API 510 and API 570
Inspection interval calculator
Pick the risk rank and enter the remaining life. The calculator applies the base interval for the rank, caps it at half the remaining life, floors it at three months, and states the basis it used, the way the platform does before an inspector confirms the date.
Base interval for rank
24months
Half-life cap
36months
Interval
24months
In years
2.00years
Advisory result. Provisional until a qualified inspector or engineer verifies it against the governing code edition.
How it works
- 01Base interval by rank: 1 = 6 months, 2 = 12, 3 = 24, 4 = 48, 5 = 120.
- 02Half-life cap: floor(remaining life / 2, in months). When it is shorter than the base, it governs.
- 03Floor: never less than three months.
- 04Basis: the result states whether the rank or the half-life governed, so the record carries the reason.
Formulas
cap = floor(RL / 2 x 12) monthsI = max(min(base(rank), cap), 3)Read before you rely on it
- The code maxima (for example ten years for many API 510 internal intervals, and the API 570 class maxima) still apply on top of this result.
- The remaining life entered should come from the governing corrosion rate, not the most comfortable one.
- Advisory. The interval is set by the inspector under the owner's program.
Answers
Questions about this calculator
What does 'half the remaining life' mean in practice?
If the equipment has eight years of remaining life at the governing corrosion rate, the next inspection is due within four years, unless the code maximum or the risk rank says sooner.
Why is there a three-month floor?
Below three months an inspection interval stops being a program and becomes a repair decision. The platform floors the interval there and expects a disposition instead.
Where does the risk rank come from?
From the RBI risk rank calculator on this site, or from the platform's RBI scoring: probability from remaining life and corrosion rate, consequence from fluid and system criticality.
Is the code maximum applied here?
Not in this calculator. It shows the rank and half-life logic the platform uses; the class or equipment maximum from API 510 or API 570 is a separate check the inspector applies.