Category
Cryogenic & Refrigerated Storage
Subcategory
LPG
Applicable standards
7
Issuing bodies
4
Description
Spherical pressurized LPG / butadiene / propylene storage vessel.
Applicable Standards (7)
ASME — 2 standards
ASME BPVC Sec VIII Div 1
Rules for Construction of Pressure Vessels
Mandatory rules for design, fabrication, inspection, testing and certification of pressure vessels operating above 15 psig (~1 barg).
Key requirements (12)
- Applies to vessels with internal pressure > 15 psig (1.03 barg) up to ~3000 psi (Div 1 sweet spot).
- Joint efficiency E: 1.0 (full radiography), 0.85 (spot RT), 0.70 (no RT) for Type 1 butt joints.
- Shell thickness: t = P·R/(S·E – 0.6·P) for circumferential stress (UG-27).
- Head thickness: t = P·D/(2·S·E – 0.2·P) for 2:1 ellipsoidal heads (UG-32).
- Hydrostatic test pressure: 1.3 × MAWP × (S_test/S_design) — UG-99.
- Pneumatic test (when hydro impractical): 1.1 × MAWP — UG-100.
- Corrosion allowance is added to calculated thickness (not included in S formula).
- MDMT and impact testing per UCS-66 / Figure UCS-66; below the curve, Charpy V-notch impacts are required.
- PWHT thresholds per UCS-56 — generally required above 19 mm thickness for P-No. 1 carbon steels.
- Nozzle reinforcement: area replacement method (UG-37) within reinforcement zone.
- Maximum allowable stress S: from ASME II Part D, Table 1A/1B/3 — temperature dependent.
- Flanges per ASME VIII-1 Appendix 2 (or B16.5 for standard sizes).
Note: Most widely used pressure vessel code worldwide.
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.
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.
NFPA — 1 standard
NFPA 58
Liquefied Petroleum Gas Code
LP-Gas storage, handling, transport in the US.
BIS — 2 standards
IS 2825 (legacy)
Code for Unfired Pressure Vessels
Legacy Indian pressure vessel code; many existing plants still reference it.
Key requirements (7)
- Indian Code for Unfired Pressure Vessels — generally aligned with ASME VIII Div 1.
- Three classes (1, 2, 3) corresponding to severity of service.
- Joint efficiency 1.0 (full RT), 0.85 (spot), 0.7 (no RT).
- Hydrotest: 1.3 × design pressure × (allowable at test/allowable at design).
- Material allowables drawn from Indian + ASME-equivalent grades.
- Used in conjunction with SMPV(U) Rules for statutory approval in India.
- Increasingly being superseded in industry by ASME VIII direct adoption.
IS 6044 (Parts 1 & 2)
Code of Practice for LPG Storage Installations
Indian LPG storage facilities — pressurized and refrigerated.
Key requirements (4)
- Indian code for LPG storage installations — Part 1 (above-ground pressurized) and Part 2 (refrigerated).
- Covers spacing, fire protection, vent stack height, instrumentation.
- Aligned with NFPA 58 in approach but with Indian PESO statutory framework.
- Mandatory deluge water spray, gas detection, automatic ROV on inlet/outlet lines.