Risk Based Inspection

Probability of Failure (POF) addresses the likelihood that equipment will fail within a defined period or operating scenario. The assessment begins by identifying active and potential damage mechanisms. Depending on the equipment and process environment, these may include general or localized corrosion, erosion, cracking, fatigue, high-temperature degradation, or other forms of deterioration.

Where applicable, methodologies consistent with the American Petroleum Institute Recommended Practice (API RP) 581 can be used to support quantitative or semi-quantitative POF assessments. A robust evaluation should also recognize uncertainty in data, degradation rates, inspection effectiveness, and relevant management-system factors rather than presenting uncertain inputs as precise predictions.

Consequence of Failure (COF) considers what could happen if an asset fails. Potential consequences may include injuries and other safety risks, environmental releases, equipment damage, loss of containment, production interruption, and broader operational impacts. Financial consequences may incorporate lost production, repair costs, cleanup costs, replacement expenses, and other credible business losses. COF results can then be classified into defined categories so that consequences can be compared consistently across the facility.

RBI combines POF and COF to establish an overall risk ranking. In simplified form: Risk = POF × COF. Assets can then be assigned to risk bands or categories using an established risk matrix or other approved methodology. Higher-risk assets generally receive greater inspection priority, while lower-risk assets may qualify for optimized or extended inspection intervals where technically justified and permitted by applicable requirements. This prioritization enables operators to map inspection resources, budgets, personnel, and shutdown opportunities directly to identified integrity risks.

RBI should not operate independently from the wider asset integrity program. Its findings can inform corrosion control plans and identify where additional mitigation measures are appropriate. Depending on the identified degradation mechanism, recommendations may include changes to cathodic protection systems, corrosion inhibitor programs, process controls, coatings, linings, monitoring programs, or materials of construction. Where repeated degradation is detected, material upgrades or other engineering modifications may provide a more sustainable solution than relying solely on increasingly frequent inspection.

Once the inspection plan has been approved, NDT activities should be performed using the selected techniques and applicable procedures. Consistent data capture is critical. Standardized field reporting templates help ensure that inspection teams document locations, methods, observations, measurements, anomalies, and equipment condition in a format suitable for subsequent analysis. Inspection results should then be uploaded to a centralized repository or integrity management system where they can be reviewed, trended, and incorporated into future RBI assessments.