Safety assessment in industry 

Having systematically identified the risks and the safety measures that are present, an evaluation is made of whether the level of safety is high enough.

COWI carries out safety evaluations using both entirely qualitative methods and fully and semi-quantitative methods:

• Categorization of frequency and consequence and plotting them on risk matrix
• Using the ALARP principle that requires risk to be As Low As Reasonably Practicable
• Use of barrier diagrams that can be made as quantitative as necessary for the specific situation being studied
• Estimation of risk expressed as IR (individual risk) or PLL (potential loss of life) 
• Failure frequencies for main safety functions
• Use of interactive risk models (Bayesian networks) for more complex problems.

Barrier diagrams

COWI has developed the barrier diagram method in cooperation with industry clients who work with hazardous chemicals. A barrier diagram gives an overview of the most serious hazards and the safety measures (barriers) on which safety depends.

Barrier diagrams are similar to "bow-tie" diagrams but are more flexible and can show more information.

Safety barriers are assigned a number of points, depending on how effective they are. The principle is that the more frequently an incident is expected to occur or the more serious its consequences, the more barrier points are required. The effectiveness of barriers depends on technical, organizational and human factors. The operational assumptions made for the assessments must be fulfilled during operation and maintenance.