Tanker Explosion Investigation

Explosion in a Flammable Atmosphere

• An explosion occurred on a tanker near the vent heads of a fuel oil tank
• The Marine Safety Investigation Unit (MSIU) of Transport Malta published Safety Investigation Report 05/2022 regarding the event
• A large tanker was en route to a scheduled dry-docking; technicians were on board assisting with preparations
• Walkway ramps on the main deck were being dismantled to inspect their condition and the piping underneath

Actions Leading to the Explosion

• Two bolts on the last ramp were difficult to undo.
• A technician used an angle grinder to facilitate the work
• Sparks from the grinder flew towards the vent head of a fuel oil tank, causing an explosion
• The vessel sustained damage to its steel structure and port side lifeboat/rafts
• No injuries occurred

Root Causes of the Incident

• There was acceptance of risk and perceived pressure to finish the job quickly
• The technician was unable to remove the last two bolts using an impact wrench, spanners, and a chisel
• The bolts' hexagonal shape was rounded, which made removal harder, so an angle grinder was then used
• The vessel was scheduled to dry dock the next morning, potentially adding pressure to complete the task quickly before the end of daylight
• The technician was motivated to complete the task quickly, and using the angle grinder seemed like a simple solution
• The technician was aware that sparks would be generated, but unaware of flammable gasses around the bunker tank vent head

Recommended Actions

• Refresher webinars should emphasize the "stop work authority"
• Improve safety management and planning when additional crew are on board

Process Safety Fundamentals - IOGP/Step Change

• Step Change in Safety created a "Safety Moment" based on IOGP's Process Safety Fundamentals.
• A downloadable Step Change Safety Moment pack is an available resource for safety meetings or individual toolbox talks

Key Principles

• Incident investigations identify a lack of hazard awareness as an underlying process safety event cause
• Use operating and maintenance procedures, even when familiar with the task
• Speak up when barriers do not feel adequate
• Discuss and use approved limits for the location
• Raise concerns and challenge isolation plans before work starts
• Physically confirm that the system is ready for the intended activity
• Minimize and challenge ignition sources, even in non-hazardous areas
• Look for and discuss change
• Involve others in discussions about change to identify the need for management of change
• Seek advice on change that occurs gradually over time
• Discuss the work plan and signals that indicate progress
• Pause and ask questions when signals/conditions aren't as expected
• Stop and alert supervisors if the activity is not proceeding as expected
• Proactively seek indicators or signals that suggest issues
• Speak up about potential problems, even when unsure of their importance
• Explore the causes of changing indicators or unusual situations

Dropped Object Incident

• IOGP released Safety Alert 334 regarding a dropped object during drilling on a jack-up rig
• The recovery of a 16" riser was needed after running the completion in a subsea well
• A drill-pipe deployed anchor tool, set inside the riser, prematurely released, dropping the riser ~14m
• The Subsea Wellhead Housing (WHH) sealing face was damaged
• No injuries were caused

Factors and Recommendations

• The drill pipe deployed anchor tool load rating had failed because it was not as per advised value
• The tool prematurely released at 35K lbs overpull instead of its rated 114K lbs overpull
• Damage to the wellhead sealing face was addressed and confirmed as satisfactory
• During recovery of casing/riser, the slip mechanism of the anchor tool should be energized constantly by applying pressure
• The shear pins/ratchet mechanism should not be solely relied upon to ensure tool engagement

Safe Use of Ladders and Stepladders

• The Ladder Association, in cooperation with the UK Health and Safety Executive (HSE), published Guidance Document LA455 on safe ladder and stepladder use
• Falls from height remain a common workplace fatality in the UK
• People should use use the right type of ladder for the task, and know how to use it safely

Ladder Use Guidelines

• Only use ladders when they can be used safely like when the ladder will be level, stable, and can be secured
• Check ladders for pre-use
• Take simple precautions to minimize the risk of a fall when using ladders
• What about the condition of the ladder ensuring it is suitable for the work task and in a safe condition before use

"Not a Drill" - LTI Example

• The Marine Safety Forum (MSF) reports in Safety Alert 22-08 an incident where someone was injured during a drill.
• Crew members were performing a stretcher and casualty handling drill on a vessel's daughter craft (rescue boat), when the incident occurred

Incident Details

• A person was closing the daughter craft door as part of the scenario
• The person placed his right hand with the thumb overlapping on the inside of the door frame
• The left hand was then used to forcefully close the door, entrapping the thumb and causing a severe open fracture
• The injured person was cleaned and dressed and then medevac'd to shore

Root Cause and Preventative Actions

• A lack of situational awareness and poor judgement were attributed to the root cause
• The seafarer lost focus and prioritized completing the exercise correctly over safety
• Inspection to assess if door design alterations can incorporate preventative measures
• A Time Out for Safety is recommended to stress trapping points and increase awareness of potential cabin door frame hazards in the future