How to detect plastic-coated steel pipes

Plastic-coated steel pipes, also known as plastic-coated pipes, steel-plastic composite pipes, and plastic-coated composite steel pipes, are based on steel pipes. A layer of plastic anti-corrosion layer or plastic anti-corrosion layer is fused to the inner surface of the steel pipe (bottom pipe) through spraying, rolling, dipping, and suction processes. A steel-plastic composite steel pipe with a plastic anti-corrosion layer fused to the inner and outer surfaces.

1. Appearance inspection: Check the appearance quality of plastic-coated steel pipes.

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 on each cross-section to measure the coating thickness at any four orthogonal points on the circumference.

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 electric spark.

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 shall 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 welds are 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. In an environment with a temperature of (20±5) ℃, during the test, the weld should be in the opposite direction of the impact surface, and the test results should Comply with the provisions of 5.9.

Plastic-coated steel pipes have excellent corrosion resistance and relatively small friction resistance. Epoxy resin-coated steel pipes are suitable for the transportation of water supply and drainage, seawater, warm water, oil, gas, and other media. Polyvinyl chloride plastic-coated steel pipes are suitable for the transportation of drainage, seawater, oil, gas, and other media. 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.