Failures human error

Core damage and containment performance was assessed for accident sequences, component failure, human error, and containment failure modes relative to the design and operational characteristics of the various reactor and containment types. The IPEs were compared to standards for quality probabilistic risk assessment. Methods, data, boundary conditions, and assumptions are considered to understand the differences and similarities observed. 

The primaiy causes of accidents arc mechanical failure, operational failure (human error), miknown or miscclhmcous. process upset, and design error. Figure 14.4.1 is the relative number of accidents that liave occurred in tlie petrochemical field (on a percentage basis), There are lliree steps that normally lead to an accident ... 

An event tree provides a diagrammatic representation of event sequences tliat begin with a so-called initiating event and terminate in one or more undesirable consequences. In contrast to a fault tree, which works backward from an undesirable consequence to possible causes, an event tree works forward from the initiating event to possible undesirable consequences. The initiating event may be equipment failure, human error, power failure, or some other event that has the potential for adversely affecting an ongoing process. 

A fault tree is, itself, a Boolean equation relating basic events to the top event. The equation can be analyzed quantitatively or qualitatively by hand or by using computer code(s). If it is analyzed quantitatively, the probabilities or frequencies of the intermediate events and the top event are calculated. If it is analyzed qualitatively, a list of the failure combinations that can cause the top event is generated. These combinations are known as cut sets. A minimal cut set (MCS) is the smallest combination of basic events that, if they occur or exist simultaneously, cause the top event. These combinations are termed "minimal" because all of the basic events in a MCS must occur if the top event is to occur. Thus, a list of MCSs represents the known ways the top event can occur, stated in terms of equipment failures, human errors, and associated circumstances. 

Advances in information technology and the necessity of improved efficiency have resulted in increasingly automated and interlinked infrastructures, and have created new vulnerabilities due to equipment failure, human error, weather and other natural... 

Latent component failures, human errors, and related imsafe acts and errors are all results of weaknesses in our management systems. This is why the terms root cause and management system weaknesses are used interchangeably. The term latent failure or latent error is still used in some academic settings. 

A slightly more structured approach uses AVhat-If Analysis,(i) which involves the team asking What if questions that usually concern equipment failures, human errors, or external occurrences. Some examples are What if the procedure was wrong What if the steps were performed out of order The questions can be generic in nature or highly specific to the process or activity where the incident occurred. Sometimes these questions are preprepared by one or two individuals, which may also potentially bias the discussion. 

Process Hazard Analysis (PHA) can be defined as the application of a systematic method to a process design in order to identify potential hazards and operating problems. It determines the causes and consequences of abnormal process conditions that arise from equipment failure, human error or other events. The goal is to determine whether opportunities exist to reduce the risks of the toll s hazards and then to implement warranted action items. The AJChE CCPS guideline Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples is a good resource for fully detailed approaches to process hazard analysis. It provides an introduction to hazard evaluation as well as guidance on ... 

In order to illustrate the method, we can take the example of a pump as a component. It may fail to start or to stop when requested, provide too low a flow rate or too low a pressure, or present an external leak. The internal causes for pump failure may be mechanical blockage, mechanical damage, or vibrations. The external causes may be power failure, human error, cavitation, or too high a head loss. Then the effect on the operation of the system and external systems must be identified. It is also useful to describe the ways for detecting the failure. This allows establishing the corrective actions and the desired frequency of checks and maintenance operations. 

Despite all safety precautions, equipment failure, human error and other external events can sometimes lead to increased pressures beyond the safe levels, resulting in a relief event. These possible events are described above, but what are the potential lines of defence and why use relief systems which go beyond the simple use of an SRV The SRV is in fact only a part of the relief system and definitely the most important one. 

Date Deficiencies Failure Human Error Malfunction Deficiency Technique Mind-set... 

This is, however, not the case and cannot be achieved. Apart from the— although remote—possibility of wrong dimensioning (e.g. walls too weak) components of technical systems can fail, humans can commit errors in operating the technical system or external threats such as flood, storm or lightening may lead to failures within the plant. Thus, temperature and pressure increases or other damaging events may be triggered. In addition, it is conceivable that safety systems are not available due to component failures. Probabilities for such events may be assessed. However, the instant in time of a component failure, human error or destructive external event cannot be predicted. 

Often too much reliance is placed on the FMEA/FMECA, while ignoring threats that can arise from outside the system (e.g. common cause failures, human error, multiple failures, etc.). 

Internal events Equipment failures Human error Other internal events External events Combination of events... 

A formal hazard analysis of the anticipated operations was conducted using Preliminary Hazard Assessment (PHA) and Failure Modes and Effects Analysis (FMEA) techniques to evaluate potential hazards associated with processing operations, waste handling and storage, quality control activities, and maintenance. This process included the identification of various features to control or mitigate the identified hazards. Based on the hazard analysis, a more limited set of accident scenarios was selected for quantitative evaiuation, which bound the risks to the public. These scenarios included radioactive material spills and fires and considered the effects of equipment failure, human error, and the potential effects of natural phenomena and other external events. The hazard analysis process led to the selection of eight design basis accidents (DBA s), which are summarized in Table E.4-1. 

The starting point for the safety analysis is the set of PIEs that need to be addressed. A PIE is defined in Ref. [1] as an identified event that leads to anticipated operational occurrences or accident conditions . PIEs include events such as equipment failure, human errors and human induced or natural events. The deterministic safety analysis and the PSA should normally use a common set of PIEs. 

The mission of this independent federal agency is to investigate accidents at plant sites and determine root causes. The Board has found that the root-cause deficiencies are often within safety management systems, but can be ary factor that would have prevented the accident. Some other causes involve equipment failures, human errors, unforeseen chemical reactions or other hazards. 

FAILURE Human Error (of success tasks AND human tasks for mitigation of technical failures). Technical Failure (of main functions AND functions for mitigation of human errors Failure (of Tasks, Functions AND mitigations)... 

Numerous studies and institutions interpret and quantify the vulnerability of chemical sites, processes, and transportation methods to the varied threats of mechanical failure, human error, industrial accident, natural disaster, vandalism, theft, or terrorism, including the U.S. Chemical Safety and Hazard Investigation Board. As a result, most facilities have instituted a combination of voluntary and mandatory security measures to consistently improve their safety record. Nevertheless, it is an incontrovertible fact that no amount of security guards, fences, alarms, or containment structures can entirely eliminate risk at a site that produces, uses, or stores hazardous material. In contrast, when the chemists and engineers responsible for industrial process design seek to modify the process itself, inherently safer conditions can be permanently and irreversibly built into the chemical industry and its facilities. 

For each hazardous event there could be a single or combination of precursors (system failures, sub-system failures, component failures, human errors or physical effects) that could result in the occurrence of the hazardous event. For example, a derailment would be considered to be a hazardous event as it can lead directly to injuries, whereas a broken rail would be classified as a cause precursor because without the occurrence of a subsequent derailment, no injury would occur. 

Equipment/control hardware failure Software failure Human error... 

Human error is not a cause of failure. Human error is the effect, or symptom, of deeper trouble. Human error is. . . systematically connected to features of people s tools, tasks, and operating systems. (15)... 

FTA is a top-down, deductive analytical method. In FTA, initiating primary events, such as component failures, human errors, and external events are traced through Boolean logic gates to an undesired top event, such as an aircraft crash or nuclear reactor core meltdown. 

Three nonsafety tools are used in safety analysis failure modes, effects, and criticality analysis (FMECA) human factors analysis and software analysis. Because these techniques are extremely helpful in finding eqnipment failures, human errors, and software mistakes, safety engineers have coupled them to their safety analyses. It is definitely worthwhile to understand how these tools can benefit you. 

This involves assessing the design, by means of reliability analysis techniques, to determine whether the targets can be met. Techniques include fault tree and logic block diagram and FMEA analysis, redundancy modeling, assessments of common cause failure, human error modeling, and the choice of appropriate component failure rate data. Reliability assessment may also be used to evaluate potential financial loss. The process is described in Work Instruc-tion/001 (Random hardware failures). 

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