VOL 18 ISSUE #2
Developed with customers in mind, PMIII is Astec’s newest plant control system.
PM96 system overview
PM96 system overview
PMII system overview
PMII system overview

From burners to silos, from motors to drums, each component of a hot-mix production plant can either be a trusted collaborator in increasing the plant's efficiency or—with access to timely information or ability to fine-tune its operation—a frustrating adversary to a plant's capability. The main way plant operators and managers interact with the full range of their plant's production process is through the plant control system.

The human element—how comfortable users are with this system—is often as important as its technical aspects in determining how efficiently a control system works within the plant. Over the years, the designers and engineers at Astec Controls have looked at how plants use their various control systems and developed answers based on real-world demands. Their latest design, called the PMIII, has just been introduced and is earning praise from customers as a responsive and intuitive system for today's hot-mix production.

Laying the Foundation

Of Astec's legacy systems, the PM96—commemorating the year of its release, 1996—was an early version of a single-bore or multi-bore control system. It provided reliable service for hot-mix plants throughout America for years. However, with new technology came changing expectations. Operators were pleased with the PM96's ability but as more demands were put on the system, newer controls would need to be integrated as well.

New Expectations

The next generation release, the PMII, was designed to be its replacement. It maintained the same level of control but replaced the PM96's specialized user-interface with a standard PC terminal, which relied on a so-called soft PLC and ran in Windows. The benefits to the plant's machinery were the same, but the benefits to operators were exponentially improved: necessary training time decreased, plant control increased.

Just before the release of the PMII, Astec released the TCII, a highly automated and exceedingly detailed plant control system. "This is the Cadillac of control systems," said Al Williams, one of Astec's senior control engineers and head of the Industrial Control Group. Williams has over three decades' experience with Astec's asphalt control systems and has seen many of them put to the test—and pass with flying colors. "With a system like the TCII, for example," he explained, "it can do whatever a plant operator needs. It's almost as if, if something has an on/off switch, the TCII can automate it."

PMIII system overview
PMIII system overview
PMIII burner controls
PMIII burner controls
PMIII silo controls
PMIII silo controls

Learning by Doing

The TCII's chief advantage over earlier systems is its capacity to learn and communicate with smart motors, variable frequency drives (VFDs), and other equipment. In addition to allowing operators easy manual control options and automated operations within preset limits, the TCII records and reports information about the plant's efficiency from various points within the hot-mix production process. Thus, the TCII allows operators to use that information in realtime, establishing a more responsive and productive control system.

However, not every plant requires that level of intricate data-management. Also, for some plants, a system like the TCII might be their ideal model, but perhaps management has not allocated enough resources to afford a "Cadillac" control system. With those customers' needs in mind, Astec Controls developed their latest version of plant control systems—the streamlined PMIII.

Made With Customers in Mind

Developed by Astec's in-house controls engineers, the PMIII is a PLC-based control system comprised of separate modules for burners, silos, motor controls, and blending and loadout. With these features, the PMIII can be as robust or as simplified as plant operators desire. Williams noted, "Customers can purchase CPUs for each part of the plant or just one for the motor or the burner. If someone out there still wants to use the old PM96 push-button control panel for one part of the plant, that customer can still install PMIII modules everywhere else." The PMIII's modules can be installed individually to specify the options to a unique asphalt facility or they can be installed together as a package, similar to the TCII.

Some plant operators complain of "information overload" in competing control systems. With that in mind Astec updated the PMIII user interface to rely on minimal graphics on each screen, reducing distraction and increasing an operator's ability to find information with speed and clarity. Also, even though each individual screen may appear simple, the PMIII retains the ability to drill down for more information. This layered approach to data management allows the PMIII to provide abundant information that an operator may need without overwhelming users.

Lastly, the PMIII's built-in diagnostics reduce plant downtime, helping operators probe for the source of any problems along the production line. Also, the system's improved reporting makes a greater variety of data available, which will assist management in long-term plant decisions.

"Instead of just sending a signal to start or stop, the PMIII can read current on motors," Williams added. "This is normally a feature you would only find on a larger, more expansive control system. Now that a more streamlined system can provide this level of data, more and more plants will have a level of control they never thought possible."

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