Mitsubishi Shipbuilding and Nippon Steel have received the world’s first General Design Approval (GDA) from ClassNK for a manufacturing process that enables large low-pressure liquified carbon dioxide (LCO2) cargo tanks to be built without post-weld heat treatment (PWHT). The approval follows joint development work that applied Nippon Steel’s newly developed high-strength, low-temperature-toughness steel to LCO2 tanks and validated PWHT exemption through an Engineering Critical Assessment (ECA).
PWHT is normally required when using carbon-manganese steels for large LCO2 tanks under the IGC Code, but limited heat-treatment furnace capacity has been a major barrier to scaling up tank size and stabilizing supply. The successful ECA demonstrated that weld integrity can be maintained without PWHT when using Nippon Steel’s KF460-grade steel, enabling a more economical and productive manufacturing process.
The breakthrough supports Mitsubishi Shipbuilding’s efforts to standardize large LCO2 carriers for future carbon-capture, utilization and storage (CCUS) value chains, and aligns with Nippon Steel’s Carbon Neutral Vision 2050 under its NSCarbolex Solution brand.
Both companies will now work with industry partners to commercialize the steel and tank technology, helping reduce LCO2 transport costs and accelerate deployment of CCUS infrastructure.
