2. For the plastic-coated pipes inside and outside, because the inner and outer walls are coated, it is recommended to adopt the ditch connection with the diameter of DN50-DN200, which is convenient and will not destroy the coating; For pipes with external zinc plating and internal plastic coating, the general diameter DN 15- 100 can be connected by thread, because the casing wire is on the external zinc plating layer, which will not damage the epoxy coating on the inner wall. The specific choice still depends on the actual situation of construction.
3. Plastic-coated steel pipe, also known as plastic-coated pipe, steel-plastic composite pipe and plastic-coated composite steel pipe, is a steel-plastic composite steel pipe with steel pipe as the matrix and plastic anticorrosion layer welded on the inner surface or inner and outer surfaces of steel pipe (bottom pipe) through spraying, rolling, dipping and suction processes.