An ‘incident’ usually occurs when a ‘system’ breaks down, as most systems have multiple ‘barriers’ that prevent failure; for example, we will be injured in an automobile accident if:
- we are involved in an accident;
- our reactions fail to avoid the accident;
- our automobile protective devices (air bags, etc.) fail; and,
When a pipeline fails due to external corrosion, the corrosion protection ‘system’ has failed (Figure 1):
- the coating has failed;
- the cathodic protection has failed;
- our inspections (internal and external) have failed to detect the corrosion;
|Figure 1. Corrosion Failures are Prevented by ‘Systems’ made up of ‘Barriers’ [1, 2].|
But… why does this ‘system’ break down? The barriers preventing the failure, are not perfect: they will have faults (holes), Figure 1. A failure from corrosion will occur if all the faults in the barriers line up. It is like ‘Swiss cheese’… and is called the ‘Swiss cheese model’ [1, 2].
Failure will only occur if all the faults in the barriers line up. Today we look at the engineering barriers, but others, such as management, culture, etc.
|Figure 2. Barriers Preventing Incidents.|
- J Reason, ‘Too little and too late: a commentary on accident and incident reporting systems’, in: Schaaf van der, et al. (Eds.), Near miss reporting as a safety tool, Butterworth Heinemann, Oxford. 1991.
- J Reason, ‘Managing the Risks of Organizational Accidents’, Ashgate Publishing Limited. 1997. ISBN 1 84014 104 2.