Overview
EN ISO 8311:2013 - titled "Refrigerated hydrocarbon and non‑petroleum based liquefied gaseous fuels - Calibration of membrane tanks and independent prismatic tanks in ships - Manual and internal electro‑optical distance‑ranging methods" - is the CEN‑endorsed adoption of ISO 8311:2013. The standard specifies internal measurement methods for shipboard membrane tanks used to transport refrigerated light hydrocarbons (LNG, LPG) and, with some modification, for independent prismatic tanks. It defines procedures for producing tank capacity tables and correction tables that are used to compute cargo quantities for custody transfer, inventory and operational control.
Key Topics
- Scope and applicability: Internal calibration of membrane tanks and modified application to prismatic tanks for refrigerated hydrocarbon and non‑petroleum liquefied gaseous fuels.
- Measurement methods: Two primary approaches - manual measurement and internal electro‑optical distance‑ranging (EODR).
- Measurement elements covered:
- Determination of measuring points (length, width, height).
- Bottom undulation and gauge reference height.
- Tank geometry measurements and gauge locations.
- Precautions for tank condition, membrane integrity and onboard safety during calibration.
- Calculation procedures:
- Derivation of tank capacity (volume vs. liquid level) tables.
- Correction tables for trim and list and for shell thermal expansion/contraction.
- Treatment of deadwood and chamfer areas.
- Quality and uncertainty: Annex on uncertainty associated with tank calibration and examples of capacity and correction tables (informative annexes).
- Reporting and maintenance: Guidance on calibration reporting, table formats and periodic recalibration.
Applications
- Custody transfer and commercial transactions where accurate cargo quantity is critical (LNG/LPG carriers).
- Ship operators and cargo planners for inventory control, voyage planning and stability calculations.
- Classification societies, surveyors and metrology teams that perform tank calibration and certification.
- Shipyards and naval architects validating tank geometry during construction or retrofit.
- Regulatory compliance and safety inspections, ensuring measurement methods meet international best practice.
Who Should Use This Standard
- Calibration surveyors and maritime metrology laboratories
- Shipowners and operators of refrigerated hydrocarbon carriers
- Classification societies and port state control inspectors
- Naval architects, shipyards and equipment manufacturers
- Commodity traders and operations teams involved in custody transfer
Related Standards
- Developed by ISO/TC 28 (Subcommittee SC5) and adopted by CEN as EN ISO 8311:2013. It supersedes earlier editions and is part of the suite of standards addressing measurement and custody transfer of refrigerated liquefied gaseous fuels.
Keywords: EN ISO 8311:2013, tank calibration, membrane tanks, prismatic tanks, EODR, LNG, LPG, tank capacity table, trim correction, list correction, ship tank calibration.
