Uncoated Tubular Liner for District Heating Pipe Relining

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Solution Overview

Problem

Existing re-liners for district heating pipes face issues with water ingress leading to corrosion, embrittlement, and delamination, especially under high temperatures and pressures, resulting in thermal losses and costly trenching for renovation.

Innovation Solution

A tubular liner impregnated with a curable and high-temperature-resistant resin, using corrosion-resistant reinforcing fibers, is introduced into the pipe and cured in place, eliminating the need for coatings and addressing ingress and delamination issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional liners are used for relining district heating pipes, then installation is possible, but water ingress causes corrosion and embrittlement of reinforcing fibers

Engineering Contradiction:

Improveliner durabilityVSAvoidwater ingress

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention removes the outer coating layer from the liner structure, eliminating the interface where water ingress and delamination occur. By using a single-layer construction without outer protection coatings, the patent eliminates the harmful effect of water penetrating through or between layers, thereby preventing corrosion and embrittlement of reinforcing fibers.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs composite materials consisting of corrosion-resistant reinforcing fibers (such as glass, carbon, or basalt fibers) combined with a curable resin matrix. This composite structure provides both mechanical strength and inherent corrosion resistance, eliminating the need for separate protective coatings while maintaining durability against water ingress.

Inventive Principle:

Principle #40Composite materials

2Strength

If multiple laminated layers are used in liners, then structural strength is improved, but delamination occurs due to loss of adhesion

Engineering Contradiction:

Improveliner structural strengthVSAvoidlayer adhesion

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The invention extracts and eliminates the outer coating layer from the multi-layer liner structure, reducing it to a single-layer construction. This removes the delamination problem entirely by eliminating the interface between layers where adhesion loss occurs, while maintaining sufficient structural strength through the use of high-performance composite materials.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If trenching is used for pipe renovation, then pipe replacement is possible, but high costs and network shutdown are required

Engineering Contradiction:

Improvepipe renovation feasibilityVSAvoidnetwork shutdown time

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The invention applies the nesting principle by inserting the liner inside the existing district heating pipe, creating a nested structure where the new liner is contained within the old pipe. This allows renovation without removing the original pipe, enabling trenchless rehabilitation that avoids network shutdown and high excavation costs while restoring pipe functionality.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The liner is prepared with corrosion-resistant fibers and curable resin in advance, allowing it to be manufactured and positioned before installation. The preliminary preparation of the liner with its protective composition enables rapid installation through existing access points, minimizing network shutdown time and avoiding the need for extensive trenching operations.

Inventive Principle:

Principle #10Preliminary action

4Power

If high temperatures and pressures are used in district heating pipes, then heat transport efficiency is improved, but corrosion from heating fluid increases

Engineering Contradiction:

Improveheat transport efficiencyVSAvoidinternal corrosion

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent uses composite materials with corrosion-resistant reinforcing fibers (glass, carbon, basalt) embedded in a curable resin matrix. This composite structure provides inherent resistance to internal corrosion from heating fluid while maintaining the ability to withstand high temperatures and pressures required for efficient heat transport, eliminating the trade-off between efficiency and corrosion resistance.

Inventive Principle:

Principle #40Composite materials

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 a durable, corrosion-resistant liner that withstands high temperatures and pressures, preventing water ingress and extending pipe life without trenching, enhancing productivity and reducing maintenance costs.

Implementation Method 1

a curable and high-temperature-resistant resin, using corrosion-resistant reinforcing fibers, is introduced into the pipe and cured in place

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentEP3359864B1Liner having no coating utilized for relining a heating pipe, method and use

Publication Date: 2025.09.17 PRESSURE PIPE RELINING SWEDEN AB

Figure 1A~1B

AI summary

The invention relates to a tubular liner (10) for re-lining a district heating pipe (20), said liner (10) comprising a first tubular layer (12) of woven fiber material, said first (12) tubular layer of woven fiber material being impregnated with a curable resin (R), said first tubular layer (12) of woven fiber material comprises corrosion resistant reinforcing fibers (F).