Reliability Based Facility Risk Assessment

Pipeline facilities are ageing and will likely soon come under closer scrutiny from federal regulation. It is imperative that sound reliability based inspection procedures be established that meet the goals of an organization while controlling time and cost. DNV Columbus has developed a statistically based sequential inspection decision support system for this purpose. This system was implemented for an international petroleum company and quickened the inspection process by making a “stop inspections” or a “continue inspections” decision after each inspection at a facility. This system allows inspections to be stopped because the desired reliability metrics have been met. This means that the point of diminishing returns has been met based on inspections that did not reveal a significant amount of corrosion. At this point, further sampling would provide minimal additional value to the reliability assessment. Inspections can also be stopped because the estimated reliability metrics have not been met. Stopping for this reason indicates the facility may need more significant repair or replacement. Engineers and managers can then make a decision that includes a variety of factors including safety and the economic feasibility of alternates. In contrast, when using this method, inspections continue because insufficient data have been collected to determine whether the reliability metrics have been met. This system will be illustrated with actual data. It will also describe the use of four key safety factors in developing site specific reliability goals. These factors are consequence, off site migration probability, product type, and facility size. This work can result in a major savings in time and financial expenditures for an inspection cycle. This reliability based inspection methodology leads to the following improvements: 1) Quicker decisions to save time and money, and allows more sites to be inspected in a timelier manner, 2) The reliability of a group of inspections performed is quantified after each inspection, 3) Results at a facility are broken down by database driven categories into a scorecard, 4) Methodology kept generic to be easily adapted to a wide variety of situations.