The direct cause of gathering pipe network failure was the failure of the pipeline and accessories equipments according to a lot of field investigation .The fault tree was established as the top event of gathering pipeline failure on the basis of the comprehensive analysis of gathering pipeline network failure factors. Considering about the 44 basic events, the descending method was used to analyze the gathering pipeline network failure fault tree, and obtained all 52 minimum cut sets in the system. And the quantitative analysis of the fault tree was carried on. The qualitative analysis was carried on the gathering pipe network and the weakest link was found out in gathering pipe network, which could maintenance the old pipeline network and provide theoretical guidance for the design of the new pipeline network.

Being aimed at the problem of contaminated oil in batch transportation of the same gasoline and diesel on different density condition during product oil flowing through the downhill and uphill, with the help of VOF model, the numerical calculation of threedimensional flow model was established. The influence of contaminated oil from different sequence，density，pipe range on boundary layer region was researched on the uphill and downhill road. The results showed that for uphill pipeline the length of the mixed oil of forward diesel was longer than forward gasoline，and the mixed oil volume of forward diesel was greater than forward gasoline. For downhill pipeline the length of the mixed oil of forward gasoline was longer than forward diesel and the mixed oil volume was greater than forward diesel. During forward the same gasoline and trailing diesel for different density diesel, the smaller density could help reduce mixed oil volume.