The effect of fluid temperature and crack size toward stress intensity factor on geothermal pipe installations

A pipe is a fundamental component of the geothermal power plants to drain the water vapor from the inside of the earth. Structural durability is the main focus of geothermal pipe which is affected by the thermal stress caused by internal pressure and fluid temperature. In the present study, the stress intensity factor for mode I was investigated under variations of fluid temperature and crack size. A commercial finite element analysis (FEA) was used to find the highly stressed regions in the geothermal pipe by using solid-fluid interaction model and calculate the stress intensity factors. Variations used in this study are a fluid temperature in pipes of 80°C, 115°C, and 150°C and surface crack size of 1 mm, 3 mm, and 5 mm. This study used ASTM A106-B steel material which is geothermal pipe standard. The result showed that the fluid temperature and crack size in the pipe installation affects the stress intensity factor. The stress intensity factor increased with increasing the fluid temperature in the pipe and crack size. Furthermore, the pipe installation with 5mm crack size and fluid temperature in pipes 115°C and 150°C has stress intensity factor value that exceeds the fracture toughness value of the material. This condition will lead the crack to propagate along the pipe.