How to check the quality of welded pipe?

Posted by zora li on April 10th, 2023

How to check the quality of welded pipe?

1) Judging from the surface, that is, visual inspection. Visual inspection of welded joints is a simple and widely used inspection method, and is an important part of finished product inspection. The inspection generally adopts the visual method, with the help of standard templates, gauges, magnifying glasses and other tools. If there is a defect on the surface of the weld, there may be a defect inside the weld.

2) Physical method test: Physical test method is to use some physical phenomena to measure or test. The inspection of internal defects of materials or workpieces generally adopts non-destructive testing methods. Non-destructive testing includes ultrasonic testing, radiographic testing, penetrant testing, magnetic testing, etc.

3) Pressure vessel strength test: In addition to the sealing test, the pressure vessel should also undergo a strength test. There are two common tests: hydrostatic test and air pressure test. Both methods check the weld tightness of pressure vessels and piping. Pneumatic testing is more sensitive and faster than hydrostatic testing. At the same time, the tested product does not require drainage treatment, which is especially suitable for products with difficult drainage. But the risk of the test is greater than that of the hydrostatic test. Corresponding safety technical measures must be taken during the test to prevent accidents during the test.

4) Densification test: For welded containers storing liquid or gas, through the densification test, it can be found that there are non-densification defects such as through cracks, pores, slag inclusions, incomplete penetration, and loose tissue in the weld. Densification test methods include kerosene test, water load test, water washing test, etc.

5) During the hydrostatic test, each q345b welded pipe shall undergo a hydrostatic test, and no leakage shall occur. The test pressure is calculated according to P=2st/D (s-hydrostatic pressure test stress MPa), and the hydrostatic pressure test stress is 60% of the minimum yield value specified in the corresponding steel strip standard (Q235 is 235mpa). Stabilization time: D<508 test holding time is not less than 5 seconds; D≥508 test holding time is not less than 10 seconds; 4 Non-destructive testing of steel pipe repair welding, steel strip butt welding, and girth welding. 100% SX-ray or ultrasonic flaw detection should be carried out for steel spiral welds conveying flammable ordinary fluids, and X-ray or ultrasonic flaw detection should be carried out for steel pipe spiral welds conveying ordinary fluids (20%) Water, sewage, air and heating steam and other fluids.