Category
Cryogenic & Refrigerated Storage
Subcategory
LNG
Applicable standards
5
Issuing bodies
4
Description
Double-containment LNG tank — primary inner tank with secondary steel/concrete bund (no vapor containment).
Applicable Standards (5)
API — 2 standards
API 625
Tank Systems for Refrigerated Liquefied Gas Storage
Single-, double- and full-containment refrigerated tank systems for LNG, LPG, ethylene, ammonia, butadiene, etc. Integrates inner tank, outer tank, foundation, insulation, vapor barrier, and ancillaries.
Key requirements (10)
- Tank systems for refrigerated liquefied gases — covers full / double / single containment.
- Inner tank materials: 9 % Ni steel (ASTM A553) for cryo (LNG, ethylene); SS for very low temp; CS for warmer (NH3, LPG).
- Outer tank: prestressed concrete (full containment) or steel (single/double).
- Insulation in annulus: perlite (loose-fill), cellular glass, PIR foam, depending on system.
- Vapor barrier mandatory for refrigerated systems to prevent atmospheric moisture ingress.
- Heated foundation required for cryogenic service to prevent ground frost heave.
- In-tank submerged pumps mandatory — no bottom or side connections below liquid level.
- Boil-Off Gas (BOG) management: vapor return, BOG compressor, recondenser typical.
- Roof: suspended deck (full containment) with insulation above.
- References API 620 Annex Q/R for inner tank design rules.
Note: Primary US/Global standard for cryogenic and refrigerated bulk storage tanks.
API 620
Design and Construction of Large, Welded, Low-Pressure Storage Tanks
Atmospheric and low-pressure (≤15 psig) welded storage tanks. Annex Q covers refrigerated LNG/LPG; Annex R covers low-pressure refrigerated storage.
Key requirements (7)
- Low-pressure tanks: pressures > 2.5 psig up to 15 psig (≈ 1 barg).
- Design temperatures: ambient down to –50 °F (–46 °C) by default; Annex Q to –270 °F (–168 °C); Annex R for refrigerated.
- Annex Q: refrigerated LNG, ethylene with 9 % Ni or stainless inner shell.
- Annex R: low-pressure refrigerated storage of LPG, NH3, etc.
- Stress allowable: ≤ 1/3 UTS or 5/12 yield (lower governs).
- Joint efficiency E: 1.0 with full RT for primary stress areas.
- Hydrotest: pneumatic + hydrostatic combination commonly used.
NFPA — 1 standard
NFPA 59A
Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG)
Onshore LNG facilities — production, storage, vaporization, transfer.
Key requirements (7)
- US standard for production, storage and handling of LNG.
- Spacing requirements: tank-to-tank and tank-to-property line based on thermal radiation contours.
- Spill containment: impoundment area sized for 110 % of largest tank, or full containment design.
- Vapor dispersion analysis required for siting (using LNG fire / spill radiation).
- Refers to API 620, API 625, ASME B31.5 for design.
- Fire protection: fixed water spray, dry chemical, high-expansion foam.
- Adopted by 49 CFR 193 in the US.
EN/CEN — 1 standard
EN 14620 (series)
Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases
Single, double and full containment refrigerated tanks for LNG, ethylene, LPG, ammonia. Operating between −165 °C and 0 °C.
Key requirements (7)
- European standard for site-built vertical cylindrical flat-bottomed steel tanks for refrigerated liquefied gases (–165 °C to 0 °C).
- 5 parts: General, Metallic, Concrete, Insulation components, Testing/commissioning.
- Containment categories: single, double, full, membrane.
- Inner tank materials: 9 % Ni (X8Ni9), austenitic SS, aluminum alloys depending on temperature.
- Annular space insulation: perlite + resilient blanket; required vapor seal at outer wall.
- Acceptance: hydrotest + pneumatic + cool-down + commissioning.
- Counterpart to API 625 in European market; widely cited globally for LNG storage.
Note: Primary European cryogenic site-built tank standard; widely referenced globally.
BSI — 1 standard
BS 7777 (legacy)
Flat-bottomed, vertical, cylindrical storage tanks for low temperature service
British cryogenic tank code; still referenced on legacy LNG/LPG/ammonia projects.
Key requirements (5)
- British 4-part standard for above-ground vertical flat-bottomed cylindrical tanks for low-temp refrigerated service.
- Part 1: Guide; Part 2: Design (metallic); Part 3: Concrete components; Part 4: Insulation.
- Pre-dates EN 14620; still cited for LNG, ethylene, propane storage in UK / Middle East.
- Temperature scope: down to –165 °C (LNG).
- Defines single, double, full containment with similar criteria to API 625 / EN 14620.