What is definition of Membrane Tanks ?

• Membrane tanks are non-self-supporting tanks which consist of a thin layer (membrane) supported through insulation by the adjacent hull structure.
• The membrane is designed in such a way that thermal and other expansion or contraction is compensated for without undue stressing of the membrane.
• The design vapour pressure P0 is not normally to exceed 0,25 bar. If, however, the hull scantlings are increased accordingly, and consideration is given, where appropriate, to the strength of the supporting insulation, P0 may be increased to a higher value but less than 0,7 bar.
• The definition of membrane tanks does not exclude designs such as those in which non-metallic membranes are used or in which membranes are included or incorporated in the insulation. Such designs require, however, special consideration by the Society.
• In any case the thickness of the membranes should normally not exceed 10 mm.

Note :

• Integral tanks form a structural part of the ship’s hull and are influenced in the same manner and by the same loads which stress the adjacent hull structure.
• The “design vapour pressure” P0 as defined is not normally to exceed 0,25 bar. If, however, the hull scantlings are increased accordingly, P0 may be increased to a higher value but less than 0,7 bar.
• Integral tanks may be used for products provided the boiling point of the cargo is not below – 10 °C. A lower temperature may be accepted by the Society subject to special consideration.