This report is the property of AGA and is part of its process for developing new
documents. This report or any of its part shall not be copied, disseminated, cited
in literature, presentations or discussions without prior approval from AGA.
AGA Report No. 10, Speed of Sound in Natural Gas
1
AGA Report No. 10
Speed of Sound in Natural Gas and
Other Related Hydrocarbon Gases
November 15, 2002 Post-Ballot Draft
Prepared by
Transmission Measurement Committee
This report is the property of AGA and is part of its process for developing new
documents. This report or any of its part shall not be copied, disseminated, cited
in literature, presentations or discussions without prior approval from AGA.
AGA Report No. 10, Speed of Sound in Natural Gas
2
Table Of Contents
Forward
1 Introduction
1.1 Scope
1.2 Background
1.3 Field of Application
1.4 Types of Properties
1.5 Types of Gases
1.6 Types of Conditions
2 Uncertainty
3 Calculations
3.1 Symbols
3.2 Overview of Calculation Method and Sequence
3.3 Compliance
3.4 Equations for Speed of Sound
3.5 Critical Flow Factor Determination
4 Characteristics of Typical Gases
5 References
6 Computation Flow Charts
7 Calculation Output for Program Verification
7.1 Detailed Output Results for Program Development
7.1.1 Detailed Output Result #1
7.1.2 Detailed Output Result #2
7.1.3 Detailed Output Result #3
7.2 Tabled Results for Compliance Checking and Program Development
APPENDIX A C++ Language Example Implementation
1.0 Overview of Computer Code
1.1 File Group 1 Calculation Library
1.2 File Group 2 Example Windows Application
This report is the property of AGA and is part of its process for developing new
documents. This report or any of its part shall not be copied, disseminated, cited
in literature, presentations or discussions without prior approval from AGA.
AGA Report No. 10, Speed of Sound in Natural Gas
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1. Introduction
1.1 Scope
This document contains information for precise computation of sound speed in
natural gas and other related hydrocarbon gases. Procedures are included for
computation of several related gas properties, including heat capacity, enthalpy,
entropy and the critical flow coefficient, C*.
The methods in this document are extensions to Compressibility Factors for
Natural Gas and Other Hydrocarbon Gases, AGA Transmission Measurement
Committee Report No. 8, 2
nd
Edition, 2
nd
Printing (1994). This document contains
excerpts from Report No. 8, but intentionally does not reproduce the full report.
Similarly, the methods for computing the critical flow coefficient, C*, are based on
the information in appendix E of ASME/ANSI MFC-7M-1987. Users are referred
to this source for background and pertinent references.
Procedures for computing other natural gas properties such as volumetric
heating value and relative density fall outside of the scope of this report and are
not included.
1.2 Background
This is the first AGA document on speed of sound. It is based on a large
database of high accuracy basic physical property research data obtained
through research sponsored by the Gas Research Institute in cooperation with
the American Gas Association, the American Petroleum Institute and Groupe
Europeen de Recherches Gazieres (GERG).
The methods presented in this AGA document utilize high accuracy calculation
procedures and related equations of state already implemented by AGA, API and
ISO.
For continuity and ease of application, the original AGA Report No. 8 solution
methods have been carried forward with little change. Computer code
development for Report No. 10 will be modest and incremental to most existing
AGA Report No. 8 implementations.
1.3 Field of Application
High accuracy sound speed information is needed in a variety of gas flow
measurement applications, such as ultrasonic meters and critical flow nozzles, as
well as analytical applications such as transducers and densitometers.
This report provides the information needed to compute the speed of sound in
natural gas and related hydrocarbon gases. The equations utilized are consistent
This report is the property of AGA and is part of its process for developing new
documents. This report or any of its part shall not be copied, disseminated, cited
in literature, presentations or discussions without prior approval from AGA.
AGA Report No. 10, Speed of Sound in Natural Gas
4
with AGA Report No. 8, API MPMS Chapter 14.2 and ISO Standard 12213 Part
2.
1.4 Types of Properties
The methods in this document may be used to compute a number of gas
properties including speed of sound, enthalpy, entropy, heat capacity and critical
flow coefficient.
In conjunction with the methods in AGA Report No. 8, procedures can be
developed to support a variety of applications including sonic nozzles,
compressor efficiency, and heat exchanger calculations.
1.5 Types of Gases
This report is intended for natural gases and other related hydrocarbon gases.
Table 1 identifies the ranges of gas characteristics for which this report can be
used. The normal range column gives the range of gas characteristics for which
the average expected uncertainty corresponds to the uncertainties identified in
Figure 1. The expanded range of gas characteristics has an uncertainty, which is
expected to be higher, especially outside of region 1 of Figure 1. The use of this
report for computations of the physical properties of gases with component mole
percentages outside the ranges given in Table 1 is not recommended.
An accepted database for water, heavy hydrocarbons and hydrogen sulfide in
natural gases is not presently available for determinations of uncertainties of
calculated gas properties. Therefore, as a practical matter, the only limitation is
that the calculation is for the gas phase. Thus, the limits are the water dew point
for mole percent water, the hydrocarbon dew point for mole percent heavy
hydrocarbons, and pure hydrogen sulfide. The presentation of methods for
calculations using the various heavy hydrocarbon fraction characterization
methods used in the hydrocarbon industry is beyond the scope of this report.
This report is the property of AGA and is part of its process for developing new
documents. This report or any of its part shall not be copied, disseminated, cited
in literature, presentations or discussions without prior approval from AGA.
AGA Report No. 10, Speed of Sound in Natural Gas
5
Table 1 Range of Gas Mixture Characteristics Consistent with this Report
Quantity Normal Range Expanded Range
Relative Density * 0.554 to 0.87 0.07 to 1.52
Gross Heating Value ** 477 to 1150 Btu/scf 0 to 1800 Btu/scf
Gross Heating Value *** 18.7 to 45.1 MJ/m
3
0 to 66 MJ/m
3
Mole Percent Methane 45.0 to 100.0 0 to 100.0
Mole Percent Nitrogen 0 to 50.0 0 to 100.0
Mole Percent Carbon Dioxide 0 to 30.0 0 to 100.0
Mole Percent Ethane 0 to 10.0 0 to 100.0
Mole Percent Propane 0 to 4.0 0 to 12.0
Mole Percent Total Butanes 0 to 1.0 0 to 6.0
Mole Percent Total Pentanes 0 to 0.3 0 to 4.0
Mole Percent Hexanes Plus 0 to 0.2 0 to Dew Point
Mole Percent Helium 0 to 0.2 0 to 3.0
Mole Percent Hydrogen 0 to 10.0 0 to 100.0
Mole Percent Carbon Monoxide 0 to 3.0 0 to 3.0
Mole Percent Argon # 0 to 1.0
Mole Percent Oxygen # 0 to 21.0
Mole Percent Water 0 to 0.05 0 to Dew Point
Mole Percent Hydrogen Sulfide 0 to 0.02 0 to 100.0
* Reference Conditions: Relative Density at 60° F, 14.73 psia.
** Reference Conditions: Combustion at 60° F, 14.73 psia; density at 60° F, 14.73 psia.
*** Reference Conditions: Combustion at 25° C, 0.101325 MPa; density at 0° C, 0.101325 MPa.
# The normal range is considered to be zero for these compounds.
1.6 Types of Conditions
This report is only valid for the gas phase. The methods can be applied for
temperatures from -130° C to 200° C (-200° F to 400° F) at pressures up to 138
MPa (20,000 psia). Application at extreme conditions should be verified by other
means (e.g., experimental verification). Use of the calculation method is not
recommended within the vicinity of the critical point. For pipeline quality gas, this
is usually not a constraint because operating conditions near the critical point
generally are not encountered.
