Critical operating tasks

A prime example of such an approach in the chemical industry is DuPont The American giant has established a powerful target-setting process that starts with so-called critical operating tasks (COTs). These are derived from financial origins at the business unit level, and cascade down through the plant to the production line. The system creates transparency for each production line employee about his or her targets and about how the individual s performance is linked to that of the whole unit (Fig. 12.4). 

A CTA can be undertaken to identify and analyse the human performance issues in critical operational tasks as defined for successful interaction. The initial CTA should focus on human performance aspects relating to the design of the human tasks including high-fiinction cognitive functions such as attention vigilance situation awareness etc. 

The final step is the selection of preventive maintenance tasks for all components found critical. Maintenance tasks are selected according to a specific selection logic which views all preventive maintenance operation in a ascending order of complexity lubrication, in-service monitoring, checks and tests, complete overhaul and scheduled replacement. 

According to this rating, a screening of the human performance is performed. Moreover, since a nominal task analysis has been performed to analyse all tasks in sequence, probabilities for human errors that can lead to deviations from the required sequence can be estimated. Critical PSFs have been also identified and their impact to the human error probability is evaluated with the FPE. Additionally, critical operating and recovery points needing improvements are identified. The imp act o f the se improvements to the overall hmnan performance is depicted through the use of the FPE tool. This whole process is explained with the use of a specific example. 

Consideration of deviation Did the maintenance program make allowances for human errors Was a two-person concept used for critical operations Did supervision monitor difficult, tedious, or other error-prone tasks ... 

Process models, operation tasks models and operators are not independent in the process operation. The operation task models (agents) evoke the suitable process models and make decisions on the calculation results under the supervision of the operator. Therefore, the participation of operator is critical to the success of the CIPOS. The procedure of consulting between agents and operators is similar to the interaction of the operation task models. In this situation, the operator can be looked as a special agent. The integration of the operation tasks and operators is also a collaboration resolution. So integration of process models, operation task models and operator is also depended on the internal knowledge base. The required rules can be created by the methods mentioned in the section 3.2. 

When doing so, there should be ooverage of all modes of tank operation filling, emptying, maintenance, transfers, and any other abnormal modes of operation etc. A critical (human) task list can then be created. Table 13 shows an example. 

A safety-critical requirement is a design requirement that is necessary to mitigate, or assist in the mitigation, of a hazard that has been designated as SC. It is also a requirement that is involved in the implementation of a SC function, operation, task, and so on. 

The validation plan is really a plan to audit the quality assurance trail of the SIS. The main validation task takes place after installation and ideally before critical operation of the SIS. Experience of validation work teaches that the task can be lengthy and difficult to conclude if it has not been done as an ongoing task from the start of design. Catching up on neglected QA trails is called retrospective validation and it is a very inefficient and fiustrating thing to have to do ... 

Although all instmctions/procedures have the same purpose and objectives, their significance varies and does so in direct proportion to the consequences of failure to comply. For example, a misunderstanding when reading the instructions on expense submissions may lead to inefficiency and delayed payment but, in reality, the consequences are unlikely to have any more impact than to inconvenience a small number of people. However, failure to comply with the instruction/procedure covering a safety critical operation or maintenance task could (as previously shown) result in fatalities. 

Has each task that has been identified as critical in the area of quality and/or safety been documented with full operating instructions and are these instructions reviewed regularly ... 

It should be expected that tasks for all operations are defined and those critical to quality and/or safety are identified. Critical tasks should have detailed operating instructions. 

Modem process plants grow increasingly complex with highly coupled unit processes. A result of this tendency is that tasks now often require a team rather than individual effort. Team training becomes increasingly important for the safe and efficient operation of plants. The aim of this section is to identify those PIFs which play a critical role in the collective efforts and communications of process workers. 

This technique sets out to collect data about near-incidents or critical events that have been experienced by the operating team but that are unlikely to be documented. The basic premise of the technique is that events that could have led to serious consequences would tend to be remembered by the workers. Through individual or group interviews, significant events are recalled which are then analyzed in order to generate useful information about the difficulties involved in the performance of a task, the adequacy of the operating procedures, any problems with the equipment or control panel design and so on. The technique can be used in three areas ... 

Disadvantages may arise because the behavior observed may not be fully realistic. A static simulation, for instance, may not reveal the true nature of operators dynamic interaction with the system. There is also the possible disadvantage of behavior in a simulator not fully replicating that found in the real situation. This can happen because of the absence of real stressors found in the actual task, for example, risk to life, criticality of the process, and presence of other workers and supervisors. 

Interactions refers to any jobs, tasks, or operations carried out by people who could directly or indirectly cause the hazard to be released. Direct interactions with the plant might involve breaking open pipework, opening reactors, etc. Indirect interactions would include remote activation of valves from a control room, or the performance of maintenance on critical plant items. Errors that might occur during these interactions could allow the harm potential to be released. This could occur directly (for example, a worker could be overcome by a chlorine release if an incorrect valve line-up was made) or indirectly (for example, if a pump bearing in a critical cooling circuit was not lubricated, as in the example in Chapter 1). The procedure as described above... 

Information on the types of human interactions with hazardous systems that occur would be obtained from sources such as plant operating instructions, job safety analyses and similar sources. These interactions are referred to as critical tasks (CT). 

PROBLEM DEFINITION. This is achieved through plant visits and discussions with risk analysts. In the usual application of THERP, the scenarios of interest are defined by the hardware orientated risk analyst, who would specify critical tasks (such as performing emergency actions) in scenarios such as major fires or gas releases. Thus, the analysis is usually driven by the needs of the hardware assessment to consider specific human errors in predefined, potentially high-risk scenarios. This is in contrast to the qualitative error prediction methodology described in Section 5.5, where all interactions by the operator with critical systems are considered from the point of view of their risk potential. 

Sequences of operations in different tasks which are very similar, apart from the critical steps which could have critical consequences when performed in the wrong situation (strong habit intrusions)... 

---