Influence of the artificial defect on the flexible pipeline twist angle

To establish the dependence of the change in the values of the twisting angle of the flexible pipeline on the internal water pressure and the defect length, which is directed along and across the axis of the sleeve. Experimental studies were conducted in two stages. At the first stage, the methodology and plan of the experiment were developed, the factors and their values were determined, and experimental studies were conducted. The limits of variation in the area of factor spaces were established based on the basic analysis of a priori information. The length of the defect was 0, 50 and 100 mm. The pressure values in the sleeve were 0.2, 0.4 and 0.6 MPa. Adequacy of the obtained regression equations was checked using Fisher's test. At the second stage, the analysis of the research results was carried out and the numerical values of the factors that most affect the change in the value of the twisting angle of the sleeve were established. According to the results of experimental studies, the dependences of the change in the twisting angle of the flexible pipeline on the internal water pressure and the length of the defect were obtained. It was established that the dependence of the previously mentioned factors is close to linear. The largest discrepancy in the maximum sleeve twist angle – 21% was observed at pressure values of 0.4 MPa. The research was limited to only two factors: the defect length and the pressure in the middle of the sleeve. Such factors as the degree of wear of the sleeve, the type of sleeve and the number of defects on the test sample were not taken into account. The obtained results can be used during the development of a new method of testing flexible pipelines, which will allow to establish hidden defects in them. For the first time, the dependence of the influence of the size and direction of the defect on the reinforcing frame of the pressure fire hose on the value of its twist angle at constant internal pressure indicators was established.