Venice, home to Piazza San Marco, the Rialto Bridge... and a rather interesting bolt expansion job on a steam turbine.
Expanding bolts with induction is the proven time- and labour-saving alternative to inefficient flame and resistance heating. With induction, a specially designed coil is inserted into the bolt. Rapid, precisely controlled and localized heat is then induced directly in the bolt. The heat expands the bolt by an exact, pre-decided length, making it easy to remove the nut.
Induction heat delivery is very accurate. Due to the heat being generated within the component, you only heat the part you want to heat, and thus the bolt threads with nuts stay cold during the heating operation.The heating process is so quick there simply isn’t enough time for heat to travel into the thread area. And of course, with induction there is no risk of rods melting inside the bolts—a common and time-consuming problem with alternative heating methods.
The EFD Induction bolt expansion solution is built around a small yet powerful mobile Minac converter and specially designed inductor coils. The Minac also comes in a ‘Twin’ version, where one converter is connected to two independent handheld transformers. This means an operator can work on two bolts at the same time—in effect achieving the productivity of two operators. Alternatively, two operators can work simultaneously, each with their own independent transformer.
Operator productivity is also enhanced by quick-release coils. It takes only a few seconds to attach differently sized and shaped coils to the handheld transformers.
In the bolt expansion process, focus on safety is vital for a consistent result and for avoiding damage to either personnel or the expansion bolt itself. All flash-over from coil to workpiece must be avoided, as high-energy currents weaken the metal structure inside the bolt. Glass fibre insulation holster, varnish lacquers and electronic coil to work-piece detection provides a triple safety on flash-over situations.
Induction heating for bolt expansion is used in high-pressure turbines at power stations, chemical plants and oil and gas processing plants.
The use of induction heating for bolt expansion in high-pressure turbines is a powerful business tool. It’s faster than resistance and flame heating.