Process safety evaluation applying DIERS methodology to existing plant operations

The DIERS methodology can be used to quickly assess the relief capacity envelope for a collection of existing process vessels accounting for both vapor and gassy systems. Easy-to-use vent sizing nomograms and PRESS sheets are proposed that can be completed by the process engineering, the process chemistry and the process safety departments. A vessel volume-vent size diameter relationship is also developed using the source term based on fire exposure to cover a reasonable range of credible upset scenarios. In this way the adequacy of existing relief systems can be quickly surveyed for potential trouble sources—“outliers”—warranting further evaluation and corrective action.