Improvement and uncertainty evaluation of a static gravimetric facility for natural gas

Abstract

The mass & time facility was built up as a flow rate primary standard for natural gas operated from 3 bar to 60 bar in CVB in 2017. The calibration uncertainty for CFVs is from 0.12 % to 0.10 %(k = 2). To further reduced the calibration uncertainty, several methods were used including reducing buoyancy effect caused by gas filling, consolidating the frame of the weighting system, improving the positioning accuracy of the hanging system, monitoring the exact diverting position and controlling the temperature and humidity of the whole testing area. The uncertainty budget and preliminary test showed that the mass measurement uncertainty of gas was improved from 1.0 g to 0.5 g and the calibration uncertainty for CFVs would be better than 0.10 %(k = 2) over 3 bar–60 bar.