First, the principles of spiral welded steel pipe acceptance.
The quality inspection and acceptance of spiral welded steel pipes should be carried out by the supplier’s technical quality supervision department. The supplier must guarantee that the delivered spiral welded steel pipes conform to the relevant product standards. The buyer has the right to inspect and accept them according to the relevant product standards. Spiral welded steel pipes should be submitted for acceptance in batches, and the batching rules should conform to the relevant product standards. The inspection items, sampling quantity, sampling location, and test methods for spiral welded steel pipes shall be in accordance with the relevant product standards. With the buyer’s consent, spiral welded steel pipes may be sampled in batches according to the number of rolled roots.
Second, the classification of spiral welded steel pipe acceptance methods.
1. Visual inspection: Visual inspection of spiral welded steel pipes is a simple and widely used testing method. It is an important part of the finished product inspection of spiral welded steel pipes, mainly to discover the weld seam dimensions on the surface of the spiral welded steel pipe. It is usually done by visual inspection, with the aid of standard models, instruments, and testing tools such as a magnifying glass. If surface defects are found in the weld seam, the welding defects may be internal.
2. Physical Testing Methods: Testing methods utilize detected physical phenomena or various physical testing methods. For inspecting defects inside spiral steel pipes, non-destructive testing methods are generally employed. These include ultrasonic testing, radiation testing, penetrant testing, and magnetic particle testing.
3. Spiral Steel Pipe Hydrostatic Testing Standards: Each pipe should undergo a hydrostatic test without leakage. The test pressure is calculated as P=2ST/D, where the hydrostatic test is performed according to the minimum yield strength specified in the relevant standard for the steel strip (Q235 is 235 MPa), with 60% of the strips selected. Pressure holding time: For D<508, the test pressure time should be less than 5 seconds; for D≥508, the test pressure holding time should be less than 10 seconds. For welded seams, rebar ends, and circumferential welds, non-destructive testing should include X-ray or ultrasonic inspection. For ordinary flammable fluids transported to spiral steel pipes, 100% X-ray or ultrasonic testing should be performed. For spiral welds used in pipelines transporting general heated fluids such as water, sewage, air, and steam, X-ray or ultrasonic flaw detection (20%) should be performed.
4. Spiral Steel Pipe Strength Test: In addition to airtightness testing, spiral steel pipes also undergo strength testing. There are two common tests: hydrostatic testing and hydrostatic pressure testing. These tests can be performed on the pressure testing vessel and the weld seam of the pipe. Hydrostatic pressure testing is more sensitive than hydrostatic testing, but it is particularly suitable for products where drainage is difficult after wastewater treatment. However, the risk is greater than that of hydrostatic testing. During testing, appropriate safety measures must be followed to prevent accidents. Density testing: Liquid or gas shielded welding, where non-density welding defects, such as penetration cracks, porosity, slag inclusions, incomplete penetration, and loose structures, can be used to test density. Density testing methods include: kerosene testing, ballast water testing, and flushing testing.
Third, post-inspection treatment of spiral steel pipes.
If any item fails to meet the product standard requirements, the non-conforming pipes should be removed, and twice the number of samples should be randomly selected from the same batch of spiral welded pipes for retesting of the non-conforming item. If the retest result (including any index required for the test item) is unqualified, the entire batch of spiral welded pipes shall not be delivered. For spiral welded pipes with unqualified retest results (including items where the initial test result shows an unqualified microstructure and retesting is not allowed), the supplier may submit them for acceptance piece by piece, or they may undergo reheat treatment (the number of reheat treatments shall not exceed two) and be submitted as a new batch for acceptance. Unless otherwise specified in the product standard, the chemical composition of the spiral welded pipes shall be accepted according to the smelting composition.
Fourth, the final result of the spiral-welded pipe acceptance.
Based on the quality inspection results of spiral welded pipes, large-diameter spiral welded pipes are usually divided into three categories: qualified products, rework products, and scrap products. Qualified products refer to spiral steel pipes whose appearance and internal quality meet the relevant standards or delivery acceptance technical conditions; rework products refer to spiral steel pipes whose appearance and internal quality do not fully meet the standards and acceptance conditions, but are allowed to be repaired and can meet the standards and acceptance conditions after repair; scrap products refer to spiral steel pipes whose appearance and internal quality are unqualified, are not allowed to be repaired, or still cannot meet the standards and acceptance conditions after repair.
Post time: Mar-06-2026