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 User Solutions continued
Codifying Code
Standardizing the hardware served to simplify physical design efforts for subsequent projects,
both new and retrofit. However, the team wisely applied significant effort to software design as well. Specifying the AutomationDirect PLC and HMI fami- lies was just the first step. How those platforms were programmed would play a crucial role for imple- menting, deploying, and maintaining these projects.
Software programming and configurations are intangible compared to physical designs, and if the code is not arranged logically and documented thor- oughly it can be downright inscrutable to all but the original programmer. Helix’s first task was to define the PLC logic to reliably handle the basic functional needs of a general pump station.
The team then went to great lengths archi- tecting the logic so that a typical program could be used for different pump quantities, signal ranges, and even network technologies simply by making minor adjustments. Memory locations and I/O address assignments were also standardized to promote consistency from site to site.
HMI graphics development received the same level of attention. Standardizing the graphical objects made the configuration effort more efficient and consistent. In turn, the resulting screens are easier for operations personnel to use regardless at each of the pump stations.
With all the software design pieces coming together, the next step was testing to validate the entire concept.
The Big Picture
For a water utility like Helix, there is one main operational site and many distributed remote sites. Significant wired and wireless networking infrastructure is in place to bring all of this together into an integrated whole under a single SCADA umbrella. Each of the remote locations must be capable of operating locally as an “island” of
operation in case of communication failure, yet under normal circumstances they must integrate seamlessly.
Local control at any given site was straightforward. The first level of complication was ensuring that PLCs could communicate peer-to- peer, which was needed if a pumping PLC required information about a downstream tank level handled by another PLC. Because this communication impacted pump starting and stopping, it required the utmost reliability.
Another required attribute for the automation architecture was a centralized data collector PLC
at the main plant for monitoring system values, handling start/stop setpoints, logging other events like communication failures, and alarming on faults. This data collector would also support
more advanced systemwide functionality such as identifying time-of-use periods for shedding load during peak hours to reduce energy costs.
Knowing the necessary characteristics, Helix performed preliminary testing. They were able to individually prove out all basic communication, control, and visualization functionality, with the assistance of available documentation, online videos, and free support from AutomationDirect. This gave the team confidence that the pieces could be integrated into a whole as required.
This multi-tiered approach of local control, peer communications, and centralized data collection wasn’t deployed to the field in a single effort. Instead, careful benchtop testing was performed in advance to ensure the concept would perform as expected (Figure 3).
By assembling multiple PLCs configured as local stations, and networking them with a data collector PLC and each other, the team was able to simulate and pre-test all levels of control function- ality and communications to their satisfaction. HMI operation was also verified during the test phase. Extensive benchtop testing was key to ensuring success for initial and subsequent field installations.
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Editor's Note
New Product Focus
- Expaded communications and analog I/O capabilities for the
- Control cabinet cable entry systems
- DURApulse® GS20 Series high performance AC drives
- ProSense® Advanced Process Conrollers
- Enclosure Thermoelectric Coolers
Tech Thread
Improvies, Adapt, Overcome
Business Notes
Cover Story
The Best Automation HMIs Keep Things Simple
What's New
User Solutions
- Water Utility Successfully Standardizes Automation Practices
- Automating the Hendrick's Gin Grand Garnisher
Student Spotlight
CPAPs RE-INVENT ed into Ventilators Using PLCs & HMIs
Break Room
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 User Solutions | Issue 44
Brain Teasers

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