Steel-Reinforced Polyethylene Pipe: Extrusion Welding, Investigation, and Mechanical Testing

Abstract

This work presents extrusion welding with a square butt joint of V-shaped steel-reinforced polyethylene (SRPE) corrugated pipe. The SRPE pipe was welded in a single pass on the inside of the pipe. The welding temperature was controlled at 190°–200°C. The welding extruder was modified for controlling the travel speed and preheating conditions for welding. A high-density polyethylene (HDPE) rod was used as the welding filler metal, which was inserted into the extruder with a speed of 2.20 m/min. Welding progressed downhill from the overhead position with a travel speed of 3.0 cm/min. The effects of welding methods, with and without preheat conditions, on the weld quality were investigated by visual and radiographic inspections. From the results, the preheated welding condition showed complete fusion of the weld without any defects, while that of the nonpreheat exhibited a great number of voids inside the weld. The crystal structures of the preheated and nonpreheated welds were analyzed with an x-ray diffractometer and compared with the HDPE base material. From mechanical testing, the weld from the preheat condition showed a good ability to endure the tension force of 46 MPa and compressive stress of up to 0.41 MPa at 5%deflection. In addition, it was found the welded SRPE could tolerate hydrostatic pressure of up to 0.18 MPa without any water leakage when being used as a water-containing tank.