Risk Assessment: Theory, Methods, and Applications

CHAPTER 10

CAUSAL AND FREQUENCY ANALYSIS

10.1 INTRODUCTION

This chapter deals with the second question in the triplet definition of risk: How often will the hazardous event occur? To answer this question, it is often necessary to identify and analyze the possible causes of the hazardous event. The potential hazardous event must be identified and defined prior to the causal analysis, for example, by using the hazard identification methods described in Chapter 9.

10.1.1 Objectives of the Causal and Frequency Analysis

The objectives of the causal and frequency analysis are to:

1. Determine the causes of the defined hazardous event. How far the causal sequences should be pursued depends on the objective of the analysis and the data available.
2. Establish the relationship between the hazardous event and the basic causes.
3. Determine the frequency of the hazardous event based on a careful examination of the basic causes and the causal sequences.
4. Determine how important each cause is in relation to the frequency of the hazardous event.
5. Identify existing and potential proactive barriers and evaluate the efficiency of each barrier and the barriers in combination.

10.1.2 Methods for Causal and Frequency Analysis

Five different methods of causal and frequency analysis are described in this chapter:

Cause and effect diagrams

Cause and effect diagrams have their origin in quality engineering, and can be used to identify causes of a hazardous event. The method is easy to use and does not require ...