Field coating
The plastic coating in the pipe connection area is completed using corrosion protection bands (polyethylene, butyl rubber, or combinations) or heat-shrinkable material (shrink sleeves, shrink tubing, or heat-processable bands) in accordance with DIN 30672-1 or ISO 21809-3. Polyurethane/epoxy resin fillers are also used for special applications.
For pipelines that are additionally cathodically protected, post-coating material in accordance with DIN EN 12068 must be selected. The manufacturer's instructions must always be observed.
The permissible operating temperatures for recoating systems can be found in the technical documentation for the various systems. The coating systems are classified according to application for increasing mechanical loads A, B, and C.
Example: Field coating with cold wrappers
1. Preparatory steps: Pipe and mill-applied coating must be cleaned of dirt, oil and grease and the temporary corrosion protection coat removed. The adhesive and the epoxy resin layer of the plastic coating can remain on the pipe. Bevel the edges of the mill-applied coating to an angle of 30°.
2. Apply primer in accordance with the manufacturer’s instructions. It may be necessary to let the surface dry before applying the primer. Observe flash-off time requirements before wrapping the anti-corrosion tape round the pipe joint.
3. The anticorrosion tape is applied spirally, pulling it tight as it is wrapped around in either one or two layers, depending on the tape used. Each wraparound must overlap the previous layer by 50 percent as instructed by the manufacturer, with an all-round overlap of at least 50 mm over the mill-applied coating.
