The 4”, 10” and 12” Suction & Discharge lines detailed in Table 1 above were installed over 20 years ago to transport Fuel Oil between three adjacent pump rooms. These lines serve as critical conduits for transporting highly viscous fuel oil for Bunker Fuel operations.
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 pipes 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 between the 4 and 8 o'clock positions. The cyclic heating of the heat trace cables further accelerated the corrosion process.
Upon removing the insulating lagging, the client installed a pipe repair clamp over a defect of particular concern to prevent any leakage if the lines were to be operated before a successful composite repair could be completed.
The repair areas covered several complex pipe geometries, including; two 90° elbows, a pipe repair clamp and three tees. The repairs were located at height and confined space between the pipes and the pump room wall created limited access.
Figure 1 below shows some of the areas affected by the external corrosion under insulation (CUI).
Non-destructive testing (NDT) revealed significant reduction in wall thickness. The minimum remaining wall thickness was measured between 3.7mm and 5.7mm at the locationstested. Composite repairs in accordance with ASME PCC-2:2022 were thereforerequired to restore the geometry and structural integrity of the pipe.
The client hired Icarus Composites, a trading division of Icarus Group Ltd, tocomplete these repairs. The affected areas were categorised into elevendistinct repair sections, totalling 18.631 metres.
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 an Elcometer and Testex Press-O-Film to make sure it met the minimum surface roughness profile of 55µm, as shown in Figure 2. The surface roughness readings were found to be within a range of 99– 139µm,well above the minimum required.
Silica epoxy resin paste 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 3. The Silica epoxy resin paste is a combination of Fumed SilicaThixotropic powder and the BioWrap 102 epoxy resin. When combined these create a lightweight filler that serves as a load transfer material, transferring the hoop stresses caused by the internal pressure from the pipe to the engineered composite wrap.
The client wished for the pipe repair clamp that they had installed over a defect of particular concern to be encapsulated within the composite repair. The reason for this is that they were unsure of when the line was going to be operated and they didn’t want to risk having tooperating the line without the pipe repair clamp before a composite repair could be successfully installed.
The protruding bolt tails and handles were removed from the clamp by the client. To reduce any potential stress concentrations inthe composite laminate, metal epoxy was used to create a smooth transition between the pipe repair clamp and the pipe. Thereby eliminating any sharpchanges in geometry, as shown in Figure 4.
The composite used for the remedial works was BioWrap 102, a wet layup glass fibre bio-resin epoxy composite, fully qualified to bothISO 24817 and ASME PCC-2.
When mixed the BioWrap 102 resin has an overall plant-based content of 27%. This provides this composite with significant environmental benefits in comparison to similar petro-chemical derived epoxy resins. The BioWrap 102 composite system utilises a quadriaxial fibreglass cloth which provides strength in the 0°, +45°, -45° & 90° directions. This makes it the perfect reinforcement for repairing complex geometries as the multiaxial fibres ensure that there are fibres running in the circumferential direction of the pipe providing strength in the hoop direction which is the dominant principal stress of an internally pressurised pipe.
The entire repair area was primed using the BioWrap 102 resin. The BioWrap 102 composite materials was applied using 6”wide tapes utilising a spiral wrap with a 50% overlap. This means that the tape being applied overlaps the previous tape by 50%. Each pass in one direction therefore applies 2 layers of composite.
Once the minimum required number of layers of Biowrap 102 was applied, release film and high stretch compression film were applied. The release film acts as abarrier to prevent the resin from sticking to the compression film during curing. The compression film compresses the composite to ensure there are no delamination’s in the composite laminate and to ensure good adhesion of the composite to the pipeline substrate. Once applied, the BioWrap 102 composite repair system was left to cure for 16 hours at ambient temperature which was measured to be between 13°C and 21°C.
Upon completion of the curing process, full cure of the composite laminate was verified using Shore D hardness readings. All readings were found to be above 80 verifying that the BioWrap 102 composite system had fully cured.
Quality assurance tests were completed to ensure that all 11 composite repairs had been conducted in accordance with ASME PCC-2. The composite repair laminate was checked for the following.
Below is a summary of the steps completed for each of the 11 repairs.
In total, the project took 6 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 repairs were located at height and close to the pump room wall. This created aconfined space, restricted access and safety challenges.
Scaffolding was provided by the client to allow access to the repairs and provide a safeworking platform at the correct height to allow the safe wrapping of theBioWrap 102 composite.
The restricted access made it difficult to apply the BioWrap 102 composite as the rolls of 6” fibreglass tape were too wide to fit through the 3” gap between the pipework and the wall. The gap is shown in Figure 5. To get around this the BioWrap 102 composite was cut into strips which fit around the circumference of the pipe with a 2” overlap back overitself. This allowed the strips to be passed through the gap. The next strip was then applied with a 50% overlap over the previous strip. The 2” overlap was varied in position between the 12, 3, 6 & 9 o’clock positions to prevent any weak spots. This is a method we call “strip wrapping” which we specifically developed for restricted access.
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The access for the repair of the tees was also extremely tight with approximately 12” of clearance for a technician to stand and apply the BioWrap 102 composite,as shown in Figure 6. To achieve this a safe working platform was erected behind the pipework and the repair completed in two stages – the wrapping of the tee and the wrapping of the pipework below the platform.
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Successful installation of BioWrap 102 was attained over the 11 repair areas. Photographs of the completed repairs are shown below in Figure 7 to Figure 17.
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Thedetails of each completed repair are shown below.
The successful repair of the corroded suction and discharge pipes using BioWrap 102 has restored the pressure-retaining capabilities of the pipes, preventing further corrosion and eliminating the need for immediate pipe replacement. This has provided significant economic benefits for the client, as they avoided thehigh costs associated with new pipe installations. Additionally, this approach has positive environmental implications by extending the service life of existing infrastructure and reducing waste. The project demonstrates the effectiveness of advanced composite materials in addressing severe corrosionissues, highlighting the importance of thorough preparation, skilled execution, and adherence to industry standards in achieving durable and reliable repairs.
