People and Work Context

Human beings will always be a part of the decision-making process in plant operations and therefore there will always be opportunities for human error to contribute to abnormal situations. At various points in the process, people can contribute to abnormal situations by not responding with appropriate reactive, anticipatory, or compensatory actions or by responding with inappropriate actions which causes or escalates process upsets. The consequence of human error varies depending on the nature of the abnormal situation and the point at which the upset is detected. In order to fully understand the role of plant personnel, it is important to characterize the internal and external characteristics of the decision-making context that contribute to non-action when action is required or inappropriate action. The following characteristics are based on site visit comments and requests made by plant personnel.

Internal Characteristics

  • Training/skill—Operation teams should understand the how the process works and more importantly and how to use the DCS to monitor the process, diagnose upsets, and execute appropriate actions during an abnormal situation. Currently, the lack of training contributes to abnormal situations by creating situations in which some personnel do not know what the DCS is doing or what the best way of identifying or solving a problem is.

  • Practice/experience—Operation teams should have the requisite experience to effectively complete their tasks. Furthermore, the experience and practice should be distributed across personnel so that cooperative work load sharing can take place, particularly during upsets. For example, if a plant has changed its operations room or modified its DCS system, upsets will be more likely because people will have to gain experience with the new configuration.

  • Stress—Operation teams must be alert but not overwhelmed during upsets because high levels of stress will increase the likelihood of human errors in performance. Stress can be due to various external factors such as task demands and work flow issues which will be described later. Commonly reported stresses include the obnoxiously loud horn used to annunciate alarms and the telephone calls from plant personal and local residents.

Other internal characteristics which were not directly observed at the site visits but have been found to be influences include intelligence, motivation/work attitude, personality, emotional state, physical condition, and cultural background.

External Characteristics

  • Organizational structure—How the operations team is structured can have an impact on the probability of an upset. For example, if a single individual is the holder of most of the DCS knowledge then there is no way of coordinating workload during an abnormal situation as well as no checks of decisions made by the operator. Another example, is a situation in which there is a de facto leader but the leadership role is neither acknowledged nor is standardized across shifts in terms of title or location in the process.

  • Communication—Given that plant operations is a coordinated effort within a plant unit, across units in a plant, and in the field, the ability to communicate and information share is critical to plant operations. Upsets can occur because plant personnel are unable to coordinate actions. For example, it is currently difficult to send messages to plants affected by disturbance while at the same time taking compensatory or corrective action. In addition, miscommunication or no communication at all may occur across shifts which leads to inappropriate action. It is also the case that the operations team and maintenance personnel are not able to coordinate their actions because they do not have terminal access to each others actions.

  • Procedures—The lack of procedures or procedures that are not context-sensitive can contribute to abnormal situations. Procedures are only valuable if they are used. Several individuals have commented that existing procedures are not written with the context of use in mind (e.g., upset situations in which actions need to be executed quickly). Consequently, the procedures are often designed in a manner which makes them more of nuisance than an aid which leads to difficulty in obtaining compliance.

  • Work practices—Work practices and ways of completing tasks are sometimes not documented or somehow transferred to new personnel. This can contribute to abnormal situations by creating moderately trained personnel who do not fully understand the nature of the process and its relation to operations procedures and tasks. This situation over time can create a personnel pool with significantly different degrees of expertise and knowledge.

  • Task demands—The task demands on the operations team affects the likelihood of human error. For example, the task criticality, frequency and repetitiveness of tasks, time constraints, suddenness of onset, risk, and duration of tasks all creates levels of stress which affect performance. For example, if the operations team is trying to avert a plant shutdown and are presented with 30-40 alarms in a matter of minutes, the task demands would be high and stress would increase.

  • Environment—The physical work space that the operations team works in can affect the occurrence of abnormal situations. Site visits have illustrated some of the environmental factors that can affect performance. For example, operation teams have mentioned that the noise level can be distracting, particularly the alarm horn and that lighting is not adequate for working.

Other external characteristics which can influence operator effectiveness include the plant design, work schedule, availability/adequacy of special equipment, tools and supplies, staffing levels task criticality; frequency and repetitiveness of tasks; time constraints?

In conclusion, plant personnel have many things to monitor and maintain in a plant to keep the plant operating at peak efficiency while at the same time maintaining security and safety. The interplay among process, equipment, and personnel factors result in abnormal situations. Section 3 presents a model of how an abnormal situation develops over time and the interplay among the various root causes through its resolution.