Technique principle of reliable TCP electrothermal fitting connection

The key reliable TCP electrothermal fitting connection technology that allows this novel electrofusion coupler to achieve a high pressure rating for hydrogen gas pipelines is the use of a continuous fiber reinforced polymer (TCP) composite layer as the structural component.

Conventional electrofusion couplers utilize resistive wire heating to melt and fuse an inner thermoplastic liner to the pipe liner, creating a fluid-tight seal. However, these couplers are only rated for low pressures around 100 psi, insufficient for high pressure hydrogen pipeline applications.

This new coupler design overcomes the pressure limitation through the incorporation of a high strength TCP composite structural layer, wound with optimal fiber angles to handle hoop and axial stresses. The composite layer provides the required burst rating and pressure containment capacity, while the electrofusion process provides the sealing function.

In more detail, the coupler consists of three key layers progressing from the interior surface outwards:

Inner thermoplastic liner - This liner is made of HDPE with embedded resistive heating wires. When electrical current is applied, the wires heat up and melt the surrounding HDPE resin. This allows fusion bonding to the liner of the pipes being joined, creating a continuous leak-proof seal. The liner material provides corrosion resistance and hydrogen compatibility.

Structural TCP layer - This layer constitutes the main high pressure load-bearing component. It is fabricated by helically winding carbon fiber or glass fiber reinforcement impregnated with a thermoplastic resin matrix. The fiber angle is optimized to handle hoop, axial, and radial stresses. The TCP provides a burst rating of 100 bar and the strength needed to contain pipeline pressure. It is wound using automated fiber placement technology that allows rapid in-situ consolidation.

Protective outer layer - The outer layer is a neat thermoplastic coating that shields the TCP from mechanical damage, UV degradation, moisture ingress, and other environmental factors. It ensures long-term durability and integrity.

The combination of the electrofusion liner and high strength composite winding enables the creation of a coupler that can be installed without elastomeric seals, adhesives, or mechanical joints. The fusion bonding process occurs in one step during on-site installation.

The automated fiber placement technology used to fabricate the structural layer provides repeatable and reliable quality. It also enables customization of each coupler to match the fiber angle and thickness required for specific pipe dimensions and operating pressures.

The end result is an innovative coupler design that meets the following key performance characteristics:

-High pressure rating exceeding 100 bar for hydrogen gas containment

-Maintenance-free sealed joint without elastomers or adhesives

-Corrosion resistance and hydrogen compatibility

-On-site installability using standard electrofusion techniques

-Reliable long-term performance exceeding 50 year pipe lifetimes

-Applicability to both metal and composite pipe materials

-Custom optimization of structural layer for operating demands

This novel hybrid design combining conventional electrofusion with high strength TCP composites provides a solution to enable the safe and economical transmission of hydrogen gas through buried pipelines. It eliminates the need for maintenance and provides a technically elegant option for joining non-metallic composite pipes in high pressure conditions.

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