Turbine repair at Nesjavellir geothermal power plant: An Icelandic case study

During a quadrennial inspection of a 30MW Mitsubishi steam turbine at Nesjavellir geothermal power plant, corrosion products were found on the last set of labyrinth packing in the gland seal system which resulted in erosion corrosion of the turbine rotor. The rotor had worn by approximately 8. mm. Because of the tight timeframe of the overhaul, it was decided to repair this failure on site using the experience of the staff and domestic industry. Labyrinth seals were built by a domestic machine shop, decreasing cost and shutdown time dramatically. This article describes the occurring failure and how it was repaired within days with cooperation between the energy company and domestic industry. It further discusses probable causes for such failure and how it may be prevented. The article describes in essence how valuable it can prove to build maintenance knowledge domestically in the geothermal sector.