At the Section 2-layer and 3-layer external coating using extruded PE on welded and seamless steel pipe intended for the use in construction of line pipes and exploration pipelines and the outflows, for conveying gas, gas distribution systems and water pipelines. The following materials are used: chromatizing compound, primer, adhesive, PE.
The original pipe and materials (shot, epoxy powder, adhesive, PE, protective varnish) go through the incoming inspection (1). Then, the pipe surface is prepared and that ensures good operational properties for coated pipe: degreasing (2), washing, heating (3), shot-blasting (4). Then, the quality of the surface treated is inspected. (5).
Immediately before coating application, the pipe ends are wrapped in paper (6) and the pipes are joined by couplings (7). The coupled pipes go to the dust removal machine (8) and then to the inductor to be heated (9) for the subsequent epoxide application. (10).
The line applies 2- and 3-layer coatings with the total wall thickness up to 3,5 mm. The coating is applied using the ring extrusion method (11) that ensures a smooth and uniform coating. After adhesive and PE application, the cooling unit starts operating (12).
The line includes automatic UT wall thickness measuring system (13) and holiday detector (14) that control the coating thickness and dielectric continuity circumferentially. The coating is inspected for the adhesive and impact strength. For periodic testing, the cathodic peeling, thermocycling, resistance to cracking etc. are used. After paint marking (15), the pipe is automatically cut (16).
The pipe ends are automatically cleaned from excessive PE (17) and coated with a protective coating: conservative varnish (18). After that, the final inspection and packing are carried out (19).