1. Acceptance principles for spiral steel pipes
The quality inspection and acceptance of spiral welded pipes shall 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
①Visual inspection
Visual inspection of spiral pipes is a simple and widely used test method and is an important part of finished product inspection, defects and deviations are mainly found on the surface of the weld size. 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.
②Physical testing method
The testing method is to utilize the detected physical phenomena or some physical testing methods. Inspection of defects in materials or internal coils of work is generally done using non-destructive testing methods. Non-destructive testing, ultrasonic testing, radiation testing, penetrant testing, magnetic particle testing, etc.
③Standards for hydraulic pressure testing of spiral steel pipes
Each pipeline should be tested for hydraulic pressure without leakage. Test pressure Mpa S-hydrostatic test, test pressure test to calculate P=2ST/D, in which the hydraulic pressure test is based on the minimum yield zone specified in the corresponding standard. Steel (Q235 is 235Mpa), 60% of people choose. 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% ).
④Strength test of spiral steel pipe
Spiral steel pipes, in addition to air tightness tests, are also tested for strength. There are two common test pressures and solenoid hydrostatic tests. 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 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 kerosene test, ballast water test, and flushing test.
3. Treatment after initial inspection of spiral welded pipes
When a certain item does not meet the requirements of the product standard, the unqualified ones should be singled out, and double the number of samples should be taken from the same batch of spiral welded pipes for re-inspection of the unqualified items. 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.
Post time: Oct-30-2023