The criteria for classification of averaging impact tubes are introduced (the art of measuring of reference pressure, the construction of the primary device, the number of ports and their displacement, the way of taking of total pressure) and some technical solutions are presented. Mathematical model of averaging impact tube is introduced and the correction factor is derivated. This factor takes into account the fact, that the output signal from differential pressure transducer is proportional to the average of dynamic pressures (velocities in second power) but the flow-rate is proportional...
Velocity profile is the definition given to the distribution of velocity in the axial direction over the cross-section of the pipe. This distribution is not usually flat and can vary dramatically depending on the properties of the fluid and the configuration of the pipe in which it flows. Fully developed flow is well defined for most values of Reynolds number however distorted flow is not. Ultrasonic flowmeters are affected by such distortions in the flow profile often resulting in erroneous measurements. For this reason correction to or prediction of distorted profiles has sparked great...
This paper presents the details about in-situ calibration of natural gas orifice meters in China, and discusses some actual calibration results made in the custody transfer metering station of natural gas transportation pipeline from Shanxi to Beijing.
A special fluid flow diverter was developed and tested for the new water flow standard facility which is under construction now at PTB Braunschweig. It offers several new features and properties for improving the accuracy, e. g. variable rec- tangular nozzle, CFD designed influx pipe section and high precision electrome- chanical switching device. The paper describes design and test results of a first pro- totype in a water flow circuit.
The use of flow conditioners becomes necessary in flow measurement applications where the geometry of conduits does not allow complete development of the velocity profile upstream the flowmeter. In this paper the authors present a numerical analysis, based on finite volume technique, for the evaluation of flow conditioner performance under low level perturbation conditions. The use of non structured grids was necessary because of the complexity of the geometry studied. The results of the numerical calculations were used to evaluate the efficiency of different types of flow conditioners. The...
The paper reports about the profile measurement downstream of several perforated plates and their evaluation. Five different designs of perforated plates were investigated, which were: modified Zanker, Mitsubishi, two designs by company NOVA and a design by Laws. Every flow conditioner were tested in three different pipe configurations with different levels of axial profile deformation and swirl. The report focuses on development of the axial velocity profile. The evaluation was done not only by comparing the velocity profiles but also with respect to the error shift of turbine meters.
The new AGA 3/API 14.3 standard on concentric square edged orifice meters suggests that, if installation effects can be shown to be less than about 0.23 %, there is no need to apply any additional uncertainty to that of the basic discharge coefficient. This suggestion has revived interest in flow conditioners that can assure this performance without the need for long straight upstream lengths of pipe. A feature of the new standard is that it specifies performance acceptance tests for evaluating other flow conditioners, which were not included in the previous versions of the document. In this...
TransCanada Calibrations’ (TCC’s) new high pressure, large diameter calibration facility is designed to meet the needs of the changing natural gas industry. With year-around access to gas volumes in excess of 50,000 actual m³ / h, the TCC facility is designed to provide full range calibrations of flow meters ranging from 0.15 m (6 inch) to 0.75 m (30 inch) in diameter. In order to ensure that the facility meets user expectations of accuracy and repeatability, a round robin testing program was initiated by TCC. The CENTAUR (Canadian, European, North American, Turbine And Ultrasonic, Round...
There is keen interest in the total accuracy of flow measurements in industry. Total accuracy is defined as the accuracy of the whole measurement chain which can be determined only in a field calibration. Indmeas has for several years carried out quality maintenance work for industry using the radiotracer methods for field calibrations of liquid and gas measurements. Comprehensive data from these calibrations show that the dominating uncertanties of flow measurements in industry lie outside the flow meters themselves. The large error components, however, are often fairly stable and can be...