Abstract: A process for operating a hydraulic machine, especially a hydro-turbine, includes the step of detecting an actual machine state during operation of the machine by ascertaining operating data. The ascertained operating data includes flow through the turbine (if present), effective and reactive power fed into the electric mains, guide vane opening, pressure before the machine and at the suction pipe exit, headwater level, and tailwater level. The method further includes the step of processing at least one state characteristic values of a first cavitation characteristic value (indicative of cavitation intensity), a second cavitation characteristic value (indicative of an abrupt rise in cavitation manifestations), vibration characteristic values, suction pipe pressure, sand concentration, air pressure, water temperature, and generator temperature (for example winding temperature).

Abstract: A method for optimizing the efficiency of a set of machines comprising a double-controlled turbine and a generator. A correlation is determined between the efficiency .beta., flow Q, variable height of fall H, gate opening .DELTA..gamma. and runner opening .phi. on a model set of machines by test series. The determination yields a model optimum curve for the respective height of fall, the model optimum curve having the optimum gate opening as a function of flow and runner opening. An optimum efficiency for an operating point of a large-scale system is determined by, based on the model optimum curve, making variations of the gate opening .DELTA..gamma. and of the runner opening .phi. on the large-scale system, the variations being such that the flow of the model set of machines would remain constant for the same variations, and wherein the flow of the large-scale system is also presumed to be constant. The power outputs before and after the variations are compared to determine stepwise the .DELTA..gamma./.phi.

Abstract: In a two-piece piston with a head piece and a trunk hinged only over the piston pin, the annular space radially located inside the piston ring groove and open in the direction of the trunk is covered with a sheet metal wall part forming a cooling duct. The sheet metal wall part is held by a collar that extends from the outer annular wall of the head piece and is cramped around the sheet metal wall part. For optimally covering the annular space, the sheet metal wall part is radially divided into two parts.