In vertical cuts to success

Control system migration in a special waste incineration plant

When it comes to migration projects, plant operators are faced with many decisions: Which successor system should be used? Do we modernize from the marshalling level or only from the interface level? Do we go into complete plant shutdown? GSB Sonderabfall-Entsorgung Bayern GmbH has faced these and many other questions and made the right decision throughout - from the implementation partner to the applied technology.

With its eleven sites, GSB ensures the environmentally sound disposal of industrial waste for the whole of Bavaria. Approximately 380,000 tons of material are processed safely and reliably each year under strict environmental guidelines. The incineration plant for hazardous waste in Baar-Ebenhausen forms the backbone of the area-wide disposal infrastructure. In 1996, the two incineration lines 2 and 3 went into operation, while the first incineration plant was shut down in 1999 after 24 years of operation. The regular renewal of the control technology was the decisive factor for the modernization of the incineration lines including the auxiliary plants. The focus of the upgrade was on the long-term availability of the new control system. Through strategic planning, GSB wanted to secure the longest possible period for service and support as well as the supply of spare parts. The biggest challenge during the migration was to maintain plant operation, as plant manager Wolf Reuter reports: "There has never been a total shutdown at the Bar-Ebenhausen plant in recent decades. For good reason, because we have purchase obligations: Some of our 5,000 industrial customers would have to stop their production if we couldn't reliably keep up our work." The rotary kilns in Baar-Ebenhausen, for example, are in operation around the clock, 365 days a year. Solid, liquid and pasty wastes burn at around 1200 °C. Only for the annual revisions the 12 m long, almost 5 m high kilns are put out of operation one by one.  

  Pilot project secures important findings

To be able to set up a watertight migration strategy under these conditions, GSB decided in 2014 to first invite tenders for a partial control system modernization. SAR Elektronic GmbH was awarded the contract for the exhaust gas scrubbing water treatment plant (Abgaswaschwasser-Behandlungsanlage – AGWW). The company has been implementing automation solutions around the globe as a general contractor or subcontractor since 1985. More than 600 employees in seven business units ensure successful projects for customers in industrial manufacturing, the process industry and environmental technology with in-depth knowledge and passion.

 

The AGWW consists of a series of chemical-physical treatment steps in which the water from the flue gas scrubbers is freed from pollutants and heavy metals. For monitoring and controlling the individual processes, the Simatic PCS 7 process control system replaced the previous system with Simatic S5 controllers. Andreas Innerhofer, project manager at GSB responsible for the modernization of the process control system, attaches great importance to this first migration step: "We have gained a lot of valuable knowledge from this migration pilot. In order to be better prepared for the modernization of further plant sections, we have completely revised our plant identification system and updated our P&IDs."

Powerful peripherals

After SAR also won the tender for the further modernization steps, an already experienced team was now entrusted with updating the entire plant. The migration strategy was based on the experience gained from the pilot: "We decided to make vertical installation. This means that we decided to completely migrate plant section by plant section to the new system," says Innerhofer and continues: "This means that we will use two control systems in parallel during the transition period. A horizontal wiring, i.e. visualizing the entire plant with the new control system but leaving the automation level for the time being, was simply not an option for us. We wanted to benefit from the new technology consistently." So, the migration strategy started below the automation level: In the marshalling cabinets, the previous Termi-Point posts were replaced by push-in terminals and the new control cabinets were connected in which a completely newly developed peripheral line from Siemens now performs its services: Simatic ET 200SP HA. Based on the success of the ET 200 product family, the new I/O system was designed according to maximum economic aspects and meets the highest demands in terms of availability. Thanks to a flexible - both vertical and horizontal - installation, a very high channel density can be achieved in the control cabinet, which de facto means that more power is made available in the given space. 

The new clarity

For both SAR and GSB, the new hardware opened up a variety of advantages. "Due to the individual power supply of the inputs, no potential distributions are necessary, and all inputs can be wired directly to the terminals and supplied with 24 volts," explains Manfred Prokosch, who is responsible for the project as technical project manager on the part of SAR. "In addition, we were able to build the cabinets in a standardized way according to a recurring layout." Innerhofer confirms this from the user's point of view: "We now get a uniform marshalling level: two wires go into the field per encoder, there is no extra power supply, no additional circuit brakers or similar. This is very simple, clear and extremely diagnostics-friendly." The number of cabinets has been drastically reduced. "That's also one of the advantages of our strategy of vertical installation," Innerhofer explains. "We were able to redesign the layout of our plant sections, optimize cable routes and thus gain enormous clarity."

Well proven: the new guidance system

In addition to cutting-edge hardware, GSB also relies on modern control system software. Flue gas cleaning is the first section now running on the latest version of Simatic PCS 7. The first few months have shown that the new possibilities offered by an advanced control system are changing the way operators think and work: "The comprehensive and intuitive curve and trend display in the new system very quickly led to most colleagues now driving via trend observation," reports Marco Düsedau, shift manager in Baar-Ebenhausen. "This makes it possible to see much earlier what will happen next. Colleagues are really excited about the fact that they can click their way step by step to the root cause of a malfunction. Today, I'm shown quite clearly that a filling level is too low, for example, and therefore a certain process can't be started. In the past, such causes could often only be clarified by consulting the field crew," Düsedau continues.

At eye level

The entire migration project will be completed in 2021. So far, everyone involved is highly satisfied with the cooperation and what has been achieved so far. "What we particularly appreciate, in addition to the extensive improvements provided by the new Siemens technology, is the fact that the specialists from SAR are not simply programmers," says plant manager Reuter. "Rather, the employees are here with us on site or in the control room and have a great deal of process engineering know-how." Colleague Innerhofer adds, "Just by the nature of the questions, you can tell that there is a real understanding here of our daily challenges. This means that the new control technology doesn't just work, but makes a lasting contribution to improving our work." Thus, the core idea of the modernization has been optimally implemented, as also expressed by Dr. Dominik Deinzer, Managing Director of GSB: "Especially in times of economic boom, it becomes apparent what a valuable contribution we make with our plants for an industrial nation like Germany. To be able to fulfill our tasks in the best possible way, we rely firstly on our employees with their commitment and ideas, secondly on competent partners and thirdly on state-of-the-art and reliable systems for process monitoring and control."

simatic compact field unit

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