API 579 Part 13 Lamination Assessment Screening

API 579 Part 13 Lamination Assessment is used when UT scanning identifies laminations, planar separations, or embedded discontinuities in plate material that may affect structural integrity. Laminations can reduce effective load-carrying capacity or raise concern near welds, seams, nozzles, or other stress-concentrated locations, so acceptability depends on size, location, and orientation—not thickness averages alone.

Use this screening workflow to confirm Part 13 applicability and whether your inspection dataset is sufficient to support a defensible decision. If the screening indicates concern, the next step is a formal Part 13 Fitness-for-Service (FFS) evaluation to determine acceptability and define practical integrity actions for continued operation.

Use the screening questions below to determine whether a formal Part 13 evaluation is recommended.

API 579 Part 13 — Lamination Assessment Screening (Workflow)

Instruction: Answer all questions, then click “Check if FFS is needed”.

Note: Use N/A only when the question truly does not apply (e.g., no welds nearby, no supplemental loads, no external pressure).

1) Has inspection identified one or more planar lamination indications in the pressure boundary material?
For example; an in-service UT scan shows a planar reflector parallel to the plate surface on a shell course, reported as a “lamination-like indication.”
2) Is there any observed surface bulging (ID or OD) associated with the indication that would cause it to be categorized as a blister (not a lamination-only case)?
For example; an OD “pillow”/bulge is visible or confirmed by profile checks near the UT indication → treat as blister per Part 7, not Part 13.
3) Is the component currently in hydrogen charging service (or a service that can drive hydrogen damage progression) such that laminations must be evaluated using Part 7?
For example; a wet H2S / sour water environment with hydrogen charging risk and history of hydrogen damage mechanisms → Part 13 directs evaluation using Part 7.
4) Is there a through-wall linear indication or evidence that the lamination must be treated as a crack-like flaw (per Part 13 direction to Part 9)?
For example; a connected linear UT indication suggests through-thickness cracking or a planar flaw extending toward a surface → evaluate as crack-like flaw per Part 9 when directed by Level 1/2 steps.
5) Was the component originally designed/constructed to a recognized code/standard (required for Level 1/2 applicability)?
For example; ASME VIII vessel, API 650 tank, or recognized piping code basis documented in equipment files.
6) Is the material considered to have sufficient toughness for the operating conditions (no unresolved brittle fracture concern)?
For example; unknown CVN / unknown MDMT margins at cold start-up → route to Part 3 brittle fracture assessment instead of relying on Level 1/2 lamination screening.
7) Is the component subject to embrittlement during operation due to temperature/process environment such that a Level 3 assessment should be performed?
For example; a service known for embrittlement risk where a simple screening is not appropriate → go directly to Level 3.
8) Is the component NOT in cyclic service (or, if cyclic, do adjacent laminations remain on the same plane and show no through-thickness cracking so Level 1/2 can still apply)?
For example; repeated pressure/temperature cycles from frequent start-ups/shut-downs with uncertain lamination stability → trigger more detailed evaluation.
9) For Level 1 screening, is the lamination in a Type A component subject to internal pressure (Level 1 limit)?
For example; a typical cylindrical shell course under internal pressure → Type A case fits Level 1 scope.
10) For Level 2 screening, is the component either Type A or Type B Class 1, and are the applied loads limited to internal pressure, supplemental loads, or a combination (Level 2 scope)?
For example; internal pressure + nozzle loads/wind/seismic considered as supplemental loads → Level 2 scope is appropriate.
11) Was the lamination detected/defined using an inspection method suitable for through-thickness location and remaining thickness (e.g., UT that can size depth and remaining plate thickness)?
For example; UT reports both lamination depth and the minimum measured thickness at the lamination location.
12) Have the lamination plan dimensions been recorded (length/width or equivalent “s” and “c”), with a clear sketch showing orientation?
For example; the UT map defines an ellipse/rectangle footprint (e.g., 4.5 in × 3.25 in) and shows its orientation relative to the vessel axis/circumference.
13) Have you recorded the through-thickness position/height of the lamination (and any “ligament” to the nearest surface) so surface-breaking checks can be made?
For example; lamination is mid-wall with a defined distance to OD/ID, enabling a surface-breaking determination check.
14) Has the minimum measured thickness at/near the lamination location been recorded (for remaining-section thickness calculations)?
For example; UT thickness readings around the lamination show a minimum measured thickness used for conservatism.
15) If multiple laminations exist, have you measured edge-to-edge spacing to the nearest lamination (to decide “separate vs combine” and to detect closely spaced laminations at different depths)?
For example; two laminations on the same plane are far apart (evaluate separately) vs. close enough that they must be combined into one larger footprint for assessment.
16) Have you measured and recorded the distance from the lamination to the nearest weld seam, using the Part 13 definition of “at a weld seam” for screening?
For example; the lamination lies within 1 inch (25 mm) or 2× plate thickness (whichever is greater) from the weld edge → treat as “at a weld seam,” with elevated concern for through-wall cracking and in-service monitoring need.
17) Have you measured and documented spacing from the lamination to the nearest major structural discontinuity (nozzle, transition, stiffener, shell change, etc.)?
For example; lamination is near a nozzle reinforcement pad or a shell transition → you must capture that distance because bending/local stresses may control acceptability.
18) Has the lamination been examined for cracks extending from the lamination plane in the through-thickness direction (lamination cracking)?
For example; angle beam UT / advanced UT checks confirm whether any cracks are propagating away from the lamination plane toward ID/OD.
19) Are there multiple laminations at different depths through the wall that are closely spaced such that they should be treated as equivalent HIC damage (per Part 13 direction) rather than lamination-only evaluation?
For example; UT shows “stacked” laminations at multiple depths within the same footprint region → evaluate as equivalent HIC per Part 7 per Part 13 direction.
20) Is the lamination sufficiently far from localized bending stress sources / major discontinuities so the Level 1/2 proximity screening is not automatically failed?
For example; the lamination is in a “clean shell bay” away from nozzles, supports, knuckles, transitions, or stiffeners → screening is more likely to be valid.
21) Has the lamination been confirmed NOT surface-breaking (i.e., adequate ligament to ID/OD for the screening assumptions)?
For example; the lamination is embedded with measurable remaining metal to the nearest surface and is not connected to surface indications.
22) If the lamination is at/near a weld seam, has the site committed to an in-service monitoring plan focused on lamination cracking while in service?
For example; lamination is close to an un-PWHT seam weld; you plan periodic UT rechecks for any through-thickness cracking initiation/growth at the lamination boundary.
23) Does the component experience external pressure or other loads producing compressive stresses where full-thickness continuity is important to avoid loss of buckling strength?
For example; vacuum/external pressure or local compression from supports results in compressive shell stresses → Level 3 detailed evaluation is typically needed.
24) Are geometry/loading conditions complex enough that a detailed stress analysis is needed (i.e., Level 3 intended use)?
For example; nearby nozzles, skirt/support interactions, discontinuity bending, or combined loads where local stress distribution must be quantified → Level 3.
25) Do you need a documented acceptability decision for continued operation at current conditions (and, if needed, operating limits / rerate / repair actions) for the lamination condition?
For example; inspection found laminations in multiple shell locations and you must document run/repair/rerate decisions for management and inspection planning.
26) Is a remaining life evaluation needed (typically only if compressive/bending stresses or cyclic loads could drive growth/instability)?
For example; lamination is in a region with compression/bending or the component is in cyclic service → remaining life may be required.
27) If acceptance criteria are NOT met (or will not be met at required conditions), are you prepared to consider rerate/repair/replace or proceed to Level 3?
For example; screening fails near a discontinuity → either rerate, repair/replace, or run Level 3 detailed stress analysis.
28) If the lamination is in a service that may lead to growth (including hydrogen charging or other growth-driving conditions), do you have a monitoring plan to detect growth or through-wall cracking?
For example; you will repeat UT mapping at a defined interval; if growth/cracks are detected, you will re-evaluate the lamination.
29) Will you document and retain the lamination location, size, spacing, and condition along with the assessment results (so future monitoring compares “apples-to-apples”)?
For example; you keep a table/data-sheet per lamination with footprint, thickness, spacing to welds/discontinuities, and cracking observations.
30) If monitoring is required, will you document growth comparisons over time (baseline vs follow-up size/condition) so re-evaluation is objective?
For example; each re-inspection records updated footprint, depth/ligament, and any new cracking, with direct comparison to the baseline record.
Answer all questions, then click “Check if FFS is needed”.

When to Use API 579 Part 13

API 579 Part 13 is typically used when the controlling concern is lamination-type indications in plate material and the decision depends on their dimensions and location. Common triggers include:

  • UT scanning identifies laminations, planar separations, or embedded discontinuities in the pressure boundary
  • Laminations are near seam welds, nozzle regions, attachments, or other discontinuities where local stress is elevated
  • There is concern for interaction with welds, repairs, or future modifications (hot work)
  • A decision is needed on continued operation as-is versus repair/replace at a planned outage
  • The inspection needs a structured acceptability basis rather than a “monitor only” judgment

If the primary concern is a crack-like flaw (planar flaw acceptability at a weld or HAZ), route the evaluation to API 579 Part 9.

What to Gather if Screening Indicates FFS Is Needed

If this workflow indicates that a formal API 579 Part 13 assessment is recommended, prepare the following to support a defensible evaluation:

  • UT scan outputs and sizing results (length, width, depth/through-wall position if available)
  • Location and orientation details (distance to welds/seams/nozzles/attachments, internal vs external surface relevance)
  • Component details (thickness, diameter/geometry, drawings if available)
  • Operating basis (pressure, temperature, service description)
  • Inspection method and coverage details (scan technique, resolution, and confidence in sizing)
  • Any repair/modification plans that could affect acceptance (weld repair, nozzle addition, hot work proximity)

Request an API 579 Part 13 Lamination Assessment (FFS)

If this workflow indicates that an API 579 Part 13 Lamination Fitness-for-Service (FFS) assessment is needed, the next step is a decision-ready engineering evaluation using your UT findings, equipment details, and operating conditions.

Inspection 4 Industry LLC (I4I) performs API 579-1 / ASME FFS-1 Part 13 assessments and delivers a complete report package stating fit-for-service or not fit-for-service, any required operating restrictions or rerated limits when applicable, and practical integrity actions—repair now, repair at turnaround, replace affected components when required, or monitor and run with a defined inspection plan aligned to the controlling lamination condition.

To proceed, send your UT scan data and lamination sizing/location details (length, width, depth/through-wall position if available), proximity to welds/nozzles/seams, and your operating basis, and request an API 579 Part 13 Lamination Assessment (FFS).

 

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