ASTM D7314-08

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Designation:D7314–08
Standard Practice for
Determination of the Heating Value of Gaseous Fuels using
Calorimetry and On-line/At-line Sampling
This standard is issued under the fixed designation D7314; 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 D4150 Terminology Relating to Gaseous Fuels
D4891 Test Method for Heating Value of Gases in Natural
1.1 This practice is for the determination of the heating
Gas Range by Stoichiometric Combustion
value measurement of gaseous fuels using a calorimeter.
D5287 Practice for Automatic Sampling of Gaseous Fuels
Heatingvaluedeterminationofsamplegassescontainingwater
D5503 Practice for Natural Gas Sample-Handling and Con-
vapor will require vapor phase moisture measurements of the
ditioning Systems for Pipeline Instrumentation
pre-combustion sample gas as well as the non-condensed
D6122 Practice for Validation of the Performance of Mul-
gasses exiting the calorimeter. Instruments equipped with
tivariate Process Infrared Spectrophotometer Based Ana-
appropriate conditioners and algorithms may provide heating
lyzer Systems
value results on a net or gross and dry or wet basis.
D6299 Practice for Applying Statistical Quality Assurance
1.2 This practice is applicable to at-line and in-line instru-
and Control Charting Techniques to Evaluate Analytical
ments that are operated from time to time on a continuous
Measurement System Performance
basis.
D6621 Practice for PerformanceTesting of ProcessAnalyz-
1.3 The values stated in SI units are to be regarded as the
ers for Aromatic Hydrocarbon Materials
standard. The values given in parentheses are for information
D7164 Practice for On-line/At-line Heating Value Determi-
only.
nation of Gaseous Fuels by Gas Chromatography
1.4 This standard does not purport to address all of the
2.2 ISO Standards:
safety concerns, if any, associated with its use. It is the
ISO 14532 Natural gas – Vocabulary
responsibility of the user of this standard to establish appro-
ISO 7504 Gas analysis – Vocabulary
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3. Terminology
2. Referenced Documents 3.1 Definitions:
3.1.1 at-line instrument, n—See Terminology D4150, Sec-
2.1 ASTM Standards:
tion 3.
D1070 Test Methods for Relative Density of Gaseous Fuels
3.1.2 auto-verification, n—anautomatedmeansofintroduc-
D1826 Test Method for Calorific (Heating) Value of Gases
ing Calibration Gas Mixtures or Reference Gas Mixtures into
in Natural Gas Range by Continuous Recording Calorim-
an analyzer for the purposes of verifying the analyzer response
eter
without making any adjustments to the calibration parameters
D3588 PracticeforCalculatingHeatValue,Compressibility
of the analyzer.
Factor, and Relative Density of Gaseous Fuels
3.1.3 bypass line, n—Line ultimately vented to the atmo-
D3764 Practice for Validation of the Performance of Pro-
spherethatisusedwhereitisimpracticaltoprovideasufficient
cess Stream Analyzer Systems
pressure differential.
3.1.3.1 Discussion—The flowrate and pressure loss in the
This practice is under the jurisdiction of ASTM Committee D03 on Gaseous
open-ended line needs to be controlled so as to ensure that the
Fuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-Line
sample accuracy is not affected from any cooling and conden-
Analysis of Gaseous Fuels.
sation or both (reference ISO 14532 paragraph 2.3.2.9).
Current edition approved May 1, 2008. Published June 2008. DOI: 10.1520/
D7314-08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from International Organization for Standardization (ISO), 1, ch. de
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D7314–08
3.1.4 calibration gas mixture, n—a certified gas mixture 4.3 Calibration (7.1), maintenance (Section 10), and perfor-
with known composition used for the calibration of a measur- mance (Section 9) protocols provide a means to validate and
ing instrument or for the validation of a measurement or gas assess operation of the analyzer.
analytical method.
5. Significance and Use
3.1.4.1 Discussion—Calibration Gas Mixtures are the ana-
5.1 On-line, at-line, in-line and other near-real time moni-
logues of measurement standards in physical metrology (ref-
toring systems that measure fuel gas characteristics such as
erence ISO 7504 paragraph 4.1)
heating value are prevalent in various gaseous fuel industries
3.1.5 calorimeter, n—See Terminology D4150, Section 3.
and in industries either producing or using gaseous fuel in their
3.1.6 continuous fuel monitor, n—an instrument that
industrial processes. The installation and operation of particu-
samples gas directly from a source continuously and provides
larsystemsvarydependingonprocesstype,regulatoryrequire-
an analytical result on a continuous or semi-continuous basis.
ments, and the user’s objectives and performance require-
3.1.7 direct sampling, adj—sampling where there is a direct
ments. This practice is intended to provide guidance for
connection between the sample source and the analytical unit,
standardized start-up procedures, operating procedures, and
that is, in-line or on-line instrument.
quality assurance practices for calorimeter based on-line,
3.1.8 dry gas, n—See Terminology D4150, Section 3.
at-line, in-line and other near-real time heating value monitor-
3.1.9 fast loop/hot loop, n—Bypass loop that returns
ing systems. Users employing gas chromatographic based
sampled gas to the process line in a closed configuration and
instrumentation for measurement of gaseous fuel heating value
used for environmental and safety considerations.
are referred to Practice D7164.
3.1.9.1 Discussion—The loop requires a pressure differen-
tial from the collection point to the discharge point so as to
6. Apparatus
ensure a constant and steady flowrate through the sampling
6.1 Instrument—Any instrument of standard manufacture,
equipment located in the loop (reference ISO 14532 paragraph
with hardware necessary for interfacing to a fuel gas pipeline
2.3.2.8)
and containing all the features necessary for the intended
3.1.10 gross heating value (also called higher heating
application(s) can be used.
value), n—See Terminology D4150, Section 3.
6.1.1 Combustion System—Operating parameters employed
3.1.11 heating value, n—the amount of energy per volume
must be capable of converting all of the volatile combustible
transferred as heat from the complete, ideal combustion of the
chemical species in the sample into carbon dioxide, water,
gas at standard temperature.
nitrogen, nitrogen dioxide, and/or sulfur dioxide, using a dry,
3.1.12 in-line instrument, n—SeeTerminology D4150, Sec-
hydrocarbon-free oxidant which is typically air. A change of
tion 3.
less than or equal to 1,000 ppm/wt in the moisture content of
3.1.13 net heating value (also called lower heating value),
instrumentairbetweencalorimetercalibrationsisacceptableto
n—See Section 3 entitled Terminology, of D4150.
maintain a statistically insignificant 6 0.1% heating value
3.1.14 on-line instrument, n—See Terminology D4150,
accuracy as denoted in Practice D4891. The less than 1,000
Section 3.
ppm/wt moisture content control value is easily achieved using
3.1.15 reference gas mixture, n—a certified gas mixture
desiccant or refrigerant air dryers when the air dryers are
with known composition used as a reference standard from
maintained according to the manufacturer’s recommendations.
which other compositional data are derived.
Instrumentation must satisfy or exceed analytic performance
3.1.15.1 Discussion— Reference Gas Mixtures are the ana-
characteristics for accuracy and precision for the intended
logues of reference standards (ISO 7504 paragraph 4.1.1)
application without encountering unacceptable interference or
3.1.16 wet gas, n—See Terminology D4150, Section 3.
bias. In addition, components in contact with sample streams
3.2 Acronyms:
suchastubingandvalvingmustbeconstructedofsuitableinert
3.2.1 SOP, n—Standard Operating Procedure.
or passivated materials to ensure that the composition of the
3.2.2 QA, n—Quality Assurance.
sampled gas is not altered.
6.2 Sample Probes/Sample Extraction—The location and
4. Summary of Practice
orientation of sampling components are critical for ensuring
4.1 Arepresentative sample of the gaseous fuel is extracted that a representative sample is analyzed. The locations and
from a process pipe, a pipeline, or other gaseous fuel stream
orientation of sampling components should be selected based
and is transferred to an analyzer sampling system. After upon sound analytic and engineering considerations. Sampling
conditioning that maintains the sample integrity, the sample is
practices for gaseous fuels can be found in Practice D5287.
introduced into a calorimeter. Excess extracted process or 6.3 Sample Inlet System—Anautomatedgassamplingvalve
sample gas is vented to the atmosphere, a flare header, or is
is required in many applications. All sampling system compo-
returnedtotheprocessinaccordancewithapplicableeconomic nents in contact with the fuel stream must be constructed of
and environmental requirements and regulations. Post-
inert or passivated materials. Care should be taken to ensure
combustion gasses from the calorimeter are typically vented to that the extracted sample is maintained in a single clean
the atmosphere.
gaseous phase. The addition of heat at the point of pressure
4.2 The heating value is calculated based upon the instru- reduction or along the sample line to the analyzer may be
ment’s response to changes in the heating value of the sample required to ensure that the sample is maintained in the gas
gas using an algorithm. phase. The need for heat tracing and the extent to which it is
D7314–08
required will be site specific. In general, considerations im- used.The number of components used is frequently minimized
pactingheattracingdecisionsincludesamplecompositionsand for economical reasons and to reduce the probability of error
the expected variations, ambient temperature fluctuations, during the preparation of the Calibration Gas Mixture. In order
operating pressures, and anticipated pressure differentials in to ensure their accuracy and stability by preventing condensa-
sample system components. Sample filtration should be uti- tion and degradation, Calibration Gas Mixtures must be main-
lized as required to remove particulate matter from the ex- tained within the temperature range specified by the manufac-
tracted sample. turer. If there is any doubt concerning the validity of the
6.3.1 Combustion Air, Sample, and Carrier Gas Control— Calibration Gas Mixture, a Reference Gas Mixture should be
Constant flow control of combustion air, sample gas, and used to verify the validity of the Calibration Gas Mixture.
carrier gas, if required by the measurement application, is
necessary for optimum and consistent analytical performance.
8. Equipment Siting and Installation
Control is typically achieved by use of pressure regulators and
8.1 The siting and installation of an at-line or on-line
fixed flow restrictors. Ambient, combustion air, sample, and
monitor is critical for collecting representative information on
carrier gas temperature control is generally vital for ensuring
heating value content. Factors that should be considered in
consistent operation of flow control devices. The gas flow is
siting an instrument include hazardous area rating, ease of
measured and verified by appropriate means and adjusted as
calibration, ease of access for repair or maintenance, sample
necessary.
uniformity at the sampling point, appropriateness of samples
6.3.2 Detectors—Common calorimetry heating value detec-
from a sampling location, ambient conditions, and of course
tion systems include stoichiometric combustion (Test
safety issues. A sample inlet system capable of operating
Method 4891D4891), continuous recording calorimeters (Test
continuously at or above the maximum operating sample
Method D1826), non-stoichiometric combustion, and residual
temperatureisnecessary.Thelocationofthesampleinlettothe
oxygen detection calorimeters. Other detectors can be used
analyzer relative to the sample extraction point is critical to
provided they have appropriate linearity, accuracy, sensitivity
obtaining timely analytical results. Ideally, the analyzer is
and measurement range for the selected application. In select-
close-coupled to the sample extraction point and there is an
ing a detector, the user should consider the linearity and
insignificant sampling lag time. Normally, the analyzer is
sensitivity of a particular detection system prior to installation.
mounted at some distance away from the sample extraction
The user should also consider potential sample compositional
point. This increased distance will result in increased lag time
effects that may influence the reported heating value.
between when a sample is extracted from a process and when
6.4 Data Acquisition—Data acquisition and storage can be
an analytical result is reported. The maximum allowable lag
accomplished using a number of devices and media. Following
time depends on the specifics of the sampling location relative
are some examples:
totheprocessbeingsampled.Afastlooporby-passlinecanbe
6.4.1 Recorder—A0 to 1 millivolt or a 4-20 milliamp range
usedtominimizethelagtime.Thesamplingfrequencyrelative
recording potentiometer or equivalent, with a full-scale re-
totheprocessbandwidthiscriticaltoensuringthatthereported
sponse time of 2 s or less can be used mounted locally or
analytical results adequately represent the process being moni-
remotely.
tored. The Nyquist-Shannon sampling criterion of a sampling
6.4.2 Communications Systems—Efficient communications
frequency that exceeds twice the process bandwidth can be
between the analyzer and the host depend on resolving any and
used to establish a minimum analytical cycle time. Sample
all interface issues. Signals to and from the host are typically
handling and conditioning system practices can be found in
isolated from each other in an appropriate manner.
Practice D5503.
8.2 The sample should flow contin
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