| Title | Identification of Failure Modes and Their Effect in Geothermal Power Plants |
|---|---|
| Authors | Helen Ósk HARALDSDÓTTIR, Sunna ÓLAFSDÓTTIR WALLEVIK, Sigrún Nanna KARLSDÓTTIR, Kolbrún Ragna RAGNARSDÓTTIR, Sæmundur GUDLAUGSSON, Kristján Friðrik ALEXANDERSSON, Jan PŘIKRYL |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | FMEA, Geothermal, Power plant infrastructure, corrosion, scaling |
| Abstract | This work provides failure mode and effect analysis (FMEA) results for a variety of different geothermal power plants based on answers from power plant operators. The focus of this analysis was on erosion, corrosion and scaling occurring on metal components within the plants. The components in the different sections of the plants were considered. This includes the components in the steam production system, steam transmission system, reinjection system and cooling system. Severity, occurrence and detectability scales adjusted to geothermal power plant operations were used to evaluate the failure modes and their effects. Analysis of the results showed that using only the risk priority number (RPN) to evaluate the issues is limiting. The severity and occurrence were therefore also used separately to obtain an overview of the most critical problems. These values were used to rank the highest failure mode and corresponding effect for each major component. The overall highest-ranking issue based on the RPN was leaking of pipes in the gas extraction system due to corrosion. Following this problem was leaking of steam gathering pipes, clogging of brine pipelines and labyrinth seals, and crack formation in diaphragms due to erosion. Erosion, corrosion and scaling of valve components preventing them from operating properly and scaling to slotted liners downhole, were also high-ranking issues. The most severe issues were determined to be leaking of the gas extraction pipes, sticking and leaking of valves, and cracking of turbine components. Erosion, corrosion and scaling of vessels, sticking of valves and leaking of pipes were given a highest occurrence rating by some of the operators answering the FMEA. Despite the rating schemes being relatively well defined there is always the potential of bias in the answers from the operators. These results are also highly dependent on the issues encountered at each power plant. Instead of providing a listing of which types of problems can be expected at each plant and their impact, the results therefore provide an overview of the most critical problems that can potentially be encountered in geothermal power plants. This allows for identification of where new material and design solutions for components within geothermal power plants can be incorporated to lengthen the lifetime of components, make the operation of the plants safer and reduce operational cost. |