Pipeline Buckling Prevention via Yield Strength Control
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Solution Overview
Problem
Buckling issues occur in the vicinity of girth-weld zones of steel pipes during coiling and uncoiling, particularly at the inner arc edge, due to strain differences and varying yield strengths, which affect the pipeline's deformation properties and bending resistance, especially when laid on the seabed.
Innovation Solution
Selecting steel pipes with carefully controlled yield strength differences and yield ratios, ensuring they satisfy specific relationships (ΔYS ≤ -1.75 × YR + 230 for round type steel pipes and ΔYS ≤ -0.69 × YR + 125 for YPE type steel pipes, and optimizing chemical compositions within defined ranges to minimize buckling, while ensuring the pipeline meets API specifications for X42 to X80 properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steel pipes are coiled around a drum for transport, then the pipeline can be transported to the ocean and laid on the seabed, but plastic strain and buckling occur at the inner arc edge of the coiling
Solution Approach 1:
The patent applies parameter changes by carefully controlling the yield strength difference (ΔYS) between adjacent steel pipes and the yield ratio (YR) to satisfy specific mathematical relationships. This controls the stress distribution during coiling and uncoiling, preventing plastic strain accumulation at the inner arc edge while maintaining the ability to coil and uncoil the pipeline for seabed laying operations
2Strength
If the yield ratio of steel pipe is decreased to improve work hardening properties, then bending buckling resistance of the steel pipe body is improved, but the girth-weld zone remains vulnerable to buckling
Solution Approach 1:
The patent applies local quality by recognizing that the girth-weld zone has different mechanical properties than the base metal. Instead of uniformly decreasing the yield ratio throughout the steel pipe, the invention controls the yield strength difference between adjacent pipes specifically at the weld zone interface. This localized control ensures that the weld zone maintains adequate buckling resistance while the overall pipe can still exhibit improved work hardening properties
Solution Approach 2:
The patent applies preliminary action by pre-establishing the yield strength relationship between adjacent steel pipes before coiling occurs. By selecting and assembling pipes with controlled yield strength differences in advance, the system prevents buckling at the girth-weld zone during subsequent coiling and uncoiling operations, rather than attempting to correct issues after they occur
3Ease of manufacture
If steel pipes with varying yield strengths are used in the pipeline, then manufacturing flexibility is improved, but buckling occurs more readily at weld zones due to strain differences
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships that control the yield strength difference (ΔYS) between adjacent pipes relative to the yield ratio (YR). This allows manufacturing flexibility in selecting pipes with different yield strengths while ensuring that the difference remains within bounds that prevent buckling at weld zones during coiling and uncoiling operations
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A pipeline is a pipeline having plural weld zones in which ends of plural steel pipes are joined by welding, the plural steel pipes are produced from plural charges of molten steel having one or more steel compositions; yield point elongation is not present on a stress-strain curve obtained when stress is applied in a longitudinal direction of each of the steel pipes; a thickness of each of the steel pipes t (mm) and an average pipe outside-diameter D (mm) satisfy t/D×100≤6; and in the plurality of the weld zones, ΔYS which is a yield strength difference between one steel pipe and the other steel pipe that are welded to each other (MPa), and YR representing a yield ratio that is a ratio of the yield strength to tensile strength of a pipe having a lower yield strength out of the one steel pipe and the other steel pipe, satisfy ΔYS≤-1.75×YR+230.