Liquefied natural gas (LNG) is the cleanest fossil fuel available, producing less carbon emissions and fewer pollutants than other fossil fuels. Marine transportation is a key process in the LNG supply chain. The use of tank containers, which are portable equipment, can effectively facilitate multi-mode transportation. LNG evaporation causes pressurization, which is a safety concern during transportation. Ship motion and environmental temperature are the main factors affecting pressure variations. In this study, the effect of ship motion on pressurization and holding time was investigated through three types of experiments, namely, prototype, field, and self-pressurization experiments. The results showed that while increased boil-off gas was generated due to ship motion, this evaporation remained stable in dynamic cases. Higher evaporation rates were obtained under more severe dynamic conditions, and the holding time was shortened. The two different effects of ship motion on pressure development discussed here are the facilitation of pressurization due to the enhancement of heat transfer and the prevention of pressurization due to gas condensation at the vapor–liquid interface. These two effects show varied levels of predominance over the pressure variations depending on different stages of transportation. The holding time in the experiments was able to reach 87 days under the most severe condition, which is long enough for long-term shipping; the safety of transporting LNG in tank containers is further discussed based on the experimental results herein.

Prototype fatigue tests simulate in-place working conditions of dynamic umbilicals that are usually conducted to verify fatigue life. The fatigue failure hot spot locates on the top segment of the umbilical. The umbilical reaches a maximum curvature at the hot spot. The hot spot position of the umbilical is always inside or near the bend stiffener. The radial gap between the umbilical and the bend stiffener is very small, making it difficult to put traditional sensors in the gap. In this work, a prototype umbilical tension-bending test is conducted, and the optic frequency domain reflectometer (OFDR) technology is utilized to measure the distributed strain of the umbilical inside the bend stiffener. The curvature of the umbilical is obtained to locate the fatigue hot spot in order to verify the feasibility of this approach. The test results show that the umbilical curvature can be measured well with the use of OFDR technology. The influence of tension and swing angle on the position of the maximum curvature is studied. The method proposed in this article provides a valuable approach for curvature monitoring in the application of dynamic umbilical fatigue tests.