Natural gas. Measurement of properties. Volumetric properties: density, pressure, temperature and compression factor

The advantages of ultrasonic flow meters are well know — no line obstructions, large turndown ratio, bi-directionality, high accuracy — and ultrasonic meters are now widely used within the gas industry in a wide variety of applications. Ultrasonic meters are available in several different configurations ranging from high accuracy multipath spoolpiece meters to single path hot-tapped meters. While all of these meters operate on the same basic transit-time principle, there are significant differences in their operational aspects. This paper is intended to review the basic concepts of ultrasonic flow meters, to clarify the differences listed, and to explain how ultrasonic meters should be specified.

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Investigation of the causes for the measurement differences between the natural gas measurement systems of a gas distribution company and of a consumer

Journal of Physics Conference Series ◽

10.1088/1742-6596/648/1/012002 ◽

2015 ◽

Vol 648 ◽

pp. 012002

Author(s):

Kazuto Kawakita ◽

Rubens Silva Telles

Keyword(s):

Natural Gas ◽

Gas Distribution ◽

Measurement Systems ◽

Gas Measurement ◽

Distribution Company

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Applications of Accurate Isentropic Exponent Determination for Fuel Gas Measurement

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/95-gt-037 ◽

1995 ◽

Author(s):

David J. Pack ◽

Terry J. Edwards ◽

Derek Fawcett

Keyword(s):

Natural Gas ◽

Gas Flow ◽

Precise Measurement ◽

Gas Flows ◽

Fuel Gas ◽

Isentropic Exponent ◽

Natural Gas Transmission ◽

Gas Measurement ◽

Cost Penalty

This paper discusses the determination and application of the isentropic exponent to the various thermodynamic processes found in a high pressure natural gas transmission system. Increasing demands for more precise measurement of natural gas, coupled with the need for greater efficiency and accountability of transportation and processing operations had led to our research and development efforts into the more precise measurement of gas flow, and the determination of gas thermodynamic properties including isentropic exponent. The isentropic exponent has many applications, some of which include: • the determination of the expansion factor ϵ, for calcuation of flow using an orifice or venturi type meter; • the volumetric efficiency in a reciprocating compressor; • the determination of the compression head for a centrigual compressor; • the engine power required for the set given conditions for gas compressor; • the calculation of discharge temperatures for compressors; and • the direct measurement of gas density. As can be appreciated, the application of an incorrect value for the isentropic exponent represents an error in the parameter determined. For large volume gas flows, this can translate into a significant cost penalty.

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Uncertainty Evaluation of the Natural Gas Molar Mass and Its Flow Rate Impact

2008 7th International Pipeline Conference, Volume 1 ◽

10.1115/ipc2008-64386 ◽

2008 ◽

Author(s):

Elcio Cruz de Oliveira

Keyword(s):

Natural Gas ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Molar Mass ◽

Internal Diameter ◽

Gas Measurement ◽

Oil And Natural Gas ◽

Mass Uncertainty ◽

The Impact

In Brazil, the National Oil Agency — ANP and the National Metrology Institute elaborated Regulation No 1, on June 19th 2000. This government decree approves the Regulation of the Measurement Technique of Oil and Natural Gas, which establishes the minimum conditions and requirements for the oil and natural gas measurement systems, in order to guarantee accurate and complete results. The natural gas measurement fiscal systems must be projected, calibrated and operated so that the measurement uncertainty does not exceed 1.5%. Based on the norms AGA and ISO, the mathematical model for the calculation of the mass flow rate, depends on quantities that have well known uncertainty such as: orifice plate diameter, pipeline internal diameter, compressibility factor, discharge coefficient, differential pressure, static pressure and flow temperature. However, for the molar mass standard uncertainty fixed values are utilized in Brazil (mainly by IPT and PUC-RJ), around 0.30%, independent of the natural gas composition. The objective of this work is to develop a methodology to calculate the molar mass uncertainty of the natural gas derived from its chemical composition, analyzed by gaseous chromatography and to comparing it with the value currently practiced, evaluating the impact proceeding from this difference in the mass flow rate of the natural gas. Based on this methodology, the molar mass uncertainty is around 0.05% and the fiscal system uncertainty decreases in more than 10% when it is compared with the mass molar fixed value uncertainty.

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