API 579 Part 10 Creep Assessment Screening

API 579 Part 10 Creep Assessment is used when equipment operates in the creep temperature range and integrity becomes a time-dependent remaining-life problem. Unlike corrosion, creep damage develops under sustained elevated temperature and stress, so the controlling decision is often whether the component has sufficient remaining life to safely reach the next planned run length or turnaround.

Use this screening workflow to confirm Part 10 applicability and whether your available operating history and inspection data are sufficient to support a defensible evaluation. In many cases, a formal Part 10 assessment is needed to estimate remaining life, identify controlling locations, and define operating limits or repair timing when creep governs integrity.

Use the screening questions below to determine whether a formal Part 10 evaluation is recommended.

API 579 Part 10 — Creep Range Questionnaire (Comprehensive)

Instruction: Answer all questions (Yes / No / N/A), then click “Evaluate Part 10 Path”.

This tool helps (1) confirm Part 10 relevance, (2) check readiness for Level 1 vs Level 2/3, and (3) identify which Part 10 remaining-life category applies (rupture / creep-fatigue / crack growth / buckling / DMW / microstructural).

A) Part 10 Relevance — Are you truly in the creep regime?

P10-1) Is the component exposed to elevated metal temperatures where time-dependent deformation (creep) is credible for the material and service?
Example: furnace tubes, hot reheater piping, hot reactor effluent piping, high-temperature headers, heater transfer line, etc.
P10-2) Is your concern one of these Part 10 outcomes: (a) suitability for continued service at current conditions, and/or (b) remaining life under future planned operation?
Example: “Can we keep running at the same temperature/pressure?” OR “How many hours/years until creep damage reaches allowable?”
P10-3) Are you evaluating remaining life for a component with no crack-like flaw (general creep rupture / creep-fatigue), OR with a crack-like flaw (creep crack growth + FAD limit)?
Example: (No crack-like flaw) general wall thinning / hot spot / creep damage evidence; (Crack-like flaw) UT/PAUT detects a crack-like indication in creep service.

B) Applicability & Limitations (Part 10.2)

P10-4) Do you have (or can you obtain) the material properties needed at the actual temperature and stress conditions?
Example: Level 1 uses material screening curves; Level 2/3 uses material properties (often from Annex 10B) for commonly used materials.
P10-5) Are you aware that Level 1 and Level 2 include a minimum thickness limitation (thin areas may exceed inspection capability), and if not satisfied you should consider Level 3?
Example: localized thinning in a heater tube or hot piping may be too thin to characterize accurately; a Level 3 with validated inspection strategy may be required.
P10-6) Will any total life prediction exceed ~300,000 hours (~35 years), where extrapolation makes predictions increasingly approximate and added NDE/material testing is recommended?
Example: long-term hot piping in steady service since the 1980s; bulk strain may be minimal even if microstructural damage occurs.
P10-7) Are environmental/material interactions in creep service identified and planned to be considered (e.g., carburization, decarburization, hydrogen attack, etc.)?
Example: carburization in furnace service changes effective properties and can affect remaining life; reaction rates may need time-temperature modeling.

C) Data Requirements Readiness (Part 10.3)

P10-8) Do you have original equipment design data and maintenance/operating history adequate to support at least a Level 1 screening?
Example: nameplate/design conditions, thickness, code basis, weld details, plus known operating temperatures/pressures and durations.
P10-9) Can you define an operating history with accurate temperatures, pressures, supplemental loads, and time periods for significant events (startups, normal operation, upsets, shutdowns)?
Example: a histogram/timeline of operating “events” rather than a single average temperature.
P10-10) If the operating history is not accurate, can you develop an approximate history with documented assumptions AND perform a sensitivity analysis to evaluate assumption impact?
Example: use interviews + logs to estimate how often the unit ran at a higher temperature; then test “high vs low” cases to see remaining-life sensitivity.
P10-11) Will you base the history on the actual sequence of operation (not a scrambled/averaged order) for damage accumulation?
Example: the sequence “startup → upset → steady run → shutdown” matters; rearranging can change damage results.
P10-12) Do you have the stress basis required for your intended level: nominal stresses for Level 1, and a stress analysis for Level 2/3?
Example: Level 1 may use code equations for nominal stress; Level 2/3 requires stress analysis methods appropriate to the component and loadings.
P10-13) Can you determine remaining sound wall thickness and the extent of corrosion/erosion on all relevant surfaces?
Example: combine UT grids + hotspot surveys in a heater tube circuit; confirm the “thinnest credible” wall.
P10-14) Have you checked for local operating variations that drive localized damage (hot spots, coolant flow patterns, heater firing condition, etc.)?
Example: tube skin thermocouple pattern indicates a hot band; that region needs focused thickness + creep assessment.
P10-15) Have unusual loading conditions been identified and planned for inclusion (missing/damaged supports, dead weight anomalies, etc.)?
Example: a sagging hot line from degraded supports increases bending stress and accelerates creep damage.
P10-16) Have you defined the allowable creep damage parameter to be used (and if not available for the material, will you default to 0.8 for Level 1 and 1.0 for Level 2 as stated)?
Example: screening may limit accumulated damage more conservatively (Level 1) than Level 2.
P10-17) If future reaction rates (e.g., thickness change driven by environment) are relevant, can you account for them using time-temperature history and a fitted rate form?
Example: model a corrosion/reaction rate versus temperature for future operation when thickness loss continues during creep service.
P10-18) For Level 2/3: will you consider metallurgical factors like grain size, carbon content, and heat treatment condition?
Example: same “grade” can behave differently if heat treatment and grain size differ; this becomes critical for refined life predictions.
P10-19) If evaluating a weldment (Level 2/3), do you have weld-specific inputs (joint geometry, deposit composition, welding process, PWHT, repair history, residual stress effects, misalignment/peaking, creep mismatch, toe stress concentration, inspection records, etc.)?
Example: a dissimilar weld joint or a seam weld with mismatch can shift damage toward the HAZ or weld metal; misalignment increases local stress and reduces life.
P10-20) If a crack-like flaw exists: have you classified whether it is original fabrication vs service-induced (and if unknown, will you treat it as service-induced)?
Example: an embedded indication found now in creep service with uncertain origin is treated conservatively as service-induced.
P10-21) If a crack-like flaw is near a weld: do you know whether it is in HAZ, at fusion line, or in weld deposit, and can you size length/depth/location per Part 9?
Example: record crack location relative to weld; use UT sizing and Part 9 conventions for embedded vs surface-breaking flaws.

D) Level 1 vs Level 2/3 — Which path is realistic?

P10-22) Are you intending Level 1 as a screening check based on original design + past/future planned operation (i.e., “screening criterion”)?
Example: quick screening using nominal stress + screening curves to see whether recorded exposure time is below allowable at given stress/temperature.
P10-23) If Level 1 is not satisfied (or data quality is poor), are you prepared to perform Level 2 or Level 3 with significant input data and stress analysis?
Example: Level 2/3 requires enough fidelity to compute stresses for the damage location and apply remaining life procedures.
P10-24) If minimum thickness limitation is not satisfied for Level 1/2, are you prepared to move to Level 3 with validated inspection results and future inspection frequency based on detailed investigation of applicable damage mechanisms?
Example: very thin localized area → validate NDE sizing and set inspection frequency based on detailed multi-mechanism review.

E) Remaining Life Category — Which Part 10 damage mode governs?

P10-25) Is the primary concern creep rupture life (general creep damage leading to rupture), without needing a crack-growth model?
Example: steady high-temperature service with known stress and temperature; you need “hours/years remaining” to rupture criterion.
P10-26) Is there meaningful cyclic operation at elevated temperature such that creep-fatigue interaction must be evaluated (rather than creep rupture alone)?
Example: frequent startups/shutdowns or temperature swings on hot piping that accumulate fatigue + creep damage together.
P10-27) Does the component contain a crack-like flaw where creep crack growth must be modeled AND Part 9 FAD inputs (including fracture toughness) are needed to place limits (e.g., plastic collapse / possible instability during startup/shutdown)?
Example: a crack-like indication in a weld region of hot piping; creep growth is dominant at high T, but cold/startup portions may still need toughness-based checks.
P10-28) Is creep buckling a credible failure mode (geometry + compressive stresses + time at temperature), requiring buckling-focused remaining-life evaluation?
Example: thin-wall hot components in compression due to constraint/thermal load path; local instability develops over time at temperature.
P10-29) Are you specifically evaluating a ferritic–austenitic dissimilar weld joint (DMW), where Part 10 provides a dedicated creep-fatigue assessment approach?
Example: Cr-Mo ferritic to stainless austenitic weld at high temperature service, with mismatch behavior driving damage localization.
P10-30) Is a microstructural approach needed/desired (especially where long times/low strain make visual deformation unreliable), involving material examination/testing as part of life management?
Example: long-term service where microstructural damage can occur with little bulk strain; add replication/metallography or material testing to support remaining life decisions.

F) Inspection & Sizing Readiness (Part 10.3.7)

P10-31) Will inspection be performed to establish current condition and any detectable damage (baseline for assessment)?
Example: confirm thinning distribution, identify crack-like indications, confirm weld region condition before final life calculation.
P10-32) If crack-like flaw exists: do you have or can you obtain creep crack growth parameters and the additional fracture data needed for the required Part 9 FAD evaluation?
Example: creep crack growth constants + fracture toughness to bound collapse/instability checks that may govern during startup/shutdown.

When to Use API 579 Part 10

API 579 Part 10 is typically used when the controlling degradation mechanism is creep and the decision requires a time-based remaining-life evaluation. Common triggers include:

  • Long-term operation at elevated temperature where creep damage is plausible for the material and service
  • Components in high-temperature circuits such as heater outlet piping, hot headers, or high-temperature vessel internals/shell regions
  • A need to determine whether the equipment can safely operate to the next outage based on remaining life
  • Inspection findings consistent with creep exposure (creep deformation, bulging, local thinning, or damage indicators)
  • A need to define operating limits, inspection scope, or replacement timing when creep controls integrity

If the primary concern is general or localized wall loss at lower temperatures, route the evaluation to Parts 4 or Part 5. If the primary concern is distortion unrelated to creep, route to Part 8.

What to Gather if Screening Indicates FFS Is Needed

If this workflow indicates that a formal API 579 Part 10 assessment is recommended, prepare the following to support a defensible evaluation:

  • Operating history relevant to creep (temperatures, time-at-temperature, excursions, and run history)
  • Equipment/component identification and geometry (thickness, diameter, configuration, and drawings if available)
  • Material identification and relevant records (grade/specification and heat treatment history if available)
  • Inspection results in the suspect locations (thickness, dimensional checks, observations of bulging/strain, and any metallurgical checks if performed)
  • Operating basis for continued service (pressure, temperature, planned run length to next outage)
  • Any prior repairs, replacements, or operating changes affecting high-temperature exposure

Request an API 579 Part 10 Creep Assessment

If this workflow indicates that an API 579 Part 10 Creep Fitness-for-Service (FFS) assessment is needed, the next step is a decision-ready engineering evaluation using your operating history, inspection findings, equipment details, and operating basis.

Inspection 4 Industry LLC (I4I) performs API 579-1 / ASME FFS-1 Part 10 assessments of existing equipment for creep damage and delivers a complete report stating fit-for-service or not fit-for-service, remaining life estimates when applicable, and practical integrity actions—continue with defined monitoring, rerate/limit operation, or schedule repair/replacement at a planned outage.

To proceed, send your operating temperature history, equipment details, inspection results, and your target run/turnaround basis and request an API 579 Part 10 Creep Assessment (FFS).

 

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