CONTROL ROOM DESIGN AND ERGONOMICS
GENERAL MODELS
Before entering discussions about the different forms of models for human/computer systems in the process industry, it is important first to look more closely at the reasons behind the demand for computerisation and automation.
2.1.1 Motives fOR Automation and Computerisation
As in other industries, there is usually a requirement that investments must be economically profitable. One expectation of computerisation may be that it will lead to reductions in personnel (and thereby reductions in cost) or that the demand for qualifications among the staff could be reduced, thereby also reducing long-term costs. There may also be expectations that computerisation will increase income by, for example, increasing production capacity or bringing improvements in product quality. Another important reason for computerisation may be to reduce costs by reducing the disturbances in production and thereby achieving more efficient use of production capacity.
Apart from these economic profitability requirements, there are other motives for investing in computerisation. Pressure to automate may be due to the demands from employees and/or authorities in order to reduce the risks to workers or the community in situations where there is a danger of exposure to substances that could damage a person’s health or the environment, or to eliminate the risk of explosion.
Even if the economic profitability requirements are high within a process industry, it is no longer common to have great expectations that computerisation will lead to great reductions in staff numbers. Studies carried out by Ergolab[2] have not shown any direct relationship between the degree of computerisation and staffing levels (Ivergard et al., 1980). On the other hand, considerable increases in production volume have often resulted from increasing the degree of computerisation. This is typical, for example, within the paper industry.
In the electricity generating industry a relationship has been suggested between levels of automation and staffing. This is shown in Figure 1.2. When automation starts, drastic reductions can be made in the number of personnel. As automation continues, only smaller personnel reductions can be made, and eventually the curve tends to level out. One can even speculate that, if the automation level is pushed very high, the personnel requirements may actually increase again. By automation level in this context we mean the size of the investment, which is made for controlling the process using different types of automatic aid (for example, computer-based control systems). Even within process industries today, such a high level of automation has been reached using traditional technology that no further radical staff reductions could realistically be expected.
Within the electrical power industry, and to some extent the petrochemical industry, the most important reason for automation is thought to be that of achieving safer and more reliable production. In some of the petrochemical industries studied (Ivergard, Istance, and Gunther, 1980), the demand for production quality was an important motive. Lately, energy savings and environmental concerns have become important motives for automation.
The reason that there is no great reduction in staffing levels often lies in the fact that a certain minimum manning level is required to handle any disruptions or emergencies that may occur. In addition, the requirement for maintenance, service, and monitoring in a plant does not diminish as a direct result of automation. It is even quite likely that these tasks will tend to increase. Although computerisation may not substantially alter the size of the workforce, it inevitably brings about major changes in work roles. The traditional control room operator’s job changes extensively, and maintenance staff and their counterparts also discover that their job content alters. It is important to determine which tasks can suitably be combined into the new working roles required when introducing computers.
Studies carried out during the 1970s and 1980s show that there is a tendency for people to retain their traditional work roles, with special operators to monitor the process and other operators needed for maintenance, service, and repair. Planning and optimisation tasks connected with the control system become the work of technicians and management staff. This form of role demarcation in conjunction with computerisation has several disadvantages, particularly for the control room operators. It often results in the operator doing a daily job requiring lower levels of qualification, but it does not lead to the recruitment of operators with fewer qualifications. This is because occasionally—for example, during interruptions or under special operational conditions—the operators need at least their original level of competence to deal with these circumstances. Because people do not need to use the abilities that they are required to have, they get too few opportunities to practice
their job skills to be able to cope with the difficult peaks in the work. In addition, the level of attention becomes much too low to allow for a suitable degree of readiness to cope with demanding situations when they do arise.
Some of the companies studied (Ivergard, Istance, and Gunther, 1980) attempted to create new job roles consisting of combinations of tasks in process plants. This has been shown to have many advantages, including increasing competence. In most of the plants studied, it should also have been possible upon computerisation to require control room operators to perform more of the production planning and optimisation tasks, although examples of this are not forthcoming.
During the past decade there has been a clear tendency to increase the competence levels among control room operators. In studies carried out in the paper and pulp industry and in the production of hydroelectric power, most control room operators have advanced university technical training. There are also discussions for the 24- hour shift teams to include computer experts. There are still different opinions if the operators should mainly be working in the control room or whether their work tasks should also be carried out in the plant. In some segments of the paper and pulp industry, there seems to be a trend for operators to also work outside the control room,
It might be imagined that with computerisation, companies would, at least as a secondary aim, attempt to create interesting and meaningful jobs for the operators. However, there seem to be no examples of companies using the introduction of computerisation to attempt to enhance the quality of work. It is not possible to elaborate this issue here; we shall only deal with questions which are of more direct relevance to production.
It is usually suggested that it is desirable for operators to have some control over their own work and that the work itself should not be too ‘machine-bound’. It is also desirable for the work to be experienced as a whole, and for the operators to feel that they are performing a fulfilling job.
A characteristic of process control work is that one is working with a continuous operation, which means that the operators can seldom experience the type of satisfaction which comes from performing a complete task. On the other hand, a similar form of satisfaction can be obtained from knowing that the required qualitative and quantitative standards have been achieved in the work. One company studied gave the operators regular and clear information on the extent to which the qualitative and quantitative requirements were being fulfilled in order to provide work satisfaction (Ivergard, Istance, and Gunther, 1980).
The degree to which the operator is bound to the machine is largely determined by the design of the process. A continuous process—as distinct from a batch process—necessarily means that it is the process itself which determines the time and pattern of the work, and the operator must work according to the requirements of that process. The time scales are dependent on the dynamic time characteristics and response times of the process. In a process industry with continuous operations there is thus a high degree of time-bound work. This form of time-bound control is seldom experienced by the operators as being particularly stressing, especially where the processes have a high inertia, which means in practice that it is never second-by-second control, or even minute-by-minute control. What is more important is the degree of instructional control (that is, having to resort to reading instructions in case of disruptions or similar events). Here, different types of process industries show considerable differences. The operators in industries with ‘high’ demands for safety often have a high degree of instructional control as a form of safety net for the planners and management. This is particularly true in the nuclear and the electricity industries. Other types of process industries, such as the petrochemical industry, have a very low degree of instructional control by virtue of the fact that the operators are largely allowed to determine for themselves the actions that should be taken under different circumstances.
