Barrier verification during maintenance using a management of change (MOC) process: A process safety case study

Maintenance and equipment replacement activities in pressurized process systems are often associated with an increased risk of leaks, particularly during implementation phase transitions such as isolation, line-breaking, and return-to-service. Nevertheless, published process safety literature is still dominated by design stage analysis and post-incident investigations, with limited attention given to barrier verification during routine industrial changes. This study presents a document-based process safety case study examining the replacement of a glycol circulation pump in a gas dehydration system, managed under a Management of Change (MOC) framework. The scope of the change is defined using the minimum nameplate level specifications, and the hazards of the implementation phase are identified through activity-based analysis. Safety barriers are mapped to credible and verified leakage scenarios at auditable containment points before mechanical disassembly and before reactivation. The results show how energy isolation verification, pressure relief, mechanical readiness, and recovery conditions can be treated as separate safety functions during maintenance-related changes. Although operational performance after the change is outside the available evidence base, this study demonstrates that verified barrier integrity provides a defensible basis for loss prevention during transient operational conditions. The presented barrier verification logic can be applied to other rotating equipment interventions in pressurized systems and provides practical learning for process safety management during maintenance and modification activities.