Category
Pressure Vessels & Reactors
Subcategory
Pressure Vessel
Applicable standards
7
Issuing bodies
3
Description
Pressure vessel using more rigorous Div 2 analysis — used for high pressure / large size / cyclic duty.
Applicable Standards (7)
API — 2 standards
API 579-1 / ASME FFS-1
Fitness-for-Service
Quantitative engineering assessment of equipment with flaws (corrosion, cracks, dents, blisters, fire damage, creep, etc.) for continued service.
Key requirements (7)
- Fitness-For-Service standard, jointly with ASME (FFS-1).
- Three assessment levels: 1 (screening), 2 (detailed analytical), 3 (advanced FEA / fracture mechanics).
- Part 4: General metal loss; Part 5: Local metal loss; Part 6: Pitting.
- Part 7: HIC and SOHIC; Part 8: Weld misalignment; Part 9: Crack-like flaws.
- Part 10: Creep; Part 11: Fire damage; Part 12: Dents and gouges; Part 13: Laminations.
- RSF (Remaining Strength Factor) method for general metal loss; RSF ≥ 0.90 typical screening.
- Companion to API 510, 570, 653 for repair-vs-replace decisions.
API 582
Welding Guidelines for the Chemical, Oil, and Gas Industries
Supplementary welding requirements (PWHT, hardness, impact, NDE) beyond ASME IX.
Key requirements (7)
- Supplementary welding requirements for chemical/oil/gas industries — beyond ASME IX.
- Mandatory PWHT thresholds tighter than ASME VIII.
- Hardness limits: 200 HB (CS), 235 HB (1.25Cr-0.5Mo / 2.25Cr-1Mo) for sour service typical.
- Charpy impact requirements at MDMT for all weldments where production weld is impact-tested.
- PMI (positive material identification) required on alloy components.
- Hydrogen-induced cracking (HIC) prevention: low-hydrogen consumables, preheat, controlled diffusible H ≤ 8 mL/100g.
- Heat input control for impact-toughness-controlled materials.
ASME — 3 standards
ASME BPVC Sec VIII Div 2
Alternative Rules for Construction of Pressure Vessels
More rigorous design-by-analysis rules; permits higher allowable stresses and thinner walls.
Key requirements (8)
- Alternative rules — Design by Analysis or Design by Rules (Part 5 vs Part 4).
- Higher allowable stress factor (typically 2/3 of yield, vs 3.5:1 ratio in Div 1) — thinner walls possible.
- Mandatory user's design specification (UDS) certified by registered engineer.
- Mandatory full radiography of butt welds (with limited exceptions).
- Hydrostatic test: 1.25 × MAWP × stress ratio.
- Fatigue analysis required when cyclic conditions are significant (Part 5 screening).
- Class 1 vs Class 2 design — Class 2 allows higher stresses with stricter NDE/inspection.
- Used for high pressure (>3000 psi typical), large vessels, cyclic service, lethal service.
ASME BPVC Sec II
Materials (Parts A, B, C, D)
Material specifications (mostly identical to ASTM with SA prefix), filler metals, properties and allowable stresses.
ASME BPVC Sec IX
Welding, Brazing and Fusing Qualifications
Welding/brazing procedure and welder/operator qualification.
Key requirements (8)
- Welding and brazing qualifications.
- WPS (Welding Procedure Spec) supported by PQR (Procedure Qualification Record).
- PQR essential variables include: P-number, F-number, A-number, thickness range, position, preheat, PWHT, impact.
- Welder/operator qualification: bend tests OR radiography per QW-302.
- Coupon thickness qualifies a range: Table QW-451 (e.g., 25 mm coupon qualifies 5–50 mm).
- Position qualification: 6G qualifies all positions for pipe.
- Performance qualification expires if 6 months without welding (re-qualify).
- Notch toughness essentials when impact required by construction code.
ASTM — 2 standards
ASTM A516 / A516M
Pressure Vessel Plates, Carbon Steel, for Moderate- and Lower-Temperature Service
Most-used carbon steel plate for pressure vessel shells (Gr 60, 65, 70).
ASTM A537 / A537M
Pressure Vessel Plates, Heat-Treated, Carbon-Manganese-Silicon Steel
Heat-treated higher-strength carbon-mangan-silicon plate for PV.