Adhesive Pipe Joint Assembly Using Heat-Activated Capillary Flow
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Solution Overview
Problem
Conventional brazing methods in the heat exchanger industry are prone to leaks and pinhole defects due to the manual nature of the process, and alternative methods like liquid adhesives and epoxy-based tapes face issues with consistency and quality control.
Innovation Solution
A method involving a ring of uncured adhesive pre-applied to a pipe, which remains non-flowable at ambient temperatures and becomes flowable upon heating, allowing gravity and capillary action to fill radial clearances between pipes, resulting in a stable and durable bond upon curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual brazing is used to join pipes, then skilled labor can apply the bonding process, but the process results in leaks and pinhole defects due to manual application
Solution Approach 1:
The adhesive system is self-applying through capillary action, eliminating the need for manual application. The adhesive automatically flows into the joint clearance when heated, ensuring consistent coverage without operator skill requirements.
Solution Approach 2:
The manual mechanical application process is replaced by thermal-capillary action. Heating the assembly activates the adhesive to flow automatically into the joint through capillary forces, substituting human operation with a controlled physical process.
2Ease of manufacture
If liquid adhesives are used to join pipes, then bonding can be achieved, but the adhesives are messy and difficult to apply consistently
Solution Approach 1:
The adhesive is formulated as a non-flowable ring or tape at ambient temperature, providing a controlled, clean application format. This prevents messiness while ensuring precise placement on the pipe surface before activation.
Solution Approach 2:
The adhesive's flow properties are changed by temperature. At ambient temperature, it remains non-flowable for precise application; when heated above its melting point, it becomes flowable to fill the joint clearance automatically through capillary action.
3Ease of manufacture
If epoxy-based tapes are used as brazing replacement, then bonding can be achieved, but voids and varying thicknesses occur if tape sections do not abut properly
Solution Approach 1:
The adhesive transitions from a rigid, fixed form (non-flowable ring or tape) at ambient temperature to a fluid state when heated. This dynamic change allows the adhesive to flow and self-level, filling gaps and ensuring uniform thickness regardless of initial placement precision.
Solution Approach 2:
The adhesive undergoes a phase transition from solid (non-flowable) to liquid (flowable) when heated above its melting point. This phase change enables the adhesive to automatically fill voids and achieve uniform distribution in the joint clearance.
4Ease of manufacture
If tape is applied to pipes for joining, then bonding can be achieved, but it is difficult to insert male pipe into female sections due to the inclusion of tape
Solution Approach 1:
The adhesive is pre-applied to the male pipe end in a non-flowable ring form that does not interfere with insertion. After the male pipe is inserted into the female pipe, heating activates the adhesive to flow into the joint clearance, eliminating assembly difficulties.
Solution Approach 2:
The adhesive's viscosity and flow properties are changed by temperature. At ambient temperature during assembly, it remains non-flowable and does not obstruct insertion; after insertion, heating makes it flowable to fill the joint.
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 eliminates the need for skilled labor and reduces defects by ensuring consistent and high-quality pipe joints, comparable in durability to traditional brazing methods.
Implementation Method 1
gravity and/or capillary activity pulls the flowable adhesive into radial clearances between or proximate to contact points of the male and female members
Implementation Method 2
gravity and/or capillary activity pulls the flowable adhesive into radial clearances
Implementation Method 3
The resulting assembly is heated above a temperature at which the uncured adhesive becomes flowable
Data Source
AI summary
Apparatus and method for joining two tubular elements (14, 22) at a joint using an adhesive that is non-flowable at ambient temperatures but flowable at an elevated temperature. A ring (12) of uncured, non-flowable adhesive is placed around the male end of a male (14)/female (22) pipe interface. Upon exposure to elevated temperatures, the ring (12) melts and flows down into the interface, and cures.