Formation ofhydrate in wet-gas pipelines could bring potential safety hazard. Flow safety evaluation of wet-gas pipelines is of importance for guaranteeing production safety and minimizing losses. The first step of this evaluation is to calculate the probability of hydrate formation(HFP) in wet-gas pipeline. In this work

based on the reliability limit state method and the calculation of the hydraulics and thermodynamics for wet-gas pipeline

and using the water content in sour natural gas predicted by higher precision Har-PR and the conditions of hydrate formation estimated by Chen-Guo model

a probability limit state equation is established from the difference of temperature of hydrate formation and actual flow in the pipeline

and the probability of hydrate formation(FHP) in pipelines is calculated by combined probability method. The entrance data in the experimental hydrate flow loop is analyzed

and the results show that there is the Gaussian distribution for inlet pressure and temperature and the largest extreme value distribution for the inlet flow rate. A case calculation demonstrates that:(1)all mean values and standard deviations of random variables affect HFP in wet gas pipelines; (2)the sensibility of the HFP is different for different random process variables; (3)the probability of hydrate formation in entire pipeline is affected by both the sample numbers for single and combined random variables.