System safety tools/techniques

Throughout the 1980s, three factors have driven system safety tools and techniques in areas other than the traditional aerospace, weapons, and nuclear fields. 

The safety community has the responsibility for providing the staff support to know, teach, and apply the specific system safety tools and techniques and to help establish and monitor system safety programs. 

Some of the hazard analysis (evaluation) techniques already used by the chemical industry include traditional system safety tools such as preliminary hazard analysis, failure modes and effects analysis, and fault tree analysis. 

System safety tools and techniques currently used primarily in the aerospace, weapons, and nuclear industries offer great potential for meeting these challenges. The systematic application of system safety fundamentals early in the life cycle to produce first time safe products and services can provide significant, cost-effective gains in the safety effort in transportation, manufacturing, construction, utilities, facilities, and many other areas. 

As Stated previously, system safety developed or evolved as a direct result of a need to ensure, to the greatest extent possible, reliability in the safe operation of a system or set of systems (especially when a given system is known to be hazardous in nature). While no system can be considered completely or 100% reliable, system safety is an attempt to get as close as practical to this goal. Over the years, numerous techniques and methods used to formally accomplish the system safety task have also evolved and have further expanded our capabilities to examine systems, identify hazards, eliminate or control them, and reduce risk to an acceptable level in the operation of that system. These analytical methods and/or techniques are known by many names such as— but certainly not limited to—the following common system safety tools ... 

Part 11 of this text details a number of the various common system safety analytical methods and techniques that are practiced in the system safety discipline. Each of these methods or techniques is usually conducted at specific points during the project or product life cycle, as indicated in Eigure 3.4. At this point, it is important to understand that a specific system or program may require the use of any or all of the system safety analysis techniques available to today s system safety professional. Each method has its own distinct purpose and function, and, as tools, each can be quite useful. 

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. 

In Part II, the reader was exposed to a variety of the most common tools and techniques currently used in the system safety profession. It is hoped that the numerous examples provided will assist in developing an appreciation for system safety analysis in the evaluation of risk, no matter how complex or simple the system may be. Although these various examples did not constitute complete and detailed analyses, it is presumed that enough information has been presented to ensure a basic understanding of common system safety analysis techniques and methods. 

It is also beneficial to use system safety tools from other industries. One snch tool is hazard analysis, which is used to help identify and control hazards in a syston. The technique, though invented in the military and aerospace industries and used in the mass transit industry, can easily be applied to the manufacturing world. In fact, facility hazard analysis is a specific use of hazard analysis in facility acquisition. The U.S. Navy has used it for many years in all of their facility constructions and renovations. The Navy has used it for such things as construction or modification of fuel depots, pier, and dry dock upgrades and for entire submarine bases. 

FHA is a powerful, efficient, and comprehensive system safety analysis technique for the discovery of hazards. It is especially powerful for the safety assessment of software. Since software does not have discrete failure modes as hardware does, the best way to identify software-related hazards is by evaluating the effect of potential software functions failing. Software is built upon performing functions therefore, FHA is a very natural and vital tool. After a functional hazard is identified, further analysis of that hazard may be required to determine if the causal factors of the functional failure are possible. Since the FHA focuses on functions, it might overlook other types of hazards, such as those dealing with hazardous energy sources, sneak circuit paths, and hazardous material (HAZMAT). For this reason, the FHA should not be the sole HA performed, but should be done in support of other types of HA, such as PHA and SSHA. 

A safety assessment is an iterative process within the overall development of the system. The techniques and approaches touched on in this section can be used to different depths at different stages in the development process. Different projects use a variety of safety tools/techniques in numerous combinations. There is much guidance material and many standards available on this subject (e.g. SAE ARP4761, DEE STAN 00-56, MIL-STD-882, etc.). 

How to use spectroscopic tools for the studies of nonaqueous electrochemical systems techniques and transfer systems Safety considerations... 

STAMP provides a new theoretical foundation for system safety on which new, more powerful techniques and tools for system safety can be constructed. Part III presents some practical methods for engineering safer systems. All the techniques described in part III have been used successfully on real systems. The surprise to those trying them has been how well they work on enormously complex systems and how economical they are to use. Improvements and even more applications of the theory to practice will undoubtedly be created in the future. 

In the simpler world of the past, classic safety engineering techniques that focus on preventing failures and chains of failure events were adequate. They no longer suffice for the types of systems we want to build, which are stretching the limits of complexity human minds and our current tools can handle. Society is also expecting more protection from those responsible for potentially dangerous systems. 

In 1985, the American Institute of Chemical Engineers (AIChE) initiated a project to produce the Guidelines for Hazard Evaluation Procedures. This document, prepared by Battelle, includes many system safety analysis tools. Even though frequently identified as hazard and operability (HazOp) programs, the methods being developed by the petrochemical industry to use preliminary hazard analyses, fault trees, failure modes, effects, and criticality analyses, as well as similar techniques to identify, analyze, and control risks systematically, look very much like system safety efforts tailored for the petrochemical industry (Goldwaite 1985). 

The MORT tools and techniques can be helpful in preparing a safety analysis report (SAR), the upstream safety product most frequently required for new DOE programs, but the more common system safety products (system safety program plan, preliminary hazard analysis, system/subsystem hazard analysis, operating hazard analysis) are not a dominant part of the MORT program and are seldom even referenced in System Safety Development Center (SSDC) documents. 

As a matter of fact, a toolbox offers a suitable analogy. Ideally, the system safety manager or engineer has a well-stocked toolbox of analysis types and techniques and is able to study the particular task at hand and select the appropriate tool or combination or tools to perform the task effectively and efficiently. This example is the correct application of the tailoring concept. 

System safety may grow as a separate discipline or the system safety effort may be absorbed into the mainstream of industrial safety, loss prevention, risk management, loss control, or some other program. A new name or buzzword may appear. Nevertheless, the need for first-time safe systems and for the application of system safety principles, tools, and techniques to systematically identify, analyze, and control hazards as early in the life cycle as possible (with continuing efforts throughout the life cycle) will continue to grow indefinitely. 

Analytical trees can be used in a variety of ways in the system safety effort. The most common application of analytical trees in current system safety programs is probably the use of fault trees for fault tree analysis (FTA). However, analytical trees can also be used as planning tools, project description documents, status charts, and feeder documents for several hazard analysis techniques (including fault tree analysis). Analytical trees can be multipurpose, life cycle documents and represent one of the most useful tools available to managers, engineers, and safety professionals. 

Change analysis is one of the techniques associated with the Department of Energy s management oversight and risk tree (MORT) approach to system safety. Unlike the MORT chart itself or some of the other tools and techniques associated with the MORT program, change analysis is a very simple, straightforward process that is relatively quick and easy to learn and to apply. 

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