The Australia Transport Safety Bureau (ATSB) has released its report on the serious injury that occurred on board the LNG carrier Northwest Stormpetrel.
On November 6, 2014, the Northwest Stormpetrel completed loading cargo and left its berth in Dampier, Western Australia. The ship was then anchored in the harbor to allow the use of excess time in the schedule for its voyage to Japan for in-water lifeboat drills and other maintenance tasks. One of the tasks planned was to check the LNG forcing vaporizer’s steam trap to resolve recurrent drainage issues with the system.
At about 0900 on 9 November, the integrated rating assigned to assist the cargo engineer came to the cargo machinery room with the new gasket for the dismantled and cleaned steam trap. The cargo engineer discussed the remaining work with him before re-assembling the trap. The system then needed to be de-isolated and returned to its normal operational condition.
At about 1000, the cargo engineer decided to fully open the steam trap’s inlet valve that he had earlier cracked open. He had turned the hand wheel of the valve about one turn when the valve’s bonnet came away from the valve body. A jet of steam (about 50 mm wide) erupted from the top of the valve’s open body, scalding the cargo engineer’s hands, forehead and neck before he could move clear.
The steam valve’s bonnet had several threads and unscrewing it to the point of release would have required turning it several times. However, it was reported that the bonnet came away after the valve’s hand wheel was turned only one turn (to open). Therefore, it is likely that when the cargo engineer began to fully open the valve, the bonnet was already partially unscrewed and being held by very little thread. The nearly unscrewed bonnet and its missing locking clip may have been more readily apparent visually and by touch/feel, had the valve’s location been less confined, the lighting been better and greater vigilance been exercised.
Work on pressurized shipboard systems can potentially have a high risk of serious injury. Familiarity with repetitive tasks on these systems can sometimes reduce the perception of that risk. Therefore, it is important that the associated risk controls, such as risk assessments and permits to work, are periodically reviewed and carefully completed to effectively identify and mitigate all risks – including the presence of defective system components.
The full report is available here.
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