10 STEPS TO CHOOSING A RBI INSPECTION PROGRAM
There are several ways to approach developing a Risk-Based Inspection program for your facility. How do you determine which approach is right for you?
Qualitative versus Quantitative RBI
The quality of available information on a facility’s assets usually determines whether a qualitative or quantitative RBI approach should be used. RBI methodology can be used on older facilities that have little or poor data available; on newer assets that have technical data available, but little inspection history; and on facilities with good quality data and inspection history. The approach adopted will depend on:
- Available design and construction data
- Equipment condition based on inspection history
- Knowledge of past, current and future process operational conditions
- Complexity and age of systems involved
A qualitative RBI approach uses data analysis and local expert knowledge and judgment to prioritize inspection, and requires much less data to implement. Qualitative RBI should provide a more conservative analysis that requires shorter inspection frequencies because it relies on less data and a simplified assessment methodology. A qualitative RBI program is still fully compliant with API 580, the recommended practice for implementing RBI for oil and gas facilities, and can serve as a tool to prepare the owner/user for a more in-depth quantitative analysis after more data is available.
Quantitative RBI analysis is based on probabilistic and/or statistical models that calculate risk over time as in-service damage increases. Quantitative RBI can require large amounts of up-to-date and accurate data which is often not available. Less data generally requires a more qualitative approach, at least initially.
10 Criteria for Selecting the Appropriate RBI Level for Your Facility
Developing a Risk-Based Inspection program depends on a situation analysis of your operations, data and resources, among other factors. The following criteria can help you determine what level of RBI is appropriate for your facility:
- Maturity of the mechanical integrity and process safety management programs – RBI requires data for equipment design (U-1 or piping specification data), process operating conditions (temperature, pressure, material balance including hydrocarbon, non-hydrocarbon, toxic compositions as well as liquid/gas phase information) and inspection history (inspection locations, methods, coverage and inspection results such as measured thickness at a specific date.
- Implementation of mechanical integrity program and process safety management program initiatives – As mentioned above, a mature mechanical integrity program may support a more quantitative approach to RBI. Conversely, in the early stages of mechanical integrity implementation, an emphasis on collected design, process and inspection data may make a quantitative RBI approach unrealistic. But using qualitative RBI at this stage could result in a cost effective method to risk rank and prioritize systems for implementation of the mechanical integrity program. As more data becomes available, a more quantitative assessment can be added to the RBI program, depending on the other factors considered in this section.
- Maturity of inspection program – A very mature program with all potentially active damage mechanisms properly identified can use RBI to optimize inspection and manage/reduce risk. A program focused on optimizing risk generally results in increasing inspection for higher risk equipment and reducing inspection for lower risk equipment. The savings related to reduced inspection most often can be applied to the increased inspection areas with little negative impact on the overall cost. In the situation where little inspection has been performed, RBI can identify a much higher level of inspection required than for a more mature program. This example highlights a situation where more inspection may be recommended when a damage mechanism (wet H2S damage potential in sour service) had not been previously identified. A quantitative approach is not required to properly identify equipment in this case.
- Corrosiveness of service – Process conditions driving POF due to in-service damage needs to be considered. The key aspect of the POF is a credible corrosion/damage review performed by a knowledgeable specialist to identify potential damage mechanisms for operation that include internal corrosion (thinning due to general or localized corrosion); external corrosion or cracking (atmospheric conditions and CUI potential as well possible cracking if austenitic materials are used); internal stress corrosion cracking (for sour applications with H2S or H2S/CO2, amine treating); and other damage mechanisms (brittle fracture considerations for processing noncondensing hydrocarbons or cold service equipment). In non-corrosive services, RBI can justify doing little inspection to maintain acceptable risk levels.
- Process Operation – Process conditions driving COF due to flammable and toxic consequences, as well as business interruption, also needs to be considered. The key aspect of the COF is relative consequence ranking of equipment COF does not change over time unless the process conditions change considerably. In upstream and pipeline applications, the change in process stream composition over time, and therefore COF and risk over time, is possibly as important as the COF ranking between assets at any point in time.
- Complexity of the process – Reminding us that it’s all about risk prioritization for inspection planning, and that absolute quantitative values are not required or even desired, owner/users are looking for the best approach to properly and effectively risk rank equipment and provide the proper relative rankings. The less time and money spent on the risk analysis in order to get the desired result, the more that can be spent developing and improving the inspection program.
- Personnel – Qualitative programs, because of their relative simplified methodology, often require less training for internal resources to implement and maintain the risk program. Less rigorous RBI methodologies should not be confused with the use of less experienced resources. In fact, qualitative methodologies require more experienced specialists to assign process conditions and in-service damage potential most often through expert opinion. Quantitative methodologies depend on actual operating data and inspection history to calculate risk. However, more rigorous methodology requires more experienced and trained resources in order to properly implement and maintain the RBI program.
- Systems and training – Implementing and maintain any RBI program over time requires systems and ongoing training of personnel. Once implemented, training needs are minimal as long as the resources are properly training initially. Since quantitative programs are more rigorous, changes are often made to the methodology over time and specialized skills are often required to operate software programs to manage risk. As a result, refresher training is needed for key RBI personnel required to maintain and update the program.
- Range and number of systems and assets – What and how much equipment is being included in the RBI program? Usually piping, pressure vessels, heat exchangers, filters, and externally fired heaters are included.
- Cost of implementing and maintaining the RBI program versus value of program – If the inspection program is very mature, there may be less dollar value in investing a lot of time and money to optimize it. Conversely, if the inspection program is very immature (little high quality inspection has been done with consideration for in-service damage), implementation of an integrity program initially may require more extensive inspection regardless of risk. Short term benefit may not justify a big investment.
Developing Your RBI Inspection Program
In most facilities, a large percent of the total risk is concentrated in a relatively small percent of the equipment, and these potential high-risk areas may require greater attention through a revised inspection plan. A qualitative program can help identify these areas of higher risk and potentially destabilizing conditions for which a more focused quantitative approach is necessary.
Thus, qualitative and quantitative approaches can be used in a complementary way to develop an efficient and reliable inspection program that continues over the life of the equipment. A qualitative program can be the first step toward a semi-quantitative or quantitative program as more detailed technical data becomes available.
Call Lynne Kaley at 713-458-0098 to discuss the best option for your facility