At 9 a.m. on a Friday in November 2016, the compressor station at Prevent TWB in Hagen is on fire. In the middle of the production hall, above the presses and welding machines, the fire department is deployed to extinguish the fire as quickly as possible. But by 11 a.m., it is clear that it is not just a few filters that need replacing, as Rüdiger Schmidt, Head of Maintenance and Production at the pressing plant, had initially hoped: "All the machines were completely unusable, whether compressors or dryers." The oldest compressor, which had been here since the plant was installed in 1996, had to be consigned to the scrap heap, as did the latest acquisition, an Atlas Copco compressor that was only two years old. The task now was to restore the compressed air supply as quickly as possible so that production could continue.

The company manufactures floor panels, gratings and wheelbarrow troughs in Hagen. But above all rear seat backrests for the automotive industry: sheet metal coils are cut, the blanks pressed, welded and dip-coated. TWB also carries out some final assembly work at the site. The car manufacturer completes upholstery, covers and headrests itself. The VW Group takes 42,000 such metal parts per week for its modular transverse matrix alone.

It goes without saying that with such call-off volumes, the company was on fire. Schmidt therefore immediately pulled out all the stops to procure compressed air for production. On the same day if possible. He called the compressor dealer and compressed air specialist Indrutec, the service partner that has been looking after the station for around ten years. Within a very short time, Schmidt had five replacement machines with outputs between 55 and 132 kilowatts in the yard. By 7 p.m., everything was installed and the compressed air supply was restored to 90 percent for the emergency feed.

That same day, it was clear to everyone involved that the installation could not remain as it was and that a new station should not be built at the previous location. A completely new compressed air station had to be planned and built elsewhere on the site. "A fire in the middle of the press shops could have had devastating consequences later on," explains Rüdiger Schmidt. In any case, the previous solution was not ideal because the compressors drew in air from the area around the production machines. Dust particles and oil mist included. "Even if our processes don't require oil-free compressed air, the wear on the compressors is higher and the filters become clogged more quickly."

New station with five compressors

The Hagen-based company and its compressed air consultant came up with something new. They designed a station consisting of five new compressors, all oil-injected GA screw compressors from Atlas Copco, each with an output of 90 kilowatts, two of which were speed-controlled. They were housed in a separate building in the open air, about 50 meters away from the production area on the site. TWB converted the former machine hall into a compressor room, laid steel tiles from its own production on the floor and connected the production facility via insulated pipes and cables.

The compressed air station consists of five compressors, all gas screw compressors from Atlas Copco, each with an output of 90 kW. (Image: Atlas Copco Compressors and Compressed Air Technology)

The three GA 90 FF full-load idling compressors run almost around the clock, as the pressing plant operates in three shifts five to six days a week. One of the speed-controlled compressors - type GA 90 VSD FF - is switched on as required via the higher-level ES 16 control system, while the other serves as a redundancy. A refrigeration dryer is installed in all compressors.

"We had good experiences with the compressors and service from Indrutec at our previous station," says Schmidt. "After all, the compressors withstood the poor conditions for years without any unforeseen failures." The new station was therefore planned with the two companies again. In total, there is now 35 kW more available than before to supply the laser welding system, paint shop and assembly with compressed air. Despite this, the electricity bills have fallen.

On the one hand, this is due to the efficiency of the new compressors and the sophisticated control system, but above all to the comprehensive heat recovery system, with which the company utilizes every degree Celsius of compression energy. The Hagen-based company uses the heat from the compressor cooling water in its processes on the one hand and heats the production hall with the warm exhaust air on the other.

Fire protection precautions

Incidentally, TWB has taken precautions in the event of an emergency: Two external smoke detectors are installed in the station; each compressor also has its own smoke detector, and in the event of a fire, the entire station can be separated from the production area in terms of ventilation. An unregulated, older GA 90 compressor from Atlas Copco is located in the cellar below the production area as a reserve compressor. But an emergency is unlikely to occur, as the sheet metal processor has concluded a five-year maintenance contract with Indrutec.

According to documents from Atlas Copco / ee