Tunnel Business Magazine

JUN 2018

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is fille d hidden benefits including familiarity of machine operation and proven performance for that particular piece of equipment. Rebuilt, Remanufactured or Refurbished The r oth the process and the standardiza- tion of rebuilds — has become a focus for the industry as more proj- ects with multiple machine requirements and short time frames are being proposed. 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 in 2015. For Robbins, the preferred term is "rebuilt," which describes any manner of crea om already existing compo- nents. The ITAtech guidelines introduce different terminologies dep ebuilt. 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 or- der to designa efurbished" or a "remanufactured," but in reality the majority of "rebuilt" may be somewhere in- between these qualifications. In terms of the international guidelines, they are certainly nec- essary and welcomed. However, the strictness of the guidelines can make them hard to adopt f ebuilds, which are customized based on project needs. That is not to say that the guidelines are not useful. "I think the guideline, as written, would make a very good standard for own- ers to reference when allowing the use of a sec " says Roby, but he cautions that certification as to the quality of the rebuild is necessary: "The owners should specify that any sec- ondhand machine be certified by an independent third party en- gineer. I would suggest that the owner also require the tendering contractors to list in their bid the history and technical specifica- tions any sec e and to include in their bid the name of the company they intend to use to remanu- facture the as well as the third party engineer they intend to employ to certify the remanufacturing. All of these should be in accordance with the ITA guidelines." For Willis, rebuild guidelines may be less pressing than chang- ing the culture of operation and maintenance for many con- tractors worldwide. "I know it can be done — it's just a matter of convincing contractors to operate the machine properly. This will mean the machine at the end of a project will need less mainte- nance before it can potentially be reused. However, it's also impor- tant, where possible, to encourage project owners to standardize the sizes of tunnels, thus increasing the p euse." Training should be specific to the machine and the geology, though there are some commonalities in what is required for maintenance. "What I say is that when you first start a machine, inspect it often, until you know what to expect. The cutterhead and screw conveyor may need an intervention once a week, or once a month. Someone has to perform inspections often enough to know that a particular component has damage or is becom- ing worn out," said Willis. He added that even when the geology seems predictable, that should not be taken as failsafe, and has some advice for contractors: "Geological surveys are extremely im- portant but can be unreliable. So do interventions until you have a baseline knowledge for how the machine is reacting in specific types of geology. Don't be complacent — just becaus big machine with a hard metal cutterhead and tungsten carbide cutters, it's not true that nothing can damage it." Used vs. New Is a use od as a new one? In short, the answer is yes, with qualifications. The machine's rebuilt specifications should fit that project's geology and unique requirements. With a proper de- sign and rebuild, a used machine has advantages: "The design is proven, the cost is usually lower and there is an advantage in fast- er delivery times. The risks ar operly built or when a machine is put into geology where it's not suitable," said Roby. Overall, there are many benefits, both obvious and hidden, to using a rebuilt machine, but the rebuild should be done within certain design restraints to remain economical. "There's always the possibility to upgrade power and thrust on a machine but there are strict engineering limits. If you increase the cutterhead drive motor power, the gear reducers and final drive ring gear and pinions must have the capacity to take that increase in power. If you're increasing thrust, you need to check the bearing life and make sure that the bearing can take the increased forces. If you're exceeding gripper capacity on a hard ro ou have the wrong used machine for the job." Roby added that the typ and whether it is shielded or not also matters. "If you're chang- ing the diameter of an EPB such that it requires new shields that may not be the best choice economically. Purchasing a larger EPB would make sense in that situation." Over or the long haul is simply a cost effective, energy efficient, and sustainable way of thinking about tunnel boring. Used machines can and have shown their ability to excavate projects at world-class rates of advance and complete many kilometers of tunnel with success. This article was contributed by The Robbins Company . TUNNELINGONLINE.COM TBM: TUNNEL BUSINESS MAGAZINE // JUNE 2018 C O V E R S T O RY 2 0 iPS rescued and rebuilt a European- manufactured TBM at Bangalore, India's Namma Metro. The cutterhead features including cutters and grill bars had been worn away.

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