Soldering: gas or flame?
A washing machine cleans the pipes at a temperature of roughly 70°. Once all dirt has been removed, the pipe and fitting are either soldered on the inductive soldering stations or, in the case of large diameters, welded. With soldering, there is a choice of inductive soldering using inert gas or flame-soldering with flux. With both processes, the pipe is heated evenly from all sides and joined to the connecting part in that way. In the case of larger pipes, high-precision work is required: The welding machine current has to be set so that it produces a melt, the pipe material becomes fluid and can be joined to the fitting with the aid of a welding rod. Finally, the pipe surface is pickled and given a corrosion-proof coating. To make sure the joint does not leak, it is pressure-tested under water with compressed air at 0.5 bar. Pipes that are subjected to higher pressures on the engine are tested for leaks on a special test bench by pressurising with oil to 80 bar.