ASTM D7166-23

Standard Practice for Total Sulfur Analyzer Based On-line/At-line for Sulfur Content of Gaseous Fuels

SIGNIFICANCE AND USE
5.1 On-line, at-line, in-line and other near-real time monitoring systems that measure fuel gas characteristics such as the total sulfur content are prevalent in the natural gas and fuel gas industries. The installation and operation of particular systems vary on the specific objectives, contractual obligations, process type, regulatory requirements, and internal performance requirements needed by the user. This protocol is intended to provide guidelines for standardized start-up procedures, operating procedures, and quality assurance practices for on-line, at-line, in-line and other near-real time total sulfur monitoring systems.
SCOPE
1.1 This practice is for the determination of total sulfur from gas phase sulfur-containing compounds in high methane or hydrogen content gaseous fuels using on-line/at-line instrumentation.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 75.160.30 - Gaseous fuels
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.12 - On-Line/At-Line Analysis of Gaseous Fuels

Relations

• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D6122-23 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, Field and Laboratory Infrared Spectrophotometer, and Raman Spectrometer Based Analyzer Systems
• Effective Date: 01-Jul-2023
• Refers: ASTM D4150-19 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 15-Dec-2019
• Refers: ASTM D5453-19a - Standard Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
• Effective Date: 01-Jul-2019
• Refers: ASTM D6122-19b - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jun-2019
• Refers: ASTM D6122-19a - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-May-2019
• Refers: ASTM D6122-19 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jan-2019
• Refers: ASTM D6122-18 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jul-2018
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D4150-08(2016) - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 01-Jul-2016
• Refers: ASTM D5453-16 - Standard Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
• Effective Date: 15-Apr-2016
• Refers: ASTM D5287-08(2015) - Standard Practice for Automatic Sampling of Gaseous Fuels (Withdrawn 2024)
• Effective Date: 01-Jun-2015
• Refers: ASTM D3764-15 - Standard Practice for Validation of the Performance of Process Stream Analyzer Systems
• Effective Date: 01-Apr-2015

Overview

ASTM D7166-23 is the standard practice developed by ASTM International for the determination of total sulfur content in high methane or hydrogen content gaseous fuels using on-line or at-line sulfur analyzer systems. This standard provides comprehensive guidelines for the installation, start-up, operation, and quality assurance of on-line, at-line, in-line, or other near-real-time measurement systems used in the monitoring of fuel gas characteristics, specifically total sulfur levels. The standard addresses the need for accurate real-time monitoring in the natural gas and fuel gas industries to comply with regulatory requirements, contractual obligations, and internal performance standards.

Key Topics

• Scope and Application

  • Applies to measuring total sulfur from volatile sulfur-containing compounds in gaseous fuels, particularly those with high methane or hydrogen content.
  • Focuses on the use of on-line and at-line instrumentation for rapid and reliable determination of total sulfur.
  • Specifies that all measurements are to be made using SI units.

• Sampling and Instrumentation

  • Outlines the critical importance of proper sample extraction, handling, and conditioning for representative sulfur analysis.
  • Stresses the use of inert or properly passivated materials in all sample contact components.
  • Recommends heat tracing and filtration to maintain the gas phase and remove particulate matter.

• Analyzer and Detection Systems

  • Describes a variety of sulfur detection technologies suitable for total sulfur analyzers, including:
    • Chemiluminescence
    • Microcoulometry
    • Electrochemical methods
    • Lead acetate
    • Titration (e.g., barium chloride)
    • Ultraviolet fluorescence
  • Emphasizes the need for control of carrier and detector gas flow rates for consistent analytical performance.

• Calibration and Quality Assurance

  • Provides detailed protocols for start-up procedures, calibration using certified gas mixtures or permeation devices, and ongoing maintenance.
  • Recommends periodic performance tests, including system blank tests, calibration error checks, linearity assessments, and drift tests.
  • Highlights the importance of standard operating procedures (SOPs) and comprehensive maintenance logs.

Applications

ASTM D7166-23 is widely applied in industries where continuous monitoring of total sulfur in gaseous fuels is critical. Key applications include:

• Natural Gas Processing and Transmission

  • Ensures compliance with regulatory sulfur limits and contractual custody transfer agreements.
  • Enables real-time process control to mitigate corrosion and protect downstream equipment.

• Hydrogen Production and Distribution

  • Supports purity monitoring to prevent catalyst poisoning and maintain product quality.

• Refineries and Petrochemical Plants

  • Facilitates process optimization and emissions monitoring by providing accurate sulfur readings.

• Utility and Power Generation Facilities

  • Helps in regulatory reporting and process efficiency by monitoring sulfur content in fuel supplies.

These applications leverage the real-time and accurate results provided by ASTM D7166-compliant analyzer systems to ensure safe, efficient, and environmentally responsible operations.

Related Standards

ASTM D7166-23 references and aligns with several other key ASTM and ISO standards, including:

• ASTM D1070 - Relative Density of Gaseous Fuels
• ASTM D1072 - Total Sulfur in Fuel Gases by Combustion and Barium Chloride Titration
• ASTM D3246 - Sulfur in Petroleum Gas by Oxidative Microcoulometry
• ASTM D3764 - Validation of the Performance of Process Stream Analyzer Systems
• ASTM D4150 - Terminology Relating to Gaseous Fuels
• ASTM D5453, D5504, D6667 - Various methods for sulfur determination in fuels
• ASTM D5287 - Automatic Sampling of Gaseous Fuels
• ISO 7504 - Gas Analysis Vocabulary

These related standards provide additional guidance on sampling practices, analytical method validation, calibration, terminology, and performance evaluation, supporting comprehensive quality assurance and regulatory compliance for sulfur content analysis in gaseous fuels.

Keywords: total sulfur analyzer, on-line monitor, at-line monitor, gaseous fuels, sulfur content, ASTM D7166-23, natural gas analysis, continuous fuel monitoring, sulfur analysis standard, gas industry standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7166 − 23
Standard Practice for
Total Sulfur Analyzer Based On-line/At-line for Sulfur
Content of Gaseous Fuels
This standard is issued under the fixed designation D7166; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D4298 Guide for Intercomparing Permeation Tubes to Es-
tablish Traceability
1.1 This practice is for the determination of total sulfur from
D4468 Test Method for Total Sulfur in Gaseous Fuels by
gas phase sulfur-containing compounds in high methane or
Hydrogenolysis and Rateometric Colorimetry
hydrogen content gaseous fuels using on-line/at-line instru-
D5287 Practice for Automatic Sampling of Gaseous Fuels
mentation.
D5453 Test Method for Determination of Total Sulfur in
1.2 The values stated in SI units are to be regarded as
Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel
standard. No other units of measurement are included in this
Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
standard.
D5503 Practice for Natural Gas Sample-Handling and Con-
1.3 This standard does not purport to address all of the ditioning Systems for Pipeline Instrumentation (With-
safety concerns, if any, associated with its use. It is the
drawn 2017)
responsibility of the user of this standard to establish appro- D5504 Test Method for Determination of Sulfur Compounds
priate safety, health, and environmental practices and deter-
in Natural Gas and Gaseous Fuels by Gas Chromatogra-
mine the applicability of regulatory limitations prior to use. phy and Chemiluminescence
1.4 This international standard was developed in accor-
D6122 Practice for Validation of the Performance of Multi-
dance with internationally recognized principles on standard- variate Online, At-Line, Field and Laboratory Infrared
ization established in the Decision on Principles for the
Spectrophotometer, and Raman Spectrometer Based Ana-
Development of International Standards, Guides and Recom- lyzer Systems
mendations issued by the World Trade Organization Technical
D6299 Practice for Applying Statistical Quality Assurance
Barriers to Trade (TBT) Committee.
and Control Charting Techniques to Evaluate Analytical
Measurement System Performance
2. Referenced Documents
D6621 Practice for Performance Testing of Process Analyz-
2.1 ASTM Standards: ers for Aromatic Hydrocarbon Materials
D1070 Test Methods for Relative Density of Gaseous Fuels D6667 Test Method for Determination of Total Volatile
D1072 Test Method for Total Sulfur in Fuel Gases by Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum
Combustion and Barium Chloride Titration Gases by Ultraviolet Fluorescence
D3246 Test Method for Sulfur in Petroleum Gas by Oxida-
2.2 ISO Standards
tive Microcoulometry
ISO 7504 Gas Analysis-Vocabulary
D3609 Practice for Calibration Techniques Using Perme-
ation Tubes 3. Terminology
D3764 Practice for Validation of the Performance of Process
3.1 Definitions:
Stream Analyzer Systems
3.1.1 For definitions of general terms used in D03 Gaseous
D4150 Terminology Relating to Gaseous Fuels
Fuels standards, refer to Terminology D4150.
3.2 Definitions of Terms Specific to This Standard:
This practice is under the jurisdiction of ASTM Committee D03 on Gaseous
3.2.1 total sulfur, n—summation of all gas phase sulfur
Fuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-Line
species present in a sample.
Analysis of Gaseous Fuels.
Current edition approved May 1, 2023. Published May 2023. Originally
approved in 2005. Last previous edition approved in 2015 as D7166 – 10 (2015).
DOI: 10.1520/D7166-23. The last approved version of this historical standard is referenced on
For referenced ASTM standards, visit the ASTM website, www.astm.org, or www.astm.org.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from International Organization for Standardization (ISO), 1, ch. de
Standards volume information, refer to the standard’s Document Summary page on la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
the ASTM website. www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7166 − 23
3.3 Abbreviations: streams such as tubing and valving must be constructed of
3.3.1 DCS—distributed control system suitable inert, or passivated, materials to ensure constituents in
the fuel stream do not degrade these components or alter the
3.3.2 SOP—standard operating procedure
composition of the sampled gas.
4. Summary of Practice
6.2 Sample Probes/Sample Extraction—The location and
orientation of sampling components are critical for ensuring
4.1 A representative sample of the gaseous fuel is extracted
from a process pipe or pipeline and is transferred in a timely that a representative sample is analyzed. The locations and
orientation of sampling components should be selected based
manner through an appropriately designed sampling system to
the inlet of a total sulfur analyzer. The sample is conditioned upon sound analytic and engineering considerations. Sampling
practices for gaseous fuels can be found in Practice D5287.
with a minimum, preferably negligible, impact on the sulfur
content. A precisely measured volume of sample is either
6.3 Sample Inlet System—The siting and installation of an
injected, or allowed to flow continuously, either directly into
at-line or on-line monitor is critical for collecting representa-
the analyzer or into a carrier gas, as required by the analyzer.
tive information on sulfur content. Factors that should be
Some total sulfur analyzer systems are configured such that
considered in siting an instrument include ease of calibration,
sample gas flows directly into the analyzer detection system.
ease of access for repair or maintenance, sample uniformity at
Excess process or pipeline sample is vented to atmosphere, to
the sampling point, appropriateness of samples from a sam-
flare or to the process stream dependant upon application and
pling location, ambient conditions, and of course safety issues.
regulatory requirements.
An automated gas sampling valve is required in many appli-
4.2 Sample containing carrier gas is fed to a furnace cations. All sampling system components in contact with the
operating at an elevated temperature where sulfur compounds fuel stream must be constructed of inert or passivated materi-
are converted into detectable species. The conversion reaction als. Care should be taken to ensure that the extracted sample is
may be oxidative or reductive and may require the introduction maintained as a particulate and condensate free gas. Heating at
of additional carrier or other supply gases. the point of pressure reduction or along the sample line to the
analyzer and the use of a filter may be required to ensure that
4.3 Furnace exit gasses are conditioned as required with
the sample is maintained in the gas phase. The need for heat
respect to temperature and water content and are introduced
tracing and the extent to which it is required will be site and
into the detector where quantification of the total sulfur content
application specific. In general, considerations impacting heat
occurs.
tracing decisions include sample compositions and the ex-
4.4 Calibration, maintenance, quality assurance and perfor-
pected variations, ambient temperature fluctuations, operating
mance protocols provide a means to validate the analyzer
pressures, anticipated pressure differentials in sample system
operation and the generated results.
components, and safety considerations. Sample filtration
should be utilized as required to remove particulate matter
5. Significance and Use
from the extracted sample. The sampling frequency relative to
5.1 On-line, at-line, in-line and other near-real time moni-
the process bandwidth is critical to ensuring that the reported
toring systems that measure fuel gas characteristics such as the
analytical results adequately represent the process being moni-
total sulfur content are prevalent in the natural gas and fuel gas
tored. The Nyquist-Shannon sampling criterion of a sampling
industries. The installation and operation of particular systems
frequency that exceeds twice the process bandwidth can be
vary on the specific objectives, contractual obligations, process
used to establish a minimum analytical cycle time. Sample
type, regulatory requirements, and internal performance re-
handling and conditioning system practices can be found in
quirements needed by the user. This protocol is intended to
Practice D5503.
provide guidelines for standardized start-up procedures, oper-
6.3.1 Carrier and Detector Gas Control—Constant flow
ating procedures, and quality assurance practices for on-line,
control of carrier and detector gases is critical for optimum and
at-line, in-line and other near-real time total sulfur monitoring
consistent analytical performance. Control is achieved by use
systems.
of pressure regulators and fixed flow restrictors as well as
rotameters. Temperature control is generally vital for ensuring
6. Apparatus
consistent operation of these devices. The gas flow is measured
by appropriate means and adjusted as necessary. Mass flow
6.1 Instrument—Any instrument of standard manufacture,
with hardware necessary for interfacing to a natural gas, controllers, capable of maintaining a gas flow constant to
within 61 % at the flow rates necessary for optimal instrument
hydrogen or other fuel gas pipeline and containing all the
features necessary for the intended application(s) can be used. performance are typically used.
6.1.1 Specific Sulfur Specie Detection Systems—The oper- 6.3.2 Detectors—Common detectors used for total sulfur
ating parameters employed generally must be capable of determinations include chemiluminescence (Test Method
converting all of the gas phase sulfur species in the sample into D5504), microcoulometry (Test Method D3246), lead acetate
a single detectable species such as sulfur dioxide or hydrogen (Test Method D4468), titration, such as barium chloride (Test
sulfide. Instrumentation must satisfy or exceed other analytic Method D1072), ultra-violet fluorescence (Test Methods
performance characteristics for accuracy and precision for the D5453 and D6667), both continuous and pulsed. Other detec-
intended application without encountering unacceptable inter- tors can be used provided they have appropriate linearity,
ference or bias. In addition, components in contact with sample sensitivity, and selectivity for the selected application. In
D7166 − 23
selecting a detector, the user should consider the linearity, when the permeation device temperature is changed to ensure
sensitivity, and selectivity of particular detection systems prior the reestablishment of a constant permeation rate. Calibration
to installation. The user should also consider interference from devices using permeation tubes contain a temperature con-
substances in the gas stream that could result in inaccurate trolled oven and employ flow control to maintain a constant
sulfur gas measurement due to effects such as quenching. diluent flow rate. Practice D3609 and Guide D4298 contain
additional information on permeation tubes.
6.4 Data Acquisition—Data acquisition and storage can be
accomplished using a number of devices and media. Following
8. Equipment Siting and Installation
are some examples.
8.1 A sample inlet system capable of operating continuously
6.4.1 Recorder—A 0 to 1 mV range recording potentiometer
and delivering a gas phase sample to the analyzer is necessary.
or equivalent can be used.
The location of the sample inlet to the analyzer relative to the
6.4.2 Communications—Efficient communications between
sample extraction point is critical to obtaining timely analytical
the analyzer and the host depend on resolving any and all
results. Ideally, the analyzer is close coupled to the sample
interface issues. Signals to and from the host are typically
extraction point and there is an insignificant sampling lag time.
optically isolated from each other.
Normally, the analyzer is mounted at some distance away from
7. Reagents and Materials
the sample extraction point. This increased distance represents
increased lag time between when a sample is extracted from a
7.1 Warning—Compressed gas standards should only be
process and when an analytical result is reported. The maxi-
handled in well ventilated locations away from sparks and
mum allowable lag time depends on the specifics of the
flames. Improper handling of compressed gas cylinders con-
sampling location relative to the process being sampled. A fast
taining calibration standards, air, nitrogen, hydrogen, argon or
loop sweep can be used to minimize the lag time by creating a
helium can result in explosion. Rapid release of nitrogen or
bypass loop that flows sample from the process to the analyzer
helium can result in asphyxiation. Compressed air supports
and is then returned to the process or is vented.
combustion. Sulfur species and radiation source
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7166 − 10 (Reapproved 2015) D7166 − 23
Standard Practice for
Total Sulfur Analyzer Based On-line/At-line for Sulfur
Content of Gaseous Fuels
This standard is issued under the fixed designation D7166; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice is for the determination of total sulfur from volatile gas phase sulfur-containing compounds in high methane or
hydrogen content gaseous fuels using on-line/at-line instrumentation.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1070 Test Methods for Relative Density of Gaseous Fuels
D1072 Test Method for Total Sulfur in Fuel Gases by Combustion and Barium Chloride Titration
D3246 Test Method for Sulfur in Petroleum Gas by Oxidative Microcoulometry
D3609 Practice for Calibration Techniques Using Permeation Tubes
D3764 Practice for Validation of the Performance of Process Stream Analyzer Systems
D4150 Terminology Relating to Gaseous Fuels
D4298 Guide for Intercomparing Permeation Tubes to Establish Traceability
D4468 Test Method for Total Sulfur in Gaseous Fuels by Hydrogenolysis and Rateometric Colorimetry
D5287 Practice for Automatic Sampling of Gaseous Fuels
D5453 Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel,
and Engine Oil by Ultraviolet Fluorescence
D5503 Practice for Natural Gas Sample-Handling and Conditioning Systems for Pipeline Instrumentation (Withdrawn 2017)
D5504 Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and
Chemiluminescence
This practice is under the jurisdiction of ASTM Committee D03 on Gaseous Fuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-Line Analysis
of Gaseous Fuels.
Current edition approved June 1, 2015May 1, 2023. Published July 2015May 2023. Originally approved in 2005. Last previous edition approved in 20102015 as
D7166D7166 – 10 (2015).–10. DOI: 10.1520/D7166-10R15.10.1520/D7166-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7166 − 23
D6122 Practice for Validation of the Performance of Multivariate Online, At-Line, Field and Laboratory Infrared
Spectrophotometer, and Raman Spectrometer Based Analyzer Systems
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6621 Practice for Performance Testing of Process Analyzers for Aromatic Hydrocarbon Materials
D6667 Test Method for Determination of Total Volatile Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum Gases by
Ultraviolet Fluorescence
D6920 Test Method for Total Sulfur in Naphthas, Distillates, Reformulated Gasolines, Diesels, Biodiesels, and Motor Fuels by
Oxidative Combustion and Electrochemical Detection (Withdrawn 2018)
2.2 ISO Standards
ISO 7504 Gas Analysis-Vocabulary
3. Terminology
3.1 Definitions:
3.1.1 For definitions of general terms used in D03 Gaseous Fuels standards, refer to Terminology D4150.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.1.1 at-line instrument—instrumentation requiring operator interaction that samples gas directly from the pipeline.
3.1.2 calibration gas mixture, n—a certified gas mixture with known composition used for the calibration of a measuring
instrument or for the validation of a measurement or gas analytical method.
3.1.2.1 Discussion—
Calibration Gas Mixtures are the analogues of measurement standards in physical metrology (reference ISO 7504 paragraph 4.1).
3.1.3 continuous fuel monitor—instrument that samples gas directly from the pipeline on a continuous or semi-continuous basis.
3.1.4 direct sampling—sampling where there is no direct connection between the medium to be sampled and the analytical unit.
3.1.5 in-line instrument—instrument with an active element installed in a pipeline, which is used to measure pipeline contents or
conditions.
3.1.6 on-line instrument—instrument that samples gas directly from a pipeline, but is installed externally.
3.1.7 reference gas mixture, n—a certified gas mixture with known composition used as a reference standard from which other
compositional data are derived.
3.1.7.1 Discussion—
Reference Gas Mixtures are the analogues of measurement standards of reference standards (reference ISO 7504 paragraph 4.1.1).
3.2.1 total reducedsulfur, sulfur n—(TRS)—concentration summation of all volatile gas phase sulfur species with a −2 sulfur
oxidation number, excluding sulfur dioxide, sulfones and other inorganic sulfur compounds.present in a sample.
3.1.9 total sulfur—concentration summation of all volatile sulfur species in a sample.
3.1.10 volatile—molecular characteristic wherein the sulfur specie exists in the gas phase at the operating conditions of the process
or pipeline.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
D7166 − 23
3.3 Abbreviations:
3.3.1 DCS—distributed control system
3.3.2 SOP—standard operating procedure
4. Summary of Practice
4.1 A representative sample of the gaseous fuel is extracted from a process pipe or pipeline and is transferred in a timely manner
through an appropriately designed sampling system to the inlet of a total sulfur analyzer. The sample is conditioned with a
minimum, preferably negligible, impact on the sulfur content. A precisely measured volume of sample is either injected, or allowed
to flow continuously, either directly into the analyzer or into a carrier gas, as required by the analyzer. Some total sulfur analyzer
systems are configured such that sample gas flows directly into the analyzer detection system. Excess process or pipeline sample
is vented to atmosphere, to flare or to the process stream dependant upon application and regulatory requirements.
4.2 Sample containing carrier gas is fed to a furnace operating at an elevated temperature where sulfur compounds are converted
into detectable species. The conversion reaction may be oxidative or reductive and may require the introduction of additional
carrier or other supply gases.
4.3 Furnace exit gasses are conditioned as required with respect to temperature and water content and are introduced into the
detector where quantification of the total sulfur content occurs.
4.4 Calibration, maintenance, quality assurance and performance protocols provide a means to validate the analyzer operation and
the generated results.
5. Significance and Use
5.1 On-line, at-line, in-line and other near-real time monitoring systems that measure fuel gas characteristics such as the total
sulfur content are prevalent in the natural gas and fuel gas industries. The installation and operation of particular systems vary on
the specific objectives, contractual obligations, process type, regulatory requirements, and internal performance requirements
needed by the user. This protocol is intended to provide guidelines for standardized start-up procedures, operating procedures, and
quality assurance practices for on-line, at-line, in-line and other near-real time total sulfur monitoring systems.
6. Apparatus
6.1 Instrument—Any instrument of standard manufacture, with hardware necessary for interfacing to a natural gas, hydrogen or
other fuel gas pipeline and containing all the features necessary for the intended application(s) can be used.
6.1.1 Specific Sulfur Specie Detection Systems—The operating parameters employed generally must be capable of converting all
of the volatile gas phase sulfur species in the sample into a single detectable species such as sulfur dioxide or hydrogen sulfide.
Instrumentation must satisfy or exceed other analytic performance characteristics for accuracy and precision for the intended
application without encountering unacceptable interference or bias. In addition, components in contact with sample streams such
as tubing and valving must be constructed of suitable inert, or passivated, materials to ensure constituents in the fuel stream do
not degrade these components or alter the composition of the sampled gas.
6.2 Sample Probes/Sample Extraction—The location and orientation of sampling components are critical for ensuring that a
representative sample is analyzed. The locations and orientation of sampling components should be selected based upon sound
analytic and engineering considerations. Sampling practices for gaseous fuels can be found in Practice D5287.
6.3 Sample Inlet System—The siting and installation of an at-line or on-line monitor is critical for collecting representative
information on sulfur content. Factors that should be considered in siting an instrument include ease of calibration, ease of access
for repair or maintenance, sample uniformity at the sampling point, appropriateness of samples from a sampling location, ambient
conditions, and of course safety issues. An automated gas sampling valve is required in many applications. All sampling system
components in contact with the fuel stream must be constructed of inert or passivated materials. Care should be taken to ensure
that the extracted sample is maintained as a particulate and condensate free gas. Heating at the point of pressure reduction or along
the sample line to the analyzer and the use of a filter may be required to ensure that the sample is maintained in the gas phase.
D7166 − 23
The need for heat tracing and the extent to which it is required will be site and application specific. In general, considerations
impacting heat tracing decisions include sample compositions and the expected variations, ambient temperature fluctuations,
operating pressures, anticipated pressure differentials in sample system components, and safety considerations. Sample filtration
should be utilized as required to remove particulate matter from the extracted sample. The sampling frequency relative to the
process bandwidth is critical to ensuring that the reported analytical results adequately represent the process being monitored. The
Nyquist-Shannon sampling criterion of a sampling frequency that exceeds twice the process bandwidth can be used to establish
a minimum analytical cycle time. Sample handling and conditioning system practices can be found in Practice D5503.
6.3.1 Carrier and Detector Gas Control—Constant flow control of carrier and detector gases is critical for optimum and consistent
analytical performance. Control is achieved by use of pressure regulators and fixed flow restrictors as well as rotameters.
Temperature control is generally vital for ensuring consistent operation of these devices. The gas flow is measured by appropriate
means and adjusted as necessary. Mass flow controllers, capable of maintaining a gas flow constant to within 61 % at the flow
rates necessary for optimal instrument performance are typically used.
6.3.2 Detectors—Common detectors used for total sulfur determinations include chemiluminescence (Test Method D5504),
microcoulometry (Test Method D3246), electrochemical (Test Method D6920), lead acetate (Test Method D4468), titration, such
as barium chloride (Test Method D1072), ultra-violet fluorescence (Test Methods D5453 and D6667), both continuous and pulsed.
Other detectors can be used provided they have appropriate linearity, sensitivity, and selectivity for the selected application. In
selecting a detector, the user should consider the linearity, sensitivity, and selectivity of particular detection systems prior to
installation. The user should also consider interference from substances in the gas stream that could result in inaccurate sulfur gas
measurement due to effects such as quenching.
6.4 Data Acquisition—Data acquisition and storage can be accomplished using a number of devices and media. Following are
some examples.
6.4.1 Recorder—A 0 to 1 mV range recording potentiometer or equivalent can be used.
6.4.2 Communications—Efficient communications between the analyzer and the host depend on resolving any and all interface
issues. Signals to and from the host are typically optically isolated from each other.
7. Reagents and Materials
NOTE 1—Warning: Compressed gas standards should only be handled in well ventilated locations away from sparks and flames. Improper handling of
compressed gas cylinders containing calibration standards, air, nitrogen, hydrogen, argon or helium can result in explosion. Rapid release of nitrogen or
helium can result in asphyxiation. Compressed air supports combustion. Sulfur species and radiation sources can be toxic.
7.1 Warning—Compressed gas standards should only be handled in well ventilated locations away from sparks and flames.
Improper handling of compressed gas cylinders containing calibration standards, air, nitrogen, hydrogen, argon or helium can result
in explosion. Rapid release of nitrogen or helium can result in asphyxiation. Compressed air supports combustion. Sulfur species
and radiation sources can be toxic.
7.2 Carrier Gas and Other Supply Gases—Helium or nitrogen with
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