Safety engineering reducing hazards

Considering only the causes of past accidents is not going to be effective for software problems or when new technology is introduced into a system. Computers are introduced, in fact, in order to make previously infeasible changes in functionality and design, which reduces the effectiveness of a fly-fix-fly approach to safety engineering. Proper hazard analyses examining all the ways the system components can contribute to an accident need to be performed. 

Industrial fire protection and safety engineers attempt to eliminate hazards at their source or to reduce their intensity with protective systems. Hazard elimination may typically require the use of alternative and less toxic materials, changes in the process, spacing or guarding, improved ventilation or, spill control or inventory reduction measures, fire and explosion protective measures - both active and passive mechanisms, protective clothing, etc. The level or protection is dependent on the risk prevalent at the facility versus the cost to implement safety measures. 

Safety engineering is the discipline that attempts to reduce the risks by eliminating or controlling the hazards [p. 3],... 

System safety engineering An engineering discipline requiring specialized professional knowledge and skills in applying scientific and engineering principles, criteria, and techniques to identify and eliminate hazards, or reduce the risk associated with hazards (MIL-STD-882). 

Incorporate Safety Devices if identified hazards cannot be effectively eliminated or their associated risk adequately reduced to acceptable levels through system design, that risk should be reduced through the use of engineering controls and safety devices. These may include fixed, automatic, or other protective safety design and hazard limitation or control features or devices. Also, when applicable, provisions should be made for periodic functional checks and maintenance of any safety devices. 

One primary role for engineers in achieving safety is prevention. The role requires recognition of hazards and applying designs that eliminate and reduce hazards. This focus on designing for safety has increased in the last decade or so. 

Finally, a computer code provides only a value of keff, not a criticality safety analysis. The safety engineer must identity possibly hazardous situations, such as spills, flooding, or double batching, and use the computer code to evaluate them. Use of Monte Carlo calculations together with experimental data and calculatlonal models serves to reduce the number of computer calculations and to provide a cross check of results. 

The most important thing to remember is that system safety engineering is a combination of management and systems engineering practices applied to the evaluation and reduction of risk in a system and its operation. The objective of system safety is to identify hazards resulting from the use or operation of a system and to eliminate or reduce the hazards to an acceptable level of risk. 

Most would agree that the primary focus of safety engineering is to prevent unsafe conditions. By eliminating hazards altogether, by reducing the severity of a hazard, or by reducing the likelihood that conditions will lead to an undesired event, accidents can be prevented. 

Although the primary role of safety engineering is to prevent unsafe conditions, it must reflect the hundreds of design standards for safety (enforcement) and reduce the opportunity for errors and unsafe acts by users through designs that reflect human limitations and capabilities 84 The Hazard Control Priority Tree provides an orderly strategy for selecting controls for hazards 85... 

The system safety case of corrrse varies from sector to sector. The core of a nuclear system safety case is (i) a deterministic analysis of the hazards and farrlts which could arise and cause injury, disability or loss of life fiom the plarrt either on or off the site, and (ii) a demonstration of the sufficiency and adequacy of the provisions (engineering and procedural) for ensuring that the combined frequencies of such events will be acceptably low. Safety systems will feature amongst the risk reducing provisions comprised in this demonstration, which will thus include qualitative substantiations of compliance with appropriate safety engineering standards supplemented (where practicable) by probabihstic analyses of their reliabilities. Other techniques which may be used for stracturing the safety case include fault and event tree analysis, failure mode and effects analysis (FMEA) and hazard and operability studies (HAZOPS). 

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