ABSTRACT
It must also be emphasised that incorrect use of any instrument will give erroneous results. Summarising the practical aspects of using tube and rotational viscometers:
1. Rotational viscometers • small sample needed (2 litres maximum), • easy to operate, • may be purchased complete, • shear rate range up to approximately 300 s-1 • may be used to characterise thixotropy, • may be used to characterise wall slip, • different bobs and cups give wide viscosity range, • different length bobs used to estimate end effects, • scale up calculations can be complex and lengthy,
2. Tube viscometers • larger sample needed (5 litres to 500 litres depending on type), • may be difficult to operate, • generally constructed in-house, • shear rate range up 5 x 10 4 s-1, • difficult to characterise thixotropy, • may be used to characterise wall slip, • different tube diameters give wide viscosity range, • different length tubes used to estimate end effects, • scale up calculations from tube to tube may be relatively simple.
