Stainless steel was widely used in industrial production with its excellent oxidation resistance, corrosion resistance and other properties. But in the marine environment, the stainless steel material was affected by the seawater environment easily and the corrosion resistant properties reduced. It was analyzed that the corrosion mechanism of stainless steel in seawater, and the influence factors of influence in seawater corrosion of stainless steel were discussed from the angle of content, salinity, dissolved oxygen and water flow rate, microbial. Finally the research situation of the current stainless steel anti-corrosion technology was discussed.

The residual strength evaluation of corroded pipeline carried out regularly was significant for guiding pipeline maintenance and operation safety. Effective Area Method, an important residual strength evaluation technique, was studied. A corrosion defect measure method was proposed, which was suitable for the Effective Area Method. The computer program was compiled according to the calculation model of Effective Area Method. The residual strength of an actual pipeline defect was evaluated by the Effective Area Method and Modified B31G respectively. The result showed that the Effective Area Method was less conservative than Modified B31G.

The growth of sulfate reducing bacteria (SRB) under different magnetic field strength was studied by using microbial method. The corrosion rate of X100 steel in simulated solution of SRB steel under different magnetic field strength was calculated by the method of weight loss. It was found that the magnetic field could inhibit the growth of SRB, and the stronger the magnetic field intensity was, the stronger the inhibition effect was; The magnetic field could inhibit the corrosion rate of X100 steel, and the corrosion rate of X100 steel first decreased and then increased with the increase of magnetic field strength. When the magnetic field strength was 5 mT, the corrosion rate was the smallest. The influence of static magnetic field on the survival rate of microbe and the corrosion rate of metals were briefly introduced. A new idea for the inhibition of microbial corrosion in pipeline was proposed.

It is of great significance to predict the long distance oil pipeline residual life for avoiding leakage accidents and saving repair costs. For the two corrosiondefect points that were dug out on one domestic refined oil pipeline, the threedimensional finite element model of ellipsoidal defect of pipelines structure based on FEA was established. According to the measured dimensions of the two defects of pipeline, the stress analysis of corroded pipelines using nonlinear analysis technique and the remaining life prediction based on plastic limit state failure criterion was also done. The results show that the remaining life of the two corrosion defects were respetively 8 and 13 years. The predicted results could provide theoretical basis for pipeline maintenance and repair.

Gas belongs to flammable and explosive hazardous gas. When the leakage of gas occurred in limited indoor space, the serious consequences would be produced. According to the characteristics of the gas leakage diffusion, firstly Gambit was established indoor gas stove nozzle dispersion physical model. Secondly CFD fluid dynamics software FLUENT was used to simulate the diffusion process of continuous leakage. Finally comparing the diffusion results under certain temperature gradient but different moisture conditions, and monitoring the specified installation area with variety of mounting points, the aim was to optimize the installation position of the alarm. The results show that the location of distance and relative humidity of indoor air were both the key factors on affecting the alarm time. For the same mounting points, relative air humidity increasing 15% would cause delaying the time of alarm nearly 6 s| under the same air relative humidity, each time the alarm was away from the leaking mouth increasing by 1metre, alarm time would lag for 4 s.

According to different damage process of natural gas pipeline leakage diffusion problems, using FLUENT software, CFD simulation model was established, and studied the different leak diameter of the effects on gas leakage diffusion area and simulated the natural gas leak and diffusion process between mountain and city terrain. The situation of wind speed changing along with the height and mass discharge rates variable with the time were taken into account and UDFs were programmed into the FLUENT to amend them. It concluded that the bigger hold can achieve the higher range, the max lower explosive limit of the high from the ground and downwind horizontal distances of diameter of 6.35 , 25.40 mm and 101.60 mm were 92 m and 322 m,122 m and 770 m, 408 m and 1291 m. When diffuses on the surface and in the soil, the 101.60 mm leak diameter had the maximum diffusion range. The biggest downwind horizontal distances were up to 80 m and 105 m respectively. This was because the gas lost a lot of turbulent energy influenced by the soil above the pipeline.

The X70 and X80 steel electrochemical specimens were soaked shortly in NS4 solution which was simulated as a typical neutral soil environment. After that, ulcerlike, loose and easilyfalling rust spots were found on them. Shallow corrosion pits occurred in larger rust spots. The electrochemical behaviors of specimens were investigated with polarization curve method and electrochemical impedance scan method. The results show that the rust spot increased corrosion trend of metals and accelerated the corrosion rate. This was due to the imperfection and separation of the early rust spots reduced the metalenvironmental polarization resistance. The roughness of the surface increased the working area of the specimens and the corrosion current.

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.

Based on the research of the practical application of two pipelines laid in one ditch in projects, according to actual projects, appropriate technical parameters were chosen and the method of numerical simulations was adopted to analyze the feature and discipline of thermal distribution of hot oil pipeline and cold oil pipeline laid in one ditch. On the basis of it, the thermal stress impact distribution along the two pipelines was respectively studied, and the variation regularity of thermal stress impact along two pipelines was obtained. Then the increase of the maximum thermal stress impact of the two pipelines laid in one ditch compared with the maximum one of the pipelines laid separately was obtained, which provided references in application of engineering design, construction, maintenance and other periods.

As the Daqing crude oil's higher viscosity impacts the quantity of mixed oil, during the process of crude oil batch transportation between the Daqing and Russia, the control equation of mixed oil was established based on the sequence mixed oil conveying mechanism. Using the finite volume method computes batch transportation of different flow velocity through CFD software. And the reason that the lower viscosity of the Daqing oil, the lower quantity of mixed oil under different flow patterns was analyzed. And the feasible suggestion was that was adding adequate amount of viscosity breaker chemical or moderate diesel oil into the Daqing crude oil nearby the interface in order to decrease the quality of mixed oil in the process of transportation.