05-05-2012

In-Process measurement of kinematic viscosity

Viscosity is an important measurement parameter in the production of petrochemical end products such as fuel oils and lubricating oils. For the control of production processes, efficient process analyzers for the measurement of viscosity are indispensable. As for the method of determining viscosity, primary standards for petrochemical products (e.g. heating oil DIN 51603, diesel DIN EN 590, marine fuels ISO 8217) refer to standards describing capillary viscosimeters with high  temperature precision for the measurement of kinematic viscosity (e.g. ASTM D 445, ISO 3104, DIN 51562-1). According to the law of Hagen-Poiseuille, such viscosimeters use the mass flow of the liquid through a capillary and the pressure dropping along its length to calculate the kinematic viscosity. Due to the high temperature dependency of viscosity, a high constancy of the measurement temperature is required (0.02 K in accordance with ASTM D 445).

In the new development of the Viscosity Process Analyzer VISC-4 made by BARTEC BENKE, special attention was given to well-known problems of the viscosity measurement and to the requirements of the standards ASTM D 445 and ISO 3104. It was possible to dispense completely with an oil bath, which is quite maintenance-intensive and whose temperature is often not constant enough, and with pumps.

The VISC-4 continuously determines the kinematic viscosity. Due to the simultaneous measurement of mass flow and density of the liquid, the kinematic viscosity can be used to calculate and display also the dynamic viscosity. Due to an appropriate construction, the necessity of correcting the measurement value in accordance with Hagenbach is eliminated. Several variants are available for various measurement and temperature ranges: Kinematic viscosities ranging from 0.7 to 500 cSt can be measured at temperatures ranging from 20 to 100°C.

Interfaces for the data transfer and the control through superordinate systems as well as for the remote maintenance of the VISC-4 are available. Special functions such as an automatic purging and venting procedure offer solutions for difficult applications. The extremely complex sample preparation systems for viscosity measurements are configured in an application-specific way. With its continuous display of the kinematic viscosity, its high temperature precision and its minimized maintenance expenditure, the VISC-4 certified for zone 1 (ATEX) proves its high process capability.