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Differences between plastic lined steel pipes and plastic coated steel pipes

Plastic-lined Steel Pipes vs Plastic-coated Steel Pipes

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  1. Plastic lined steel pipe:
  • Definition: Plastic-lined steel pipe is a steel-plastic composite product made of steel pipe as the base pipe, with its inner and outer surfaces treated, zinc plating and baking paint or spray paint on the outside, and lined with polyethylene plastic or other anti-corrosion layers.
  • Classification: Plastic-lined steel pipe is divided into cold water plastic-lined steel pipe, hot water lined plastic steel pipe, and plastic rolling plastic lined steel pipe.
  • Lining plastic: polyethylene (PE), heat-resistant polyethylene (PE-RT), cross-linked polyethylene (PE-X), polypropylene (PP-R) hard polyvinyl chloride (PVC-U), chlorinated polyvinyl chloride (PVC-C).
  1. Plastic-coated steel pipe:
  • Definition: Plastic-coated steel pipe is a steel-plastic composite product that is made of steel pipe as the base pipe and plastic as the coating material. The inner and outer surfaces are melted and coated with a plastic layer or other anti-corrosive layer.
  • Classification: Plastic-coated steel pipe is divided into polyethylene-coated steel pipe and epoxy resin-coated steel pipe according to the different coating materials.
  • Plastic coating material: polyethylene powder, polyethylene tape, and epoxy resin powder.
  1. Product labeling:
  • The code number of the plastic lining steel pipe for cold water is SP-C.
  • The code number of the plastic lining steel pipe for hot water is SP-CR.
  • The polyethylene-coated steel pipe code is SP-T-PE.
  • Epoxy-coated steel pipecode is SP-T-EP.
  1. Production process:
  • Plastic lining: after the steel pipe is pre-treated, the outer wall of the plastic pipe is evenly coated with adhesive, and then placed in the steel pipe to make it expand and form a steel-plastic composite product.
  • Plastic coating: steel pipe pre-treatment after heating, high-speed plastic coating treatment, and then the formation of the steel-plastic composite products.
  1. Performance of plastic-lined steel pipes and plastic-coated steel pipes:
  • Property of plastic layer of plastic lined steel pipes:

Bonding strength: the bonding strength between the steel and the lining plastic of the plastic-lined pipe for cold water should not be less than 0.3Mpa (30N/cm2): the bonding strength between the steel and the lining plastic of the plastic-lined pipe for hot water should not be less than 1.0Mpa (100N/cm2).

External anti-corrosion performance: the product after galvanized baking paint or spray paint, at room temperature in 3% (weight, volume ratio) sodium chloride aqueous solution soaked for 24 hours, the appearance should be no corrosion white, peeling, rise, or wrinkle.

Flattening test: the plastic-lined steel pipe does not crack after 1/3 of the outer diameter of the flattened pipe, and there is no separation between the steel and the plastic.

  • Coating performance of plastic-coated steel pipe:

Pinhole test: the inner surface of the plastic-coated steel pipe was detected by an electric spark detector, and no electric spark was generated.

Adhesion: the adhesion of polyethylene coating should not be less than 30N/10mm. The adhesive force of epoxy resin coating is 1~3 grade.

Flattening test: no cracks occurred after 2/3 of the outer diameter of the polyethylene-coated steel pipe was flattened.No peeling occurred between the steel pipe and the coating after 4/5 of the outer diameter of the epoxy resin-coated steel pipe was flattened.