The Cushioning Effect of the Technigaz Membrane(eBook)

Published Date

January 1993

The Cushioning Effect of the Technigaz Membrane(eBook)

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This paper describes the tests performed to check the feature of the Technigaz membrane that appears to reduce the sloshing pressure in an LNG carrier's tanks. (18pp)

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Three types of LNG marine containment system exist today, spherical self supporting tank, prismatic self supporting tank and membrane tank. Very quickly this capacity has increased to reach what can now be considered as a standard value: 125,000 or 130,000 cu.m. The first vessel with a cargo volume in this range was delivered in 1974. Apart from the increase of capacity, the other evolution concerned the number of cargo tanks. If the first vessels, 125,000 m3 class, have 6 cargo tanks, this figure has been reduced to 5 and now to 4. This means that the engineering companies developing the containment systems have always tried to get know-how on liquid motions in the tanks as good as possible. It should be remembered that, considering a standard LNG carrier, 135,000 cu.m capacity, with 4 tanks and based on a membrane system, the length of the largest tank is in the vicinity of 45 m. To avoid the critical phenomena of liquid motion ("sloshing") it is known that several criteria have to be met.

None of the Technigaz ships has had any problem with sloshing. However the design criteria may be insufficient to explain this. The Technigaz membrane offers a particular feature: the orthogonal corrugation network. If these corrugations cannot have any influence on the global liquid motion (due to the size of these corrugations compared to the size of the tank, they cannot reduce liquid speed), they may have a beneficial effect on local phenomena, when the wave comes in contact with the tank wall. Here may take place what has been called "the cushioning effect". This paper describes at first how such a phenomena may occur. Then it describes the tests that have been performed in laboratories to check this particular feature of Technigaz membrane and introduces a theoretical model that allows compututation of potential reduction of sloshing pressure in LNG carrier tanks.

Paper Delivered by:
J Claude (Technigaz, France)

Prepared for:
Gastech Paris 1993

For over 45 years, the Gastech Exhibition & Conference has been at the forefront of the international gas and LNG market. This world-renowned event is regarded as the most significant meeting place for gas and LNG professionals, where the global industry gathers to do business.

Gastech hosts major IOCs, NOC’s, global utility companies, EPC contractors, shipbuilders, pipeline companies, manufacturers, distributors, technology and service providers, all who play an active role in the global energy value chain.

Title: The Cushioning Effect of the Technigaz Membrane(eBook)
Product Code: 4433g016
Published Date: January 1993

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