Case Study: Lapino Powerplant Penstock Failure

The paper presents the results of investigations carried out in connection with a penstock rupture at a small hydropower plant in Poland. The investigations comprised material tests of the ruptured penstock shell, analysis of the stress in the shell of the ruptured penstock section, analysis of hydraulic transients under conditions of failure, and testing of the penstock and gensets after repair. In the case under consideration, excessive water hammer caused by rapid flow cut-off was recognized as the direct cause of the penstock burst. Low strength of the penstock shell because of low quality weld joints and lack of strengthening in places of large stress concentration also contributed to the penstock failure. Results of the case investigation highlight some problems that should be taken into account during the process of design, modernization, and operation of hydropower plants in order to ensure their safe operation.