Floating Liquefied Natural Gas (FLNG) units have been under development for decades. They are now becoming a reality, combining the design and installation of LNG units with a traditional " FPSO". Since FLNG facilities handle large flammable gas quantities in a relatively small and congested environment compared to onshore LNG plants, the explosion risk is expected to be higher than some other offshore floating facilities. As a consequence the intensity of the resulting blast loads on the unit can be more severe even if the explosion likelihood is considered low in the design through a frequency analysis.
Even if prevention and mitigation measures are implemented to reduce the risk to ALARP (As Low As Reasonably Practicable), Safety Critical Elements (SCE), such as main equipment and structures, shall be designed to withstand the blast event. Since the explosion events are very specific (high intensity and short duration), the common design rules and tools should be updated to take into account this accidental event. In addition, the associated performance criteria for SCEs should be also modified. Finally the entire design shall comply with safety objectives (personnel protection, prevention of escalation).
This paper focuses on the philosophy of design against a blast event. It will review the critical functions of the unit that must be maintained during emergency evacuation in order to protect people and, identify the key parameters governing the explosion strength on FLNG. It will show that the derivation of effective explosion loads on structures and equipment based on computational fluid dynamics simulations is not straightforward and requires expertise both in explosion modeling and explosion response. In a second part the paper will show how all the engineering disciplines in Technip individually apply these blast loads into their design through non-linear finite element analyses. Finally, it will highlight the interface between the engineering disciplines and how a consistent demonstration through the design can be achieved in order to fulfill the safety goals, taking engineering further.
