Oil Storage
What the questions test
Storage questions focus on integrity, containment, siting and protection. You need to know the features of a compliant tank installation and the reasons behind each feature.
Key concepts
- Tank types: single-skin, integrally bunded, and separately bunded. Bunding capacity is normally 110% of the tank's capacity so a full loss is contained.
- Materials: steel tanks need internal and external protection against corrosion; plastic tanks need UV stability and support on a level, load-bearing base.
- Siting: distance from buildings, boundaries, drains, and sources of ignition; protection from vehicle impact; access for filling and inspection.
- Fill point and vent: fill pipe sized and labelled, with a secure, lockable fill point; vent terminating safely, sized to the fill rate, with flame arrestor where required and screened against insects.
- Pipework: oil supply lines protected, fire valves fitted where required, and bottom-outlet arrangements understood.
- Overfill prevention, contents gauges, and leak detection.
- Pollution prevention: sight gauges must not be of the unprotected glass-tube type; drip trays under fill points.
Traps in questions
- Confusing tank capacity with bund capacity (bund is 110% of tank, not 110% of the fill volume).
- Forgetting that a vent must not terminate where vapour can enter a building or reach an ignition source.
- Missing the requirement for a fire valve on the supply line.
- Assuming a plastic tank needs no base preparation.
Worked example
A 1,000 litre tank needs a bund. Rule of thumb: bund capacity = 1.1 × 1,000 = 1,100 litres, and the bund must not contain a drain valve that could release spilled oil. If a question offers 1,000 litres as the answer, it is the classic distractor.