ISO 4266-5:2024

International
Standard
ISO 4266-5
Second edition
Petroleum and liquid petroleum
2024-09
products — Measurement of level
and temperature in storage tanks by
automatic methods —
Part 5:
Measurement of temperature in
marine vessels
Pétrole et produits pétroliers liquides — Mesurage du niveau et
de la température dans les réservoirs de stockage par méthodes
automatiques —
Partie 5: Mesurage de la température dans les citernes de navire
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative reference . 1
3 Terms and definitions . 1
4 Precautions . 2
4.1 Safety precautions .2
4.2 Equipment precautions .2
4.3 General precautions .2
5 Accuracy . 3
5.1 General .3
5.2 Intrinsic error of ATTs .3
5.3 Calibration prior to installation .3
5.3.1 General .3
5.3.2 ATT calibrated as a system .4
5.3.3 ATT calibrated by components .4
5.3.4 Multiple-point ATTs .4
5.3.5 Uncertainty of the reference .4
5.4 Error caused by installation and operating conditions .4
5.5 Overall accuracy . .4
5.5.1 General .4
5.5.2 Use of ATT for fiscal/custody transfer purposes .5
6 Selection of ATTs . 5
6.1 General .5
6.2 ATTs for fiscal/custody transfer purpose .5
7 Description of ATT equipment — Electrical temperature elements . 6
7.1 General .6
8 Installation of marine ATTs . 6
8.1 General .6
8.2 Location of temperature-sensing element(s) .6
8.3 Location of manual (temperature) gauge hatch .6
8.4 Temperature measurement of inerted tanks .6
9 Calibration and on-board verification of marine ATTs . 7
9.1 General .7
9.2 Calibration of single-point temperature element ATTs for fiscal/custody transfer
purposes .7
9.2.1 Calibration prior to installation .7
9.2.2 Initial verification at shipyard or during sea trials .7
9.3 Calibration of multiple-point ATTs for fiscal/custody transfer purposes .8
9.3.1 Calibration prior to installation .8
9.3.2 Initial on-board verification at shipyard or during sea trials .8
9.4 Subsequent verification of ATTs .9
9.4.1 General .9
9.4.2 Frequency of subsequent verification .9
9.4.3 Record keeping .9
10 Data communication and receiving . 10
Annex A (informative) Accuracy limitations of tank-temperature measurements on board
marine vessels .11
Bibliography .12

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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constitute an endorsement.
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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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels
and lubricants from natural or synthetic sources, Subcommittee SC 2, Measurement of petroleum and related
products.
This second edition cancels and replaces the first edition (ISO 4266-5:2002), which has been technically
revised.
The main changes are as follows:
— slightly modified the scope;
— updated normative references;
— expanded safety precautions;
— clarified the expectations for calibrated equipment throughout the document;
— added references to the bibliography.
A list of all parts in the ISO 4266 series can be found on the ISO website.
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
International Standard ISO 4266-5:2024(en)
Petroleum and liquid petroleum products — Measurement
of level and temperature in storage tanks by automatic
methods —
Part 5:
Measurement of temperature in marine vessels
1 Scope
This document provides requirements and guidance on the selection, accuracy, installation, commissioning,
calibration and verification of automatic tank thermometers (ATTs) in fiscal/custody transfer applications.
The ATT is used for measuring the temperature of petroleum and liquid petroleum products having a Reid
vapour pressure less than 100 kPa, stored in cargo tanks on board marine vessels (i.e. tankers and barges).
This document is not applicable to the measurement of temperature in refrigerated storage tanks, or
pressurized cargo tanks on board marine vessels, which is covered in ISO 8310.
2 Normative reference
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1998 (all parts), Petroleum industry — Terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1998 (all parts) and the following 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
automatic tank thermometer
ATT
instrument that continuously measures temperature in storage (or cargo) tanks
Note 1 to entry: A marine ATT, which can also be known as an automatic tank temperature system, typically includes
precision temperature sensors, deck-mounted transmitters for electronic signal transmission, and receiving/readout
device(s).
3.2
resistance temperature detector
RTD
electrical temperature-sensing element commonly used to measure the temperature of the contents of a
storage tank
3.3
single-point automatic tank thermometer
spot automatic tank thermometer
automatic tank thermometer (3.1) that measures the temperature at a particular point in a tank by the spot
temperature element
3.4
multiple-point automatic tank thermometer
automatic tank thermometer (3.1) consisting of multiple (usually three or more) spot temperature elements
to measure the temperature(s) at selected liquid level(s)
Note 1 to entry: The readout equipment should average the readings from the submerged temperature elements to
compute the average temperature of the liquid in the tank and may also display the temperature profile in the tank.
3.5
temperature transmitter
instrument that typically provides electrical power to the temperature element(s), converts the temperature
measured by the element(s) to an electrical or electronic signal, and transmits the signal to a remote readout
Note 1 to entry: A local readout may be provided. Often, the function of the temperature transmitter is provided by the
level transmitter of the automatic level gauge
4 Precautions
4.1 Safety precautions
Relevant international standards, classification society rules and the International Safety Guide for Oil
[4]
Tankers and Terminals (ISGOTT) containing regulations on safety and material-compatibility precautions
should be followed when using marine ATT equipment. In addition, the manufacturer’s recommendations on
the use and installation of the equipment should be followed. All requirements covering entry into hazardous
areas are expected to be observed.
4.2 Equipment precautions
4.2.1 All marine ATTs should be capable of withstanding the pressure, temperature and other
environmental conditions likely to be encountered in marine service. When an ATT is installed in a corrosive
service, any parts exposed to the liquid or vapour should be of durable, corrosion-resistant construction to
avoid both product contamination and ATT corrosion. All ATTs should be sealed to withstand the vapour
pressure of liquid in the tank. ATTs mounted on vessels with an inert gas system (IGS) should be designed to
withstand the operating pressure of the IGS.
4.2.2 All marine ATTs should be specified and installed according to appropriate marine electrical safety
standards, including those developed by the IMO, IEC, CENELEC, ISGOTT and ISO. ATTs should be certified
for use in the hazardous-area classification appropriate to their installation.
4.2.3 All external metal parts of ATTs mounted on tanks should be firmly connected to an electrical earth,
i.e. the ship's hull.
4.2.4 All ATT equipment should be maintained in safe operating condition and the manufacturer’s
maintenance instructions should be complied with.
4.3 General precautions
4.3.1 The general precautions given in 4.3.2 to 4.3.6 apply to all types of ATTs and should be observed
where they are applicable.
4.3.2 Tank levels should be measured and recorded simultaneously, or as close as practical, as the tank
temperature is measured. For more details on level measurement, refer to ISO 4266-2.
4.3.3 Temperatures measured for bulk transfer should be recorded when they are taken, unless the
remote readout equipment of the ATT automatically records the temperatures periodically.
4.3.4 In the case of multiple port loading and/or discharge, the same general procedures should be used to
measure a tank temperature before product transfer (opening gauge) and after product transfer (closing gauge).
4.3.5 ATTs should provide security to prevent unauthorized adjustment or tampering. ATTs used in fiscal/
custody transfer applications should provide facilities to allow sealing to prevent unauthorized calibration
adjustment.
This protection can require mounting the ATT sensor(s) in a thermowell.
ATT sensors can be an integral part of the ALG level sensor assembly (e.g. float and tape, pole). Some design
(e.g. float and tape) can require the level/temperature sensor assembly to be raised to a “store” position
when it is not being used. Such ATTs shall not be used during tank washing.
4.3.6 The design and installation of ATTs can be subject to the approval of the national measurement
organization, who will normally have issued a type or pattern approval (“Type Approval”) for the design of
the ATT for the particular service for which it is to be employed. Type approval is normally issued after an
ATT has been subjected to a specific series of tests and is subject to the ATT being installed in an approved
manner. Type approval tests may include the following: visual inspection, performance, vibration, humidity,
dry heat, inclination, fluctuations in power supplies, insulation, resistance, electromagnetic compatibility
and high voltage.
5 Accuracy
5.1 General
The accuracy of petroleum temperatures taken by the ATTs should be consistent with the accuracy of the
levels taken by the automatic level gauging system so that the overall accuracy of the standard volume
measurement is not seriously degraded. Observance of the accuracy requirements for level and temperature
gauging systems given in ISO 4266-2 and in this document are expected to ensure overall accuracy of the
standard volume measurement.
5.2 Intrinsic error of ATTs
The intrinsic error of the ATT, i.e. the accuracy of the ATTs when tested under controlled conditions
as specified by the manufacturers, can be a major component of the uncertainty of the temperature
measurement of the ATT as installed. It is presupposed that the calibration reference device used to calibrate
the ATT is traceable to appropriate national stand
...