Refinery Relief Device and Flare Header Revalidation and Documentation Updates

Project Synopsis

Project Summary

PETROLEUM REFINERY RELIEF DEVICE AND FLARE HEADER REVALIDATION AND DOCUMENTATION UPDATE

The client, an independent petroleum refinery with a capacity in excess of 50,000 BPD, contracted Process Engineering Associates, LLC (PROCESS) to execute a relief valve and flare system capacity update project.  It is noted that this project was required to update information that PROCESS had previously generated for the client during earlier projects.  This project included the following major tasks:

• Update the previously completed relief device documentation files with the most current information for the relief devices including all relevant changes from revamps and new or out-of-service equipment.
• Update the refinery wide flare header simulation done three years prior to include all recent refinery modifications and current Pressure Safety Valve (PSV) information from recent revamps.  The updated simulation considered the current refinery throughput as well as an escalated operational mode.  PROCESS identified issues associated with the flare header hydraulics and made recommendations to resolve these issues.
• Develop calculations to determine the maximum backpressure during relief scenarios to help ensure that relieving pressures at the actual process equipment would not exceed the allowable overpressure.

At the initiation of this task, the PROCESS project team gathered the requisite process and engineering information from the client. Using the process information from the client as well as engineering information relative to the existing relief valves, PROCESS utilized its licensed commercial computer process simulation software as well as its in-house relief device evaluation program to evaluate the vapor and liquid relief capacities of each valve as well as relief requirements for all identified credible relief scenarios.  Relief capacities for pressure safety devices (PSDs) were evaluated using current API Standards.

Although the project covered the entire refinery, most relief devices were located in the following units:

• Alkylation Unit (Alky)
• Mild Hydrocracking Unit (MHC)
• Fluid Catalytic Cracker Unit (FCC)
• Crude Distillation Unit (CDU).

PROCESS also constructed and/or modified detailed computer process simulations of the relief system hydraulics using its licensed commercial computer process simulation software’s hydraulics package.  The identified relief scenarios were then modeled for the purpose of determining the presence of excessive back-pressures (i.e., inadequate capacities).  For sections of the relief system identified as bottlenecks, PROCESS developed recommendations to eliminate the bottlenecks, including pressure vessel pressure re-rating, process or operational changes to reduce the required relief loadings, and potential modifications to existing relief valves (e.g., decreasing set pressures, increasing orifice sizes, or replacing conventional relief valves with balanced-bellows relief valves).

Industry Type

• Petroleum Refining

Utilized Skills

• Refinery wide relief systems revalidation