Lessons learned: Multi-disciplinary pre-job risk assessment critical

The incident

While cutting a section of 12-inch pipe using a five-foot cutting torch, a flash fire struck the contractor on the right side of his face. Fire watch personnel quickly extinguished the fire, and the contractor was immediately transported to shore to treat his burns.

Six months before this incident, the pipe was flushed, filled with seawater, and inspected by opening several needle valves. Clear salt water was discharged before the hot work activity commenced.

However, releasing the salt water did not eliminate the trapped hydrocarbons from the pipe. The first cut was made on the lower end of the pipe without incident, suggesting that the line did not contain flammable vapors or liquids.

When the contractor made the second cut on the upper end of the pipe, the gas ignited, causing the flash fire.

Probable cause

• Insufficient identification of hazards: The Job Safety Analysis (JSA)2 covered the pipe-cutting operation and several other decommissioning activities. It addressed common hazards for this job but only briefly mentioned testing for flammable gas.
• Inadequate work planning: A detailed work procedure specific to cutting and removing piping was not developed, and the entire decommissioning project did not have a work plan.
• Deficient work-permitting system: There was no isolation verification (e.g., mechanical barrier) nor pre-job validation that the pipe contained no flammable gas; the pipe was presumed safe and ready for demolition.
• Insufficient policies and procedures: The hot work permit and JSA were unclear about gas detection requirements for the Lower Explosive Limit (LEL).

Lessons learned

• Always assume that all piping and vessels that previously contained flammable liquids or vapors may still contain these flammable gasses until it has been positively verified that there is no longer hazardous. Piping or vessels isolated from potential hydrocarbon sources using only a single barrier (e.g., a closed ball valve) should also be assumed to contain flammable hydrocarbons.
• Understand that gravity draining a vessel or pipe and opening them to the atmosphere may not be sufficient to remove all flammable liquids and vapors.
• Plan and conduct multi-disciplinary pre-job risk assessment.
• Determine no hydrocarbons are present inside vessels or piping before cutting or breaking containment.
• Remove hydrocarbons if they are present.
• Ensure hydrocarbons will not enter piping or vessels during the job (e.g., closing and locking valves, installing pipe plugs, etc.).
• Develop and follow hot work policy/procedures5 for tasks involving special hazards (e.g., welding, flame cutting, removing barriers separating hydrocarbons from work areas (breaking containment), working at heights, working in confined spaces, etc.).
• Ensure all contractors use proper work permits and comply with requirements.
• Ensure all operations and contract personnel attend and participate in a pre-job JSA meeting to evaluate the specific job tasks, hazards, and necessary control measures for all hot work and ensure that the supervisors of all phases of the work know and understand the complete job scope.
• Ensure all operations and contract personnel involved in hot work attend and participate in a pre-job meeting/toolbox talk.
• Consider splitting larger jobs with multiple tasks into organized respective units via JSAs and work permits.
• Ensure operator, contractor, and service company employees recognize and understand that inadequate communication is one of the most common causes of major accidents, especially when performing hot work.
• Always ensure that all individuals involved in the task wear proper Personal Protective Equipment (PPE).