Safety (also called safety engineering) is the state of being "safe", the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be considered non-desirable. Safety can also be defined to be the control of recognized hazards to achieve an acceptable level of risk. This can take the form of being protected from the event or from exposure to something that causes health or economical losses. It can include protection of people or of possessions.
A system is defined as a set or group of interacting, interrelated or interdependent elements or parts that are organized and integrated to form a collective unity or a unified whole to achieve a common objective. This definition lays emphasis on the interactions between the parts of a system and the external environment to perform a specific task or function in the context of an operational environment. This focus on interactions is to take a view on the expected or unexpected demands (inputs) that will be placed on the system and see whether necessary and sufficient resources are available to process the demands. These might take form of stresses. These stresses can be either expected, as part of normal operations, or unexpected, as part of unforeseen acts or conditions that produce beyond-normal (i.e., abnormal) stresses. This definition of a system, therefore, includes not only the product or the process but also the influences that the surrounding environment (including human interactions) may have on the product’s or process’s safety performance. Conversely, system safety also takes into account the effects of the system on its surrounding environment. Thus, a correct definition and management of interfaces becomes very important. Broader definitions of a system are the hardware, software, human systems integration, procedures and training. Therefore system safety as part of the systems engineering process should systematically address all of these domains and areas in engineering and operations in a concerted fashion to prevent, eliminate and control hazards.
A “system", therefore, has implicit as well as explicit definition of boundaries to which the systematic process of hazard identification, hazard analysis and control is applied. The system can range in complexity from a manned spacecraft to an autonomous machine tool. The system safety concept helps the system designer(s) to model, analyse, gain awareness about, understand and eliminate the hazards, and apply controls to achieve an acceptable level of safety. Ineffective decision making in safety matters is regarded as the first step in the sequence of hazardous flow of events in the "Swiss Cheese" model of accident causation. Communications regarding system risk have an important role to play in correcting risk perceptions by creating, analyzing and understanding information model to show what factors create and control the hazardous process. For almost any system, product, or service, the most effective means of limiting product liability and accident risks is to implement an organized system safety function, beginning in the conceptual design phase and continuing through to its development, fabrication, testing, production, use and ultimate disposal. The aim of the system safety concept is to gain assurance that a system and associated functionality behaves in a safe manner and is safe to operate. This assurance is necessary. Technological advances in the past have produced positive as well as negative effects.
Root cause analysis
A root cause analysis identifies the set of multiple causes that together might create a potential accident. Root cause techniques have been successfully borrowed from other disciplines and adapted to meet the needs of the system safety concept, most notably the tree structure from Fault Tree Analysis, which was originally an engineering technique. The root cause analysis techniques can be categorised into two groups:
a) tree techniques, and b) check list methods.
There are several root causal analysis techniques, e.g. Management Oversight and Risk Tree (MORT) analysis. Others are Event and Causal Factor Analysis (ECFA), Multilinear Events Sequencing, Sequentially Timed Events Plotting Procedure, Savannah River Plant Root Cause Analysis System.
Failure Mode Effects Analysis
Failure mode and effect analysis (FMEA) was one of the first systematic techniques for failure analysis. It was developed by reliability engineers in the 1950s to study problems that might arise from malfunctions of military systems. A FMEA is often the first step of a system reliability study. It involves reviewing as many components, assemblies, and subsystems as possible to identify failure modes, and their causes and effects. For each component, the failure modes and their resulting effects on the rest of the system are recorded in a specific FMEA worksheet. There are numerous variations of such worksheets. A FMEA is mainly a qualitative analysis. A few different types of FMEA analysis exist, like Functional, Design and Process FMEA. Sometimes the FMEA is called FMECA to indicate that Criticality analysis is performed also.
An FMEA is an inductive (forward logic) single point of failure analysis and is a core task in reliability engineering, safety engineering and quality engineering (Quality engineering is specially concerned with the "Process" (Manufacturing and Assembly) type of FMEA). A successful FMEA activity helps to identify potential failure modes based on experience with similar products and processes or based on common physics of failure logic. It is widely used in development and manufacturing industries in various phases of the product life cycle. Effects analysis refers to studying the consequences of those failures on different system levels.
Functional analysis are needed as an input to determine correct failure modes, both for functional FMEA or Piece-Part (hardware) FMEA. A FMEA is used to structure Mitigation for Risk reduction based on either failure (mode) effect severity reduction or based on lowering the probability of failure or both. The FMEA is in principle a full inductive (forward logic) analysis, however the failure probability can only be estimated or reduced by understanding the failure mechanism. Ideally this probability shall be lowered to "impossible to occur" by eliminating the (root) causes. It is therefore important to include in the FMEA an appropriate depth of information on the causes of failure (deductive analysis).
An accident or mishap is an unforeseen and unplanned event or circumstance, often with lack of intention or necessity. It usually implies a generally negative outcome which may have been avoided or prevented had circumstances leading up to the accident been recognized, and acted upon, prior to its occurrence.
Here are a few common accidents within the medical community:
- Gun Safety
- Tool Safety
- Seat Belt
- Work Hazards
- ↑ Charles G. Oakes, PhD, Blue Ember Technologies, LLC.“Safety versus Security in Fire Protection Planning,”The American Institute of Architects: Knowledge Communities, May 2009. Retrieved on June 22, 2011.
- ↑ System Reliability Theorie, Models, Statistical Methods, and Applications, Marvin Rausand & Arnljot Hoylan, Wiley Series in probability and statistics - second edition 2004, page 88