| Deviation | Typical causes | Typical consequences | Typical safeguards |
|---|---|---|---|
| Overfill | Wrong line-up; tank gauge stuck; transfer not stopped; receipt larger than ullage | Liquid spill, vapour cloud, fire or explosion, environmental damage | Tank gauge with high alarm; independent high-high level with automatic shut-off; ullage check before transfer; bund |
| Overpressure | Filling faster than vent capacity; blanket gas regulator failure | Roof or shell damage | Pressure/vacuum relief valve sized for maximum rates; emergency vent |
| Vacuum | Pump-out faster than vent capacity; vent blocked | Tank implosion | PVRV; inspection of vents |
| Static ignition | Splash filling of low-conductivity liquids | Fire in the vapour space | Bottom entry, flow velocity limits, bonding and earthing |
| Leak from the bottom | Corrosion | Soil and groundwater contamination | Inspection; leak detection; double bottom |
| Rim seal fire (floating roof) | Lightning | Fire | Rim seal fire detection and foam system |
The overfill scenario has caused some of the best-known incidents in the industry; see the knowledge articles on Buncefield (2005) and the Caribbean Petroleum terminal (2009).
Written for First Out AI as engineering guidance. It supports engineering work and does not replace it; check every value against your standards, certificates and company rules with a competent functional safety engineer.