The Traceability Improvement and Comparison of Bell Prover as the Indonesian National Standard of Gas Volume Flow Rate

Traceability is urgent to guarantee the truth of measurement, particularly for National Standard. Although a bell prover facility has established as the national low pressure gas flow standard of Indonesia since 2008, the measurement capability (15 to 1400 L/min, U-95 = 0.20%) of the bell prover has not been traceable to SI Units. Moreover, displacement values provided by the bell prover's manufacturer by rotary encoder method are still used. The limit detector by optical sensor to measure displacement is worthy to achieve dimensional traceability which can be switched by ultrasonic sensor for reasonable solution. The aim of this study is to improve the traceability of the bell prover by reasonable solution and then validate the gas volume flow rate measurement by inter-laboratory comparison. The Center for Measurement Standards (CMS), Industrial Technology Research Institute (ITRI), was invited to participate in the bilateral comparison, and a gas turbine flow meter was used as the transfer standard. The bell prover has been successfully traceable to SI units, particularly displacement measurement through flying start/stop method by limit of ultrasonic sensor (250 to 1200 L/min, U-95 = 0.80% passing assessment report). Despite having larger uncertainty than manufacturer specification, the results are better for more in of layer comparison. Because the effect of turbine drift should be a concern, the gap of measurement time for inter-laboratory comparison is recommended to minimize as many as possible. Furthermore, the measurement range of bell prover should be reduced as reasonability purpose.