Double-Walled Pipeline Fitting for Insulated High-Strength Joints
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Solution Overview
Problem
Existing double-walled pipeline joints lack efficient thermal insulation and mechanical strength due to single-walled junctions, which are prone to mechanical fatigue and reduced lifespan, especially when using materials like polyurethane resin or DiPolyCyclopentadiene (DPCD) that undergo significant shrinkage and poor adhesion.
Innovation Solution
A double-walled pipeline fitting with segments in the form of half-shells, held by a fastening system, and a double-walled insulated sleeve, filled with a hardening material like DPCD or epoxy, ensuring reduced shrinkage and improved mechanical force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a single-walled junction is used to connect inner tubes of successive sections, then the welding time is reduced and installation cost is lowered, but the thermal insulation is compromised and mechanical strength is reduced
Solution Approach 1:
The joint fitting is divided into multiple segments (typically 3-5 segments) that are arranged around the junction of inner tubes. Each segment is a separate component that can be independently installed and secured, allowing the joint to achieve full mechanical strength without requiring a single complex weld operation. The segments are held in place by a fastening system that distributes mechanical loads evenly around the joint.
Solution Approach 2:
The joint fitting is nested within the double-walled pipeline structure, with segments positioned between the inner and outer tubes. The segments are inserted into the annular space and secured by fastening systems that engage with both the inner tube junction and the outer tube, creating a nested configuration that reinforces the joint while maintaining thermal insulation.
2Reliability
If polyurethane resin is used as filling material, then good adhesion to the sleeve is achieved, but the material cannot withstand temperatures above 100°C for long-term marine operation
Solution Approach 1:
The joint fitting uses composite material construction where segments are made from high-temperature resistant materials such as reinforced polymers or metal alloys that can withstand marine operating temperatures up to 150°C or higher. These segments work together with the filling material to provide both adhesion and thermal resistance, creating a composite structure that overcomes the limitations of single materials.
3Temperature
If DiPolyCyclopentadiene (DPCD) is used as filling material, then temperature resistance up to 180°C is achieved, but significant thermal and chemical shrinkage occurs during curing
Solution Approach 1:
The segments are pre-installed around the inner tube junction before the DPCD filling material is injected. This preliminary placement of rigid segments provides a structural framework that compensates for the shrinkage that will occur during DPCD curing. The segments maintain the geometric integrity of the joint fitting throughout the curing process, preventing dimensional deviations.
Solution Approach 2:
The formulation of the DPCD filling material is modified by adding shrinkage-compensating additives or blending with other resins that have lower shrinkage rates. This changes the curing parameters of the material to reduce thermal and chemical shrinkage while maintaining high-temperature resistance. The adjusted material composition allows for more precise dimensional control during the curing process.
4Temperature
If DPCD material is used, then high temperature resistance is achieved, but poor adhesion with the walls of the sleeve and tubes results in gap formation
Solution Approach 1:
A primer or adhesion-promoting coating is applied to the inner tube junction and outer tube surfaces before injecting the DPCD filling material. This intermediary layer improves the chemical bonding between the DPCD and the metal surfaces, preventing gap formation. The primer acts as a mediator that enhances wetting and adhesion, ensuring reliable mechanical force transmission from the pipeline walls through the filling material to the segments and sleeve.
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 fitting enhances mechanical efficiency and extends the pipeline's lifespan by minimizing shrinkage and maintaining thermal insulation, suitable for both J and S laying methods without additional equipment, and compatible with existing injection machines.
Implementation Method 1
During its curing process, DPCD undergoes significant thermal and chemical shrinkage, equivalent to several percent by volume.
Implementation Method 2
a double-walled insulated sleeve arranged around the outer tubes and centered at the weld
Data Source
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AI summary
Disclosed is a pipe fitting (1) for a double-walled pipeline constituted by a set of sections (16a, 16b, …) comprising, in particular, an internal tube (2a, 2b) and an external tube (3a, 3b), intended to ensure the thermal insulation of the connection (5) between two successive sections (16a, 16b), and the transmission of mechanical forces, characterised in that the fitting (1) consists of at least one segment (10) arranged around the connection of the internal tubes (2a, 2b) of the two successive sections at the weld (17) of the internal tubes (2a, 2b) and held by a fastening system (11), a double-walled insulated sleeve (6) arranged around the external tubes (3a, 3b) and centred at the weld and a hardening filling material injected or poured between the sleeve (6) and the at least one segment (10) so as to fill the interstitial space defined by the internal tubes (2a, 2b) of the pipe, the at least one segment (10) and the insulated sleeve (6).