Fong-Ruey Yang, Yi-Lin Ho, Wen-Bin Wang, Jiunn-Haur Shaw, Tsai-Wang Huang, Jyh-Rong Wu, Zhong-Yong Chen, Yun-Ho Cheng, Zhi-Xiong Su, Trank Li
Traceability Calibration from Primary Standard to On-Site Ultrasonic Flowmeter
This paper describes the traceable calibrations from primary standard to on- site natural gas ultrasonic flowmeters. In practice, the National Metrology Laboratory constructed a gravimetric type air-flow calibration system with sonic nozzle array as the working standard in 1993. The flow measurement capacity of this primary standard at 1 bar and 20 °C is from 15 m³/h to 18000 m³/h with operating pressure range from 1 bar to 60 bars. A re-circulating high pressure gas flow measurement facility was constructed at Chinese Petroleum Corp in southern part of Taiwan. The pressure range is also from 1 bar to 60 bars with flow range from 20 m³/h to 4000 m³/h under actual pressure condition. The transfer standards of this re-circulating facility are four 6” Instromet ultrasonic flowmeters. The expanded uncertainty of these four transfer standards calibrated by NML compact nozzles was 0.18 %. For the Da-Tan distribution and metering station in Taiwan, four Sick 12” ultrasonic flowmeters are used as transfer standards. These were calibrated by the re-circulating facility regularly and expanded uncertainty for the transfer standard was 0.24 %. Subsequently, six on-site Daniel 24” ultrasonic flowmeters are calibrated by transfer standards with the expanded uncertainty of 0.26 %. The pressure effect of the ultrasonic flowmeter was tested and proved insigificant. The calibration curve of ultrasonic flowmeter at specific pressure can be used at any pressure.
