1. INTRODUCTION

Failure Mode and Effects Analysis (FMEA) is a form of nonquantitative analysis that aims to identify the nature of failures that can occur in a system, machine, or piece of equipment by examining the subsystems or components in turn, considering for each the full range of possible failure types and the effect on the system of each type of failure. Failure Mode and Effects Criticality Analysis (FMECA) is an extension of FMEA that assigns a rating to both the severity of the possible effects and their likelihood, enabling the risks to be ranked.

FMEA and FMECA are most applicable when only one type of impact is being considered, such as production loss, or safety, or environmental damage, not a combination of them. Where a combination of types of impact is to be considered, it is preferable to use rapid ranking that is structured and designed for computer sorting, and is thus more flexible.

However, both FMECA and rapid ranking use the same basic approach:

• subdivision of the equipment or operation into "bite-sized" subsections,

• for each subsection, systematically examining the potential for each of a checklist of possible failures or mishaps,

• for each identified failure or mishap, estimating the potential severity of the consequences and the likelihood, and

• determining a risk score for each identified failure or mishap.

2. FAILURE MODE AND EFFECTS ANALYSIS (FMEA)

FMEA is often undertaken by one person alone, but to meet the requirements of effective risk identification it is very desirable that it be...