Process operators supervise and control complex processes. To enable the operator to do an adequate job, we need to address several related topics, such as console design, process information design, navigation, alarm management, office software, and CCTV. Key to the operator job is information processing. Information comes in various formats, mainly visual.
- A HF analysis in control rooms usually reveals cluttered and ill structured data. Ill-structured data prevents the operator of acquiring good process awareness. Unplanned unit shutdowns or production losses have been reported, because operators missed vital process information.
- Existing graphics can often be simplified, by applying a set of straightforward, ergonomic guidelines on information display. A 50 to 80% reduction can be achieved, leading to an improvement of the operator task and more compact workplaces.
- An additional permanent process overview display is a powerful operator tool. An overview typically consists of key performance indicators and a selection of most important process variables.
- Graphics and interaction design have an impact on console design and vice versa. Improved display technology, such as higher resolutions and wide screens, enable better representations of symbols, process equipment, indicators, etc. Note that the frequently advocated 1:1 graphics conversion ignores these advantages.
- Graphics and interaction design have a major impact on operator workload. If it is difficult for one operator to get a full picture, the need may be felt to have two operators in the control room for the same process control job. If a task analysis shows that this is due to poorly designed graphics, more cost effective solutions can be implemented.
- Instrumentation upgrade project teams should consider a HF inspired graphics redesign approach, consisting of an operator task analysis, a review of existing graphics, and an analysis of the capabilities and limitations of the instrumentation system. Next, an Operating Philosophy and HMI Conventions have to be developed, agreed upon, and implemented.
- Download the article HMI Conventions for Process Control Graphics (here).
Example – simplify a graphic
Top shows the original graphic; below the result of a first simplification of piping.
Note: the number of screens on a desk basically determines console dimensions. A typical operator workplace has a status overview screen and 3 – 4 screens for process interaction and alarm handling. Nevertheless it is not difficult to find operator workstations with much more screens for one operator. This might be a sign that the presentation of process information is not optimal.
Example – large screen displays
The supervision and operating of a steam and electricity cogeneration power plant is carried out from this control room. Though several operators may be needed to supervise this process, they all need a full overview of the status of the electricity grid. Therefore, it is shown on a large wall mounted display.
Graphics are part of the operator interface of the process control system. The selection of graphics, detailed process data (controllers), alarm overview and other pictures is governed by interaction software. Depending on how this is organized, interaction requires space on the graphic real estate for a menu or control bar, usually repeated on each screen. If you want to have a one-touch access to each graphic, a button is needed for each graphic. Other examples of data repeated on each screen are time and date, the last three alarm lines, and a vendor logo, being shown on each display. The number of graphics has an impact on interaction needed. Of course, this also relates to the number of screens on the console, ease of selecting and finding data, ease of switching between graphics and so on.
Complex processes require tools to present an overall view of the processes to be supervised and the status of off-normal situations. Off-normal process information (commonly indicated as alarm) adds to the overview, improving operator awareness of the process conditions. In many cases an off-normal overview is presented on a separate display. Recent developments can be found in the ASM Guidelines for effective display design. Read more.
A CCTV-system is a human machine system, consisting of an observed reality, cameras, transmission, displays, image presentation, workplace(s), and cognitive information processing. CCTV is used in control centres for traffic supervision, tunnel safety, surveillance, security, and remote control.
Guidelines for CCTV information display are equal to those for simplifying process graphics or reducing alarm messages. The general guideline is: keep it simple and present no more images then needed to do the job. For example, if there is no traffic congestion expected (by night!), there is no need to show live images of almost empty highways; a black screen is ok.
However, engineering good CCTV-images is more complex, because image requirements can be achieved by different means. The camera locations, resolution, and lenses are a starting point. Next live streams have to be directed to the control centre, possible with a loss of quality. Images can be pre-processed before display (scaling, cropping), and finally the size and resolution of the display screen has an impact on image quality.
HF Guidelines on CCTV-system design are now available. Summaries can be found in several published articles. If you are interested in the full guideline document, please fill in the contact sheet.