Corrosion Allowance — Wall-Life Explorer

PRESETS

PIPE SIZE

MATERIAL (S, E)

DESIGN PRESSURE NOMINAL WALL t_nom CORROSION ALLOWANCE GENERAL CORROSION RATE DESIGN LIFE PIT RATE MULTIPLIER (× general) AGE NOW (for the survey sum)

t_min (B31.3 eq 3a) Start wall t₀ CA needed = rate×life CA provided CA used up at Retire (wall = t_min) Wall now (age) Remaining life now Pit rate Pit reaches t_min Perforation (leak) UT grid average then

What the arithmetic is. CA is a thickness budget for uniform loss: CA ≥ rate × design life. The pressure-retaining floor is separate — t_min = P·D / [2(S·E·W + P·Y)] — and retirement happens when the measured wall reaches it, not when the CA is "used up". API 570 remaining life = (t_actual − t_min) / rate. Switch to Localised pit and watch the grid-average thickness stay comfortably above t_min while the pit bottom goes straight through the wall: the CA never touched it.