Automated abrasive water jet pin cutting system

After a long operation time, steam turbine blades need to be removed, inspected and/or replaced. Numerous steam turbine fleets feature blades that are attached to the rotor discs by the means of pins. To change these blades, the pins have to be removed. At the time being, the pins are removed using a hydraulic jack. Roughly ten percent of the pins of a steam turbine rotor need to be drilled out due to strains and deformation of the pin. The drilling process is very time consuming and implicates a high risk of damaging the disc. ALSTOM has developed a new system for steam turbine pin removal using abrasive water jet cutting technology with respect to the geometrical and process requirements. The new system can therefore be applied to nearly any large steam turbine rotor. The system basically consists of a robotic tool including a precise camera, a cutting nozzle and a catcher, a pump system and a control unit. The main aim of the application of the new water jet cutting system is to weaken the pin as far as it can be pushed out using a hydraulic jack.