Indicators of barrier availability

In Chapter 7, we introduced the concept of barriers against losses. Two examples were shown—one of barriers against exposure to hazardous chemicals and the other of the prevention of fires and explosions. We may use this concept to define a different set of performance indicators, i.e. that of barrier availability. This is defined as the probability that a barrier is available when it is needed and ranges from 0 to 1 (or from 0 to 100 per cent). These types of performance indicators have by their nature to be specific to the type of hazard that is to be prevented. Let us illustrate this principle by two examples. 

All three indicators may be measured through sampling techniques of the type described in Section 18.2. 

Example 2 Similarly, we may define performance indicators for the availability of barriers against fires and explosions in a refinery such as  

Duration of significant gas leakage in percentage of total production time. (A more practical indicator is the frequency of significant gas leakage.) 

Availability of such safety systems as fire and gas detection and active fire protection. 

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Example 1 Figure 7.2 illustrated four different barriers against the exposure to hazardous chemicals. In a plant for the manufacturing of aluminium rims, different types of solvents are used in the paint shop. These solvents represent a hazard to the operators, who may inhale them or get exposed through the skin. Below are examples of indicators of barrier availability for this specific case ... 

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