For a greenfield wastewater treatment facility currently starting up near Denver, the city's Metro Wastewater Reclamation District desired an advanced process automation system that could optimize operations and improve maintenance procedures while simultaneously meeting compliance objectives. They turned to engineering firm CH2M, which designed and implemented a virtualized PlantPAx system from Rockwell Automation to accomplish these goals.
John Costello, west regional technology lead-automation for CH2M, together with colleague Tyler Nading, water engineer, reviewed the facility's new productivity-enhancing automation environment at the Rockwell Automation Process Solutions User Group (PSUG) meeting that kicked off today in Chicago, leading up to Automation Fair later this week.
Mobile access, HMI best practices
The PlantPAx modern DCS platform not only streamlined engineering of the facility's control and instrumentation systems, but also leveraged mobile technology including ISA 18.2 standards for alarming and gray-scale graphics to give operators ready access to the information they'll need to efficiently operate and troubleshoot the new facility.
Over 60,000 tags and 6,000 alarms are monitored from an operations center that features a state-of-the-art video wall providing visibility to the entire 100-acre facility, Costello said. Further, secure mobile access via iPads allows operators to also monitor and control key processes from anywhere on the site.
The solution improves troubleshooting, predictive maintenance and operator effectiveness, while controlling the processing of nearly 30 million gallons per day (MGD) of wastewater with future expansion to 75 MGD.
From an architecture standpoint, the facility is designed for high availability, featuring a redundant control-level network firewalled by a demilitarized zone (DMZ) from the site's supervisory-level network where applications run in fully virtualized mode.
The system relies extensively on digital field network rings connecting some 1,400 smart devices. Between the redundant controller networks and device-level Ethernet rings (which by nature include an inherent level of fault tolerance), the system is designed to resist any process interruption due to network failure.
"It's really hard to take down the facility," Costello said.
Also included are some 550 hardwired I/O and 13 vendor skids, 12 of which are based on Rockwell Automation controller technology and could be readily and fully integrated into the PlantPAx architecture.
Control code tested via simulation
The development team made use of CH2M's Replica software to dynamically simulate the plant's hydraulic behavior, including simulation of control strategies, according to Nading.
"The differentiator with this software is that we also have controls capability; we simulate not just pump but motor, not just tank but level indicator," he said.
From a practical perspective, this allowed designers to test unique control algorithms in simulation, implement those algorithms in the PlantPAx system, then run the code as implemented against the Replica simulator to ensure everything worked as expected prior to start-up.
"We could even take math directly out of the simulation and place it in the controller logic," Nading added.
During the procurement, installation and commissioning phases of the project, FactoryTalk AssetCentre software from Rockwell Automation was used to provide version control of automation applications, and has assisted in configuration and troubleshooting of HART- and Profibus-based smart instruments.
And as operations ramp up, "AssetCentre will give them the ability to schedule manage, track and report on field calibration activities," Costello said.
Of particular value during instrument configuration and commissioning was AssetCentre's Process Device Configurator tool, which automates many manual tasks. "The amount of time that this tool saved us was astronomical," Costello said, estimating a 40% time savings in configuration and commissioning.
Mobile access, alarm management
Finally, the design team was able to bring state-of-the-art mobile operator access and alarm management strategies to bear using PlantPAx tools. For example, a modified version of the ISA 18.2 guidelines for best practices in operator graphics was used in order to accommodate the unique requirements of the plant's mobile access philosophy. (Dialogues and drilldowns were modified to better suit the iPad's touchscreen interface and form factor.)
Alarm strategies were designed and implemented to take advantage of alarm shelving capabilities, which at the time the configuration was developed were due to be included in the next PlantPAx release.
"They've since worked seamlessly," Costello said. Other alarm management best practices included the use of a consistent symbology to differentiate priority among alarms, and the isolation of root-cause alarms to prevent associated cascades.
Finally, the design team implemented the alarm KPI reports in FactoryTalk VantagePointEMI in order to provide ongoing alarm management and mitigation guidance, for instance, by grouping alarms by class and by hourly alarm frequency. "If you don't know what the most frequent alarms are," said Costello, "you don't know how to start reducing them."