Safety systems events

Buys, R. J., and Clark, J. L. Events and Causal Factors Charting. Revision 1, Idaho Falls, ID System Safety Development Center, Idaho National Engineering Laboratory, 1978. (DOE 76-45/14 SSDC-14)... 

If the verification confirms that the analyzed failure mode has no negative effects on system safety, the failure mode can be accepted. In the opposite case however we know that the failure mode, if actually occurs, can affect the system safety properties. In such case FDR can provide example event scenarios that lead to a contradiction of safety. Those scenarios can then be very helpful while considering possible redesign of the component objects. The results of the failure mode injection campaign are collected in the OF-FMEA tables (see Table 1). 

Design optimization studies provided a fire detection system employing minimum water which will effectively prevent between-bay flame propagation in the event of a process fire. The cost of installing quick-acting mechanical fire gates was avoided without affecting system safety of the CASBL. 

In the process-improvement or outcomes-measurement approaches, medication-use system redesign should 1) identify and assess lynchpin safety components of the medication-use cycle as well as improving event capture and reporting, 2) develop a medication system safety... 

Safety Device — An instrument, control, or other equipment that acts, or initiates action, to cause the furnace to revert to a safe condition in the event of equipment failure or other hazardous event. Safety devices are redundant controls, supplementary controls utilized in the normal operation of a furnace system. Safety devices act automatically, either alone or in conjunction with operating controls, when conditions stray outside of design operating ranges and endanger equipment or personnel. 

Safety and reliability of chemical process plants are such important issues, they deserve the best techniques to prevent problems occurring. To minimize risks resulted from operating problems and hazardous events, process system safety and reliability analysis is often employed. This is a rigorous approach undertaken to improve system reliability and safety. The approach consists of three main tasks hazard identification, risk estimation, and risk control. 

The most frequently reported systemic adverse events were hypertension, arthritis, urinary tract infection, and hypercholesterolemia. Of the 36 patients reporting a serious adverse event, 11 exited the study for that reason. Serious adverse events were reported by 23 of the 98 anecortave acetate-treated patients and 13 of the 30 placebo-treated patients. Five deaths from lung carcinoma, heart failure/ cerebrovascular accident, accidental injury, or myocardial infarction were reported. However, none of these serious adverse events or deaths was assessed as related to study treatment. An independent safety committee concluded that there were no clinically relevant medication-related or administration-related safety concerns. 

The results of this Phase IIA multiple intravitreal injection clinical study of anti-YEGF therapy expanded the favorable safety profile reported in the Phase IA single-injection study. Specifically, the Phase IIA study showed that three consecutive anti-pegaptanib sodium intravitreal injections given monthly did not cause serious ocular or systemic adverse events. The adverse events encountered appeared to be unrelated to study drug and were generally minor. In most cases they were probably related to the intravitreal injection procedure or to the PDT therapy. These results provided the basis for the Phase III pegaptanib sodium trial described below. 

Unlike production, engineering, and other functions, when things do not happen within the safety and health realm, this is a positive. When employees are being injured, chemical being spilled, procedures not being followed, and related events, this is a negative and often means that there is a problem within the safety and health system. Safety and health professionals often need to think on their feet to critically and creatively develop solutions to address the needs of the situation. The corrective action(s) often does not come from the standards and regulations but from the mind of the safety and health professional. Safety and health is as much an art as it is a science. 

Safety approaches based on systems theory consider accidents as arising from the interactions among system components and usually do not specify single causal variables or factors [112]. Whereas industrial (occupational) safety models and event chain models focus on unsafe acts or conditions, classic system safety models instead look at what went wrong with the system s operation or organization to allow the accident to take place. 

As every loss event results from the interactions of elements in a system, it follows that all safety is system safety [p. 12]. 

To promote learning about incident investigation, Ferry wrote extensively about and suggested inquiry into System Safety, Change Analysis, The MORT Process, Multilinear Events Sequencing, and D. A. Weaver s Technic of Operations Review. 

The heart of the book is its presentation of Sequentially Timed Events Plotting (STEP). The accident investigation methodology presented relies on a new conceptual framework, building on system safety technology and the safety assurance systems of MORT (management oversight and risk tree). 

While MORT is based on the fault tree method of system safety analysis, its logic diagram does not require statistical entries and computations for event probabilities. MORT is presented as an incident investigation methodology and as a basis for safety program evaluation. 

As every loss event results from the interactions of elements in a system, it follows that all safety is systems safety . The safety community instinctively welcomed the systems concept when it appeared during the stagnating performance of the mid-1960s, as evidenced by the ensuing freshet of symposia and literature. For a time, it was thought that this seeutingly novel approach could reestablish the continuing improvement that the public had become accustomed to however, this anticipation has not been fulfilled. 

A technical system normally has a number of standby components (components which become active only after demand). Components of the monitoring and safety systems belong to this category. These systems are devised to cope with accident initiating events. They form the barriers between the initiating and the undesired event. The latter only occurs if all barriers fad. The situation is shown schematically in Fig. 9.10. Obviously in the same system initiating events can occur for whose control various barriers may become effective, and initiating events which directly lead to the undesired event, for example the spontaneous failure of a chlorine pipe. 

The first step for a successful FTA is to define the objective of the FTA. The resulting scope of the FTAs will depend on the exact phrasing of the top-level event as well as the scope of the controlling System Safety Assessment (e.g. see Fig. 2.5). Careful... 

In most civil aviation System Safety Assessments, this event originates from a Function Hazard Analysis (FHA, see Chapter 3), but it can also come from any other hazard identification technique (e.g. ZS A or PRA). An FTA is a deductive approach (i.e. top down) that determines how a given state (i.e. the undesired event) can occur. It does not identify all failures in a system in a way that inductive tproaches (such as an FMEA) would. 

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. 

Preliminary System Safety Assessment The PSSA should have already been conducted and should have highlighted some of the architectural/installation requirements (such as physical and electrical segregation) needed to ensure appropriate levels of redundancy in system functionality during potential failure events. 

Recommendations as to how the System Safety Assessment needs to take account of any event independence vulnerabilities (refer Section 8.2). 

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