Have you ever struggled with the need to make technology upgrades while minimizing risk, avoiding plant shutdowns and maximizing return on investment? If so, you’re not alone. Hill’s Pet Nutrition recognized a need to upgrade its existing I/O system in 2006 at its Kentucky plant to eliminate periodic failures involving the analog inputs. The company implemented control technology based on the Allen-Bradley ControlLogix programmable automation controller (PAC) from Rockwell Automation with little downtime. The technology migration also helped eliminate I/O failures and streamline software programming.

Founded more than 50 years ago by a veterinarian, Hill’s pet food products are available in 86 countries, with sales of more than $1 billion. The company has more than 150 veterinarians, nutritionists and food scientists on staff.

The periodic failures involving the analog inputs meant maintenance would have to go out to the I/O rack, unplug the card and reconnect it so that the module would start working again.

“All of our process control for the extruder line is communicated through the analog input, so when that communication fails, it essentially shuts down the process,” says Shane Simmons, systems engineer at Hill’s Pet Nutrition. “Once the extruder line shuts down, it can take up to an hour-and-a-half to reconfigure the system and bring the process back online.”

In addition, finding replacement cards was becoming more difficult because the vendor was no longer making them. The only other option was to have them repaired, potentially adding delays and cost.

Hill also was concerned about disparate controllers on its raw materials, extrusion and packaging lines as well as dual controllers on its batching line used to maintain a tight tolerance on its ingredient mixing process. Unreliable service, declining operator knowledge, and increasing maintenance and support costs were pointing to a strong case for a control system migration.

“With the ongoing reliability issues from our I/O system and the existing controllers nearing the end of their technology life cycle, we realized it was time for a major upgrade of both platforms,” Simmons explains. “We needed a flexible, high-performance control system that could be integrated into our existing infrastructure with minimal impact, and provide a technology framework that would allow us to grow well into the future while protecting our past investment.”

Perhaps the biggest challenge was determining how to implement a simultaneous upgrade of both platforms while minimizing the impact on production. Engineers determined that the best strategic approach would be to implement the upgrade as part of a multiphase process, especially considering the plant’s intense production demands and the potential impact on multiple lines.

Hill’s decided to migrate to Rockwell Automation and its ControlLogix PAC. A key factor in the decision was the ability of the ControlLogix PAC to scan existing I/O cards while also communicating with other controllers in the plant. This solution offered Hill’s a cost-efficient way to convert its existing I/O to the Allen-Bradley Flex I/O platform as part of a multiphase implementation.

The first phase began in early 2008 with the conversion of the first of its four extruder lines to ControlLogix PAC technology. Engineers simply unplugged I/O from the existing system and plugged it into the ControlLogix PAC to test it on weekends. Then, the engineers would plug it back into the original system with minimal impact on production during the week. This helped minimize the downtime required while allowing a phased upgrade.

“That was probably one of the biggest factors that sold this project,” Simmons says. “Implementing this conversion did not require taking the line down for a minimum of six months to a year to replace more than 10 I/O racks, which would be completely unacceptable for our operation due to the high cost of downtime.”

Standardization Supports Plant-Wide Integration
The upgrade to the ControlLogix PAC also will allow the plant to move toward standardizing on EtherNet/IP network communication. Currently the plant maintains multiple networks, including DeviceNet, Modbus Plus and Data Highway Plus. Narrowing these down to a single network architecture will help the plant simplify maintenance and troubleshooting, and lead to better plant-wide integration.

Migration enablers also played a key role in the Hill’s phased approach. The two migration enablers used were supplied by participating Encompass Product Partners in the Rockwell Automation PartnerNetwork: the Automation Network X-change (AN-X) module from Quest Technical Solutions, and the Modbus Plus dual-port communications module by ProSoft Technologies.

The AN-X module serves as a database for all the I/O and ControlLogix PAC interface, linking and mapping them together in a seamless fashion. This module, which replaced an existing I/O scanner, automatically reads all of the I/O card information and passes the information to the ControlLogix PAC via Ethernet, providing plant-wide communication capabilities.

It also offers new tags that can be imported into the Rockwell Software RSLogix 5000 programming software. This allows for easier reference to specific I/O data in the controller.

The Modbus Plus dual-port communications module acts as an I/O module between the existing Modbus Plus network and the ControlLogix controller backplane. This helps provide easier access to processor memory for data transfer between process and module. A 4,000-word register space in the module exchanges data between the ControlLogix PAC and the existing network, allowing the ControlLogix PAC platform to connect directly on to the existing network as a peer.

Ladder logic is used for data transfer between module and PAC. Configuration data is obtained through user-defined ladder. Other potential Hill’s applications include connecting ControlLogix controllers to Modicon controllers, and connecting Modbus Plus-speaking devices such as drives, relays and power monitor hardware to the Rockwell Automation controller backplane.

The continued upgrade of the first extruder line will involve converting the existing controller to the ControlLogix PAC, along with about 10 I/O racks to the FLEX I/O platform. The existing Modbus Plus network will eventually be replaced with EtherNet/IP.

In addition, as variable-frequency drives in the plant are updated, they will be replaced with Allen-Bradley PowerFlex 70 drives.

By reducing its I/O reliability issues and reducing downtime, the plant anticipates about a 5 percent productivity increase. In addition, the high-speed processing capabilities of the ControlLogix PAC will allow the plant to replace the two controllers on its batching line with a single controller.

Valuable Programming Support
After implementing the ControlLogix PACs, the plant will have access to local support in Bowling Green, Ky., through its local Authorized Allen-Bradley Distributor, as well as through the Rockwell Automation support capabilities. This is especially crucial when it comes to programming support for the standard RSLogix 5000 programming package used with the ControlLogix PACs.

“Finding a knowledgeable programmer on short notice can be a challenge, especially in this area of the country,” Simmons says. “Locating programmers for Allen-Bradley controllers has been a much easier proposition – we’ll have a lot more options now.”

The RSLogix 5000 software features add-on instructions, which allow engineers to create sets of commonly used custom instructions that can be easily reused without modification. This lets the plant create standardized libraries that can help reduce programming time and provide consistency to help simplify troubleshooting and reduce training costs.

“Different contractors working on multiple processors throughout the plant resulted in a variety of software code being developed over the years, which increased programming complexity and the need for more specialized software expertise,” Simmons says. “Now when we program across the plant, more of our code will look the same, providing engineers with more standardized instructions and greater consistency between systems.”

In addition, the tag-based programming inherent in RSLogix 5000 software will allow the plant to keep its current I/O wiring configuration in place without changing a lot of field devices. This will help save a major amount of configuration time and cost.

Next Step in the Migration
“With ControlLogix PACs, we’re confident that we now have a stable, long-term migration path that will allow us to protect our investment and scale the technology to meet our long-term needs,” Simmons explains.

The upgrade project will be implemented in phases over five years and will involve upgrading a minimum of six of the plant’s existing controllers, including a distributed control system (DCS), programmable logic controllers (PLC) and motion controllers, to the ControlLogix PAC platform. The upgrade will involve all of the plant’s major production lines, including four extruder lines, a raw ingredients line, batching line and packaging line.

The company also is using this project as a model for its other plants, including a new plant in Emporia, Kan. that will be based on the ControlLogix PAC technology.

“This project is the proving ground for that plant since they are incorporating a lot of our specifications and following very closely what we’re doing at this site,” Simmons says. “We’re leading the way in terms of defining our new technology roadmap.”

For more information about Rockwell Automation Migration Solutions, visit www.rockwellautomation.com/go/tjmg.

Quest Technical Solutions
www.rockwellautomation.com/go/p-quest

ProSoft Technology
www.rockwellautomation.com/go/p-prosoft