Spiral pipe, also known as spiral steel pipe or spiral welded pipe, is a low-carbon structural steel or low-alloy structural steel strip rolled into a tube blank at a certain helical angle (called a forming angle), also known as a spiral tube or a spiral body. The outer diameter of the spiral tube is about 30 nanometers, the inner diameter is about 10 nanometers, and the pitch between adjacent spirals is about 11 nanometers.
What are the methods for identifying whether the quality of large-diameter spiral welded pipes is up to standard?
1. Inspection by physical method: physical inspection method is a method of measuring or inspecting by using some physical phenomena.
2. Strength test of the pressure vessel: In addition to the tightness test, the pressure vessel also needs to undergo a strength test. Commonly there are two kinds of hydrostatic test and air pressure test. They both inspect the tightness of welds in vessels and pipes operating under pressure. The air pressure test is more sensitive and faster than the hydraulic test. At the same time, the large-diameter spiral welded pipe after the test does not need to be drained, which is especially suitable for products with difficult drainage. However, the risk of the test is greater than that of the hydrostatic test. During the test, the corresponding safety technical measures must be followed to prevent accidents during the test.
3. Hydrostatic test: Each large-diameter spiral welded pipe should be subjected to a hydrostatic pressure test without leakage. The test pressure is calculated as follows: P=2ST/D.
In the formula, S—the test stress Mpa of the hydrostatic test, and the test stress of the hydrostatic test is selected according to 60% of the yield value specified in the corresponding steel strip standard.
4. Judging from the surface, that is, the appearance inspection, is a simple and widely used inspection method. It is an important part of the finished product inspection. It is mainly to find defects on the weld surface and dimensional deviations. Generally, it is inspected by naked eyes, with the help of standard templates, gauges, magnifying glasses and other tools. If there is a defect on the surface of the weld, there is a possibility of a defect inside the weld.