Localised fires are an important accidental scenario for the offshore industry due to the extent of their potential damage. Its consequences may be localised damage, weakening of structural elements, blast when a storage tank reaches its critical temperature, or the structure's progressive collapse. The correct sizing of the fire protection (passive and/or active) system allows reducing or delaying the potential structure's damage. This article evaluates the use of the LF-ESF methodology at the design stage to estimate the efficiency of the passive fire protection layer (PFP) in upper offshore structures exposed to localised fires. Fire conditions are assumed to result from a typical process involving the combustion of hydrocarbons. Three fire scenarios are evaluated using the LF-ESF model proposed by the authors and based on updates of simple methodologies widely used in the literature. In order to verify its accuracy, its results are compared with a model developed in a CFD-based package for a fire scenario. Thermo-mechanical analysis is performed employing a finite element model that considers the temperature-dependent physical and geometric non-linearities. The estimated thermal load is entered into the thermo-mechanical model in combination with the pre-existing operational loads to evaluate the structure's behaviour. Despite the slight overestimation of the thermal field from the LF-ESF model, compared to the CFD-FEM methodology, the results obtained allow the selection of the PFP without being too conservative and at low computational cost.