Field Joint Coating (FJC) is an operation that is performed after 2 pipes have been joined together by welding.
The first step to performing a successful field joint coating is surface preparation – usually performed through grit blasting. This is an important process because a poorly-prepared surface would result in the failure of the specified coating following application.
The next step is induction heating, generally using a coil. Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, through heat generated in the object (by eddy currents) rather than by an external heat source. Different coatings are applied at different temperatures ranging from 60°C up to 240°C
The final stage is the application of the specified coating. Typical coating types are Fusion Bonded Epoxy (FBE), Multi Component Liquid (MCL), 3-Layer, Injection Moulded Polyurethane (IMPU) and Polyurethane Foam Injection (PUF).
A field joint is the point where two pipe sections are welded together.
In the field 12m (or longer) lengths of pipe are laid down end to end, these small pipeline sections are placed in locations and then welded. These welded areas are called field joints.
Many pipelines can be hundreds of kilometres in length and there will be thousands of field joints that need to be coated.
Different types of field joint anti-corrosive coatings include, liquid coatings such as epoxies, urethanes, heat shrinkable sleeves and sometimes fusion-bonded epoxy are required for the field joints.