Polyethylene | coating developments
provide long term pipeline protection. Another benefit of the SureBond system is that
mechanical properties such as impact resistance, hardness and flexibility – all of which are directly linked to installation performance of the coating system in the field – exceed those of equivalent 3LPE systems. Impact resistance is so improved (>12J/mm) that the sug- gested topcoat thickness for a SureBond-based system is roughly half of that of an equivalent 3LPE. While SureBond was designed to meet existing 3LPE
specifications, its adhesive-less design results in a positively distinct performance in adhesion testing, where the topcoat cohesively fails. This provides a failsafe mechanical and moisture barrier that further protects FBE. This cohesive failure behavior occurs even at high operating temperatures and is shown in Figure 3. The interlocking chemically bonded system also
helps spread strain across the total thickness, which results in very good flexibility performance at much lower temperatures than alternative anti-corrosion systems. Bredero Shaw testing has shown SureBond yields a 2.5° ppd system bend test at -50°C and passes a 2.5° ppd topcoat bend test at -70°C without cracking. This opens up a variety of new installation applications, including previously unavailable cold bending capability or artic installation conditions. The coating system design also offers minimal
component thermal mismatch and reduces shrinkage from the melt to solid phase, which eliminates issues with residual stress delamination during storage or field joint application. This results in outstanding thermal cycling properties, showing no disbondment in over ten -70°C to +100°C cycles. Even more aggressive thermal shock testing with -70°C to +100°C shock cycles and no thermal equilibrium also resulted in no disbondment. Given the performance data, Bredero Shaw is
confident a SureBond pipeline will offer the asset owner a safer operating window and provide operators with a higher level of confidence even after unexpected process upset, such as a sudden gas line depressurization, which could otherwise result in coating failure. This advanced thermal stability performance also delivers a higher level of pipeline protection in permafrost settings.
Table 1: Typical surface energy results (in mJ/m²/ dynes) for different coating systems
Polymer material 3LPE Surface 3LPP Surface SureBondTM Epoxy
Surface Energy 34-36
<30 (28-29) 44-46 54-56
Field joint performance As discussed earlier, a key design parameter for the SureBond topcoat was to deliver enhanced field joint performance. The system is based on a blend of reactive and functionalised polyethylene. The reaction between the components begins during the extrusion process and continues in the inline post cure oven after the extrusion step, locking the polymer networks in place. However, the system retains a small amount of reactivity from the adhesion promoter and the functionalised polyethylene, which reacts at the temperatures typically reached during field joint installation. This small amount of residual reactivity enhances the chemical bond to the adhesive group or epoxy group in a typical field joint solution. In addition, SureBond exhibits a substantially higher surface energy than the typical polyethylene grades commonly used in 3LPE application, as shown in Table 1. Higher surface reactivity translates to greater chemical affinity and hence a stronger bond to the field joint material.
Global availability Bredero Shaw secured and executed its first SureBond 100 application at its Ras-Al- Khaimah, facility in UAE in January of this year. The coating system was applied to 6, 18, 24 and 30-inch pipes for the Audex Rotary oil terminal project at Fujairah. The SureBond product will be rolled out across the company’s global coating facilities over the coming months. ❙
www.brederoshaw.com/Surebond
About the author: Cedric Oudinot is global product line manager for anticorrosion and internal coatings at Bredero Shaw in Houston, US. Oudinot graduated in engineering in France, gaining a chemical engineering masters degree and an MBA in the US. He has more than a decade of experience in commercial and technical roles in the international oil & gas industry. Oudinot joined Bredero Shaw in 2010, taking on his current role in 2012.
May 2014 | PIPELINE COATING 19
Figure 3: A
SureBond 100 peel test under way (left) and example of the
cohesive failure (right) resulting in peel
performance above 4N/mm at 80°C
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