Summary
Floating-liquefied-natural-gas (FLNG) units have been under development for decades. They are now becoming a reality, combining the design and installation of liquefied-natural-gas (LNG) units with a traditional floating production, storage, and offloading facility. Because FLNG facilities handle large flammable-gas quantities in a relatively small and congested environment compared with onshore LNG plants, the explosion risk is expected to be higher than that for 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 likelihood of explosion in the design is considered to be low through frequency analysis.
Even if prevention and mitigation measures are implemented to reduce risk to as low as reasonably practicable, safety-critical elements (SCEs) such as main equipment and structures should be designed to withstand the blast event. Because 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 modified. Finally, the entire design should comply with safety objectives (personnel protection, prevention of escalation).
This paper focuses on the philosophy of design against a blast event on floating facilities in general, but with a particular focus on FLNG units. It will review the critical functions of the unit that must be maintained during emergency evacuation to protect people and identify the key parameters governing the explosion strength on floating facilities. It will show that the derivation of effective explosion loads on structures and equipment on the basis of computational-fluid-dynamics simulations is not straightforward and requires expertise in explosion modeling and explosion response. The paper will also show how all the engineering disciplines in Technip individually apply these blast loads in their designs through nonlinear-finite-element analysis. Finally, the paper will highlight the interface between the engineering disciplines and how a consistent demonstration through the design can be achieved to fulfill the safety goals, taking engineering further.