With the increase in large TBM projects over the last few decades and a global awareness of their environmental impacts, there has been a greater focus on the origin of TBMs and their parts. The focus has been further highlighted by the ITAtech; a technology-focused committee for the International Tunneling Association (ITA-AITES) that produced guidelines on rebuilds of machinery for mechanized tunnel excavation were released in 2015. While the guidelines are relatively new, Robbins has a long history of delivering robust machines, many of which are rebuilt (many are also 100% new). In this post, I’d like to explore just what a “rebuilt” TBM is, and what that means to Robbins as a TBM manufacturer.
History and Terminology
Throughout Robbins’ history (over 65 years), our TBMs and design philosophies have been based on the understanding that TBMs require a substantial initial investment, and designing machines for single tunnels is neither economical nor sustainable. This realization has resulted in robust, sturdy designs of high quality that–even before the pencil is put to paper–are meant to last for multiple projects. This is clearly shown when you look at the number of Robbins TBMs around the world that are excavating their second, third, fourth or even their eighth or ninth tunnel. There are even Robbins TBMs manufactured in the 1960s that are still in operation!
For Robbins, the term “rebuilt” describes any manner of creating a custom TBM from already existing components. It is the term we use most and continue to use. The ITAtech guidelines introduce different terminologies depending on the extent to which a TBM is rebuilt. They are, very shortly, described here:
- Remanufacturing – Remanufacturing is a process with the aim to start a new life cycle of the product using its current or modified configuration.
- Refurbishment– Refurbishment can be considered a full maintenance, where defect parts are replaced to extend the life of the product in its original configuration or with small modifications.
The guidelines describe the requirements of each process in order to designate a TBM “refurbished” or a “remanufactured”, but in reality the majority of “rebuilt” TBMs may be somewhere in between these qualifications.
The Robbins Philosophy
Over the years Robbins has built a quality assurance system that ensures when we deliver a rebuilt machine, either to the original configuration or a modified one, we still adhere to a design life of 10,000 hours. This standard also includes checks to make sure that all the components are in a functional condition of ‘as new’ or ‘new’. Due to our long experience in rebuilding TBMs, we can offer in principal the same warranty on a rebuilt machine as a new machine.
The Robbins philosophy on this is that, in order to offer the same design life and same warranties on a rebuilt machine, the initial design of the TBM will need to consider that the TBM will be used on several projects. This means that the major structures will need to be strong enough to survive even the toughest conditions and that worn parts can easily be replaced. If the machine is not properly designed for multiple projects, there will be a need to do major work to get the TBM in a working condition either in its original or modified configuration. Robbins strongly believes that considering the total life cycle of a machine, even in its first design stages, is the most economical and sustainable option.
One can argue that project owners typically only have one project and that the condition of the TBM and the suitability of its rebuild is therefore not essential. This is something that is also reflected in many of today’s tunneling projects, where the commercial consideration is often given far more attention than the technical one. We would argue, however, that an initially sturdy and robust design of the TBM will give the project more uptime, higher production rates and better flexibility if unexpected conditions are encountered, making it a good and effective kind of insurance for the project. This effect has been clearly identified in the field, where Robbins has more than 90% of world production records in hard rock.
In terms of the international guidelines, they are certainly necessary and welcomed. However, the strictness of the guidelines makes them hard to adopt worldwide and perhaps not realistic for the majority of TBM rebuilds, which are customized based on project needs. The ITAtech guideline is also missing something else: the definition of what makes a TBM “new”. While opinions from different suppliers vary, Robbins is perfectly clear on this topic: If you are buying a new TBM, then it is a 100% new TBM with only 100% new components. We strongly believe the whole industry should commit to this definition of what makes a TBM “new”, and this definition should be added to the guidelines.
Robbins has throughout the years built up a vast experience in providing the right machine for the right project, whether that means a new or rebuilt machine. As a part of this experience, we are convinced that the life cycle of TBMs should be considered at the earliest stages of the design process. Designing machines with ease of rebuilding in mind ensures that we do not have to start from scratch every time a machine needs work. It also results in time, cost, and energy savings when the time does come to rebuild a machine for a new project. For the industry, this type of perspective is the only economical and sustainable option going forward.
By Sindre Log, Civil Engineer and General Manager for Robbins Norway
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