A senior operator at a major plastics manufacturer summoned it up nicely when she said, We already know what the plant looks like, and we know exactly where things are located. Besides, a bunch of digital values up and down a multi-colored and highly detailed graphic arent much use to us because no one bothered to include a simple reference point.
The message is loud and clear: Every control room operators ability to remain vigilant and rapidly respond to abnormal situations is the direct result of his or her working environment and how much needed information is presented to them.
Acuites Nick Dinadis suggests evaluating existing operator graphics using the following criteria:
Content: Operators can only be effective if the operator interface provides them with the right information at the right time in a usable and logical manner. Often graphics are designed for normal operation and dont support abnormal situations, such as start-up or shutdown. Documenting the different graphics and keystrokes/point-and-clicks required during different operational phases can provide valuable insight into what graphic modifications are warranted.
Format: Even the best information is of little help to operators if it is not communicated as efficiently and reliably as possible. Everything from the appearance of meters and equipment to the use of colors and text must be consistently tailored for optimum usability. Recommendations include the use of a gray-scale color palette; reserving specific colorsi.e, yellow and redfor alarms; use of deviation bars; the use of advanced analytical graphics, such as multi-point spider webs (polar stars) driven by thirty to forty data points; and other intuitive health-at-a glance graphic elements.
Structure: The types and organization of graphic pages is critical to overall operator effectiveness. Based on industry- acknowledged best practices, the consistent organization of a multi-tiered graphics hierarchy is an important first step to providing operators with usable information and near-instant recognition of abnormalities. For example, Level 1 = overviews; Level 2 = task-oriented, major system overview and primary operating graphics; Level 3 = additional detail, similar to todays graphics; and Level 4 = non-control and help displays.
Processes, quality and production demands, and automation systems have changed dramatically during the past twenty years, so doesnt it make sense that control rooms designs should also change?
If air-traffic controllers require a well-designed, functional environment in order to maintain high levels of vigilance and situation awareness, why is it so difficult to think that process control operators dont require, in fact deserve, a similar working environment?
Dave Harrold is co-founder of the AFAB Group and a regular Control contributor.
Here are some additional resources to help you get started on your control room redesign.
Defining Operator Vigilance and Situation Awareness
26 Injured1995 Texaco Refinery in Milford Haven, Wales
Badly designed HMIs and alarming systems quickly can make a bad situation even worse. Analysis of this 1995 accident revealed the following:
The incident developed from its initial causative problems largely because of the combined effects of two factors.
Firstly, operators were not provided with information systems configured to help them identify the root cause of such problems The interface between the operators and the control system should have been designed to give the operators and manager overview facilities through the display.