API 571 study guide
API 571 · Work through your exam, one topic at a time.
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 study guide has 6 sections and about 2,112 words.
01General Principles of Damage Mechanisms and Failure Analysis
API 571 is organized around damage mechanisms rather than equipment. For each mechanism the text gives the damage morphology, susceptible materials, critical process variables (temperature, environment and chemistry, stress, velocity), the equipment where it occurs, inspection and monitoring, prevention and mitigation, and related mechanisms.
357 words, about 2 min02Mechanical and Metallurgical Failure Modes
Mechanical failures come from the wrong combination of stress and resistance. Overload produces either ductile fracture (dimples, shear lip, visible deformation) or brittle fracture (cleavage, no deformation, rapid).
343 words, about 2 min03Uniform, Localized, and Under-Deposit Corrosion
Uniform or general corrosion removes metal broadly and predictably; it is managed with corrosion allowance, and rates come from coupons, probes, and thickness surveys. Galvanic corrosion occurs where dissimilar metals contact in an electrolyte; severity increases with potential difference, cathode-to-anode area ratio (a small anode to a large cathode is worst), and conductivity.
347 words, about 2 min04Environment-Assisted Cracking
Environment-assisted cracking requires a susceptible material, a specific environment, and tensile stress, usually residual stress from welding; removal of any leg prevents cracking. EAC is threshold driven, so inspection is for cracks rather than thinning, and the crack morphology is usually branched and brittle with little general metal loss.
361 words, about 2 min05High-Temperature Corrosion and Metallurgical Degradation
At elevated temperature, corrosive species in the process attack metal at rates that depend on temperature, partial pressure of the aggressive species, and alloy content. Sulfidation occurs in H2S/H2 streams from roughly 500 to 1000 deg F and is resisted by increasing chromium.
377 words, about 2 min06Refining Process Unit Damage Mechanism Susceptibility and Inspection Planning
Unit questions reward knowing the environment each stream creates. Crude units combine chloride hydrolysis to HCl in the atmospheric tower overhead, ammonium chloride deposition and under-deposit corrosion, sour water, naphthenic acid corrosion, sulfidation, and extensive CUI.
327 words, about 2 min