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Yuan Pingfan, Renjia , Hemin
The Present Traceability hierarchy of Natural Gas Measurement in China and It's Prospect

With the development of natural gas industry in China, turbine flow meters, Vortex flow meters and Ultrasonic flow meters have been applied nationwide in recent years. It changes the fact that orifice flow meters used to cover about 95 % market of natural gas measurement. Those different flow meters are used to adapt to various process installation conditions.
Meanwhile three traceability chains have been established in southwest and northeast of China for 10 years. The test facilities, management, inter-lab comparison and service in-situ has been promoted greatly, even to international level. The Nanjing Calibration Station will be built up within 3 to 5 years. By then the traceability hierarchy will become more perfect in China. It is also related to some legislative problems. The present configuration and prospect of the traceability hierarchy in China is presented in this paper.

Min Wei, Xia Shouhua
Research of the mobile ultrasonic gas flowmeter as work standard

Now, most gas flowmeters are taken to the special verification station to test (verify or calibrate) by manufacture in the world. It's obvious that shortcoming and wasting.The ChenDu Verification Branch (in brief CVB) imported a set of mobile gas ultrasonic measurement system for nature gas which is much advancer of the world from the Instromet company in Holland. After the gas ultrasonic meters have been tested in CVB, the system's performance is proved that it work very well and also can meet the requirement the nation build the mobile work standard for flowmeters in the field. It inaugurate the new epoch which use the mobile gas flow verification system to test (verify or calibrate) those gas flowmeters in the field.

Duan Jinqin, Liu Chunyan, Chen Huiyu, Zhao Baorui
Research of Improving Accuracy of the 3-ton Electric Balance for Gas Flow Measurement

There is a professional 3-ton electric balance for gas mass flow measurement in Chengdu Verification Branch for Natural Gas Flow of National Crude Oil Large Flow Rate Measurement Station. The weighting range of this balance is 0 kg to 110 kg, the minimum sensible mass is 1 g, and the shift of indication value is no more than 2 g (P = 95 %). It has been proved stable and reliable during its 8-year usage. This article brieves the method of improving the original circuit control system by applying advanced electric technology. Using this method, the shift of indication value can been reduced to less than 2 g and the balance can work even more stable. In addition, the author introduces an indirect weighting method to reduce the negative effect caused by the balance crossbeams and the hanging weights used after many years. Thus the accuracy of the electronic balance can be improved.

Wolfram Bremser, Bodo Mickan
Harmonised Values and Reference Functions in Key Comparisons

Key comparisons in the field of flow measurement have some peculiarities with impact on data evaluation and performance assessment, in paticular on the caluclation of the key comparison reference value (KCRV). The normal KC approach which assumes that all measurements in all laboratories are made at prescribed nominal sampling points faces problems in practical implementation. Furthermore, it is normally assumed that values submitted by participants are independent of each other. It is well-known that this assumption may not hold in specific cases since some of the factors which influence the uncertainty may be the same in all or at least a couple of laboratories. The paper discusses the influence of the above factors. The problems are handled by calculating key comparison reference functions (KCRF) instead of series of isolated KCRV, and by correctly evaluating, and accounting for all correlations present within the data sets.

Wu Jian
The Middle Range Gas Flow Standard of SPRING Singapore

An auto-bell prover was set up at SPRING Singapore for the calibration of gas flow meters in the flow range of 3 m³/h to 100 m³/h or 1 to 33 g/s (dry air). The gas flow rate of the bell prover was determined by a primary method based on pressure, temperature, time and displaced volume measurements. The evaluations of the measurement uncertainties were carried out at the Gas Flow Laboratory of SPRING Singapore. The relative expanded measurement uncertainty was estimated to be less than +/- 0.2 % of readings. The performance of the auto-bell prover was checked using two transfer standards that were calibrated at National Institute of Standard and Technology (USA). The results are satisfactory.

Harvey Padden
Uncertainties And Inter-Laboratory Comparisons of Dry Piston Gas Flow Provers

Dry piston provers are similar in nature to conventional mercury-sealed flow provers, with the exception that the viscosity of the gas forms the seal across a very small (< 10 µ) section. As a result, very small, portable provers can be produced. Calibrations can be performed with the accuracy, primacy and large dynamic range of the earier mercury-sealed provers, but far more rapidly. The transportable nature of these primary instruments also makes them very useful for the inexpensive, ongoing harmonization of laboratories.
Our latest uncertainty analysis shows a combined expanded uncertainty of less than 0.08 % over the range of 5 to 50,000 sccm. Although we made every effort to perform an accurate analysis, empirical verification of any uncertainty analysis is necessary. At this level, the only means of verification is through peer-to-peer inter laboratory comparisons.
As a result, we have performed informal comparisons of a single pair of provers with a number of national and private laboratories on three continents. We compared for reproducibility with respect to different national laboratories and over time, with transportation and between overlapping cellranges. In addition, and we compared newly manufactured provers with the original pair to establish reproducibility with manufacture. Typically, the provers exhibited discrepancies (within their specified range) of less than 0.1 % in comparison with critical flow venturis at NIST and NMIJ, with the possible exception of the 50,000 scm point. At the highest flow, the original prover exthibited a discrepancy of 0.15 % to 0.2 %. A second prover later showed a discrepancy of 0.035 %. We must conduct further investigations to determine the linearity of the design for flows above 30,000 sccm.
Here, we will present an introductory summary of the uncertainty analyses, details of the comparison methodology, data on potential experimental error sources (such as inventory volume), the comparative data, and the methods of data analyses used. We will also discuss our ongoing research at the lower limit of this design's useful range (approximately 1 sccm), where leakage is not necessarily constant and conventional viscosity may not apply.

Cheng-Tsair Yang, Jeng-Yuan Chen, Jiunn-Haur Shaw
A New Air Velocity Standard by Using LDV and a Wind Tunnel at CMS

Though air speed measurements are daily routine in many industries, calibration is still a problem due to the lack of standard. Though the Center for Measurement Standards (CMS) has established a calibration facility since 1997, the block effects resulted from small wind tunnel section constrained the devices to be calibrated. In this paper, a facility comprises a redesigned wind tunnel and a LDV with expanded lens was tested of its performance to estimate its uncertainty of measurement. Firstly, the expanded LDV probe was readjusted of its beam crossings and calibrated of its fringe spacing. This improved the uniformity of fringe pattern in the measuring volume to obtain accurate fringe spacing that serves as velocity coeficient and to reduce the uncertainty of LDV measurement to be less than 0.1%. The tunnel was tested under air speed from 0.5 m/s to 25 m/s. Turbulence intensity, long-term flow stability, and unifomity of velocity profiles are all considered as significant sources of measurement uncertainty. The uncertainty analysis indicated that the relative expanded uncertainty for regular calibration could be less than 0.5 %.

Isabelle Care
Characterization of a New Calibration Wind-Tunnel within Low Air Velocity Range

Air velocity is a quantity often used in specifications of industrial processes or buildings. In these applications, the velocity is generally below 1 m·s-1, the air temperature can be different from ambient one and the air can flow in any direction whatever. Furthermore, to reach minimum uncertainty measurements, a minimum calibration uncertainty of the used anemometer is needed as well as a calibration as close as possible to measurements conditions. To answer these needs, CETIAT has built a new anemometers' calibration test rig. Its evaluation is presented in terms of stability, homogeneity on humidity, temperature and velocity fields as well as calibration uncertainty.

Vahit Ciftci, Hakan Kaykisizli
UME Gas Flow Rate Measurement Systems and the New Wind Tunnel with LDA

National Metrology Institute of Turkey, UME, has partially completed the new gas flow velocity and gas flow rate measurement systems. In this article UME primary and secondary gas flow measurements systems for air at atmospheric conditions will be explained briefly.
In the new gas flow laboratories, velocity measurements and anemometer calibrations are realized with a 2D Laser Doppler Anemometer .Two dimensional velocity measurements up to 40 m/s can be done in two different tunnels that have dimensions 500 × 500 mm and 250 × 250 mm.
The wind tunnel system is constructed parallel to a gas flow measurement system. This turbine gas meter test rig is designed for a maximum flowrate of up to 19500 m³/h with an uncertainty less than 0,5 %. Another gas meter test rig for air at atmospheric conditions is designed and constructed to operate parallel with a sonic nozzle test rig. This system will be used for gas flowrate calibrations in the range of 50-5000 m³/h. Until the planned sonic nozzle test rig is added to this system, the uncertainty can be declared as 0,3 %. Primary standard Bell Prover and the low flow secondary standards Wet gas meter and Bubble Generators completes the traceability chain for gas flow at atmospheric conditions.

Aernout F. Van den Heuvel, Robert Kruithof, Henk J. Riezebos
Reproducibility of the Bernoulli Laboratory in Westerbork

This paper explains the way in which the traceability of the Bernoulli laboratory in Westerbork is organised and shows the reproducibility that is determined from the measurement results involved.

Page 164 of 977 Results 1631 - 1640 of 9762