| The development and application of marine resources need high-quality marine equipment as a guarantee.With our country's attention to marine equipment,pipelines have been greatly applied.However,the seawater contains the rich in corrosion factors,microorganisms and sediment,which cause seriously the local corrosion of the pipeline.In the thesis,a pipeline erosion corrosion apparatus has been designed independently and the B10 tube as the research object was carried on corrosion experiment.The details are as follows:(1)Aiming at the high temperature,high humidity and high salt environment in the South China Sea,a pipeline erosion corrosion apparatus with controllable temperature and flow rate has been developed and designed.The liquid phase of the device is single-phase flow or solid-liquid two-phase flow.It can be used to test straight pipe section,welded pipe section and elbow section.The branch pipeline is equipped with a test tube.The diameter of the test tube can be used in the range of 40 mm to 100 mm.Based on the design requirements of flow rate,the total flow rate of the device is determined,and then the centrifugal pumps,solenoid valves,water tanks and other types of calculation are selected,and the pipeline erosion corrosion apparatus is manufactured and installed.(2)Based on the general design scheme,the control system was designed to control the temperature and velocity using programmable logic controller(PLC)as a main control unit,and PID algorithm was used to control temperature and velocity by PT100 and ultrasonic flowmeter respectively,the action of the actuator was controlled by A/D module and D/A module,the operating state of control system was monitored by touch screen.GX-WORK2 software was used to write the control program,and Easy Builder Pro software was used to write the upper computer operation interface.The test results show that the flow velocity range of the DN50 test tube is 0 m/s to 5 m/s,the DN80 test tube is 0 m/s to 3 m/s,the DN100 test tube is 0 m/s to 2 m/s,and the temperature regulation range is from room temperature to 60?.The temperature control precision can reach-0.5?to + 0.8?,and the flow velocity control precision can reach ±0.1 m/s.(3)In order to optimize the length of test tube and reduce the size of branch pipeline,simulation analysis of test tube was carried out to determine the unstable erosion length.The simulation results show that with the increase of temperature(30?,40?,40?,60?),the change of cavitation volume fraction is not obvious or unchanged,and the erosion rate shows a trend of decreasing,increasing and decreasing gradually;with the increase of flow velocity(2m/s,3m/s,4m/s,5m/s),the cavitation volume fraction increases gradually,and the erosion rate increases gradually.The simulation results of erosion instability length at different flow velocities are 1.7%,1.7%,1.5% and 1.4%,respectively.Therefore,the design of the connection mode of the different diameter pipe of a pipeline erosion-corrosion apparatus is reasonable,the shortest length of the test tube should be 300 mm to 500 mm,after the unstable region of the test tube is removed,there is a residual of the length of the test tube for erosion analysis,which it provides theoretical basis for the analysis of corrosion of test tube.(4)In order to application the pipeline erosion corrosion apparatus,the erosion corrosion test of B10 tube was carried out on the experimental device,and analyzed corrosion of B10 tube at different erosion time(30 min,1 h,2 h,4 h),different temperature(30?,40?,50?)and different flow velocities(1m/s,2m/s,3m/s,4m/s).The results show that with the increase of erosion time,flow rate and temperature,the surface oxides of B10 gradually increased.With the increase of temperature,the oxidation degree of B10 decreased.When the temperature is 40? and flow rate is 3 m/s,the erosion marks are most obvious. |
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