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Case Study: Migration Boosts Batch Operations

June 23, 2009
New control system improves consistency and halves batch creation time.

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.


Outdated Controls
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.

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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.

To help improve batch-to-batch consistency and reduce manual adjustments, the system incorporates FactoryTalk Batch recipe management software. This can build signature templates and enforce command-verification policies, which improves productivity and the company’s security and regulatory compliance efforts. The software is much simpler to use than the prior system and allows programming batch recipes into the machinery and automatic exact execution of instructions. The improved functionality makes a dramatic difference in the quality of product as well as in overall productivity.

Integrated into the PlantPAx system, communications interface applications allow users to get required data from the plant floor. This enables Arkema engineers and Precision Engineering technicians to gather production data from other applications and optimize communications with the controller. A Rockwell Automation Encompass Partner, Salem Automation, also played a key integration role with its ABNet software interface module. This device allows the new control system to interface via EtherNet/IP with the remaining DCS.

The Rockwell Automation technical support team provided training for line workers and engineers, helping them become acclimated to the new system and teaching them how to leverage the new automation features. Included with the technical support, Rockwell Automation led Arkema through its well-defined and strategic technology migration path.

Impressive Results
The team finished phase one of the migration (replacing the control system, HMI and I/O), in July 2008, well within the necessary six-month window. The new system has experienced zero downtime since becoming operational, yielding annual savings of over $500,000. Also, the plant achieved full production during week one, several weeks earlier than expected.

Batch creation time has been cut in half. The automation system’s engineering tools allowed recipe and batch management to move from control engineers to the production engineering team. This makes procedures a lot quicker if the team wants to add a new product to the line. Now, a production engineer can complete all batch changes and new product additions without having to involve a control engineer. Any small recipe errors found can be fixed immediately for the next batch.

Batch consistency also has improved. Data monitoring spurs greater uniformity in both the control recipe and procedure — and also lowers safety risks. A production engineer can modify procedures and load recipes at the same time while keeping everything synched. Arkema constantly can pilot new grades and make changes at a moment’s notice to the batch. In fact, the company has added two products to its portfolio since the new system has been installed. This would have been nearly impossible with the old system.

Having batch programming done outside the controller has enhanced operator ease-of-use, as well. Changes are much easier and safer than the previous system would allow. Additionally, the ISA-S88-compliant platform lets all operators view batch control elements like temperature and pressure, making it easier for them to maintain consistent and safe production.

Phase two of the migration project — in the facility’s impact modifier production facility — was implemented during the two last weeks of April 2009. Startup and commissioning of the PlantPAx process automation system were flawless. The facility immediately achieved full capacity rates with no safety, environmental or productivity issues. Due to the enormous success of this project, Arkema is developing plans to upgrade the wastewater treatment unit at Axis utilizing the same migration strategy.

John Bryant is engineering and maintenance manager for Arkema in Axis, Ala. Mike Vernak is program manager, DCS migrations, for Rockwell Automation, Mayfield Heights, Ohio. E-mail them at [email protected] and [email protected].

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