Natural gas - Measurement of properties - Volumetric properties: density, pressure, temperature and compression factor (ISO 15970:2008)

EN-ISO 15970 gives requirements and procedures for the measurement of the properties of natural gas that are used mainly for volume calculation and volume conversion: density at reference and at operating conditions, pressure, temperature and compression factor. Only those methods and instruments are considered that are suitable for field operation under the conditions of natural gas transmission and distribution, installed either in-line or on-line, and that do not involve the determination of the gas composition. This International Standard gives examples for currently used instruments that are available commercially and of interest to the natural gas industry. NOTE Attention is drawn to requirements for approval of national authorization agencies and to national legal regulations for the use of these devices for commercial or official trade purposes. The density at reference conditions (sometimes referred to as normal, standard or even base density) is required for conversion of volume data and can be used for other physical properties. Density at operating conditions is measured for mass-flow measurement and volume conversion using the observed line density and can be used for other physical properties. This International Standard covers density transducers based on vibrating elements, normally suitable for measuring ranges of 5 kg/m3 to 250 kg/m3. Pressure measurement deals with differential, gauge and absolute pressure transmitters. It considers both analogue and smart transmitters (i.e. microprocessor based instruments) and, if not specified otherwise, the corresponding paragraphs refer to differential, absolute and gauge pressure transmitters without distinction. Temperature measurements in natural gas are performed within the range of conditions under which transmission and distribution are normally carried out (253 K < T < 338 K). In this field of application, resistance thermometer detectors (RTD) are generally used. The compression factor (also known as the compressibility factor or the real gas factor and given the symbol Z) appears, in particular, in equations governing volumetric metering. Moreover, the conversion of volume at metering conditions to volume at defined reference conditions can properly proceed with an accurate knowledge of Z at both relevant pressure and relevant temperature conditions.

Erdgas - Messung der Eigenschaften - Volumetrische Eigenschaften: Dichte, Druck, Temperatur und Kompressibilitätsfaktor (ISO 15970:2008)

Diese Internationale Norm enthält Anforderungen und Verfahren für die Messung der Eigenschaften von Erdgas, die hauptsächlich zur Volumenberechnung und Volumenumrechnung verwendet werden: Dichte bei Referenz- und Betriebsbedingungen, Druck, Temperatur und Kompressibilitätsfaktor (Realgasfaktor).
Es werden nur die Verfahren und Messgeräte berücksichtigt, die für den Vor-Ort-Betrieb unter den Bedingungen von Erdgasferntransport und -verteilung geeignet sind und entweder leitungsintegriert oder an der Leitung installiert sind, aber keine Bestimmung der Gaszusammensetzung bedingen.
Diese Internationale Norm enthält Beispiele für derzeit verwendeten Messgeräte, die im Handel erhältlich und für die Erdgasindustrie von Interesse sind.
ANMERKUNG   Es wird auf die Anforderungen an die Zulassung durch nationale Behörden und auf nationale Bestimmungen zum Gebrauch dieser Geräte für kommerzielle und amtliche Handelszwecke verwiesen.
Die Dichte bei Referenzbedingungen (manchmal Norm-, Standard- oder sogar Basisdichte genannt) wird für die Umrechnung von Volumendaten benötigt und kann für andere physikalische Eigenschaften verwendet werden.
Die Dichte bei Betriebsbedingungen wird für die Messung des Massendurchflusses (-stroms) und für die Volumenumrechnung mit der in der Leitung bestimmten Dichte gemessen und kann für andere physikalische Eigenschaften verwendet werden. Diese Internationale Norm berücksichtigt Dichte(messwert)aufnehmer auf Grundlage von Schwingelementen, die normalerweise für Messbereiche von 5 kg/m3 bis 250 kg/m3 geeignet sind.
Die Druckmessung nutzt Differenzdruck-, Manometerdruck- und Absolutdruck-Messumformer. Berücksichtigt werden analoge und intelligente Messumformer (d. h. mikroprozessorgestützte Messgeräte) und die zugehörigen Absätze beziehen sich, sofern nicht anderweitig festgelegt, auf Differenzdruck-, Manometer-druck- und Absolutdruck-Messumformer ohne Unterscheidung.
Die Temperaturmessungen in Erdgas werden innerhalb des Bereichs der Bedingungen durchgeführt, unter denen der Transport und die Verteilung normalerweise erfolgen (253 K < T < 338 K). In diesem Anwendungs-bereich werden im Allgemeinen Widerstandsthermometer (RTD, en: resistance thermometer detector) verwendet.
Der Kompressibilitätsfaktor (auch Kompressionsfaktor oder Realgasfaktor genannt und mit dem Formel-zeichen Z bezeichnet) tritt insbesondere in Gleichungen auf, die die Volumenmessung betreffen. Außerdem kann die Umrechnung des Volumens unter Messbedingungen in das Volumen unter festgelegten Referenz-bedingungen mit einer genauen Kenntnis von Z sowohl unter relevanten Druck- als auch relevanten Temperaturbedingungen richtig ausgeführt werden.

Gaz naturel - Mesurage des caractéristiques - Caractéristiques volumétriques: masse volumique, pression, température et facteur de compression (ISO 15970:2008)

L'ISO 15970:2008 spécifie les exigences et les modes opératoires relatifs au mesurage des caractéristiques du gaz naturel qui sont principalement utilisées pour le calcul et la conversion des volumes: masse volumique dans les conditions de référence et du réseau, pression, température et facteur de compression.
Seuls sont pris en compte les méthodes et les instruments qui conviennent au fonctionnement sur le terrain dans les conditions de transport et de distribution du gaz naturel, installés dans le réseau (à l'intérieur de la conduite ou montés sur celle-ci), et qui n'impliquent pas la détermination de la composition du gaz.
L'ISO 15970:2008 donne des exemples d'instruments actuellement utilisés, disponibles dans le commerce et présentant un intérêt pour l'industrie du gaz naturel.
La masse volumique dans les conditions de référence (parfois appelée «masse volumique normale», «masse volumique standard» voire «masse volumique de base») est requise pour la conversion des données volumiques et peut être utilisée pour d'autres caractéristiques physiques.
La masse volumique dans les conditions de fonctionnement est mesurée en vue du mesurage du débit massique et de la conversion de volume en utilisant la masse volumique aux conditions opératoires observée et elle peut être utilisée pour d'autres caractéristiques physiques. L'ISO 15970:2008 couvre les transducteurs de masse volumique à base d'éléments vibrants, normalement adaptés aux plages de mesure allant de 5 kg/m3 à 250 kg/m3.
Le mesurage de pression concerne les transmetteurs de pression différentielle, relative et absolue. Il tient compte des transmetteurs tant analogiques qu'intelligents (c'est-à-dire les instruments utilisant des microprocesseurs) et, sauf spécification contraire, les paragraphes correspondants se rapportent à des transmetteurs de pression différentielle, absolue et relative, sans distinction.
Les mesurages de température dans le gaz naturel sont effectués dans la plage de conditions normales de transport et de distribution (253 K < T < 338 K). Dans ce champ d'application, des détecteurs de température à résistance (RTD) sont généralement utilisés.
Le facteur de compression (également appelé «facteur de compressibilité» ou «facteur de gaz réel», et auquel le symbole Z est attribué) apparaît notamment dans les équations de comptage du volume. En outre, la conversion d'un volume dans les conditions de mesurage en un volume dans les conditions de référence définies peut être effectuée correctement si l'on connaît précisément Z dans les conditions de température et de pression applicables.

Zemeljski plin - Merjenje njegovih lastnosti - Volumetrične lastnosti: gostota, tlak, temperatura in kompresijski faktor (ISO 15970:2008)

Standard EN-ISO 15970 podaja zahteve in postopke za merjenje lastnosti zemeljskega plina, ki se uporabljajo predvsem za izračun prostornine in prostorninsko konverzijo: gostota pri referenčnih in obratovalnih pogojih, tlak, temperatura in kompresijski faktor. Upoštevane so samo metode in inštrumenti, ki so primerni za terensko uporabo pri pogojih prenosa in distribucije zemeljskega plina, so nameščeni v cevi ali na cevi in ki ne vključujejo določanja sestave plinov. Ta mednarodni standard podaja primere inštrumentov, ki se trenutno uporabljajo, so na voljo na trgu in so zanimivi za industrijo zemeljskega plina. OPOMBA Opozoriti je treba na zahteve za odobritev nacionalnih agencij za izdajo dovoljenj in nacionalne pravne predpise glede uporabe teh naprav v komercialne ali uradne trgovske namene. Gostota pri referenčnih pogojih (včasih imenovana normalna, standardna ali osnovna gostota) je potrebna za konverzijo podatkov o prostornini in se lahko uporabi za določevanje drugih fizikalnih značilnosti. Gostota pri obratovalnih pogojih se meri za določevanje masnega pretoka in prostorninske konverzije z uporabo opazovane gostote linije ter se lahko uporabi za določevanje drugih fizikalnih značilnosti. Ta mednarodni standard zajema pretvornike gostote na osnovi vibrirajočih elementov, ki so običajno primerni za merilne razpone od 5 do 250 kg/m3. Merjenje tlaka obravnava diferenčne, merilne in absolutne tlačne oddajnike. Vključuje analogne in pametne merilnike (kot so instrumenti z mikroprocesorjem) in, če ni drugače navedeno, se ustrezni odstavki brez razlike nanašajo na diferenčne, merilne in absolutne tlačne oddajnike. Meritve temperature zemeljskega plina se izvajajo v pogojih, pri katerih običajno potekata prenos in distribucija (253 K

General Information

Status
Published
Public Enquiry End Date
01-Dec-2013
Publication Date
01-Apr-2014
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Mar-2014
Due Date
25-May-2014
Completion Date
02-Apr-2014

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SLOVENSKI STANDARD
SIST EN ISO 15970:2014
01-maj-2014

=HPHOMVNLSOLQ0HUMHQMHQMHJRYLKODVWQRVWL9ROXPHWULþQHODVWQRVWLJRVWRWDWODN

WHPSHUDWXUDLQNRPSUHVLMVNLIDNWRU ,62

Natural gas - Measurement of properties - Volumetric properties: density, pressure,

temperature and compression factor (ISO 15970:2008)
Erdgas - Messung der Eigenschaften - Volumetrische Eigenschaften: Dichte, Druck,
Temperatur und Kompressibilitätsfaktor (ISO 15970:2008)

Gaz naturel - Mesurage des caractéristiques - Caractéristiques volumétriques: masse

volumique, pression, température et facteur de compression (ISO 15970:2008)
Ta slovenski standard je istoveten z: EN ISO 15970:2014
ICS:
75.060 Zemeljski plin Natural gas
75.180.30 Oprema za merjenje Volumetric equipment and
prostornine in merjenje measurements
SIST EN ISO 15970:2014 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 15970:2014
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SIST EN ISO 15970:2014
EUROPEAN STANDARD
EN ISO 15970
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2014
ICS 75.060; 75.180.30
English Version
Natural gas - Measurement of properties - Volumetric properties:
density, pressure, temperature and compression factor (ISO
15970:2008)

Gaz naturel - Mesurage des caractéristiques - Erdgas - Messung der Eigenschaften - Volumetrische

Caractéristiques volumétriques: masse volumique, Eigenschaften: Dichte, Druck, Temperatur und

pression, température et facteur de compression (ISO Kompressibilitätsfaktor (ISO 15970:2008)

15970:2008)
This European Standard was approved by CEN on 16 February 2014.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same

status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United

Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15970:2014 E

worldwide for CEN national Members.
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SIST EN ISO 15970:2014
EN ISO 15970:2014 (E)
Contents Page

Foreword ..............................................................................................................................................................3

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SIST EN ISO 15970:2014
EN ISO 15970:2014 (E)
Foreword

The text of ISO 15970:2008 has been prepared by Technical Committee ISO/TC 193 “Natural gas” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 15970:2014.

This European Standard shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by September 2014, and conflicting national standards shall be

withdrawn at the latest by September 2014.

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

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Endorsement notice

The text of ISO 15970:2008 has been approved by CEN as EN ISO 15970:2014 without any modification.

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SIST EN ISO 15970:2014
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SIST EN ISO 15970:2014
INTERNATIONAL ISO
STANDARD 15970
First edition
2008-06-15
Natural gas — Measurement of
properties — Volumetric properties:
density, pressure, temperature and
compression factor
Gaz naturel — Mesurage des caractéristiques — Caractéristiques
volumétriques: masse volumique, pression, température et facteur de
compression
Reference number
ISO 15970:2008(E)
ISO 2008
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
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electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

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ii © ISO 2008 – All rights reserved
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
Contents Page

Foreword............................................................................................................................................................. v

Introduction ....................................................................................................................................................... vi

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

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

3 Terms and definitions........................................................................................................................... 2

3.1 Terms and definitions for density at reference conditions .............................................................. 2

3.2 Terms and definitions for density at operating conditions.............................................................. 2

3.3 Terms and definitions for pressure .................................................................................................... 3

3.4 Terms and definitions for temperature............................................................................................... 4

3.5 Terms and definitions for compression factor .................................................................................. 4

4 Symbols and units................................................................................................................................ 4

4.1 Symbols and subscripts for density at reference conditions.......................................................... 4

4.2 Symbols and subscripts for density at operating conditions.......................................................... 5

4.3 Symbols and subscripts for compression factor.............................................................................. 5

5 Density at reference conditions .......................................................................................................... 6

5.1 Principle of measurement.................................................................................................................... 6

5.2 Performance assessment and acceptance tests............................................................................. 10

5.3 Sampling and installation guidelines ............................................................................................... 11

5.4 Calibration ........................................................................................................................................... 11

5.5 Verification .......................................................................................................................................... 11

5.6 Maintenance ........................................................................................................................................ 12

5.7 Quality control..................................................................................................................................... 12

6 Density at operating conditions ........................................................................................................ 12

6.1 Principle of measurement.................................................................................................................. 12

6.2 Performance assessment and acceptance tests............................................................................. 13

6.3 Sampling and installation guidelines ............................................................................................... 16

6.4 Calibration ........................................................................................................................................... 20

6.5 Verification .......................................................................................................................................... 20

6.6 Maintenance ........................................................................................................................................ 21

6.7 Quality control..................................................................................................................................... 21

7 Pressure............................................................................................................................................... 21

7.1 Principle of measurement.................................................................................................................. 22

7.2 Performance assessment and acceptance tests............................................................................. 24

7.3 Sampling and installation guidelines ............................................................................................... 24

7.4 Calibration ........................................................................................................................................... 27

7.5 Verification .......................................................................................................................................... 28

7.6 Maintenance ........................................................................................................................................ 28

7.7 Quality control..................................................................................................................................... 29

8 Temperature ........................................................................................................................................ 29

8.1 Principle of measurement.................................................................................................................. 29

8.2 Performance assessment and acceptance tests............................................................................. 30

8.3 Installation guidelines ........................................................................................................................ 31

8.4 Calibration ........................................................................................................................................... 33

8.5 Verification .......................................................................................................................................... 34

8.6 Maintenance ........................................................................................................................................ 34

8.7 Quality control..................................................................................................................................... 34

9 Compression factor............................................................................................................................ 34

© ISO 2008 – All rights reserved iii
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SIST EN ISO 15970:2014
ISO 15970:2008(E)

9.1 Principle of measurement .................................................................................................................. 34

9.2 Working principle................................................................................................................................ 35

9.3 Performance assessment and acceptance tests............................................................................. 38

9.4 Sampling and installation guidelines................................................................................................ 38

9.5 Calibration............................................................................................................................................ 39

9.6 Verification........................................................................................................................................... 40

9.7 Maintenance......................................................................................................................................... 40

9.8 Quality control..................................................................................................................................... 40

Annex A (informative) Guidance for instrument selection, instrument test

and operational procedures............................................................................................................... 41

Annex B (informative) Instrument documentation........................................................................................ 45

Bibliography ..................................................................................................................................................... 47

iv © ISO 2008 – All rights reserved
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SIST EN ISO 15970:2014
ISO 15970:2008(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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 15970 was prepared by Technical Committee ISO/TC 193, Natural gas.
© ISO 2008 – All rights reserved v
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
Introduction

The transmission of natural gas can involve passage across national boundaries; at border stations and

elsewhere, knowledge of the physicochemical properties of the fluid is of great operational and economic

importance. The energy flow and properties of the gas are required at several stages of the overall production

and custody transfer process: production, blending, transmission, metering, distribution and supply.

International standardization of the performance specifications for various types of measuring instruments can

facilitate comparison of, and increase confidence in, measurement results for contracting partners. In many

cases, it is possible to calculate the properties of natural gas with sufficient accuracy, given the composition.

However, it is often also possible to measure the property using techniques that do not require a

compositional analysis for their implementation.

This International Standard considers only those methods for determining physical properties of natural gas

that do not rely upon a detailed component analysis of the gas. Such measurements consider the “whole”

sample of the gas.

This International Standard defines performance characteristics necessary to specify instrumentation for

measurement of some natural gas properties. It provides guidelines for the installation, traceable calibration,

performance, operation, maintenance and acceptance testing of these measurement instruments.

The principle of measurement of various properties included in this International Standard is typical for a

number of applications.

It is required that the calibration of the instruments dealt with in this International Standard be traceable to

national standards or International Standards.

It is required that the measuring instruments, including their installation and the devices used for field

calibration, verification and maintenance comply with local legal regulations on application in hazardous areas.

Annex A presents general guidelines for instrument selection, instrument test and operational procedures of

the instruments considered in this International Standard.

Annex B lists the data of particular importance for the instrument documentation.

vi © ISO 2008 – All rights reserved
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SIST EN ISO 15970:2014
INTERNATIONAL STANDARD ISO 15970:2008(E)
Natural gas — Measurement of properties — Volumetric
properties: density, pressure, temperature and compression
factor
1 Scope

This international Standard gives requirements and procedures for the measurement of the properties of

natural gas that are used mainly for volume calculation and volume conversion: density at reference and at

operating conditions, pressure, temperature and compression factor.

Only those methods and instruments are considered that are suitable for field operation under the conditions

of natural gas transmission and distribution, installed either in-line or on-line, and that do not involve the

determination of the gas composition.

This International Standard gives examples for currently used instruments that are available commercially and

of interest to the natural gas industry.

NOTE Attention is drawn to requirements for approval of national authorization agencies and to national legal

regulations for the use of these devices for commercial or official trade purposes.

The density at reference conditions (sometimes referred to as normal, standard or even base density) is

required for conversion of volume data and can be used for other physical properties.

Density at operating conditions is measured for mass-flow measurement and volume conversion using the

observed line density and can be used for other physical properties. This International Standard covers

density transducers based on vibrating elements, normally suitable for measuring ranges of 5 kg/m to

250 kg/m .

Pressure measurement deals with differential, gauge and absolute pressure transmitters. It considers both

analogue and smart transmitters (i.e. microprocessor based instruments) and, if not specified otherwise, the

corresponding paragraphs refer to differential, absolute and gauge pressure transmitters without distinction.

Temperature measurements in natural gas are performed within the range of conditions under which

transmission and distribution are normally carried out (253 K < T < 338 K). In this field of application,

resistance thermometer detectors (RTD) are generally used.

The compression factor (also known as the compressibility factor or the real gas factor and given the

symbol Z) appears, in particular, in equations governing volumetric metering. Moreover, the conversion of

volume at metering conditions to volume at defined reference conditions can properly proceed with an

accurate knowledge of Z at both relevant pressure and relevant temperature conditions.

2 Normative references

The following referenced documents are indispensable for the application 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 2186, Fluid flow in closed conduits — Connections for pressure signal transmissions between primary

and secondary elements
© ISO 2008 – All rights reserved 1
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SIST EN ISO 15970:2014
ISO 15970:2008(E)

ISO 5167-1, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-

section conduits running full — Part 1: General principals and requirements

ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe index from

composition
ISO 10715, Natural gas — Sampling guidelines

ISO 12213-1, Natural gas — Calculation of compression factor — Part 1: Introduction and guidelines

IEC 60079-0, Explosive atmospheres — Part 0: Equipment — General requirements

IEC 60079-1, Explosive atmospheres — Part 1: Equipment protection by flameproof enclosures “d”

IEC 60079-11, Explosive atmospheres — Part 11: Equipment protection by intrinsic safety “i”'

IEC 60079-14, Explosive atmospheres — Part 14: Electrical installations design, selection and erection

IEC/TR 60079-15, Electrical apparatus for explosive gas atmospheres — Part 15: Construction, test and

marking of type of protection 'n' electrical apparatus

IEC 60381-1, Analogue signals for process control systems — Part 1: Direct current signals

IEC 60381-2, Analogue signals for process control systems — Part 2: Direct voltage signals

IEC 60751, Industrial platinum resistance thermometer sensors

IEC 60770-1, Transmitters for use in industrial-process control systems — Part 1: Methods for performance

evaluation
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1 Terms and definitions for density at reference conditions
3.1.1
density at reference conditions

mass of a gas divided by its volume at specified reference conditions of pressure and temperature

3.1.2
relative density at reference conditions

ratio of the mass of a gas, contained within an arbitrary volume, to the mass of dry air of standard composition

in accordance with ISO 6976, which would be contained in the same volume at the same references

conditions
3.2 Terms and definitions for density at operating conditions
3.2.1
density

mass of a gas divided by its volume at operating conditions of pressure and temperature (operating and

reference conditions)
2 © ISO 2008 – All rights reserved
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
3.2.2
vibrating element density transducer

device that contains a vibrating element that is maintained at its natural frequency, made such that the

element contains or is surrounded by gas, the gas and the element forming a system where the density of the

gas is the main property of the gas determining the natural frequency of the element

NOTE The natural frequency to the first approximation is determined by the gas density.

3.2.3
main density transducer constants

constants that, to a first approximation, define the relationship between the natural frequency of the vibrating

element and the density of the gas
3.2.4
raw density

density as determined by a vibrating-element density transducer from its vibrating frequency by use of the

main density transducer constants before any corrections for temperature, pressure and composition are

applied
3.2.5
correction density transducer constants

constants applicable to a density transducer to correct for the deviation between the calibration condition

under which the main constants were determined and the operating conditions
3.2.6
temperature-corrected density

raw density corrected for difference in temperature to which the vibrating element is exposed in operation and

the temperature at which the density transducer was calibrated
3.2.7
compositional-corrected density

temperature-corrected density, corrected for difference in gas properties between gas to which the vibrating

element is exposed in operation and the gas properties of the gas used for calibration

NOTE Normally, the gas property relevant for this purpose is velocity of sound, hence this term is often referred to as

velocity-of-sound-corrected density.
3.2.8
line density

compositional-corrected density, corrected for difference in operating conditions, e.g. pressure and

temperature, to which the vibrating element is exposed and the operating conditions in the line where the

density is measured
3.3 Terms and definitions for pressure
3.3.1
pressure transmitter

device that responds to a measured pressure to produce a standard output signal for transmission, which has

a prescribed continuous relationship to the value of the measured pressure
3.3.2
lower range value
LRV
lowest value of the pressure that a transmitter is adjusted to measure
3.3.3
upper range value
URV
highest value of the pressure that a transmitter is adjusted to measure
© ISO 2008 – All rights reserved 3
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
3.3.4
span
algebraic difference between the upper and lower range values
3.3.5
static pressure

pressure that would be measured by a pinpoint observer travelling with a particle of the fluid

3.3.6
absolute static pressure
static pressure of a fluid measured with reference to an absolute vacuum
3.3.7
gauge pressure

difference between the absolute static pressure of a fluid and the atmospheric pressure at the place and time

of the measurement
3.4 Terms and definitions for temperature
3.4.1
temperature transmitter

device that responds to a measured temperature to produce a standard output signal for transmission, which

has a prescribed continuous relationship to the value of the measured temperature

3.5 Terms and definitions for compression factor
3.5.1
least squares method

method used to compute the coefficients of the equation when a particular form of equation is chosen for

fitting a curve data

NOTE The principle of least squares is the minimization of the sum of squares of deviations of the data from the

curve.
4 Symbols and units
4.1 Symbols and subscripts for density at reference conditions
Symbol Quantity Unit
k Ratio of Z(p, T) and Z
Z n
p Absolute pressure Pa
Density
ρ kg/m
T Thermodynamic temperature K
Z Compression factor —
Subscripts
A Standard air
m Measured gas/measuring chamber
n Reference conditions
r Reference chamber
4 © ISO 2008 – All rights reserved
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SIST EN ISO 15970:2014
ISO 15970:2008(E)
4.2 Symbols and subscripts for density at operating conditions
Symbol Quantity Unit
C Velocity of sound m/s
C Velocity of sound in calibration gas m/s
C Velocity of sound in gas in density transducer m/s
Frequency
Density transducer constants
K K K
1 2 N
ρ Raw density
kg/m
Temperature corrected density
ρ kg/m
ρ Compositional corrected density
kg/m
Line density
ρ kg/m
T Calibration temperature K
Calibration temperature °C
Temperature in density transducer K
...

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