ISO 21154:2026

Ships and marine technology — Boil-off-rate measurement method for cargo containment system of LNG ships

This document specifies the principles, conditions, equipment, processes, data acquisition and processing, and test reports of the boil-off-rate (BOR) test for cargo containment systems (CCS) in liquefied natural gas (LNG) ships. It is applicable to the CCS of LNG carriers, LNG floating storage and regassification units (FSRU) and LNG bunkering vessels. It can be used as reference for the fuel containment system (FCS) of LNG fuel ships.

Titre manque

General Information

• Status: Published
• Publication Date: 26-May-2026
• ICS: 47.020.85 - Cargo spaces
• Technical Committee: ISO/TC 8 - Ships and marine technology
• Drafting Committee: ISO/TC 8 - Ships and marine technology
• Current Stage: 6060 - International Standard published
• Start Date: 27-May-2026
• Due Date: 20-Jun-2026
• Completion Date: 27-May-2026

Overview

ISO 21154: Ships and marine technology - Boil-off-rate measurement method for cargo containment system of LNG ships is an international standard developed by ISO (International Organization for Standardization). This standard provides a systematic measurement method for determining the boil-off rate (BOR) in the cargo containment system (CCS) of liquefied natural gas (LNG) ships, floating storage and regasification units (FSRUs), LNG bunkering vessels, and LNG fuel ships. The BOR is a critical indicator in evaluating the efficiency and performance of the CCS, directly impacting operational costs, cargo loss, and greenhouse gas (GHG) emissions. ISO 21154 outlines the principle, equipment, conditions, procedures, data acquisition, processing, and reporting necessities for accurate and repeatable BOR testing at sea.

Key Topics

• Measurement Principle: The standard addresses the approach to assess LNG quantity change over time, utilizing a heat balance system to determine the volume and mass of LNG lost through boil-off under typical operating conditions.
• Measurement Parameters: ISO 21154 specifies essential parameters that must be measured and recorded, including:
  • LNG composition and density
  • Average liquid and vapor temperatures within the CCS
  • Liquid level and volume
  • Vapor pressure in the CCS
  • Insulation system temperature points
  • Ambient air and external water temperatures and pressures
  • Voyage and operational conditions affecting BOR
• Measurement Facility: Requirements are outlined for precise, automated recording of liquid level, temperature, and pressure with defined accuracy tolerances.
• Measurement Procedure: The process consists of three primary phases-before voyage (after loading), during the voyage, and before unloading. Data must be collected consistently and reported in line with the standard's prescribed formats.
• BOR Reporting: The standard mandates a specific format for data recording and BOR calculation, ensuring results are consistent, traceable, and comparable.

Applications

ISO 21154 is applicable to a range of marine vessels and operations, providing practical value in the following areas:

• LNG Carriers and FSRUs: Ensures reliable performance assessment of CCS, facilitating regulatory compliance and reducing operational risks associated with excessive LNG loss.
• LNG Bunkering Vessels: Assists operators and shipbuilders in benchmarking design efficiency and optimizing bunkering schedules to minimize boil-off-related losses.
• LNG Fuel Ships: Provides reference for evaluating and maintaining onboard fuel containment systems, helping achieve higher fuel efficiency.
• Regulatory and Warranty Compliance: Supports shipowners, operators, and maritime technology providers in documenting CCS performance for regulatory authorities, environmental reporting, and warranty claims.
• Cost Optimization: By accurately assessing BOR, stakeholders can better estimate voyage costs, improve CCS design, and enhance overall LNG supply chain sustainability.

Related Standards

• ISO 16063:2015 - Defines terminology for liquefied natural gas, referenced for LNG properties and definitions.
• IMO IGC Code - Provides international regulatory requirements for the design and operation of gas carriers, referenced for definition of cargo containment systems.
• ISO 5937 - Relevant for measurement instrumentation used aboard ships.
• ISO 6976 - Covers determination of calorific values and densities for natural gas, supplementary to LNG properties.

ISO 21154 offers a harmonized, transparent framework for measurement and reporting of boil-off rates, supporting industry best practices, safety, and environmental performance across the LNG maritime sector. Utilizing this standard helps organizations align with international benchmarks, enhance cargo containment system management, and drive efficiency in global LNG shipping operations.

Standards Content (Sample)

International
Standard
ISO 21154
First edition
Ships and marine technology —
2026-05
Boil-off-rate measurement method
for cargo containment system of
LNG ships
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle and facility . 2
4.1 Measurement principle .2
4.2 Measurement parameters .2
4.3 Measurement facility .2
5 BOR measurement procedure . 3
5.1 Measurement conditions .3
5.2 Measurement procedure .4
5.3 Data record .5
5.4 Data posting .6
6 BOR report . 7
Annex A (informative) Examples of record tables . 8
Bibliography .10

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 25, Maritime GHG reduction.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
With the growing international demand for green fuels, LNG has gained widespread use due to its lower
CO emissions, high calorific value and cost-effectiveness. LNG ships, as an important transport equipment,
are increasingly in demand. Central to these vessels is the cargo containment system (CCS), the storage
unit for liquefied gas, which is usually composed of thermal insulation materials and support structures.
Due to the huge temperature difference between ultra-low temperature LNG (−163 °C) and the atmospheric
environment, boil-off is inevitable in the system. The boil-off-rate (BOR) is an important metric for assessing
CCS design quality: the lower the value of BOR, the more efficient and effective the CCS. For shipowners, BOR
also plays a role in calculating transportation costs. Therefore, reliable BOR testing method is essential for
verifying containment system performance at sea.

v
International Standard ISO 21154:2026(en)
Ships and marine technology — Boil-off-rate measurement
method for cargo containment system of LNG ships
1 Scope
This document specifies the principles, conditions, equipment, processes, data acquisition and processing,
and test reports of the boil-off-rate (BOR) test for cargo containment systems (CCS) in liquefied natural gas
(LNG) ships.
It is applicable to the CCS of LNG carriers, LNG floating storage and regassification units (FSRU) and LNG
bunkering vessels. It can be used as reference for the fuel containment system (FCS) of LNG fuel ships.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
boil-off-rate
BOR
percentage between the mass of cryogenic liquid lost during natural evaporation under the rated vapor
pressure in 24 hours and the mass of cryogenic liquid under the effective volume of the cargo containment
systems (3.4) when it reaches the thermal balance at the rated filling rate
3.2
active boil-off-rate
percentage between the mass of cryogenic liquid lost under the rated vapor pressure in 24 hours and the
mass of cryogenic liquid under the effective volume of the cargo containment systems (3.4) with boil off gas
management equipment used for a specific purpose
3.3
liquefied natural gas
LNG
colourless and odourless cryogenic fluid in the liquid state at normal pressure composed predominantly
of methane which can contain minor quantities of ethane, propane, butane, nitrogen, or other components
normally found in natural gas
[SOURCE: ISO 16903:2015, 3.3]
3.4
cargo containment system
CCS
arrangement for containment of cargo including, where fitted, a primary and secondary barrier, associated
and any intervening spaces, and adjacent structure, if necessary, for the support of these elements
Note 1 to entry: If the secondary barrier is part of the hull structure, it may be a boundary of the hold space.
[2]
[SOURCE: IMO IGC Code, 1.2.8, modified — structure of the definition modified to fit the context of this
document.]
4 Principle and facility
4.1 Measurement principle
The rate of change in LNG quantity is measured over time and the loss of LNG during a given period is
calculated based on a heat balance approach.
4.2 Measurement parameters
In order to calculate the BOR, the following parameters shall be measured and recorde
...