A derailment that spilled about 89 litres of phosphoric acid has shown the critical importance of detecting track defects before they cause an accident.
The derailment occurred on 9 April 2013, near Lowdina in Tasmania. The train, which consisted of five locomotives hauling 28 wagons, was being operated by a single driver. It had departed Burnie that morning, bound for Boyer in Southern Tasmania.
A few kilometres away from Lowdina, the track made a tight curve to the left, and as the third wagon travelled over the curve, it came into contact with a twist defect in the rails. The leading wheels of the wagon were jolted off the rails, and the rear wheels derailed a few metres later.
The train continued on, however, with the driver unaware of the derailment of the third wagon. At Lowdina, the derailed wagon struck a set of points, and the impact completely derailed the third wagon, dragging the fourth and fifth wagons off the tracks. The wagons separated and spilled their containers around the adjacent area. The third wagon was carrying two containers of sodium hydrosulphite while the fourth wagon held a tank of phosphoric acid solution.
The separation caused the train’s brakes to apply automatically, and it stopped about 90 m later. The driver notified the train control centre and TasRail employees were dispatched to the site. Phosphoric acid was discovered leaking from the top hatch of the tank and a number of spill kits were deployed to contain the leak.
Early detection and conscientious management of track defects is critical in maintaining safe rail operations.
It was estimated that about 89 litres of phosphoric acid escaped from the tank, most of which was contained on site. Eventually, the site was declared safe and investigation/recovery operations began. Approximately 800 steel sleepers were replaced along with about 24 m of rail and associated fasteners and switch gear.
The ATSB investigation identified the large twist defect as the cause of the initial derailment, and found it likely that a previously undetected, small to medium sized twist defect had developed under the passage of the train.
Prior to this incident, the network owner/manager (TasRail) had identified the need to renew the track infrastructure in the area of the derailment and anticipates that the track between Colebrook and Campania should be renewed by June 2014.
The ATSB emphasises to all rail operators that early detection and conscientious management of track defects is critical in maintaining safe rail operations.
Read the report: Derailment of train 331, near Lowdina, Tasmania, on 9 April 2013