The Context
An operating team at an oil refinery noticed that a cooling water line feeding a highly exothermic reactor jacket was scaling up internally, restricting flow. To quickly fix the issue before the next major turnaround, the maintenance team decided to run a temporary, flexible high-pressure hose from a nearby utility water header directly into the jacket inlet. Because it was “just a utility line change,” it was treated as a minor repair and bypassed the standard Management of Change (MOC) process.
During operation, the utility water pressure dropped unexpectedly. The high-pressure reactor process fluids overpowered the temporary line, back-flowed through the flexible hose, and contaminated the entire facility’s utility water grid with flammable hydrocarbons.
Key Learnings:
- No Change is Too Small: Trevor Kletz dedicated an entire body of work to modifications, famously stating that most disasters happen because someone modified a plant without understanding the secondary consequences.
- The “What-If” of Temporary Piping: Any change to the physical plant layout—including temporary hoses, jumper wires in a control panel, or software overrides—must go through a formal safety screening.
- HAZOP Updates: If a temporary change alters the process flow or piping boundaries as drawn on the P&IDs, it invalidates the existing HAZOP study. A mini-HAZOP review must be conducted for the temporary state.
Labels: Management of Change, Plant Modification, Incidents