Induction-Welded RTR Pipe Joints for Leak-Resistant High Pressure Sealing
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Solution Overview
Problem
RTR pipe joints in high-pressure applications are prone to failures due to improper installation, leading to leaks and reduced confidence in the technology, particularly in oil and gas services, where conventional jointing techniques rely heavily on skilled labor and are susceptible to misalignment, over-torqueing, and degradation of sealing systems.
Innovation Solution
A system and method combining integral threading with thermoplastic welding using tie layers of thermoplastic materials and susceptors for induction heating, which ensures a permanent seal and increased strength by fusing the spigot and socket joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional jointing techniques (adhesive/bonded or interference joints) are used for RTR pipes, then the pipes can be assembled, but the joints are prone to failures due to improper installation, misalignment, and degradation of sealing systems
Solution Approach 1:
The patent replaces mechanical jointing techniques (threaded connections, key-lock joints, adhesive bonding) with induction heating technology. The induction heating system uses electromagnetic fields to heat and melt thermoplastic material, creating a fused joint that eliminates the need for mechanical assembly skills. This substitution transforms the joining process from a skill-dependent mechanical operation to an automated thermal process, thereby improving joint reliability while reducing installation skill dependency.
Solution Approach 2:
The patent changes the physical state of the thermoplastic material from solid to molten and back to solid through controlled induction heating. By adjusting heating parameters (power, duration, temperature distribution), the system creates optimal bonding conditions that ensure reliable joints regardless of installation skill level. This parameter control approach eliminates the variability associated with manual mechanical jointing.
2Stress or pressure
If threaded or key-lock joints are used for high-pressure RTR pipes, then the pipes can be connected, but the joints are susceptible to over-torqueing and sealing system degradation
Solution Approach 1:
The patent utilizes the phase transition of thermoplastic material from solid to molten state during induction heating, and then back to solid state during cooling. This phase change allows the material to flow and fill the joint interface completely, creating a homogeneous bond that distributes stress evenly. The resulting joint can handle high pressures (up to 1500 psi as mentioned in the patent) without the localized stress concentrations that cause failure in threaded or key-lock joints.
Solution Approach 2:
The patent creates a composite joint structure where thermoplastic material bonds the RTR pipe components together. The thermoplastic acts as a matrix that reinforces the joint interface, combining the pressure-resistant properties of RTR pipes with the bonding capabilities of thermoplastic materials. This composite approach produces joints that maintain strength under high pressure conditions without susceptibility to over-torqueing or sealing degradation.
3Ease of manufacture
If adhesive/bonded joints are used for lower pressure RTR pipes, then the pipes can be joined, but the performance is limited by surface preparation requirements and field conditions
Solution Approach 1:
The patent replaces adhesive bonding with induction heating technology. Instead of relying on chemical adhesion that requires precise surface preparation, the induction heating system uses electromagnetic energy to melt and fuse thermoplastic material directly at the joint interface. This substitution eliminates the need for meticulous surface preparation while maintaining joint integrity, thereby improving ease of manufacture without sacrificing manufacturing precision.
Solution Approach 2:
The induction heating system performs self-adjusting heat distribution across the joint interface. The electromagnetic fields automatically concentrate energy where needed based on the material properties and geometry, eliminating the need for external surface preparation steps. The thermoplastic material itself serves the dual function of being heated and forming the bond, making the process self-sufficient and insensitive to field condition variations.
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
The solution provides improved sealing, reliability, and increased joint strength by eliminating installation-dependent failures, allowing for de-skilled assembly and enabling integrity monitoring, thus enhancing the operational envelope of RTR pipes to 1500 psi and 200°F.
Implementation Method 1
a system and method for welding reinforced thermosetting resin (RTR) pipe joints by induction heating
Implementation Method 2
upon application of induction heating to the coupler, the heat between the first pipe, the second pipe, and the coupler is sufficient to melt the thermoplastic material
Implementation Method 3
the heat between the first pipe, the second pipe, and the coupler is sufficient to melt the thermoplastic material such that, when the heat is removed, the hardened thermoplastic material seals the first pipe and the second pipe to the coupler
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A system for coupling pipes includes a first pipe having a tapered, spigot end; a second pipe having a tapered, spigot end; wherein the first pipe and the second pipe are made from a reinforced thermosetting resin (RTR), and a coupler having two tapered socket ends adapted to internally receive the respective tapered, spigot ends of the first pipe and the second pipe, wherein a thermoplastic material is disposed between an exterior of the first pipe and an interior of the coupler. A thermoplastic material is disposed between an exterior of the second pipe and the interior of the coupler. Upon application of induction heating to the coupler, the heat between the first pipe, the second pipe, and the coupler is sufficient to melt the thermoplastic material such that, when the heat is removed, the hardened thermoplastic material seals the first pipe and the second pipe to the coupler. A system for coupling pipes includes a first pipe having a tapered, spigot end; and a second pipe having a tapered, socket end adapted to internally receive the tapered, spigot end of the first pipe. The first pipe and the second pipe are made from a reinforced thermosetting resin (RTR). A thermoplastic material is disposed between an exterior of the first pipe and an interior of the second pipe. Upon application of induction heating to the coupler, the heat between the first pipe and the second pipe is sufficient to melt the thermoplastic material such that, when the heat is removed, the hardened thermoplastic material seals the first pipe to the second pipe. A method includes disposing a thermoplastic material between an exterior of a first pipe and an interior of a coupler; disposing a thermoplastic material between an exterior of a second and an interior of the coupler; inserting the first pipe and the second pipe into the coupler; and applying induction heating to the coupler sufficient to melt the thermoplastic material such that, when the heat is removed, the hardened thermoplastic material seals the first pipe and the second pipe to the coupler. A method of coupling pipes includes disposing a thermoplastic material between an exterior of a first pipe and an interior of a second pipe; inserting the first pipe into the second pipe; and applying induction heating to the coupler sufficient to melt the thermoplastic material such that, when the heat is removed, the hardened thermoplastic material seals the first pipe to the second pipe.