Definition: LNG ships
Liquid natural gas (methane) is carried at temperatures of around –160° C and as such presents very significant technical difficulties in the design of the cargo containment system. The ships are large and the potential hazard represented by the cargo (an explosion of one of these ships would represent a blast of several mega-tonnes) dictates that the standards of construction are higher than any other class of ship. Construction is restricted to a small number of licensed builders and entry costs into this sector are very high. Two containment systems have been developed. The original system uses spherical tanks and is based on a design by Moss Rosenberg. These ships are often called "Moss type" or "spherical type". The alternative system uses more conventionally shaped tanks based on designs by Gaz Transport or Technigaz, normally referred to as "membrane type".
First Marine International Limited, "Overview of the international commercial shipbuilding industry, Background report", disseminated on the Web site of Directorate-General "Enterprise and Industry" of the European Commission, May 2003