Induction Coil Electrofusion for Polymer Pipe Liner Joints
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Solution Overview
Problem
Existing methods for electrofusion of polymer liners in pipelines face challenges, particularly in closed-bevel automatic welding techniques, where external energization of heating coils is difficult, and prior inductive solutions consume excessive electrical power due to large magnetic fields.
Innovation Solution
The method involves using an induction coil inside the pipe to locally heat and fuse polymer liner sections by generating a controlled magnetic field, allowing for spot heating and progressive fusion along the interface without direct electrical connections through the pipe wall, and the apparatus includes a drive system and alignment sensors for precise coil movement and heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic induction is used to heat the liner bridge, then direct electrical connections through the pipe wall are eliminated, but the power consumption increases significantly due to large magnetic fields
Solution Approach 1:
The patent applies local quality by concentrating the magnetic field generation to specific zones where heating is required, rather than using a large-scale electromagnetic induction system. The induction coil is positioned to create localized magnetic fields that induce currents only in the heating elements at the liner-pipe interface, reducing overall power consumption while maintaining effective heating where needed.
Solution Approach 2:
The patent introduces heating elements as intermediaries between the induction coil and the liner material. These heating elements are electrically connected to the induction coil and serve as a mediator to transfer thermal energy to the liner and bridge materials, enabling indirect heating that reduces the magnetic field strength required compared to direct electromagnetic heating of the entire assembly.
2Ease of manufacture
If heating coils are energized through electrical leads extending through the fitting, then the fitting can be fused to parent liners, but electrical leads create potential leak paths
Solution Approach 1:
The patent extracts the electrical connection function from the structural integrity function. By using an induction coil positioned outside the liner bridge and energizing heating elements through non-penetrating means (such as inductive coupling or connections through the pipe exterior), the design removes electrical leads that would otherwise penetrate the liner and create leak paths, while still enabling the heating and fusion process.
3Productivity
If closed-bevel automatic welding techniques are used, then welding efficiency is improved, but external energization of electrofusion fittings becomes difficult
Solution Approach 1:
The patent inverts the traditional approach by positioning the induction coil outside the liner bridge and heating the liner from the exterior rather than from the interior. This reversal allows the heating system to work effectively with closed-bevel configurations where internal access is limited, as the induction coil can be positioned on the pipe exterior to energize the heating elements at the interface without requiring open-bevel preparation or internal access.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient fusion-bonding of liner bridges to parent liners within polymer-lined steel pipes without electrical connectors through the pipe wall, reducing power consumption and improving cycle times in pipeline fabrication.
Implementation Method 1
energising an induction coil disposed within the pipe to heat only a portion of an interface between the liner sections. This may be achieved by generating heat locally in at least one heating element positioned at the interface
Implementation Method 2
The induction coil is then moved along the interface to heat successive portions of the interface above the melting temperature
Implementation Method 3
That portion of the interface is thereby heated above a melting temperature of the polymer material of the liner sections, at which that material melts and fuses locally
Data Source
AI summary
A method of joining together liner sections within a polymer-lined pipe energises an induction coil inside the pipe to spot-heat part of a circumferential interface between the liner sections. This melts and fuses the polymer material locally. The induction coil is then moved along the interface to heat other parts of the interface successively above the melting temperature. An apparatus for performing the method has a power supply for energising the induction coil and a drive system for moving the energised induction coil relative to a body of the apparatus. The apparatus may be configured as a carriage that is movable along the pipe.