Field Joint Coatings – Cold Weather Application
The application of Pipeline Field Joint Coatings in cold weather is a difficult one. There are multiple technologies with strengths and weaknesses that in cold climates become more challenging to install successfully.
What are the challenges the cold weather can bring to the field joint coating process?
In general, coatings and plastics do not behave the same in lower temperatures. They have significantly slower curing-times (in some cases the curing process stops completely), the increased viscosity reduces wetting on the profile substrate and polymer film integrity can be compromised. Also, in cold climates there is an increased risk of condensation, ice formation and contamination of abrasive media.
The field coating contractor has to build an installation plan that considers all the different contingencies, regardless of the selected coating system.
Preheating Elements. In cold climates, the preheating of the steel surface is necessary not only to achieve the curing temperature, but also to eliminate any potential condensation on the surface. The selection of the heating element is decided not just by budget but also by accessibility. It is important to understand the heating surface preparation sequence; for instance if an open torch is used it is recommendable to preheat the surface before abrasive blasting to eliminate risk of flash rusting on the surface. Induction coils are obviously a preferred method, but unfortunately they are not always available.
Sheltering the Joint Coating. The FJC should be protected during the application and curing process. The construction of enclosures for protection from the cold wind and weather is necessary in cases where the environment could interfere with the coating curing process.
Quality control. The quality control process should be adapted to the environmental conditions and curing mechanism. Many of the testing protocols are designed for “normal” temperatures. QC testing such as adhesion, Shore D hardness and peel resistance are not meant to be performed at lower temperatures. The inspection testing plan should be reviewed and accepted alternatives, such as companion plates, or other test methods that are more suitable for lower temperatures, should be used.
The solution when a pipeline is built during colder climates, is to have a solid plan and well-trained crew. Depending on the coating of choice, the contractor needs to be able to adapt and consider all contingencies and be prepared to deal with any setbacks.
It is your pipeline, so the choice is yours!
Mario Moreno P.Eng. NACE CIP Level 3