Systems Hazard Analysis

The system hazard analysis (SHA) provides detailed analysis of hazards associated with the total system. 

The SHA is prepared as early in the design phase as possible, generally between 35% and 90% design. Timing is normally determined by the availability of subsystem and system design data. 

The SHA is normally prepared by the system safety working group and reviewed by management review boards. 

Detailed project description documents and drawings are required to perform an SHA. Additionally, relevant codes, standards, and regulations, the PHL, the PHA, and the SSHAs for the projects should be available. Access to lessons learned and reliability data is also needed. 

Failure inodes and effects analysis (FMEA) and fault tree analysis (FTA) are recommended techniques for the SHA. Energy trace and barrier analysis (ETBA) may also be appropriate. Change analysis is useful for evaluating changes made during the SHA. 

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Quality control in the upstream supply chain is part of our supplier approval system and regular supplier auditing. The applied control systems are based, as within our own factory premises on the HACCP systems (Hazard Analysis on Critical Control Points). These quality control systems have been elaborated for each individual raw material. It is our objective to source our raw materials as far as possible from approved suppliers these are suppliers who are able to guarantee the qualities we require. 

U.S. Army Soldier and Biological Chemical Command systems hazard analysis standard operating procedure... 

A systems hazards analysis (SHA) is a systematic and comprehensive search for and evaluation of all significant failure modes of facility systems components that can be identified by an experienced team. The hazards assessment often includes failure modes and effects analysis, fault tree analysis, event tree analysis, and hazards and operability studies. Generally, the SHA does not include external factors (e.g., natural disasters) or an integrated assessment of systems interactions. However, the tools of SHA are valuable for examining the causes and the effects of chemical events. They provide the basis for the integrated analysis known as quantitative risk assessment. For an example SHA see the TOCDF Functional Analysis Workbook (U.S. Army, 1993-1995). 

DeMil International. 2004. System Hazard Analysis TC-60 Controlled Detonation Ch ber, Draft Report, June 7. Aberdeen Proving Ground, Md. U.S. Army Edgewood Chemical-Biological Commmd. 

Level 2 System Principles External interfaces Task analyses Task allocation Controls, displays Logic principles, control laws, functional decomposition and allocation Validation plan and results, System Hazard Analysis... 

Software need not be treated any differently than the other parts of the system. Most safety-related software problems stem from requirements flaws. The system requirements and system hazard analysis should be used to determine the behavioral safety constraints that must be enforced on software behavior and that the software must enforce on the controlled system. Once that is accomplished, those requirements and constraints are passed to the software developers (through the black-box requirements specifications), and they use them to generate and validate their designs just as the hardware developers do. 

Representatives from the companies attend a joint Systems Hazards Analysis in which each PHA is treated as a black box. 

As from 2002 the Danish Veterinary and Food Administration (DVFA) has made it mandatory for businesses in the food industry to launch selfinspection programmes, which direct businesses to self-inspections and subsequently documenting and reporting failures to comply with the governmental food safety standards. These standards follow the EU-legislation and are organized in accordance with the principles embodied in the HACCP system (Hazard Analysis and Critical Control Points). 

Again the process involves a preliminary hazard analysis to be done very early in the concept stage, followed by subsystem hazard analysis as subsystems are developed, systems hazard analysis that looks at interfaces between subsystems, and, finally, the operating hazard analysis, which tends to add the human element and evaluate procedures. 

Laundry lists of analyses frequently mix types of analyses (preliminary hazard analysis, system hazard analysis, and operating hazard analysis) with the methods or techniques for performing analyses (fault tree analysis, energy trace and barrier analysis, failure modes and effects analysis, common cause analysis, change analysis, and so on). Whether fault hazard analysis is a type or a method depends upon the reference in use. For all practical purposes, fault hazard analysis and system (or subsystem) hazard analysis seem to be the same thing, which is apparently called gross hazard analysis occasionally. 

Hazard identification is continued throughout the design stage and documented in the preliminary hazard analysis (PHA), subsystem hazard analysis (SSHA), and the system hazard analysis (SHA). Even though the primary purpose of these products is to analyze previously identified hazards and to determine the adequacy of controls, every effort should be made to continue to identify new hazards, especially those associated with interfaces and changes. 

After the PHA is complete, first subsystem hazard analysis (SSHA) and, if required, system hazard analysis (SHA) are performed. Depending on the nature and complexity of the end product and the results of the PHA, SSHAs may be performed on all subsystems or just on selected critical subsystems. Unlike MIL-STD-882B, software analyses are not generally identified separately. If applicable, preliminary software hazard analysis is part of the PHA. Software should be treated as a subsystem and, if further software analysis is required, an SSHA can be performed on the software. 

Figure 8-4 shows a system hazard analysis worksheet. 

R0 HOUR SYSTEM SAFETY (CHAPTERS in PRUSRNARV HAZMTOMIALYSO (CHAPTERS) SUBSYSTEMS SYSTEM HAZARD ANALYSIS (CHPTt) OSMQE ANALYSE (CHAPTERS S.17) (CHAPTERS)... 

Based on the system safety program plan and recommendations from other analyses (PHA, SSHAs), a system hazard analysis (SHA) may be required. The SHA is initiated as soon as input data from the SSHAs are available and completed at the review milestone indicated in the SSPP, normally around 60% design. 

This system hazard analysis of a wet pipe sprinkler system was conducted using fault tree analysis (FTA). 

The purpose of the project evaluation tree is to provide a relatively simple, straightforward, and efficient method of performing an in-depth evaluation or analysis of a project or operation. It is best suited for performing operating hazard analysis and accident analysis. It can also be a valuable review and inspection tool. If adequate information is available, PET analysis may be helpful in performing preliminary hazard analysis, subsystem hazard analysis, and system hazard analysis. 

Fault hazard analysis is mentioned very frequently in system safety literature, sometimes as a type of analysis and occasionally as a technique. One NASA system safety document (NHB 1700.1-V3, System Safety) describes it as the analysis to be performed after the preliminary hazard analysis for further analysis of systems and subsystems and suggests that it can be either a separate analysis or an extension of the failure modes and effects analysis (NASA 1970). Most programs today (including NASA) refer to this analysis as the subsystem hazard analysis (SSHA) and the system hazard analysis (SHA). 

System hazard analysis (SHA) As described in NHB 1700.1(V1-A) and this document. The SHA is identical to the SSHA but at the system level. Once... 

Energy Trace Banter Analysis — Sid)system Hazard Analysis — Sul>syslem Hazard Analysis —AccidenUnciderd Artalysis — Change Analysis... 

I—Wh Review — System Hazard Analysis — System Hazard Analysis —Mgml OversighI A Risk Tree — Operating Hazard Analysis... 

The PHA (Figure 6.2) is perhaps the most critical analysis that will be performed because it is usually the first in-depth attempt to isolate the hazards of a new or, in some cases, modified system. The PHA will also provide rationale for hazard control and indicate the need for further, more detailed analyses, such as the subsystem hazard analysis (SSHA) and the system hazard analysis (SHA). The PHA is usually developed using the system safety techniques known as failure mode and effect analysis (FMEA) (Chapter 9) and/or the ETBA. Data required to complete... 

A subsystem hazard analysis (SSHA) or a system hazard analysis (SHA) may be required depending on the complexity of a given program or project. The SSHA and the SHA are often referred to as one in the same by many system safety professionals (Stephenson 1991). However, as explained here, the two methods are slightly different and, if used properly, provide for a more complete evaluation of a given system. 

Figure 7.1 Sample subsystem/system hazard analysis (SSHA) worksheet.

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