The key design parameter for most solid-liquid operations in a stirred tank is the just suspended speed, N-js. In majority of the literature N-js is determined by visual observation of the tank bottom. This method is observer dependent, and the results may vary up to 38% between two observers. A more recent method, pressure gauge measurement (PGM) method, is promising as it is based on pressure measurements at the bottom of the tank, and therefore is observer independent. This method also does not require a transparent vessel which eases its use in industrial applications. The PGM method was developed for slurries of low to moderate solids concentrations with N-js values corresponding to relatively low impeller speeds. In this study the applicability of PGM method was tested at conditions beyond the limits that it was developed. The slurries that were tested were in general closer to slurries that are used in industrial applications - high solids concentrations, more than one solid phase, high-density solids, but also slurries with low settling velocity solids were tested. It was found that the application of PGM method required some caution when these slurries were used. The problems encountered with collection and analysis of data at these out-of-limit applications and the solutions to overcome these problems are reported. In this study, for the first time in literature, the visual observation method and the PGM method were compared using a large data set. The two measurements varied up to 12.8%, which shows that the PGM method can confidently be used for finding N-js of industrial slurries. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.