Spiral Steel Pipe

Before spiral steel pipes shall be subject to mechanical performance, flattening and flaring tests and meet the stipulations of standards before leaving the factory. The quality inspection methods for spiral steel pipes are as follows:
1. Surface observation, i.e. appearance inspection. As a simple but widely applied inspection method as well as an important content of inspection for finished products, appearance inspection of weld joints is mainly used for identifying defects and dimensional deviations on the surface of weld joints. Generally speaking, appearance inspection is conducted by naked eyes with the help of standard templates, gauges and magnifying glass. If there are defects on the surface of weld joints, it is estimated that there are defects inside such weld joints.
Spiral Steel Pipe - Hebei Spiral Steel Pipe - Spiral Steel Pipe Factory
2. Physical inspection: a method used for measurement or inspection by using some physical phenomena. Usually, NDT is used for detecting internal defects of materials or workpieces. NDT includes ultrasonic inspection, radiographic testing, penetrant testing, magnetic testing, etc.
3. Pressure vessel strength test: pressure vessels shall also be subject to the strength test, in addition to the tightness test. Hydrostatic test and air pressure test are common. The welding tightness of vessels and pipes that work under pressure can be inspected; the air pressure test is more sensitive and faster than the hydrostatic test. In the meanwhile, there is no need for drainage treatment against tested products that are especially suitable for the situations with difficulty of drainage. However, this test is more dangerous than the hydrostatic test. During the test, corresponding safety technical measures shall be taken to prevent accidents.
4. Tightness test: as regards welding vessels for storing liquids or gas, the tightness test can be used for identifying non-tightness defects of weld joints, such as penetrated cracks, pores, slag inclusion, incomplete weld and loose structures. Tightness test methods include kerosene test, band water test, water flushing test, etc.
5. Hydrostatic test: each steel pipe shall be leak-free after the hydrostatic test. The test pressure shall be calculated with the following formula: P=2ST/D (S- the test stress (Mpa) of the hydrostatic test). The test stress used in the hydrostatic test shall be 60% of the small yield value (Q235 is 235MPa) as stipulated in the corresponding steel band standard. Pressure holding time: D is less than 508, the pressure holding time in the test shall be no less than 5s; the D508 test pressure shall be no less than 10s. Repair of steel pipe weld joints, butt weld and circumferential weld shall be subject to X-ray or ultrasonic inspection. Spiral weld joints of all the steel pipes for conveying ordinary combustible fluids shall be subject to x-ray or ultrasonic flaw detection. Spiral weld joints of all the steel pipes for conveying ordinary fluids like water, sewage, air and heated steam (20%) shall be subject to x-ray or ultrasonic flaw detection in the form of spot check.