Latent conditions

The answer to the second question was obtained by using models from organizational control theory. A deviation can re-occur due to ineffective operation of the organization s control process. A theoretical model of this control process, in which causes of precursors can be expressed in terms of ineffective control elements of the organization s control process, was derived from existing models in literature. However, as safety literature shows, there are certain conditions shaping a situation that make these control elements ineffective. These conditions, sometimes called latent conditions in safety literature are the actual root causes of precursors and possible accidents. In this thesis a classification has been developed which identifies six main types of latent conditions (these six latent conditions are context related but... 

The case studies revealed a lack of overview regarding precursors, their underlying organizational root causes (the latent conditions) and their possible effects on safety barriers. This lack of overview created the opportunity for safety risks in the operational process, despite the presence of many safety indicators and measures. 

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...

From hindsight analyses of accidents by Heinrich (Heinrich, 1959), Turner (Turner, 1978), Leplat (Leplat, 1987), Reason (Reason, 1997), etc., it is known that failures or deviations in normal operations are present prior to, and are directly related with, an accident. From hindsight analysis as reported in FACTS, the failures or deviations as well as the accident trajectory or causal path, of 70 accidents are known. To derive the risk coverage area these deviations, are placed in the risk matrix. The only deviations taken into account are those which occur in the operational process and are part of the accident trajectory or causal path prior to the critical events as described in FACTS. So the latent conditions lying behind these operational deviations as described by Reason (Reason, 1997) are not yet taken into account but will be discussed in the following Chapter. 

The transformation, history, organizational values and norms, and external environment types of latent conditions are all latent conditions concerning information flows. The infrastructure and human types of latent conditions both concern resources. 

When these latent conditions create an unfolding situation, the safety barriers present in an organization can be seriously affected. Svenson (Svenson, 2001) identifies three functional categories of safety barriers, e.g. technical, human, organizational. These safety barriers can be activated by different safety barrier systems, such as the closure of a valve automatically by a computer or manually by an operator. Moreover, a safety barrier system can (simultaneously) operate more than one safety barrier, like an operator who can close a valve, connect a hose, or a computer which closes down a machine and alerts an operator, etc. 

A technical safety barrier represents technical equipment, whose function it is to arrest the accident/incident evolution so that the next event in the chain will not be realised. The human safety barrier is the suitable people, whose function it is to intervene and arrest the accident/incident evolution so that the next event in the chain will not be realised. The organizational safety barrier is the procedures, rules, guidelines, etc. present, which function to arrest the accident/incident evolution so that the next event in the chain will not be realised. In this thesis the latent conditions and precursors in an unfolding situation are considered to have three possible effects on the safety barriers negative, positive or none at all. 

The letters A to C in Figure 26 represent the possible interventions a company can make, to arrest the development of an accident. The interventions react to the situation as shown prior to them. The thick arrow represents a cause effect relationship that is so direct, no intervention can be implemented preventing the effect from occurring if the cause is not removed. In Figure 26 one relation is present, between the initial ineffective control elements and the precursors, implying that if latent conditions are present, the initial ineffective control elements are automatically present to and will automatically result into precursors. 

A Removal of the latent conditions initially causing the accident scenario. This is... 

In practice the presence of all three ways of intervening are needed. It is not possible to eliminate all latent conditions and there will always be conditions leading to possible ineffective safety barriers and ineffective control elements, which subsequently lead to precursors. Therefore, recovery is necessary, to intervene and arrest the precursors and ineffective safety barriers from evolving into a possible accident. Finally, because not all precursors can be effectively recovered, finally an overview of affected safety barriers is necessary to prevent an alignment of ineffective safety barriers and the presence of precursors that can escalate into an accident. 

By explicitly showing the cause-effect relationships from precursor via control to the latent conditions, recommendations for all three ways of intervention principles can be made. The next sub-Section will therefore discuss an approach where the concepts discussed in this Chapter can be used to display the working and influence of a control process on the safety of an organization. 

In the following sub-Sections the practical approach derived in the previous Chapter will be applied on this case study. Therefore, the precursors present inside the operational process are identified. Then, the control of the operational process will be modelled and analysed to find the ineffective control elements. Furthermore, the latent conditions causing the ineffective control will be retrieved and their impact on the existing safety barriers will be identified. Finally, improvement opportunities for the company will be indicated, together with some recommendations and enhancements for the applied concepts and the proposed practical approach. 

The next sub-Section will discuss how the latent conditions, that cause the identified ineffective control elements, affect the current safety barriers in the pesticide company. 

In this sub-Section the ineffective control elements are further analysed to retrieve the conditions causing their ineffectiveness. By checking all six types of conditions for their contribution to the ineffectiveness, the causal conditions can be identified. These causal conditions are the latent conditions. Subsequently, these latent conditions are used to explain why certain safety barriers are affected in the pesticide company. 

Table 9 The latent conditions of the ineffective control elements.

Furthermore, the eighth and ninth columns of Table 9, together called resources, show the other types of latent conditions, i.e. infrastructure and human resources. For the ineffective judgement element of the mixing process, in addition to the information flows relating to latent conditions the lack of knowledge of the human resources involved, contributed to the ineffective judgement. 

Likewise, the latent conditions from the ineffective observation of the product storage sub-process and the ineffective observation of the extrusion sub-process, the No.5 and No. 10 respectively from Table 9 can be derived. However, from the seven remaining ineffective steering elements no latent conditions could be obtained, which is displayed as the ... in Table 9. The steering element itself was so complex that no latent conditions could be unambiguously retrieved. Therefore, some additional research had to be performed, so that latent conditions could be retrieved for an ineffective steering element. This problem will be further addressed in Section 5.2. 

Once both latent conditions and precursors are identified in the company s control process and operational process, the effects on the company s safety barriers can be retrieved. Therefore, the safety barriers present around the transformation process will be identified, i.e. technical, human, and organizational safety barriers. Subsequently, the identified types of latent conditions are used to check if they affect the identified safety barriers either positively, negatively, or not at all (as discussed in the previous Chapter). How safety barriers are affected is illustrated by the example of the re-... 

Extend the control model concept, to reduce the steering element s complexity, enabling latent conditions to be derived from it. 

Identify the latent conditions Identify the conditions causing the control elements on the different hierarchical control levels to be ineffective. 

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). 

To identify the latent conditions which enable the initial ineffective control element. Contents... 

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