ISO 10101-1:2022

Natural gas - Determination of water by the Karl Fischer method - Part 1: General requirements

This document specifies general requirements for the determination of water in natural gas using the Karl Fischer method (see Reference [1]). ISO 10101-2 and ISO 10101-3 specify two individual methods of determination, a titration procedure and a coulometric procedure, respectively.

Gaz naturel — Dosage de l'eau par la méthode de Karl Fischer — Partie 1: Exigences générales

General Information

• Status: Published
• Publication Date: 23-Aug-2022
• ICS: 75.060 - Natural gas
• Technical Committee: ISO/TC 193/SC 1 - Analysis of natural gas
• Drafting Committee: ISO/TC 193/SC 1/WG 21 - Revision of ISO 10101
• Current Stage: 6060 - International Standard published
• Start Date: 24-Aug-2022
• Due Date: 03-Dec-2022
• Completion Date: 24-Aug-2022

Relations

• Consolidated By: ISO 2440:2019 - Flexible and rigid cellular polymeric materials - Accelerated ageing tests
• Effective Date: 06-Jun-2022
• Revises: ISO 10101-1:1993 - Natural gas - Determination of water by the Karl Fischer method - Part 1: Introduction
• Effective Date: 04-Nov-2015

Overview

ISO 10101-1:2022 establishes the general requirements for determining water content in natural gas using the Karl Fischer method. This internationally recognized standard enhances measurement accuracy by specifying fundamental principles, sampling procedures, and uncertainty evaluation for water determination. It serves as Part 1 of a series, complemented by ISO 10101-2 and ISO 10101-3 that detail volumetric and coulometric procedures, respectively.

The Karl Fischer method offers a selective, rapid, and precise technique for moisture analysis in natural gas - essential for ensuring gas quality, safety, and efficiency in processing, transport, and end-use applications.

Key Topics

• Scope and Application: Defines the purpose of determining water concentration in natural gas via Karl Fischer titration, applicable to both volumetric and coulometric techniques.

• Principle of Method:

  • Based on the stoichiometric reaction of water with iodine and sulfur dioxide in a methanol solution.
  • Water quantity is derived from iodine consumption, measured either by titration (volumetric) or electrochemical generation of iodine (coulometric).
  • Volumetric titration suits water amounts from 1 mg to 100 mg; coulometric titration targets smaller amounts from 10 µg to 10 mg.

• Chemical Reactions and Interferences:

  • Detailed key reaction mechanisms and the impact of interfering gases like hydrogen sulfide and mercaptans, with correction formulas for interference mitigation.
  • Guidance on identifying and quantifying interfering sulfur compounds to ensure precise water measurement.

• Sampling Requirements:

  • Highlights the necessity of maintaining sample integrity by keeping gas temperature above dew point and using inert materials.
  • Recommends sampling procedures aligned with ISO 10715 to prevent moisture loss or contamination.

• Measurement Uncertainty:

  • Emphasizes estimating measurement uncertainty using interlaboratory comparisons (ISO 5725-2) and evaluation guidelines (ISO 21748).
  • Suggests reporting expanded uncertainty with a coverage factor k=2 for reliable results.
  • Incorporates the importance of including sampling uncertainty in the total uncertainty budget.

Applications

• Natural Gas Industry: Monitoring and controlling moisture levels to prevent pipeline corrosion, hydrate formation, and equipment damage.

• Gas Quality Assurance: Ensuring compliance with gas specifications for both transmission companies and end users.

• Laboratory Analysis: Development of standardized procedures for routine moisture testing in natural gas samples.

• Environmental and Safety Compliance: Moisture determination to assess gas safety parameters and reduce risks associated with impurities.

• Process Optimization: Utilizing accurate water content data to improve gas processing operations and efficiency.

Related Standards

• ISO 10101-2: Specifies the volumetric titration procedure for water determination in natural gas.

• ISO 10101-3: Details the coulometric titration method adapted for low water content measurements.

• ISO 10715: Provides general guidelines for natural gas sampling essential for water analysis.

• ISO 14532: Natural gas vocabulary ensuring consistent terminology in moisture analysis and related testing.

• ISO 5725-2: Establishes protocols for evaluating repeatability and reproducibility of measurement methods.

• ISO 21748: Offers guidance on using repeatability and reproducibility data to estimate measurement uncertainty.

• ISO 19739: Covers determination of sulfur compounds in natural gas, relevant for interference correction.

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Keywords: ISO 10101-1, natural gas, water determination, Karl Fischer method, moisture analysis, volumetric titration, coulometric titration, sampling, measurement uncertainty, gas quality, sulfur compound interference.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10101-1
Second edition
2022-08
Natural gas — Determination of water
by the Karl Fischer method —
Part 1:
General requirements
Gaz naturel — Dosage de l'eau par la méthode de Karl Fischer —
Partie 1: Exigences générales
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 General . 1
4.2 Principle of the titration method . 1
4.3 Principle of the coulometric method . 2
5 Reactions and interferences .2
6 Sampling . 3
7 Measurement uncertainty .3
Bibliography . 4
iii
Foreword
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 193, Natural Gas, Subcommittee SC 1,
Analysis of natural gas, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 238, Test gases, test pressures, appliance categories and gas appliance types,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 10101-1:1993), which has been technically
revised.
The main changes are as follows:
— Clause 2 and Bibliography were revised;
— New fixed structure numbering inserted.
A list of all parts in the ISO 10101 series can be found on the ISO website.
iv
Introduction
Water vapour may be present in natural gas due to, for example, natural occurrence in the well
production stream, the storage of gas in underground reservoirs, transmission or distribution through
mains containing moisture or other reasons.
The Karl Fischer method for the determination of moisture has several practical advantages compared
to other methods for moisture determination, such as accuracy, speed and selectivity.
The Karl Fischer method is selective for water, because the titration reaction itself consumes water.
The Karl Fischer (KF) titration can be divided into two basic techniques depending on the application
range – volumetric and coulometric KF titration. The two analysis techniques differ in the mode of
iodine addition or generation.
KF titration is essentially based on the Bunsen reaction used for the determination of sulphur dioxide
in aqueous solution:
22HO++SO IH→+SO HI
22 22 4
If an excess of sulphur dioxide with simultaneous neutralization of the sulphuric acid formed shift the
reaction equilibrium to the right, the Bunsen reaction can also be used for the determination of water.
Karl Fischer used pyridine as (neutralization) base, thus developing the classical KF reagent. This was
[9]
a solution of iodine and sulphur dioxide in a solvent mixture of pyridine and methanol . The fact that
the pyridine contained in the reagent has a strong unpleasant odour and toxicity and the reaction
[9]
runs stoichiometrically only within a certain pH range led to the revision of the KF reagents . Scholz
formulated the following KF reaction based on imidazole:
CH OH+SO+RN→[]RNHSOCH
32 33
where RN = Base.
HO+I +R[]NH SO CH +2RN→[]RNHSOCH+2R[]NH I
22 33 43
Volumetric KF titration is preferably used for the determination of large amounts of water in the range
[10]
of 1 mg to 100 mg
...