Maintenance at Salzgitter Flachstahl (Part II)

The integrated steelworks in Salzgitter is akin to a complex organism. From the sintering plant through to strip coating, the plants are closely connected in technical, energy and logistics terms. If a component malfunctions, this can endanger the smooth operation of the entire process chain, which is why experts in production and maintenance work hand in hand. “These two areas are the pillars that underpin steel production in Salzgitter. Our focus centers clearly around plant availability and high-quality production,” as Gerd Baresch, Plant Director for Technical Service, Energy and Environmental Protection states. This concept of integrated process and plant technology (iPAT) in the steelworks is Gerd Baresch’s definition of exemplary state-of-the-art maintenance. His department’s job is to conduct the interplay between decentralized and centralized maintenance with external specialist firms just like an orchestra. The issue is to coordinate deployment of the various instruments and soloists, from the 130mm wrench in plant assembly technology right through to the tablet for maintenance notifications, from the circuit diagram and troubleshooting guide through to the AI application for the analysis of process stability in hot rolling, from the IT infrastructure all the way through to the supply of energy and media, along with all the necessary maintenance rounds, spare parts bookings, and so much more.

Contemporary maintenance is not only a question of fast, efficient and cost-effective elimination of incidents. It starts much earlier, already in the planning phase and in the design of lean, low-error processes. The art is to find solutions before a problem gets big and its elimination expensive. “That said, the real heroes of maintenance are competent experts, more the quiet sort of people. Their job is a job well done if plants and processes run reliably and no spectacular damage needs to be rectified,” says Stefan Thelen, Head of Plant Technology in the cold-rolled flat product segment.

Maintenance employees must therefore be familiar with how the plants interconnect. “In this context, it is important to think in processes and in a logical manner, and to eliminate weak points on one’s own, whether with a simple mechanical aid or by using a digital application,” Thelen says. There are three different strategies for securing plant availability: reactive, condition-based and preventive maintenance. Reactive maintenance is the response to failure that is not expected but nevertheless planned for. For example, a pump can be operated until it no longer works. The system is then switched to a reserve pump and the defective pump repaired or replaced. There is not always a backup replacement, however. In such cases, condition-based maintenance comes into play. This kind of maintenance necessitates in-depth know-how and the ability to assess the condition of a system, however. “We derive this knowledge from networked sensors, operating statistics, condition monitoring systems and feedback from employees, with learning from mistakes as an integral part of our methodology,” Gerd Baresch explains.

At the integrated steelworks, tens of thousands of sensors in all parts of the process chain generate readings at millisecond intervals that are prepared, analyzed, visualized, processed and stored with the aid of more than 2,000 servers, depending on the application. Consequently, condition-based maintenance depends on the readings and their evaluation, all of which deliver specific indications of imminent failure. By contrast, preventative maintenance is based on a defined road map with fixed maintenance intervals that are to be carried out without any indication of potential downtime. This is applied in particular to bottleneck aggregates where failure could interrupt the production process chain. In this context, sufficient expertise about the technical condition of the equipment is necessary while also taking customer, production and replacement parts, logistics into account, which places high demands on maintenance, both in technical and expert terms, but also with regard to organizational and commercial aspects: Experts must be on standby, along with the necessary replacement part, and ultimately all customers must receive their material on time despite planned production downtime.

In order to control and manage all these processes and factors, maintenance experts use digital tools and resources in taking their decisions. They plan the deployment of expert personnel on a digital capacity dashboard, prepare for repair measures in an SAP system, and service rendered by external firms are billed in digital workflows. Salzgitter Flachstahl has even gone so far as to develop its own app for its plant technology in order to digitalize maintenance workflows. How useful digitalization is for maintenance is illustrated even more clearly in the Salzgitter Group’s “VR Cave”. Virtual reality in this special room is projected onto a wraparound screen, which displays an artificial but nevertheless realistic environment. This is where things that do not yet exist are seen, experienced and tested. “We can visualize 3-D models of all aggregates and components, right down to the individual screw,” says Salzgitter Flachstahl’s Peter Sieland, head of Digital Factory. The Cave has come into its own, for instance with the construction and conversion of plants: If the simulation shows a problem, for example, if a certain area is inaccessible for a crane operator or there is not enough space for maintenance, to replace a pump or valve for instance, the plan can be corrected. “It is easy to calculate how much money that saves if problems like these can be already eliminated in the construction phase and not at a later date when the plant has already been built and conversion and/or delays cost money,” Gerd Baresch says, adding: “Let’s not forget that digital virtualization also helps with training.” It could be said that the Cave is a kind of flight simulator for maintenance staff.