APRIL 1, 2015 —The Australian Transport Safety Bureau (ATSB) has issued the report of its investigation into a November 8, 2014 incident onboard an LNG carrier at anchor in Dampier that underscores the fact that work on pressurized shipboard systems can potentially have a high risk of serious injury. In this case, the cargo engineer of the vessel, the Northwest Storm Petrel, was severely scalded when installing a new gasket in a steam trap.
When there is insufficient natural boil-off from LNG in the Northwest Storm Petrel's cargo tanks, its LNG forcing vaporizer utilizes steam to generate LNG vapor for consumption in the ship's boilers. The steam trap of the forcing vaporizer had presented recurrent drainage issues.
On November 8, the cargo engineer, who routinely carried out vaporizer-related maintenance and was familiar with its systems and the task. went to the cargo machinery room (CMR) on the starboard side of the main deck (where the vaporzer was located) to isolate the system before work on it could start. Meanwhile, the integrated rating (IR) assigned to assist him went to the engine room to fabricate a new gasket for the steam trap.
In the CMR, the cargo engineer isolated and locked out the forcing vaporizer's steam supply, outlet, drain and bypass valves. After checking that the system was depressurized, he went to get a permit to work for the task.
The cargo engineer completed the permit to work with the chief engineer, who signed the permit to authorize the work. The cargo engineer then returned to the CMR and started dismantling the steam trap located below the vaporizer.
At about 0900, the IR came to the CMR 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.
Shortly before 1000, the cargo engineer walked around the vaporizer to check if everything was in order for de-isolating the system. Satisfied with the checks, he removed all the valve lock outs.
He then began carefully opening and closing steam valves, regularly checking if everything was normal. The IR stood by and kept watch for abnormal signs. After the vaporizer's steam supply valve had been fully opened, the regulator was set to its normal working pressure.
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. After getting clear of the steam, he took off his gloves, safety glasses and hardhat. The IR helped him out of the CMR and, once outside, his boots and overalls were removed. They then hurried to the nearest safety shower and began cooling the cargo engineer's burns.
Subsequently he was evacuated by helicopter and taken to the local hospital, where a doctor assessed his injuries as superficial and admitted him to a treatment ward.
Later that afternoon, representatives from the Australian Maritime Safety Authority (AMSA) and Northwest Stormpetrel's managers, Shell International Shipping and Trading Company (Shell), boarded the ship to conduct their respective investigations.
The investigations found that the bonnet locking clip on the steam valve was missing and this had allowed the bonnet to unscrew and come away from the valve body. The missing clip was not found, nor could it be established when or how it had been lost.
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.
The ATSB has been advised of the following proactive safety action in response to this occurrence.
Australian Maritime Safety Authority (AMSA)
As the ship's flag state administration, AMSA conducted a regulatory investigation and issued Northwest Stormpetrel's master with an Improvement Notice that required the following action:
- Conduct a detailed analysis and review of procedures and precautions whilst working with pressurized systems.
- Specifically address isolation and de-isolation procedures to ensure adequate protection from injury.
Shell International Shipping and Trading Company (Shell)
Shell's safety investigation identified a number of safety actions to avoid this type of incident.
Procedures and work practices
- The safety actions covered shipboard procedures and practices dealing with risk awareness, risk assessment and work planning, permits to work, defective equipment and safety reporting.
- Focus areas identified for better risk awareness included joining ship briefings, familiarization, work site assessments, personal protective equipment and audits. The development of effective risk assessments, their review and using them for work planning and toolbox talks were also identified. An increased focus on permits to work, particularly for invasive and pressurized systems, and the completion and verification of permits were other identified focus areas. Checking for defective equipment and better reporting through training were also noted.
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 .
Read the ATSB report HERE