Fitness for service assessment of liquid storage tanks

Abstract

Storage tanks are widely used in industrial applications in order to store liquid products. Corrosion damage, which is generally termed as locally thinned area (LTA), is considered to be a serious threat to the structural integrity of the industrial storage tanks. Therefore, fitness-for-service (FFS) assessment of these structures needs to be performed periodically in order to ensure the operational safety and structural integrity. -- In the present work, the Remaining Strength Factor (RSF) is chosen to quantify corrosion damage. Two alternative methods are proposed for FFS assessment of industrial storage tanks undergoing corrosion damage. The methods are based on the variational concepts in plasticity, the m-alpha tangent multiplier, the concept of elastic decay lengths and the idea of reference volume. The proposed methods are shown to give conservative assessment of the remaining strength of storage tanks developing LTA during operation. The methods are demonstrated through an example, and the results are verified by inelastic finite element analysis.