Traceability Chain and Uncertainty of the U.S. National Flow Standard for High Pressure Natural Gas

Published

May 20, 2026

Author(s)

Aaron Johnson, Brad Sims, Jason Johansen, Joel Clancy

Abstract

In 2009 NIST and CEESI Iowa established an internationally recognized flow standard to calibrate flow meters used for custody transfer of high-pressure natural gas. Initially, the flow capacity of the facility ranged from 0.25 m3/s (18 kg/s) to 10.7 m3/s (780 kg/s) with expanded uncertainties from 0.23% to 0.4% depending on flow. In 2019 a joint project to update the traceability chain and reduce the expanded uncertainty was launched. An 8-stage bootstrap process was implemented that used critical flow venturis (CFVs) and turbine meter working standards to scale-up low pressure air flow measurements made by NIST's 677 L pressure-volume temperature-time (PVTt) primary standard to high pressure natural gas flows. Stage 1 of the bootstrapping process began by individually calibrating 21 CFVs in air against the PVTt standard. Stages 2 and 3 used these CFVs to calibrate additional CFVs in air at higher pressures and flows. In stage 4, an array of these high pressure CFVs was used to calibrate a turbine meter in dry air. This turbine meter was then used in stage 5 to calibrate 3 additional turbine meters in high pressure natural gas at matched Reynolds numbers. In stage 6 a parallel array of these four meters calibrated two larger turbine meters. These two turbine meters calibrated each of the 9 turbine meter working standards that are used for customer calibrations at the CEESI Iowa flow laboratory. This resulted in uncertainties from 0.16% to 0.21% for volumetric flow rate at a customer meter. This 8-stage process is now being repeated to validate the stability of the flow standards and to further reduce the uncertainty. This manuscript documents the 8-stage calibration process performed in 2019, the lessons learned during that process, and the planned changes in the process during the current iteration.

Proceedings Title

The 20th International Flow Measurement Conference FLOMEKO 2026

Conference Dates

May 17-20, 2026

Conference Location

Nara, JP

Conference Title

FLOMEKO26

Pub Type

Conferences

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Keywords

US national standard for custody transfer natural gas flow measurement, US reference standard system for custody transfer natural gas measurement in pipelines, critical flow venturis, turbine meter, Measurement uncertainty of the US national custody transfer natural gas flow standard

Citation

Johnson, A. , Sims, B. , Johansen, J. and Clancy, J. (2026), Traceability Chain and Uncertainty of the U.S. National Flow Standard for High Pressure Natural Gas, The 20th International Flow Measurement Conference FLOMEKO 2026, Nara, JP, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=961679 (Accessed June 13, 2026)

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