Tank insulation system for LNG and ammonia-fueled vessels receives ClassNK’s blessing

December 3, 2025, by Melisa Cavcic

With the maritime industry facing the pressing challenge of decarbonization, the development of alternative fuel vessels powered by liquefied natural gas (LNG) and ammonia is gaining momentum, as illustrated by an approval in principle (AiP) Japan’s classification society ClassNK has granted for Spray form insulation system of IMO Type B tank for LNG and ammonia fuel.

While IMO Type C tanks have been the mainstream choice for LNG-fueled ships due to their advantages in productivity and cost, IMO Type B tanks are gaining recognition as an alternative, offering superior cargo efficiency and outfitting flexibility for large-capacity fuel tanks required on large container ships and ammonia-fueled vessels.

For the design concept and result of the demonstration mock-up test for the Spray form insulation system of IMO Type B tank for LNG and ammonia fuel developed by Nihon Shipyard and Hankuk Carbon, ClassNK conducted its safety review based on part N of its ‘Rules and Guidance for the Survey and Construction of Steel Ships,’ which incorporates the IGC Code, and also part GF, which entails the IGF Code.

Upon confirming its compliance with the requirements, the Japanese classification society issued the AiP. The certification is said to demonstrate its feasibility from regulatory and safety perspectives.

According to ClassNK, the design is examined based on the existing regulations, such as international conventions and ship classification rules, and an AiP is issued as proof of conformity with requirements at the initial stage of designing or before the specific target ship to be implemented is decided.

This is perceived to prevent rework of regulatory aspects in the post-process, shortens the examination time at the time of class registration, and can be used as a technical basis for external appeal of the design status.

The Japanese classification society, which intends to continually strive to contribute to advanced decarbonization initiatives through safety assessments and other ways, recently gave approval in principle for a tank design concept incorporating Sandwich Plate System (SPS) technology to boost shipboard storage capacity for both methanol and ethanol.