API 571 case studies
API 571 · Put your knowledge to work in context.
API 571 is the American Petroleum Institute's recommended practice describing damage mechanisms affecting fixed equipment in refineries, and the API 571 individual certification program (ICP) is the associated credential for inspectors and engineers who need to recognize, evaluate, and plan inspection for those mechanisms. The credential is aimed at inspection personnel, corrosion and materials engineers, fixed-equipment engineers, and reliability specialists who work with pressure vessels, piping, heat exchangers, and tanks in refining and related process units. The API 571 case studies are 5 cases and about 4,288 words.
1Crude Preheat Heater Tube Rupture: Characterizing Overheating Before Return to Service
A 5 in OD × 0.250 in minimum-wall carbon steel tube in a crude unit preheat heater split longitudinally after 11 years of service. The rupture is roughly 30 in long and sits in a visibly bulged section; the fracture face is thick, heavily oxidized, and rough, with a short shear lip at each end.
831 words, about 4 min2Undertube Deposits in a Cooling-Water Cooler: Under-Deposit Corrosion or MIC?
A carbon steel shell-and-tube lube oil cooler on an open cooling tower loop was opened after tube failures. Tubes are 3/4 in OD, 12 BWG (0.109 in wall), water on the tube side at 3 ft/s bulk velocity, outlet 112°F.
845 words, about 4 min3Cracking in a Sour Water Flash Drum: SSC, HIC, or SOHIC?
A sour water flash drum, SA-516 Gr. 70, 0.75 in shell, fully post-weld heat treated at 1150°F, has operated 6 years at 165 psig.
829 words, about 4 min4Vacuum Transfer Line Wall Loss: Naphthenic Acid or Sulfidation (and What to Build Back With)?
An 8 in carbon steel vacuum transfer line carries vacuum tower bottoms to the visbreaker at 680°F. Feed assays give TAN 4.6 (potentiometric, whole crude) and 2.9 wt% sulfur; the line has a designed velocity of 14 ft/s at the elbow and downstream straight run, and some low-velocity sections near the tower outlet.
865 words, about 4 min5Cracking in a Lean/Rich Amine Exchanger: Amine SCC After a 'Correct' PWHT
A gas treating unit uses 45 wt% MDEA. The lean/rich exchanger is carbon steel, 0.625 in shell, PWHT at 1200°F with documentation, and has run 9 years.
918 words, about 5 min