ISO/TR 14749:2016

TECHNICAL ISO/TR
REPORT 14749
First edition
2016-05-15
Natural gas — Online gas
chromatograph for upstream area
Gaz naturels — Chromatographe en phase gazeuse en ligne pour
zone amont
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Principle of measurement . 1
2.1 General . 1
2.2 Gas composition . 1
3 Sampling and conditioning . 3
4 Online gas chromatograph selection guideline . 6
5 Calibration guidelines . 7
5.1 Calibration procedure . 7
5.1.1 General. 7
5.1.2 Calibration . 7
5.1.3 Calibration frequency . 7
5.2 Calibration gases . 8
5.3 Chromatogram verification . 8
5.3.1 Response Factor (RF) . 8
5.3.2 Retention Time (RT) . 8
6 Verification procedure . 8
6.1 General . 8
6.2 Visual inspection of Sample system . 9
6.3 Visual inspection of analyser . 9
6.4 Carrier Gas . 9
6.5 Calibration Gas . 9
6.6 GC verification . 9
7 Maintenance and Corrective maintenance .10
7.1 Preventive maintenance .10
7.2 Corrective maintenance .10
8 Alarm and diagnostic .10
9 Repeatability and Reproducibility .12
9.1 Repeatability .12
9.2 Reproducibility .12
10 Data handling during GC failure .12
11 Quality Control of analysis data .13
Annex A (informative) Example, comparison between duty and backup GC .14
Annex B (informative) Example, Typical chromatogram .16
Annex C (informative) Example: Analysis result .18
Bibliography .19
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. 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. 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 on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 193, Natural gas, Subcommittee SC 3,
Upstream area.
iv © ISO 2016 – All rights reserved

Introduction
Online Gas Chromatograph (GC) is widely used to determine hydrocarbon components in natural gas
because of its “Real time” measurement and ease of use. It has become a powerful tool for both custody
transfer and upstream process gas monitoring. Especially for the custody transfer which the calorific
value and others gas properties such as, relative density, compressibility factor, etc. are needed for
energy determination. Therefore, accuracy and reliability of the equipment are crucial.
With proper maintenance and handling, GC can provide an accurate result with a minimum manpower
as it analyzes and provides results continuously. With technology today, the unit can do auto-calibration,
alarm setting, diagnostic, troubleshooting and configuring through Human Machine Interface (HMI).
Its outputs can be linked directly with Flow computer, Distributed Control System (DCS) or any remote
personal computer (PC).
The Natural Gas in upstream petroleum industry is normally wet. Then this Technical Report provides
recommended application to handling GC focus on design, selection, operation, maintenance and
verification of GC and its peripheral. The purpose is to provide the whole process to proper handling
the GC until getting the accurate and reliable results. It is also included the sampling system to get the
representative sample, data verification, alarm, diagnostic and troubleshooting including how to deal
with the data in case of being used for custody transfer purpose. Some acceptance criteria are also
identified in this paper based on our historical record and performance of the equipment.
TECHNICAL REPORT ISO/TR 14749:2016(E)
Natural gas — Online gas chromatograph for upstream area
1 Scope
This Technical Report concerns the determination of hydrocarbon components up to C7+ in natural
gas in upstream petroleum industry, which describes the principle of operation of GC and provides
guidelines for selection, evaluation, and factors impacting upon its performance such as sample probe,
sample conditioning, installation, operation and troubleshooting.
2 Principle of measurement
2.1 General
The GC is a technique for separating and analysing compounds that can be vaporized without
decomposition in a continuous and automatic manner of sample injection, separation, data integration
and reporting. A precise volume of sample gas is injected into the column which contains a stationary
phase (packing) that is either an active solid (adsorption partition) or an inert solid support that is
coated with a liquid phase (absorption partitioning). The gas is moved through the column by means
of a mobile phase (carrier gas). Selective retention of the components of the sample takes place in
the column and causes each component to move through the column at a different rate. This action
separates the sample into its gaseous constituents.
A detector detects the elution of component from the column and produces electrical outputs
proportional to the concentration of each component. Output from the detector are amplified in the
electronics, then transmitted to the controller for further processing.
2.2 Gas composition
Natural gas is composed primarily of methane with smaller amounts of higher hydrocarbons and of
non combustible gases. Major, minor and trace components are as indicated in Tables 1, 2 and 3:
Table 1 — Major components
Component Units
Methane mole %
Ethane mole %
Propane mole %
Butanes mole %
Pentanes mole %
Hexanes mole %
Heptanes plus mole %
Nitrogen mole %
Carbon dioxide mole %
Table 2 — Minor component
Component Units
Hydrogen mole %
Oxygen mole %
Carbon monoxide mole %
Helium mole %
Table 3 — Trace component
Component Units
Hydrogen sulfide mg/m
Mercaptan sulfur mg/m
Dialkyl (di) sulfide mg/m
Carbonyl sulfide mg/m
Total sulfur mg/m
Figure 1 — Online Gas Chromatograph Functional Block Diagram
2 © ISO 2016 – All rights reserved

Figure 2 — Online Gas Chromatograph Equipment Diagram
Output from the controller is normally linked to flow computer, DCS, remote personal computer (PC) or
a printer. Connection between the GC Controller and others can be accomplished via a direct seri
...