Dec-2022

What RBI is and what it isn’t

Risk-based Inspection (RBI) has been around the refining and petrochemical industry for many years.

Matt Caserta
Becht

Article Summary

When the original task group was put together to investigate RBI in the early 1990s, lessons learned from other industries that had been practicing this approach even earlier were incorporated into the two standards that API developed, API RP 580 — Risk-based Inspection and API RP 581 — Risk-based Inspection Methodology. API RP 580 provides the requirements, systems, and practices required to have an RBI program for owner-operators. API RP 581 provides a specific, consensus-approved methodology for performing RBI analysis. It should be noted that API 580 allows for the use of any methodology as long as the minimum requirements are met. API 581 is just one example of a specific approach to determining risk related to fixed equipment.

So what is RBI?
Risk-based Inspection is a risk management system used to determine inspection, mitigation, and acceptance of risks associated with pressure equipment. The primary point of RBI is to help owner-operators make more informed decisions about what types of inspections to perform on pressure equipment and when to complete those inspections. The main basis of RBI in the refining and petrochemical industries it that risk is a function of a probability of a failure occurring (events per year) and the consequences associated with that failure (impact per event), expressed in the equation below:

Risk=p(t)*c(t)

RBI is a useful tool to help focus inspection programs on areas of the highest risk. Areas that have large risks associated with losses of containment or financial impact to the facility can be prioritised to identify potential issues prior to a major event occurring. RBI programs also identify the expected damage mechanisms which allow for targeted inspections to determine the current state of a pressure equipment item. RBI also allows an inspection to focus on specific techniques for the expected damage that can be done intrusively or non-intrusively.

What RBI isn’t
Ï…    A cost saving program — in the past RBI has been touted as a way to reduce costs of inspection programs. While there are some long-term benefits related to cost, normally when starting a program, inspections costs will rise initially as high-risk items are identified that may have been unknown or neglected in the past. Investments must be made develop and maintain the program and supporting resources. Some of the focused inspections mentioned above may be more costly than traditional inspection techniques.

Ï–    A stop-gap for missing data — In order to understand risks associated with pressure equipment a number of different data types are needed: asset lists, operating conditions, process constituents, and previous inspection information, just to name a few. Data quality is very important to a well-functioning RBI program. As the old saying goes “garbage in, garbage out.”

ω    A solution for poor programs — some within industry see RBI as a solution to a poor mechanical integrity (MI) programs. RBI doesn’t substitute for lacking foundational elements of mechanical integrity. For an RBI program to be successful, it must build on existing MI programs such as damage mechanism identification, piping circuitisation, condition monitoring location assignment, and quality control.

ξ    A one-time effort — as noted above, RBI is a system used to manage risk associated with fixed equipment. This means that “doing RBI” isn’t a single initiative. Instead, it is adopting a new approach to managing inspection planning. RBI allowances in inspection codes like API Std. 510 and API Std. 570 require revalidation of an RBI analysis on a time-based interval (like 10 years) or when major changes occur to the unit. Either way, keeping the program updated is key to a high functioning management system.

In the end, RBI should be seen as another “tool in the toolbelt” for the inspector. RBI can be a very powerful tool when properly leveraged but should not substitute for other critically important mechanical integrity efforts. If you are optimising an existing RBI program or embarking on a new risk-based effort our industry renowned experts can help develop a program that works for your site and can be maintained in the future.