Thermal fatigue crack initiation and arrest behavior in labyrinth structure subjected to temperature fluctuation in pure water

At a tee junction point of piping system or labyrinth structure of pump seal, hot and cold water are mixed with each other in whirl. The vibrating mixing boundary between the hot and cold water induces a temperature fluctuation on a inside surface of the pipe just after the connection point or labyrinth land and bottom surface. The temperature fluctuation causes thermal fatigue. In this study the thermal stress distributions in the labyrinth structure were analyzed using FEM for various frequencies under the temperature fluctuation of turbulent water flow. The fracture mechanics analysis indicated that the thermal fatigue crack with relatively high frequency of 0.1 Hz to 25 Hz were arrested at a depth nearly proportional to square root of reciprocal of the frequency and it was about 3.8 mm for 1 Hz. (author)