An Industrial Reference Fluid for Moderately High Viscosity

Abstract

In industrial practice, there is a demand for a reference standard for viscosity that is established for a readily available fluid to simplify the calibration of industrial viscometers for moderately high viscosities [(50 to 125) mPa · s]. Diisodecyl phthalate (DIDP) has been suggested as that reference fluid, and a number of studies of its properties have been carried out in several laboratories throughout the world, within the auspices of a project coordinated by the International Association for Transport Properties. That project has now progressed to the point where it is possible to collate the results of studies of the viscosity of the fluid by a number of different techniques, so as to lead to a proposed standard reference value which will be included in the paper. To support this recommended value, the various measurements conducted have been critically reviewed, and the sample purity and other factors affecting the viscosity have been studied. Density and surface tension measurements have also been performed. This paper does not describe the individual viscosity determinations carried out in independent laboratories because these are the subject of individual publications, but it does describe the ancillary studies conducted and their relevance to the viscosity standard. In addition, the paper contains recommended values for the viscosity of liquid DIDP. The samples of DIDP to which the recommended values refer are isomeric mixtures available commercially from certain suppliers, with a minimum purity by gas chromatography of 99.8 %. The recommended values result from a critical examination of all the measurements conducted to date and are supported by careful arguments dealing with the likely effects of the isomeric content of the sample as well as of other impurities. The proposed reference standard is intended particularly to serve an industrial need for a readily available calibration material with a viscosity close to that required in practical situations. To that end, the recommended value has an overall relative uncertainty of approximately 1 %. It is therefore not intended to supersede for the reference value for the viscosity of water at 20°C, which is known much more accurately, but rather to complement it.

Tris(2-ethylhexyl) trimellitate (TOTM) a potential reference fluid for high viscosity. Part I: Viscosity measurements at temperatures from (303 to 373) K and pressures up to 65 MPa, using a novel vibrating-wire instrument

“…As a consequence, there is, at present, a demand for new industrial viscosity standards with various viscosities, at high pressures and high temperatures. Industrial viscosity standards with adequate viscosity could be used for calibration and tests of industrial viscometers for use in-well, or on-line, at the adequate working conditions [1][2][3][4][5][6][7][8][9][10]. Since, in industry the range of viscosity of useful fluids varies over several orders of magnitude, a number of "industrial reference materials", covering a large spectrum of practical conditions, are required to calibrate or verify the calibration of those instruments [8].…”

“…Often, in industry the calibration of viscometers is made directly or indirectly, using certified reference fluids, which have viscosities traceable to standards from national metrological laboratories, obtained with capillaries calibrated by a step-up procedure, from the water primary reference to the corresponding viscosity [8]. For very viscous liquids this procedure can be time consuming and expensive.…”

“…For very viscous liquids this procedure can be time consuming and expensive. Moreover, those certified reference fluids are usually mixtures of oils, whose composition has only a general description [8]. In face of this, the viscosity of these fluids must be determined for each batch and its utilization should take place within strictly defined time limits.…”

“…As a consequence, the International Association for Transport Properties (IATP) has been developing efforts in order to respond to the demand of industrial viscosity standards [1][2][3][4][5][6][7][8][9][10]. In particular, IATP has proposed an industrial viscosity standard for moderately high viscosity [DIDP] and, more recently, has created an internal project regarding the search of a high viscosity industrial viscosity standard fluid, and at high pressures and high temperatures.…”

“…In fact, in the last decades, viscosity reference data of low viscosity fluids [12][13][14][15][16] and moderately high viscosity fluids [6,8,9], have been proposed under the auspices of STP-IUPAC and IATP.…”