Thermoplastic Pipe Coating with Controlled Expansion
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Solution Overview
Problem
Existing methods for coating pipes with polyurethane foam result in turbulence and density variations due to high injection speeds, leading to cavitation and local differences in thermal and mechanical properties, making it difficult to achieve a flexible and effective insulation system, especially for dynamic use and high temperatures.
Innovation Solution
A method involving a flowable thermoplastic coating material with a cellular structure is guided over a heat exchange surface, cooled to a temperature just above its solidification point, and applied to the pipe with an outer compact plastic covering layer, which adjusts the expansion properties and improves flexibility without requiring a supporting outer sheathing pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polyurethane foam is injected at high speed into the cavity between carrier pipe and jacket pipe, then the coating process is efficient and productive, but turbulence forms leading to cavitation and density variations in the pipe
Solution Approach 1:
The coating material is pre-cooled to a temperature close to its solidification point before injection. This preliminary cooling action reduces the material's流动性 (flowability) and prevents turbulence during injection, thereby avoiding cavitation and density variations while maintaining efficient coating application
Solution Approach 2:
The temperature of the coating material is changed from ambient or elevated temperature to near-solidification temperature. This parameter change fundamentally alters the material's flow characteristics, enabling high-speed injection without turbulence while maintaining density uniformity in the cured foam coating
2Strength
If a compact jacket system is used for mechanical or corrosion protection, then the system has high structural strength, but the system is highly resistant to bending and lacks flexibility
Solution Approach 1:
Instead of using a compact solid jacket system, the invention employs polyurethane foam with a cellular (porous) structure. This porous material provides the necessary mechanical strength and corrosion protection while inherently offering flexibility and bendability, resolving the contradiction between strength and adaptability
Solution Approach 2:
The invention creates a composite structure combining the carrier pipe, cellular polyurethane foam coating, and jacket pipe. This composite material system integrates the strength of the metal pipes with the flexibility and insulation properties of the foam, achieving both mechanical protection and system flexibility
3Temperature
If rigid foam insulation is used for thermal insulation in underground pipes carrying hot media, then thermal insulation performance is improved, but the insulation ages at high temperatures above approximately 120°C
Solution Approach 1:
The temperature parameter of the coating material is precisely controlled to be close to but above its solidification temperature. This parameter optimization ensures the foam cures at controlled conditions that prevent thermal degradation, maintaining both insulation performance and long-term reliability at elevated operating temperatures
4Manufacturing precision
If the coating material is cooled to a temperature close to its solidification temperature before application, then the coating material expands minimally and maintains consistent thickness, but the coating process requires precise temperature control
Solution Approach 1:
The invention replaces complex mechanical thickness control systems with thermal control. By cooling the coating material to near-solidification temperature, the material's expansion is naturally minimized and thickness consistency is achieved through thermal physics rather than mechanical adjustment mechanisms, simplifying the overall system
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 method simplifies the coating process, enhances the flexibility of the coated pipe, and ensures reliable adhesion and thermal insulation by controlling the expansion and solidification of the coating material, reducing internal stresses and maintaining consistent coating thickness under external forces.
Implementation Method 1
guiding a flowable coating material which comprises an extruded thermoplastic material having a cellular structure, over a heat exchange surface of an extrusion head; cooling the coating material to a temperature not more than 30K above a solidification temperature of the coating material
Implementation Method 2
cooling the coating material to a temperature not more than 30K above a solidification temperature of the coating material
Data Source
AI summary
A method for coating a pipe involves applying a coating material of cellular structured extruded thermoplastic material to the pipe and enclosing it on the outside by an outer covering layer of compact plastic. In an extrusion head, the annular opening for supplying coating material can be adjusted to a desired temperature by a region having coolant channels separated from the annular opening by an annular heat exchange surface. Before being applied to the pipe, the flowable coating material is guided along the heat exchange surface and cooled to a temperature just above the solidification temperature thereof. After the coating material leaves the annular opening, the coating material expands in a controlled manner, widening the outer covering layer depending on the adjusted temperature of the coating material, until the coating material begins to solidify. The outer covering layer surface condition can correspond to or be different from the pipe.