Could hydrogen re-enter the line? The SK Energy Ulsan maintenance explosion
An explosion during maintenance on 17 October 2025 ultimately killed two workers and injured four at SK Energy’s Ulsan facility, according to follow-up reporting.
The casualty figures changed
Six people were initially injured. Two subsequently died, on 18 and 23 October.
Investigators examined the site and compliance with safety arrangements. Hydrogen leakage was a reported hypothesis; the exact ignition and isolation-failure mechanisms were not established in this account.
Stopping is not verified isolation
Before intrusive work, identify the equipment boundary and demonstrate control of incoming material and remaining energy. A stopped process is not by itself proof that a pipe can be opened.
HSE · 설비 격리 / Safe isolation of plant and equipment
Check your workplace
- Have all connected flow paths been identified?
- How was isolation verified?
- Who communicates operating changes to maintenance?
Use an unambiguous work boundary
Operations and maintenance should name the same equipment and opening points. Communicate changes and shift handovers; reassess authorisation when conditions move outside the agreed scope.
Do not rely on human senses
Use appropriate detection and site procedures rather than smell or appearance. On a suspected release, withdraw and report the equipment and symptoms from a safe location instead of approaching or manipulating fittings.
Putting it into practice
Before opening a line, confirm its identifier, the isolation boundary, the verification result and the person responsible for communicating changes. The HSE references describe UK guidance, to be adapted within local requirements.
Technical insight
Identify routes for re-entry into the line
A hydrogen maintenance boundary may involve more than the nearest valve. Review possible connections and how the safe state will be maintained during the task.
Reconcile line identification and field conditions, then consider effects of operating actions nearby. This is an application review, not a claim about an unconfirmed action in the accident.
Korean safety resources
- KOSHA GUIDE C-C-2-2025 · Chemical plant maintenance planning
Korean-language PDF on maintenance planning and preparation; technical recommendations.
Sources
- 경향신문 · SK에너지 수소배관 폭발 사망자 2명대한민국 / South Korea
- HSE · 설비 격리 / Safe isolation of plant and equipment영국 지침 / UK guidance
- HSE · 설비 정비 / Maintenance of work equipment영국 지침 / UK guidance