Can overfill protection work when the gauge stops?: The Buncefield oil depot explosion
Explosions and a major fire occurred at Buncefield, United Kingdom, on 11 December 2005. The case highlights both normal level measurement and independent overfill protection.
Fuel continued to arrive while indication stopped
The HSE/EA report describes a stuck gauge on Tank 912 and failure of the independent high-level protection to prevent overfilling. Overflow generated a vapor cloud followed by explosions and fire.
HSE and Environment Agency: Buncefield — Why did it happen?
Two displays are not necessarily two barriers
Distinguish normal measurement from the overfill-protection function. Shared sensing, power or signal paths can expose apparently separate devices to the same failure.
Trace the complete path from sensing through decision and alarm to final isolation. Required independence and reliability should follow the actual risk assessment and competent engineering design.
HSE and Environment Agency: Buncefield — Why did it happen?
Check your workplace
- Have common failure paths between measurement and protection been assessed?
- Are bypass removal and normal restoration verified after tests?
- Is there sufficient margin for detection and isolation at maximum inflow?
Verify restoration after testing
An HSE safety alert addressed the test mechanism and restoration of particular level switches. A successful test record does not alone demonstrate that protection remains available in service.
Include test conditions, outputs, final-element action, bypass removal, restoration and handover. Apply the actual manufacturer’s instructions; do not generalize the mechanism of the product discussed in the alert.
Consider the time remaining before overflow
Review available capacity, maximum inflow and detection-to-isolation time together. Include continued inflow after shutdown where relevant.
A changed route, receipt rate or receiving tank needs reassessment. Containment and drainage controls are important but cannot replace overfill prevention.
Putting it into practice
Before receipt, match the tank, route and permitted quantity with protection-system test and restoration records. If level indication freezes or the material balance becomes inconsistent, use the approved stop procedure rather than continuing blindly.
Korean safety resources
- KOSHA · Practical safety handbook 57: Inorganic chemical manufacturing (2021)
Korean handbook: chemical plant fire/explosion/leaks p.166 and turnaround maintenance p.203. Prevention guidance, not an investigation of this incident.
Sources
- HSE: Buncefield investigation영국 / United Kingdom
- HSE and Environment Agency: Buncefield — Why did it happen?영국 / United Kingdom
- HSE safety alert HID 6-2010: Level switches on large tanks영국 / United Kingdom
- Rob Emms photograph licence · CC BY-SA 2.0사진 이용 조건 / Photograph licence