Implementation of the risk triad algorithm to determine the probability of failure in pipelines: case of external corrosion

Abstract

This paper describes and discusses a case of application in the hydrocarbon transportation industry of the so-called risk triad probabilistic model discussed by Kent Muhlbauer (or Quantitative Risk Reference Model algorithm), to establish the probability of failure (PoF) of a pipeline event, in particular the external corrosion threat. The model uses probabilistic mathematics to combine the variables and capture both individual impacts and the accumulation of minor effects through OR and AND logic gates. The use of these logic gates in risk models represents a distinct improvement over older methods, as it provides a better representation of how the parameters that materialize a threat behave. In this model, the variables affecting the PoF are grouped in three groups or elements, exposure, mitigation and resistance, which are a function of the threat or potential damage mechanism to which the asset under study is subject. After obtaining the PoF value, it is contrasted with the numerical values associated with the probability of failure in Table 4.2 of API RP 581, it is crossed with the CoF results and thus a risk ranking is obtained that allows optimizing resources by applying them to the highest risk assets. The results are presented after applying them to the external corrosion threat.