BSafe Case Study 1 — The Tank Wasn't Empty, and Nobody Checked a Second Way

A Level Gauge That Was Lying

Sludge had been pumped from the Bilge Separator Oil Tank into No.2 Waste Oil Settling Tank. The level gauge on No.2 wasn't showing the right quantity — it had malfunctioned. A Job Hazard Analysis was written up, and the Second Engineer was tasked with draining the tank's residues and fixing the gauge, with the Third Engineer assisting.

The Second Engineer opened the drain valve to let sludge run by gravity to the BSO Tank. The Third Engineer climbed on top of the tank and turned the scale reduction wheel, reporting it working. The Second Engineer noticed a small movement on the level indicator while the valve was open. Then he opened the self-closing drain valve — a small amount of water came through, then stopped. That was enough for both of them to be convinced the tank was empty.

Two Metres Up, Four Nuts Still On

The Third Engineer went to open the manhole cover, about two metres above the floorplates. He removed all the nuts except four, which he loosened but didn't take out. He saw no leakage — so he pulled the cover without removing the remaining nuts. Hot oil splashed out of the manhole bottom onto him, standing on a folding ladder. The Second Engineer pulled him clear and stripped off his oil-soaked coveralls. The Chief Officer gave first aid; a helicopter arrived roughly two hours later and got him to a shoreside hospital. He died there 12 days after the accident.

What HBMCI's Investigation Found

• The hazard of an unknown quantity of hot sludge remaining in the tank, caused by the malfunctioning gauge, was never actually identified as a hazard in its own right.
• A small trickle of water from the drain valve and a working scale-reduction wheel were treated as proof the tank was empty — confirmation bias, in HBMCI's own framing: information that fit what the engineers already believed was accepted without a second, independent check.
• The vessel's Planned Maintenance System had no routine guideline for cleaning or maintaining the gauges to prevent them jamming with sludge in the first place.
• The tank had no sounding pipe — no alternative way to verify contents once the primary gauge was known to be unreliable.
• The Third Engineer wore a company-issued cotton coverall, which gave only limited heat protection and let the hot liquid through.