Operations and Support Hazard Analysis

One last transformation of the hazard analysis technique that is worth investigating is the operations and support hazard analysis (O SH A). Most hazard analyses (and safety analyses, in general) are directed toward uncovering hardware design problems however, this is not the intent of an O SHA. Simply put, an O SHA identifies and evaluates the hazards associated with the operations of a system. As with all hazard analyses, it looks at hardware systems, software, facilities, support equipment, procedures, personnel, operating environment, natural environment, human-machine interfaces, and other interfaces, but with the telling difference of how all of these factors relate to the operation of the system by people. The O SHA is a very useful technique to understand how operations-focused hazards impact the system. It is not a human factors analysis. See Chapter 8 for more on human factors analysis. 

Many engineers perform an O SHA instead of a hardware hazard analysis. This is not a particularly good idea since the operations of a system or plant are intrinsically related to the hardware design. You may wish to use the O SHA as a separate, more in-depth look at operational aspects of the system, but not in lieu of other analyses. Actually, the best idea is to combine the O SHA with the hardware hazard analyses. Many times the human-machine interface is a very ambiguous area, and it is unclear which affects which. 

High hydrogen concentration leads to a fire devices in facility. 

Lack of means to detect toxic and highly toxic gases 

Undetected buildup of hydrogen gas due to failure to accurately calibrate and maintain gas detection system. 

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The final major type of analysis is the operating hazard analysis (OHA) or the operating and support hazard analysis (O SHA). The OHA is the analy-... 

Operating and support hazard analysis (O SHA) As described in NHB 1700.1(V1-A) and this document. The O SHA is to identify hazards and recommend risk reduction alternatives in procedurally controlled activities during all phases of intended use (NSTS 22254). 

The information recorded on the PHA worksheet, together with the PHA report, will greatly facilitate the performance of other benehcial system analyses (such as the subsystem hazard analysis, the failure mode and effect analysis, and the operating and support hazard analysis) that may be accomplished during the remaining phases of the product life cycle. 

Figure 8.1 Sample operating and support hazard analysis (O SHA) worksheet.

The ETBA is an analytical technique that can be of great assistance in preparation of the preliminary hazard list (PHL). It can also be quite useful in the development of a preliminary hazard analysis (PHA), subsystem hazard analysis (SSHA), or the more general system hazard analysis (SHA). The ETBA can also be used, depending on the specific system under consideration, in the development of the operating and support hazard analysis (O SHA), and, of course, during the MORT process from which the ETBA evolved. 

The second and more common hardware FMEA examines actual system assemblies, subassemblies, individual components, and other related system hardware. This analysis should also be performed at the earliest possible phase in the product or system life cycle. Just as subsystems can fail with potentially disastrous effects, so can the individual hardware and components that make up those subsystems. As with the functional FMEA, the hardware FMEA evaluates the reliability of the system design. It attempts to identify single-point failures, as well as all other potential failures, within a system that could possibly result in failure of that system. Because the FMEA can accurately identify critical failure items within a system, it can also be useful in the development of the preliminary hazard analysis and the operating and support hazard analysis (Stephenson 1991). It should be noted that FMEA use in the development of the O SHA might be somewhat limited, depending on the system, because the FMEA does not typically consider the ergonomic element. Other possible disadvantages of the FMEA include its purposefiil omission of multiple-failure analysis within a system, as well as its failure to evaluate any operational interface. Also, in order to properly quantify the results, a FMEA requires consideration and evaluation of any known component failure rates and/or other similar data. These data often prove difficult to locate, obtain, and verify (Stephenson 1991). 

The purpose of the Operating and Support Hazard Analysis (O SHA), sometimes called the Operating Hazard Analysis (OHA), is to... 

Operating and Support Hazard Analysis A system safety analytical technique (also know as the operational hazard analysis) which focuses primarily on the hazards associated with or caused/enhanced by the human/task interface of system operations. 

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