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

• Geothermal rotor was worn down by 8 mm and fixed on site.
• The wear was considered to be caused by erosion–corrosion products on the labyrinth packing.
• We show root cause analysis for the occurring failure.
• The shut-down time was kept to <4 weeks by using domestic expertise.
• Described are the benefits of building maintenance knowledge domestically in Iceland.

During a quadrennial inspection of a 30 MW 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.