Clamp encapsulation

Overview

This case study outlines the encapsulation of a pipe repair clamp as part of a broader composite repair process for several corroded suction and discharge lines. The lines, which were integral to transporting fuel oil in a coastal environment, exhibited significant corrosion due to salt exposure, moisture accumulation, and cyclic heating from heat trace cables. The repair was conducted in line with ASME PCC-2:2022 standards, utilising the BioWrap 102 composite system.

Problem Identification

The suction and discharge lines in question had been in service for over 20 years. They suffered from external corrosion under insulation (CUI), which was exacerbated by the coastal environment and the heat trace cables used to maintain fuel viscosity. Specifically, the corrosion led to localised pitting and significant reduction in wall thickness, with measurements as low as 3.7mm.

A defect in a particular section prompted the installation of a pipe repair clamp by the client as a temporary measure to prevent leakage before a full composite repair could be conducted. However, the client expressed concern over the risk of operating the line without the pipe repair clamp due to the risk of the pressure causing a through-wall leaking defect.

Clamp Encapsulation Process

Given the risk of a through-wall defect, it was decided to encapsulate the clamp within the composite repair to ensure the integrity of the line until the final repair was in place. The encapsulation process involved several key steps:

1. Preparation of the Clamp and Pipe Surface:
   • The first step was to remove the protruding bolt tails and handles from the clamp to facilitate smooth integration with the surrounding pipe. This was crucial to eliminate any sharp changes in geometry, which could cause stress concentrations in the composite material.
2. Application of Metal Epoxy:
   • To create a smooth transition between the pipe repair clamp and the pipe itself, metal epoxy was applied over the clamp, as shown in Figure 1. This step ensured that no abrupt edges would compromise the structural integrity of the composite laminate by reducing potential points of weakness.
3. Composite Application:
   • The composite material used for the encapsulation was BioWrap 102, a wet layup glass fiber bio-resin epoxy composite. This material was chosen due to its strength and environmental benefits, with 27% plant-based content in the resin.
   • The quadriaxial fiberglass cloth within the BioWrap 102 provided multi-directional strength, essential for handling the complex geometry of the clamp and pipe. The composite was applied using a spiral wrap technique, ensuring 50% overlap for added durability and structural integrity.
4. Curing Process:
   • Once the composite was applied, a release film and compression film were used to compress the layers and prevent delamination during the curing process. This ensured a seamless and strong repair around the clamp and the pipe.

Conclusion

The clamp encapsulation provided a robust and reliable temporary solution, ensuring the safe operation of the fuel oil lines until the full composite repair could be completed. By integrating the repair clamp into the composite system, the client was able to mitigate the risk of leaks while maintaining operational safety.

The use of BioWrap 102 composite not only restored the structural integrity of the corroded lines but also provided environmental benefits through its plant-based resin content, aligning with modern sustainability goals in industrial repairs.

This case demonstrates the effectiveness of composite repair systems in handling complex geometries and existing temporary solutions like pipe repair clamps. The smooth transition achieved with metal epoxy and the multiaxial strength of the composite materials ensured a durable and long-lasting repair, shown in Figure 2, below.

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