Relief Systems Audit Case Study


The Challenge

A large refinery in the U.S. desired to conduct a third-party audit of their emergency relief systems to ensure that the methodology and engineering analysis used in the design of their emergency relief systems was adequate, conformed to recognized and generally accepted good engineering practice (RAGAGEP), and was being performed consistently without significant systemic errors. The audit scope covered two units within the refinery, and considered both individual relief devices, and entire flare systems. Findings of the audit were presented to plant management as well as the local regulatory authority.

Our Approach

The audit was a very systematic, thorough review of the emergency relief systems of the two units selected within the scope of work. The ioMosaic team worked with SuperChems™, ioAuditor™, and Process Safety Enterprise® Emergency Relief System Design Workflow software to manage all process safety information, evaluate the relief systems, identify compliance gaps easily, track action items, and  prepare a detailed report. 

Compile List of Relief Devices

ioMosaic reviewed the unit P&IDs and PFDs and assembled a categorized list of all the pressure relief devices in the two selected units. The results of the ERS survey of the hydrocarbon devices and the associated effluent handling system were presented as a schematic to illustrate how the relief system is connected to headers and flares.

Review of Individual Devices

An assessment of the input data accuracy, integrity, and availability of individual devices was conducted. Information typically required for relief system design and evaluation was crosschecked against information used in the actual analysis, and was also compared to the piping and instrument diagrams (PIDs). Where data may potentially reside in multiple places, ioMosaic reviewed the update procedures to ensure data integrity. The design reports for individual relief devices were then compared to the documentation requirements included in the 5th Edition of API-STD- 521. A review of the relief system design was performed to determine that the calculations were performed correctly, and that the design conformed to corporate guidelines, required standards, and good engineering practices.

Review of Flare Header

ioMosaic also reviewed one of the flare headers. The flare header review focused on disposal system loads, flare header design calculations, credits taken to reduce/eliminate disposal system peak loads, instrumentation assumed not to work for each relieving scenario, back pressure limit for each source and basis for limit, and acceptance criteria for flare system capacity. To ensure a consistent approach throughout the audit, ioMosaic developed a checklist to ensure key items were addressed for each relief system.

Review Internal Technical Guidance Documents

ioMosaic reviewed the client’s internal technical design guidance documents, and compared them to external guidelines and industry standards. The review included the design methodology, engineering calculations, scenarios and device selection as specified in guidance documents and compared them to recognized and generally accepted good engineering practice (RAGAGEP). ioMosaic made an assessment of the client’s internal guidelines. Any instances where the client’s internal design guidelines differed significantly from industry standards was described as part of the audit findings.

Verify Overpressure Calculations

For the two units within the scope of work, ioMosaic selected a representative sample of emergency relief systems and reviewed overpressure protection calculations for selected systems including the protected equipment, associated relief devices, headers and flares.

The Benefits

A presentation of the results was delivered in person and a report summarizing the audit findings. The report contained an Executive Summary section directed at a technical audience that is not a subject matter expert in relief devices. The summary presented the findings of the audit by giving our assessment of the clients technical guidance documents in comparison to recognized and generally accepted good engineering practice, and our assessment of the quality of the reviewed relief system calculations. This summary included any findings on significant systemic deficiencies that were identified. A Detailed Report was also included for the relief system experts. This report gave details to back up our assessment of the client design methodology, listed findings from the review of individual relief devices and explained any significant systemic deficiencies identified. The detailed report also contained the list of all relief devices and the schematic drawings.

In conclusion, the client was very happy the quality and execution of the audit. The client was very impressed with ioMosaic’s expertise, and that we had identified design issues which had previously been overlooked. The client was confident that ioMosaic was the correct choice to conduct this audit.

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.