Rain Flow Counting Analysis on Operating Pressure Cycle Characteristics of Gas Pipeline

The analysis on the operating pressure cycle characteristics of gas pipeline is an important research basis for predicting the fatigue life of the pipeline. Based on the rain flow counting method, the pressure cycle in the random load spectrum was counted, the outlet pressure change history of two stations in a pipeline was counted, and the pressure cycle amplitude, mean value, frequency proportion and damage proportion of the pipeline in the stations were analyzed. The analysis results show that the Nmber of pressure cycles with pressure ratio greater than 0.8 in the gas pipeline accounts for more than 90% of the total cycles; the acquisition cycle has little effect on the counting of large pressure cycles, but has great effect on the counting of small pressure cycles; the acquisition cycle is selected for pipeline pressure cycle based on the principle of no loss of large cycle; the higher the frequency proportion of large cycle, the greater the proportion of damage to the pipeline is, but when the Nmber of cycles is large and the cycle amplitude is small, a large Nmber of small cycles are the main causes of pipeline damage. The analysis conclusions provide a theoretical support for the fatigue life prediction of oil and gas pipelines.