Remaining Wall Thickness & Retirement Life Calculator
Turns a measured wall thickness and a corrosion rate into a remaining life estimate, a retirement date, and a suggested next inspection date using the common half-life planning rule. Pairs with the Corrosion Rate Calculator.
mm
in
From the applicable code or design calculation (e.g. ASME B31.3 t-min, or a corrosion/structural allowance set by engineering).
mm/yr
mpy
Use a measured or trended rate where available — from the Corrosion Rate Calculator, inspection history, or a conservative design assumption.
Caps the suggested next inspection date even when the half-life rule alone would allow longer — set this to whatever your code or RBI program specifies.
REMAINING LIFE
—
years
Corrosion allowance left—
Retirement date—
Next inspection due—
Quick reference
How this is calculated
Corrosion allowance remaining = current thickness − minimum required thickness
Remaining life = corrosion allowance remaining ÷ corrosion rate
Retirement date = today + remaining life
Next inspection (half-life rule) = the sooner of half the remaining life, or your maximum interval cap
About the half-life rule
A common, conservative planning convention: inspect again no later than halfway through the estimated remaining life
It's a general rule of thumb, not a substitute for a formal RBI (risk-based inspection) program or the specific requirements of API 510/570/653, ASME, or your company's inspection code
Corrosion doesn't always progress linearly — trend actual measurements over time rather than relying on a single rate indefinitely
Where the minimum thickness comes from
Pressure-retaining components: typically a code-calculated t-min (e.g. ASME B31.3 pressure design thickness)
Structural members: a minimum thickness from the original structural design, allowing for the intended safety margin
Always confirm against the actual design basis for the specific component — this tool doesn't calculate t-min itself
Good practice
Use the same measurement location(s) each inspection so the trend is meaningful
Treat a single corrosion rate as a working estimate — re-derive it after each new inspection reading
Localized corrosion (pitting) can retire a component long before general wall loss would — this tool assumes uniform thinning