Fatigue analysis of girth gear of a rotary dryer

• This paper describes the fatigue failure of a girth gear of rotary dryer in a chemical plant.
• Stress analysis were carried out using the EN 1993-6:2007 and BS 5400-10:1980 Codes.
• Fatigue-induced cracks were related to the stress risings encountered at the start-up condition of the rotary dryer.

This paper describes the fatigue failure of girth gear manufactured from low alloy cast steel of rotary dryer in a chemical plant. The cracks of T-section web of the girth gear occurred at the end of 25 year working period because of stress intensity factor. Because of normal condition of working surfaces of teeth, spare gear was not thought and repair welding was the only option. Nickel based super alloy electrode was used for repairing and it had been successful until the new gear was ordered. The factors behind the fatigue failure and the reasons of temporary repairment were discussed using the cause-effect diagram. Higher grade bolt using instead of design grade, insufficient stiffener of web, insufficient preparation of repair welding and wide section welding beads at the welding deposits were found as the reasons of changing the girth gear with the new one.