District Heating Pipe Force Transfer for Trenchless Installation
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Solution Overview
Problem
Existing district heating pipes face challenges in economical installation, particularly when trenchless methods are employed, due to the need to manage tensile, compressive, and shear forces that can damage the thermal insulation layer during installation.
Innovation Solution
The district heating pipe design incorporates a central metal tube, a thermal insulation layer, a jacket layer, and an outer casing layer made of glass fibre-reinforced plastic, with a force transmitting structure, such as a pulling head or metallic protection shield, to transfer forces without shearing the insulation layer, ensuring the pipe can be installed trenchlessly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the district heating pipe is designed for trenchless installation by pulling or pushing, then installation efficiency and productivity are improved, but shear forces act on the thermal insulation layer causing damage and reducing reliability
Solution Approach 1:
A force transmitting structure (pulling head or thrust head) made of metal and glass fibre-reinforced plastic is introduced as an intermediary component. This structure is fixed to the central metal tube and attached to the outer casing layer, allowing installation forces to be transmitted through the metal and GRP components without directly shearing the thermal insulation layer, thus enabling trenchless installation while protecting the insulation layer integrity
Solution Approach 2:
The force transmitting structure combines metal (for strength and force transmission) with glass fibre-reinforced plastic (for protection and force distribution). This composite construction allows the structure to withstand high installation forces while distributing them in a way that prevents shear damage to the thermal insulation layer, resolving the contradiction between installation efficiency and insulation layer protection
2Strength
If the outer casing layer is made thicker to absorb and transmit tensile and compressive forces, then the protection and force transmission capability are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The outer casing layer is designed with specific local thickness requirements (at least 5 mm, preferably at least 10 mm) at critical locations where force transmission is needed. This localized thickening provides the necessary strength for force transmission while avoiding unnecessary material usage and complexity in non-critical areas, balancing protection capability with manufacturing simplicity
Data Source
AI summary
A district heating pipe section comprises a central metal tube, a corrosion protection layer, and a thermal insulation layer protected by a jacket layer. The district heating pipe section further has a distal end that is the front end when a district heating pipe is installed, an outer casing layer, and a force transmitting structure comprising a metal fixed to a central metal tube's distal end. The thermal insulation layer is arranged radially between the central metal tube and the outer casing layer. An outer diameter of the force transmitting structure matches or exceeds an outer diameter of the outer casing layer. The force transmitting structure transfers forces acting on the district heating pipe section's distal end in a longitudinal direction of the district heating pipe section to the central metal tube and the outer casing layer, avoiding shear and compressive forces on the thermal insulation layer.