What Are the Quality Inspection Methods for Steel Pipes?

The quality inspection methods of spiral steel pipes are as follows:

1. Judging from the surface, that is, the appearance inspection: the appearance inspection of the welded joint is a simple and widely used inspection method, which is an important content of the finished product inspection, mainly to find the defects and dimensions of the weld surface of deviation. Generally, it is inspected by naked eyes and with the help of tools such as standard templates, gauges, and magnifying glasses. If there is a defect on the surface of the weld, there may be a defect inside the weld.

2. Inspection of physical methods: The physical inspection method is a method of measuring or inspecting using some physical phenomena. The inspection of internal defects of materials or workpieces is generally performed by non-destructive testing. Non-destructive testing includes ultrasonic testing, radiographic testing, penetration testing, magnetic testing, etc.

3. Strength inspection of pressure vessel: In addition to the tightness test, the pressure vessel must also undergo a strength test. There are two kinds of water pressure test and air pressure test. They can check the tightness of the welds of containers and pipes that work under pressure. The air pressure test is more sensitive and faster than the water pressure test. At the same time, the product after the test does not need to be drained. It is especially suitable for products with difficult drainage. But the risk of the test is greater than the hydrostatic test. During the test, the corresponding safety technical measures must be observed to prevent accidents during the test.

4. Tightness test: Welding containers that store liquids or gases, the non-density defects of the welds, such as penetrating cracks, pores, slag inclusions, under-welded and loose tissues, etc., can be found by the compactness test. Denseness testing methods include kerosene test, water load test, water flush test, etc.

5. Hydrostatic test: Each steel tube should be hydrostatically tested without leakage. The test pressure is calculated by pressing P=2ST/D where the S—hydrostatic test stress Mpa and the hydrostatic test stress are calculated as follows: The corresponding steel strip standard stipulates 60% of the minimum yield value (Q235 is 235Mpa). Stabilization time: D<508 test pressure retention time is not less than 5 seconds; D≥508 test pressure retention time is not less than 10 seconds.

6. Non-destructive testing: X-ray or ultrasonic inspection should be carried out on the repair welding seam of the steel pipe, the butt weld of the steel belt and the circumferential seam. The spiral welds of steel for flammable general fluid transportation should be 100% SX-ray or ultrasonic inspection, and the spiral welds of steel pipes for general fluid transportation of water, sewage, air, heating steam, etc. should be X-ray or Ultrasonic inspection spot check (20%).

According to the quality inspection results of spiral steel pipes, spiral steel pipes are generally divided into three categories: qualified products, repaired products and scrap products. Qualified products refer to spiral steel pipes whose appearance quality and intrinsic quality meet the relevant standards or technical conditions for delivery and acceptance; reworked products refer to appearance quality and intrinsic quality that do not fully meet the standards and acceptance criteria, but are allowed to be repaired, and the standards and acceptance conditions can be reached after repair. Spiral steel pipe; scrap refers to the spiral steel pipe whose appearance quality and internal quality are unqualified, and it is not allowed to be repaired or the standard and acceptance conditions are still not met after the repair. Waste products are divided into internal waste and external waste. Internal waste refers to the waste spiral steel pipe found in the foundry or foundry; external waste refers to the waste found after the delivery of the spiral steel pipe, which is usually only revealed during mechanical processing, heat treatment or use, and the economic loss caused by it is far Greater than domestic waste. In order to reduce external waste, it is best to sample and heat-treat spiral steel pipes in batches for experimental heat treatment and rough machining before leaving the factory. If possible, find potential spiral steel pipe defects in the spiral steel pipe factory, so as to take necessary remedial instructions as soon as possible.