District Heating Pipe Structure for Trenchless Installation Loads
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Solution Overview
Problem
Existing district heating pipes face challenges in achieving efficient trenchless installation while minimizing shear forces on the thermal insulation layer, which is crucial for maintaining heat retention and protecting against mechanical and electrolyte damage.
Innovation Solution
The district heating pipe design incorporates a glass fibre-reinforced plastic outer casing layer with a force transmitting structure, such as a pulling head or metallic protection shield, to transfer tensile and compressive forces directly to the central metal tube and casing layer, thereby avoiding shear forces on the insulation layer during trenchless installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional insulated pipe structure is used for trenchless installation, then the installation can be performed, but shear forces act on the thermal insulation layer causing damage and heat loss
Solution Approach 1:
A force transmitting structure made of glass fibre-reinforced plastic is introduced as an intermediary element between the central metal tube and the outer jacket layer. This mediator transfers installation forces (tensile and compressive) directly to the metal tube and jacket, preventing shear forces from acting on the thermal insulation layer, thus maintaining insulation integrity while enabling trenchless installation
Solution Approach 2:
The force transmitting structure is constructed from composite materials (glass fibre-reinforced plastic) that provide both mechanical strength for force transmission and compatibility with the existing pipe structure. This composite material enables the structure to withstand installation forces without transferring damaging shear stresses to the thermal insulation layer
2Strength
If the outer casing layer thickness is increased to transfer forces, then force transmission capability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The thickness of the outer casing layer is optimized to specific ranges (5-24 mm depending on pipe diameter) to achieve sufficient force transmission capability. By carefully selecting and controlling the thickness parameter, the design achieves adequate strength without unnecessary complexity or cost, balancing performance requirements with manufacturing simplicity
Data Source
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AI summary
The invention relates to a district heating pipe section (10) with a central metal tube (12), a corrosion protection layer, a thermal insulation layer (16) of a polymer foam, and a jacket layer (18) protecting the thermal insulation layer from mechanical damage. The district heating pipe section (10) has a distal end that is the front end when the district heating pipe is trenchlessly installed. The district heating pipe section has an outer casing layer (20) made of glass fibre-reinforced plastic and a force transmitting metal structure (22) that is fixed to the distal end of the central metal tube. The force transmitting structure (22) has an outer diameter that matches or exceeds an outer diameter of the outer casing layer (20). The force transmitting structure (22) is designed to transfer forces acting on the distal end of the district heating pipe section (10) in a longitudinal direction of the district heating pipe section (10) to the central metal tube (12) and the outer casing layer (20), thus avoiding shear and compressive forces on the heat insulation layer (16) made of a polymer foam that is arranged radially between the central metal tube (12) and the outer casing layer (20).