RBI Reassessment

Sustaining your API RBI program

Sustainability is one of the most important parts of a RBI program. Since RBI is a dynamic approach based on data and technology that both change over time, inspection plans need to be updated based on new inspection findings, as well as to reflect enhancements to API RBI technology. Optimally, RBI should be combined with Fitness-for-Service and Materials/Corrosion disciplines to manage mechanical integrity throughout the useful life of equipment.

API 510 and 570 Codes require re-evaluation of an RBI study at a maximum frequency of 10 years. To maximize an inspection plan, updating a RBI reassessment should be done to ensure that the most recent inspection findings and any changes in process, hardware, and active damage mechanisms are included and analyzed.

Updating new inspection data

Data updating of a current inspection history is usually performed in conjunction with turnaround work, during the Management of Change (MOC) process, to comply with OSHA 1910 HAZOPs, PHAs or audits, or after an unexpected failure. Updating new inspection data includes the following:

• Inspection History – date of inspection, measured wall thickness (internal/external thinning) and inspection effectiveness categories by mechanisms
• Measured corrosion rate representative for the circuit/corrosion group; modifications in cracking susceptibilities, as appropriate
• Any significant findings from inspection

After the addition of new or revised data, the risk associated with the equipment is reevaluated.

Reassessment

Although API 510 and 570 Codes require re-evaluation of a RBI study at a maximum frequency of 10 years, Equity recommends re-evaluation at unit turnaround frequencies for maximum safety and program benefit. Re-evaluation can be triggered by the results of inspections, changes in process operating conditions, operating outside of identified key process variable ranges or vessel material changes. Any of these issues can have a significant effect on the damage assessment and probability of failure, and prompt the need for a reassessment.

The work process for RBI Reassessment includes:

• Review of operating data for identification of changes since the previous study
• Evaluation of whether changes impact assigned damage mechanisms
• Review effectiveness categories of inspection performed as well as inspection results since the previous RBI study
• Development of an updated Inspection Plan

Other specific analyses that should be considered at this time include a Management of Change (MOC) study to identify changes affecting equipment and other mechanical integrity issues; and a Materials Operating Envelope (MOE), a study that identifies key process operating variables that may affect damage. MOEs are described in more detail in the following section.