EN ISO 12213-1:2005

SLOVENSKI STANDARD
01-julij-2005
=HPHOMVNLSOLQ±,]UDþXQNRPSUHVLMVNHJDIDNWRUMD±GHO8YRGLQVPHUQLFH,62

Natural gas - Calculation of compression factor - Part 1: Introduction and guidelines (ISO
12213-1:1997)
Erdgas - Berechnung von Realgasfaktoren - Teil 1: Einführung und Leitfaden (ISO 12213
-1:1997)
Gaz naturel - Calcul du facteur de compression - Partie 1: Introduction et directives (ISO
12213-1:1997)
Ta slovenski standard je istoveten z: EN ISO 12213-1:2005
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 12213-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2005
ICS 75.060
English version
Natural gas - Calculation of compression factor - Part 1:
Introduction and guidelines (ISO 12213-1:1997)
Gaz naturel - Calcul du facteur de compression - Partie 1: Erdgas - Berechnung von Realgasfaktoren - Teil 1:
Introduction et directives (ISO 12213-1:1997) Einführung und Leitfaden (ISO 12213-1:1997)
This European Standard was approved by CEN on 17 April 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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EUROPÄISCHES KOMITEE FÜR NORMUNG
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© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12213-1:2005: E
worldwide for CEN national Members.

Foreword
The text of ISO 12213-1:1997 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 12213-1:2005 by CMC.
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 November 2005, and conflicting national
standards shall be withdrawn at the latest by November 2005.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 12213-1:1997 has been approved by CEN as EN ISO 12213-1:2005 without any
modifications.
INTERNATIONAL ISO
12213-1
STANDARD
First edition
1997-12-01
Natural gas — Calculation of compression
factor —
Part 1:
Introduction and guidelines
Gaz naturel — Calcul du facteur de compression —
Partie 1: Introduction et directives
A
Reference number
ISO 12213-1:1997(E)
ISO 12213-1:1997(E)
Contents Page
1 Scope . 1
2 Normative references . 2
3 Definitions . 2
4 General principles . 3
5 Guidelines . 4
5.1 Pipeline quality natural gases . 4
5.1.1 Pipeline quality gas . 4
5.1.2 Transmission and distribution metering . 5
5.1.3 Calculation using a molar-composition analysis . 5
5.1.4 Calculation using physical properties . 6
5.1.5 Manufactured gases . 6
5.1.6 Predictive uncertainty . 6
5.1.7 Wider ranges of pressure and temperature . 7
5.2 Other gases and other applications . 7
5.2.1 Introduction . 7
5.2.2 Lean and rich gases . 8
5.2.3 Wet and sour gases . 8
5.2.4 Manufactured gases . 8
5.2.5 Summary of predictive uncertainty . 8
5.2.6 Calculation of related properties . 9
Annexes
A Symbols and units . 10
B Suppliers of computer programmes . 11
C Bibliography . 12
©  ISO 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet central@iso.ch
X.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii
©
ISO ISO 12213-1:1997(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.
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.
International Standard ISO 12213-1 was prepared by Technical Committee
ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas.
ISO 12213 consists of the following parts, under the general title Natural
gas — Calculation of compression factor:
— Part 1: Introduction and guidelines
— Part 2: Calculation using molar-composition analysis
— Part 3: Calculation using physical properties
Annex A forms an integral part of this part of ISO 12213. Annexes B and C
are for information only.
iii
©
INTERNATIONAL STANDARD  ISO ISO 12213-1:1997(E)
Natural gas — Calculation of compression factor —
Part 1:
Introduction and guidelines
1  Scope
This International Standard specifies methods for the calculation of compression factors of natural gases, natural
gases containing a synthetic admixture and similar mixtures at conditions under which the mixture can exist only as
a gas.
The standard is in three parts: part 1 gives an introduction and provides guidelines for the methods of calculation
described in parts 2 and 3.
Part 2 gives a method for use where the detailed molar composition of the gas is known. Part 3 gives a method for
use where a less detailed analysis, comprising superior calorific value (volumetric basis), relative density, carbon
dioxide content and (if non-zero) hydrogen content, is available.
Both methods are applicable to dry gases of pipeline quality within the range of conditions under which transmission
and distribution, including metering for custody transfer or other accounting purposes, are normally carried out. In
general, such operations take place at temperatures between about 263 K and 338 K (approximately - 10 °C to
65 °C) and pressures not exceeding 12 MPa (120 bar). Within this range, the uncertainty of prediction of both
methods is about – 0,1 % provided that the input data, including the relevant pressure and temperature, have no
uncertainty.
NOTE —  Pipeline quality gas is used in this International Standard as a concise term for gas which has been processed so as
to be suitable for use as industrial, commercial or domestic fuel. Although there is no formal international agreement upon the
composition and properties of a gas which complies with this concept, some quantitative guidance is provided in 5.1.1. A
detailed gas quality specification is usually a matter for contractual arrangements between buyer and seller.
The method given in part 2 is also applicable (with increased uncertainty) to broader categories of natural gas,
including wet or sour gases, within a wider range of temperatures and to higher pressures, for example at reservoir
or underground storage conditions or for vehicular (NGV) applications.
The method given in part 3 is applicable to gases with a higher content of nitrogen, carbon dioxide or ethane than
normally found in pipeline quality gas. The method may also be applied over wider ranges of temperature and
pressure but with increased uncertainty.
For the calculation methods described to be valid, the gas must be above its water and hydrocarbon dewpoints at
the prescribed conditions.
The standard gives all of the equations and numerical values needed to implement both methods. Verified computer
programmes are available (see annex B).
©
ISO
ISO 12213-1:1997(E)
2  Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 12213. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 12213 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
ISO 6976:1995, Natural gas — Calculation of calorific values, density, relative density and Wobbe index from
composition.
ISO 13443:1996, Natural gas — Standard reference conditions.
3  Definitions
For the purposes of the various parts of this International Standard, the following definitions apply.
3.1  compression factor, Z: The ratio of the volume of an arbitrary mass of gas, at a specified pressure and
temperature, to the volume of the same mass of gas under the same conditions as calculated from the ideal-gas
law, as follows:
Z = V (real)/ V (ideal) . . . (1)
m m
where V (ideal) = RT/p . . . (2)
m
Thus, Z(p, T, y) = pV (p, T, y)/(RT) . . . (3)
m
where
p is the absolute pressure;
T is the thermodynamic temperature;
y is a set of parameters which uniquely characterizes the gas (in principle, the latter may be the complete
molar composition or a distinctive set of dependent physico-chemical properties, or a mixture of both);
V is the molar volume of the gas;
m
R is the molar gas constant in coherent units.
The compression factor is a dimensionless quantity usually close to unity.
NOTE —  The terms “compressibility factor” and “Z-factor” are synonymous with compression factor.
3.2  density, r: The mass of a given quantity of gas divided by its volume at specified conditions of pressure and
temperature.
3.3  molar composition: The term used when the proportion of each component in a homogeneous mixture is
expressed as a mole (or molar) fraction, or mole (molar) percentage, of the whole.
Thus the mole fraction x of component i is the ratio of the number of moles of component i in a given volume of a
i
mixture to the total number of moles of all the components in the same volume of the mixture. One mole of any
chemical species is the amount of substance which contains the relative molecular mass in grams. A table of
recommended values of relative molecular masses is given in ISO 6976.
For an ideal gas, the mole fraction (or percentage) is identical to the volume fraction (or percentage), but this is not in
general a sufficiently accurate approximation to real-gas behaviour for the purposes of this International Standard.
©
ISO
ISO 12213-1:1997(E)
3.4  molar calorific value, H: The amount of heat which would be released by the complete combustion in air of
the hydrocarbons in one mole of natural gas in such a way that the pressure at which the reaction takes place
remains constant and all the products of combustion are returned to the same specified temperature as that of the
reactants, all of these products being in the gaseous state except for water formed by combustion, which is
condensed to the liquid state at the specified temperature.
Note that the molar calorific value only includes the hydrocarbons in the natural gas, i.e. inert components (primarily
nitrogen, carbon dioxide and helium) and other combustible components (such as hydrogen and carbon monoxide)
are excluded.
The specified temperature is 298,15 K (25 °C) and the reference pressure is 101,325 kPa.
The term “molar heating value” is synonymous with “molar calorific value”.
3.5  superior calorific value, H (volumetric
...