Last edit: 26/06/2023

Evidence of the need to adopt an approach that covers all phases of a system Safety Lifecycle was illustrated in a study undertaken by the UK Health and Safety Executive. The study analysed a number of accidents and incidents involving Safety-related Control Systems. The figure at the side shows the primary causes of failure for each lifecycle phase.

Based on the HSE study, more than 60% of failures were ‘built in’ the safety-related system, before being taken into service. Whilst the primary causes by phase will vary, depending upon the sector and complexity of the application, what is self-evident is that it is important that all phases of the lifecycle be addressed if Functional Safety is to be achieved.

That, again, is the reason why IEC 61508 puts so much emphasis on the Safety Lifecycle of the Safety Control System.