Multi layer PE / PP coating plant
Multi layer pipe coating process
In the multi layer pipe coating process, pipes are blast cleaned and covered with a compound coating of three or more individual layers. Generally the first layer is a fusion bonded epoxy coating of 100 – 200 microns thickness, which is the actual anti-corrosion layer. On top of the epoxy, an adhesive layer of 250 – 350 microns is applied which acts as the bond layer between the epoxy and the top layer(s). The top layer usually consists of 2 – 4 mm PE or PP and provides mechanical protection for the pipe. In some cases, foamed PP or syntactic PP is added in extra intermediate layer(s) as an insulation coating for heated transport lines. The two main types of coating application are side extrusion and crosshead extrusion (also known as sleeve extrusion). In side extrusion, pipes rotate while top coating is wrapped around the pipe. In crosshead extrusion, the pipe does not rotate and coating is ‘pulled’ as a sleeve around the pipe.
These multi layer PE and/or PP pipe coating plants can be manufactured for virtually any capacity and pipe size and can be fitted with all thinkable add-ons such as:
- internal dust removal equipment
- extra surface treatment equipment (flush / alkaline wash, phosphoric acid wash, chromate)
- mechanized pipe handling systems (pipe transfer indexers, walking beams, pipe push conveyors, chain transporters)
- pipe end cleaning systems
- granules transport & heating systems
- pipe data collection and filing
- automatic coating thickness measurement
- water processing plant
- QC laboratory equipment
Extruders for pipe coating applications
A unique capability of Selmers is that the extruders required for the multilayer coating plants are fully designed and manufactured in-house and therefore are specially equipped for pipe coating applications, whereas ‘buyout’ extruders would be more general purpose types, not specifically designed for pipe coating. This Selmers proprietary design has been very successful, and extruders ranging from 100 up to 2500 kg/h are currently in use worldwide at pipe coating plant locations.