Viscometer, Brookfield concentric-cylinder

Figure 2.4 A commercial instrument, the Brookfield Digital Viscometer, based on the geometry of the concentric cylinder viscometer. (Photo courtesy of Brookfield Engineering Laboratories, Inc., Stoughton, Mass. 02072.)...

With several springs, which function as torque gauges, and a number of spindles, viscosities can be measured up to 10 mPa-s with the Brookfield viscometer. The shear rates depend on the model and the sensor system they are ca 0.1 100 for the disk spindles, <132 for concentric cylinders, and <1500 for the cone—plate forlow viscosity samples. Viscosities at very low (ca 10 — 1 )) shear rates can be measured with the concentric... 

Historically, viscosity measurements have been the single most important method to characterize fluids in petroleum-producing applications. Whereas the ability to measure a fluid s resistance to flow has been available in the laboratory for a long time, a need to measure the fluid properties at the well site has prompted the development of more portable and less sophisticated viscosity-measuring devices [1395]. These instruments must be durable and simple enough to be used by persons with a wide range of technical skills. As a result, the Marsh funnel and the Fann concentric cylinder, both variable-speed viscometers, have found wide use. In some instances, the Brookfield viscometer has also been used. 

The concentric-cylinder viscometer is schematically shown on Fig. 10.3. There are two ways that the rotation can be applied and the torque measured the first is to drive one member and measure the torque on the same member, while the other is to drive one member and measure the torque on the other. Examples of the first kind are the Haake and Brookfield instruments examples of the second kind would be the Weissenberg and Rheometrics rheogoniometers. 

The flow-property or rheological constants of non-Newtonian fluids can be measured using pipe flow as discussed in Section 3.5E. Another, more important method for measuring flow properties is by use of a rotating concentric-cylinder viscometer. This was first described by Couette in 1890. In this device a concentric rotating cylinder (spindle) spins at a constant rotational speed inside another cylinder. Generally, there is a very small gap between the walls. This annulus is filled with the fluid. The torque needed to maintain this constant rotation rate of the inner spindle is measured by a torsion wire from which the spindle is suspended. A typical commercial instrument of this type is the Brookfield viscometer. Some types rotate the outer cylinder. 

The Brookfield TTIOO is a typical on-line instrument that fulfils the criteria set out above, in that it follows the 3Rs, i.e., representative sampling, relatabihty, reliability and robustness of operation. It is manufactured by the Brookfield Engineering Company of the USA, who are the longest-standing manufacturers of commercial rotational viscometers in the world. It is a concentric-cylinder instrument that can operate in- or on-line, and has an open-ended variant that can be mounted into the wall of a vessel - the TT200. 

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