Fusion bond epoxy (FBE) has long been used as a protective coating for oil and gas pipelines with one consistent and major drawback – mechanical resistance. As FBE is a relatively thin, hard coat, it is prone to damage during handling, installation, as well as operation. Some progress in improving this has been made over the years. The major improvement has been the dual-layer ARO systems. These systems have improved impact and gouge resistance but at the expense of flexibility.
To take the performance to a higher level using a different concept, a new system for a multi-layer FBE-based coating has been developed by Jotun Powder Coatings, resulting in a tough resilient, anti-corrosion coating. This new system is commercially branded J-trac.
The system consists of three layers, each providing a different characteristic and the combination of these three layers works together to deliver high levels of performance.
The outer layer is a tough layer resisting damage arising from impacts and gouges. The middle layer is a resilient layer functioning as a cushion to absorb impacts and protect the inner layer. The inner layer is an FBE optimised to ensure good wetting, adhesion, and anti corrosion properties designed to work with the protection of the outer layers (Figure 1).
The three layers are applied in a continuous coating operation similar to that currently employed for dual-layer epoxies. This results in the three layers being fused together.
How does the system work to deliver performance?
The tough outer layer minimises impact damage and the middle resilient layer spreads the impact over a wider area ensuring the impact energy is dissipated. The anti-corrosion inner layer is thereby protected from damage (Figure 2).
The value of an energy absorbing process can be clearly seen in the comparison of two well known impact test procedures. A standard FBE panel tested for impact, for example, in accordance with the AWWA C213 method, is required to meet a requirement of 11 J, but the same coating tested using the CSA Z245.20.06 method will only yield 2-3 J. Why such difference? Because the energy is absorbed differently.
The AWWA method allows the energy to be absorbed by deforming the metal panel, in CSA it is absorbed only by the FBE. With the new system, it is absorbed by the resilient layer, which also spreads the load ensuring it does not damage the anticorrosion layer.
In this case the tough outer layer resists penetration and the inner resilient layer absorbs and spreads the load (Figure 3).
When the load is heavy enough to penetrate the tough outer layer, the resilient middle layer acts as a lubricant to smooth the gouge and protect the anti-corrosion inner layer (Figure 4).Stress on the tough outer layer is spread evenly. The resilient middle layer absorbs the bending force reducing stress raisers that can break the outer layer, ensuring the anti-corrosion inner layer is well protected (Figure 5).
The J-trac system features a combination of FBE powders providing all the benefits and none of the weaknesses of stand-alone FBE and multi-layer extruded coatings.
In addition to long term anti-corrosion protection the J-trac system provides:
* Mechanical protection matching or exceeding multi-layer capabilities;
* Compatibility with traditional girth welds coating solutions for FBE;
* Negligible damage on concrete weight coating application;
* Advanced abrasion and impact performance;
* Compatibility with anti-slip coatings;
* High flexibility at low temperatures;
* Cathodic protection transparency;
* Raised weld coverage; and,
* Pipe stress tolerance.
A full performance evaluation of J-trac against CSA Z245.20-06 is shown opposite.
For further information regarding this article, you can contact: Jotun Powder Coatings Denis Grimshaw on Mobile: +9 71 50 550 1228 email@example.com