SIST EN ISO 10715:2023
(Main)Natural gas - Gas sampling (ISO 10715:2022)
Natural gas - Gas sampling (ISO 10715:2022)
This document gives means for ensuring that samples of natural gas and natural gas substitutes that are conveyed into transmission and distribution grids are representative of the mass to which they are allocated.
NOTE To ensure that a particular gas is taken into account in the standard, please see Annex A.
This document is applicable for sampling at sites and locations where interchangeability criteria, energy content and network entry conditions are measured and monitored and is particularly relevant at cross border and fiscal measurement stations. It serves as an important source for control applications in natural gas processing and the measurement of trace components.
This document is applicable to natural dry gas (single phase - typically gas transiting through natural gas pipelines) sampling only. On occasion a natural gas flow can have entrained liquid hydrocarbons. Attempting to sample a wet natural gas flow introduces the possibility of extra unspecified uncertainties in the resulting flow composition analysis. Sampling a wet gas (two or three phases) flow is outside the scope of this document.
This document does not apply to the safety issues associated with gas sampling.
Erdgas - Probenahme (ISO 10715:2022)
Dieses Dokument enthält Mittel, mit denen sichergestellt wird, dass Proben von Erdgas und Erdgasaustauschgas, das in Fernleitungs- und Verteilungsnetze geleitet wird, repräsentativ für den Gasstrom sind, dem sie zugeordnet sind.
ANMERKUNG Um sicherzustellen, dass ein bestimmtes Gas in der Norm Berücksichtigung findet, siehe Anhang A.
Dieses Dokument ist für die Probenahme an Standorten und Stellen anwendbar, an denen Austauschbarkeitskriterien, Energiegehalt und Netzeinspeisebedingungen gemessen und überwacht werden, und ist insbesondere an grenzüberschreitenden und abrechnungsrelevanten Messstellen maßgebend. Es dient als wichtige Quelle für Kontrollanwendungen in der Erdgasverarbeitung und für die Messung von Spurenbestandteilen.
Dieses Dokument ist nur für die Probenahme von trockenem Erdgas (einphasig — üblicherweise Gas, das durch Erdgasleitungen fließt) anwendbar. Gelegentlich kann ein Erdgasfluss mitgenommene flüssige Kohlenwasserstoffe enthalten. Der Versuch, einen feuchten Erdgasfluss zu beproben, führt möglicherweise zu zusätzlichen, nicht spezifizierten Unsicherheiten bei der Analyse der resultierenden Gasflusszusammensetzung. Die Probenahme aus einem feuchten Gasfluss (zwei- oder dreiphasig) liegt nicht im Anwendungsbereich dieses Dokuments.
Dieses Dokument ist nicht für die Sicherheitsfragen in Zusammenhang mit der Gasprobenahme anwendbar.
WARNUNG — Allgemeine Aspekte der Erdgasbeschaffenheit sind in ISO 13686 [1] ausführlich beschrieben. Möglicherweise deckt die Norm nicht alle Spurenbestandteile ab, deren Überwachung aus verschiedenen Gründen zunehmend notwendig ist.
Gaz naturel - Échantillonnage de gaz (ISO 10715:2022)
Zemeljski plin - Vzorčenje (ISO 10715:2022)
Ta dokument določa sredstva za zagotavljanje, da so vzorci zemeljskega plina in nadomestkov zemeljskega plina, ki se prenašajo v prenosna in distribucijska omrežja, reprezentativni za maso, ki so ji dodeljeni. OPOMBA: Ali je določen plin upoštevan v standardu, je mogoče preveriti v dodatku A. Ta dokument se uporablja za vzorčenje na mestih in lokacijah, kjer se merijo in spremljajo merila medsebojne zamenljivosti, vsebnost energije ter vstopni pogoji za omrežje. Še posebej je pomemben pri čezmejnih postajah in sistemih fiskalnega merjenja. Je pomemben vir za izvajanje nadzora pri predelavi zemeljskega plina in merjenju komponent v sledovih. Dokument se uporablja samo za vzorčenje suhega zemeljskega plina (enofaznega – običajno plina, ki teče po plinovodih za zemeljski plin). Zgodi se, da tok zemeljskega plina vsebuje tekoče ogljikovodike. Pri poskusu vzorčenja toka mokrega zemeljskega plina in analizi njegove sestave lahko pride do dodatnih nedefiniranih negotovosti. Vzorčenje toka mokrega plina (dvo- ali trifazni) ne spada na področje uporabe tega dokumenta. Dokument se ne navezuje na varnostna vprašanja, povezana z vzorčenjem plina.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-2023
Nadomešča:
SIST EN ISO 10715:2000
Zemeljski plin - Vzorčenje (ISO 10715:2022)
Natural gas - Gas sampling (ISO 10715:2022)
Erdgas - Probenahme (ISO 10715:2022)
Gaz naturel - Échantillonnage de gaz (ISO 10715:2022)
Ta slovenski standard je istoveten z: EN ISO 10715:2022
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 10715
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 75.060 Supersedes EN ISO 10715:2000
English Version
Natural gas - Gas sampling (ISO 10715:2022)
Gaz naturel - Échantillonnage de gaz (ISO 10715:2022) Erdgas - Probenahme (ISO 10715:2022)
This European Standard was approved by CEN on 7 July 2022.
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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10715:2022 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 10715:2022) has been prepared by Technical Committee ISO/TC 193 "Natural
gas" in collaboration with Technical Committee CEN/TC 238 “Test gases, test pressures, appliance
categories and gas appliance types” the secretariat of which is held by AFNOR.
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 April 2023, and conflicting national standards shall be
withdrawn at the latest by April 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 10715:2000.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 10715:2022 has been approved by CEN as EN ISO 10715:2022 without any modification.
INTERNATIONAL ISO
STANDARD 10715
Second edition
2022-10
Natural gas — Gas sampling
Gaz naturel — Échantillonnage de gaz
Reference number
ISO 10715:2022(E)
ISO 10715:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 10715:2022(E)
Contents Page
Foreword . vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety considerations . .4
5 Principles of sampling . .4
6 The concept of representative sample . 4
7 Types of sampling .5
7.1 Sampling method considerations . 5
7.2 Spot sampling . 6
7.2.1 General . 6
7.2.2 Fill-and-empty method . 6
7.2.3 Controlled-rate method . 7
7.2.4 Evacuated-cylinder method . 7
7.2.5 Helium pre-fill method . 7
7.2.6 Floating-piston cylinder method . 7
7.2.7 Single cavity sample cylinder . 7
7.2.8 Sampling frequency . 7
7.3 Incremental sampling (continuous or composite) . 9
7.3.1 General considerations . 9
7.3.2 Intervals . 9
7.3.3 System considerations . 9
7.3.4 Monitoring the filling process . 10
7.3.5 Cylinder tracking. 10
7.3.6 Overpressure protection. 10
7.4 Online or direct sampling . 10
7.4.1 General considerations . 10
7.4.2 Automatic drainage.12
7.4.3 Reducing the pressure.12
7.4.4 Inert-gas purging . 13
7.4.5 Safety/pressure relief valve . 13
7.4.6 Heating of sample line . 13
8 Sampling location . .13
8.1 General .13
8.2 Sampling place .13
8.2.1 General .13
8.2.2 Relevant gas . 14
8.2.3 Undisturbed gas . 14
8.2.4 Access . 14
8.3 Sampling position . 15
8.4 Sampling point . 15
9 Ideal implementation of gas sampling .16
9.1 General . 16
9.2 Gas sorption . 16
9.2.1 General . 16
9.2.2 Surface treatment . 17
9.2.3 Sorption considerations regarding sampling equipment . 17
9.2.4 Equilibrating of sampling equipment . 17
9.3 Materials used in sampling . . . 18
9.3.1 General considerations . 18
iii
ISO 10715:2022(E)
9.3.2 Steel grades . 19
9.3.3 Epoxy coatings . 19
9.3.4 Other polymers . 19
9.3.5 Rubbers . 19
9.3.6 Bimetallic corrosion . 19
9.4 Sample contamination . 19
9.4.1 Cleanliness . 19
9.4.2 Cleaning sampling systems . 19
9.4.3 Pre-charging of sample cylinders . 20
9.5 Sample condensation . 20
9.5.1 Temperature . 20
9.5.2 Pressure reduction and Joule Thomson cooling . 20
9.5.3 Condensation and revaporization . 22
9.6 Disturbance of the flow through the sampling system . 24
9.7 Delay time . 24
9.7.1 Direct sampling method . 24
9.7.2 Indirect sampling method . 25
10 Sampling equipment .26
10.1 General . 26
10.2 Probes . 27
10.2.1 General . 27
10.2.2 Straight-tube probe . 27
10.2.3 Probe regulator .28
10.2.4 Pitot probe .29
10.3 Tubings .30
10.3.1 Sampling and sample lines .30
10.3.2 Bypass constructions . 31
10.4 Filters, membranes and separators . 31
10.5 Valves and safety valves . 32
10.6 Fittings . 33
10.7 Flow monitoring and control . 33
10.8 Pressure reducers . 33
10.9 Pressure sensor/manometers.33
10.10 Heating devices . 33
10.11 Seals and lubricants .34
10.12 Sample containers or cylinders .34
10.12.1 General .34
10.12.2 Standard or single cavity cylinder . 35
10.12.3 Floating-piston cylinders or Constant Pressure cylinders . 35
10.13 Concentration devices .36
10.14 Number and sequence of equipment . 37
11 Verification of the system.38
12 Troubleshooting .39
Annex A (informative) Purposes of sampling, panel of compounds and information in the
sampling report .41
Annex B (informative) Procedures for sampling.42
Annex C (informative) Gas sorption effect: adsorption/desorption .49
Annex D (informative) Cleaning of steel sampling cylinders .50
Annex E (informative) Joule-Thomson cooling and phase behaviour .51
Annex F (informative) Vortex shedding and associated problems .54
Annex G (informative) Guidelines for the calculation of the residence time .58
Annex H (informative) Protocol for gas sampling system verification .66
iv
ISO 10715:2022(E)
Annex I (informative) Number of samples.68
Bibliography .70
v
ISO 10715:2022(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 of 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
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 193, Natural Gas, Subcommittee SC 1,
Natural gas analysis, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 238, Test gases, test pressures and categories of appliances, in accordance with the
Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 10715:1997), which has been technically
revised.
The main changes are as follows:
— This new edition has placed a significant relevance on regular service, maintenance and validation
of installed sample systems which previously have not been given proper attention. Sample systems,
or at least the fixed/installed portion of them, have all too often been installed and forgotten without
realization that through use they become more and more contaminated leading to distortions of the
composition of the gas being sampled.
— Introduction of new sampling devices.
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.
vi
ISO 10715:2022(E)
Introduction
The composition, quality, and properties of natural gas vary according to amongst others its source, level
of processing, natural mixing at interconnection points, storage facilities, blending stations, fluctuating
demand for some of its derivatives such as LPG (Liquefied Petroleum Gases), and increasingly the need
to transport unconventional and renewable gases in the same network etc.
The variations that occur are closely monitored and controlled to ensure safety of the general public
as well as operational staff, plant, equipment and the gas infrastructures in general. Additionally and
commercially critical the energy content of the gas differs with these variations and is very accurately
monitored for billing and fiscal purposes because of the very large sums of money involved.
The variations that occur can be best collectively grouped under the generic term “Gas Quality” which
is subsequently referred to as GQ in this document.
For monitoring and controlling GQ, samples are taken at many and various stages along the way and
analysed. Such samples are taken under many different process parameters with a need to always
ensure that any gas that is subsequently analysed for such monitoring purposes is truly representative
of the bulk.
Methods of measuring GQ are well specified in numerous ISO standards as are the means of calibrating
such measuring instruments, however all those measurements and calibrations are all but futile if the
samples used for making such measurements are not representative.
This document provides means to ensure sampling systems and sampling processes are designed,
located, installed, operated, and maintained such that samples obtained are representative of the bulk
to which they are attributed. It also specifies comprehensive information on the way that samples can
be contaminated, altered, modified or degraded and methods, means and procedures for ensuring that
the sample remains representative from the start of the sampling process to the point where the sample
is presented to the analytical device.
vii
INTERNATIONAL STANDARD ISO 10715:2022(E)
Natural gas — Gas sampling
[1]
WARNING — General quality aspects of natural gas are detailed in ISO 13686 . However,
it is possible that the standard does not cover all the trace constituents that are increasingly
necessary to monitor for various reasons.
1 Scope
This document gives means for ensuring that samples of natural gas and natural gas substitutes that
are conveyed into transmission and distribution grids are representative of the mass to which they are
allocated.
NOTE To ensure that a particular gas is taken into account in the standard, please see Annex A.
This document is applicable for sampling at sites and locations where interchangeability criteria, energy
content and network entry conditions are measured and monitored and is particularly relevant at cross
border and fiscal measurement stations. It serves as an important source for control applications in
natural gas processing and the measurement of trace components.
This document is applicable to natural dry gas (single phase - typically gas transiting through natural
gas pipelines) sampling only. On occasion a natural gas flow can have entrained liquid hydrocarbons.
Attempting to sample a wet natural gas flow introduces the possibility of extra unspecified uncertainties
in the resulting flow composition analysis. Sampling a wet gas (two or three phases) flow is outside the
scope of this document.
This document does not apply to the safety issues associated with gas sampling.
2 Normative references
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 14532, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions from ISO 14532 and the following apply.
ISO and IEC maintain terminological 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
absorption
extraction of one or more components from a mixture of gases when brought into contact with a liquid
Note 1 to entry: The assimilation or extraction process causes (or is accompanied by) a physical or chemical
change, or both, in the sorbent material.
Note 2 to entry: The gaseous components are retained by capillary, osmotic, chemical, or solvent action.
EXAMPLE Removal of water from natural gas using glycol.
ISO 10715:2022(E)
[SOURCE: ISO 14532:2014, 2.2.2.6]
3.2
adsorption
retention, by physical or chemical forces of gas molecules, dissolved substances, or liquids by the
surfaces of solids or liquids with which they are in contact
Note 1 to entry: For example, retention of methane by carbon.
[SOURCE: ISO 14532:2014, 2.2.2.7]
3.3
contaminant
constituent in very low levels, such as particulates, glycol, compressor oil, etc., that are assumed to be
intrusive and not part of the gas to be sampled
Note 1 to entry: Such contaminants are generally harmful to the analytical equipment and if they enter the
sampling process they need to be removed from the sample before it enters the analyser. However, once the
contaminants enter the sampling process they continue to influence any following sample that come into contact
with them. Over a period of time the accumulation of contamination in the sampling system can have a profound
effect on the sample such that it is no longer representative of the mass.
Note 2 to entry: Contaminants are not to be confused with trace components that are inherent to the gas to be
sampled.
3.4
desorption
removal of a sorbed substance by the reverse process of adsorption or absorption
Note 1 to entry: From solution in a liquid phase for example.
[SOURCE: ISO 14532:2014, 2.2.2.8, modified — Note 1 to entry added.]
3.5
direct sampling
sampling in situations where there is a direct connection between the natural gas to be sampled and
the analytical unit
3.6
floating-piston cylinder
container which has a moving piston separating the sample from a buffer gas, where the pressures are
in balance on both sides of the piston
3.7
gas sorption effect
physical process whereby some gases are adsorbed onto or desorbed from the surfaces of a solid
without transformation of the molecules
Note 1 to entry: The force of attraction between some gases and solids is purely physical and depends on the
nature of the participating material. Natural gas can contain several components that exhibit strong sorption
effects. Special care should be taken when determining trace concentrations such as heavy hydrocarbons, water,
sulfur compounds, mercury and hydrogen.
[SOURCE: ISO 14532:2014, 2.3.4.6]
3.8
high-pressure natural gas
natural gas with a pressure exceeding 0,2 MPa
3.9
hydrocarbon dew point
temperature, at a given pressure, at which hydrocarbon vapour condensation begins
ISO 10715:2022(E)
3.10
incremental sampler
sampler which accumulates a series of spot samples into one composite sample
3.11
indirect sampling
sampling in situations where there is no direct connection between the natural gas to be sampled and
the analytical unit
3.12
liquid separator
unit, in the sample line, used to collect liquid fall-out
3.13
purging time
period of time during which a sample purges a piece of equipment
3.14
representative sample
sample having the same composition as the natural gas it is attributed to, when the latter is considered
as a homogeneous whole
[SOURCE: ISO 14532:2014, 2.3.4.2]
3.15
residence time
time it takes for a sample to flow through a piece of equipment
3.16
retrograde condensation
production of a liquid phase of heavy hydrocarbons at a particular pressure and temperature where, at
that same temperature, the gas stays in a single phase at a higher pressure as well as at a lower pressure
Note 1 to entry: Retrograde behaviour describes the non-ideal phase properties of hydrocarbon gas mixtures,
such as natural gas.
3.17
sample container
container for collecting the gas sample when indirect sampling is necessary
3.18
sample line
line provided to transfer a sample of the gas from the sampling point (3.21) to the sampling device or the
analytical unit
Note 1 to entry: Devices necessary to prepare the sample for transportation and analysis (conditioning unit) can
be part of it.
3.19
sample probe
device inserted into the gas source, used to extract a sample and to which a sample line (3.18) is
connected
3.20
sampling place
whereabouts along the gas pipeline or on the process plant where the sample probe (3.19) is located
3.21
sampling point
exact point in space defined by the sampling place (3.20), the sampling position (3.22) and by the location
of the inlet on the sample probe (3.19)
ISO 10715:2022(E)
3.22
sampling position
location within the cross-sectional area of the gas pipeline or process plant at the sampling place from
where a sample is taken
3.23
spot sample
sample of specified volume taken at a specified place at a specified time from a stream of gas
3.24
trace component
component present at very low levels
Note 1 to entry: Trace components generally include hydrocarbons or groups of hydrocarbons above n-pentane
and other components listed in ISO 14532.
3.26
wetted surface
surface of the material in contact with the sampled gas
4 Safety considerations
The use of this document can involve working with high pressure flammable gases and other hazardous
materials which can be located in areas designated as hazardous (potentially explosive and or toxic
atmospheres). This document does not address the safety issues associated with such situations. It
is the user’s responsibility to establish appropriate design rules, installation, operating, testing and
maintenance procedures for pressurized equipment, equipment located in potentially hazardous areas,
the control, handling and transportation of substances potentially hazardous to health, etc.
International and national regulations on safety requirements should be followed closely and carry
more weight than this document.
5 Principles of sampling
Natural gas sampling is the process of acquiring a sample from a source of interest, conditioning the
sample (where necessary) and delivering the sample to an analytical instrument, either directly or
indirectly via a vessel or other transport medium.
The methods and equipment for each of these steps are described within this document.
The purpose of the sampling system is to ensure that the sample acquired is representative of the
source gas desired and that in the process of delivering the sample to the analytical instrument the
chemical and physical state remain unchanged, even on a molecular level.
Considering the equipment is relied on to fulfil this purpose for many years of operation, careful
consideration should be applied to the design (considering application-specific conditions and
measurement objectives), manufacturing, operation, maintenance and performance evaluation of the
system.
6 The concept of representative sample
In order to show that any information gained from a sample of natural gas is truly representative of the
whole quantity to which the information is to be attributed we use the term “representative sample”
A representative sample is established by two main criteria:
a) The sample is not altered in any way, or more realistically in any avoidable way, during the process
of collecting, handling, containing or preparing the sample for analysis or measurement. The
condition of the sample being the same in composition and phase -absolute or essential sameness
ISO 10715:2022(E)
as the mass from which it was taken for the quality/analyte under consideration - is considered as
being identical.
b) The sample is taken at a sample point where we can be sure that it is actually from the bulk to
which the information is to be applied at a known time or time period. This requires a matching in
time or a synchronization of analytical results to the mass. This is considered as being pertinent.
7 Types of sampling
7.1 Sampling method considerations
The main function of sampling is to take an adequate sample that is representative of the gas.
The main distinction in sampling is between direct and indirect sampling methods. In the direct
sampling method, the sample is drawn from a stream and directly transferred to the analytical unit.
In the indirect sampling method, the sample is stored in a sample container before it is transferred
to the analytical unit. The main classifications of the indirect sampling method are spot sampling or
[17]
incremental sampling. Incremental sampling regarding regasified LNG is described in ISO 8943 .
Key
A sampling
B1 direct
B2 indirect
C1 spot
C2 incremental
D1 time
D2 flow
Figure 1 — Survey of direct and indirect sampling methods
The information needed from the analysis of natural gas falls into two basic categories: averaged and
limit values.
— Averaged values:
A typical example is the calorific value. Custody transfer requires the time- or flow-averaged calorific
value. Commercial agreements determine the period and method of averaging.
— Limit values:
ISO 10715:2022(E)
Most gas custody transfer contracts contain specification limits on composition or on gas properties.
Direct sampling can be applied, but often the requirements are such that also indirect sampling has to
be applied.
7.2 Spot sampling
7.2.1 General
This clause specifies a method of indirect sampling in which a suitable container is filled with the
sample. The sample is subsequently transported to the place of analysis.
Spot sampling is a form of sampling that is representative of what is in the pipeline at the moment that
the sample is being taken. Spot sampling may be used for well or feed assessment, periodic stream
assessment, result verification, process verification, trouble shooting and auditing purposes.
Spot sampling is a form of sampling that is taken from a single location and a single point in time and
provides a sample of what was in the pipeline when the technician extracted the sample.
The interval between samples should be specified by the user, based on safety or process criticality of
the results and stability of the gas quality (see 7.2.8).
The sample is extracted by utilizing one of several approved methods for taking spot samples, such as:
the fill and empty method, the Helium pop method, the continuous purge, constant pressure method or
another proven and tested method of extraction. Most samples are gathered in a standard, single cavity
sample cylinder or a constant pressure piston style sample cylinder.
While valuable information can be gathered by this method, it shall always be noted that the sample
represents what was present at the time of sampling. It is not representative of the sample location for
the next week or month, unless it is from a single gas well that has a long history of producing the same
gas and gas content. It is worthy to note that an older field begins to get richer and richer near the end
of its life. The gas quality could stay the same for 10 years and then begin to change near the end of its
field production life.
Annex B
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