API 570 cheat sheet

API 570 covers in-service metallic piping systems and components originally designed to ASME B31.3, B31.1, or equivalent; it does not cover new construction, pipelines (B31.4/B31.8), boiler or furnace tubes, instrument tubing, or nonmetallic piping.

A piping system includes pipe, flanges, gaskets, bolting, valves, fittings, and supports between defined battery limits.

Inspection under API 570 means visual and NDE activities performed to determine condition; examination is the NDE itself, performed by an examiner.

Only a holder of a valid API 570 certification may act as the inspector; an examiner is qualified for the specific NDE method and need not be API 570 certified.

The owner/user establishes the inspection plan, defines which piping is in scope, approves repairs and alterations, and retains records.

Alterations and rerating require engineering design approval; a rerating changes the MAWP or temperature rating and must be documented.

Repair organizations and welders must be approved by the owner/user; welding must follow ASME Section IX qualified procedures.

API 570 does not override the original code of construction; minimum thickness and design rules come from the applicable ASME B31 code.

General (uniform) corrosion removes metal evenly; rate in mpy = 1000 × thickness loss in inches ÷ years in service.

Localized mechanisms-pitting, crevice, galvanic, and under-deposit corrosion-cause penetration with little overall metal loss.

CUI affects carbon steel externally and causes external chloride SCC in austenitic stainless steel, typically between 50 °C and 175 °C (120–350 °F).

Erosion-corrosion accelerates at high velocity, turbulence, or wet steam; inspect elbows, tees, reducers, and downstream of valves.

MIC produces pitting in stagnant, low-flow, or dead-leg water service; symptoms include tubercles and black deposits.

Wet H2S service can cause hydrogen blistering, HIC, and sulfide stress cracking; hardness and PWHT controls apply.

At elevated temperature, creep and stress rupture produce bulging and cracking; graphitization affects carbon steel above about 800 °F.

Cyclic or vibrating service causes fatigue cracking, usually initiating at weld toes, branch connections, and supports.

Buried piping is subject to soil corrosion; coating condition and cathodic protection determine the external corrosion rate.

Remaining life = (actual thickness − minimum required thickness) ÷ corrosion rate; use the governing (usually higher short-term) rate.

Inspection interval must not exceed the lesser of half the remaining life or 10 years; if remaining life is below 10 years, the interval cannot exceed half that life.

Corrosion rate = (previous thickness − current thickness) ÷ elapsed time; long-term rate uses initial-to-current readings, short-term rate uses the last two.

Minimum required thickness is calculated by the applicable ASME B31 code from design pressure, diameter, allowable stress, weld joint factor, and corrosion allowance.

A repair restores safe condition without changing design; an alteration changes geometry, materials, or design conditions and requires engineering approval.

Rerating changes MAWP or temperature rating and requires calculations, inspector review, and updated records.

Repair and alteration welds require qualified WPS/PQR per ASME Section IX, welder qualification, and NDE as specified.

A hydrostatic test is typically 1.5 × design pressure for B31.3 piping; pneumatic testing is permitted at lower ratios with added safeguards.

Injection points and mixing points are high-corrosion locations and require shorter inspection intervals than the parent line.

Ultrasonic thickness measurement is the principal method for determining remaining wall; readings at fixed TMLs are compared over time.

TMLs are placed at elbows, tees, reducers, low points, and areas of turbulence or known corrosion.

NDE methods include VT, PT, MT, UT, and RT; performance and qualification follow ASME Section V.

Welding qualifications follow ASME Section IX; weld inspection follows the applicable B31 code and API 577.

API 574 provides detailed piping inspection practices; API 571 describes damage mechanisms; API 578 covers material verification.

Inspectors must have Jaeger 1 (or equivalent) near vision at 12 inches and adequate color vision, re-verified periodically.

Insulation must be removed at suspect CUI locations to allow external visual and UT inspection.

Pressure tests verify tightness and strength after repairs or alterations; test medium, temperature, and pressure are recorded.

Records must be retained for the life of the piping system and include inspection reports, thickness data, repairs, alterations, and reratings.

Each inspection report records date, locations, methods, findings, remaining life, recommendations, and next inspection date.

Repair records include repair description, materials, WPS/PQR, welder ID, NDE results, heat treatment, and pressure test data.

Rerating records include design calculations, new MAWP and temperature, approvals, and revised inspection requirements.

Thickness records list each TML, its location, date, and reading, enabling corrosion-rate and remaining-life calculations.

Alteration records include design drawings, calculations, and engineering approval.

Records must be available to the API 570 inspector and authorized personnel; controlled electronic records are acceptable.