A further development of the extended risk based inspection methodology – guidelines and performance

Abstract

Risk Based Inspection (RBI) is a much used method for planning inspection intervals in the oil and gas industry. The RBI method has over the recent years proved to show fruitful results with regards to proactive risk measures and continues to show results of increased safety, more reliable and predictable systems and a more economical routine for maintenance and inspection activities. However, some weaknesses in the method have been discovered; the method lacks a clear definition of risk and avoids assessing the uncertainties in calculations, data and judgements which potentially can lead to unwanted consequences. In order to assess this weakness, the ERBI method was developed by Selvik, Scarf et al. (2010). The basic idea behind the method is that uncertainties are communicated to the management through an extended uncertainty evaluation which integrates the results from the risk analysis and the uncertainty analysis. This thesis presents and discusses the ERBI methodology and provides an enhanced description of how to perform the ERBI method. The methodology is taken a step further; from a theoretical framework to a recommendation of practice. The recommended practice enhances some of the basic ideas of the ERBI methodology and maximises the benefits by using the method. The additional assessments of uncertainty and sensitivity in the ERBI methodology produce some increase in the time needed to perform the process, as well as resources required. The purpose of the thesis is to show that with an effective method of performing the ERBI, the increase of resources can be minimal – without compromising on the safety.