Anatomy of a Safety Analyses

A safety analysis is a structured way of looking at a system to find out what could go wrong, how bad it would be, and what needs to be done about it. It starts with understanding the system, then works through finding hazards, judging their risk, adding protections, checking the protections work, and writing everything down. The goal is to catch problems before they happen, rather than reacting to them after an accident.

Some of the most common safety analyses are

1. HARA

2. FMEA

3. STPA

4. FTA

5. FMEDA

6. HAZOP

7. Others (E.g. Ishikawa, Human Factors analyses)

More details on these analyses are available in this blog post

General anatomy of safety analyses

The general process of a safety analyses looks like Fig 1.

Fig: Anatomy of a safety analyses

Step 1 - Identify the system

Define what the system is, its boundaries, and how it connects with other systems or the environment. Understand how it works, from inputs to outputs, so you know what normal operation looks like before looking for problems.

Step 2 - Identify hazards

Find out what could go wrong using structured methods such as HAZOP, FMEA, checklists, or what if analysis, instead of just brainstorming. Go through the system step by step or part by part so nothing gets missed.

Step 3 - Assess risk

Work out how serious each hazard is by looking at severity and how likely it is to happen: Risk = Severity x Probability. This helps rank the hazards, so you know which ones need attention first.

Step 4 - Identify mitigation

Check if existing measures already control the hazard, and if not, figure out what new measures are needed. These can lower the severity, lower the likelihood, or both, and may involve design changes, procedures, or protective equipment.

Step 5 - Is the risk reduced?

Check the risk again after adding mitigation to see if it actually went down and decide if the remaining risk is acceptable and reasonable. If it is not acceptable, go back to step 4 and add more mitigation.

Step 6 - Verify

Confirm the mitigation actually works as expected, using reviews, testing, or simulation. This makes sure the assumptions made on paper hold true in real life.

Step 7 - Document

Write down the whole process, including the system definition, hazards found, risk assessments, mitigations chosen, and verification results. This keeps a clear record that can be checked later or reused if the system changes.

Conclusion

Safety analysis is the backbone of safety engineering. Performing a thorough safety analysis is essential for identifying safety requirements, defining mitigations, and building a defensible safety case.