By introducing PCM in the multifrequency principles and using DM produced by Radiodetection company, the article showed respectively the detection results of the anticorrosion layers from Shuwulian to first station, from Shuyilian to Shuwulian and from Shusilian to first station gathering pipelines in Shuguang oil production plant in Liaohe oilfield. The inferior and poor level of the three pipelines was accounted for 50.2%,51.8% and 42.9% respectively on all the anticorrosion layers. The detect results and the verification of suspected leaks were consistent. There were certain limitations when PCM was used only to detect underground pipes .If it was combinated with other detection means, the results would be more accurate.

Aiming at the mixed oil quantity of pipelining products, mixed oil control equations of batch transportation was established based on multiphase flow model and finite volume method. The transportation mediums were 0# diesel and 90# gasoline. The numerical calculation was based on two cases, the product flows through a Ztube from top to bottom and from bottom to top. The research shows that when it flowed through the horizontal section of a Ztube, the distribution of mixed oil is not symmetric. In a vertical section, there are lager amount of mixed oil when diesel is above gasoline and the distribution of section concentration was more uniform when gasoline is in front of diesel.