While LNG is expected to be widely used this decade, alternative fuels are under scrutiny and shipowners are becoming increasingly focused on multi-fuel supply systems able to handle two or more different fuels. This prompted Italy based liquefied gas handling system specialist Gas and Heat S.p.A. to embark on a study to identify possible options and to develop solutions. It has now gained an Approval in Principle from classification society Bureau Veritas (BV) for its flexible solution for the transport of LNG and ammonia.
In a study supported by BV, GH demonstrated that IMO Type C cargo/fuel tanks made with a special grade austenitic steel can transport both LNG and ammonia for sea-going and inland navigation.
GH has used austenitic steel with a special grade for LNG containment since its Approval by Bureau Veritas in Jun, as an “alternative material” in terms of the IGC/IGF Code. The compatibility of this material with ammonia has been verified by a specific stress corrosion cracking test performed by GH and then approved by Bureau Veritas in August 2022.
Twelve specimens were prepared for the tests in accordance with ISO 16540, which provides guidelines on evaluating the corrosion of metals and alloys by determining their resistance to stress corrosion cracking using the four-point bend method. This methodology includes procedures for metals that have no distinct yield point in their stress-strain behavior as well as metals with a distinct yield point.
Throughout the test, the specimens were loaded as four-point-bend (FPB) test subjects to the specified minimum yield strength of the base material. Tests were then performed in three different conditions: at ambient temperature, -20C, and -33C, in an environment of pure ammonia. After the completion of all tests, each specimen was visually examined at 10x magnification by a stereoscopic microscope and subjected to fluorescent liquid penetrant examination to detect any visible surface crack. An additional tomographic scan was performed to ascertain that no inner crack was detected.
According to Bureau Veritas, the outcomes successfully demonstrated that cargo/fuel tanks made of austenitic steel can carry both LNG and ammonia, for seagoing and inland navigation.
BV was involved from the very earliest stages, validating the stress test methodology and reviewing each phase of the test. The society confirmed that the applied methodology opens the way to design and build LNG/Ammonia tanks that comply with the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC Code) and the international code of safety for ship using gases or other low-flashpoint fuels (IGF Code), as well as applicable BV’s classification rules for seagoing and inland navigation.
Paillette Palaiologou, vice president South East Europe, Black Sea & Adriatic Zone at Bureau Veritas Marine & Offshore, said: “While the shipping industry is facing many uncertainties, it is the role of class to support the industry in this period of change. I am proud of the work accomplished by both teams and the results are extremely positive for the industry. Providing different options will be key for industry stakeholders as they make decisions. We look forward to collaborating with GH on new projects.”
Mauro Evangelisti, President of Gas and Heat SpA, said: “Innovation has always been and will remain our main focus. This study is part of the innovation journey the industry needs for a smart and sustainable transition to a greener future. We hope the use of this material will provide more cost-effective and safer components to the industry.”
GH has already secured one contract that includes the supply of cargo tanks for inland navigation of LNG/ammonia and another for a seagoing LNG/ammonia fuel supply system.