2019 Spring Meeting and 15th Global Congress on Process Safety

(109b) CFD-Based Probabilistic Explosion Hazard Analysis As an Early Tool to Improve FLNG Design

Authors

Davis, S. - Presenter, GexCon US Inc.
Marsegan, C., Gexcon US
Process areas on floating LNG facilities (FLNGs) are typically designed to be very compact, due to the high costs of “floating real estate”. Given the high congestion levels of FLNGs, explosion design accidental loads (DALs) can become very large and are very sensitive to the layout of piping and equipment, the size of safety gaps, specifics of the liquefaction process, etc. For these reasons, the analysis of explosion hazards on FLNGs is a critical step that should accompany the facility development from the very earliest design phase. This paper will discuss how a probabilistic explosion hazard analysis methodology based on computational fluid dynamics (CFD) modeling can be used to optimize the layout of an FLNG facility with respect to DALs. The methodology uses a detailed 3D model of the FLNG geometry (down to 1-2 inch pipe diameters) within which gas dispersion and vapor cloud explosion scenarios are simulated using a CFD tool; leak rate probability data and time-dependent ignition model are then used to calculate probability of exceedance curves and to determine the DALs. The paper will present results from studies which compared the effectiveness of a number of design variables, such as:
  • Different liquefaction processes;
  • Docking distance between FLNG and LNG carrier;
  • Module layout.

The paper will demonstrate how CFD-based probabilistic methodologies can provide FLNG designers with critical safety-related design implications previously not available until the later stages of design. More specifically, the advanced methodology implemented in the present work, which incorporates advanced techniques to supplement an “incomplete” model of the FLNG geometry in concept or design phases before front-end engineering design (FEED) to levels anticipated in the “as-built” condition, provides a powerful tool to assess FLNG layouts/technologies in the earliest design phase. This paper will provide some case studies on how valuable insights were gained by applying a detailed 3D model in early, concept phase of the design.