Inspection of Coating Appearance: Check whether the coating is smooth and free of burrs, whether there is any exposed steel, and whether the color matches the customer's requirements.
Verification of Coating Thickness: Ensure that the coating thickness meets the customer's specifications.
Pinhole Testing: Conduct a test to detect any pinholes in the coating.
Adhesion Test: Perform the adhesion test according to Appendices A and B of CJ/T 120-2016.
Bend Test: Cut a specimen approximately 50mm long from any position on the plastic-coated steel pipe under test. Place the specimen between two flat plates at room temperature and gradually compress it using a tensile testing machine. For polyethylene coatings, control the distance between the two plates to be 2/3 of the specimen's outer diameter; for epoxy resin coatings, control the distance to be 4/5 of the specimen's outer diameter. During compression, ensure that the weld seam of the plastic-coated steel pipe is perpendicular to the compression direction. After flattening, observe the inner coating for cracks and peeling. For plastic-coated steel pipes with nominal sizes greater than DN200, DN150 pipes can be used as substitutes.
Flattening Test: Conduct a flattening test on plastic-coated steel pipes with an outer diameter greater than 50mm. The length of the pipe segment specimen should be (50±10)mm. Place the specimen between two flat plates at a temperature of (20±5)°C and gradually compress it on a pressure testing machine until the distance between the two plates is 4/5 of the specimen's outer diameter for epoxy resin coatings or 2/3 for polyethylene coatings. During compression, ensure that the weld seam of the coated steel pipe is perpendicular to the load application direction. After the test, inspect the inner coating for cracks and peeling. If no such defects are found, the pipe is deemed qualified. For plastic-coated steel pipes with nominal sizes greater than DN200, DN150 pipes can be used as substitutes.
Impact Test: Cut a specimen approximately 100mm long from any position on the plastic-coated steel pipe under test. Conduct the impact test at room temperature as specified in the diagram below, with the weld seam oriented opposite to the impact surface. After the test, inspect the inner coating for cracks and peeling. If no such defects are found, the pipe is deemed qualified. For plastic-coated steel pipes with nominal sizes greater than DN200, DN150 pipes can be used as substitutes.
Hygiene Performance Testing: Perform hygiene performance tests according to GB/T 17219.
Vacuum Test: The length of the pipe segment specimen should be (500±50)mm. Block the inlet and outlet of the pipe using appropriate measures and gradually increase the negative pressure from the inlet to 660mm Hg, maintaining it for 1 minute. After the test, inspect the inner coating for any detachment.
High-Temperature Resistance Test, Low-Temperature Resistance Test, Pressure Cycle Test, Temperature Cycle Test, Warm Water Aging Test, etc.
