Precautions for ERW steel pipe when testing water pressure

　　When the hydraulic test of the erw steel pipe is carried out, it is often found that the bursting opening is cracked from the weld of the erw steel pipe, which indicates that the strength of the welded portion is lower than that of the base metal. Through experimental analysis, it is found that if an internal scraping 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 bead is reduced, and the sample is easily broken from the tensile test.

　　The water pressure test of the water supply pipeline is the means for the final quality assessment of the erw steel pipe laying. Generally, there are two main requirements for the hydraulic pressure test: one is that it can correctly reflect the leakage of the pipeline; the other is the pressure test. No problem, nor can the interface be damaged due to pressure test, but it will affect the quality of the project, or retry the work, resulting in waste, and can not cause personal safety accidents.

　　In addition, when the weld tensile test is carried out in accordance with APISPEC 5L, it is often the case that the remaining height of the weld is removed or retained, and the weld is often broken. This indicates that the strength of the weld of the erw steel pipe is lower than that of the base metal. There are two reasons for the analysis: one is that the strength of the weld portion of the erw steel pipe is lower than that of the base material; the other is the scraping on the inner surface of the steel pipe when the burr in the weld is removed.

　　The groove or the residual burr causes the transition of the weld portion and the base material to be unreasonable, resulting in stress concentration, so that the overall structural strength of the weld portion is lower than that of the base material portion. Therefore, the transition shape of the weld portion of the ERW welded pipe and the base metal should be optimized to ensure the overall quality of the steel pipe. The hydraulic pressure test is not necessarily 1.5 times of the design pressure. For details, please refer to GB50235-2011 Industrial Metal Pipeline Construction Specification or TSG-D0001 Pressure Pipe Safety Technology Supervision Regulations - Pressure Pipeline Standard.

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