LAUDA Tensiometer TD 3

The ring/plate method of measuring the surface and interfacial tension of liquids is an established method with future potential: the increasing demand for surface active additives and proof of these in quality control requires fully automated and user-friendly equipment. As a stand-alone device, the compact, fully automated TD 3 ring/plate tensiometer with LAUDA Command remote control offers everything that is needed, both in the laboratory environment and for use on-site.

At the touch of a button, surface and interfacial tension can be measured easily, calculated precisely and reproducibly, printed, saved and optionally transferred to a computer.

LAUDA TD 3, the successor to TD 2, comes with a new design and new technical features, some of which are unique. As such, e.g. the world’s smallest thermostat, the LAUDA PTT Peltier thermostating unit, is easy to insert into the device. The temperature of the measuring samples can be set from 5 to 80 °C extremely quickly, conveniently and with the smallest space requirement. The TD 3 determines the interfacial/surface properties of organic and inorganic liquids (liquid/liquid or liquid/gaseous), dispersions, emulsions including for the development of surface active substances such as surfactants and emulsifiers and as evidence of these in sewage and bodies of water.

Application example: Control of cleaning water

Task: Even the smallest residues of detergents in beverage bottles, beerbarrels etc. have a negative effect on frothing and must be avoided. A surfactant analysis would take too long and would be too expensive. Summary information about surfactant pollution is needed here by means of a measuring method that is quick and easy to execute, yet also precise.

Solution: By measuring the surface tension with the TD 3, e.g. using the ring method, and by comparison with clean water, it is possible to quickly check whether the rinse water contains residues of surfactants (down to the range of ppm). Here, clean bottles are filled with distilled water and the surface tension is then measured with the tensiometer. Even the smallest impurities will reduce the surface tension of water. The integrated PTT Peltier thermostating unit ensures adherence to a temperature stability of ±0.1 ºC, in accordance with the standards

Application example: Aging of insulating oils

Task: The insulating properties of oils in transformers deteriorate during operation as a result of the oxidation of the oil, e.g. as a result of the penetration of water or the absorption of products from the decomposition of the cellulose in the winding papers. This silt severely impairs the winding cooling and therefore impedes heat dissipation. In turn, this build-up of heat results in severe aging of the winding paper. It must always be ensured that the oil is changed or recycled routinely.

Solution: The interfacial tension, which is easy to measure with the TD 3 even when used on the move, is an indicator of the quality of the transformer oil. This test is a measure of the concentration of the polar molecules in the oil, which develop during the aging process. The greater this concentration, the lower the interfacial tension and therefore the greater the silting tendency of the insulating oil. Interfacial tensions of fewer than 15 mN/m are indicative of possible silting. The integrated PTT Peltier thermostating unit keeps the temperature absolutely constant during the measurement and is therefore compliant with the ±0.5 °C required by ASTM D971.