Risk Based Inspection

RBI, Risk Based Inspection, is a method of evaluating failure modes and their effects for stationary equipment, in order to create the most optimal inspection regime to reduce risk to safety, environment, production as well as other factors that the organization cares about.

It examines the Health, Safety and Environment (HSE) and business risk of ‘active’ and ‘potential’ Damage Mechanisms (DMs) to assess and rank failure probability and consequence. This ranking is used to optimize inspection intervals based on site-acceptable risk levels and operating limits, while mitigating risks as appropriate. RBI analysis can be qualitative, quantitative or semi-quantitative in nature.

Probability of Failure (PoF) is estimated on the basis of the types of degradation mechanisms operating in the component. It is calculated as the area of overlap between the distributions of the degradation rate for each degradation mechanism (based on uncertainties in rate) with the distribution of the resistance of the component to failure.

Consequence of Failure (CoF) is defined for all consequences that are of importance , such as safety, economy and environment. Consequence of failure is evaluated as the outcome of a failure based on the assumption that such a failure will occur.

Accuracy is a function of analysis methodology, data quality and consistency of execution.

Precision is a function of the selected metrics and computational methods. Risk presented as a single numeric value (as in a quantitative analysis) does not guarantee greater accuracy compared to a risk matrix (as in a qualitative analysis), because of uncertainty that is inherent with probabilities and consequences.

RBI is most often used in engineering industries and is predominant in the oil and gas industry. Assessed risk levels are used to develop a prioritized inspection plan. It is related to (or sometimes a part of) Risk Based Asset Management (RBAM), Risk Based Integrity Management (RBIM) and Risk Based Management (RBM).

Generally, RBI is part of Risk and Reliability Management (RRM). The basis of most RBI programs is the Corrosion Circuit, in which each circuit can be compared for relative risk levels to aid in inspection and maintenance planning.

Inspections typically employ non-destructive testing (NDT).