Plastic-coated steel pipes not only have the advantages of steel pipes such as high strength, easy connection, and resistance to water flow impact, but also overcome the shortcomings of steel pipes that are prone to corrosion, pollution, and scaling when exposed to water, as well as the low strength and poor fire-fighting performance of plastic pipes. The design life can reach 50 Years. The main disadvantage is that bending is not allowed during installation. During thermal processing, electric welding, and cutting, the cutting surface should be painted with non-toxic room-temperature curing glue provided by the manufacturer.
1. Appearance inspection: Visually inspect the appearance quality of plastic-coated steel pipes. The test results should comply with the provisions of 5.1.
2. Thickness measurement: Take two cross-sections of different lengths from both ends of the plastic-coated steel pipe, and use an electromagnetic thickness gauge to measure the coating thickness at any four orthogonal points on the circumference at each cross-section. The test results should comply with the 5.4 Regulation.
3. Pinhole test: The length of the pipe section specimen is about 1000mm. Use an electric spark leak detector to check the steel pipe coating under the specified test voltage. The coating thickness is not greater than 0.4mm. The test voltage is 1500 V. The coating thickness is greater than 0.4mm, test voltage is 2000 V. Check whether there is any spark generated. The test results should comply with the provisions of 5.5.
4. Adhesion test: The adhesion test is carried out by 7.4.2 in CJ/T 120-2008, and the test results should comply with the provisions of 5.6.
5. Bending test: Bending test is carried out on coated steel pipes with DN≤50mm. The length of the pipe section specimen is (1200±100) mm. In an environment where the temperature is (20±5) ℃, the radius of curvature is 8 times the nominal diameter of the steel pipe, the bending angle is 30o, and the pipe is bent on a pipe bending machine or mold. During the bending test, there is no filler in the pipe, and the weld is located on the side of the main bending surface. After the test, cut the specimen open from the middle of the bending arc and check the inner coating. The test results should comply with the provisions of 5.7.
6. Flattening test: Flattening test is conducted on coated steel pipes with DN>50 mm. The length of the pipe section specimen is (50±10) mm. In an environment with a temperature of (20 ± 5) ℃, place the specimen between two flat plates, and gradually compress it on the pressure testing machine until the distance between the two flat plates is four-fifths of the outer diameter of the specimen. Apply coating when flattened. The steel pipe weld is perpendicular to the direction of load application. After the test, check the inner coating and the test results should comply with the provisions of 5.8.
7. Impact test: Cut a sample of about 100 mm in length from any position of the coated steel pipe, conduct an impact test by regulations at a temperature of (20±5) ℃, and observe the damage to the inner coating. During the test, the weld should be in the opposite direction to the impact surface, and the test results should comply with the provisions of 5.9.
8. Vacuum test: The length of the pipe section specimen is (500±50) mm. Use appropriate measures to block the inlet and outlet of the pipeline. Gradually increase the negative pressure from the inlet to 660 mm of mercury and maintain it for 1 minute. After the test, check the inner coating. The test results shall comply with the provisions of 5.10.
9. High-temperature test: The length of the pipe section specimen is (100±10) mm. Place the specimen in a constant temperature box, raise the temperature to (300±5) ℃, and keep the temperature constant for 1 hour. Then take it out and cool it to normal temperature naturally. After the test, take out the test piece and inspect the inner coating (the appearance is allowed to become darker or darker). The test results should comply with the provisions of 5.11.
10. Low-temperature test: The size and length of the pipe section specimen are (100±10) mm. Place the specimen in a low-temperature box, cool it to (-30±2) ℃, and keep it constant for 1 hour. Then take it out and place it at a temperature of (20 ±5) ℃ environment (4 ~ 7) h. After the test period, take out the test piece to check its inner coating, and conduct an adhesion test according to the provisions of 6.4. The test results shall comply with the provisions of 5.12.
11. Pressure cycle test: The length of the pipe section specimen is (500±50) mm. Use appropriate measures to block the inlet and outlet of the pipe and connect it to the hydraulic supply system. Fill it with water to eliminate air, and then perform 3000 times from (0.4 ±0.1) Alternating water pressure test from MPa to MPa, the period of each test shall not be greater than 2 s. After the test, check the inner coating and conduct an adhesion test according to the provisions of 6.4. The test results shall comply with the provisions of 5.13.
12. Temperature cycle test: The length of the pipe section specimen is (500±50) mm. The specimen is placed in each temperature condition for 24 hours in the following order: (50±2)℃; (-10±2)℃; (50±2)℃;(-10±2)℃;(50±2)℃;(-10±2)℃. After the test, the specimen is placed in an environment with a temperature of (20±5) ℃ for 24 hours. The condition of the inner coating is checked, and the adhesion test is performed according to the provisions of 6.4. The test results shall comply with the provisions of 5.14.
13. Warm water aging test: The length of the pipe section specimen is about 100 mm. The exposed parts at both ends of the pipe section should be treated accordingly. The pipe section should be soaked in distilled water at (70±2) ℃ for 30 days. After the test, take it out naturally. Cool to normal temperature and check the inner coating of the specimen. The test results should comply with the provisions of 5.15.
Post time: Apr-23-2024