Plastic-coated steel pipe detection method

the detection of plastic-coated steel pipes has always been an important existence for us. given the existing conditions, the following inspections and tests are often carried out by us:

appearance inspection: visually inspect the appearance quality of the coated steel pipe, and the test results should meet the requirements of 5.1.

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 points perpendicular to the circumference of each cross-section. the test results should meet the requirements of 5.4.

pinhole test: the length of the pipe section test piece is about 1000 mm, and the coating of the steel pipe is inspected under the specified test voltage with an electric spark leak detector. mm, and the test voltage is 2000 v. check whether there is any electric spark, and the test result should meet the requirements of 5.5.

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.

bending test: the coated steel pipe with dn≤50mm 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.

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 results should meet the requirements.

impact test: cut a sample with a length of about 100 mm from any position of the coated steel pipe, and perform an impact test at a temperature of (20±5) °c to observe the damage to the inner coating. during the test, the weld seam should be in the direction opposite to the impact surface, and the test results should meet the requirements.

vacuum test: the length of the pipe section test piece is (500±50) mm, use appropriate measures to block the inlet and outlet of the pipe, gradually increase the negative pressure from the inlet to 660 mm hg, keep it for 1 min, check the inner coating after the test, and the test results should meet the provisions of 5.10.

high-temperature test: the length of the pipe section test piece is (100±10) mm, the test piece is placed in a constant temperature box, the temperature is raised to (300±5) ℃, and the temperature is maintained for 1 hour, and then it is taken out and naturally cooled to room temperature. after the test, take out the test piece and check the inner coating (allow the appearance to become darker and darker), and the test result should meet the requirements of 5.11.

low-temperature test: the length of the pipe section test piece is (100±10) mm, the test piece is placed in a low-temperature box, cooled to (-30±2) ℃, and kept at a constant temperature for 1 h, then taken out and placed in a temperature of (20±5) ) ℃ environment (4~7) h.

pressure cycle test: connect to the water pressure supply system, fill with water, and remove air, then conduct 3000 alternating water pressure tests from (0.4±0.1) mpa to mpa, the period of each test is not more than 2 s. after the test, check the inner coating, and carry out the adhesion test according to the provisions of 6.4. the test results should meet the provisions of 5.13.

temperature cycle test: the length of the pipe section test piece is (500±50) mm, and the test piece is placed in the following order for 24 h under each temperature condition: (50±2)℃; (-10±2)℃; (50±2)℃; (50±2)℃; 2) °c; (-10±2) °c; after the test, place the specimen in an environment with a temperature of (20±5) °c for 24 hours, check the condition of the inner coating, and conduct an adhesion test according to the provisions of 6.4. the test results should meet the provisions of 5.14.

warm water aging test: the size and length of the pipe section test piece is about 100 mm, and the exposed parts of the pipe section should be treated with corresponding anti-corrosion treatment. the pipe section is placed in (70±2) ℃ distilled water and soaked for 30 days. after the test, it is taken out and naturally cooled to room temperature. , check the inner coating of the test piece, and the test results should meet the requirements of 5.15.