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The result of a chemical measurement is consequence of a set of steps that begins with sample selection. The aim of this study was to evaluate the relative importance of the sampling in overall measurement uncertainty, taking as study case physicochemical measurements of diesel. The empirical method used was by duplicates, and the treatment of data sets was performed by four different statistical techniques: classic analysis of variance, robust analysis of variance and two different Range Statistics models. The choice must be backed by previous evaluation of data set in terms of normality, independence, presence of outliers and homogeneity of variance. It was found that Range Statistics produced most reliable results under different premises and for the variety of physicochemical parameters evaluated. Robust analysis of variance failed indicates proper influence of sampling even it is a test designed to work under the lack of some of the proper premises.

This study evaluates the results of efficiency and consumption tests on gas household appliances and their influence on the classification of the Brazilian Labeling Program. Historically, based on results in interlaboratory comparisons, there is a doubt concerning if the algorithms correct properly the differences among different altitudes. Data from efficiency and consumption tests were collected in two cities with different altitudes, and the proposed calculation methodology is compared with the traditional one. The results show that the arithmetic average, used in the calculation of the efficiency of the burners on the stove table, justifies being replaced by the weighted average, after evaluating the behaviour of the data and treating outliers. The uncertainty of the efficiency and consumption tests was not enough to change the classification range of the product's energy efficiency label. It is concluded that statistically a difference is observed between the results at sea level and at altitude above sea level; since the tests were applied by the same operator using the same apparatus, the only parameter that leaves a doubt is the algorithms for the correction of the altitude. Shortly, this study will be part of a revised Brazilian standard.

In any commercial transaction, the presence of tolerances from specification limits is essential to ensure that the true value of the property of interest is sufficiently close to the specification value with a mutually agreed probability, so that there is no litigation between the parties. In order to meet this requirement, this tolerance is treated elegantly as a “toast” or more technically as a superior quality that the customer receives—giveaway. This work presents a new methodology for determining the tolerance limits of critical properties in some fuels, based on the reproducibility, on the difference between the averages of all acceptable results of each laboratory and on the specifications derived from the Brazilian National Agency for Oil, Natural Gas and Biofuels. Applying this approach to flash point by tag closed, final boiling point, volatility (95 % evaporated temperature), electrical conductivity and total sulfur content of some fuels and by means of a hypothesis test, the results show that this methodology was validated for most of the proposed new limits.

Calibration acceptance criteria for pressure and temperature measuring devices used in orifice plate gas flowmeters were specified. The study was motivated by the introduction of a Brazilian regulation that specifies technical and legal requirements for in-field measurements of oil and gas flows. In compliance with international best practices, the applicable regulation, which establishes uncertainty levels for flow measurements (1.5% for fiscal/custody transfer measurements and 2% for appropriation measurements), did not set up limits of acceptance of uncertainties associated with pressure and temperature measuring devices. The effects of these uncertainties in measurements were evaluated. By making use of the Design of Experiments and Response Surface Method (RSM), acceptance criteria were sought to comply with the applicable regulation. The use of the methodology proved to be very useful as low uncertainties were obtained in all ten metering stations investigated. In the worst cases (in three stations only), uncertainties were lower than 0.2% of the correspondent full-scale reading. The response surface methodology also showed that the minimum measuring capacity to meet the regulatory uncertainty requirements are 0.05% for differential pressure calibrators and 0.01% for the static pressure (relative to the full-scale reading).

This paper discusses the conception, construction and validation of a gravimetric system conceived as an alternative measurement standard for calibrating liquid flow meters. The ability to evaluate a large mass of a working fluid by measuring, with much lower uncertainty, a smaller quantity of it, reflects the innovative character of the proposed calibration system. In this work, the mass of water (over 10 tons) retained in a large squared (1.50 m × 1.50 m) cross section reservoir (5 m high) is evaluated by weighing a mass of water confined in a much smaller reservoir (0.0835 m diameter, 5 m high), hydraulically connected to the first. A low capacity weigh scale (full scale: 32 kg; resolution: 0.10 g) is used to weigh, under static condition, the water in the smaller reservoir, whose liquid level is the same of the large storage reservoir. The metrological reliability of the proposed gravimetric system—assessed through the propagation of all impacting measurement uncertainties—falls in the range 0.018 % to 0.055 %, depending on the volume of the working fluid transferred throughout the calibration process (varying from a minimum of 0.001 m3 to a maximum of 0.022 m3).

This paper discusses metrologically the best practice regarding the calibration curves applied to H2S mass fractions determination in natural gas by gas chromatography with sulfur chemiluminescence...

Ractopamine is used as an animal feed additive, but its adverse effects led to the necessity of the current monitoring programs of ractopamine residues in food products, so its reliable quantification is indispensable. This work aims to demonstrate the stability of solutions of ractopamine used for calibration of a liquid chromatography–tandem mass spectrometry method. Naturally contaminated samples with ractopamine were quantified using solutions prepared on different days. The stability study was based on an empirical model that considered a straight line (slope = 1) to describe the degradation mechanism. No significant change in the slope was detected. It could be concluded that solutions underpinning calibration curves at two different working intervals were stable for at least 11 months and 5 months, respectively.

International standards propose maximum uncertainties for custody transfer measurements, without establishing maximum permissible differences in the operations between two systems. It is up to the suppliers and customers to negotiate this parameter, which frequently causes disputes because a fixed value is proposed. This study aims to apply a methodology to evaluate the maximum permissible differences in LPG operations for custody transfer measurements for each particular operation using hypothesis tests based on measurement uncertainty instead of using pre-established values. The results showed that, in an isolated system, unlike other methods, environmental conditions do not influence the mass measurement method and its uncertainty. No maximum permissible difference of LPG transferred mass between tank trucks and metering stations exceeds 1.0%; in contrast, when a storage sphere is part of the one of the measurement systems, this parameter depends completely upon the operational conditions, and definitely, a unique value should not be considered.

This paper presents a method for measuring flow rates in pipelines based on the flow induced vibration principle using water as fluid, eliminating the need for interrupting the flow and opening of the pipeline for installation of traditional water flow meters. Experimental measurements are carried out in an accredited laboratory for calibration of rate flow meters and a metrological validation, followed by an uncertainty evaluation, are presented. Data analysis is accompanied by a method of optimization that minimizes adjustment errors of measurement using regression by parts and by the selection of the optimum period to estimate more accurately the flow rate. The results meet the specifications of Brazilian Metrology Institute.

A meter proving factor can be considered as a calibration parameter, by expressing the ratio the reference volume and the gross volume of liquid passed through a meter. The international guideline recommends Dixon's test for outliers to a meter proving factor set. However, the literature says that this statistic test is restricted only to data with Gaussian behavior, besides of not to be able to detect and treat two outliers at the same time. Here, Gaussian behavior of the meter proving factor set is evaluated, then different parametric and nonparametric approaches for detection and treating outliers applied to turbine meter proving factors for custody transfer of liquefied petroleum gas are compared. Afterwards, this effect is evaluated in relation to the number of outliers and how this handling affects the variable range criteria for expanded uncertainty in average meter proving factor. The results show that different average meter factors can be reached for each nonparametric and parametric test; anyway, no statistically significant effect between them is noticed.

The low-quality of automotive fuels may lead to the generation of pollutants harmful to both environmental and human health. The quality evaluation of automotive fuels requires a multiparameter conformity assessment, which may lead to an increased total risk of false conformity decisions even if all parameters comply with the acceptance limits. Thus, the aim of this work was to propose the establishment of multivariate acceptance limits in order to ensure a reduced total risk of false conformity decisions applied to automotive fuels analysis. Particular and total (consumers’ and/or producers’) risks were estimated using frequentist (specific) and Bayesian (global) approaches. Multivariate acceptance limits were estimated using Monte Carlo method, adopting an appropriate multivariate coverage factor (k’) defined using MS Excel Solver function. The definition of multivariate acceptance limits ensures a total risk below the maximum admissible risk (typically 5%) and was successfully employed in the conformity assessment of automotive fuels (diesel and gasoline). The employment of the multivariate acceptance limits may be useful in the conformity assessment of several multiparameter products.

The goal of this manuscript is the use of the statistical methods to analyze differences caused by the application of the correction methods defined on different standards for the measurement of the volume of liquid petroleum derivatives. This correction is necessary because pressure and temperature variations can cause differences between measurements made by the customer and supplier due to operational condition variations. To standardize this measurement, it was established that all volumes used on transactions in Brazil should be corrected to a base condition (20 °C and 101.325 kPa). To study these possible differences, the applied methodology uses statistical distributions that model the density of the products during the production process and, i.e., uses data collected during certain periods. Corrected density values are then obtained for each method. With these values in hand, a hypothesis test based on measurement uncertainty shows that numerical differences don’t always have statistical significance.