Control systems are built to last for decades of reliable operation. Yet technology continues to advance at a rapid pace. At the recent Emerson Exchange conference in Texas, Emerson’s Jean Pressly presented To Migrate Or Not To Migrate—DCS HMI Only. Here is a recap of the main points of that presentation.
Jean discussed reasons customers may consider human machine interface (HMI) migration, including obsolescence, “at the glass” consolidation of operator view to various devices such as PLC’s, and first step toward full controls migration. These initiatives all intend to address certain risks, such as loss of view to the process due to failure of an unsupported hardware or operating system platform.
While addressing such risk may provide a short-term fix, what type of impact does an HMI solution have in the longer term?
On the upside, HMI migration can save your view to the process. On the downside, it costs a significant amount and does not enhance your ability to improve process operations significantly enough to impact your bottom line results. HMI migration typically introduces a temporary bridge solution that is a hybrid of newer system technologies integrated with legacy system network devices and interface software. Maintaining such a hybrid HMI solution requires know-how on multiple platforms. To make changes (add/remove instruments and devices) requires opening at least two software configuration environments. Troubleshooting may therefore be more complex.
Installing a newer HMI solution can provide a sense of relief about keeping an eye on the process. However, let’s be clear that installing and using this solution does introduce new risks.
So, before you make that move, please consider examining the overall costs and benefits for the longer term. Take a look at your site: How well is the plant currently performing? Where is there room for improvement? Does the current control infrastructure help or hinder problem solving? Getting these questions answered takes time and effort. One recommendation is to engage a knowledgeable consultant who can work with you and other site personnel to gather all the information needed to develop and deliver a report that details scope of work, costs, benefits that can be achieved through automation investments.
This diagram depicts the study process, which has been proven many times:
For small- and large-scale sites, developing a plan for controls migration allows clients with aging legacy systems to make informed choices about how, when and why to modernize automation equipment.