'GAS-OIL PISTON-PROVER', A NEW CONCEPT TO REALIZE REFERENCE VALUES FOR HIGH-PRESSURE GAS-VOLUME IN THE NETHERLANDS

摘要

The paper describes the recently developed "GOPP" – Gas Oil Piston-Prover. This primary standard for high-pressure gas-volume is created to realize units of volume at various pressures for the Dutch National traceability-chain of high-pressure gas-flow measurements. The paper presents the design, working principle, simulation calculations and first results to realize a calibrated rotary-piston gas-meter. Furthermore, the actual physical process is compared to simulation calculations, and temperature characteristics are discussed. With internal harmonization processes at NMi VSL with 'input' reference values from the three other primary standards, viz. DDD-conventional, DDD-extended pressure level and NMi TraSys, the aim of 0,1% uncertainty at 4.000 m~3/h and p = 60 bar is within reach. This will improve the uncertainty as well as the stability of the Dutch National reference values considerably. The developed Gas-Oil Piston-Prover has the potential to become an important primary standard at NMi VSL, generating straight-forward Reference Values for high-pressure gas at a desired pressure. The gas can be of any nature, but the major aim is Natural Gas. The paper presents describes the design, construction, working principle and features of a hydraulic driven piston-prover system. A 12 meter long, 600mm bore piston-prover is used for the realization of Reference Values for Gas-Volume at any pressure between 1 and 90 bar and any type of Gas. The paper explains the coherence between the Gas-Oil Piston-Prover system and the other available traceability generators. Following the philosophy of NMi, a "tripartite" traceability-chain for high-pressure gas-flow Reference Values is created. GOPP is one of the current developments at NMi to reduce the uncertainty of its traceability-chain considerably. The paper shows block diagrams, describing the coherence between physical equilibriums, simulation calculations and graphical simulations, compared to the results of full-scale experiments with a special duo-rotary piston-meter. A method is described to demonstrate an absolute leak-free piston-seal operation. Also a special measuring method was designed for the determination of the average gas-temperature inside the expanding measuring-chamber during the movement of the piston. Finally, real-time temperature and pressure readings, as well as the first calibration results of a duo-rotary gas-meter, established values for repeatability of the piston-prover system and first estimates of uncertainty budgets will be presented.