An FLNG (floating liquefied natural gas) or LNG FPSO (floating production, storage and offloading) unit is a notable offshore unit
with the increasing demand for LNG. The liquefaction process on an FLNG unit is the most important process because it detennines the economic
feasibility, but would be a hazard source because of the large quantity of hydrocarbons. While a high efficiency process such as OMR has been preferred
for onshore liquefaction processes, a relatively simple process such as the SMR (single mixed refrigerant) or DMR (dual mixed refrigerant) liquefaction
process has been selected for offshore units because they require a more compact size, lighter weight, and higher safety due to their space limitation
for facilities and long distance from shore. It is known that an SMR has the advantages of a simple configuration, small footprint, and lower risk.
However, with an increased production rate, the inherent safety of SMR needs to be evaluated because of its small train capacity. In this study, the
potential explosion risks of the SMR and DMR liquefaction processes were evaluated at the conceptual design stage. The results showed that an SMR
has a lower overpressure than a DMR at the same frequency, only with a small production capacity of 0.9 MTPA. "With increased capacity, the
overpressure of the SMR was higher than that of the DMR. The increased number of trains increased the frequency in spite of the small amount
of equipment per train. This showed that the inherent risk of an SMR is not always lower than that of a DMR, and an additional risk management
strategy is recommended when an SMR is selected as the concept for an FLNG liquefaction process compared to the DMR liquefaction process.