ISO 6570:2001
(Main)Natural gas — Determination of potential hydrocarbon liquid content — Gravimetric methods
Natural gas — Determination of potential hydrocarbon liquid content — Gravimetric methods
This International Standard describes the principles of, and general requirements for, two gravimetric methods for the determination of the potential hydrocarbon liquid content of natural gas, or similar gas, at a given pressure and temperature. Two methods are specified in this International Standard to determine the amount of condensate in a sample gas: _ Method A: a manual weighing method; _ Method B: an indirect automatic weighing method based on the indication of the pressure difference caused by the accumulation of condensate in a vertical tube. The manual weighing method is a reference method for the indirect automatic method (Method B). The indirect automatic method (Method B) is suitable for semi-continuous control. NOTE Unless otherwise specified, gas volumes are in cubic metres at 273,15 K and 101,325 kPa.
Gaz naturel — Détermination de la teneur en hydrocarbures liquides potentiels — Méthodes gravimétriques
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INTERNATIONAL ISO
STANDARD 6570
First edition
2001-06-15
Natural gas — Determination of potential
hydrocarbon liquid content — Gravimetric
methods
Gaz naturel — Détermination de la teneur en hydrocarbures liquides
potentiels — Méthodes gravimétriques
Reference number
©
ISO 2001
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
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 either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Principle.2
4 Apparatus requirements .2
4.1 Measurement installation.2
4.2 Check for correct installation operation .5
5 Sampling.10
5.1 General.10
5.2 Sampling conditions .10
5.3 Sample line.10
5.4 Direct sampling.10
5.5 Indirect sampling .10
6 Procedure .11
6.1 Determination of potential hydrocarbon liquid content.11
6.2 Determination of water formation .12
7 Expression of results .12
7.1 Method A — Manual weighing method.12
7.2 Method B — Indirect automatic method.14
8 Uncertainty of measurement .15
8.1 Achievable uncertainty .15
8.2 Gas leakage.15
8.3 Bath liquid .16
8.4 Wet gas .16
8.5 Condensate leakage .16
8.6 Variations in bath temperature and pressure in the gas/liquid cyclone separator .16
8.7 Premature condensation.16
9 Test report .16
Annex A (informative) Selection of measurement temperature and pressure.17
Annex B (informative) Examples of the line-up of the apparatus .18
Annex C (informative) Example of calibration of the differential pressure gauge for the indirect
automatic method — Method B.19
Annex D (informative) Example of an indirect automatic measurement — Method B.21
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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 6570 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee
SC 1, Analysis of natural gas.
This first edition cancels and replaces ISO 6570-1:1983 and ISO 6570-2:1984, which have been technically
revised.
Annexes A to D of this International Standard are given for information only.
iv © ISO 2001 – All rights reserved
Introduction
Under certain conditions, higher hydrocarbons present in natural gas or similar gases may condense and the
condensate formed can cause difficulties in the operation of gas transport and distribution systems.
Dew-point measurements, by condensation on a mirror, may give an indication of the conditions under which
condensation starts. However, these measurements give no further information about the amount of liquid to be
expected under operating conditions.
For proper operation of transport and distribution systems, a knowledge of the quantities of condensate formed as
a function of temperature and pressure is required. This knowledge is also required for the design of production
and treatment systems as well as for subsequent handling and disposal of the liquid.
The methods described in this International Standard are intended for the determination of the quantity of
hydrocarbon condensate formed from a natural gas or similar gas as a function of the temperature and pressure of
the gas.
Instruments based on different measurement principles can give a figure related to potential condensate content or
dew point. The dew point can only be determined by performing measurements at different temperatures followed by
extrapolation of the measurements to a potential hydrocarbon liquid content (� ) value of zero. The methods
PHLC
described in this International Standard can be used to calibrate such instruments.
INTERNATIONAL STANDARD ISO 6570:2001(E)
Natural gas — Determination of potential hydrocarbon liquid
content — Gravimetric methods
WARNING — The use of this International Standard may involve hazardous materials, operations and
equipment. This International Standard does not purport to address all of the safety problems associated
with its use. It is the responsibility of the user of this International Standard to establish appropriate safety
and health practices and to determine the applicability or regulatory limitations prior to use.
1 Scope
This International Standard describes the principles of, and general requirements for, two gravimetric methods for
the determination of the potential hydrocarbon liquid content of natural gas, or similar gas, at a given pressure and
temperature. Two methods are specified in this International Standard to determine the amount of condensate in a
sample gas:
� Method A: a manual weighing method;
� Method B: an indirect automatic weighing method based on the indication of the pressure difference caused by
the accumulation of condensate in a vertical tube.
The manual weighing method is a reference method for the indirect automatic method (Method B). The indirect
automatic method (Method B) is suitable for semi-continuous control.
NOTE Unless otherwise specified, gas volumes are in cubic metres at 273,15 K and 101,325 kPa.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
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 10715:1997, Natural gas — Sampling guidelines
ISO 12213-1:1997, Natural gas — Calculation of compression factor — Part 1: Introduction and guidelines
ISO 12213-2:1997, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-composition
analysis
ISO 12213-3:1997, Natural gas — Calculation of compression factor — Part 3: Calculation using physical
properties
3Principle
Determination of the quantity of hydrocarbon condensate which can be formed at a pressure (p) and a temperature
(T) by passing a representative sample of the gas through an apparatus where it is first brought to the pressure (p)
and then cooled to the temperature (T).
The temperature and pressure are selected according to the specific application (see annex A).
Prior to reducing the pressure of the sample of gas to that required for the determination, the gas is heated, so that,
after pressure reduction, the temperature is well above the dew-point temperature of the gas. Downstream of the
reducer, the sample is cooled isobarically in a cooling bath to the required measurement temperature.
The quantity of liquid accumulated during the measurement period is determined by either direct manual weighing of
the collected liquid or weighing of the condensate cyclone separator at the start and at the end of a measurement
period (Method A).
Alternatively, the quantity of liquid accumulated in a vertical measuring tube may be determined automatically (indirect
automatic weighing) by indication of the pressure difference caused by the liquid accumulated in a vertical measuring
tube.
4 Apparatus requirements
WARNING — The instrumentation used for this method shall comply with local legal regulations for
application in hazardous areas.
4.1 Measurement installation
The general arrangement is shown in Figure 1. Examples of the line-up of the apparatus are given in annex B.
4.1.1 Gas-line connecting tubes, made of stainless steel with an internal diameter ranging between 2 mm and
4mm.
If mist is present in the gas, all tubing up to the point where the mist is evaporated or separated shall have an
internal diameter compatible with that of the sample line (4.1.2).
4.1.2 Sample line, the length of which is kept to a minimum and temperature-controlled along its length to at
least the point where it enters the part of the installation where the measurement is made.
An example o
...
INTERNATIONAL ISO
STANDARD 6570
First edition
2001-06-15
Natural gas — Determination of potential
hydrocarbon liquid content — Gravimetric
methods
Gaz naturel — Détermination de la teneur en hydrocarbures liquides
potentiels — Méthodes gravimétriques
Reference number
©
ISO 2001
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
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 either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Principle.2
4 Apparatus requirements .2
4.1 Measurement installation.2
4.2 Check for correct installation operation .5
5 Sampling.10
5.1 General.10
5.2 Sampling conditions .10
5.3 Sample line.10
5.4 Direct sampling.10
5.5 Indirect sampling .10
6 Procedure .11
6.1 Determination of potential hydrocarbon liquid content.11
6.2 Determination of water formation .12
7 Expression of results .12
7.1 Method A — Manual weighing method.12
7.2 Method B — Indirect automatic method.14
8 Uncertainty of measurement .15
8.1 Achievable uncertainty .15
8.2 Gas leakage.15
8.3 Bath liquid .16
8.4 Wet gas .16
8.5 Condensate leakage .16
8.6 Variations in bath temperature and pressure in the gas/liquid cyclone separator .16
8.7 Premature condensation.16
9 Test report .16
Annex A (informative) Selection of measurement temperature and pressure.17
Annex B (informative) Examples of the line-up of the apparatus .18
Annex C (informative) Example of calibration of the differential pressure gauge for the indirect
automatic method — Method B.19
Annex D (informative) Example of an indirect automatic measurement — Method B.21
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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 6570 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee
SC 1, Analysis of natural gas.
This first edition cancels and replaces ISO 6570-1:1983 and ISO 6570-2:1984, which have been technically
revised.
Annexes A to D of this International Standard are given for information only.
iv © ISO 2001 – All rights reserved
Introduction
Under certain conditions, higher hydrocarbons present in natural gas or similar gases may condense and the
condensate formed can cause difficulties in the operation of gas transport and distribution systems.
Dew-point measurements, by condensation on a mirror, may give an indication of the conditions under which
condensation starts. However, these measurements give no further information about the amount of liquid to be
expected under operating conditions.
For proper operation of transport and distribution systems, a knowledge of the quantities of condensate formed as
a function of temperature and pressure is required. This knowledge is also required for the design of production
and treatment systems as well as for subsequent handling and disposal of the liquid.
The methods described in this International Standard are intended for the determination of the quantity of
hydrocarbon condensate formed from a natural gas or similar gas as a function of the temperature and pressure of
the gas.
Instruments based on different measurement principles can give a figure related to potential condensate content or
dew point. The dew point can only be determined by performing measurements at different temperatures followed by
extrapolation of the measurements to a potential hydrocarbon liquid content (� ) value of zero. The methods
PHLC
described in this International Standard can be used to calibrate such instruments.
INTERNATIONAL STANDARD ISO 6570:2001(E)
Natural gas — Determination of potential hydrocarbon liquid
content — Gravimetric methods
WARNING — The use of this International Standard may involve hazardous materials, operations and
equipment. This International Standard does not purport to address all of the safety problems associated
with its use. It is the responsibility of the user of this International Standard to establish appropriate safety
and health practices and to determine the applicability or regulatory limitations prior to use.
1 Scope
This International Standard describes the principles of, and general requirements for, two gravimetric methods for
the determination of the potential hydrocarbon liquid content of natural gas, or similar gas, at a given pressure and
temperature. Two methods are specified in this International Standard to determine the amount of condensate in a
sample gas:
� Method A: a manual weighing method;
� Method B: an indirect automatic weighing method based on the indication of the pressure difference caused by
the accumulation of condensate in a vertical tube.
The manual weighing method is a reference method for the indirect automatic method (Method B). The indirect
automatic method (Method B) is suitable for semi-continuous control.
NOTE Unless otherwise specified, gas volumes are in cubic metres at 273,15 K and 101,325 kPa.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
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 10715:1997, Natural gas — Sampling guidelines
ISO 12213-1:1997, Natural gas — Calculation of compression factor — Part 1: Introduction and guidelines
ISO 12213-2:1997, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-composition
analysis
ISO 12213-3:1997, Natural gas — Calculation of compression factor — Part 3: Calculation using physical
properties
3Principle
Determination of the quantity of hydrocarbon condensate which can be formed at a pressure (p) and a temperature
(T) by passing a representative sample of the gas through an apparatus where it is first brought to the pressure (p)
and then cooled to the temperature (T).
The temperature and pressure are selected according to the specific application (see annex A).
Prior to reducing the pressure of the sample of gas to that required for the determination, the gas is heated, so that,
after pressure reduction, the temperature is well above the dew-point temperature of the gas. Downstream of the
reducer, the sample is cooled isobarically in a cooling bath to the required measurement temperature.
The quantity of liquid accumulated during the measurement period is determined by either direct manual weighing of
the collected liquid or weighing of the condensate cyclone separator at the start and at the end of a measurement
period (Method A).
Alternatively, the quantity of liquid accumulated in a vertical measuring tube may be determined automatically (indirect
automatic weighing) by indication of the pressure difference caused by the liquid accumulated in a vertical measuring
tube.
4 Apparatus requirements
WARNING — The instrumentation used for this method shall comply with local legal regulations for
application in hazardous areas.
4.1 Measurement installation
The general arrangement is shown in Figure 1. Examples of the line-up of the apparatus are given in annex B.
4.1.1 Gas-line connecting tubes, made of stainless steel with an internal diameter ranging between 2 mm and
4mm.
If mist is present in the gas, all tubing up to the point where the mist is evaporated or separated shall have an
internal diameter compatible with that of the sample line (4.1.2).
4.1.2 Sample line, the length of which is kept to a minimum and temperature-controlled along its length to at
least the point where it enters the part of the installation where the measurement is made.
An example o
...
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