Acceptance standards and methods for spiral steel pipes

1. Principles for acceptance of spiral steel pipes: The quality inspection and acceptance of spiral welded pipes should be carried out by the supplier’s technical quality supervision department. The supplier must ensure that the delivered spiral welded pipes comply with the requirements of the corresponding product standards. The purchaser has the right to inspect and accept products according to corresponding product standards. Spiral welded pipes should be submitted for acceptance in batches, and the batch grouping rules should comply with the provisions of the corresponding product standards. The inspection items, sampling quantity, sampling locations, and test methods of spiral steel pipes shall be by the provisions of the corresponding product standards. With the consent of the purchaser, spiral welded pipes can be sampled in batches according to the rolling root number.

2. Classification of spiral steel pipe acceptance methods:
①. Visual inspection: Visual inspection of spiral steel pipe is a simple and widely used testing method. It is an important part of finished product inspection, defects, and deviations, mainly to find the weld size on the surface. Usually through the naked eye, with standard models, instruments, and inspection tools such as magnifying glasses. If the weld surface is defective, the weld defect may be internal.
②. Physical testing method: The testing method uses the detected physical phenomenon or some physical testing methods. Inspection of defects in materials or work internal spiral steel pipes is generally done using non-destructive testing methods. Non-destructive testing, ultrasonic testing, radiation testing, penetrant testing, magnetic particle testing, etc.
③. Spiral steel pipe hydraulic pressure test standards: There should be no leakage. Each pipe should be tested for hydraulic pressure. Press the test pressure Mpa S-hydrostatic test. Test pressure test to calculate P=2ST/D, where the water pressure The test was conducted by the minimum yield strip steel specified in the corresponding standards (Q235 is 235Mpa), and 60% were selected. Pressure stabilization time: D<508, the pressure test time is less than 5 seconds, D≥508 test the steel pipe welding seam, steelhead, and girth weld seam with a pressure holding time of less than 10 seconds. 4 Non-destructive testing should be X-ray or ultrasonic inspection. For ordinary combustible fluid transport to spiral seam steel pipes should be 100% SX-ray or ultrasonic test, for water, sewage, air, steam, and other general heating fluid transport pipeline spiral welds should be subject to X-ray or ultrasonic flaw detection inspection (20% ).
④. Strength test of spiral steel pipe: In addition to the air tightness test, spiral steel pipe also undergoes strength test. There are two common testing pressures and hydraulic pressures for spiral steel pipes. They can work on pressure-testing vessels and piping with dense welds. The hydrostatic pressure test is more sensitive than the test and speed, but it is particularly suitable for products that have difficulty draining water after testing the product without wastewater treatment. However, the risks are greater than hydrostatic testing. When testing, the corresponding safety technical measures must be complied with to prevent the occurrence of accidents during the test.
⑤. Compactness test: liquid or gas-shielded welding, which is not dense welding defects, such as penetration cracks, pores, slag inclusions Storage containers, incomplete penetration loose tissue, etc., can be used to test the density of the test. Intensive testing methods are the kerosene test, ballast water test, and flushing test.

3. Treatment after the initial inspection of spiral welded pipes: When a certain item does not meet the requirements of product standards, the unqualified ones should be picked out, and double the number of samples should be taken from the same batch of spiral welded pipes to conduct unqualified items. re-inspection. If the re-inspection results (including any indicator required for the test of the project) are unqualified, the batch of spiral welded pipes shall not be delivered, and the re-inspection results are unqualified (including items whose initial inspection results are unqualified for microstructure and re-inspection is not allowed) For spiral steel pipes, the supplier may submit them for acceptance one by one; or re-heat treatment (the number of re-heat treatments shall not exceed two times) and submit a new batch for acceptance. If there are no special provisions in product standards, the chemical composition of spiral steel pipes shall be inspected based on the melting composition.

4. Final results of spiral steel pipe acceptance: According to the quality inspection results of spiral steel pipes, large-diameter spiral steel pipes are usually 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; repaired products refer to appearance quality and intrinsic quality that do not fully meet the standards and acceptance requirements, but are allowed to be repaired and can meet the standards and acceptance conditions after repair. Spiral steel pipes; scrap refers to spiral steel pipes whose appearance quality and intrinsic quality are unqualified and are not allowed to be repaired or which still fail to meet the standards and acceptance conditions after repairs.