Strength and structural integrity assessment of fillet weld attachment junction on cylindrical pressure vessels

Abstract

Welding is a method of joining components in manufacturing piping and pressure vessels. This method is used to joint cylindrical vessel and head, vessel and nozzle, and pad attachment for lifting lug. This paper aims to present results of finite element study of strength and structural integrity of fillet weld used for pad attachment of lifting lug to lift a horizontal cylindrical vessel. It is aware that the pad attachment and the cylindrical vessel are not integrally jointed. The joint of pad attachment and the cylinder is only along the peripheral of the rectangular pad. Therefore, there is inherent crack introduced in this structural connection, the crack length equals to the axial and circumferential length of the pad. Study of the effect of crack length on limit load has been performed separately in 2D for circumferential and axial direction. The crack length parameter was 200, 210, 220, 230, 240 and 250 mm. The results surprisingly show that crack length does not increase or decrease the limit load. It seems that strength of material approach does not work for dealing with cracked structures. Linear Elastic Fracture Mechanics (LEFM) analysis then was performed to study the effect of axial crack length on stress intensity factors of KI and KII. Results show that both KI and KII increased as the crack length increase.