Overview - ISO 8311:2013 (tank calibration for refrigerated gases)
ISO 8311:2013 specifies methods for the internal measurement and calibration of membrane tanks used in ships transporting refrigerated light hydrocarbons (LNG, LPG) and other non‑petroleum liquefied gaseous fuels. The standard defines both manual and internal electro‑optical distance‑ranging (EODR) measurement approaches and sets out the calculation procedures for producing tank capacity tables and correction tables used to compute cargo quantities. With some modification, the procedures can be applied to independent prismatic tanks.
Key topics and technical requirements
- Scope and applicability: Calibration of membrane tanks; adaptable for independent prismatic tanks.
- Measurement methods: Manual methods (tape/hand‑held laser) using membrane scaffolding, and internal EODR methods for slope distance, vertical and horizontal angles.
- Measuring points and geometry: Determination of measuring points across section planes and longitudinal planes; measurement of tank length, width, height, and bottom undulation.
- Data processing and tables: Calculation procedures for tank capacity (partial fill volumes), trim and list correction tables, and combined corrections for custody transfer accuracy.
- Corrections and conditions: Compensation for temperature, tank shell expansion/contraction, deadwood, and changes in ship attitude (trim/list).
- Safety and precautions: Requirements for safe access, membrane condition checks, and explosive‑atmosphere considerations during internal surveys.
- Uncertainty and documentation: Annex on measurement uncertainty, examples of capacity, trim and list tables, and guidance on recalibration intervals and reporting.
Practical applications and users
ISO 8311:2013 is used to ensure accurate cargo volume measurement and custody transfer of refrigerated gaseous fuels on tankers and LNG/LPG carriers. Typical users include:
- Shipbuilders and tank designers validating tank geometry
- Marine surveyors and calibration technicians performing tank surveys
- Terminal and shipping operators managing cargo quantity control
- Naval architects and ship operators applying trim/list corrections
- Regulatory bodies and classification societies reviewing calibration records
Practical outcomes: accurate tank calibration, reliable tank capacity tables, standardized correction tables for cargo quantity computation, and traceable measurement uncertainty for custody transfer.
Related standards
Keywords: ISO 8311:2013, tank calibration, membrane tanks, EODR, refrigerated hydrocarbon fuels, LNG, LPG, ship tank calibration, tank capacity table, trim and list corrections, measurement uncertainty.