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plastic-coated steel pipes, also known as plastic-coated pipes, steel-plastic composite pipes, and plastic-coated composite steel pipes, use steel pipes as the substrate and weld a layer of plastic anti-corrosion layer or steel-plastic composite steel pipe with plastic anti-corrosion layer welded on 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 to measure the coating thickness at any four points perpendicular to the circumference of each cross-section.
3. pinhole test: the length of the pipe section test piece is about 1000mm, and the steel pipe coating is inspected under the specified test voltage with an electric spark leak detector. 0.4mm, the test voltage is 2000 v. check for sparks.
4. adhesion test: the adhesion test shall be carried out according to 7.4.2 of cj/t 120-2008, and the test results shall meet the provisions of 5.6.
5. bending test: dn≤50mm coated steel pipe is subjected to a bending test. the length of the pipe section test piece is (1200±100) mm. in an environment with a temperature of (20±5) ℃, take 8 times the nominal diameter of the steel pipe as the radius of curvature, and the bending angle is 30o, and bend it on a pipe bender or mold. during the bending test, there is no filler in the tube, and the weld is located on the side of the main bending surface. after the test, cut the test piece from the middle of the curved arc to check the inner coating. the test results should meet the requirements in 5.7.
6. flattening test: the coated steel pipe with dn>50 mm is subjected to the flattening test. the length of the pipe section test piece is (50±10) mm. in an environment with a temperature of (20±5) ℃, place the test piece 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 test piece. the steel pipe weld is perpendicular to the direction of load application. after the test, check the inner coating and the test result should meet the requirements in 5.8.
7. impact test: cut a sample with a length of about 100 mm from any position of the coated steel pipe, and in an environment with a temperature of (20±5) °c, the weld should be in the opposite direction of the impact surface during the test, and the test result should be comply with the provisions of 5.9. plastic-coated steel pipe has excellent corrosion resistance and relatively small frictional resistance. epoxy resin-coated steel pipe is suitable for the transportation of water supply and drainage, seawater, warm water, oil, gas, and other media, and pvc-coated steel pipe is suitable for the transportation of drainage, sea water, oil, gas, and other media. plastic-coated steel pipe not only has the advantages of high strength, easy connection, and water impact resistance, but also overcomes the shortcomings of steel pipes such as easy corrosion, pollution, scaling, low-strength plastic pipes, and poor fire performance. the design life can reach 50 years.