Testing Method of Plastic Coated Steel Pipe

A. Visual inspection

Visually inspects the appearance quality of the coated steel pipe.

B. Thickness measurement

Take two cross-sections of different lengths from the two ends of the coated steel pipe, and measure the coating thickness at any four points on the circumference at right angles with an electromagnetic thickness gauge on each cross-section.

C. Pinhole test

The length of the pipe section test piece is about 1000mm. The coating of the steel pipe is inspected under the specified test voltage with an electric spark leak detector. The thickness of the coating is not more than 0.4mm, the test voltage is 1500 V, and the thickness of the coating is greater than 0.4mm. It 2000 V. checks for sparking.

D. Adhesion test

The adhesion test is carried out under CJ/T 120-2008.

E. Bending test

The coated steel pipe with DN≤50mm is subject 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) ℃, the radius of curvature is 8 times the nominal diameter of the steel pipe, and the bending angle is 30o, and the bending is performed on a pipe bender or a mold. During the bending test, there is no filler in the tube, and the well is located on the side of the main surface of the bed. After the test, cut the test piece from the middle of the curved arc to check the inner coating.

F. Flattening test

Coated steel pipes with DN>50mm are subjected to flatten 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 a pressure testing machine until the distance between the two flat plates is four-fifths of the outer diameter of the test piece, and then coat The steel pipe weld is perpendicular to the direction of load application. After the test, check the inner coating.

G. Impact test

Cut a sample with a length of about 100mm from any position of the coated steel pipe, and conduct an impact test in an environment with a temperature of (20±5) ℃ to observe the damage of the inner coating. During the test, the weld should be located in the opposite direction of the impact surface.

H. Vacuum test

The length of the test piece of the pipe section is (500±50) mm. Use appropriate measures to prevent the inlet and outlet of the pipe. Gradually increase the negative pressure from the inlet to 660mm Hg and keep it for 1 min. After the test, check the inner coating.

I. High-temperature test

The length of the test piece of the pipe section is (100±10) mm. Place the test piece in a constant temperature box, raise the temperature of (300±5) ℃ and keep it constant for 1 h, then take it out and let it cool to room temperature. After the test, take out the test piece and check the innermost coating (allowing the appearance of darkening and darkening).

J. Low-temperature test

The length of the test piece of the pipe section is (100±10) mm. Place the test piece in a low-temperature box, cool it down to (-30±2) ℃, and keep it constant for 1 h, then take it out and place it at (20±5) ℃ (4~7) h under the environment.

K. Pressure cycle test

Connect with the water pressure supply system, fill with water to remove air, and then carries out 3,000 alternating water pressure tests. The period of each test is not more than 2 s. After the test, check the inner coating and conduct an adhesion test as required.

L. Temperature cycle test

The length of the test piece of the pipe section is (500±50) mm, and the test piece shall be placed under each temperature condition in the following order for 24 h: After the test, the test piece shall be placed in an environment with a temperature of (20±5) ℃ for 24 h. Coating condition, and conduct adhesion test according to regulations.

M. Warm water is aging test

The length of the test piece of the pipe section is about 100 mm. The exposed parts of the pipe section should be treated with corresponding anti-corrosion treatment. The pipe section shall be immersed in distilled water (70±2) ℃ for 30 d. After the test, take it out and let it cool to room temperature. Check the test piece Internal coating.