Glossary · Functional safety
Hazard and risk analysis (H&RA)
Also known as: H&RA, hazard and risk assessment
German: Gefährdungs- und Risikoanalyse
In functional safety under IEC 61508 and IEC 61511, hazard and risk analysis (H&RA) is the lifecycle phase that identifies the hazards and hazardous events of a process or equipment, determines their causes, consequences and likelihood, and derives the risk reduction and safety functions required.
- Functional safety
In one sentence
Hazard and risk analysis identifies hazards and hazardous events and determines the risk reduction and safety functions a process needs.
Example
A HAZOP of a distillation unit identifies overpressure from a failed reflux pump; the H&RA then estimates the risk and concludes that a pressure trip with a SIL 2 requirement is needed.
How it applies
- Methods: H&RA typically combines a hazard identification method such as Hazard and Operability Study (HAZOP) with a risk estimation. Its results are the input to SIL allocation.
- Engineering: Each hazardous event is documented with its initiating causes, consequences and existing safeguards. The analysis also considers operating modes such as startup, shutdown and maintenance.
- Security: IEC 61511-1:2016 also requires a security risk assessment for the SIS, which links the H&RA to IEC 62443 practices.
- Documentation: Record assumptions, scenarios and conclusions in a traceable form, for example a Hazard log. The documentation team should carry the resulting residual risks and required operator actions into operating instructions and warnings.
H&RA vs. risk assessment under ISO 12100
Both follow the same logic of identifying hazards and estimating risk. H&RA is the term of the process-sector safety lifecycle and ends in required safety functions and SILs. Risk assessment under ISO 12100 is the machinery method, where risk reduction follows the three-step method and safety functions are rated with PLr or SIL.