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Successful migration without any risk

Stepwise modernisation of process control at CHT R. Beitlich
Successful migration without any risk

Companies, particularly medium-sized enterprises, cannot afford excessive production outages in the course of modernising the control technology in their processing systems. Migrating to a new solution step by step can be the answer to maximising system availability and avoiding extended or unplanned downtime, as demonstrated by a recent migration project at speciality chemical producer CHT/Bezema. In order to succeed at this, however, the process control system and control technology need to support the stepwise approach.

The author: Franz Joachim Roßmann Freelance journalist

CHT R. Beitlich recently modernised the processing stations at the firm’s key production site, a factory in Dusslingen near Tübingen, Germany, with B&R technology. “We’ve improved the reliability of our processes and the quality of our products, and we’re now able to react more quickly and flexibly to changing market requirements”, reports Günther Schätzle, Head of Production Engineering at CHT R. Beitlich.
A system migration was becoming increasingly urgent for the company. From its origins as a supplier of textile chemicals, CHT has expanded its business to include speciality chemicals in the areas of textiles, textile care and construction and performance chemicals, with customer-oriented product development and a large, ever-growing spectrum of products. The majority of the group’s revenue comes from very complex products, which are manufactured primarily at the production and logistics centre in Dusslingen. Here, CHT operates 68 processing stations, including ten higher-level supply systems, 40 mixing vessels and 14 chemical reactors. Many of the production stations are multifunctional and can be used to make up to 100 different products.
Migration objective: more efficiency
“It was growing more and more apparent that our systems for control, HMI and production data acquisition, which had evolved over the course of many years, would soon no longer be able to keep up with the intensifying demands on product quality, quality assurance, process reliability and safety regulations”, says Schätzle, explaining CHT’s motives for beginning the migration process early in 2011. “What’s more, our outdated technology was preventing us from filling new orders.”
It used to take three days, for example, to install a new valve and get it up and running. The increasing frequency of age-related equipment failures and the difficulty of obtaining replacement components were further arguments in favour of migration. The objective was to replace the control, HMI and data acquisition systems, which had become obsolete, inflexible and prone to failure, with new, state-of-the-art technology. “Fully automating everything was certainly not our primary goal”, adds Schätzle, “because that would have been too complex for our multifunctional stations”.
Aprol system stands out
CHT formed a team of experts to perform an in-depth evaluation of three different process control systems, as well as control and HMI so-lutions from two bidders, based on an exhaustive matrix of specific criteria. In the end, B&R came out on top. For Schätzle, the logic sup-porting this decision was clear. “One of the decisive factors was that Aprol provides optimum support for stepwise migration while keeping the old systems running in parallel.”
The CHT experts especially valued the new-found independence from Windows. B&R’s process control and HMI technology is Linux based, and the structure of the process control system is remarkably clear and intuitive.
B&R’s finely graduated selection of control and HMI products has allowed CHT to match the performance of each system’s PLC to its own requirements and equip every one with a line-up of I/O modules and its own HMI unit. “The advantage is that we can mirror the actual system structure directly in the control and HMI technology, which helps us implement the stepwise migration perfectly from a hardware perspective”, explains Schätzle. He continues: “Another argument in favour of a single source solution is the lack of problems with interfaces and communication”.
Schätzle concedes that a solution from a large German control supplier would also have allowed CHT to fit each of its stations out with a separate controller. “Yet this would only have been possible in a roundabout way or with the aid of a soft PLC, both of which were out of the question for us”, he explains.
The CHT manager sees very few disadvantages in switching suppliers for its process control system and control technology. “We would have had to rewrite a significant portion of our software anyway since 50% of the code we’ve accumulated over the years is now unused, which would have made reusing the software virtually impossible.”
From a cost perspective, Schätzle sees very little difference between the solutions evaluated. “There were some considerable variations in the offers we received from systems integrators”, he says, “yet the estimates the integrators gave us for alternative process control systems varied by no more than 20 %”. This is most likely due to the strongly decentralised structure of the production stations, which can be represented ideally by the decentralised structure of the process control system.
For CHT, selecting a systems integrator was not simply about the bid price alone. More impor-tant, the integrator would need to be willing and able to accommodate the needs of a speciality chemical producer, and especially to adapt to additional changes throughout the project. Of the five potentially suitable systems integrators going into the evaluation phase, Erler came out on top. The integrator was well aware of the scope and complexity of the task at hand. On the other hand, since they had no previous experience of Aprol, they were a bit sceptical as to whether this system was up to the challenge. This initial doubt faded quickly in the course of the project, however, and the migration went more smoothly than expected.
The first migration took place on an immensely complex pilot station with around 360 digital and 20 analogue I/O channels towards the end of 2011. Since then, a new production station has been migrated nearly every week. By the middle of 2013, all 68 stations at the Duss-lingen plant should be completely migrated to Aprol and the old process control system shut down for the last time. At that point, CHT’s new solution will comprise 46 Power Panel HMI units, just under 70 X20 controllers and a total of around 14,000 digital and 1000 analogue X20 I/O channels as well as various shift supervisor stations connected via VNC. The system will also include 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 redundant and highly available
“We’ve 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 level of availability that the stations demand.
Even part way through the migration, it became clear that CHT had found more than just 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.”
Analysing process sequences is also a much more straightforward task in the meantime. “With TrendViewer and AuditTrail, we discovered we were able to analyse processes that we didn’t have access to before”, explains Schätzle. “Aprol lets us analyse interactions between processes in real time in order to implement optimisations on the spot. Failed batches can be tracked and analysed later on based on the logged process data.”
One way that CHT uses this supplementary information is to analyse and reduce energy consumption. “We now 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.” After utilising savings potential with Aprol, CHT is looking to take advantage of the additional savings offered through energy management by becoming one of the first users of the EnMon library for Aprol.
cpp-net.com/0313417
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