Programmable Logic Controller (PLC) service in process industries began as an alternative to hardwired relay, systems for sequencing controls and safety systems. PLC usage increased with the addition of analog control capability. As Original Equipment Manufacturers (OEM’s) adapted skid based equipment to include pre-engineered PLC’s, this convenient equipment and controls combination propagated rapidly.
Sites implementing skids from different OEM suppliers may have an array of PLC models with various control, Human Machine Interface (HMI), alarm, and historian packages. Upgrading such PLC’s tends to be cost prohibitive, as OEM PLC’s typically have minimum control and data capabilities to meet a price point.
Thousands of PLC’s are approaching 100,000 hours in service, over 11 years of continuous operation. Beyond this age, higher failure rates are likely and replacement parts availability is declining. PLC replacement in kind will likely add a second control platform, which includes separate controller and HMI databases. Whereas, modernizing with a new automation system, such as the DeltaV™ system consolidates configuration of the HMI and controllers in a single database. Other advantages include data integration, asset management, advanced controls, and improved diagnostics.
This paper examines techniques for PLC to DeltaV system modernization through integration or migration. Integration refers to a physical connection and software application for passing data between your older PLC and a new DeltaV system. Migration implies removing functionality from your PLC based system and implementing it in a new DeltaV system. Solutions may combine integration and migration. For example, one may migrate critical PLC shutdown logic into a new DeltaV SIS application, and for non-critical plant areas, integrate PLC I/O with DeltaV controllers.