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Alstom uses EFD Induction Minacs for bolt expansion

SKIEN, NORWAY. Alstom Italy has purchased two EFD Induction mobile Minac 25/40 induction systems for their service activities in the electro-technical and power generation industries.


bolt heating


The systems’ first project for Alstom Italy involved scheduled maintenance on a steam turbine in Venice. The Minacs were successfully used to heat and expand the bolts that secure the turbine casing, allowing for fast and easy disassembly.  


According to Alessandro Mariani of EFD Induction Italy, the decision to choose Minac was the result of a rigorous selection process by Alstom. “Scheduled maintenance on turbines is a time-critical job,” says Mariani. “Work has to be completed within narrow time windows. Broken deadlines can result in massive revenue losses for power utilities—and penalties and damaged reputations for service companies. So Alstom set stringent reliability and safety conditions; conditions satisfied by our Minacs.”  


Alstom ordered the two Minacs following an equipment demo in Milan. Although the outer dimensions of each Minac are only 345 x 708 x 453mm, the system’s handheld transformer delivers a maximum output power of 40kW. The power and accurate heat delivery of the Minac (made possible by specially designed elongated coils) means there simply isn’t time for the heat to travel into the thread area. And thanks to Minac’s electronic controls, key process parameters such as temperatures, ramp-up and dwell times can be set in advance and accurately repeated.  


As Mariani explains, several factors make the Minac ideal for bolt expansion. “Speed is the obvious advantage. Then there are benefits such as reliability, ease-of-use, safety and mobility. Moreover, alternatives such as open flames and resistance heaters have serious drawbacks. The former method is slow, uncomfortable and inaccurate, with a risk of excessive heat input damaging the threads. The latter has reliability issues, with a risk of rods melting inside the bolts.”   According to Mariani, Alstom were delighted with Minac’s performance in Venice. “Sure, the job was completed much faster than it would have taken had traditional methods been used. No damage was caused to nuts or bolts. And the operators really appreciated Minac’s comfort and safety. In short, nothing unexpected happened. Minac did what it does best—it got the job done.”