Importance of Backflow Prevention of Hazardous Chemicals from Process Vessels to Utility Pipelines

Design of a chemical manufacturing facility is a challenging task because one must ensure that every design feature is carefully analyzed for Hazard and Operability (HAZOP). Along with the HAZOP studies of the main process vessels it is imperative to study the possible failures of the utility connections. A system is as safe as its weakest point of failure. A common failure is the back flow of hazardous chemicals into the utility connections. Utilities like nitrogen, steam, plant air, and deionized water are often directly connected to process vessels. The utility systems are generally common to the entire plant and so depending on the reaction conditions in an equipment, backflow may occur and contaminate other equipment. Different backflow prevention instrumentation is required based on the utility service. While designing PSVs for utility supply to process vessels one need to consider backflow scenario as one of the design criteria. This talk will outline various backflow prevention setups that have been successfully implemented in different chemical manufacturing facilities. Based on the severity of failure, the back-flow prevention appropriate for different utility services will be discussed.