Metrological evaluation of several Coriolis mass flowmeters

Abstract

This paper is the final report of an evaluation and research project on the metrological performances of six different mass flowmeters of the Coriolis type which were extensively tested, under identical operating conditions, at the IMGC flow measurement laboratory, making use of the Italian national standard calibration facilities. The first results of the evaluation project, already detailed in a previous paper, are also briefly reviewed.evaluate the metrological characteristics of several commercially-available CMFs. The main aims of this investigation are: 8B making a comparative evaluation of as many CMFs of different design as possible, by testing them at an independent laboratory in identical conditions of practical interest to users; improving the knowledge of the metrological characteristics exhibited by a representative sample of CMFs, in order to allow a basic assessment of the performances of the whole class of such instruments.The test programme and the first results of this research were reported in Cascetta et al (1992) and are here briefly recalled. Further, this paper presents the results of the second part of the project, which consisted of on the influence of fluid density and fluid temperature. The extensive set of data given in both papers, which summarise many thousands of measurements, provides a further contribution to the documented characteristics of this type of flowmeter. The metrological evaluation programmeThe tests, as agreed with each manufacturer, include calibration of each meter:~ in water, by varying pressure (up to 400 kPa) and temperature (up to +80°C); in a test fluid (MIL-C-7042-B type II) in substitution for JP4 kerosene (in the following text called simply 'JP4 k~rc~sene'), whose density and viscosity at 20°C are respectively 768.5 kg/m3 and 1.~'l mm2/s; in a two-phase fluid, namely water mixed with a small amount (up to 10% in volume) of air bubbles. It must be stressed that this experimental evaluation was performed on a single instrument for each manufacturer. Therefore, the test results do not provide justification for a quality judgement on other flowmeters, and even less to a whole product line of instrumentation. It should also be noted that, by now, many improvements have been incorporated in most CMFs available today, owing to the fast development of this comparitively young technology.The model that each company was asked to provide was chosen in view of comparing meters with similar measurement flow ranges: more precisely, with full scale (FS) values as close as possible to each other.These FS values, for use in water at room temperature and low line pressure, ranged between 2.8 kg/s and 4.5 kg/s. All the CMFs chosen are equipped with DN 25 flanges.All flowmeters but one were tested by measuring their DC output across a standard resistor: this choice, according to previous experiences at the IMGC flow laboratory, is thought to be fully adequate and more reliable with respect to electromagnetic noise (Wade and Dandridge, 1988). Just one flowmeter, instead, was t...

Measuring of compressed natural gas in automotive application: A comparative analysis of mass versus volumetric metering methods

“…4) [2]. The reference meter (E) was positioned after the turbine meter (A) and before the multistage compressor (C) and the gas storage vessel (D).…”

“…The main disadvantages are: (1) on-board storage and low density requires: CNG (at >200 bar) or LNG (at -180 • C); (2) cost and weight of on-board storage vessels; (3) cost/complexity/possibility of refueling infrastructure; (4) limited availability of gas fueled engines/vehicles.…”

“…However, the use of natural gas in automotive applications [1][2][3][4] implies a metrological dichotomy, since the natural gas is measured by means of a volumetric method when it is supplied to a petrol pump, while CNG is measured by a mass (Coriolis) method when the gas is loaded into the vehicles. These different measuring approaches can cause misalignments between the two measuring systems, causing discussions and disputes.…”