Calculations & Intervals
Not publishedof exam
Corrosion RateRemaining LifeInspection IntervalMAWP RecalcWeld Joint FactorHydro Test
Welding Procedure Review
Not publishedof exam
WPS ReviewPQR ReviewWPQ ReviewEssential VariablesP-NumbersRP 577
Nondestructive Examination
Not publishedof exam
RTPTMTVTUT ThicknessLeak Testing
Practical Knowledge General
Not publishedof exam
CML PlacementCircuitizationDeadleg InspectionInjection PointsSmall Bore PipingRecords
Practical Knowledge Specific
Not publishedof exam
Damage MechanismsRP 574 ComponentsRP 576 PRDsRP 578 PMIPCC-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
Compare LT and ST rates; always use the faster
LT: long baseline trendST: recent short trendGoverning: pick higher rate
LT vs ST Corrosion Rate
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
- 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
- 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
Class 1 tightest, Class 4 loosest inspection interval
Class 1: 5 and 5Class 2: 10 and 5Class 3: 10 and 10Class 4: optional both
Point-to-Point vs Circuit Method
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)
- 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
- 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
- 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
WPS is how; PQR proves it; WPQ certifies welder
WPS: written instructionsPQR: procedure test recordWPQ: welder skill proof
PQR vs WPQ
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
- 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
- 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
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
- 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
PT and MT see surface; RT and UT see inside
PT/MT: surface onlyRT/UT: internal volumeVT: overall visual condition
RT vs UT
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
- 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
- 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
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
- 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
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
- 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
- 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
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
- 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
- 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
Amine, caustic, and chloride all cause stress cracking
SCC group: amine, caustic, chlorideCorrosion group: CUI, sulfidation, MICMechanical: fatigue and erosion
Sulfidation vs Sour Water Corrosion
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)
- 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)
- 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
- 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
- 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
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