A Rotary Air Preheater is a rotary heat exchanger in which heat exchange takes place thanks to the heat capacity of slowly rotating elements – sheets placed on the rotor. These elements take over the heat from the flue gases from the boiler (they heat up) and transfer it to the air sucked in from the environment, next directed further to the boiler burners. Thanks to the use of OPP, the efficiency of the installation is significantly improved by recovering a large part of the heat from the flue gases. OPP is used in virtually all solid (coal) fuel boilers.   Our scope included machining work in four holes: rounding/turning of the hole to size Ø615H7, facing from approx. Ø120 mm to Ø 615 mm with allowance 50 mm (very large allowance!), production and assembly of centering sleeves, drilling and threading holes in the heater body and covers.

The heavily damaged surface of the journal is salvageable! If the scratches are too deep and it is possible to make mating elements (e.g. bearing shells) on a slightly smaller shaft diameter, then turning is enough to remove scratches and grooves and obtain the right surface quality. If it is important to maintain the original diameter, the turning operation must be preceded by premachining (optional) and layer welding. Only then can the original geometry be restored. We implemented such technology, for example, in the Bujagali power plant, Bujagali HPS, Uganda | WWTECH – On site machining In both cases, the last step of treatment can be honing using the same machine tool.

The purpose of standard flange machining is to obtain the correct flange geometry: flatness of 0,05 mm, perpendicularity to the axis – not more than 0,02 mm, and, importantly, adequate surface roughness (< 3.2 μm) More: Machining of flanges | WWTECH – On site machining