Shortly after starting full time at ProSys, I became involved in a Human Machine Interface (HMI) Re-Design project which included the production of advanced Operator graphics. I quickly learned that the HMI at plants provides more than just a detailed view of the plant. If done properly, the graphics should provide an advanced warning that there is a deviation in the process, whether planned or unplanned. The process to making an effective HMI involves many different stages before the design is complete.
Steps to Designing an Efficient HMI
- Reviewing the Process: looking through current graphics to see what equipment is involved and begin to understand the flow of the process.
- Initial Meeting with Team: discuss how they view the process to help decide what pieces of equipment are viewed together.
- Breaking Equipment into Logical Systems: information from the initial meeting is used to decide what equipment will be placed together on a graphic.
- Critical Process Variable Selection: going through tags and deciding which ones provide the best leading indications of process deviations. Many considerations are taken here, including mass and energy balances and Operator action logs.
- Team Review of Displays: a meeting with Operations, Controls, and Process to make sure the process is adequately covered, and all the main process variables needed for control and monitoring are on the graphic. Also, to review the layout to make sure piping and tag locations are correct.
- Installation: the graphics are placed on one or multiple consoles for review on the live system. Often, using the graphics live will lead to small changes that were not thought of during the review meeting.
- Implementation: once reviewed on the live system, the design can be pushed out to all of the consoles.
During this project, I learned that there shouldn’t just be one level of graphic, with the same amount of detail on each one. Yes, there should be graphics that mimic/match the P&IDs, but these should not be the only ones. These detailed graphics can become cluttered due to the amount of piping and instrumentation needed to provide a complete view of the process. Higher level graphics provide a larger view of the process, and include multiple pieces of related equipment. They are developed to provide enough information to warn of a potential issue, and provide some tools/handles to mitigate the issue. The detailed displays will be able to be navigated to for additional diagnostics and further identification of issues.
Also, during the project, I was exposed to multiple shapes ProSys created to enhance the Operator graphics. The use of these shapes provides the Operator at a glance monitoring capability. The shapes allow for ease of identifying process deviations and ease of navigating to displays.
I have come a long way in understanding the importance of an effective HMI. There is not just one right way to layout a graphic, and more detail is not always a good thing. If done properly, Operations should be able to spend most of their time on an Overview type graphic. Operations should use leading indications to determine if there is an issue, and have an intuitive navigation system in order to easily drill down to the detail display to investigate issues further. Specific displays can be created for known alternate modes of operation to decrease the amount of movement from graphic to graphic. Multiple tools are also available to enhance the Operator’s awareness of what is going on in the process. Overall, a well-designed HMI can play a major role in effective plant operations.