Movable Die Polymer Coating for Field-Joint Corrosion Protection
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Solution Overview
Problem
Field-welded joints in polymer-coated steel pipes are prone to corrosion due to inadequate protection, and existing coating methods are either difficult to use in field conditions or fail to provide sufficient corrosion resistance.
Innovation Solution
A method and apparatus for applying a polymer coating using a movable die and nozzle to form a melt film or sheet on the pipe surface, which includes a leveling mechanism to ensure a tight and hermetic seal, allowing for efficient application in various weather conditions and field environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coating methods (shrink-sleeve, spray guns, machine taping) are used for field-welded joints, then some provide good coating results, but they are difficult or impossible to use in field conditions
Solution Approach 1:
The invention changes the physical state of the polymer material from solid (conventional methods) to melt form, enabling application in field conditions. The movable die applies polymer melt directly to the joint, and the polymer solidifies upon cooling to form a protective coating, resolving the contradiction between coating quality and field usability.
Solution Approach 2:
The invention employs a movable carriage that can travel around the periphery of the pipe, allowing the die to access different positions of the joint dynamically. This dynamic positioning system enables complete coverage of the welded joint in field conditions while maintaining consistent coating quality through controlled movement.
2Ease of operation
If conventional coating methods are used for field-welded joints, then some are easy to apply in field conditions, but they fail to provide adequate protection against corrosion
Solution Approach 1:
By changing the polymer application method to melt form extrusion through a movable die, the invention achieves both ease of field application and reliable corrosion protection. The melt form allows complete penetration and coverage of the joint area, while the controlled cooling and solidification process ensures adequate thickness and protective properties.
Solution Approach 2:
The movable carriage enables continuous application of the polymer coating around the entire periphery of the joint in a single operation. This continuous action ensures complete coverage without gaps or missed areas, providing reliable corrosion protection while maintaining ease of field operation.
3Reliability
If a polymer coating is applied on the entire pipe surface at the factory, then corrosion resistance is improved, but weld-joining at the construction site becomes difficult
Solution Approach 1:
The invention segments the coating application process into two distinct phases: factory coating of the pipe body and field coating of the joint area. This segmentation allows the pipe to be welded at the construction site with uncoated ends, followed by application of polymer coating specifically on the joint area, thus resolving the contradiction between corrosion resistance and weld-joining ease.
4Ease of manufacture
If field-welded joints are left uncoated to facilitate welding, then weld-joining becomes easier, but the joints become sensitive to corrosion
Solution Approach 1:
The invention applies polymer coating to the joint area after welding is completed, serving as a preliminary protective action against corrosion. The movable die system enables this post-weld coating application in field conditions, ensuring that the joint receives adequate corrosion protection without compromising the ease of welding operation.
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 and apparatus provide a reliable and efficient coating that matches factory-quality results, offering excellent corrosion protection and ease of use in field conditions, suitable for both new and repaired polymer coatings on pipes and joints.
Implementation Method 1
applying at least one polymer material in the form of a melt film or sheet on the surface of the pipe or pipe section from a moving die
Implementation Method 2
The melt polymer film or sheet is applied on the pipe from a die which is mounted on a carriage, which can be moved along the periphery of the pipe or pipe section
Data Source
AI summary
Method and apparatus for coating a pipe or a pipe section with a layer of at least one polymer. The method includes providing the pipe or the pipe section having an outer surface defining the periphery of the pipe or the pipe section; applying on the outer surface of the pipe or pipe section a layer of at least one polymer material in melt stage using a nozzle, which is mounted on a carriage capable of travelling along the periphery of the pipe or the pipe section; and moving the carriage along at least a part of the periphery during the application of the polymer material to form a layer on the surface of the pipe or the pipe section that is particularly useful for coating field joints in pipelines.