Pipe-Section End Heating for Reel-Lay Seam-Welded Pipelines
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Solution Overview
Problem
Seam-welded pipes used in offshore oil and gas applications often have high yield-to-tensile ratios and low elongation due to cold forming, making them unsuitable for reel-lay installation without costly heat treatment or Strain Based Design, which increases costs and requires cumbersome equipment.
Innovation Solution
A method involving heating specific portions of seam-welded pipe-sections to 500°C for 2 minutes, with adjacent portions maintained at a lower temperature, to reduce residual stress and improve mechanical properties, allowing for reel-lay installation without additional costly equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If seam-welded pipes are used for cost-effectiveness, then manufacturing cost is reduced, but yield-to-tensile ratio increases and elongation decreases making them unsuitable for reel-lay installation
Solution Approach 1:
The pipe is divided into two distinct portions: a first portion (3%-40% of total length) that undergoes heat treatment to reduce residual stress and improve elongation for reel-lay installation, and a second portion that maintains the original cold-formed properties. This segmentation allows only the critical end sections to be modified while preserving the cost advantages of seam-welded construction for the majority of the pipe length.
Solution Approach 2:
Heat treatment is applied locally only to the first portion of the pipe (3%-40% from one end) rather than the entire pipe. This local quality change reduces residual stress and improves mechanical properties (elongation ≥8%, Y/T ratio ≤0.9) in the critical regions where reel-lay installation stresses are concentrated, while maintaining cost-effectiveness by treating only necessary sections.
2Reliability
If heat treatment is applied to the overall pipe-section to reduce residual stress, then mechanical properties improve for reel-lay installation, but manufacturing cost significantly increases due to specific equipment requirements
Solution Approach 1:
The heat treatment process is segmented to affect only the first portion (3%-40% of length) rather than the entire pipe. This reduces the volume of material requiring heat treatment, thereby reducing equipment size requirements, energy consumption, and overall manufacturing cost while still achieving the necessary mechanical property improvements in the critical end sections.
Solution Approach 2:
The heat treatment is applied locally to specific portions of the pipe where residual stress most critically affects reel-lay performance. This localized approach improves mechanical properties (elongation and Y/T ratio) where needed without incurring the full cost of treating the entire pipe, making the process economically viable.
3Reliability
If the first portion of the pipe is heated to 500°C for 2 minutes, then residual stress is reduced and mechanical properties improve, but energy consumption increases
Solution Approach 1:
Heat treatment is applied partially to only the first portion (3%-40% of length) rather than the entire pipe, and for a limited duration (2 minutes minimum). This partial action is sufficient to reduce residual stress and improve mechanical properties in the critical regions where reel-lay stresses are concentrated, while minimizing overall energy consumption compared to full-pipe treatment.
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 method reduces residual stress and improves mechanical properties, making seam-welded pipes suitable for reel-lay installation while maintaining cost-effectiveness and avoiding the need for cumbersome equipment.
Implementation Method 1
heating at least the first portion L1 to at least a first temperature T1 of at least 500°C for at least 2 minutes
Implementation Method 2
reducing residual stress within said pipe-section
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A method of preparing a pipe-section for welding to another pipe-section to form a pipeline comprising a plurality of said pipe-sections, the method comprising at least the steps of: (i) providing a pipe-section having first and second pipe-ends; (ii) defining a first portion L1 of the longitudinal length of the pipe-section from the first pipe-end being in the range 3% to 40% of the overall length of the pipe- section; (iii) defining a second portion L2 of the longitudinal length of the pipe-section from the end of the first portion L1 towards the second pipe-end; (iv) heating at least the first portion L1 to at least a first temperature T1 of at least 500°C for at least 2 minutes; (v) maintaining a second temperature T2 of the second portion L2 during step (iv) below the first temperature T1. The invention is able to reduce the strain capacity during reel-laying of a pipeline formed from a plurality of pipe sections formed by the invention.