Spiral steel pipe acceptance criteria and methods

First, the principles of acceptance of spiral steel pipes:
The quality inspection and acceptance of spiral welded pipes shall be carried out by the technical quality supervision department of the supplier. The supplier must ensure that the delivery of spiral welded pipes meets the requirements of the corresponding product standards. The buyer has the right to inspect and accept the products according to the corresponding product standards. Spiral welded pipes should be submitted for acceptance in batches, and the batch rules should 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 number of rolling roots.


Second, the classification of spiral steel pipe acceptance methods:
A. Visual inspection: The visual inspection of the spiral pipe is a simple and widely used test method, which is an important part of the finished product inspection, defects, and deviations, mainly to find the weld size on the surface. Usually by the naked eye, with standard models, gauges, and inspection tools such as a magnifying glass. If the surface of the weld is flawed, the weld flaw may be internal.
B. Physical test method: The test method is to use the detected physical phenomenon or some physical test methods. In inspecting defects in materials or internal spiral tubes of work, non-destructive testing methods are generally used. Non-destructive testing Ultrasonic testing, radiation testing, penetrant testing, magnetic particle testing, etc.
C. Spiral steel pipe hydraulic test standard: There should be no leakage to do the hydraulic test of each pipeline, according to the test pressure Mpa S-hydrostatic pressure test, test pressure test, to calculate P=2ST/D, where the water pressure The test is carried out by the minimum yield strip steel (Q235 is 235Mpa) specified in the corresponding standard, and 60% of the people choose it. Pressure 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 welds, steel bar heads, and girth welds 4 Non-destructive testings should be X-ray or ultrasonic inspection. 100% SX-ray or ultrasonic testing should be done for ordinary flammable fluids transported to spiral seam steel pipes, and X-ray or ultrasonic testing should be done for spiral welded pipes used for water, sewage, air, steam, and other general heating fluids transporting pipes (20% ).
D. Spiral steel pipe strength test: In addition to the air tightness test, the spiral steel pipe is also tested for strength. There are two common test pressures and the hydrostatic test for coiled tubing. They can work on tight welds in pressure-tested vessels and pipes. The hydrostatic pressure test is more sensitive than the test and speed, but it is especially suitable for products that have difficulty draining after the test product has no wastewater treatment. But the risk is greater than the test of the hydrostatic test. When testing, it must comply with the corresponding safety technical measures to prevent accidents during test 5. Compactness test: liquid or gas-shielded welding, which is non-dense welding defects, such as penetration cracks, pores, slag inclusions Storage containers, incomplete penetration and loose tissue, etc., can be used to check the density of the test. Intensive test methods are the kerosene test, ballast water test, and flush water test.


Third, the treatment after the initial inspection of the spiral welded pipe:
When a certain item does not meet the requirements of the product standard, the unqualified ones should be picked out, and double the number of samples should be randomly taken from the same batch of spiral welded pipes for re-inspection of unqualified items. If the re-inspection result (including any index required by the project test) is unqualified, the batch of spiral welded pipes shall not be delivered, and the re-inspection result is unqualified (including the microstructure of the preliminary inspection result is unqualified, and re-inspection is not allowed) For spiral steel pipes, the supplier can submit them for acceptance one by one, or re-heat-treat (the number of re-heat-treatments shall not exceed twice), and submit a new batch for acceptance. If there is no special regulation in the product standard, the chemical composition of the spiral steel pipe shall be checked and accepted according to the melting composition.


Fourth, the final result of the acceptance of the spiral steel pipe:
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 waste products. Qualified products refer to spiral steel pipes whose appearance quality and internal quality meet the relevant standards or delivery acceptance technical conditions; reworked products refer to appearance quality and internal 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; waste products refer to spiral steel pipes whose appearance quality and internal quality are unqualified, and are not allowed to be repaired or still fail to meet the standards and acceptance conditions after repairing.