Research On In-Line Inspection Of Small-Diameter Pipelines With Ultrasonic Pigs And Measurement Technology

With the view to the general oil-gathering pipeline for oil and gas fields, the correlative theories and technology have been studied extensively. The main research respects are as following in this thesis:1. Aimed at the in-line inspection of small-diameter pipelines, the modules have been designed in I-shape. The distance wheel system is adopted the mouse principle by its simple and reliable characteristics, and the force-enhanced structure is added on arms so that the precision and reliability of the distance count are improved.2. Emphasized on the influence of planar reflector on focusing beams, the model of immersion focusing ultrasonic field based on focusing beams reflected by planar reflector is given. And it has been studied on immersion testing the cylindrical objects with the single focus transducer, which is available for small-diameter pipelines.3. Introduced the coefficient of sweep zone, the condition of complete coverage of circumference for the pipeline has been extensive studied for a few types of sensor carriers, such as multi sensor array, multi rotating sensor array and single sensor rotating reflector.4. The data acquisition and data flow for various sensor carriers are analyzed systematically, and the calculation models are put forward. The model of quantification of wall-loss defects for in-line inspection with ultrasonic pigs has been established. And inspection data can be pretreated with this model, compressed with DPCM technique and treatd by DSP instruments.5. Turning to the corroded pipelines, the safety evaluation methods based on fracture mechanics, reliability analysis and Fuzzy synthetic evaluation are analyzed. It is suggested that the threshold for non-destructive pipelines should be determined by Fuzzy synthetic evaluation method.6. The laboratory immersion testing has been shown that the sensor carrier for single sensor rataing reflactor is available for in-line inspection of small-diameter pipelines at the proper sampling frequcy and system amplititude.