski
m.kaminski@marin.nl
Conventional sloshing assessments of new membrane LNG carriers traditionally follow the comparative approach that is based on small-scale model testing, numerical simu- lations and the excellent track record of LNG carriers. Model testing provides the maxi- mum loads, based on statistical analysis of measured pressures. The response of the containment system to these loads is numerically simulated and checked against different limit states.
However, with the filling level limitation on the current fleet, experience is lacking to support comparative methods for partially filled cargo tanks. To move forward, the industry is developing a methodology to assess membrane systems by a direct comparison of the loads and the structural capacity. To develop such methodology, MARIN recognised the need for full-scale validation already back in 2003.
Gradually, a confidential and exclusive Joint Industry Project “Sloshel” was set up by MARIN, Gaztransport & Technigaz (GTT), Bureau Veritas and Shell. Ecole Centrale Marseille, the American Bureau of Shipping, Chevron, Lloyd’s Register, Det Norske Veritas and ClassNK joined the project later on.
Sloshel results to be revealed at ISOPE Following a recent decision of the project group to reveal some of the findings, a dedicated session on the Sloshel project will be held during the first LNG Sloshing Dynamics Symposia at the ISOPE conference in Osaka, Japan, from June 22 to 26, 2009.
The scope of work includes full and small- scale tests conducted at MARIN, numerical developments carried out by Bureau Veritas and validation studies undertaken by the consortium members.
On behalf of the project group, MARIN has now carried out 110 full-scale sloshing tests in the Delta flume of Deltares. Each sloshing test consisted of one breaking wave impact, obtained by the controllable wave focusing method. The wave breaking impacts were first defined in 1:6 tests that showed that they are representative for sloshing impacts in membrane LNG tanks.
The full-scale data includes shape measure- ments of the breaking wave before and during the impact, as well as pressure, force, strain and acceleration measurements of a real containment system and its rigid equivalent.
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