A High Performance HMI enables an operator to safely and effectively monitor and manage a processing plant. It is based upon best practices for the display of information conforming to known human factors issues and the proper principles for abnormal situation management. The HMI is the operator’s window to the process and is a critical element for operations effectiveness.
Several specific practices exist to make a High Performance HMI possible. These are covered thoroughly in the later parts of this book. This chapter is a high level overview of the principles and work processes.
1 Bring Back the Big Picture
With the older control walls, experienced operators could use pattern recognition techniques to quickly ascertain the overall health of the process. Most values were trended. Abnormal event detection could be quite fast. During a major upset, everyone in the control room could easily see the status of the plant in one view by examining the wall-mounted instrument panel.
With the DCS, managers, engineers, and outside operators often have to question the console operator to learn the plant status (or worse, “take over” some of the screens and begin calling up other displays). During abnormal situations, this is an unnecessary distraction which only adds stress to an already stressful situation.
An optimal solution for all is the introduction of large, off-workstation Process Overview displays, configured to show a proper summary view of the process. Situation awareness is greatly increased by the usage of such overview displays. With these, the entire operating team always has a clear view of key process conditions. Typically, 50 inch and larger computer video displays are used, with larger sizes becoming more practical and less expensive. However, such possible large sizes as shown in Figure 1 are not necessary.,
Figure 1: An “Over-the-Top” Overview Display
Projection Display System picture courtesy of BARCO, www.barco.com
2 Create Hierarchical, Scenario-Based Displays to Improve Situation Awareness and Response
Situation Awareness is an accurate and timely understanding of the condition and behavior of the process. Proper display design should support situation awareness and encourage proper operating practices.
Four distinct levels of displays should be used, incorporating the principle of progressive exposure of detailed data. These are:
Level 1 – Process Area Overview (for situation awareness)
Level 2 – Process Unit Control (for ongoing process manipulation)
Level 3 – Process Unit Detail (for close, detailed examination)
Level 4 – Process Unit Support and Diagnostic Displays (for troubleshooting)
When P&IDs are used as the simplistic basis for graphic design, a proper graphic hierarchy will not result. P&IDs are a totally “flat” form of depicting the process. For control purposes and proper abnormal situation handling, the displays should enable “drill-down” for increased level of detail.
Proper displays for running a process in a normal situation will likely not contain the right information for handling an abnormal situation. Additionally, there should be displays specifically designed to address upset conditions, as well as certain routine activities such as mode or product transitions.
3 Redesign Displays to Emphasize the Most Important Information
Display design and style has a significant impact on the speed and accuracy of operators’ interactions with a display. Meaningless (yet common) misuse of color, animation, and flashing lights are an impediment to easy and early recognition of a significant event. Our knowledge of human factors has increased greatly since the introduction of the DCS, yet display design has not generally incorporated this knowledge.
Proper design schemes increase the ability of operators to distinguish different conditions, recognize important information, and respond to abnormal plant conditions. Improper design slows response times and contributes to errors in perception and comprehension.
Traditional displays are usually far too cluttered and covered with numeric data. The operator needs information (data in context made useful) to operate in a high performance manner. Proper presentation of information in innovative ways will significantly enhance the operator’s situation awareness and ability to deal with abnormal situations.
Some characteristics and contents of High Performance displays are as follows:
Gray backgrounds are used to minimize glare, along with a generally low-contrast depiction.
No gratuitous animation, such as spinning agitators or pumps, moving conveyors, and splashing liquids and sprayers. Animation should be limited and only used to highlight abnormal situations.
Depiction of process values is made in the context of information, rather than as simple numbers on a screen.
Important information and key performance indicators have embedded trends.
There is very limited use of color. Alarm colors are used only to display alarms and nothing else.
Equipment is depicted in a simple 2-D low-contrast manner, rather than brightly colored 3-D vessels with shadowing.
Layout is generally consistent with the operator’s mental model of the process.
Navigation methods are logical and consistent.
A hierarchical structure supports progressive exposure of detailed information.
Display access requires a minimum number of operator keystroke actions.
Techniques are used to minimize the possibility of operator mistakes, as well as provide validation and security measures.
Display elements have consistent visual and color coding.
4 Employ Proper Control Room and Physical Console Design
It is a common situation to find especially poor design of the operator’s workspace. The quantity of physical screens, their layout, and the correct access to communication tools greatly affects the ability of the operator to function effectively. Imagine if an aircraft pilot had to leave his seat to use the radio! Equivalent situations are not uncommon for process operators.
Proper design of the control room and the operator console is essential to operator alertness and situation awareness. Factors to be considered in control room and console design are detailed in later chapters. They include:
Comfort factors, such as lighting, temperature, noise, and traffic
Number, type, and arrangement of screens and keyboards per specific console
Console heights, adjacency, and similar ergonomic factors
Support equipment (radio, intercom, phone, switches, etc.)
5 Minimize Distractions in the Control Room
Console operators need an environment free of distractions, especially at times when the unit is in a transition or an abnormal situation. For example, maintenance scheduling and management activities should not share the control room.
It is a poor practice to see engineers, supervisors, managers, and maintenance technicians accumulating behind the console and calling up various displays. Distractions are a major problem for operators.
Control and production engineers should have their own workstation, clearly distinct from the console operators. By policy or by control room design, maintain a separation between the console operator and everyone else during unit upsets. Give engineers and managers access to information through large screen displays, separate workstations, or a situation/conference room located just off the control room. With support people close by, the operator can ask for help if needed and still maintain a sense of control over the work environment – an important stress management technique.
6 Seven Steps for Creating a High Performance HMI
The following steps are optimum for transforming a traditional HMI into a High Performance HMI. They are also easily adaptable for creation of a new HMI for an entirely new facility.
Step 1: Adopt a High Performance HMI Philosophy and Style Guide
Step 2: Assess and benchmark existing graphics against the HMI Philosophy
Step 3: Determine specific performance and goal objectives for the control of the process, for all modes of operation
Step 4: Perform task analysis to determine the control manipulations needed to achieve the performance and goal objectives
Step 5: Design and build high performance graphics, using the design principles in the HMI Philosophy and elements from the Style Guide, to address the identified tasks
Step 6: Install, commission, and provide training on the new HMI
Step 7: Control, maintain, and periodically reassess the HMI performance
Each of these steps will be covered thoroughly in later chapters.