Fatigue failure of a rotating chemical vessel

Abstract

This paper describes the fatigue failure of a welded steel vessel in a chemical plant. The process conditions required the vessel to be rotated continuously at a speed of about two revolutions per minute. To permit this rotation, a pair of trunnion shafts was welded to opposite sides of the vessel. Each shaft was supported in a self-aligning bearing. The connection between the shaft and the vessel was strengthened with gusset plates which were fixed to both vessel and shaft by fillet welds. Because of the self-weight of the vessel, each trunnion shaft was subjected to an upward reaction force of 13 tonnes applied at the centre-line of the bearing. After 4 1 2 years in service, 75% of the gusset-shaft welds had failed by fatigue. The failure was analysed using the weld fatigue curves given in BS 5400: Part 10: 1980 and remedial measures were discussed.