Double wall tube often known as Bundy tube is mainly used as hydraulic brake hose in the automobile industry. It is produced from continuous copper clad steel strip, which is brazed after cold fully overlapped forming. Brazing consists of melting and scattering the copper coating on the surfaces of the strip after forming in order to obtain (once the copper is solidified), a strong double wall tube suitable for the required duty. Such a process can be performed inline using either a electric-resistive system (for a production speed of not more than 20m/min), or an induction system in cases of high productivity (up to 100m/min). For the latter scenario, Emmedi has developed induction equipment based on solid state technology, which is able to heat double wall tube up to 1,200C in a controlled atmosphere. The equipment for diameters of 4.76mm to 6.35mm is able to undertake perfect melting and scattering of the copper around and along the inner spaces of the tube walls. Production with OD 4.76mm at 100m/min can be undertaken at 420Kg/h, while for OD 6.35mm at 100m/min it is 580Kg/h. The system consists of one inductor bench composed of two groups (heating zones) of 4 inductors each. While the first zone heats the tube up to approximately 700C, the second one finishes the thermal cycle bringing the temperature up to 1,200C. The inlet temperature is 20C. Each group of inductors is connected to its own solid-state induction equipment, which supplies the necessary power for achieving the best results in terms of production speed, temperature and brazing uniformity inside the tube. In addition, the equipment also includes a cooling system, heat exchanger, stainless steel tank, and stainless steel centrifugal pump. The equipment also comes with a push-button control panel, selectors, analogic meters and a graphic digital display. Two independent infra-red pyrometers are supplied for measuring the temperature of the tube and controlling the feedback of the output power during this process.

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