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M. D. Cazacu, R. M. R. Neacsu
A NEW METHOD AND DEVICE FOR GAS FLOW-METER CALIBRATION ON AIR AT HIGH VELOCITIES

The work presents the theoretical and experimental research on a new method, more precise and more advantageous than the ones already known, for the gas flow-meter calibration on air for however high flow-rates or flow velocities and without pressure loss. The research also deals with a patented device, which can be attained under the best technical and economical conditions even for the largest sizes. This is why we have made both the method and the device available for all interested companies and metrological laboratories.
The theoretical research refers to the permanent, with axial symmetry flow of a compressible ideal or viscous fluid, in its isothermic or adiabatic evolution towards the entrance of a circular pipe.
The movement is obtained by the numerical integration of Euler or Navier-Stokes system of partial differential equations, completed with the equations of thermodynamic evolution tor compressible fluids. We introduce the stream function and eliminate the pressure and density functions with unknown values along the boundary of the domain occupied by the fluid.
From experimental point of view, the used method consists in the gas exhaustion out of a large enough chamber with the following known characteristics: absolute pressure, temperature and humidity of the air and its recycling through a pipe.
These characteristics have been stabilised after a certain time interval and measured with good accuracy. We have also measured the relative pressure inside the pipe whose diameter is constant and known, and on which the calibration flow-meter is mounted under admitted metrological conditions.
What follows is the measuring in the pipe-entrance region of the relative static pressure of exhausted gas, the velocity distribution being uniform in the rst section.
The device for the gas ow-meters calibration on air for large diameters and high velocities is made in entrance section, followed by an intermediary pipe section on which the calibration flow-meters are mounted, and at the end of this pipe there is an exhaustion blower with a valve at its outlet, for the adjustment of the exhausted flow-rate.
The greatest advantage of this method is that it can be applied under any atmosphericat conditions and that it is not necessary to ensure the rigorous temperature conditions (20 ± 0.5 °C), which are required in the metrological laboratories and which are standardly imposed but exemplary. The only requirement is the ensuring of a certain permanence of the working gas parameters, but only during each measurement session.

Carl Carlander, Jerker Delsing
TEMPERATURE AND INSTALLATION EFFECTS ON SMALL COMMERCIAL ULTRASONIC FLOW METERS

Experimental work has been performed on a selection of small ultrasonic flow meters for water. This work was accomplished in order to investigate the influence of temperature and flow profile disturbances on the performance of flow meters in district heating applications.
The flow meters tested were all ultrasonic flow meters of sing-around typ e. The selection of flow meters contains in total seven meters of three different brands. All meters have a flow range from 0.015 m³ / h to 1.5 m³ / h. These meters are commonly used in heat meters in small district heating subscriber stations. The flow meters are presented without identification.
All tests were performed in a flow meter calibration facility and in a flow range including the minimum and maximum flow of each flow meter. In the tests three different water temperatures and three different installations were investigated. Water temperatures of 20 °C, 50 °C and 70 °C were used. These temperatures are representative for district heating applications. The installations tested involved flow meters mounted with long straight pipes both up- and down-stream representing ideal conditions, a single elbow and a double elbow out of plane both generating disturbed flow profiles. All set-ups are in accordance with the flow meter specifications.
The results demonstrate that both the change in temperature and the disturbed flow profiles introduce errors in the flow measurements. The change from 20 °C to 50 °C and 70 °C can cause a shift in meter performance larger than the specified maximum permissible error. Compared with the ideal installation the installations generating disturbed flow profiles cause errors up to more than 2 %. The errors due to temperature and installation effects have a bias to add when combined. This might lead to even larger errors.

Klaus J. Zanker
INSTALLATION EFFECTS ON SINGLE- AND MULTI-PATH ULTRASONIC METERS

This paper takes an analytical approach to examine the effects of swirl, asymmetry, pipe roughness, and Reynolds Number on the performance of a meter that utilizes a single bounce path through the center line (e.g., Daniel JuniorSonic) and a meter that employs four chordal paths (e.g., Daniel SeniorSonic).
A simple “power law” velocity profile is used to study the effects of pipe roughness and Reynolds Number. Mathematically generated axial velocity profiles, similar to those from bends and Tees, are used to study the effects of asymmetry. A solid body rotation is used to study the effects of swirl on the performance of both meters.
The single path meter requires typical corrections from 4 to 8% for changes in velocity profile due to variations in pipe roughness and Reynolds Number. The single path meter output varies about 6%, depending on the path orientation relative to the asymmetry and creates a bias error of about +/-3%.
The 4-path meter does an excellent job of integrating the velocity profile to give the correct flow rate over a wide range of both Reynolds Number and roughness values. The 4-path meter integrates the asymmetric profiles to give an answer within 0.1 to 0.3% of the flow, irrespective of orientation. Furthermore, it has sufficient diagnostics to recognize changes in operating conditions.
Simple bulk swirl, centered on the pipe axis, has no effect on the performance of either meter. This paper examines the effects of deviations from this simple ideal swirl.

E. van Bokhorst, M. C. A. M. Peters
THE IMPACT OF LOW-FREQUENCY PULSATIONS ON A DUAL- BEAM ULTRASONIC FLOWMETER

The impact of flow and pressure pulsations on flowmeters of various measuring principles, like turbine, vortex or DP-based flowmeters is well known and published at several occasions. To the author’s knowledge, there have been no publications on investigations regarding the impact of low frequency pulsations on commercially available ultrasonic flowmeters. The influence of high frequency acoustic noise, as caused by control valves, is part of several investigations and reported in recent publications. This paper describes the impact of low frequency, almost sinusoidal pulsations in the range from 25 to 100 Hz, which are imposed on a 4-inch, dual-beam, commercially available ultrasonic flowmeter.
The results of our experiments show a strong impact as a result of the aliasing effect for pulsation frequencies coinciding with the sample frequency or multiples thereof. Moreover considerable errors also occur if pulsation frequencies are below the sampling frequency. Errors in reading are over 5 % at a pulsation frequency of 25 Hz with a flow pulsation amplitude of 8 % rms.
It is obvious that ultrasonic flowmeters, as well as turbine, vortex or DP-based flowmeters, will not operate properly close to compressor stations as flow pulsation levels over 50 % rms occur even up to partial flow reversal in case of acoustical resonance. However also flow induced pulsations (FIPS) in metering stations, due to vortex shedding at T-joints, can be considerable in case of acoustical resonance and can result in misreading of the ultrasonic flowmeter. Typical frequencies of FIPS, determined by gas properties, operating conditions and piping geometry, are found in practice to be in the same range as the sample frequencies of the ultrasonic flowmeter.
It is not likely that the phenomenon observed is restricted to the meter under investigation.
The TNO Institute of Applied Physics is therefor working on a program in which the impact of pulsations on commercially available ultrasonic flowmeters for gas is investigated systematically.
This paper presents the first results of this investigation. In addition appropriate methods in signal processing will be investigated, so that measures can be taken to minimise the uncertainty in the flowmeter reading.
The aim of the future investigations is to improve the ultrasonic flowmeter by using appropriate signal processing, so that it can operate properly and without misreading caused by flow pulsations.

M. Watanabe, H. Okamoto
DEMONSTRATION TEST ON AND EVALUATION OF AN ULTRASONIC FLOW METER IN A HIGH-PRESSURE GAS PIPELINE

Osaka Gas conducted a demonstration test on an ultrasonic flow meter in a high-pressure gas pipeline. In this paper we report on the result of that test.

Jorge Gomez Sanchez, Sandro de Almeida Motta
ESTIMATION OF NOT MEASURED WATER VOLUME SUPPLIED TO RESIDENTIAL CONSUMERS, IN JUAZEIRO – BAHIA

The presented paper describes a work developed in a 180 000 habitants city in the Northeast of Brazil, that intends to characterize the water consumption profile of typical residential consumers and estimate the volume not measured and billed, due to the inaccuracy of the water meters, function of the age of installation.

Fernandes, N.F.
APPLICATION OF DATA RECONCILIATION TO AN ATMOSPHERIC CRUDE UNIT TO CALIBRATE INSTRUMENTS

Traditionally, data reconciliation has been used to obtain more accurate estimates of plant measurements. The accuracy is assumed to be improved by taking more information into account, ie additional measurements and knowledge of the process. Mass balance reconciliation has been used to get a consistent set of mass flow rates. Plant-wide material balance in oil refineries are providing an accurate representation of the interconnectivity of the entire plant complex and resolving and reconciling data discrepancies associated with plant operating data sources. The process of reconciliation is often an inexact and arduous task. Meters measure within tolerances, measure volume not mass, and often do not measure all the material movement in the plant. The task of reconciliation, then, becomes one of surmising the missing flows and determining where the errors are in the measurement system. Process data are generally corrupted by gross measurement errors. Using data reconciliation of process data we can use the operational performance of field instrumentation and plot calibration curves and the problematic instruments can be determined. Ploting reconciliation vs measured data we can produce a reliable mass balance for the distillation crude unit.

Josaphat Dias da Mata, Ricardo A. T. Pessanha, Roberto Guedes, Gualton Manhães, Hildebrando Pinho Filho
APPLICATIONS OF ULTRASONIC FLOW METERS IN THE PETROLEUM INDUSTRY

With the recent advances in electronics, the ultrasonic flow measurement technology was the one with the greatest development, allowing a wider use of these flow meters in various applications in the petroleum industry.
The measurement of gas and oil at the inlet (import) and outlet (transfer) points, among other internal applications on an oil production platform, is essential for the volume balance and a good control of several properties of the fluid to be transferred.
A critical point in this balance is the calculation of the flared gas volume. Ultrasonic technology is able to do it, even considering critical flow rate conditions, big diameters, low pressures and huge turn-down, thus permitting a better process control.
Some types of multibeam ultrasonic flow meters for liquids present very low uncertainty, allowing their use as a reference (calibration) flow meter. Due to this feature, this type of meter presents great advantages in applications such as custody transfer, tanker offloading, transfer lines with high flow rates, etc.
It should be highlighted that the ultrasonic flow meters have no intrusive moving parts, therefore minimizing the head loss. This characteristic confers an additional benefit to the flow meter, so that it needs less frequent maintenance, if compared to the traditional mechanical flow meters, such as positive displacement and turbine flow meters.
The objective of this paper is to present some oil and gas applications of ultrasonic flow meters, which have generated advances in operational control, reliability in flow measurement, besides an updating of this new metrological scenario in Brazilian oil sector.

H. H. Dijstelbergen, H. Bellinga
A NEW ULTRASTABLE TRANSFER STANDARD FOR TCC’S NEW HIGH PRESSURE GAS METER CALIBRATION FACILITY

Tests are reported on a 10-unit Rotary Piston Prover system that is installed at the TCC high-pressure gas meter testing facility. The paper also describes new tests that were carried out with the Rotary Piston Prover concerning its temperature dependence. Tests against a Bell Prover are also reported.

Wan-Sup Cheung, Kyung-Am Park, Jong-Seung Paik
MEASUREMENT UNCERTAINTY FACTORS OF ACOUSTIC FLOWMETERS

This paper addresses uncertainty factors associated with the acoustic flowmeter developed in KRISS. Repeated experimental attempts have been made to investigate their effects on the measurement accuracy of the flowmeter and its robustness in various experimental conditions. The attempts have enabled us to sort out the two major uncertainty factors of the acoustic flowmeter; the measurement errors of the acoustic pressure in the pipe and the acoustic wave reflection characteristics (the ratio of the incident wave to reflected one). Their effects are in details discussed. These findings are shown to lead to a new method that can present more accuracy and robustness in measuring the flow velocity in the pipe. The proposed method decomposes the measured acoustic pressure into the incident and reflected wave components and then estimates the flow velocity by choosing one or both of the decomposed wave components. Their choice depends on the acoustic wave reflection characteristics inside the pipe. Since the Mach number is estimated by using the least squares method, it is found to be the best-fitted result. In order to make those points clear, experimental results will be demonstrated in this paper, including the simulation results that were not possible to implement experimentally.

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