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API 570 Piping Inspector Cheat Sheet

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Calculations & Intervals

  • Not published of exam
  • Corrosion Rate Remaining Life Inspection Interval MAWP Recalc Weld Joint Factor Hydro Test

Welding Procedure Review

  • Not published of exam
  • WPS Review PQR Review WPQ Review Essential Variables P-Numbers RP 577

Nondestructive Examination

  • Not published of exam
  • RT PT MT VT UT Thickness Leak Testing

Practical Knowledge General

  • Not published of exam
  • CML Placement Circuitization Deadleg Inspection Injection Points Small Bore Piping Records

Practical Knowledge Specific

  • Not published of exam
  • Damage Mechanisms RP 574 Components RP 576 PRDs RP 578 PMI PCC-2 Repairs

Quick Facts

  • Exam API 570
  • Credential Piping Inspector
  • Body API
  • Questions 170 (140 scored)
  • Time 7.5-hour exam day
  • Pass score 400 of 500 scaled
  • Format Closed + open book
  • Level Advanced, experienced inspectors
  • Blueprint Feb 2026 BOK

Corrosion Rate Choice CA

  • Compare LT and ST rates; always use the faster
  • LT: long baseline trend ST: recent short trend Governing: pick higher rate

LT vs ST Corrosion Rate CA

Long-Term (LT)

  • Since initial baseline thickness
  • Covers full service history

Short-Term (ST)

  • Since previous reading only
  • Flags recent rate acceleration
  • Use the higher rate

Inspection Interval Picker CA

  • Remaining life over 20 years → Table 1 max interval ( Class-based cap applies )
  • Remaining life under 4 years → Full life, max 2yr ( Short-life exception rule )
  • RBI assessment available → RBI-set due date ( Per API 580 )
  • No RBI, Class 1 → 5yr thickness and external ( Shortest fixed interval )
  • No RBI, Class 3 → 10yr thickness and external ( Longest fixed interval )
  • Injection point circuit → 3yr max thickness ( Localized corrosion risk )

Corrosion Rate Formulas CA

  • LT rate Baseline minus actual, per year
  • ST rate Previous minus actual, per year
  • Governing rate Use the faster of two
  • t-actual Thickness measured at inspection
  • t-required Design minimum before allowances
  • t-initial Baseline thickness at install
  • Remaining life Actual minus required, over rate

Table 1 Interval Order CA

  • Class 1 tightest, Class 4 loosest inspection interval
  • Class 1: 5 and 5 Class 2: 10 and 5 Class 3: 10 and 10 Class 4: optional both

Point-to-Point vs Circuit Method CA

Point-to-Point

  • Per-CML worst case only
  • No statistical pooling used
  • Simple and conservative

Circuit/Statistical

  • Pools circuit-wide CML data
  • Needs fairly uniform corrosion
  • Uses a confidence interval
  • Per-point vs circuit-wide averaging

Inspection Intervals (Table 1) CA

  • Class 1 5 years thickness and external
  • Class 2 10yr thickness, 5yr external
  • Class 3 10 years thickness and external
  • Class 4 Optional, owner-user discretion
  • Injection points 3-year max thickness interval
  • Soil-to-air interface By class; see API 574
  • Half-life rule Max interval = half remaining life
  • Short remaining life Under 4yr: full life, max 2yr

MAWP & Thickness Design CA

  • MAWP recalc Actual t minus 2x loss
  • t-min straight pipe ASME B31.3, 304.1.1
  • Blank thickness ASME B31.3, 304.5.3 rule
  • Ej Weld joint quality factor
  • Ec Casting quality factor
  • Hydro test pressure About 1.5x design pressure
  • Pneumatic test Riskier; lower safety margin
  • Brittle fracture margin 30F above MDMT, thick pipe

Flange, Impact & Thermal Calcs CA

  • Flange rating Temperature sets max pressure
  • Flange class Material plus temperature table
  • Impact exemption Min metal temp curve
  • Charpy V-notch Min required impact value
  • Preheat temperature Set by weld size table
  • Thermal expansion Appendix C, Table C-1

Weld Document Trio WE

  • WPS is how; PQR proves it; WPQ certifies welder
  • WPS: written instructions PQR: procedure test record WPQ: welder skill proof

PQR vs WPQ WE

PQR

  • Qualifies the weld procedure
  • Records mechanical test results
  • One per supporting WPS

WPQ

  • Qualifies the individual welder
  • Tests welder's actual skill
  • Per welder, per process
  • Procedure proof vs person proof

Welding Review Checklist WE

  • Reviewing a WPS → Check essential variables ( Match to qualified PQR )
  • Reviewing a PQR → Check mechanical test results ( Proper type and pass )
  • Reviewing a WPQ → Check welder qualification ( Coupon per qualified WPS )
  • Dissimilar base metal joint → Exclude from exam scope ( Not tested this exam )

WPS, PQR, WPQ Review WE

  • WPS Welding Procedure Specification, the how
  • PQR Procedure Qualification Record, proves WPS
  • WPQ Welder Performance Qualification, proves welder
  • Essential variable Change requires requalification
  • Nonessential variable Change needs no retest
  • Supplemental essential Not tested on this exam
  • Signed & dated Required on PQR and WPQ

Essential vs Nonessential Variables WE

Essential Variable

  • Requires WPS requalification test
  • Affects mechanical properties directly

Nonessential Variable

  • No requalification needed here
  • Documentation update only needed
  • Requalify vs simply revise

Welding Review Limits WE

  • Processes covered SMAW, GTAW, GMAW, or SAW
  • One process per WPS No multi-process WPS on exam
  • Filler metal limit One filler metal per process
  • Base metals tested P-1, P-3, P-4, P-5, P-8
  • Dissimilar metals Excluded from exam scope
  • Brazing Not covered on this exam
  • Transition temps (exam) 1330F lower, 1600F upper

NDE Surface vs Volume ND

  • PT and MT see surface; RT and UT see inside
  • PT/MT: surface only RT/UT: internal volume VT: overall visual condition

RT vs UT ND

RT

  • Internal flaws and slag
  • Porosity and inclusion detection
  • Film or digital image

UT

  • Elongated, planar flaw sizing
  • Thickness measurement capability
  • Angle beam for cracks
  • Imaging vs sizing and thickness

NDE Method Picker ND

  • Surface cracks, nonmagnetic material → PT ( Liquid penetrant )
  • Surface cracks, ferromagnetic material → MT ( Yoke or prod )
  • Internal flaws, weld slag → RT ( Radiography )
  • Elongated internal or surface flaw → UT flaw detection ( Angle beam technique )
  • Manual thickness measurement needed → UT (SE-797) ( Pulse-echo contact method )
  • Overall external condition check → VT ( Visual examination )
  • Through-thickness defect suspected → Leak test ( Article 10 method )

Section V NDE Methods ND

  • RT (Article 2) Radiography for internal flaws
  • PT (Article 6) Penetrant for surface cracks
  • MT (Article 7) Yoke/prod for ferromagnetic cracks
  • VT (Article 9) Visual for overall condition
  • Leak test (Article 10) Bubble test, direct pressure
  • UT (Article 23) SE-797 manual thickness only
  • IQI Image quality indicator for RT

PT vs MT ND

PT

  • Nonmagnetic material required
  • Surface-breaking flaws only
  • Liquid dye penetrant

MT

  • Ferromagnetic material required
  • Yoke or prod technique
  • Magnetic flux leakage
  • Material magnetism decides method

NDE Method Selection Notes ND

  • Surface vs volumetric PT/MT surface, RT/UT internal
  • Calibration Required before every NDE method
  • Record keeping Required for all NDE articles
  • Ultrasonic accuracy limits Coatings, roughness, temp above 150F
  • Owner/user responsibility Define procedures and acceptance criteria
  • Section V scope Main article body only tested

Class 1 vs Class 2 Piping PR

Class 1

  • Immediate emergency potential
  • Rapid vaporizing, H2S, HF
  • 5-year thickness and external

Class 2

  • Most unit process piping
  • Slow-vaporizing, on-site service
  • 10yr thickness, 5yr external
  • Consequence of failure severity

Piping Class Picker PR

  • Rapid vaporizing C2-C4 → Class 1 ( Immediate emergency risk )
  • H2S over 3% → Class 1 ( Toxic gaseous stream )
  • Anhydrous HCl or HF → Class 1 ( Acid service )
  • Piping over water or roads → Class 1 ( Public exposure risk )
  • Slow-vaporizing on-site hydrocarbon → Class 2 ( Most unit piping )
  • On-site acids or caustics → Class 2 ( Strong chemical service )
  • Off-site tank farm lines → Class 3 ( Remote, below flash point )
  • Nonflammable utility service → Class 4 ( Steam, air, nitrogen, water )

CML & Circuitization PR

  • CML Condition monitoring location on circuit
  • Circuit Grouped piping with similar corrosion
  • More CMLs Higher risk or localized corrosion
  • Fewer CMLs Low risk, noncorrosive, straight run
  • Point-to-point method Worst-case CML sets interval
  • Circuit/statistical method Pools data, needs uniform corrosion

Closed-Book vs Open-Book Exam PR

Closed-Book

  • 110 questions, 2.75 hours
  • Memorized formulas and rules
  • No references allowed

Open-Book

  • 60 questions, 3.75 hours
  • On-screen PDF references given
  • Only effectivity sheet documents
  • Memory speed vs lookup speed

Deadlegs, SBP & Injection Points PR

  • Deadleg Low-flow branch, accelerated corrosion risk
  • Small bore piping Vents, drains, bridles, level
  • Injection point upstream 12in or 3 diameters, greater
  • Injection point downstream 25ft or next flow-direction change
  • SBP Class 1/2 Same rules as primary piping
  • Threaded connections Inspect like small-bore piping
  • Auxiliary piping Optional; risk-based inspection only

Records & Program Basics PR

  • Permanent records Kept for piping system life
  • Progressive records Updated after every inspection
  • Baseline thickness Set at installation inspection
  • Owner-user duty 20% time on inspection work
  • CPD hours 24 hours per 3-year cycle

Damage Mechanism Memory Groups PR

  • Amine, caustic, and chloride all cause stress cracking
  • SCC group: amine, caustic, chloride Corrosion group: CUI, sulfidation, MIC Mechanical: fatigue and erosion

Sulfidation vs Sour Water Corrosion PR

Sulfidation

  • High-temperature sulfur compound attack
  • No water phase required

Sour Water Corrosion

  • Aqueous H2S and cyanide
  • Acidic condensate, pitting common
  • Temperature regime and phase differ

Damage Mechanisms (RP 571) PR

  • Amine SCC Rich amine unit cracking
  • Atmospheric corrosion Weather-exposed external metal loss
  • Boiler water corrosion Condensate and steam system loss
  • Caustic corrosion Concentrated NaOH localized attack
  • Caustic SCC Cracking under caustic and stress
  • Chloride SCC Austenitic stainless under chloride/stress
  • CUI Corrosion under wet insulation
  • Erosion/erosion-corrosion Flow-induced wall thinning
  • Galvanic corrosion Dissimilar metals, electrolyte present
  • HCl corrosion Hydrochloric acid, often overhead
  • Mechanical fatigue Vibration-induced cyclic cracking
  • MIC Microbiologically influenced localized corrosion
  • Soil corrosion Buried piping external attack
  • Sour water corrosion Acidic H2S condensate attack
  • Sulfidation High-temp sulfur compound thinning

PRDs (RP 576) & PMI (RP 578) PR

  • PRD test interval 5yr typical, 10yr clean service
  • Stuck-shut default 150% of set pressure limit
  • PRD scope tested RP 576 sections 5, 6.1-6.5, 7
  • PMI program Confirms installed material matches spec
  • PMI verification 100%, risk-based, or sampling
  • Retroactive PMI Targets legacy alloy piping systems

PCC-2 Repair Articles PR

  • Art. 201 Butt-welded insert plates
  • Art. 206 Full encirclement reinforcing sleeves
  • Art. 209 Alternatives to postweld heat treatment
  • Art. 210 In-service welding on carbon steel
  • Art. 211 Weld overlay and clad restoration
  • Art. 304 Flaw excavation and weld repair
  • Art. 305/306 Flange repair, mechanical clamp repair

RP 574 & RP 577 Basics PR

  • RP 574 scope Entire document tested, components
  • RP 577 scope Entire document tested, welding metallurgy
  • Piping components Valves, flanges, fittings inspection practices
  • Weld metallurgy basics HAZ, dilution, hardness for inspectors
  • RP 578 scope Material verification, new and existing

Common Traps

LT rate ≠ ST rate

  • LT uses the baseline ≠ ST uses the previous reading

Remaining life ≠ corrosion rate

  • Life counts years left ≠ Rate counts loss per year

Class 1 ≠ Class 3 interval

  • Class 1 is all 5-year ≠ Class 3 is all 10-year

PQR ≠ WPQ

  • PQR qualifies the procedure ≠ WPQ qualifies the welder

Essential ≠ nonessential variable

  • Essential change needs retest ≠ Nonessential change just noted

RT ≠ UT purpose

  • RT images internal flaws ≠ UT sizes and measures thickness

Closed-book ≠ open-book portion

  • Closed-book tests memorized rules ≠ Open-book tests document lookup

Circuit ≠ single CML

  • Circuit groups many CMLs ≠ CML is one location

Last Minute

  • 1. 170 questions, 140 scored total
  • 2. 110 closed-book, 60 open-book
  • 3. 7.5-hour exam day, 45-min lunch
  • 4. Pass score: 400 of 500
  • 5. Use the higher LT/ST rate
  • 6. Remaining life = actual minus required
  • 7. Class 1 interval: 5 and 5
  • 8. Class 3 interval: 10 and 10
  • 9. Injection points: 3-year thickness max
  • 10. MAWP recalc uses 2x corrosion loss
  • 11. PQR proves procedure; WPQ proves welder
  • 12. Open-book allows only effectivity-sheet documents

API-570

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