Details behind the experimental technique of ultrasonic velocity profiling (UVP) to obtain in situ velocity measurements of both aqueous and organic phases in commercial solvent extraction SX settlers are presented. The commercial applicability and benefit of the process is demonstrated via the on-site analysis of two settlers at a commercial copper solvent extraction operation. The two settlers had the same dimensions and were operated under essentially equivalent conditions but differed in terms of being assessed before and after routine maintenance, with the internal 'furniture' configuration of the latter also being modified. UVP-determined organic and aqueous flow pattern results from the two settlers are reported and compared in relation to the furniture configuration/maintenance status of each. The results highlight the potential for UVP analysis to ascertain flow patterns in commercial solvent extraction settlers to benefit industrial operations directly and to enable the development of improved mathematical (computational fluid dynamics) modelling of flow patterns in settlers. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.