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Title: Uncertainty Estimates For The Gravimetric Primary Flow Standards Of The Mrf
Author: Joel T. Park, Kendricks A. Behring II, Terrence A. Grimley
Source: 1995 International Symposium on Fluid Flow Measurement
Year Published: 1995
Abstract: Two gravimetric flow standards for mass flowrate are in operation for the calibration of high capacity flowmeters with natural gas. Both systems measure mass electronically from scales which operate on a gyroscopic principle. The gravimetric provers are an integral part of the Gas Research Institute (GRI) Metering Research Facility (MRF) and can provide a direct primary calibration for any conventional gas flowmeter. The smaller system is attached to the Low Pressure Loop (LPL) with an operating pressure of 0.14 to 1.4 MPa (20 to 200 psia) and a flowrate up to 4.6 kg/s (10 lbm/s). The larger system is connected to the High Pressure Loop (HPL) with pressures of 1.4 to 10 MPa (200 to 1,455 psia) and flows to 43 kg/s (95 lbm/s). The performance of these two standards and their estimated uncertainties are described. The optimal total uncertainty in mass flowrate is 0.01 % and 0.02 %, respectively, for die LPL and HPL. The actual uncertainty is dependent on the operating conditions and is primarily a function of the operating pressure and flowrate. Uncertainty estimates are provided on the calibration of turbine meters and sonic nozzles. The largest uncertainty in the calibration of flowmeters is the uncertainty in theoretical models for density and the measurement of natural gas composition.