Finite Element Analysis to the Effect of Thermo-Mechanical Loads on Stress Distribution in Buried Polyethylene Gas Pipes Jointed by Electrofusion Sockets, Repaired by PE Patches

Abstract

Polyethylene (PE) gas pipes can be jointed together by electrofusion PE fittings, which have sockets that are fused onto the pipe. Additionally, electrofused PE patches can be used to repair defected pipes. When these pipelines are buried under the ground, they can experience sever local stresses due to the presence of pipe joints, which is superimposed on the other effects including the soil-structure interaction, traffic load, soil’s column weight, a uniform internal pressure, and thermal loads imposed by daily and/or seasonal temperature changes. The present contribution includes two cases. At first, stress variations in buried polyethylene gas pipe and its socket due to the aforementioned loading condition is estimated using finite element. The pipe is assumed to be made of PE80 material and its jointing socket material is PE100. Afterward, the effects of aforementioned thermo-mechanical loads on the stress distribution in patch repaired buried pipes are well investigated. The soil physical properties and the underground polyethylene pipe installation method are based on the American association of state highway and transportation officials and American society for testing and material standards. The computer simulation and analysis of stresses are performed through the finite element package of ANSYS Software. Stress concentrations can be observed in both components due to the presence of the socket or the repair patch. According to the results, the electrofusion sockets can be used for joining PE gas pipes even in hot climate areas. The maximum values of these stresses happen to be in the pipe. Also, the PE100 socket is more sensitive to a temperature drop. Additionally, all four studied patch arrangements show significant reinforcing effects on the defected section of the buried PE gas pipe to withstand applied loads. Meanwhile, the defected buried medium density polyethylene (MDPE) gas pipe and its saddle fused patch can resist the imposed mechanical and thermal loads of +22 °C temperature increase.

Calculations of Electrodynamic Forces in Three-Phase Asymmetric Busbar System with the Use of FEM

“…Other authors used experimental methods to check the reliability of busbar contacts and predicted the contact state on the basis of theoretical models [19,20]. Therefore, considering the effects of electrodynamic forces, temperature rise, and other factors, such as mechanical strength and the effect of a short circuit conditions on the busbar is analyzed [21][22][23].…”

“…In particular cases during a short circuit electrodynamic forces reach such high values that their impact on a given electrical system can even lead to mechanical damage and deformation of the busbars. The dependencies (Equations (20), (22), and (25)) show that during electrodynamic forces presence, the average current circuit is subjected to the greatest stress. This is due to the fact that in a system in which the busbars are arranged symmetrically with respect to the middle current circuit, the interaction of the external busbars is slightly smaller due to the greater distance.…”

Numerical and Experimental Investigation of the Effect of Traffic Load on the Mechanical Characteristics of HDPE Double-Wall Corrugated Pipe

“…Previous studies have focused on the circumferential stress and changes in the diameter of the flexible pipe to indicate the deformation of the pipe [9,16,23,51]. Compared with the real stress, the von-Mises stress comprehensively considers the deformation of materials in multiple directions, and the assessment of the ductile failure of pipes is more accurate; thus, it is reasonable to take the Von-Mises stress as a parameter that indicates the deformation of the pipe [52][53][54]. When the corrugated pipe is simplified as a straight-walled pipe, the circumferential and axial stress distribution of a particular section of the corrugated pipe cannot be obtained, so the Von-Mises stress is more suitable than the real stress to define the deformation of the pipe.…”

Finite Element Analysis of Polyethylene Pipe with Elliptical Hole Supported by Saddle Fusion Patch with Fin

“…Damage to PE pipe can be in the form of cracks, which eventually form holes on the PE pipe surface. In previous research done by Khademi et al [4] , It is assumed that the damage to the pipe surface caused by cracks has the shape of an elliptical hole, and patching methods make the repair. The saddle fusion patch method has the most significant effect on maximum stress distribution, reducing the patched area [5].…”