Emergency Depressurization System Evaluation Case Study


The Challenge

A major oil refinery needed to ensure the adequacy of several Emergency Depressuring Systems (EDS) within their operating process units. The client requested that ioMosaic evaluate the dynamics of all interlinked equipment.

  • by 75 psi or 5% of full pressure during the first minute after actuation, or
  • as required to depressurize to less than 50 psig in 60 minutes, or
  • to 50% of the normal operating pressure in 15 minutes or less.

Our Approach

ioMosaic modeled the flow dynamics for the entire depressuring system using Process Safety Office®. Our tools are capable of modeling the depressuring dynamics of one or more interlinked single and/or multi-phase vessels.

This case study focuses on the reformer reaction system. It started with four reactors connecting to a series of five exchangers and ended at a gas separator. This was a challenging analysis because the depressuring system contains interconnected vessels that involve two-phase systems. A single volume representation solution of the system (what is typically assumed) is not recommended and cannot represent the correct initial system dynamics. In addition, the flow resistance of the lines interconnecting the equipment must be considered. This was addressed by SuperChems™ using detailed flow models for both single and multiphase systems.

An important aspect of depressuring dynamics is consideration of the potential condensation of heavies in downstream vessels as the pressure and temperature decrease during blowdown. For some systems, this can give rise to two-phase flow and/or cold cryogenic temperatures.

The Benefits

Oil refineries are required to provide adequate documentation regarding the conditions that necessitated the installation of depressuring systems, the required rate of depressuring, and the adequacy of the blowdown systems. ioMosaic modeled the depressurizing dynamics of a complex system and demonstrated to the client that the system was adequate and delivered a full report of the results.

Learn More

Our mission is to help you protect your people, your plant, your stakeholder value and our planet. To learn more about how we can help you manage risk, call us at 1.844.ioMosaic.