How to do hydrostatic test for ERW steel pipe?

Posted by zora li on December 13th, 2022

In the hydrostatic test of ERW pipe, it is often found that the crack is broken from the weld of ERW steel pipe, which indicates that the strength of the welded part is lower than that of the base metal. Through experimental analysis, it is found that in the process of removing burrs in the weld, if an internal scratch groove is formed on the inner surface of the steel pipe, the thickness of the sample in the weld can be reduced. In a tensile test, the sample breaks easily from this point.

The hydrostatic test of the water supply pipeline is a means to evaluate the final quality of the steel pipe laying. Generally speaking, we have two requirements for the hydrostatic pressure test: one is to correctly reflect the leakage of the pipeline; second, there is no problem with the pressure test, and the pressure test will not damage the interface. On the contrary, it will affect the quality of the project, or rework and retest, resulting in waste products, and even personal safety accidents will not occur.

In addition, when API SPEC 5L is used for weld tensile test, if the reinforcement is removed or the weld is retained, weld fracture often occurs. This indicates that the strength of the ERW steel pipe weld is lower than that of the base metal. There are two reasons for the analysis: one is that the strength of the welded joint of the steel pipe is lower than that of the base metal; the other is that the inner surface of the steel pipe is scraped when removing the burr in the weld. Due to the unreasonable transition between the welding position and the base metal, grooves or residual burrs will cause stress concentration, so the overall structural strength of the weld is lower than that of the base material. Therefore, the transition shape between the welded part of the steel pipe and the base metal should be optimized to ensure the overall quality of the steel pipe.