Failures: active

A very important contribution in this socio-technical era is made by Reason (Reason, 1990). He made a distinction between active failures, and latent conditions. The active failures are in general failures made by those at the sharp end of the accident causation (e.g. technical and human failures). Effects are felt almost immediately. Latent conditions are removed in time and space from the sharp end of the accident causation (e.g. organizational and technical failures) creating conditions for active failures to be made. A strict boundary between both concepts cannot be made and in reality can be seen as a sort of sliding transition. Here, the two concepts are separated... 

Figure 3 Latent condition - active failure model of accident causation passing through...

Identify the affected safety barriers Identify if, how and where safety barriers are affected by the identified latent conditions and active failures (resulting in identified precursors). 

As stated by Reason (Reason, 1997), the active failures resulting in precursors and the latent conditions cause the holes in the safety barriers, leading to an accident. The active failures result in precursors which were identified, while the latent conditions were roughly divided into information flows and resources types. The latent conditions explain why precursors still exist. They also explain the holes in the safety barriers. Subsequently, the identified types of latent conditions are used to check if they affect the identified safety barriers. The safety barriers can be affected negatively, positively or not at all, by the identified types of latent conditions. 

A mismatch between operator procedures and the automatic control system of the reactor (see also Table 17) was the first active failure identified in this scenario. This precursor was still present mainly due to a shortage of people. Literally it was said that the pressure relief valve would open if the wrong value was inserted into the reactor s control system. The second precursor was the failure of the pressure relief valve (see also Table 17), which was not known to the responsible person who decided to ignore the difference between procedures and control system. The pressure relief valve failed, because resins stuck in the valve after it was used for the first time. Consequently the second time the valve was opened it was at a much higher pressure due to the build up of resins in the valve. If this second precursor had not been observed in time by damp on the pipes situated above the pressure relief valve or by the alarms in the control room a possible accident scenario existed. This was especially dangerous as the alarms in the control room are often ignored because of the high incidence of false alarms (see also Table 17), which was the third precursor present. 

The test activity itself activates failure upon the next use of the process... 

Alternatively, processes such as failure mode and effects analysis or root cause analysis can be used to identify systems ripe for quality improvement activities. Failure mode and effects analysis is a prospective procedure used to identify areas for quality improvement before they become a problem (Cohen et al., 1994 DeRosier et al., 2002 NCPS, 2001). Once pos-... 

Define latent and active failures and the role each plays when a medication error occurs. 

Figure 8.5. Mohr circles for two cases (a) Active failure (b) Passive failure.

Active failures—events before which there were no adverse consequences and after which there were. Active failures are usually the result of personnel decisions or actions. These same actions may have resulted in safe outcomes on previous occasions, but... 

Immediate outcome—the adverse state the system reached immediately after the active failure. Examples are release of agent, plant damage, or personal injury. Reporting and investigation flow charts supplied by the Army indicate that the severity of outcome often determines the incident s prominence for managers, the workforce, or the community, which in turn drives subsequent responses. Incidents with more salient outcomes naturally receive more scrutiny, which may bias the data set used for analysis. 

The committee s analyses of past chemical events at Johnston Atoll Chemical Agent Disposal System (JACADS) and Tooele Chemical Disposal Facility (TOCDF) indicate that the cansal factors are similar to those associated with breakdowns of other safety-critical systems. Release of chemical agent may be triggered by equipment design flaws and failures, by procedural deficiencies, and by human actions—i.e., by both latent and active failures (see Chapter 2). 

Secondly, from many seeds only a few flowers grow. As a consequence, the society must be willing to accept a substantial number of failures. Further those who fail should not be unduly punished but rather accommodated in ways that will revitalize their interest in creating new activity. Failure in some of the industrialized western countries can be as difficult as it is in closed societies as in the Soviet Union. 

The first study found 40 active failures (i.e., direct error precursors) and nine latent failures (i.e., dormant states predisposing the system to later errors). Four broad classes of active failures were ... 

In addition, it should be demonstrated analytically that the mechanical systems can withstand a single active failure including failure of any auxiliary electric power source and not prevent delivery of sufficient cooling water to maintain the plant in a safe shutdown condition. A technique suitable for this analysis is a Failure, Modes, and Effects Analysis (FMEA). IEEE Std. 353-1975, "Guide for General Principles of Reliability Analysis of Nuclear Power Generating Station Protection Systems," provides additional guidance on the preparation of FMEAs. 

OMITTED ACTIVITY FAILURE MODE ASPECT OF IMS AFFECTED PROBABILITY P FAILURE COST C CPN SIGNIFICATINE FAILURE MODE OMISSION COSTS... 

---