Automation Vision Comes to Life

The company's slogan, "Helping Make Products Better," encourages the use of technology to improve chemical processes. With this in mind, the Hannibal plant commissioned a DCS team to develop an automation and controls vision for the site. The team knew it couldn't meet its goals with the seven existing DCS local control networks (LCNs). Replacing these systems with leading-edge equipment and software would be a time-consuming and costly endeavor.

The team needed to find the best, most cost-effective automation architecture available. It also had to develop a strategy for replacing the old DCS control networks several at a time, rather than all at once. The team needed to accomplish these goals under tight time schedules, and to minimize production downtime, decrease startup time, overcome resistance to new work practices, and ensure adequate training for affected employees.

Four units' DCS were recently replaced with the DeltaV digital automation system from Emerson Process Management, Austin, Texas.

Technology leaps forward
Although it was challenging to abandon preconceived notions about DCS architecture and function, the DCS team at Hannibal decided to start with a clean slate and evaluate all automation options. They wanted to identify the most capable and cost-effective automation system available; one that would be compatible with future upgrades.

Careful evaluation yielded two potential paths:

1. Upgrade to the existing vendor's latest DCS equipment and gain an incremental process control benefit, or

2. Install a new system based on proven technologies in process automation.

The decision was affected by economic factors and a desire for a less hardware-intensive DCS with integrated Foundation Fieldbus, Hart and Profibus DP technologies. BASF also wanted the life cycle cost efficiencies that come with using standardized PC platforms, which communicate with controllers through TCP/IP Ethernet networks.

After a thorough evaluation, BASF decided that replacing the existing DCS with a DeltaV digital automation system from Emerson Process Management would provide the greatest benefit.

Hardware differences
Once the team chose its automation strategy, implementation was the next step. Complicating the effort was that the new and old DCS were of different manufacture and vintage.

The Emerson DeltaV has a simplified structure: off-the-shelf workstations, standard IEEE Ethernet for the network, and rail-mounted backplanes with plug-in CPU, power supply and I/O cards. These features helped minimize purchase cost and provide flexibility, future compatibility and upgrade paths not available in a proprietary architecture.

The legacy DCS consisted of numerous gateways, nodes, termination boards, I/O boards, controllers, communications cards and consoles. One of the primary drivers for moving to a new system was to eliminate as much legacy hardware as possible. The team developed a modified version of Emerson's Flexconnect, which connects DeltaV I/O directly to the existing DCS termination panels using pre-built cables.

Automated configuration
Configuration of the DeltaV automation system was largely automated. The team developed a program to convert point parameters into a flat file, which was imported into standardized DeltaV modules. One of the challenges with this approach was that the new modules had many more features than the legacy system. For example, Hart data are brought into the modules at a channel level, so transmitter range and diagnostic information is tied to the analog input signal. Default module settings were set up to uniformly act on these additional data.

Process control configuration, including interlocks, also posed a challenge since many people had worked on the existing programs in the past. Determining the original programmer's intent was critical to ensuring that the new code had the same functionality. The process had to be studied in detail to reestablish which actions should occur and why.

The legacy system relied on separate text and logic block code for interlocks, whereas the DeltaV interlocks are built into the device control modules. The operators can easily view them from a module faceplate. The new DCS's ability to show the current status of interlock initiating variables and to see the "first out" condition has proved to be very helpful.