The STPA Process

Like HAZOP, STPA works on a model of the system and has guidewords to assist in the analysis, but because in STAMP accidents are seen as resulting from inadequate control, the model used is a functional control diagram rather than a physical component diagram. In addition, the set of guidewoids is based on lack of control rather than physical parameter deviations. While engineering expertise is still required, guidance is provided for the STPA process to provide some assurance of completeness in the analysis. 

STPA (System-Theoretic Process Analysis) can be used at any stage of the system life qrcle. It has the same general goals as any hazard analysis technique accumulating information about how the behavioral safety constraints, which are derived from the system hazards, can be violated. Depending on when it is used, it provides the information and documentation necessary to ensure the safety constraints are 

Identify the potential for inadequate control of the system that could lead to a hazardous state. Hazardous states result from inadequate control or enforcement of the safety constraints, which can occur because  

Determine how each potentially hazardous control action identified in step 1 could occur. 

While the analysis can be performed in one step, dividing the process into discrete steps reduces the analytical burden on the safety engineers and provides a 

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