Testing method of plastic-coated steel pipe(Part One)

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.