Migrating the Automation System of a Textiles Chemicals Plant

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For CHT, selecting a systems integrator was more important than the bid price. More importantly, the integrator would need to be willing and able to accommodate the needs of a specialty chemical producer, especially with regards to additional changes throughout the course of the project. Of the five systems integrators in question going into the evaluation phase, Erler came out on top.

“Going into the project we were well aware of the scope and complexity of the task at hand. Since we had no previous experience with Aprol, we were initially a bit skeptical as to whether this system was up to the challenge,” explains Alois Erler. “However, our doubts faded quickly over the course of the project.”

A Smooth Migration Process

The migration process also went more smoothly than expected, as Erler confirms, “Aprol is very open as compared to other process control systems, which allows us to react very flexibly to customer requirements even when a project is already underway. We were also very pleased with how easy it was to link up to the existing legacy system.”

The first migration took place in late 2011 on an immensely complex pilot station with around 360 digital and 20 analog I/O channels, and since then a new production station has been migrated nearly every week. By the second quarter of 2013, all 68 stations at the Dusslingen plant had been completely migrated to Aprol, and the old process control system was shut down for the last time.

CHT’s new solution includes 46 Power Panel HMI units, just under 70 X20 controllers and a total of around 14,000 digital and 1,000 analog X20 I/O channels, as well as various shift supervisor stations connected via VNC. The system includes two runtime servers, one engineering server and a VNC server secured by a disaster recovery system. The redundant Linux-based production network communicates with Windows devices on the corporate network via a clearly defined interface.

Double Redundancy Guarantees Availability

“We have even incorporated double redundancy,” adds Schätzle. Every component in a station can be reached via two bus systems: an operator bus and a process bus. Each bus can take over for the other if it becomes necessary. In addition, each station is equipped with two ports that can back each other up. This ensures the high availability that the stations demand. Before the migration was even complete, it was clear that CHT had found something more than simply a replacement for the old system. “The Aprol system is significantly more flexible, and we can now have a new valve up and running in a matter of hours rather than days. Any changes to the software can also be reversed with a single click if an error is detected.”

Analyzing process sequences is also a much simpler task these days. “With TrendViewer and AuditTrail, we found that we were able to analyze processes that we did not have access to before,” explains Schätzle. One way that CHT uses this additional information is to analyze and reduce energy consumption. “Now, we also have the option of controlling critical process values individually to further increase the safety of the stations, especially with regard to processes that require certification.”

* First published in PROCESS India

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