How To Detect The Quality Of Spiral Steel Pipes?

Surface inspection: This involves visual examination of the welded joints of spiral steel pipes. It's a simple and widely used inspection method, primarily aimed at detecting defects and dimensional deviations on the surface of welds. Typically, this is done through visual observation aided by tools such as standard templates, gauges, and magnifying glasses. Defects on the surface of welds may indicate internal flaws within the weld.

Physical methods: These methods utilize physical phenomena for measurement or inspection. Non-destructive testing methods are commonly employed to inspect the internal defects of spiral steel pipes materials or components. Techniques such as ultrasonic testing, radiographic testing, penetrant testing, and magnetic particle testing are utilized.

Pressure vessel strength testing: In addition to sealing tests, pressure vessels undergo strength tests. Common tests include hydrostatic tests and pneumatic tests. These tests assess the integrity of welds in vessels and pipelines under pressure. Pneumatic testing is more sensitive and quicker than hydrostatic testing, and products tested with pneumatic methods don't require draining afterward, making it particularly suitable for products where drainage is difficult. However, pneumatic testing carries greater risks than hydrostatic testing. Safety measures must be strictly followed during testing to prevent accidents.

Tightness inspection: Welded containers for storing liquids or gases may exhibit non-tightness defects in their welds, such as penetrating cracks, gas porosity, slag inclusion, incomplete penetration, and loose structures. These defects can be detected through tightness testing methods such as kerosene testing, water immersion testing, and water flushing testing.

Hydrostatic test: Each spiral steel pipes should undergo a hydrostatic pressure test without leakage. The test pressure is calculated according to the formula P=2ST/D, where S is the test stress (in MPa) of the hydrostatic test, and it is selected as 60% of the minimum yield strength specified in the relevant steel strip standard (e.g., Q235 is 235 MPa). Stabilization time: For D<508, the pressure holding time should be no less than 5 seconds; for D≥508, the pressure holding time should be no less than 10 seconds.

Non-destructive testing: Weld repairs on steel pipe welds, end-to-end welds of steel strips, and circumferential welds should undergo X-ray or ultrasonic testing. Spiral welds of steel pipes for conveying flammable fluids should undergo 100% SX-ray or ultrasonic testing. For steel pipes used for conveying common fluids such as water, sewage, air, and heating steam, spiral welds should undergo X-ray or ultrasonic testing sampling (20%).

Based on the quality inspection results of spiral steel pipes, they are typically classified into three categories: qualified products, repairable products, and scrap. Qualified products refer to spiral steel pipes whose external and internal quality meets relevant standards or delivery acceptance technical conditions. Repairable products are those whose external and internal quality does not fully meet standards and acceptance criteria but are allowed to be repaired, and after repair, they meet the standards and acceptance criteria. Scrap refers to spiral steel pipes with unacceptable external and internal quality, which cannot be repaired or, if repaired, still fail to meet the standards and acceptance criteria.