Summary
- ClassNK issued a world-first General Design Approval (GDA) for a low-pressure liquefied CO₂ cargo tank concept that can omit PWHT using ECA.
- The work is a joint development by Mitsubishi Shipbuilding and Nippon Steel, using KF460 steel for the tank.
- The goal is to remove a major fabrication bottleneck: large PWHT furnace capacity is limited for big tanks.
Mitsubishi Shipbuilding and Nippon Steel say they have received the world’s first General Design Approval (GDA) from ClassNK for a low-pressure liquefied CO₂ (LCO₂) cargo tank design that uses Engineering Critical Assessment (ECA) to justify a manufacturing process without post-weld heat treatment (PWHT).
In the release, the companies point to a real shop-floor constraint: when high-strength carbon-manganese steel is used for large LCO₂ tanks, PWHT is generally required under the IGC Code, but furnaces big enough for these tanks are limited—slowing scale-up and stable supply. Their answer is an ECA-based integrity check, supported by material property assessment of a newly developed steel that conforms to ClassNK’s KF460 standard.
ClassNK adds that an Approval in Principle (AiP) for the ECA evaluation process was issued in September 2024, and the new GDA confirms the detailed design meets requirements even without PWHT, based on the ECA results under the specified design temperature conditions.
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