Risk Analysis Based on ETA, FTA and Bowtie Methodologies for the Bulk Coal Discharge Process

Abstract

A safety analysis was performed to determine possible causes of coal falling in the bulk coal discharge process using a methodology for risk analysis based on a combination of Fault tree analysis (FTA), event tree analysis (ETA) and BowTie (BT). The steps for risk assessment were the following: Description bulk coal discharge process, Event sequence modeling where logic models (ETA; FTA; BT) and Consequence assessment. The bulk coal discharge process is performed using cranes which are deployed in the terminal, in parallel to the coal holds of the ship. The hydraulic grabs descend onto the ship holds at an angle, determined by considerations of wind direction and intensity, which shovel up the coal and lift it upwards. The grabs move along the crane handle, and open up above the funnel which pours the coal into the coal conveyor, this procedure is repeated sequentially until empty the ship. Results from BT allow to identify three possible causes of coal falling. Two of which are attributed to technical factors such as crane failure and grab failure, while the other cause is related to human factors such as lack operational discipline (OD). Three barriers were identified to prevent the fall of coal: certified crane, hermetic grabs and operational discipline. Two mitigating barriers were identified: Vacuum truck to clean the coal in the pier and tablecloth to avoid coal fall in the sea. Finally, the consequences if not working barriers are: coal built up on pier and sea pollution. However, it can't be ensured that the stranding of coal on the beaches is directly caused by port operations.