Pipe sand holes, weld sand holes

The so-called \"sand hole\" is merely a colloquial term for a through-leakage defect in pipes or welds; generally, the area where the leakage occurs appears as a small hole or crack, which is why it is vividly called a sand hole. There are many causes, and generally they include the following: 1. Internal defects in the material itself, such as shrinkages and cracks, or weld defects such as pores and cracks in the welds, which can form through-holes internally and lead to leakage. 2. Starting from internal defects, internal stress points or local weak areas are formed; corrosion exacerbates these defects, eventually leading to the creation of through-going defects that cause leakage. 3. Due to corrosion, through defects form locally. 4. Due to the erosion by the medium, through defects are formed locally. Especially at the points where the flow direction of the medium changes or where vortex flow is likely to occur, such as valves, the bottom of tees, or the bilateral shoulders (where the medium enters from the branch pipes). 5. Furthermore, sand holes may arise again during the process of repairing defects, especially when welding under pressure; the pressurized medium can create voids as the weld droplets solidify. If proper welding techniques are not followed during repair, and the weld is not properly hammered or riveted to eliminate these voids, they will remain as defects within the weld, potentially becoming sources of leaks in the future. In short, “sand hole” is just a colloquial term that is not accurate; it should not be understood literally. Some sand holes may appear to be small holes on the surface, but they might actually contain cracks inside ； Some manifest as trachoma, but the area may already be significantly thinned out. Therefore, sand holes are merely a symptom; when dealing with them, it’s not enough to simply carry out weld repairs. If conditions permit, thickness testing or other forms of inspection should be conducted on the affected area. If no special medium is available, a grinder can be used to polish the surface in order to identify the source of the internal defects. It’s important to carefully analyze the reasons behind the formation of sand holes and to implement effective measures to prevent potential problems from arising.