Aboveground storage tank inspection: what gets looked at over an asset's life

The cycle, from the outside in

Four levels of attention, with very different costs and very different findings.

• Frequent walk-arounds by site personnel: leaks, obvious coating failure, foundation washout, blocked vents, damaged appurtenances. Cheap, and the only one that happens often enough to catch a change.
• Formal external inspections by a certified inspector: a structured look at the same things, plus measurement.
• Ultrasonic thickness work: how much metal is left, and where it is going.
• Internal inspection: the floor, the underside of the roof, the internal coating and the parts of the shell nobody can see from outside.

Most owners under-invest in the first level and then buy the fourth in a panic. The cheapest inspection programme in the long run is the one where somebody competent walks the tank farm regularly and writes down what changed.

What triggers an inspection

In practice, one of five things puts a tank on the schedule.

1. A due date derived from the previous inspection and its evaluation.
2. A regulatory or insurance requirement, or a customer audit.
3. A change of service, a different product, a different temperature, a different duty.
4. A finding: a leak, a settlement reading that moved, a coating failure, water in product.
5. A transaction: due diligence before purchase, lease or divestment of a facility.

The fifth is worth naming because it comes with a schedule nobody controls. A tank inspection inside a deal timetable is priced differently from the same inspection planned a year out.

What the regulatory picture looks like from a distance

Several regimes can touch the same tank at once: federal rules covering oil storage and spill prevention, state programmes that may adopt industry standards directly, fire and building codes, and occupational safety rules governing the work itself.

The workable approach: establish who is asking, then write the scope to satisfy the strictest requirement rather than the average one. It is cheaper than discovering the difference during an audit.

Where the money actually goes

On an internal inspection, the inspection itself is often a minority of the total. Emptying, cleaning, waste disposal and lost throughput dominate, which is set out in detail on what drives the cost.

This is why scope discipline pays here more than in most trades. Buying a slightly better inspection while the tank is already open is cheap. Reopening the tank because the scope was thin is not.

Frequently asked