Calculating The Speed Of Sound In Natural Gas — Aga Report No. 10 To Aga Report No. 8

Author: Jerry Paul Smith, Joel ClancyDownload File

The speed of sound in natural gas is the velocity a sound wave travels in the gas. There are a number of gas properties that affect the speed of sound and they include the composition of the gas, the pressure of the gas, and the temperature of the gas. The American Gas Association (AGA) Report No. 10, Speed of Sound in Natural Gas and Other Related Hydrocarbon Gases, first published in 2003 provided an accurate method for calculating the speed of sound in natural gas and other related hydrocarbon fluids.

Purpose of AGA Report No. 10

The development of ultrasonic flow meters prompted the development of AGA Report No. 10 (AGA 10). The ultrasonic meter determines the speed of sound in the gas as it calculates the flow of gas through the meter. In order for one to check the accuracy of the speed of sound measured by the ultrasonic meter, it was necessary to have an accurate method to calculate the speed of sound in natural gas. AGA 10 was developed to do just that. The speed of sound calculated by the method in AGA 10 compares very favorably to the speed of sound determined by the highly accurate research that was the basis for the report. The information in AGA 10 is not only useful for calculating the speed of sound in natural gas, but also, other thermodynamic properties of hydrocarbon fluids for other applications, such as the compression of natural gas and the critical flow coefficient represented by C*.

The audience for the revised AGA Report No. 8 is the same as it was for AGA 10 which includes measurement engineers involved with the operation and start-up of ultrasonic meters, sonic nozzles, and other meter types that are involved in applying the principles of natural gas thermodynamics to production, transmission, or distribution systems.

The methods for calculating the speed of sound in AGA 10 were an extension of the information contained in AGA Report No. 8 (AGA 8), Compressibility Factors of Natural Gas and Other Related Hydrocarbon Gases, and it does contain excerpts from AGA 8. This is especially true since the speed of sound is related to the compressibility of the gas.