Design safety mechanism

Accidents and mishaps are the direct result of hazards that have been actuated. (Note Accidents and mishaps are synonymous terms, and mishap has become the preferred term in system safety.) Mishaps happen because systems contain many inherent hazard sources (e.g., gasoline in an automobile), which cannot be eliminated since they are necessary for the objectives of the system. As systems increase in complexity, size, and technology, the inadvertent creation of system hazards is a natural consequence. Unless these hazards are controlled through design safety mechanisms, they will ultimately result in mishaps. 

See Design Safety Feature, Design Safety Measure,Design Safety Mechanism, and Hazard Countermeasure for additional information. 

It should be noted that the terms safety feature, safety measure, safety mechanism, DSF, design safety measure, design safety mechanism, and hazard countermeasure are synonymous and can be used interchangeably however, most system safety practitioners tend to use the terms safety feature or safety measure most often. 

A fusible link is a design safety mechanism used for hazard risk mitigation. FUZE (FUZING SYSTEM)... 

Safe software is software that executes within a system context and environment with an acceptable level of potential mishap risk. This means the software will not cause any system hazards or prevent system design safety mechanisms from performing correctly, or the likelihood of causing these conditions is within acceptable bounds. 

The Safety Case produced for the Windscale Vitrification Plant in 1994 included a detailed and comprehensive assessment of fault conditions in the plant using HAZOP and Probabilistic Risk Assessment techniques. The Safety Case identified a number of major hazards. These major hazards, along with the protective measures, Operating Rules, and Safety Mechanisms designed to prevent these hazards or to mitigate them are briefly described below. 

A difference between [ISO 13849-1] and [lEC 62061] is that [ISO 13849-1] except E/E/PE based subsystems also covers mechcuiical, hydrauhc cuid pneumatic subsystems. But it is possible to use either [ISO 13849-1] or [lEC 62061] when designing safety functions that include subsystems based on mechanical, hydrauhcs and pneumatics. The difference is that in the case you choose [lEC 62061] you must find support for mechanical, hydraulic and pneumatic subsystems from [ISO 13849-1]. Information about this could be found in note 3 in table 1 in [lEC 62061]. 

Passive devices (fully automatic) the safety mechanism is integral to the device design, requiring no any additional actions by the user to activate the safety feature. For example, self-sheathing needle. 

Common cause Diversity means that the safety function is to be carried out in a redundant manner with different hardware/design principles/even completely different technologies (e.g., one a mechanical system, the other an electronic system so that in the former system the EMC effect will not exist). In practice a real common cause is dif cult to find because the failures of a multichannel system must by definition of a common cause occur at exactly the same time. The same hardware will always have different strengths and thus fail at a slightly different time. A well-designed safety system can take advantage of this gap in time and detect one failure before the other failure occurs. 

Main, B. W. and Ward, A. 1992, Angust. What do design engineers realty know about safety Mechanical Engineering, 114 44—51. 

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