1. Inspection and inspection of submerged arc steel pipes shall be carried out by the supplier’s technical supervision department.
2. The supplier must ensure that the delivered submerged arc steel pipes comply with the regulations of the corresponding product standards. The purchaser has the right to inspect and inspect according to corresponding product standards.
3. Submerged arc steel pipes should be submitted for inspection in batches, and the batching rules should comply with the rules of the corresponding product standards.
4. The inspection items, sampling quantity, sampling locations, and test methods of submerged arc steel pipes shall be by the provisions of the corresponding product standards. With the consent of the buyer, hot-rolled seamless submerged arc steel pipes can be sampled in batches according to the rolling root number.
5. When the test results of submerged arc steel pipes do not meet the requirements of product standards, the unqualified ones should be singled out, and double the number of samples should be taken from the same batch of submerged arc steel pipes to test the unqualified items. recheck. If the re-inspection results (including any of the indicators required by the project test) are unqualified, the batch of submerged arc steel pipes shall not be delivered. If the following inspection items fail the initial inspection, re-inspection is not allowed: a. There are white spots in the low-magnification tissue; b. Microstructure.
6. For submerged arc steel pipes that fail to pass the re-inspection results (including items whose microstructure fails to pass the initial inspection results and are not allowed to be re-inspected), the supplier may submit them for inspection one by one; or re-heat treatment (the number of re-heat treatments shall not exceed two times) ), submit a new batch for inspection.
7. If there are no special provisions in the product standards, the chemical composition of the submerged arc steel pipe shall be tested according to the smelting composition.
In the construction of long-distance pipelines, line steel pipes account for a considerable proportion. Under normal circumstances, line steel pipe investment accounts for about 35% to 40% of the total project investment. How to choose pipes with reasonable prices and high performance is particularly important. Reasonable selection of pipes has a great impact on saving construction investment, facilitating construction, and operating the pipeline system. Long-distance oil and gas pipeline steel pipes include high-frequency straight seam resistance welded steel pipes, spiral submerged arc welded steel pipes, and submerged arc steel pipes. The diameter range of high-frequency straight seam resistance welded steel pipes is limited. In China, it is generally limited to steel pipes within Φ406.4mm. In Japan, the largest pipe diameter has reached Φ508mm. There are two forms of pipe making for large diameters: spiral submerged arc welding and straight seam submerged arc welding. Spiral welded steel pipes have many shortcomings due to their pipe-making process and forming characteristics, and their proportion in long-distance pipelines is gradually declining. In foreign countries, especially in many European and American countries, the use of spiral submerged arc welded steel pipes as main steel pipes for lines has been banned.
Submerged arc steel pipes are being widely used in long-distance oil and gas pipelines with their unique advantages. Their advantages are as follows:
1. There is no unwinding process, so the base material will have fewer pits and scratches.
2. Staggered edges, seams, pipe diameter, and circumference are easy to control and weld.
3. After the stress is relieved by pipe expansion, there is no residual stress.
4. Since it is a straight weld and the weld is short, the probability of defects is small.
5. After diameter expansion, the geometric dimensional accuracy of the steel pipe is improved, which greatly facilitates on-site welding.
6. The weld is a straight line, which has little impact on the coating of anti-corrosion materials.
Post time: Oct-09-2023