LPG storage — loss of containment
The canonical process-safety bowtie — three threats fan in through preventative barrier chains, three consequences fan out through mitigative chains, around the central loss-of-containment top event.
For the process-safety engineer presenting a major-accident scenario
What this shows
The integrating picture of barrier-based risk management for one major-accident scenario. The hazard ("LPG stored under pressure") sits above the central top event — the moment control is lost. To the left, three credible threats each fan in through a chain of preventative barriers (grey, on the line) that stop them reaching the knot. To the right, three consequences each fan out through a chain of mitigative barriers that limit the damage if the top event occurs.
This is the shape a process-safety reviewer expects on an A3: defence-in-depth depth on both wings, the knot in the middle, the hazard above. Correct by construction — the engine would reject any threat or consequence drawn with no barrier (a Swiss-cheese cartoon), so every line you see genuinely passes through a control.