Reinforcement test of epoxy-filled steel sleeves for girth weld defects of X80 pipelines

In order to verify the applicability of epoxy-filled steel sleeves for reinforcement of the girth weld defects in X80 steel pipelines, X80 pipe fittings with 1 016 mm diameter were selected as the specimens and on the specimens two girth welds with same defects were set by manual welding. Definitely, one of the welds was reinforced with an epoxy-filled steel sleeve, while the other was not. Then, the full-scale mechanical tests were performed under the internal pressure, fluctuation pressure and the coupling effect of internal pressure and bending moment for the above two defective girth welds with/without reinforcement. In addition, the failure mode, bearing capacity and deformation performance of the two specimens were compared and analyzed. The results show that the hoop and axial stresses of the girth weld defects reinforced by the epoxy-filled steel sleeve under the operating pressure is reduced, and the sleeve shares 47% of the internal pressure. The stress of the girth weld defects reinforced by the epoxy-filled steel sleeves under the cyclic fluctuating pressure is kept unchanged, which indicates that the stress level of the sleeve reinforced girth weld defects is stable, without changing with the fluctuation of the pressures. In addition, under the coupling effect of the internal pressure and the bending moments, the failure mode of the unreinforced pipeline is overall fracture of the weld section, while the failure mode of the reinforced pipeline is local buckling failure in the pressure region after the yield of the steel in the tensile region, which indicates that the epoxy-filled steel sleeves increase the bending capacity of the pipelines and reduce the bending deflection. In brief, the research results can provide a reference to the engineering application of reinforcing the defective girth welds of X80 pipelines with epoxy-filled steel sleeves.