Five key considerations for improving HMI graphics during a control system migration
Performing thorough back engineering
One of the most difficult things about using existing graphics from older control systems as the design basis for new graphics is accurately estimating the complexity. Often, it is not feasible to go through each graphic in detail during the early stages of a migration project when the estimate is developed, or as part of the bid process. In many older control system graphics, dynamic functionality requires scripting or logic functionality programming. For instance, to change pump colors with run and stop status changes in many legacy control systems requires coding or scripting in some vendor programming language. This background scripting, which can be extensive and complex, is not evident when just looking at the static graphic, or even in performing a surface review of the graphic. While much of this functionality is now easier to configure in newer control systems, the back engineering process can be time consuming.
Back engineering involves reviewing the scripting in older graphics to develop a complete understanding, so that the dynamic functionality can be accurately built into the new screens. Scripting or additional functionality that is not identified during the scoping stage of the project may lead to more configuration effort during project execution than originally planned. If your existing graphics will be the design basis for the new ones, then it is essential that you allocate time at some early stage of the project to do a complete back engineering of the graphics. This will ensure that you fully understand the scope of functionality required in the new system and estimate accordingly.
Involving operations throughout the process
The primary users of graphics are operators, so it is essential that the operations department be actively involved in the graphics design and development process, if the graphics are to be effective. They should be involved from the early stages of the migration project, providing input for the graphics design guide and going on to play a role in the actual design and development. Finally, operators should be central to the graphics testing, review, and approval processes.
The way that organizations involve operations in the process varies greatly. In ideal circumstances, organizations might have an operator, or possibly several, actually design and build graphics. This can improve their practical usability because operators will bring a unique and practical perspective to the process. An added benefit is that it generally speeds time to acceptance by other operators because those responsible for graphics development will help promote acceptance of the new control system to their counterparts. Unfortunately, in many organizations, the time requirements needed for complete graphics development make it impractical to have operators wholly committed to these tasks. When this is the case, an alternative is to have a team of operators who regularly consult with the engineering team developing graphics to provide input for key graphics-related decisions.
As graphics move from development to testing, review, and approval, operations should be centrally involved in all of these efforts. For example, having operators participate in the factory acceptance test is a great way to gain valuable feedback about the operability of your graphics, while also increasing the comfort level of the operators with the new system.
Clearly defining the review and approval process
My experiences as an end-user, system integrator, and vendor have taught me that many times, companies do not have a clear vision or consensus when it comes to graphics. This translates to scope changes, cost overruns, and schedule delays, leading to frustration on everyone’s part. Ask several people and you will likely get a variety of answers regarding what they want to see on the screens. To manage this reality effectively, it is important to have a clearly defined graphics review and approval process that specifies who reviews and approves graphics, when in the process that review takes place, and how much time is allocated to the review and feedback cycle.
One approach that is often employed is to build a few sample graphics and get approval for them, subsequently using them as the templates going ahead. The templates shift major changes to the front-end of the project by allowing for early review of basic items, such as general layout, color usage, and equipment and instrument symbols. This approach also minimizes the replication of issues on individual graphics that will later need to be changed.
It’s never too soon to plan
HMI graphics are a substantial challenge on control system migration projects. The initial decisions of how much to change graphics and whether to use conversion tools or start from scratch are complex. The key driver in the decision process should be determining what approach will give you the most benefits from the new control system, and thoroughly defining graphics needs can help mitigate the risks. This involves complete back engineering of graphics in the old control system to fully understand the existing operating capabilities. It also requires up-front planning using tools like a comprehensive graphics design guide and a graphics inventory and complexity spreadsheet. Involving operations throughout the graphics development process is essential to reducing back-end changes, while also increasing the comfort level and satisfaction with the new system among operators. Finally, clearly defining the graphics review and approval process can prevent individual preferences and ongoing changes from derailing your project.
Daniel Roessler is author of Control System Migrations: A Practical Project Management Handbook (Momentum Press 2013) and an owner of DANR Consulting.
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- HMI graphics can be a major element of a larger DCS migration, but can be overshadowed by other concerns.
- Careful functional evaluation can help avoid confusing operators with new screens while gaining functionality of the new control system.
- Planning following these five steps can smooth out the process.