Refrigerated hydrocarbon and non-petroleum based liquefied gaseous fuels — Metering of gas as fuel on LNG carriers during cargo transfer operations

ISO 19970:2017 specifies minimum requirements to quantify the boil-off gas (BOG) consumed on liquefied natural gas (LNG) carriers for their own functions, notably for power generation, during cargo transfer operations. BOG in this document refers to the low molecular gas returned from shore tanks to ships' tanks and the gas produced in ships' cargo tanks. ISO 19970:2017 provides requirements for the metering of BOG and the subsequent calorific value calculations which can be taken into account when the energy transferred during cargo transfer is determined. This document also introduces performance requirements and calibration of the elements included in the BOG measurement system. A flowmeter of any type may be used to measure BOG as long as it meets the performance requirements specified in this document. ISO 19970:2017, with some modification, can also be applied to the measurement of BOG consumed by LNG carriers at sea.

Hydrocarbures réfrigérés et combustibles gazeux liquéfiés à base non pétrolière — Mesurage du gaz comme carburant sur les transporteurs de GNL pendant les opération de transfert de cargaison

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Status
Published
Publication Date
23-May-2017
Current Stage
9060 - Close of review
Due Date
02-Sep-2022
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INTERNATIONAL ISO
STANDARD 19970
First edition
2017-06
Refrigerated hydrocarbon and non-
petroleum based liquefied gaseous
fuels — Metering of gas as fuel on
LNG carriers during cargo transfer
operations
Hydrocarbures réfrigérés et combustibles gazeux liquéfiés à base non
pétrolière — Mesurage du gaz comme carburant sur les transporteurs
de GNL pendant les opération de transfert de cargaison
Reference number
ISO 19970:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 19970:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, 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.
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ii © ISO 2017 – All rights reserved
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ISO 19970:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Design requirements ........................................................................................................................................................................................ 3

4.1 General ........................................................................................................................................................................................................... 3

4.2 Flowmeter ................................................................................................................................................................................................... 3

4.3 Indicating device ................................................................................................................................................................................... 3

5 Accuracy requirement .................................................................................................................................................................................... 3

6 Calibration and accuracy verification ............................................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Calibration at laboratory or factory ...................................................................................................................................... 4

6.3 Calibration and accuracy verification of indicating devices after installation ................................. 4

6.4 Periodic accuracy verification of indicating devices .............................................................................................. 4

7 Metering and calculation ............................................................................................................................................................................. 5

7.1 General ........................................................................................................................................................................................................... 5

7.2 Metering ........................................................................................................................................................................................................ 5

7.3 Calculation of heating value ......................................................................................................................................................... 5

Annex A (informative) Typical installation of fuel gas flowmeters ...................................................................................... 7

Annex B (informative) Application of the energy of BOG consumed by LNG carriers to

custody transfer measurement ............................................................................................................................................................. 8

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2017 – All rights reserved iii
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ISO 19970:2017(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: w w w . i s o .org/ iso/ foreword .html.

The committee responsible for this document is ISO/TC 28, Petroleum products and related products

of synthetic or biological origin, Subcommittee SC 5, Measurement of refrigerated hydrocarbon and non-

petroleum based liquefied gaseous fuels.
iv © ISO 2017 – All rights reserved
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ISO 19970:2017(E)
Introduction

Concerns over the emission of pollutants from ship exhausts prompted IMO to enact MARPOL Annex

VI to the IMO Protocol of 1997 which sets limits on sulfur oxide and nitrogen oxide emissions. As for

sulfur, as from 1 January 2012, the annex specifies a global cap mass fraction of 3,5 % on the sulfur

content of fuel oil and special SOx emission control areas (SECAs) where the sulfur contents shall not

exceed a mass fraction of 1,0 %. In order to comply with these requirements, the ships in general need

to fit special facilities to limit SOx emissions unless they use low sulfur fuel oil.

However, liquefied natural gas (LNG) carrier is capable of utilizing BOG in ship’s and shore tanks, and

return gas during cargo transfer operation as fuel for their own power generation, if commercial value

of such energy consumed on board is accountable as an element of custody transfer measurement.

This document provides the procedures needed for metering gas and assessing its calorific value and

the requirements for metering devices.

Aspects of safety are not dealt with in this document. It is the responsibility of the user to ensure that

the system meets applicable safety regulations.
© ISO 2017 – All rights reserved v
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INTERNATIONAL STANDARD ISO 19970:2017(E)
Refrigerated hydrocarbon and non-petroleum based
liquefied gaseous fuels — Metering of gas as fuel on LNG
carriers during cargo transfer operations
1 Scope

This document specifies minimum requirements to quantify the boil-off gas (BOG) consumed on

liquefied natural gas (LNG) carriers for their own functions, notably for power generation, during cargo

transfer operations. BOG in this document refers to the low molecular gas returned from shore tanks to

ships’ tanks and the gas produced in ships’ cargo tanks.

This document provides requirements for the metering of BOG and the subsequent calorific value

calculations which can be taken into account when the energy transferred during cargo transfer is

determined. This document also introduces performance requirements and calibration of the elements

included in the BOG measurement system. A flowmeter of any type may be used to measure BOG as

long as it meets the performance requirements specified in this document.

This document, with some modification, can also be applied to the measurement of BOG consumed by

LNG carriers at sea.
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 terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
boil off

process of evaporation of a liquid resulting from heat ingress or a drop in pressure

[SOURCE: ISO 10976:2015, 3.1.6]
3.2
boil-off gas
BOG
vapour (3.14) produced by boil off (3.1)

Note 1 to entry: BOG in this document refers to the low molecular gas returned from shore tanks to ships’ tanks

and the gas produced in ships’ cargo tanks during cargo transfer operation.
[SOURCE: ISO 10976:2015, 3.1.7 — Note 1 to entry has been added.]
3.3
closing custody transfer measurement

custody transfer measurement (3.4) implemented after loading or discharging cargo from the tank(s)

© ISO 2017 – All rights reserved 1
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ISO 19970:2017(E)
3.4
custody transfer measurement

measurement of liquid level, liquid and vapour temperature, vapour pressure and analysis of the

composition of LNG to be delivered to/from a tank, by which volumetric and other data are determined

to be a basis of payment of cost or assessment of duty
3.5
custody transfer measurement system
CTMS

system that processes inputs from an ATG system, thermometers, pressure gauges, etc., and provides

custody transfer measurement information on board, generating documents with regard to custody

transfer of LNG
[SOURCE: ISO 18132-1:2011, 2.1.4, modified]
3.6
flowmeter
flow measuring device which indicates the measured flowrate
3.7
gas dangerous space or zone

space or zone defined by the International Code for the Construction and Equipment of Ships Carrying

Liquefied Gases in Bulk (IGC Code)
3.8
indicating device
displaying device

set of components of a measuring instrument intended to indicate the measured value

3.9
intrinsic error
inherent error

error of a measuring device when it is tested against a reference standard under controlled conditions

as specified by the manufacturer
3.10
LNG carrier
LNGC
cargo ship specifically constructed and used for the carriage of LNG in bulk
3.11
maximum permissible error
MPE

extreme value of measurement error, with respect to a known reference quantity value, permitted by

specifications or regulations for a given measurement, measuring instrument, or measuring system

[SOURCE: ISO/IEC Guide 99:2007, 4.26, modified]
3.12
opening custody transfer measurement

custody transfer measurement (3.4) implemented before loading or discharging cargo from the tank(s)

3.13
uncertainty

non-negative parameter characterizing the dispersion of the quantity values being attributed to a

measurand, based on the information used
3.14
vapour

fluid in the gaseous state that is transferred to/from or contained within the cargo tank

2 © ISO 2017 – All rights reserved
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ISO 19970:2017(E)
3.15
verification

process of confirming the accuracy of an instrument by comparing to a source with known accuracy

4 Design requirements
4.1 General
Flowmeters shall be so constructed as not to leak g
...

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