HMIs evolve in process control

Other industries, such as the nuclear field, have good guidelines for HMI developers, and many of these are directly relevant to the process industry. Likewise, ISA has produced recommended practices for Fossil Fuels on HCI and task analysis, which appeared in the organization's RP 77.60.05-2001 report, "Fossil Fuel Power Plant HMI Task Analysis."

In fact, the latest recommended practices for developing graphics includes starting with, not just a task analysis as was done 50 years ago for the control panel layout, but more in-depth analysis using a variety of techniques. These formats include:

• Hierarchical task analysis
• Tabular task analysis
• Timeline analysis
• Link analysis diagram
• Human error analysis tabular

Better Graphics
Some of the latest practices associated with HCI development directly address these human factor issues by first providing a good graphic style guide. Many of these practices are identified in the EEMUA 201 document.

The background of HMI graphics also has changed from the traditional black to a grey background to mitigate glare. Most lighting schemes will produce glare and contrast issues when first delivered through glass VDUs. This problem was dramatically reduced as technology changes allowed LCD screens to be implemented. Black backgrounds facilitated operators turning the control room lights out, but use of multiple bright colors on these black backgrounds added to their complexity.

Graphics also have become easier to read as developers moved to brighter grey backgrounds, and reduced use of added colors by using high and low-intensity hues. Glare and reflection were reduced, but potential problems can still arise. Moving to brighter background color can introduce new problems if a control room’s lights are still turned out. Ideally, the control room should be designed to facilitate operator vigilance, especially with 12 hour shifts, by illuminating the control room between 500 and 800 LUX.

As mentioned above, the practice of using grey on grey for lines and vessels has allowed developers to put the fixed information into the background of the graphic, and place the variable information in the foreground.

Reserving colors and limiting color adoption in the graphic enables easier identification of off-normal or abnormal operation using grey on grey as normal and color as an attention getter. When a high-priority alarm annunciates on these displays, it becomes very visible on the graphic. And when the alarm is acknowledged, the color intensity is reduced to half, making the alarm still visible, but not the highest attention. This allows priority to become part of the graphic design.

Some investigations have been done about using graphical analog instruments, rather than just using digital numbers. Level and flow gauges are easier to read and make estimates of than relying on purely digital information. The aircraft industry mixes digital and analog data to provide good situational awareness, and uses analog indicators and accuracy where needed with its digital data. These new graphic systems use objects to represent mathematical solutions, such as mass energy balance and polar star techniques to represent change, and how it impacts other physical variables. This provides a better understanding of how to correct problems.

The technology now allows integration of information outside the DCS, such as Microsoft Word and Excel documents to be integrated into the graphic. By using pull-down menus, one of these IT based documents can be launched to provide calculations, lookup tables, procedures, and diagnostic information. This may include alarm information, stating the purpose for the alarm, typical problems that initiate the alarm, what corrective action is expected, consequences of no action, and other supporting information that would be useful to the operator.

As the HMI or HCI world continues to change, we have the power, but we need the discipline and knowledge of how to use this technology. We need to recognize that the problem we’re solving is called “situation awareness,” and alarms, trends and graphics are an integral part of the awareness solution.

This solution requires a true overview display, one that allows operators to monitor the important equipment within their scope of control, and provides clear indication of the highest level of alarms. The display needs to provide production information that will help the operator monitor the most important key performance indications (KPIs). Some solutions may include a graphical bar chart showing normal, the ± off-normal indication, and relevant alarm data.

The graphic system of the future will have trending embedded into the displays, operators again will use trends to predict off-normal, and they’ll be less dependent on alarms. The new system will exploit new navigation techniques, such as hierarchical navigation, which moves from overview to unit view to detail view, and finally down to diagnostic views and controller change zones. This form of navigation allows use of yoking techniques. This will allow automatic screen setup based on selecting a point, and populating the other displays with the relevant information associated with that point from overview to unit to detail to trend and alarm data.

Recent graphic projects also have exploited large overview screens and video walls, which reduce the amount of glass required at the console, and can significantly reduce the cost of the console because fewer workstations are required.

Another anomaly with HCI development is that graphics should be developed before the console, and the console should be developed before the control room. Unfortunately, we do this in reverse order, which causes problems with the flow and concentration of information.

Consequently, the future of the process industry should be driven by standards organizations such as ISA. Industry needs to free up and encourage engineers to address this topic. Research should be done first to identify what has worked well during this evolutionary process, looking back at how operators and supervisors used the panel, as well as how operators adapted to group displays and the new transition to cool graphics that provide good situation awareness. As an industry, we also need understand the research and knowledge that the nuclear, fossil fuels and aircraft industry have identified as best practices in HMI development.

The final solution will not be driven by operators or control engineers, but by a management team that understands the issues with the existing culture, is brave enough to follow the leaders in industry, and invest in good task management and up-front project loading. Investment is needed in graphical style guidelines suitable for all DCS vendors systems and project-specific requirement specifications.  This specification is a how-to guide to implementing the style guide on a specific system and/or project. Investment in graphical object libraries is also required to provide more than traditional valve, pump, and compressor objects, so the new systems will have diagnostic modules that help the operator understand more advanced information, such as material mass and volumetric balance.

Driving human error out of systems and improving safe work practices is a management responsibility, but so far management still lacks knowledge and experience to prevent those errors. They have a poor understanding of human factors, and are complacent to the needs of their operators. The control engineer can do a service to his company by raising awareness of this topic at the highest levels in an organization, and pursuing best practices on the control system upgrade projects.

Ian Nimmo, PE, IEng, MIET (CEI)