Here we synthesize a two-step Fr 13 risk assessment (Davey et al., 2015; Davey, 2015) for the first time. We demonstrate it with vulnerability to fouling in an apparent steady-state global process of integrated cross-flow ultrafiltration and osmotic distillation (UF-OD) for concentration of fruit juice. Integrated two-step membrane processing of juices is becoming widespread as an alternative to thermal treatment. The aim was to advance the Fr 13 framework to investigate how naturally occurring, random fluctuations in apparent steady-state plant parameters can be transmitted and impact in progressively multi-step complex (i.e. integrated not 'complicated') processes. Membrane behavior is simulated using Monte Carlo (with Latin Hypercube) sampling of transmembrane pressure (Delta PUF1-1) and filtration time (t(UF1-1)) with independent data for concentrating pomegranate juice (Punica granatum). Membranes fouling is defined as a permeate flux less than the operational design flux. Overall global failure of the integrated two-step OF-OD is defined as an unwanted OD flux (J(OD) 1-2 < J(OD) 1-2, required plus 3% tolerance). Results show the Fr 13 method is applicable to an integrated two-step process. The integrated OF-OD is expected to be vulnerable to surprise fouling in 10.5% of all operations, over an extended time. Findings are used to assess re-design for reduced membrane vulnerability to fouling in second-tier studies. Results appear generalizable and could be applied to a range of integrated two-step processing. Outcomes will be of interest to risk analysts and manufacturers of membrane equipment. This work is part of an overall development and investigation of Fr 13 as a new quantitative risk assessment and equipment design tool. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.