3PE anti-corrosive coatings with good corrosion resistance, moisture permeability resistance and mechanical properties, is widely used in the oil pipeline industry. This kind of anti-corrosive coating steel pipe is easy to happen edge warping problems due to corrosion.
The 3 PE anti-corrosion layer steel pipe in reserve period of polyethylene polishing groove, the residual height of pipe weld has not been grind or with uneven grinding, this will lead to the grind off of the epoxy powder at the bottom of the polyethylene. If the anti-corrosion pipe had been long deposited in the open air, the surface of the weld metal will be corrosion, leading to 3 PE coating become warped edge.
The measures to avoid edge warping of the steel tube 3PE coating tube end
1. Under the circumstance of having no effects to the pipe welding, the reserved length of the epoxy powder of the end of the polyethylene should be appropriately increased. This can prevent the 3PE coating edge warping caused by the pipe metal corrosion due to the long time deposited in the air.
2.The pipe end should be covered to prevent the rain erosion which will lead to the serious corrosion if the pipe had been deposited in the open air for too long.
3. If the pipeline field construction cycle is too long, the pipe end can be brushed with weldable anti-rust paint to prevent corrosion caused by corrosion during storage of 3 PE coating which will lead to the edge warping.
4. Strictly control the grinding quality of reserved tube end reserved. To make the epoxy powder reserved length > 20mm in the slope of polyethylene in weld and the pipe body, in order to prevent the welds epoxy powder at the bottom be corrosion that will lead to the 3PE anti-corrosion layer become warped edge. The pipe weld grinding should be paid attention to:
1) There should be 10-20mm polyethylene layer flat section with no weld residual height from the weld grinding to the polyethylene bevelling to ensure that the polyethylene pipe groove squeeze cementing quality.
2) The residual height of welding after the grinding should try to be the same height as the pipe in order to prevent the epoxy powder be polished when polishing the polyethylene layer bevelling.
3) The end without grinding and the bevelling which had be grinding should also be like bevelling of polyethylene layer (≤30°), in order to guarantee the extrusion pressure can be even on the PE layer, to prevent the edge warping due to the bad bonding in anti-corrosion layer.
5. Only by protecting the whole period of the reserved epoxy powder coating, the edge warping can be retard caused by corrosion of the pipe. Domestic polyethylene pipe groove processing adopts the wire wheel grinding way, and this will damage the epoxy powder coating. And the mechanical processing should be adopted, and the bottom of the blade should have a device to control the depth of the tool feed limited, in order to avoid injury epoxy powder coating.