System safety concepts definitions

I am aware that my outline of The System Safety Idea does not fit precisely with any of the several definitions of system safety published. It encompasses most, and goes beyond several. I hope that it s of interest to more generalists in the practice of safety than are now applying system safety concepts. 1 am confident that the application of system safety concepts in the business and industrial setting would result in significant reductions in injuries and illnesses. 

By the strictest definition, a fail-safe system is one that cannot cause harm when it fails. The term fail-safe is used to describe a device which, when it fails, fails in a way that will cause no harm or at least a minimum of harm to other devices or danger to personnel. Fail-safe is a system safety concept that, in theory, is intended to ensure a system remains safe, or in a safe state, in the event of a failure, thereby preventing a mishap while alternative action is being... 

Unfortunately, the term system safety does not convey a clear meaning of the practice as it is applied. Published definitions of system safety are of some help in understanding the concept, but they do not communicative clearly. To move this discussion forward, and to give indications of the differences in the definitions of system safety, I quote from five sources. 

A complex PEM electrolysis system with 100 MW is definitely more than a big electrolysis stack and a gathering of components. It must rather be integration of design, material selection and technical engineering on one hand and the interaction of electrochemical and electro technical subsystems on the other hand. Additional big-style production know-how, a transparent security and safety concept as well as an experienced and competent commissioning and service organization must be available. Paired with over 15 years of experience in research and development of PEM electrolysis these factors build a solid fundament for the realization at Siemens. 

The DOD system safety programs tend to be more standardized than those of some other agencies, primarily because MIL-STD-882B serves as a foundation for the effort. However, considerable variation in programs, concepts, interpretations, definitions, and approaches occurs, even within the DOD community. This variability is most pronounced in the attempts of contractors to interpret and conform to system safety requirements. 

In addition to updated content of the first edition, the revised second edition of the Basic Guide to System Safety has a more expanded and useful glossary of terms it also contains a new chapter describing the basic concept, utility, and function of the hazard and operability study (HAZOP) and what-if analysis. Both of these analytical techniques have been used quite routinely and successfully in the petrochemical industry for decades. As with all analytical methods and techniques presented in this text, it is suggested that the HAZOP smdy and what-if analysis have definite application to general industry operations as well. 

Therefore, the question still remains as to the proper definition of safety. One possible improvement of the previously presented MIL-STD-882 definition might be that safety is a measure of the degree of freedom from risk in any environment (Leveson 1986). Hence, safety in a given system or process is not measured as much as is the level of risk associated with the operation of that system or process. This fundamental concept of acceptable risk is the very foimdation on which system safety has developed and is practiced today. 

Preliminary hazard analysis is one of the early steps in a system safety project. This step also creates assessments of risks associated with each hazard. This step defines possible corrections for the risks. The product of this step is a tabular inventory of hazards for the system under consideration. The PHA fits best during early system stages, such as concept definition, design, and development. 

The system life cycle consists of six phases concept, definition, development, production, deployment, and disposition. At the end of each phase, a safety review is conducted. A decision is then made whether to continue the project or place it on hold, pending further examination. 

The concept of ALARP helps with respect to the economic considerations necessary in risk decision making. A good and easily understood definition of ALARP may be found in the draft of MIL-STD-882E, the Department of Defense Standard Practice for System Safety ... 

System Safety The Concept This chapter outlines the system safety idea in terms that relate well to the definition of the practice of safety given in Chapter 2. Lessons can be learned from the successes attained by system safety practitioners. System safety is hazards and design based. So is the entirety of the practice of safety. As opportunities arise for generalist safety professionals to participate in the design processes, the need for system safety skills will be apparent. 

Most of the current safety techniques and concepts we use today were bom at the end of the World War II. Operations research led the way, suggesting that the scientific method could be applied to the safety profession. In fact, operations research gave some legitimacy to the use of quantitative analysis in predicting accidents. One of the earliest concept definitions for systan safety (looking at safety from a system perspective) first appeared at the Fourteenth Annual Meeting of the Institute of Aeronautical Sciences in New York City in January 1946. The Organization of... 

The central concept in system safety is the definition of a hazard. It is important to spend some time nnderstanding what appears intnitive to all of ns. For snccess, a design or production engineer has to be able to identify and correct or control these hazards. Once a hazard is defined, the system safety process can start to unfold and make sense. The hazard reduction precedence is the philosophical basis for most safety control systans across industry. And finally, engineering standards are part of the structure that ensures that all technological systans have some level of safety. System safety optimizes the safety process. 

Ericson II, A. C. 2011a, August. Concise Encyclopedia of System Safety Definition of Terms and Concepts. Hoboken, NJ Wiley. 

Existing well-defined process for the derivation of safety requirements have been followed and applied within the new fiamework. The author analysed the concept of the safety requirement fiom the system point of view and proposed a minor clarification of the definition and the topology of a safety requirement as a system safety objecU in relation to defence/protection measures. 

Which general targets could be formulated for a safety concept. ISO 26262 clearly defined that the functional and technical safety concept should be defined derived from the ITEM Definition, a system on vehicle level and the resulting safety goals from the Hazard and Risk Analysis. 

In this context we often find a lot of indications and requirements from the definition of the vehicle system and the partial networks descriptions, which need to be realized that can exclude certain microcontroller safety concepts or at least make them appear ineffective. 

In September 1963, the USAF released MIL-S-38130. This specification broadened the scope of the system safety effort to include aeronautical, missile, space, and electronic systems. This increase of applicable systems and the concept s growth to a formal Mil-Spec were important elements in the growth of system safety during this phase of evolution. Additionally, MIL-S-38130 refined the definitions of hazard analysis. These refinements included system safety analyses system integration safety analyses, system failure mode analyses, and operational safety analyses. These analyses resulted in the same classification of hazards, but the procuring activity was given specific direction to address catastrophic and critical hazards. 

The SSPP is a formal documented plan that serves as a management tool for implementing an effective SSP. A well-prepared and documented SSPP is the key to a successful SSP. The SSPP should be written to cover all aspects of the SSP. It should also be written to cover all phases where system safety work is to be performed, that is, concept definition, design, test, deployment, operation, upgrade, and disposal. The SSPP describes and formalizes the system safety management and engineering tasks and activities it is the how-to document that provides the what, when, why, and who for the SSP. 

Concise encyclopedia of system safety definition of terms and concepts /... 

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