EN ISO 10715:2000
(Main)Natural gas - Sampling guidelines (ISO 10715:1997)
Natural gas - Sampling guidelines (ISO 10715:1997)
Erdgas - Probenahmerichtlinien (ISO 10715:1997)
Zweck dieser Unterlage ist es, kurze Richtlinien für eine einwandfreie Entnahme, Konditionierung und Handhabung repräsentativer Proben aufbereiteter Ergasströme zu geben. Sie enthält außerdem Richtlinien zu Probenahmestrategie, Anordnung der Probenahmestelle sowie der Handhabung und Auslegung von Probenahmeeinrichtungen. Sie behandelt Probenahmesysteme für Einzelproben, Sammelproben (Durchschnittsproben) und für die kontinuierliche Probenahme.
Gaz naturel - Lignes directrices pour l'échantillonnage (ISO 10715:1997)
La présente Norme internationale fournit des lignes directrices concises pour l'utilisation en vue du prélèvement, du conditionnement et de la manipulation d'échantillons représentatifs de gaz naturel traité. Elle fixe également les critères en termes de stratégie d'échantillonnage, d'emplacement de la prise de gaz et de manipulation et conception de l'équipement d'échantillonnage. La présente Norme internationale traite des systèmes d'échantillonnage par points, composites (par prélèvement) et continus. Elle examine également certains constituants des flux gazeux, tels que l'oxygène, l'hydrogène sulfuré, l'air, l'azote et le dioxyde de carbone. Le cas échéant, toute trace de liquide, tel que le glycol et l'huile provenant du compresseur, est considérée comme gênante et distincte du gaz devant être échantillonné. Son élimination est souhaitable, afin de protéger l'équipement d'échantillonnage et d'analyse de toute contamination. La présente Norme internationale peut être utilisée pour les systèmes de mesure de transfert surveillé et les systèmes de mesure de répartition.
Zemeljski plin - Smernice za vzorčenje (ISO 10715:1997)
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2000
=HPHOMVNLSOLQ6PHUQLFH]DY]RUþHQMH ,62
Natural gas - Sampling guidelines (ISO 10715:1997)
Erdgas - Probenahmerichtlinien (ISO 10715:1997)
Gaz naturel - Lignes directrices pour l'échantillonnage (ISO 10715:1997)
Ta slovenski standard je istoveten z: EN ISO 10715:2000
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL
IS0
STANDARD
First edition
1997-06-01
Natural gas - Sampling guidelines
Gaz na furel - Lignes directrices pour khantillonnage
Reference number
IS0 10715:1997(E)
IS0 10715:1997(E)
Contents
1 Scope . 1
2 Definitions . 1
3 Principles of sampling . 3
4 Safety precautions . 5
5 Technical considerations . 7
6 Materials used in sampling . 10
7 General preparation of equipment . 11
8 Sampling equipment . 12
9 Spot sampling . 18
10 Direct sampling .
11 Incremental sampling .
Annexes
A Use of a block valve in direct sampling . 23
B Cleaning of steel sampling cylinders . 25
C Procedure for low-pressure sampling into glass cylinders . 26
D Procedure for sampling by the fill-and-empty method . 28
E Procedure for sampling by the controlled-rate method . 30
............................................................................. 32
F Procedure for sampling by the evacuated-cylinder method
........................................................................................
G Guidelines for the calculation of the residence time 34
H Student’s f-table . 38
J Bibliography . 39
0 IS0 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
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Internet: central @? iso.ch
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Printed in Switzerland
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0 IS0
IS0 10715:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 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 IS0 IQ715 was prepared by Technical Committee lSO/TC 193, Natural gas, Subcomittee
SC 1, Analysis of natural gas.
Annexes A to J of this International Standard are for information only.
0 IS0
IS0 10715:1997(E)
Introduction
This International Standard provides guidance on all aspects of the sampling of processed natural gas. Unless
otherwise stated, all pressures up to 15 MPa in this International Standard are given as gauge pressures.
The determination of the composition and the properties of the gas is highly dependent on the sampling technique.
Also of great importance are the design, construction, installation and maintenance of the sampling system as well
as the conditions of sample transfer and transport.
These guidelines cover sampling strategy, details of sampling methods, the choice of sampling method and
sampling equipment.
This document is intended for use in sampling is not described
those cases where as part of the analytical
procedure.
This document concentrates on sampling systems and procedures. Analyses from the samples collected using
these systems and procedures may be utilized in many different ways, including calculations to determine the
calorific value of the gas stream, identification of contaminants contained in the gas stream, and compositional
information to determine whether or not the stream meets contractual specifications.
iv
IS0 10715:1997(E)
INTERNATIONAL STANDARD o IS0
Natural gas - Sampling guidelines
WARNING - The use of this International Standard may involve hazardous materials, operations and
equipment. This standard does not purport to address all of the safety problems associated with its use. It
is the responsibility of the user of this standard to establish appropriate safety and health practices and
determine the applicability or regulatory limitations prior to use.
All sampling activities shall comply with local safety regulations.
1 Scope
The purpose of this document is to provide concise guidelines for the collection, conditioning and handling of
representative samples of processed natural gas streams. It also contains guidelines for sampling strategy, probe
location and the handling and design of sampling equipment.
It considers spot, composite (incremental) and continuous sampling systems.
This document gives consideration to constituents such as oxygen, hydrogen sulfide, air, nitrogen and carbon
dioxide in the gas stream.
This document does not include sampling of liquid streams or streams with multiphase flow.
Traces of liquid, such as glycol and compressor oil, if present, are assumed to be intrusive and not a part of the gas
to be sampled. Their removal is desirable to protect the sampling and analytical equipment from contamination.
This document can be used for custody transfer measurement systems and allocation measurement systems.
2 Definitions
For the purposes of this International Standard, the following definitions apply:
direct sampling:
Sampling in situations where there is a direct connection between the natura ,I gas to be sampled and the analytica I
unit.
2.2 floating-piston cylinder:
A container which has a moving piston separating the sample from a buffer gas. The pressures are in balance on
both sides of the piston.
2.3 flow-proportional incremental sampler:
A sampler which collects gas over a period of time and at a rate that is proportional to the flow rate in the sampled
pipeline.
2.4 - high-pressure natural gas:
Natural gas with a pressure exceeding 0,2 MPa.
NOTE - The maximum for this International Standard is 15 MPa.
0 IS0
IS0 10715:1997(E)
2.5 hydrocarbon dew point:
The temperature, at a given pressure, at which hydrocarbon vapour condensation begins.
2.6 incremental sampler:
A sampler which accumulates a series of spot samples into one composite sample.
2.7 indirect sampling:
Sampling in situations where there is no direct connection between the natural gas to be sampled and the analytical
unit.
2.8 liquid separator:
A unit, in the sample line, used to collect liquid fall-out.
2.9 low-pressure natural gas:
Natural gas having a pressure between 0 and 0,2 MPa.
2.10 purging time:
The period of time during which a sample purges a piece of equipment.
2.11 representative sample:
A sample having the same composition as the natural gas sampled when the latter is considered as a
homogeneous whole.
2.12 residence time:
The time it takes for a sample to flow through a piece of equipment.
2.13 retrograde condensation:
Retrograde behaviour describes the non-ideal phase properties of hydrocarbon gas mixtures, such as natural gas.
Retrograde condensation is the 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 - See also 5.2.
2.14 sample container:
A container for collecting the gas sample when indirect sampling is necessary.
2.15 sample line:
A line provided to transfer a sample of the gas to the sampling point. It may include devices which are necessary to
prepare the sample for transportation and analysis.
2.16 sample probe:
A device inserted into the gas line to be sampled and to which a sample line is connected.
2.17 sampling point:
A point in the gas stream where a representative sample can be collected.
2.18 spot sample:
A sample of specified volume taken at a specified place at a specified time from a stream of gas.
2.19 transfer line:
A line provided to carry the sample to be analysed from the sample point to the analytical unit.
2.20 water dew point:
The temperature, at a given pressure, at which water vapour condensation begins
/.
0 IS0 IS0 10715: 1997(E)
3 Principles of sampling
3.1 Sampling methods
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 before it is transferred to the analytical unit.
The main classifications of the indirect sampling method are spot sampling and incremental sampling.
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.
i
3.1 .I 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.
3.1.2 Limit values
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.
3.2 Sampling frequency
This subclause gives guidelines for the establishment of the sampling frequency. Mostly the sampling frequency is a
matter of common sense. Information on the properties of the gas stream in the past and about expected
(systematic) future changes determines the sampling frequency.
Generally, pipeline gas composition will have daily, weekly, monthly, semi-annual and seasonal variations.
Compositional variations will also occur because of gas treatment equipment and reservoir changes. All of these
environmental and operational considerations shall be taken into account when selecting a sampling interval.
The statistical approach in this paragraph is only intended to support the common-sense approach.
In this context, the required sampling frequency is the number of samples to be taken in a certain period of time in
order to obtain meaningful results.
0 IS0
IS0 10715:1997(E)
The formula for calculating the number of samples is:
I
-
n* =,Xj
where
d is the error margin required;
n is the number of samples;
is the standard deviation;
S
f is Student’s f-factor (see table H.1 in annex H).
This equation shall be solved by iteration: an initial value of f is estimated, and used to calculate a revised value of
n, which is used, in turn, to give a new value of t. The error margin, the number of samples and the standard
deviation shall be taken over the same period of time.
3.2.1 Error margin
There are two different cases of error margins. One case is related to the determination of averaged values. In most
custody transfer contracts, these values are given as an indication of the accuracy.
The other is related to the determination of limit values. Custody trans
...
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