Underwater Pipe Joint Assembly for Corrosive Fluid Welding
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Solution Overview
Problem
Existing methods for assembling underwater pipes carrying corrosive fluids are complex and costly, often requiring multiple welds and tubular junction sleeves to ensure sealing and corrosion resistance, while also posing challenges in terms of fatigue resistance and mechanical performance.
Innovation Solution
A method for assembling underwater pipe elements by directly welding the ends of pipe elements coated with a thermoplastic liner and a layer of corrosion-resistant steel alloy, using a compression ring to ensure sealing and corrosion resistance without the need for tubular junction sleeves or additional steel connecting pieces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tubular junction sleeves are used to ensure sealing and corrosion resistance at welds, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention removes the tubular junction sleeve component entirely from the assembly. Instead of using a separate sleeve to protect the weld, the corrosion-resistant coating is applied directly to the pipe ends themselves, extracting the protective function from a separate component and integrating it into the base structure.
Solution Approach 2:
The protective corrosion-resistant coating is merged with the pipe end structure. The coating serves dual purposes: it prepares the surface for welding and simultaneously provides corrosion protection at the weld zone, eliminating the need for separate protective components like junction sleeves.
2Reliability
If multiple welds and connecting pieces are used to ensure corrosion resistance, then corrosion protection is improved, but manufacturing cost and assembly complexity increase
Solution Approach 1:
The invention eliminates the steel connecting piece component and extracts the corrosion protection function to be provided by the coating system alone. This removes the need for additional materials and reduces manufacturing costs while maintaining corrosion resistance.
Solution Approach 2:
The corrosion-resistant coating serves multiple functions: it provides corrosion protection during welding, ensures proper weldability of the steel alloy, and maintains long-term corrosion resistance at the joint. This multi-functionality eliminates the need for separate protective components.
3Reliability
If thermoplastic liner coating is applied to pipe ends before welding, then corrosion resistance is improved, but the coating cannot tolerate high welding temperatures
Solution Approach 1:
The protective coating system is segmented into two distinct layers with different functions: a thermoplastic liner coating for general corrosion protection and a corrosion-resistant steel alloy coating at the weld zone for high-temperature welding tolerance. Each layer is optimized for its specific function without compromising the other.
Solution Approach 2:
The pipe surface is given different local properties: the thermoplastic liner coating is applied to areas not subject to welding (lower temperature zones), while a heat-resistant corrosion-resistant steel alloy coating is applied specifically to the weld zone where high temperatures will be encountered. This local differentiation allows each material to perform optimally in its designated area.
4Reliability
If compression ring is used to ensure sealing at the liner-weld interface, then sealing reliability is improved, but device complexity increases
Solution Approach 1:
The compression ring is pre-installed on the pipe before the thermoplastic liner coating is applied. This preliminary action ensures that the sealing interface is established before the liner is in place, allowing the liner to be molded around the ring and creating an integrated sealing system without requiring additional assembly steps later.
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 method provides reliable sealing, corrosion resistance, and fatigue resistance at the welds, while minimizing mechanical resistance losses and operational complexity, and can be efficiently implemented with reduced on-board welding on pipelay vessels.
Implementation Method 1
a layer of corrosion-resistant steel alloy on a terminal part of length L1 of the internal wall of each pipe element
Implementation Method 2
the internal wall of which is partially lined by a protective coating of plastic material of the liner type
Implementation Method 3
the crimping of a first annular part of length L4 of said compression ring against the pressure side face of the terminal part of said protective coating of plastic material
Implementation Method 4
the assembly by welding directly together the ends to be welded of two pipe elements by a corrosion-resistant steel alloy weld
Data Source
AI summary
A method for producing a steel underwater pipe for carrying a corrosive fluid, includes the successive steps: applying a layer of corrosion-resistant steel alloy on a terminal part of the internal wall of each pipe element from its end to be welded; the application of a plastic coating, on the internal wall of each pipe element; covering only a first part of the layer of metal alloy, a terminal part of the layer of metal ally on the side of the end to be welded of each pipe element not being covered by the plastic coating; the coaxial insertion and the crimping of a compression ring against the terminal part of the plastic coating; and the assembly by welding directly together the ends of two pipe elements by a corrosion-resistant steel alloy weld.