The methodology for applying Risk based inspection (RBI) to the process industry have been developed by DNV in Houston, for a sponsor group under the American Petroleum Institute Committee on Refinery Equipment, and is laid down in the Base Resource Document API 579. Risk based inspection is a method for using risk as a basis for prioritising and managing the efforts of an inspection programme. In an operating plant, a relatively large percentage of the risk is associated with a small percentage of the equipment items. RBI permits the shift of inspection and maintenance resources to provide a higher level of coverage on the high risk items and appropriate effort on lower risk equipment, resulting in an improvement of plant availability and reliability. The RBI method defines the risk of pressure-containing equipment as the combination of the likelihood of failure and the consequences of that failure. This combination produces an estimated risk for each equipment item. Risk can be expressed in terms of personal safety, damaged to equipment, environmental impact and business interruptions. The influence of inspection on risk is quantified and risk reduction can be evaluated based on inspection options. A further benefit of an RBI programme is to increase operating periods and run lengths of process facilities while managing the level of risk. This approach permits an estimate of change in operating equipment or piping as a result of time dependent deterioration. RBI can become a tool that will allow plant owners to extend shutdown intervals. Based on the Base Resource Document software prioritisation programmes have been developed as a tool that analyses the position of the plant equipment and piping within a five-by-five matrix, which rates it as high, medium high, medium and low risks. Optimisation of plant inspection effectiveness and extensive report generation is part of the software programme. Also recent projects in the Netherlands have demonstrated the value of this approach. Close co-operation between client and DNV will stand surely for an effective implementation of the Risk Based Inspection programme, which, in turn, will help with plant reliability and profitability.
Publication Source: First International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components , 20 - 22 October 1998, Amsterdam, Netherlands. Held by the Joint Research Centre of the European Commission. Publisher:Woodhead Publishing Limited
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