In situ calibration of Coriolis flowmeters for high-pressure gas flow calorimetry

An in situ calibration method for small Coriolis meters used for high-pressure gas flow calorimetry is presented. The method has an accuracy better than 0.02%, at level one standard deviation. Two meters, both with a totalizer function, have been evaluated, and the total long-term accuracy of the best meter is ±0.11% at level one standard deviation.     

Novel application of gas chromatography in measurement of gas flow rate

Real-time volume flow rate of gas component for slowly changing composition mixtures is of chief importance for some special research applications. However, it is always difficult for us to achieve the goal by sophisticated gas flowmeter. In this study, we demonstrate two methods for the problem solution by the flow measurement of acetylene in unsteady gas flow based on online gas chromatography accompanying with a gas mass-flowmeter. For Method 1, high purity methane is applied as an internal standard and the volume flow rate of acetylene is obtained via coherent equations. Method 2 makes fully use of the online gas chromatography automated integration under fixed gas chromatography work conditions. Results have shown that both methods are feasible and effective, and Method 2 is more accurate than Method 1 with relative error less than 0.7%.     

Installation effects on vortex shedding flowmeters

Numerous measurements of the effects of pipe fittngs on vortex shedding flowmeters are carried out as a contribution to flow metering standards. A water test line of 150 mm diameter is used in the experiments covering a Reynolds number range of about 2 × 10⁵ to 10⁶. The effects of six kinds of piping configurations are examined at various upstream straight pipe lengths and all four kinds of liquid vortex shedding flowmeters, which were commercially available in Japan, are tested. The vortex shedding flowmeters are compared with a turbine meter in experiments designed to evaluate reproducibility of measurements. The uncertainty of the measured data is estimated at about 0.1%. It is found that the magnitude of each installation effect strongly depends on the design of the flowmeter. The experimental results are presented in detail and a table is given of the minimum upstream straight pipe lengths needed to suppress the effects to less than 0.5% for each of the tested flowmeters. This can be used as guidance in the installation of vortex shedding flowmeters.     

Analysis of signals from vortex flowmeters

The vortex flowmeter is used to measure the flow of fluids especially where the requirements include wide rangeability and the use of flowmeters with no moving part. It is common knowledge that process conditions affect the operation of a vortex flowmeter, and a customary approach is to introduce flow conditioners so that the measurement output from a vortex flowmeter conforms to specified standards. Some recent studies have shown how to apply signal analysis to the signal from vortex flowmeters to enhance performance, but the signal which has been typically analysed is the pulse train. In this paper,we advocate a new approach which involves detailed analysis of the unconditioned signal from the sensor prior to conventional signal conditioning. The results obtained from this approach open opportunities for the development of alternative signal conditioners and transmitters which not only enhance the quality of the measurement output from a vortex flowmeter but also make it possible to use the flowmeter for monitoring the condition of the plant.     

Progress in hydrodynamic oscillator type flowmeters

Vortex and fluidic flowmeters share common merits, but their working principles differ. Technical progress and the state of the art of these flowmeters are reviewed from a unified viewpoint of hydrodynamic oscillation of both the wake and jet. The problems to be solved for the expansion of vortex flowmeter applications are discussed, covering improvements in vortex frequency sensors and enhancement of application data.     

On-line viscosity measurement using Coriolis mass flowmeters

Industrial viscometers are available in large variety to measure for both Newtonian and non-Newtonian fluids. A simple system which uses the Coriolis mass flowmeter as a capillary tube has a growing range of applications. Employing the capillary principle, the rheological properties of time-independent Newtonian fluids and some non-Newtonian fluids can be successfully measured. The method applies readily available and proven components, namely mass flowmeters and differential pressure transducers. Basic viscosity calibration can be achieved with suitable software. To add viscosity measurement capability to an existing flowmeter site in most cases requires only the installation andd connection of a suitable differential pressure transducer.     

Effect of pulsating flow on Coriolis mass flowmeters

The last ten years have seen an increasing use of Coriolis flowmeters in the measurement of small flows of liquids. The performance of Coriolis meters under pulsating flow conditions was not well known, however. This paper presents some investigations on such flowmeters in the presence of monofrequent and polyfrequent pulsating flows. The linearity of the flow characteristics is checked mathematically and the mechanical resonances of the measuring tubes are determined. Two U-tube type Coriolis meters are tested and the measuring error resulting from the pulsation of the flow is examined. The investigations are carried out with monofrequent pulsation by a special test rig flow and with geared and piston type pumps (polyfrequent excitation).     

Installation effects on ultrasonic and electromagnetic flowmeters: a model-based approach

The paper describes the basic ideas of a model-based installation-effects analysis method and presents results from a collaborative research programme being conducted at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD, USA, and at Tampere University of Technology in Finland. The analysis method is based on a combination of flow modelling and flowmeter modelling. In this paper, installation effects on electromagnetic and travel-time-difference ultrasonic flowmeters are discussed. The installation cases are single elbow and double elbow out-of-plane piping configurations. The results show that significant shifts from ‘ideal’ meter performance can occur in such disturbed flow conditions. The flowmeter modelling results also show that these significant shifts can be reduced by altering the operational arrangements and performance characteristics of the meters. It is concluded that such flowmeter modelling can be very useful in: (1) redesigning flowmeters to make them less susceptible to installation effects, (2) constructing new meters, or (3) arranging special meter configurations to deal with specific disturbed flows.     

The weight vector theory of Coriolis mass flowmeters

In this paper a fuller and clear derivation of the weight vector theory of Coriolis mass flowmeters is given indicating its potential for the prediction of velocity profile effects in both the traditional kind of meter (vibrating tube) and the compact kind (vibrating element inside a duct).     

Effects of flow disturbance on an ultrasonic gas flowmeter

A series of tests are carried out to assess the effects of flow disturbance on a small dimension ultrasonic gas flowmeter. Flow disturbances generated by cone couplings, and single and double elbows are investigated. Measurements with a 100 D straight pipe upstream with a smooth connection to the meter body are used as a reference. Our measurements show that the symmetrical disturbance produced by a cone coupling at a 12 D distance from the transducer path does not impair the performance of the flowmeter. An asymmetrical disturbance, such as a single or a double elbow at the same distance, seems generally to give an underestimation of the flow velocity, resulting in reading errors of −1% or worse. Measurements with straight pipes of 10 D, 20 D, 40 D and 80 D between the disturbance and the flowmeter have also been made showing that 10 D can cause an overestimation of flow velocity. Increasing the length of the straight pipe generally decreases the error. More than 80 D straight pipe between the disturbance and the flowmeter is required to give a result within ±1% of reference conditions. The angle between the elbow plane and the transducer plane is changed from 0 to 315° in 45° steps. The meter error is plotted as a function of inlet angle, showing a clear relationship between these values.     

Design conditions for optimal dual bluff body vortex flowmeters

Examination of the performance of a large number of dual bluff body combinations leads to the conclusion that optimum repeatability of vortex shedding may be obtained with combinations satisfying certain basic conditions. One possible condition is the coincidence of the positions of maximum vortex strength for the individual bluff bodies which make up the combination. The aim of this paper is to describe the results of a test of the above principle using rectangular bluff bodies. The first stage is to find the mathematical relationship between the position of maximum strength and the depth of a single rectangular bluff body. The next stage is to use this relationship to find which combinations satisfy the above coincidence condition. These ‘optimal’ combinations were then tested against a number of ‘non-optimal’ combinations as controls. The overall conclusion is that the above condition is just one of five conditions underlying the design of optimum dual bluff body vortex flowmeters.     

Study on gas hydrates for the solid transportation of natural gas

Natural gas hydrate typically contains 85 wt.% water and 15 wt.% natural gas, and commonly belongs to cubic structure I and II. When referred to standard conditions, 1 m³ solid hydrate contains up to 200 m³ of natural gas depending on pressure and temperature. Such the large volume of natural gas hydrate can be utilized to store and transport a large quantity of natural gas in a stable condition. In the present investigation, experiments were carried out for the formation of natural gas hydrate governed by pressure, temperature, gas compositions, etc. The results show that the equilibrium pressure of structure II is approximately 65% lower and the solubility is approximately 3 times higher than structure I. It is also found that for the sub-cooling of structure I and II of more than 9 and 11 K respectively, the hydrates are rapidly being formed. It is noted that utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.     

Beta ratio, swirl and Reynolds number dependence of wall pressure in orifice flowmeters

Experimental work has been performed in an effort to gain a better understanding of the flow field inside orifice flowmeters and the pressure field generated on the walls of the pipe and orifice plate. As a part of a larger study, extensive wall pressure measurements have been made on the pipe wall from four pipe diameters upstream of the orifice plate to six pipe diameters downstream, as well as on both the upstream and downstream faces of the orifice plate. These measurements were performed for Reynolds numbers of 54 700; 91 100 and 122 800; for beta ratios of 0.50 and 0.75 with air as the working fluid. An adjustable swirl plate was installed, which was used to impart varying amounts of swirl into the flow upstream of the orifice plate. For each swirl case, Pitot and static pressure probes were used to characterize the upstream flow field while the pipe wall and orifice plate surface pressures were measured.     

Uncertainty study of fiscal orifice meter used in a gas Algerian field

Uncertainty variation of a fiscal orifice measurement system used in an Algerian natural gas exportation station is studied using data from a natural gas production field known as Gas Tin Fouye Tabankort (GTFT) located in the south-east of Algeria. The expected results are uncertainty calculus over a range of temperature and pressure variation and to the customs authorities’ allocation.In fact, each quantity of measured fluid flow has certain uncertainty and then the fiscal measurement station is very important for gas exportation, which means the income. Therefore, the pursuit of flow metering device uncertainty and its influence on the measured quantities in the transmission networks is very important.For that, the uncertainty caused by flowmeter in the measurement station causing economical revenue fluctuations is studied. The work was done to justify why there is a production decrease of hydrocarbons without identifying reasons during summer. The difference between the mass flow rate quantity produced and the transmitted value was important that is why our work is done to clarify exactly from where the problem can come.The measurements setting with two operating conditions (gas temperature and pressure) show that the uncertainty is dominated by seasonal temperatures and pressures variations which induce fluctuation in gas and pipe temperatures and influence the metrological performance of the transmitters. Indeed, the metrological measurement chain performance is affected also by these two operating conditions.The present work is done according to the ONML (National Legal Metrological Office) instructions regarding differences between the measured and the seller values represented by the mass flow rate.In natural gas transmission network, the important problem in the management and control of the network is represented by the unaccounted for gas, a quantity of measuring error which is to be considered in the equation of network balancing. One of the unaccounted for gas sources are the environmental conditions and systematic measurement errors.In this work, the calculation of the combined uncertainty of the mass flow rate measured by an Orifice fiscal gas metering plant is done. From the results founded, the authors confirm that the uncertainty in the measurement system causing by the climatic conditions generates unaccounted for gas.     

色谱分析仪在天然气计量中的应用

天然气各组分含量是天然气计量的基础参数,天然气气质的准确分析对天然气计量至关重要。气相色谱法是测量天然气组成最常用的方法,气相色谱法具有选择性高、分离效率高、灵敏度高、分析速度快等特点。本文介绍了Pro GC-2000天然气色谱仪在绍兴天然气门站输气管道处的成功应用,通过在线色谱仪实时取样分析,得到天然气组成、密度、发热量、沃泊指数、压缩因子等物性参数,并将结果及时输入流量计算机中,实现对天然气流量和能量的及时修正,确保天然气计量准确可靠。本文阐述了色谱分析原理、结果分析方法、天然气计量系统组成和工作原理等。     

The weight vector theory of Coriolis mass flowmeters — Part 2. Boundary source of secondary vibration

The purpose of this short paper is to draw attention to a boundary source of secondary vibration in Coriolis mass flowmeters. This is important in the calculation of meter sensitivity using the weight vector theory if the effect of fluid viscosity is to be taken into account in the vibrational flow.     

气相色谱-质谱法检测土壤中痕量芥子气

建立气相色谱-质谱选择离子检测土壤中痕量芥子气的方法。该方法采用二氯甲烷萃取土壤中的芥子气,萃取液经净化、浓缩,加入内标丁基硫醚后进行分析,可实现对土壤中0.02mg/kg芥子气的定量检出,且加标回收率大于70%,相对标准偏差小于10%。     

对人工煤气、液化石油气、天然气气相色谱分析方法的研究

燃气中包括人工煤气、液化石油气和天然气,它们各自的组分、含量不同,存在着一定差异,又具有一定的共性,国家标准中要用多台气相色谱仪、不同的色谱分离柱进行分析。本文研究用两台气相色谱仪、两套色谱柱、两种定量方法、可以满足3种气体的分析方法,所建方法在两个实验室,通过多年的日常分析考验,结果证明分离效果和分析方法重复性好,精度高,既节约了人力、物力又节省了时间,同时也能满足3种气体分析和国家标准的要求。     

A regression-based model for prediction of flowmeters calibration cost in oil and gas industry

Measurement of liquid flowmeters is one of the most expensive processes in the oil and gas industry. Estimating calibration costs for such flowmeters in the oil and gas industry is complicated task for the decision-making team. The difficulties arise as a result of the presence of numerous uncertain factors that influence calibration charges such as the fabrication of special tools and spools. Consequently, this paper proposes a data-driven approach for estimating the calibration costs of flowmeters in oil and gas industry. A regression-based model is developed to predict the future calibration costs of flowmeters. The factors that affect the costs of calibrating flowmeters are identified from literature and interviewing local experts. The results indicated that the most important factors influencing the cost of liquid flowmeter calibration include flowmeter size, calibration method, flowmeter type, flowmeter class and calibration factor. The developed model is validated using 577 new data points of flowmeters calibration costs. The findings showed the uncertainty of the proposed model within 98% confidence level. An accurate calibration cost for liquid flowmeter will help to manage the operational and services costs.