Mechanical reviews where
PWHT and sour service can’t be guessed.
Owner’s-engineer AI reviews for oil & gas deliverables — traceable findings, comment registers and human-supervised escalation in hours. Mechanical discipline is where missed PWHT requirements, under-specified sour service materials, and incomplete weld maps create late-stage rework. We find them at IFR.
The PWHT trigger that gets missed at IFR.
PWHT requirements triggered by material P-Number and wall thickness are missed most often when the weld map is issued as a generic template rather than a deliverable-specific document. The material is correct; the heat treatment annotation is absent.
PWHT missing on P-No 5A material above 19 mm wall thickness
What runs, in what order.
Mechanical checks run across equipment datasheets, vessel design calculations, weld maps, and material certificates in a fixed sequence. Prerequisite data checks first. Code-compliance checks second. Cross-document consistency last.
Pressure vessel design margin
ASME BPVC VIII-1 UG-27Verify that the design pressure and temperature shown on the datasheet are correctly propagated into the shell/head thickness calculations. Confirm the allowable stress value S corresponds to the correct material at design temperature from ASME Section II Part D.
MAWP vs. design pressure
ASME BPVC VIII-1 UG-98Confirm MAWP stamped on nameplate is not less than design pressure. Where MAWP > design pressure by more than 10%, flag for review — may indicate conservative over-design or an incorrect design pressure.
Nozzle reinforcement
ASME BPVC VIII-1 UG-36 to UG-45For every nozzle on the vessel, confirm that nozzle reinforcement area satisfies UG-37 area-replacement requirements or that a reinforcing pad is specified and dimensioned.
Test pressure derivation
ASME BPVC VIII-1 UG-99Confirm hydrostatic test pressure = 1.3 × MAWP × (stress ratio at test temp / stress ratio at design temp). Flag where test pressure is stated as 1.5 × design pressure without the stress-ratio correction.
PWHT triggers — material and thickness
ASME B31.3 Table 331.1.1 / ASME BPVC VIII-1 UCS-56Identify P-Number material groups on weld maps and datasheets. For each combination of P-Number and wall thickness, check against mandatory PWHT tables. Flag where PWHT is required but not annotated.
Sour service material qualification
NACE MR0175 / ISO 15156 Part 2 §7For equipment in defined H₂S service (partial pressure ≥ 0.0003 MPa absolute), confirm all pressure-containing materials are from qualified groups per ISO 15156 Table A.2 (carbon and low-alloy steels). Flag unqualified grades.
Hardness limits — sour service
NACE MR0175 / ISO 15156 Part 2 §7.3For sour service welds, confirm maximum hardness limit (typically 22 HRC / 250 HV) is specified in the WPS and material requisition. Flag where hardness requirement is absent from welding procedure.
Weld map completeness
ASME BPVC VIII-1 UW-11Confirm weld map includes: joint type, weld category, examination type (RT/UT/PT/MT), PWHT flag, and WPS reference for every seam. Flag incomplete weld maps where joints are unnumbered or examination type is blank.
Inspection category
ASME BPVC VIII-1 UW-11 / API 510For vessels in lethal, high-pressure, or sour service, confirm full radiographic examination (RT-1 or UT-1 equivalent) is specified. Flag where spot RT (RT-3) is specified for service that demands full RT.
What SpecSense flags in mechanical reviews.
PWHT not annotated — P-No 5A material, 22 mm wall thickness on ISO-089
Weld map WM-V-3101 Rev A: 1.25Cr-0.5Mo spool, 22 mm wall, no PWHT annotation. Mandatory above 19 mm for P-No 5A. Non-conforming if hydrotested without PWHT.
Unqualified material specified for sour service — ASTM A516 Gr 70 not listed in ISO 15156 Table A.2 without qualification
Vessel V-4401 in H₂S service (0.001 MPa partial pressure). Shell material ASTM A516 Gr 70 is acceptable only with hardness ≤ 22 HRC and CE ≤ 0.43. Neither limit is stated in material requisition MR-V-4401.
Test pressure — stress-ratio correction not applied; stated value is 1.5 × design pressure
V-3210 datasheet: test pressure stated as 1.5 × 42 bar = 63 bar. Correct derivation: 1.3 × MAWP × (S_test / S_design) = 1.3 × 45 × (138/131) = 61.6 bar. Overstated test pressure by 2.3%; hydrostatic load case should be rechecked.
Nozzle N7 — reinforcing pad dimensions not specified on vessel drawing
V-2101 nozzle N7: 6" NPS process outlet. Drawing notes indicate reinforcing pad required but dimensions (OD, thickness, material) are blank on Rev B. Fabrication cannot proceed without this data.
Weld map — 14 joints unnumbered, examination type blank on sour-service vessel
V-4401 weld map Rev A: 14 of 31 weld joints have no joint number, no examination type, and no WPS reference. Vessel in confirmed sour service. Full RT required per UW-11(a) for lethal/sour; cannot confirm from current map.
Hardness limit omitted from WPS for sour-service welds on V-4401
Welding Procedure Specification WPS-047 Rev 2: no maximum hardness limit stated. For H₂S service, ISO 15156 Part 2 requires ≤ 22 HRC (250 HV). WPS must be revised before fabrication.
MAWP exceeds design pressure by 22% — basis for overage not documented
V-2201: design pressure 40 bar, MAWP stamped as 49 bar (22% above design). No engineering note in calculation package explaining basis for MAWP uplift. Should be confirmed or MAWP corrected to match design basis.
What we check against.
ASME BPVC VIII-1
Rules for construction of pressure vessels — Division 1
ASME BPVC VIII-2
Alternative rules — design by analysis
ASME B31.3
Process piping — materials, fabrication, PWHT
ASME Section II Part D
Material allowable stresses vs. temperature
NACE MR0175 / ISO 15156
Materials for H₂S-containing environments
API 510
Pressure vessel inspection code
API 579-1 / ASME FFS-1
Fitness-for-service assessment
ASME Section IX
Welding, brazing, and fusing qualifications
ASTM A370
Mechanical testing of steel products — hardness
EN 13445
Unfired pressure vessels (European projects)
PD 5500
Specification for unfired fusion welded pressure vessels (UK)
API 660
Shell-and-tube heat exchangers — mechanical design
Sour service — NACE MR0175
H₂S environments demand material selection, not just material choice.
NACE MR0175 / ISO 15156 sets the material qualification requirements for equipment in H₂S-containing environments. SpecSense checks that every equipment item and pressure-containing component in a defined sour service is specified from a qualified material group, that hardness limits are called out in the material requisition, and that any welding procedure specifies post-weld hardness testing. This is the check that EPC discipline leads most frequently defer until Vendor Data Review — by which point rework cost is significant.
What we do not replace.
SpecSense checks mechanical deliverables against code requirements, material specifications, and weld map completeness. It does not perform finite element analysis, design-by-analysis per ASME BPVC VIII-2, or independent pressure vessel re-rating. It catches the systematic compliance checks — PWHT triggers, sour-service material qualification, design margin derivation — so your mechanical lead spends their time on the engineering judgements that demand it, not the checklist.
Ready to run mechanical through SpecSense?
Drop an equipment datasheet, vessel design calc, or weld map. 48-hour supervised pilot. Chartered-engineer sign-off.