Arkema makes chemicals that add strength and life to many materials used to build our homes. Its Axis, Ala., facility specializes in producing impact modifiers for polyvinyl chloride that goes into, e.g., siding, window profiles and pipe.
To create impact modifiers, Arkema uses a batch reactor to produce a liquid latex material. This then goes to a continuous spray dryer where it’s dried into a powder, the final product.
The batch development process averages eight hours/cycle with a completed batch time of 12.5 hours. The Axis facility produces 35,000 pounds in that time frame — or about 85 million pounds/year of 15 different impact modifiers.
Arkema was running half of its plant on a 28-year-old legacy distributed control system (DCS) and the other half on a 15-year-old version of the same system. Finding replacement parts was a challenge, and obtaining talent to repair any breakdowns was nearly impossible. Added to this, the site’s input/output (I/O) hardware was almost 30 years old.
Whenever a standard process update or recipe change needed to be made to the system, the plant would have to shut down for 10 hours. This situation was occurring almost once a month, costing the company approximately $42,000 each time. Sporadic failures added to the tab.
Even more importantly, safety concerns were starting to crop up. The plant experienced a few potentially critical incidents stemming from aging I/O hardware and the overburdened control systems. Because the legacy systems lacked condition-monitoring capabilities, plant personnel weren’t alerted to problems until it was too late.
It only would have been a matter of time before the plant was non-operational, Arkema realized. So, it decided to replace the control system with one that would afford needed safety-monitoring capabilities and allow the company to meet additional market demands.
The company wanted a fully integrated system that would provide complex batch and recipe capabilities, solving the quality and consistency issues that had dogged the legacy DCS. It also was important that the new installation be user-friendly. Another priority was the ability to interface with the old DCS until migration was complete. Other requirements included compliance with the ISA S88 batch standard, use of the existing I/O footprint and, of course, minimal downtime during the system switchover.
Arkema opted for the PlantPAx process automation system from Rockwell Automation. The PlantPAx platform is based on the Rockwell Automation Integrated Architecture system, which delivers a unified process and discrete solution.
Working with Precision Engineering, a system integrator, and Rockwell Automation, Arkema created a migration plan that would accommodate all the company’s priorities. The process automation platform incorporates control technology, human/machine interface (HMI) software for visualization into each application, batch management software to control recipes, and communications interface applications to link the systems together and provide for third-party access.
The New System
The system centers on the Allen-Bradley ControlLogix programmable automation controller (PAC), which provides a fully integrated, scalable platform that can be used throughout Arkema’s plant and with its enterprise-wide information technology system. Unlike conventional controllers, ControlLogix PACs offer multi-disciplined control leveraging development tools, network protocol and service-oriented architecture.