Maximum temperature difference cycle index of heating transmission main lines in thermal power plants

The parameter characterization of temperature fluctuation is very important to predict the frequency of fatigue cycles. At present, the small temperature difference in the frequency of pipe fatigue is approximately evaluated in unit of day. Proposes a small temperature difference cycle based on the continuous operating temperature of the whole heating season. Collects the thermal parameters of eight typical thermal power plants pipe network for five heating seasons in Shanxi province, and obtains the equivalent temperature difference cycle index of small temperature difference with continuous operating temperature. Determines the large temperature difference cycle index through statistical samples of pipeline accident cycles. Based on both of them, gains the maximum allowable stress of 960 MPa, which is higher than 750 MPa in the existing specification. Because eliminating noncircular small temperature difference in the continuous operating temperature in heating seasons, expands the range of the critical stress, and provides scientific data for the fatigue analysis of pipe fittings.