Safety in the System Life Cycle

Even today in the United States there are about 13 deaths daily in the workplace and 4 million injuries per year (Barab, 2012), which means we have to better integrate system safety into all engineering aspects. Studies conducted at Stanford University estimate the cost of accidents for nsers of conunercial and industrial construction at 1.6 billion annually. Hidden costs were found to be two to 18 times higher. Researchers also found that construction safety research over a 10-year period showed irrefutable 

Of conrse, the statistics vary from industry to industry what is important to note is that accidents do happen, even minor ones, bnt they can be prevented. 

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Case Studies of Poor Application of Safety in the System Life Cycle... 

Safety in the system life cycle Describes the gated review, approval, and iterative process that define how system safety is incorporated into the system life cycle, especially during design, development, implementation, and operations. 

The integration of safety into the system life-cycle stages is shown in Figure 2.1. The choice of steps within the life cycle may be redefined as project requirements mature. Modification of the life cycle for specific customer or program needs is known as tailoring. ... 

The Concept of Operations, or ConOps, is a document generated early in the system life cycle and is used to capture behavioral characteristics required of the system in the context of other systems with which it interfaces and it captures the manner in which people will interact with the systan for which the system must provide capabilities. Generation of the ConOps will allow the requirements analysis team to clearly understand operational needs. The rationale for performance requirements will be incorporated into the decision mechanism for later inclusion in the System Design Document and lower-level specifications. The ConOps will help identify safety cases that must be proven in the V V test plans. The ConOps will... 

Development of the Specification Tree will identify existing elements of the system, and those that must be designed, procured, or otherwise implemented. This must occur as early as possible in the system life cycle. At each element or node of the tree, a specification is written and as the system development matures, a corresponding individual verification of the system design, performance, or safety will be performed. 

Safety analyses must be available and used starting in the early acquisition, requirements development, and design processes and continuing through the system life cycle. 

Step lb There are CMA requirements which may not be readily derived from Step la, but are attributable to vulnerabilities and/or systemic errors in the design, build or operation of the system (i.e. systemic errors). The reason such additional assessment is required is due to the ease of designing a system which is complex to use, difficult to maintain and hard to recover in the event of failures/malfunctions. If something can be done incorrectly during the system life cycle, then at some point in time, chances are that it will be done incorrectly. Failure to consider the impact of design on expected human performance may lead to gross misjudgement of both total system safety and operational effectiveness. 

Section 3.6 Synthesis. Includes the approach and methods to transform the fimctional architecmre into a design architecture (hardware, software, and humans to support the system life cycle), to define alternative system concepts, to define physical interfaces, and to select preferred product and process solutions. Describes how requirements are eonverted into detailed design specifications for hardware, software, human engineering, manpower, personnel, safety, training, and interfaces. Approaches and methods for the engineering areas, quahty factors, and engineering specialty areas in Section 3.2 are also defined. In addition, nondevelopmental items and parts control are included. 

System safety program The combined tasks and activities of system safety management and system safety engineering that enhance operational effectiveness by satis ng the system safety requirements in a timely, cost-effective manner throughout all phases of the system life cycle (MIL-STD-882). 

The failure mode and effect analysis (FMEA) is one of the more familiar of the system safety analysis techniques in use. It has remarkable utility in its capacity to determine the reliability of a given system. The FMEA will specifically evaluate a system or subsystem to identify possible failures of each individual component in that system, and, of greater importance to the overall system safety effort, it attempts to forecast the effects of any such failure(s). Because of the FMEA s ability to examine systems at the component level, potential single-point failures can be more readily identified and evaluated (Stephenson 1991). Also, although the FMEA should be performed as early in the product life cycle design phase as possible (see Figure 3.4), based on the availability of accurate data, the system safety analyst can also use this tool, as necessary, throughout the life of the product or system to identify additional failure elements as the system matures. 

A structured argument, supported by a body of evidence, that provides a competing, comprehensive and valid case that a system is or will be adequately safe for a given application in a given environment. The process accomplishes this by addressing each of the operational safety objectives negotiated for the system. It includes articulation of a roadmap for the achievement of safety objectives that are applicable to later phases of the system life cycle. RISC emphasizes that a determination of adequate safety is the result of a deliberative decision making process that necessarily entails an assessment of risks and tries to achieve a balance between the system s safety performance and its performance in other areas. 

A sixth phase of the system life cycle, the disposition or termination phase, is the time that a product or system is removed from service. In certain cases, the removal of a product may in itself create a hazardous situation. A good example is asbestos removal from a building or light transformer replacement due to PCBs. Safety professionals monitor these situations so both the worker and the public are protected. 

The objective of this Safety Guide is to provide guidance on the collection of evidence and preparation of documentation to be used in the safety demonstration for the software for computer based systems important to safety in nuclear power plants, for all phases of the system life cycle. 

When a computer system is used in a safety-related application then this must be borne in mind at all stages in the software life cycle, i.e. specification, design, testing etc. and it is the particular influence of safety requirements on each of these stages which we shall be studying in this section. All systems consist of both hardware and software and factors relating to both... 

The system is the combination or interrelation of hardware, software, people, and the operating environment. In system safety engineering, you must look at the system from cradle to grave. In other words, the system life cycle is the design, development, test, production, operation, maintenance, expansion, and retirement (or disposal) of the system. A nuclear power plant is one large system with operators, pressure subsystems, electrical and mechanical subsystems, structural containment, safety systems, etc. A far simpler example is a boy riding his bike. The bike, the boy, the street (with all its traffic conditions), the weather, the time of day, and even other children make up the system of boy on his bike. 

Before it is defined what SACs exactly are the question shall be pursued for what SACs are usefiil and necessary. SACs involve several benefits in the Product Life Cycle. SACs assure safe operation of products by prescribing demands, which ensure the safe deployment of a system. SACs are important to give users clear safety-relevant instructions. Consequently, SACs are necessary for safety. They are prescribed compellingly... 

Normally, each of these life-cycle phases occurs sequentially, but occasionally, development tasks are performed concurrently, spirally, or incrementally to shorten and/or simplify the development process. Regardless of the development process used, sequential, concurrent, spiral, or incremental, the system life-cycle phases shown in Figure 2.85 basically remain the same. The life-cycle stages of a system are important divisions in the evolution of a product, and are therefore very relevant to the system safety process. System safety tasks are planned and referenced around these five phases. In order to proactively... 

This section discusses a generic safety life cycle, illustrated in Figure 4, and its relationship to the system life cycle. The first row represents a generic and simplified version of the development process. The second row shows the main phases of the safety life cycle, which consists of Preliminary Hazard Identification (PHI), Functional Hazard Assessment (FHA), Preliminary System Safety Assessment (PSSA) and System Safety Assessment (SSA). The primary question to be answered during each phase is shown at the bottom of Figure 4. 

The System Safety Assessment (SSA) shall answer the question Does the implemented system achieve tolerable risk The system must inqilement all safety requirements and must provide the intended functionality such that the remaining risk is kept at an acceptable level. In order to assure this, test methods such as those proposed by lEC 61508 are applied. Thereby it is verified that the safety goals are achieved and that the safety requirements are considered accordingly in the design. SSAs are consequently performed in an iterative way over the remainder of the system life cycle. In this context the safety case report has to be regarded as a living document that must be kept up-to-date especially with regard to modifications of the system or the system environment. 

Stage Gate SG2 forms the most important strategic milestone in the integrated life cycle becanse it determines the finther comse of the project. The developed design specification, the re-worked plans and the updated effort and cost estimates allow management to re-evaluate the project and to decide upon its future. If the decision is to continue the project, the activities of System Safety Assessment (SSA) and of system development are triggered. Those activities are monitored by project control. 

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