Pipe Ring Testing for Subsea Pipeline Wall Thickness
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Solution Overview
Problem
Current methods for testing deep-water pipelines to withstand external pressure collapse are expensive, time-consuming, and insufficient for confident risk management, especially for long pipelines, due to the high cost and limited availability of pressure chamber tests, and the statistical risk of a single out-of-specification joint causing failure.
Innovation Solution
A method involving cutting a ring from a pipeline, forming flat surfaces for sealing, and measuring strain and deformation in a pressure chamber to determine optimal wall thickness, allowing for cost-effective and comprehensive testing of pipe samples to replicate external pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete pipe joints are tested in pressure chambers to ensure safety against external pressure collapse, then reliability of the pipeline is improved, but the cost and time required for testing increases significantly
Solution Approach 1:
The patent divides a complete pipe joint into a smaller representative segment (a ring or short section) for testing. This segmented approach maintains the structural integrity needed to assess collapse resistance while dramatically reducing the size and cost of testing. The ring specimen is designed to replicate the stress conditions of a full joint but requires minimal test setup time and chamber space.
Solution Approach 2:
The patent creates a simplified copy (ring specimen) that replicates the critical structural characteristics of the complete pipe joint without requiring the full joint itself. The ring is fabricated to match the pipe's wall thickness, diameter, and material properties, allowing it to serve as a representative model for assessing collapse resistance under external pressure.
2Reliability
If wall thickness is increased to reduce the statistical risk of collapse in long pipelines, then reliability is improved, but the cost and commercial viability deteriorates
Solution Approach 1:
The patent uses systematic variation of geometric parameters (wall thickness, diameter, length) in ring specimens to establish empirical relationships between these parameters and collapse pressure. By testing multiple rings with different parameters, the invention creates a database that allows optimization of wall thickness to the minimum required for safety, eliminating the need for excessive thickness increases.
Solution Approach 2:
The patent employs inexpensive ring specimens that can be rapidly fabricated and tested compared to complete pipe joints. These disposable test rings allow for extensive testing of different wall thicknesses and configurations at low cost, enabling the identification of the minimum safe thickness without committing to increased thickness for the entire pipeline.
3Ease of manufacture
If theoretical studies and numerical modelling are used to calculate maximum water depth, then cost is reduced, but the reliability and confidence in risk management deteriorates
Solution Approach 1:
The patent creates a self-validating testing system where ring specimens are tested under controlled external pressure to generate empirical data that directly validates or refines theoretical models. The test results provide real-world confirmation of numerical predictions, building confidence in both the theory and the risk assessments without requiring expensive full-scale joint testing.
4Reliability
If design codes incorporate safety factors based on limited test data, then reliability is improved, but the wall thickness and cost increase
Solution Approach 1:
The patent performs preliminary testing with ring specimens during the design and fabrication stage to establish accurate collapse pressure characteristics before the pipeline is installed. This advance testing provides empirical data that allows for more precise safety factors, eliminating the need for overly conservative wall thickness increases that would result from using generic safety factors based on limited historical data.
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
This approach enables efficient and cost-effective testing of pipe samples, providing a more reliable basis for design codes and reducing the need for excessive wall thickness, thereby enhancing the commercial viability and safety of deep-water pipelines.
Implementation Method 1
increasing the pressure outside the ring and measuring the strain and deformation on the ring as the pressure increases
Implementation Method 2
the deformations that lead to external pressure collapse are uniform along the pipe and that therefore the occurrence of external pressure collapse will be the same for a ring cut from the pipe as for the complete joint length of pipe
Data Source
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AI summary
A method of testing pipes for use in making subsea pipelines comprises cutting a ring from one or more pipes of the type used to make the pipeline; forming flat, substantially parallel surfaces on the ends of the ring; providing means for measuring strain and deformation of the ring; mounting the ring in a pressure chamber such that the ends of the ring form seals with opposing walls of the chamber to isolate the inside of the ring from the outside; increasing the pressure outside the ring and measuring the strain and deformation on the ring as the pressure increases; and using the deformation and strain measurements to determine a wall thickness for pipes to be used for the pipeline. An apparatus for testing rings cut from pipes for use in making subsea pipelines, comprises first and second test chamber sections which, when placed together define a test chamber for receiving the ring to be tested; one or more sensors for measuring strain and deformation of the ring; sealing means located in the chamber for forming a seal against the ring when received in the chamber; means for clamping the first and second sections together to form the chamber and engage the sealing means against the ring when received in the chamber to form a pressure resistant seal between the inside and outside of the ring; and a fluid inlet port in one of the chamber sections to allow a pressurised fluid to be admitted to the chamber outside the ring when received in the chamber.