CIRCULAR ECONOMY | INSIGHT
previously used in problematic (e.g., contaminated) soils, additional protective measures may be required.
● Inspection: depending on the component, visual inspections, dimensional checks or special tests (such as crack testing, leak testing) are carried out. The parts are then divided into three categories: ‘directly reusable’; ‘can be reconditioned’; or ‘to be replaced’.
● Reconditioning: reconditioning is carried out in the same way as the production steps for a new part. Technical improvements, upgrades or reinforcements can also be integrated.
● Reassembly: final assembly corresponds to initial production. The final testing and documentation are also carried out following the same criteria as for new machines.
● Functional test: the tests are based on the OEM’s testing processes and specifications.
EFFICIENCY POTENTIAL THROUGH STANDARDISATION AND MODULARISATION Herrenknecht expands on the ITA specifications to create a high-level approach. This includes as standard, for example, complete measurement and functional testing on an individual test basis in accordance with manufacturer specifications and in close cooperation with the respective OEMs. The result of such remanufacturing is a machine
that is practically indistinguishable from a new one in terms of performance and appearance. The warranty, including CE or other specifications required in the country of use, is also the same as for a new machine. The prerequisites for this are created with a dedicated
site for rebuild services at the German Rhine port of Kehl. There are 140 experts employed at the site, which has more than 100,000 m2
of production and storage
space. They process around 15,000 components per year. The remanufacturing strategy not only pursues a high technical standard, but also consistently focuses on efficiency to offer customers the optimal solution at the best price. The company increasingly relies on standardised
and modularised components. In this context, standardisation and modularisation mean standardising processes and components to streamline the processes and exploit synergies.
CURRENT EXAMPLES: BOGIES A current example of this approach is the standardisation and modularisation of bogies. These bogies are components in a TBM’s back-up system
that ensure the correct travel of the back-up. They must tolerate high mechanical loads while precisely maintaining the position of the machine but otherwise have no complex tasks to perform. Nevertheless, there have been many different designs in the past, such as right-hand and left-hand welded variants. Accordingly, standardisation here promised great potential for improvement. Design changes were therefore carried out to
standardise the structural steelwork of the bogie and make it uniform. Instead of left- and right-hand versions, adaptation to different tunnel diameters is now achieved using Vulkollan tyres with different correction profiles. This means the bogies can be modular – from 2-axle to 8-axle versions. These modules can be adapted according to needs
and customer requirements. This makes the bogies more flexible and universally usable. ‘Old’ versions are retrofitted to the current design before being used again. This ‘design for reman’ concept has been implemented
in the area of bogies for around two years. The greatest effects of the new standardised and modularised solution are reduced design effort, low rebuild costs and the ability to use a higher proportion of used parts. This represents a first strategic step toward a long- term circular economy. Further components are now to follow successively.
CONCLUSION AND OUTLOOK The remanufacturing of TBMs has established itself as a sustainable strategy that combines technical, ecological and economic benefits. Defined processes and quality- assured standards enable a new product life cycle, saving time, significantly reducing the carbon footprint and promoting the reuse of valuable resources. With a systematic ‘design for reman’ approach, the company is demonstrating how standardisation and modularisation – for example of bogies – can unlock further potential for efficiencies without sacrificing flexibility. In the future, remanufacturing will gain even more
significance in tunnelling. Given growing demands for sustainability, supply chain resilience and economic efficiency, there is an increasing focus on the principle of the circular economy. The systematic roll-out of ‘design for reman’-capable components and even closer integration with digital tools – for example for service life monitoring – offer additional potential. The goal is to further establish remanufacturing as an industrial standard.
REFERENCES 1 Ebel, K.-D. & Spath, D. (Hrsg.): ‘Refabrikation – Produktaufarbeitung als Schlüsselstrategie der nachhaltigen Produktion’ (Springer Vieweg, 2015)
2 ITAtech Report n° 5-V2 – Guidelines on rebuilds of machinery for mechanized tunnel excavation (2019)7
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