Acceptance standard and method of spiral steel pipe

1. The acceptance principle of spiral steel pipe.

The quality inspection and acceptance of the spiral welded pipe shall be carried out by the technical quality supervision department of the supplier. The supplier must ensure that the delivered spiral welded pipe meets the requirements of the corresponding product standard. The purchaser has the right to conduct inspection and acceptance according to the corresponding product standards. Spiral welded pipes shall be submitted for acceptance in batches, and the batching rules shall comply with the provisions of the corresponding product standards. The inspection items, sampling quantity, sampling location, and test method of the spiral steel pipe shall be by the provisions of the corresponding product standards. With the consent of the purchaser, the spiral welded pipe can be sampled in batches according to the rolling root group.

2. Classification of spiral steel pipe acceptance methods.

A. Visual inspection

Visual inspection of helical tubes is a simple and widely used test method, and is an important part of finished product inspection, for defects and deviations, primarily finding weld dimensions on the surface. Usually by the naked eye, with standard models, gauges, and inspection tools such as magnifying glasses. If the weld is superficially defective, the weld defect is likely to be internal.

B, physical test method

Test methods utilize detected physical phenomena or some physical test method. Non-destructive testing methods are generally used to inspect defects in the material or the internal coil of the work. Nondestructive testing, ultrasonic testing, radiation testing, penetrant testing, magnetic particle testing, etc.

C. Spiral steel pipe hydraulic test standard

The water pressure test of each pipeline should be done without leakage, according to the test pressure Mpa S-hydrostatic pressure test, test pressure test, to calculate P=2ST/D, wherein the water pressure test is by the minimum yield zone specified in the corresponding standard Steel (Q235 is 235Mpa), 60% of people choose. Voltage stabilization time: D<508 pressure test time is less than 5 seconds, D≥508 test pressure holding time is less than 10 seconds for steel pipe welded seams, rebar head, and girth weld 4 Nondestructive testing should be X-ray or ultrasonic inspection. 100% SX-ray or ultrasonic testing shall be performed for ordinary flammable fluids conveyed to spiral seam steel pipes, and spiral welds of pipes used for general heating fluids such as water, sewage, air, steam, etc. shall be X-ray or ultrasonic flaw detection inspection (20% ).

D. Strength test of spiral steel pipe

In addition to the air tightness test, the spiral steel pipe is also tested for strength. There are two common test and coil hydrostatic test pressures. They can work in pressure testing vessels and tight pipe welds. The hydrostatic pressure test is more sensitive than the test and speed, but it is especially suitable for products with difficult drainage after the test product has no wastewater treatment. But the risk is greater than the test of the hydrostatic test. During the test, the corresponding safety technical measures must be met 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, and loose tissue, etc., can be used to test the density of the test. Intensive test methods are kerosene test, test ballast water, and flush test.

3. Treatment after the initial inspection of the spiral welded pipe

When a specific item does not meet the requirements of the product standard, the unqualified shall be picked out, and a double number of samples shall be taken from the same batch of spiral welded pipes for re-inspection of the unqualified items. If the re-inspection result (including any index required by the test of the project) is unqualified, the batch of spiral welded pipes shall not be delivered, and the re-inspection result is unqualified (including the unqualified microstructure of the initial inspection result, and the re-inspection is not allowed) The supplier can submit the steel pipe for acceptance one by one, or re-heat treatment (the number of re-heat treatment shall not exceed two times), and offer a new batch for acceptance. If the product standard does not make special provisions, the chemical composition of the spiral steel pipe shall be checked and accepted according to the smelting composition.

4. The final result of the acceptance of the spiral steel pipe.

According to the quality inspection results of the spiral steel pipe, the large-diameter spiral steel pipe is usually divided into three categories: qualified products, repaired products, and waste products. Qualified product refers to the spiral steel pipe whose appearance quality and internal quality meet the relevant standards or technical conditions for delivery acceptance; repaired product refers to the appearance quality and internal quality that do not fully meet the standard and acceptance criteria, but it is allowed to be repaired, and the standard and acceptance conditions can be met after repair. Scrap refers to the appearance quality and internal quality of the unqualified spiral steel pipe, which is not allowed to be repaired or still fails to meet the standards and acceptance conditions after repair.