Hydrostatic test of erw tube

In the hydrostatic test of erw tube, it is often found that the bursting opening breaks from the weld of the erw tube, which indicates that the strength of the weld site is lower than that of the base metal. Through experimental analysis, it has been found that if an internal scratch groove is formed on the inner surface of the steel pipe during the removal of the burr in the weld, the wall thickness of the sample at the weld site is reduced. In the tensile test, the sample can easily break from this point. .

The water pressure test of the water supply pipeline is the means for the final quality assessment of the erw tube laying. Generally, we have two requirements for the hydrostatic pressure test: First, it must be able to correctly reflect the pipeline leakage; second, pressure test when there is no problem, nor can the interface suffer damage due to pressure test. Instead, it will affect the quality of the project, or rework to retry, resulting in waste, and even no personal safety accident.

In addition, when the weld seam tensile test was performed in accordance with APISPEC 5L, the residual height was selected to remove or retain the weld seam, and fractures from the weld seam often occurred. This shows that the strength of erw tube welds is lower than that of the base metal. There are two reasons for the analysis: First, the strength of the erw tube weld joint is lower than that of the base metal part; the second is the scraping of the inner surface of the steel pipe when removing the burr in the weld. Grooves or residual burrs cause stress concentration due to unreasonable transitions between the weld site and the base metal, so that the overall structural strength of the weld seam is lower than that of the base material. Therefore, the transition shape of the weld site of the erw tube and the base metal should be optimized to ensure the overall quality of the steel pipe.