The component details are provided below.
The 12" SCH40S carbon steel fuel oil line detailed above was installed over 20 years ago. This line serves as a critical conduit for transporting highly viscous fuel oil to Bunker Fuel Ships. To allow for efficient heat management of the fuel oil, heat trace cables and lagging for insulation were utilised. Positioned in a coastal environment, the pipeline faced the corrosive effects of salt and moisture accumulation within the lagging. Over time, this led to the degradation of the pipe coating, external corrosion,and localised pitting, primarily at the 6 o'clock position. The cyclic heating of the heat trace cables further accelerated the corrosion process.
Non-destructive testing (NDT) revealed significant reduction in wall thickness. The minimum remaining wall thickness was measured between 4.1 mm and 7.2 mm at the 33 locations tested. Composite wrap repairs in accordance with ISO 24817:2017 were therefore required to restore the geometry and structural integrity of the pipe. The client hired Icarus Composites, a trading division of Icarus Group Ltd, to complete these repairs. The affected areas were categorised into seven distinct repair sections,totalling 16.44 meters.
The first step of the repair process was the surface preparation. The correct surface preparation is critical to the success of the repair as it ensures good adhesion of the composite laminate to the pipeline substrate. The surface preparation was completed using rotary metal brushes to SSPC-SP-11: Power tool cleaning to bare metal. The surface profile was then assessed using Testex Press-O-Film to make sure it met the minimum surface roughness profile of 55µm, as shown in Figure 1. The surface roughness readings were found to be very consistent with a range of 91 – 112µm, well above the minimum required.
Metal epoxy was used to smooth the change in geometry caused by the welds, fill the pitted areas and restore the circular profile of the pipe, as shown in Figure 2. The metal epoxy also serves as a load transfer material, transferring the hoop stresses caused by the internal pressure onto the engineered composite wrap.
The composite used for the remedial works was Attalus SnapCure 140, a pre-impregnatedglass fibre epoxy composite, fully qualified to both ISO 24817 and ASME PCC-2. Being pre-impregnated, allows for Attalus SnapCure 140 to be applied as soon as the metal epoxy is cured. There’s therefore none of the messy and time-consuming process of mixing and applying of resin associated with wet-layup systems. Figure 4 shows Attalus SnapCure 140 applied to the pipeline prior to curing.
Once applied, release film and shrink tape were applied, as shown in Figure 5. The release film acts as a barrier to prevent the resin from sticking to the shrink tape or heater blanket during curing. The shrink film shrinks up to 20% and compresses the composite to ensure there is no delamination in the composite laminate and to ensure good adhesion of the composite to the pipeline substrate. Once applied, the heater blanket shown in the lower photo of Figure 4 was used to cure the composite. Insulation was used to reduce the heat lost to the environment allowing for faster curing.
Below is a summary of the steps completed for each of the 7 repairs.
In total, the project took 9 days to complete from start to finish. All necessary safety measures and precautions were taken. All SDS, COSHH, RAMS and the client’s onsite rules were strictly adhered to.
The weather presented a challenge as the area was windy and there was frequent rainfall. A habitat, shown in Figure 5, was erected to keep the rain off during application of the composite materials.
Successful installation of Attalus SnapCure 140 was attained over the 7 repair areas.The completed repair to repair area 6 is shown in Figure 6.
The details of each repair are shown below.
Attalus SnapCure 140 will increase the longevity of the pipeline, extending its life. The epoxy resin of the Attalus SnapCure 140 will prevent oxygen and moisture reaching the substrate surface, thereby preventing any further external corrosion. The repairs were given a 20 year guarantee by Icarus Composites. This not only benefits the client economically but also contributes to environmental preservation by avoiding the production of a new pipe
