API RBI and MOEs
RBI studies are based on past and future operating conditions, focusing more heavily on inspection activities rather than on controlling operations and monitoring activities. However, knowledge and control of a unit’s operating envelope helps a RBI plan to succeed. A Materials Operating Envelope (MOE) program, although it can be a stand-alone effort, complements RBI and makes the RBI plan more proactive. Together, these two technologies provide an improved chance for reliability and safety
Refineries typically conduct Management of Change (MOC) reviews when process changes are made intentionally. Often changes are made inadvertently. In many cases, the people involved either do not have the tools or experience to evaluate the effects of minor process creep, or knowledge of the boundaries for materials degradation. Ideally, boundaries are established to permit the process to safely operate within set limits without major concerns for the health of the equipment.
A MOE defines the limits for each part of a unit for operating parameters, such as feed contaminant content, pH, flow rate, temperatures, chemical or water injection rates, and acceptable levels of corrosive constituents.
- If limits are not exceeded, degradation should be predictable and reasonably low.
- If limits are exceeded, excessive equipment degradation due to corrosion, stress corrosion cracking, metallurgical embrittlement, or hydrogen effects, such as high temperature hydrogen attack, could occur.
MOEs can be created prior to or after RBI is implemented, as many of the data requirements are similar.
