The Design Of ECT System For Wax Deposition Detection Inside The Nonmetallic Pipeline

In our country, most of the oil contains lots of wax and its viscosity is high.During the oil delivery in the nonmetallic pipelines, the oil releases its heat to theoutside continually, which can lead to wax deposition. And the phenomenon of waxdeposition inside the pipeline casuses the increment of energy consumption and thatthe oil maybe cooled and concreted, which results in the decrement of transportefficiency and the service life of the pipeline. Therefore, in order to solve this problemof wax deposition detection, a kind of detection technique was presented andresearched based on the electrical capacitance tomography (ECT). The main researchworks include:(1) The research of the ECT sensor designThe simplified model of ECT sensor was built according to the fundamentalprinciple of the ECT sensor called fringe capacitance. A series of double-platerectangular proximity capacitance sensors were designed, then the design of thesensor parameters and the performance evaluation were analyzed according to theexperiments. In order to analyze multiple factors and parameters which influencingthe performance of the sensor, the method of orthogonal test was introduced. Thismethod can ruduce the number of the experiments effectively. The results can list theoptimal combination of all the parameter combinations, and the importance ofparameters affecting sensor performance was analyzed at the same time, all theparameters can be analyzed simultaneously. A semi-analytical model for thedouble-plate rectangular proximity capacitance sensor was presented based on theeffective theory. The effect of the measured capacitance value caused by thegeometric parameters of the simplied ECT sensor was ananlyzed quantitatively, whichcan be used to provide guidance to the design of the sensors of this type.(2) The design of the hardware of the ECT systemFirstly, each module circuit was analyzed and designed, including the circuit ofexcitation source, capacitance measurement, phase sensitive demodulation andmulti-channel switch. Then the relevant simulation and experiments of each modulecircuit were designed, and the availability and accuracy of each module circuit wereverified. Finally, the capacitance can be measured, which can provide data for thesubsequent imaging. (3) The research of detection of the wax deposition inside nonmetallic pipelineThe physical model was built by using the finite elements software COMSOL,the sensitivity field of the detection area was calculated at the same time. Thepipelines with different kind of wax deposition inside were designed, then thecapacitances formed among the ECT sensor were measured. Finally, the imaging ofthe wax deposition inside the nonmetallic pipelines was realized by using the linearback projection algorithm. The results of simulation and actual experiments show thatthe ECT system can be applied in the detection of wax eposition inside thenonmetallic pipelines effectively.