Safety and Reliability Studies Using Analysis Tools

Computational Fluid Dynamics and Computational Structural Mechanics (also called Finite Element Analysis of FEA) and a combination of the two — Fluid Solid Interaction (FSI) — have long been used for safety of Personnel in Industry. This paper gives four examples of using these tools for designing equipment and mitigations to provide a safe and amenable working environment for personnel. The first example deals with the use of CFD to resize or relocate exhaust stacks — to prevent personnel working on an adjacent elevated platform being exposed to hot gasses or low oxygen levels — under high wind conditions or the presence of an inversion layer in the atmosphere. The second example is on construction of a retractable protective screen — for personal working on an elevated platform — in the event of a leak of combustive gas from an adjoining unit. CFD is used to determine the length and temperature of the flame while FEA is used to determine the impinging forces half way between the combustion source and the workers to select a suitable flexible retractable screen for protection. A third example is on cooling methane and ethane vapors heated during initial ship loading to prevent flaring caused by pressure build up. Flaring causes several environmental issues such as degradation of vegetation and trees, temperature effects on nearby occupied building, large luminescence, atmospheric disturbances and turbulence on passing aircraft, as well as loss of production. The stresses on the piping network, flanges, valves, pads and shoes — which may lift by Joule-Thompson effect caused temperature differentials — are studied using FEA to ensure the safe operation. A final example is on the use of CFD and FEA to determine the sources of flow-induced and cavitation-induced acoustic noise and vibration and water hammer produced by flow restrictions and flashing of liquid to vapor behind a vee-ball control valve and a ball control valve. The frequencies are extracted from CFD and checked against the natural frequencies from modal analysis and experimental bump test for typical resonant frequencies in the system. Mitigations are proposed to ensure lower noise levels and reduce vibrations in the system for the comfort of personnel working in the vicinity.