Task: Update Safety and Reliability Analysis
The hazard analysis should be frequently reviewed and updated as design decisions are made, solutions are modified, and requirements change.
Disciplines: Development
Purpose
The purpose of this task is to ensure that the safety and reliability analysis of the system remains valid throughout the life of the project.
Relationships
Main Description
The hazard analysis is a key document for safety critical systems as it combines the description of the hazards, the level of risk, system faults that can lead to the hazard, and the control measures all together in a single view. The Fault is a non-compliance of the system that can lead to the identified hazard. The severity is a measure of how bad the hazard is (an arbitrary scale of 1-10 is used often used). The Risk is a value computed by the likelihood multiplied by the severity of the occurrence. This task keeps the hazard analysis up to date, re-performing fault tree and failure modes and effect analyses as appropriate.
Steps
Examine changed elements for safety and reliability impact
As requirements change or design decisions are made, these can increase or decrease either safety or reliability (or both). Those changes must be examined to see if they impact or even invalidate the existing hazard analysis.
Perform Fault Tree Analysis
FTA analyses how faults and conditions interact to produce hazards.
Perform Failure Modes and Effect Analysis
FMEA looks at how failures accumulate to produce undesirable conditions (hazards).
Identify new and changed hazards
Hazard that are changed (such as by increasing or decreasing their likelihood or severity) and newly introduced hazards need to be added into the hazard analysis.
Quantify risks for new or changed hazards
Risks need to be determined by quantifying the nature of the hazards in terms of likelihood and severity.
Update Hazard Analysis
The hazard analysis needs to be updated when a change in requirements, design, or environment affects the safety and reliability of the system.
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