EVALUATION OF MEMBRANE FAILURE MODES FOR CRYOGENIC LNG STORAGE TANKS

摘要

This paper examines in detail the potential failure modes for the membrane tanks (in particular, the inner membrane) and identify the most significant ones for further quantitative analysis. In addition, an approach is proposed for the evaluation of the likelihood of the most dominant membrane failure modes identified. The failure modes evaluated in this paper includes defects induced by welding (e.g., hot cracking), fatigue crack propagation, stress corrosion cracking and other forms of corrosion, fatigue damage, and fracture. Complex design features such as the corrugations in the LNG panels and the lap welds led to high stress concentration in a number of areas in the inner tank membrane which in turn are prone to fatigue damage. In addition, the lap welds can have inferior weld quality than other types of welds. The most critical failure mode for the LNG tank membrane is identified to be the fatigue failure of the stainless steel membrane, which is dominated by strainbased fatigue at corrugation crosses and at the corrugation welds.