FIELDBUS TECHNOLOGIES, even the simple ones such as HART, make several orders of magnitude more data available to today’s modern control systems than was possible in the past with traditional analog systems where people could through “programming” of the field device force it to fail either high at 20+ mA or low at 3.8 mA for certain types of faults.
Of course, this feature was not always available with Intrinsically Safe installations because of their power limitations, but it could be done in most cases. Despite the fact that we have been using HART technology on a widespread basis for over 10 years, and Fieldbus technology has been around for over 10 years, though only widely deployed this decade, few facilities are able to use this information for a number of reasons including the fact that most HART based control systems until recently were not able to use the available diagnostic information without the addition of a parallel system to “strip” the signal off and forward it to a set of dedicated servers did not help the situation. Fieldbus systems have been using the status information since they have been available to manage the regulatory control loop, sometimes to the chagrin of engineers and operators who were not aware of this.
Of course, this only gets the information to the control layer of the enterprise and the real value in the data is in combining it with the business systems to better manage not only the process but also scheduled outages, maintenance, batches and recipes, (Yes, you can re-range smart devices to match a new recipe) and market pricing to maximize the return on a facilities capital assets. However to make all this happen will require development of standards to define not only how the data is to be exchanged across the layers but also the format and meaning or content of that data. This is the real challenge, because now we must work with the Information Technology people such as the SAP, Oracle and other Enterprise Resource Planning (ERP) providers to “create” a common dictionary we all can use to define what each term and data point means.
Do you have to wait until these standards and dictionaries are defined before realizing at least some of the benefits of today’s fieldbus systems? No. Will the integration be harder than you initially guess? Yes, just like most other complex I.T. projects the scope is often bigger than originally thought. However, the prize is great with some companies reporting a 20% reduction in maintenance costs from getting it right.
Of course, you can always start small and simply double your information from the single Process Variable (PV) measurement received today and use the Status signal for better control by incorporating this information into your control algorithm logic so that you are guaranteed to be only using valid signals and information to make changes to your process and if the status changes from good to “Uncertain” or “Out of Service” you will know the device needs maintenance and assuming you do not yet have an integrated, automated Computer Maintenance System in place, the Operator can then cut the necessary work order so that at least your technicians are only working on real problems rather than chasing suspected false readings as is often the case today.
ISA 2005 will be as good a place as any to start resolving the above issues and working with industry to insure that the necessary standards are in place to integrate this information with the higher levels of the enterprise. ISA-95 is a good template to describe the process to be used, what is needed now and where ISA has traditionally excelled is in the “how to make it work” piece of the puzzle. I hope that in the near future when we are all “information moguls” that we will look back on these times with a hazy fuzziness associated with the “good old days” when things were simpler and recall how easy it was to be a “data dummy” but at what a high cost.
|About the Author|