Application
Of the nearly two hundred LNG tankers plying the seas today, less than half are of the familiar spherical design seen in most publicity photos, with what appears to be several huge “balls” protruding from the deck of the ship. This is the traditional spherical Moss design, that is expensive and carries high Suez Canal tonnage, but largely eliminates the problem of “sloshing” in heavy seas.

Membrane based carriers are more traditionally shaped with square containers and flat-topped vessels. They are cheaper than Moss spherical ships and smaller, meaning less Suez Canal tonnage. Sloshing, however, is an issue, and a great deal of research has been done to utilize membranes to eliminate that problem. Lios participated in the testing of these membranes.

A Lios OTS 2^nd generation system was tested as a leak detection system for membrane based LNG-Carriers. A special sensor cable which is able to withstand temperatures down to -190°C was installed in a zig-zag pattern to provide effective coverage of the inside of the membrane of a large mock-up tank. One side was filled with liquid nitrogen to simulate LNG, and was allowed to achieve steady state conditions over a couple of hours.

Material+Concept

• OTS40P, 1 channel.
• 60 m low temperature sensor cable.
• 85 m supply cable.
• Visualisation and data logging with Charon_02 software.

Commissioning
Test run: July, 2005

Miscellaneous
Two clear cold spots caused by small leaks caused by insufficient preparation and adhesion of the material of the membrane compounds were identified and located inside the mock-up. The conclusion reached was that OTS technology performed perfectly, and is well suited as a reliable leak detection and locating system on membrane LNG carriers.