Plastic-coated steel pipes for water supply possess the following characteristics:
First, the inner surface of plastic-coated steel pipes is covered with a plastic coating, which maintains the smoothness inside the pipe, reduces water flow resistance, and enhances water flow capacity. Moreover, this smooth flow ensures sufficient water flow demand, prevents scaling within the pipe during use, inhibits bacterial growth, and minimizes water pollution.
Second, the outer surface of plastic-coated steel pipes is also coated with plastic, enhancing their adaptability. The outer coating improves the steel pipe's corrosion resistance, water resistance, oxidation resistance, and solvent resistance. Additionally, it mitigates the impact of the environment on the pipe. Since water supply pipes are inevitably buried underground, the outer coating effectively prolongs the service life of the pipeline.
Procedures for Inspecting Plastic-Coated Steel Pipes:
The primary inspection methods for plastic-coated steel pipes include visual inspection, thickness measurement, pinhole test, bending test, flattening test, and low-temperature test, each with its specific focus.
Visual Inspection: This involves examining the visual quality of the coated steel pipe using the naked eye.
Thickness Measurement: This step involves measuring the coating thickness at any four points intersecting perpendicularly on the circumference of the pipe at any two cross-sections.
Pinhole Test: The pinhole test utilizes an electric spark leak detector to inspect the steel pipe coating under a specified test voltage, simultaneously checking for the generation of electric sparks.
Bending Test: Typically conducted on a pipe bending machine or mold, it's important to note that during the bending test, the pipe is tested without any filling material, and the weld seam is positioned on the side of the main bending plane.
Flattening Test: In this test, the specimen is placed between two flat plates and gradually compressed on a pressure testing machine until the distance between the plates is reduced to four-fifths of the specimen's outer diameter. During flattening, the weld seam of the coated steel pipe should be perpendicular to the direction of the applied load.
Low-Temperature Test: This test involves placing the specimen in a low-temperature chamber for one hour before transferring it to room temperature conditions.
