The workstation is often designed for one specific task—interfacing with the DCS—and thus has no capacity for other duties such as report writing or training. Similarly, there are often few, or inadequate facilities for using and storing manuals and communication equipment. Other ergonomic problems include broken or patched chairs, furniture never designed for 24-hour operations and no rest/recovery strategies incorporated into control room design. Resourceful operators often find ways of taking a break or getting some exercise, but few control room environments take into account operator downtime or well being into the design.
Distractions are myriad and create one of the most common environmental problems for operators. Distractions can come from anywhere: poor traffic flow through the building, non-essential personnel congregating in the control room; undisciplined telephone traffic; auxiliary equipment noise; doors opening; alarms sounding; other operators talking on the radio, etc. The list is endless but the point is distractions in the control room are not conducive to trouble-free operations.
To Err is Human
Human errors, such as those that led to the Texaco Pembroke incident, have forced the processing industry to respond by changing the way they design and build control rooms. Standards organizations have also started to produce guidance and best practices for building design. The industry has recognized that many of the systems used within the control room need to be addressed ergonomically using a human, or a user-centered design approach (Figure 2). ISO 11064 part 1 Ergonomic Design Principles for the Design of the Control Center reads in part:
"The combination of human and machines, in its organizational and environmental context, is considered as an overall system to be optimized. The optimization is achieved by developing solutions that emphasize and maximize the strengths, features and capabilities of both humans and machines in a complimentary fashion. The human component, the machine (hardware and software), the work environment, and the control (operation and management) shall be harmonized integrated during all phases of the design process, conceptual and detailed design, assembly and construction, commissioning, user training and operations."
Worldwide industrial practice has evolved to build new control buildings that will withstand a worst-case-scenario incident and still protect the inhabitants of the building. However, with the growth in centralization and the flexibility to move the building anywhere, industry has responded by moving non-critical people outside the battery limits and into a safe area. The API "Guidelines Management of HAZARDS Associated with Location of Process Plant Buildings, Recommended Practice 752" provides advice on building structures and locating personnel, but this is not a legal requirement, and is often not implemented in a new building project due to economic constraints.
Steps to Good Design
To generate a Functional Design Specification, ISO 11064 identifies a front-end loading methodology, but the organization also acknowledges that many of the other work design systems required to ensure human safety, such as health and well-being, are not fully identified or addressed by the standard.
The standards do, however, help the designer understand the use of space, considerations for workstation layout and design, and the use of other systems such as off-workstations. The methodology is a participatory process and uses an iterative design approach.
Regardless, important questions must be addressed before the design process is started. During the process the designer often has to deal with additional complexity, such as changes to the number of console operators; changes in DCS system and technology; a change in software and user interface design capability; or correcting previous design deficiencies or incorporating recent advances in control, process technology, operations and improved management systems.
Step 1-Identify Primary Users
Accurately defining the number of operators depends on new approaches to determining staffing levels. Most previous control room schemes have had more operators than required, or created an unevenly distributed work load. Operator roles and responsibilities must also be defined, and that dictates the console operator's span of control (how many operating units). The number of console operators is also influenced by organizational and management system constraints such as training.
Step 2–Identify HCI Design
Once the number of console operators has been determined, the next step in design a truly ergonomic system is to specify the Human Computer Interface (HCI) System.
Although it is difficult at this stage of a typical project to design the HCI, it is possible to generate a vendor independent specification which includes a graphics navigation strategy, a keyboard design and the number of screens per console. This HCI system guidance is specified in the EEMUA 201 Human Computer Interface Guidance document.