Field Joint Coating

The root cause of premature breakdown of coatings at the field joint area usually stems from a lack of detail within the Field Coating Specifications in terms of technical requirements when compared to the rigorous attention given to factory-applied coatings. Evidence would suggest that unless practical attention is given to the variances induced by local environmental factors, which require systematic planning to negate, then poor workmanship/inspection could result. To ensure the entire pipeline coating system withstands the ingress of corrosion throughout its design life the importance of the field joint coating system is paramount.

Factory-applied coatings to pipelines are carefully specified with known variances in surface preparation and application controlled and keenly monitored by any number of inspection bodies who have a stakeholding in the finished project. The lifetime design protection is assured through pre-qualification and process qualification activities to ensure the coating plant can repeat 100% compliance in a production environment. In essence the field joint coatings should match the performance and design criteria of the factory-applied coating to provide one homogeneous layer protection system along the length of the entire pipeline.

ISO 21809-3 provides a prescribed method to confront the vagrancies of field joint coatings. So, for each coating classification there is attention to pre-qualification and process qualification to mirror the rigour given to factory-applied coatings. Pipeline Protection can provide materials compliant to ISO21809-3 and also field joint services compliant to the same standard.

According to ISO 21809-3 Field Joint Coatings can be classified in groups and designated codes as demonstrated in the following table;

Code Type of Field Joint Coating
1A Hot Applied Bitumen Tape
1B Petrolatum Tapes
1C Wax Tapes
1D Cold Applied Polymeric Tapes
2A Heat Shrinkable materials – PE Based
2B Heat Shrinkable materials – PE based, applied over primer
2C Heat Shrinkable materials – PP based, applied over primer
3A Single Layer Fusion Bonded Epoxy powder
3B Dual Layer Fusion Bonded Epoxy powder
4A Liquid Epoxy
4B Liquid Polyurethane
4C Fibre-reinforced epoxy
4D Fibre-reinforced vinylester
4E Cast Polyurethane
5A Flame-sprayed polypropylene powder over epoxy layer
5B Polypropylene tapes/sheets hot applied over epoxy layer
5C Injection Moulded polypropylene over an epoxy layer
5D Flame sprayed polyethylene powder applied over an epoxy layer
5E Polyethylene tapes/sheets hot applied over an epoxy layer
6 Thermally Sprayed Aluminium (TSA)
7 Hot-applied microcrystalline wax coatings
8A Elastomeric coatings, Polychloroprene
8B Elastomeric coatings, EPDM