First, construction and installation of plastic-coated steel pipes
1) It should be carried out by the “Technical Code for Plastic-coated Composite Pipe Pipe Engineering for Building Water Supply” CECS125:2001.
2) The following construction machines and tools should be used for plastic-coated steel pipes:
(1) Cutting should be done with a metal saw;
(2) Grooving should be done with a special groove rolling machine;
(3) Bending should be done with a pipe bending machine;
(4) Threading should be done with an electric threading machine;
(5) Deburring and processing of rounded corners at the end of the plastic-coated steel pipe should be done with a file;
(6) A small brush or a small toothbrush should be used to apply high-strength inorganic solvent liquid epoxy resin coating.
Second, inspection methods for plastic-coated steel pipes
(1) Appearance inspection: Visually inspect the appearance quality of the coated steel pipe.
(2) Thickness measurement: Take two cross-sections of different lengths from both ends of the coated steel pipe, and use an electromagnetic thickness gauge to measure the coating thickness at any four orthogonal points on the circumference of each cross-section.
(3) Pinhole test: The length of the pipe section specimen is about 1000 mm. Use an electric spark leak detector to check the steel pipe coating under the specified test voltage. If the coating thickness is not greater than 0.4 mm, the test voltage is 1500 V. If the coating thickness is greater than 0.4 mm, the test voltage is 2000 V. Check whether there is spark generation.
(4) Adhesion test: The adhesion test is carried out by 7.4.2 of CJ/T 120-2008.
(5) Bending test: The coated steel pipe with DN ≤ 50 mm is subjected to a bending test. The length of the pipe section specimen is (1200 ± 100) mm. Under the environment of a temperature of (20±5)℃, the steel pipe is bent on a pipe bending machine or die with a curvature radius of 8 times the nominal diameter and a bending angle of 30o. 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, the specimen is cut open from the middle of the bending arc to check the inner coating.
(6) Flattening test: Flattening test is performed on coated steel pipes with DN>50 mm. The pipe section specimen is (50±10) mm long. Under the environment of a temperature of (20±5)℃, as shown in Figure 1, the specimen is placed between two flat plates and gradually compressed on the pressure testing machine until the distance between the two flat plates is four-fifths of the outer diameter of the specimen. During flattening, the weld of the coated steel pipe is perpendicular to the direction of load application. After the test, the inner coating is checked.
(7) Impact test: Cut a sample of about 100 mm in length from any position of the coated steel pipe, and perform an impact test by the provisions of Table 2 at a temperature of (20±5) ℃ to observe the damage of the inner coating. During the test, the weld should be in the opposite direction of the impact surface.
(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 Hg and maintain it for 1 min. After the test, check the inner coating.
(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 1h, then take it out and cool it naturally to room temperature. After the test, take out the specimen and check the inner coating (the appearance color is allowed to become darker and darker).
(10) Low-temperature test: The length of the pipe section specimen is (100±10) mm. The specimen is placed in a low-temperature box, cooled to (-30±2) ℃, and kept at a constant temperature for 1 hour. Then it is taken out and placed in an environment with a temperature of (20±5) ℃ for (4~7) hours.
(11) Pressure cycle test: Connect to the water pressure supply system, fill with water to exclude air, and then conduct 3000 alternating water pressure tests from (0.4±0.1) MPa to MPa. The cycle of each test is not more than 2 seconds. After the test, check the inner coating and conduct an adhesion test according to the provisions of 6.4. The test results should 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 under each temperature condition for 24 h in the following order:
(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 subjected to corresponding anti-corrosion treatment. The pipe section is placed in distilled water at (70±2) ℃ and immersed for 30 days. After the test, it is taken out and naturally cooled to room temperature, and the coating inside the specimen is inspected.
Post time: Dec-25-2024