For those who work in the oil, gas or other process industries, regulations that ensure safe operation are clear. When operators are working with hazardous materials or work in potentially hazardous conditions, there are extra precautions to take and processes to follow.

But when operators are in charge of their company’s comprehensive asset integrity management program, they need to take into account the amount of service life equipment and components have left. They must manage such a program so that it ensures safe and efficient operation while also maximizing equipment service life. Their evaluation has to be as accurate as possible when determining how much service life is left so they are not replacing or repairing anything unnecessarily or schedule an action when is too late .

Previously, the method to determine remaining service life was condition-based inspection. Nondestructive testing methods could be used to identify flaws. Based on material or manufacturing specifications, operators would then determine whether the component or system could continue operating.

“Process industries are now moving toward risk-based inspections to maximize equipment service life.”

The difficulty operators often faced was whether to repair or replace. Trying to fix a small crack in a weld might actually do more harm than good. Replacing a component altogether might be unnecessary.

Process industries are now moving away from condition-based inspections toward risk-based inspections in an effort to maximize component service life.

How does it work
Risk-based inspections are quantitative assessments based on probability of failure and consequences of failure, according to Inspectioneering, a journal dedicated to asset integrity management for oil, gas and other process industries.

NDT is still an integral part of this type of inspection method and the results provide the data to engineers that need to make their decisions. However, RBI uses mathematical models to assess risk of failure and the consequences. As part of a RBI protocol, operators will often rank pieces of equipment by the risk of failure they pose and then implement an inspection schedule to monitor any further degradation. The higher the risk a component or system poses for failure, the more frequently inspectors have to examine those components.

A RBI protocol might also include taking steps to lessen the risk of failure. As Inspectioneering noted, engineers might change operation procedures to prolong service life. Perhaps they change the material used to construct components or systems to one that lasts longer or withstands operating conditions better. Even installing corrosion resistant liners to piping systems can prolong life.

“The API standards provide a blueprint for operators so they don’t have to figure out a RBI program for themselves.

Codes and standards
Making the case for risk-based inspectionsEngineers aren’t left to devise their own RBI protocol. The American Petroleum Institute has developed two standards for operators to follow. The API RP 580 standard details the minimum requirements for implementing a RBI program. API RP 581 provides the technical basis for such a program.

As John Reynolds wrote for Inspectioneering, the standards provide a blueprint for operators so they don’t have to figure out a RBI program for themselves.

“API RP 580 is intended to provide guidance on implementing a RBI program for fixed equipment and piping. It includes: all of the key elements of RBI, how to implement a RBI program, how to sustain a RBI program, initial planning for RBI, RBI data gathering, identification of damage mechanisms, how to assess probability of failure (POF) and consequence of failure (COF), risk calculations, managing inspection activities with RBI, RBI reassessments, and documenting the results.”

TWI Global, an independent research organization, wrote that an API RP 581 standard is applicable for oil and gas assets. The DNV-RP F116 standard – from international certification body Det Norske Veritas – is meant for underwater pipelines. RBIs are also valuable for petroleum storage tanks and power generation equipment, such as steam and gas turbines.

Many of the industries that use RBI are heavily regulated. They must meet specific criteria for safety, for the plant staff and for the general public. RBI programs must be developed with regulatory mandates in mind. However, what RBI does is to allow engineers to make decisions with more information at their disposal. They no longer are compelled to repair or replace at the first sign of a flaw.

It is becoming more challenging for operators to manage asset integrity. They must meet operational objectives and get the most out their equipment all while maintaining safety and meeting environmental standards.

Risk-based inspection methods establish more effective plant maintenance and asset integrity management programs.