Herrenknecht’s treasure trove lies in Kehl harbour – within reach of the main plant in Schwanau – and extends over 100,000 square meters. In the outside area of the factory buildings, components of used tunnel boring machines lie in storage – cylinders, screw conveyors, pumps, entire shield parts and much more. Plant manager Olaf Kortz stands in the shadow of a massive component with a diameter of more than 6 meters and says: “This main bearing has already bored through 3,500 meters of hard rock. But when we're done with it here, it will be at least as good as new.”

Quality is not negotiable

The actual remanufacturing process is highly complex. All components to be rebuilt, from the main bearing to the hydraulic pump, are taken apart down to the smallest unit and are individually cleaned. The reman experts at Herrenknecht then check the prepared parts with special equipment such as endoscopes and laser measuring devices for any deviations from the original condition. Every seal is checked, welds are examined by ultrasound and penetration test. This way, even the finest cracks can be identified.

“Nothing is hidden from us,” says Olivier Kraft. “We are not talking about random sample tests, we are talking about hundred percent testing.” When the specialists from the reman plant find something, they have to decide: can the flaw be remedied – or must the part be disposed of? What passes the strict test is rebuilt in the next step, updated to the latest technical standards and modified for the next deployment according to customer needs. Finally, the individual parts are reassembled into components and tested again in full.

Each remanufactured component must be able to withstand market comparisons with new parts. “When it comes to quality we make no compromises in remanufacturing. Premium remains premium,” says chief engineer Werner Burger. “After the process, each individual part must be at least as good as a new one. Safety and reliability are not negotiable in our business underground.” Consequently, Herrenknecht provides the full guarantee for all components “Remanufactured by Herrenknecht”.

Transparency in all areas

To make the process as transparent as possible, Herrenknecht has committed itself to the official industry standards of the ITA. “For numerous parts, our remanufacturing process exceeds these minimum standards,” explains chief engineer Burger. “But we take them as a clear basis. Also to point out that there is a lot more to remanufacturing than just repair or reconditioning.”

Antonio Nicola has relied on tunnelling technology from Schwanau for more than 15 years. “We have already used completely new TBMs as well as machines with remanufactured components in projects,” says the responsible person for the TBM department at the Italian construction company Salini Impregilo S.p.A. “With Herrenknecht there is no difference in the quality. In both cases the performance was absolutely reliable and the result outstanding. We will therefore continue to rely on remanufacturing in the future.”

For the customer the combination of buyback and remanufacturing offers convincing benefits. “On the one hand, he can sell his machine after deployment. On the other, he can rely on rebuilt premium technology himself, the components of which have already proven themselves in use,” says chief engineer Burger. These are also quickly available – often faster than new parts. “Of course, remanufacturing is a lot of work. But it is considerably more economical than a new production.” A price advantage Herrenknecht passes on to its customers: “We can offer attractive options to customers who choose reman machines or components.”

The Spanish construction company Acciona has also had positive experience with remanufacturing. “We believe that only the manufacturer of a machine can optimally handle the remanufacturing process. He designed it and knows every detail,” says Victor Martinez, Acciona’s Director of the Mechanical Engineering division.“On top of that, every project leads to new ideas, which in turn lead to the improvement of the original design. Our technicians work closely with Herrenknecht in this respect.”

REFURBISHMENT AS AN ALTERNATIVE

Professional rebuilding also plays a key role in Utility Tunnelling. Worldwide, hundreds of Herrenknecht's smaller machines are in operation. The difference: they are often designed to be more “standardized”, for example for boring sewage tunnels within fixed diameter ranges. Consequently, the TBMs can often be used for multiple construction projects in the same or very similar configurations. Because there is less wear after short tunnelling distances of a few 100 meters, it is generally not necessary to take them apart completely and check each individual part separately, as is usual in remanufacturing.

“When the machines come back to us we subject them to a defined test procedure where we check every single function,” says Peter Schmäh, Member of the Executive Board Utility Tunnelling. “And we do the same thing again before they leave the plant.” Action is only required if a fault is found during testing. “In 70 percent of all cases a normal refurbishment is all that is needed.” For the remaining 30 percent refurbishment is not enough. Then the machine goes through the complete remanufacturing process. “The rebuilt components are then used again in the same or other machines,” says Schmäh.

BASICALLY BETTER THAN NEW

All stored parts and components are recorded centrally in a database at Herrenknecht. “We not only register every part, but we also know everything about the performance parameters of its past deployment history,” says plant manager Kortz. “For example, how many kilometers a main bearing has already bored through and what maximum forces it has been exposed to.” In combination with the comprehensive testing process at the plant, the experts can assess exactly whether the parts are suitable for remanufacturing. Thanks to the premium quality of the original product this is usually the case. Only typical wear parts such as hoses or screws are always replaced.

Olaf Kortz uses a thrust cylinder to explain why reman parts from the Herrenknecht plant can sometimes be even better than new ones: “If such a component breaks down at all, then it's mostly in the first meters of a drive.” This is down to production faults, which can never be completely ruled out especially with custom-made parts. “This cylinder has already proven itself over six kilometers,” says Kortz. “So after the remanufacturing process we can be sure it will meet all performance criteria in the next deployment.”

ENVIRONMENTAL PROTECTION: DECISIVE IN THE FUTURE

According to Olaf Kortz, with a completely remanufactured tunnel boring machine the energy savings are about 80 percent. Compared to a new machine, about 99 percent less materials have to be used. A huge saving that conserves resources, reduces CO₂ emissions and thus improves the environmental balance of the machine – and thus the entire construction project.

A contribution to climate protection, which plays an increasingly important role in the context of stricter environmental requirements. Already, detailed environmental criteria apply to public tenders. The Scandinavian countries are leading the way here. Experts believe that both the European Union and other international countries will continue to tighten up their environmental regulations – including for remanufacturing. For example, the EU still only makes a non-binding recommendation to industry that it should rebuild sustainably. This could soon turn into concrete obligations. The era of remanufacturing will begin sooner or later. At Herrenknecht it has already begun, because customers and the market value professional rebuilding.