According to the quality inspection results of large diameter spiral steel pipes, the large diameter spiral steel pipes are generally divided into three categories: qualified products, repaired products and waste products. How to detect?
1. Inspection of physical methods: The physical inspection method is to use some physical phenomena to measure or inspect.
2. Strength inspection of pressure vessels: pressure vessels shall undergo strength test in addition to tightness test. There are two common types: hydraulic test and pneumatic test. They can inspect the weld tightness of vessels and pipes working under pressure. The pneumatic test is more sensitive and faster than the hydraulic test. At the same time, the large-diameter spiral steel pipe after the test does not need to be drained, which is especially suitable for products with difficult drainage. However, the test is more dangerous than the hydrostatic test. During the test, the corresponding safety technical measures must be observed to prevent accidents during the test.
3. Hydrostatic test: each large diameter spiral steel pipe shall be subject to hydrostatic test without leakage. The test pressure shall be calculated according to the following formula: P=2ST/D, where S is the test stress Mpa of hydrostatic test. The test stress of hydrostatic test shall be selected according to 60% of the yield value specified in the corresponding steel strip standard.
4. Judging from the surface, that is, visual inspection, is a simple and widely used inspection method, which is an important content of finished product inspection, mainly to find defects on the weld surface and dimensional deviation. Generally, the inspection is carried out by visual observation with the help of standard templates, gauges, magnifiers and other tools. If there are defects on the weld surface, there is a possibility of defects in the weld interior.
