Drill Pipe Hardbanding at Low Temperature to Protect Polymer Coating
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Solution Overview
Problem
Conventional hardbanding re-application methods for drill pipe tool joints in the oil and gas industry face challenges in maintaining the integrity of the internal polymer coating and achieving the required Rockwell hardness, often resulting in rejected tool joints due to high preheating and welding temperatures that degrade the coating and exceed hardness specifications.
Innovation Solution
A method involving arc welding a consumable metal welding wire onto a tool joint with a surface temperature between 50° F to 170° F using direct current (DC) power supply, which forms a stringer bead weld zone with reduced heat affected zone depth, preserving the internal polymer coating and maintaining Rockwell hardness below 40 Rc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high preheating and welding temperatures (250°F to 600°F) are used in conventional hardbanding re-application, then the hardbanding material can be properly applied to the worn surface, but the internal polymer coating deteriorates and the base metal HAZ hardness exceeds industry specifications
Solution Approach 1:
The patent changes the temperature parameter from conventional high preheating (250°F to 600°F) to a lower temperature range (50°F to 170°F). This parameter change allows the hardbanding material to be properly applied while preventing polymer coating degradation and maintaining HAZ hardness below 40 Rc, thus resolving the contradiction between application quality and harmful effects
Solution Approach 2:
Instead of following the conventional approach of high temperature preheating followed by welding, the patent inverts the sequence by first cooling the tool joint to a lower temperature range (50°F to 170°F) before applying the hardbanding material. This inverted approach prevents the harmful thermal effects on the polymer coating while still achieving proper hardbanding application
2Object-affected harmful factors
If water cooling is introduced during the welding process to preserve the internal polymer coating, then the coating properties are maintained, but the base metal HAZ hardness increases to greater than 40 Rc
Solution Approach 1:
The patent changes the temperature parameter by cooling the tool joint to a lower range (50°F to 170°F) before and during the welding process, rather than using water cooling during welding. This parameter change achieves both goals: preserving polymer coating integrity and maintaining HAZ hardness below 40 Rc, thus resolving the contradiction between coating protection and hardness specification compliance
3Productivity
If conventional hardbanding re-application processes are used, then hardbanding material can be applied to worn tool joints, but additional coating processes are required and tool joints are frequently rejected
Solution Approach 1:
The patent changes the temperature parameter to a lower range (50°F to 170°F) during hardbanding re-application, which prevents polymer coating degradation and maintains HAZ hardness compliance. This eliminates the need for additional coating processes and reduces tool joint rejections, thus resolving the contradiction between productivity and process complexity
Solution Approach 2:
The patent applies preliminary cooling to the tool joint before hardbanding re-application to establish a temperature condition (50°F to 170°F) that prevents coating degradation and HAZ hardness exceedance during welding. This preliminary action avoids the need for subsequent corrective coating processes and reduces rejections, improving productivity while simplifying the overall process
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 effectively re-applies hardbanding while maintaining the integrity of the internal polymer coating and ensuring the tool joint meets industry hardness specifications, reducing the need for additional coating processes and minimizing tool joint rejection.
Implementation Method 1
arc welding a consumable metal welding wire to a previously applied hardband metal
Implementation Method 2
the arc welding power supply utilizes direct current (DC)
Data Source
AI summary
Various methods of hardbanding an apparatus are described. In one aspect of the invention an improved method of re-applying a hardbanding alloy to worn tool joints of a previously hardbanded drill pipe results in preservation of the metallurgical properties of the drill pipe and preservation of the internal polymer coating that lines the drill pipe. A method for applying hardbanding includes arc welding a consumable metal welding wire to a tool joint having a surface temperature that ranges from about 50° F. to about 170° F. and the arc welding power supply utilizes DC current. The method herein produces a hardbanded tool joint comprising a heat affected zone (HAZ) of a based metal having a Rockwell hardness of 40 Rc or less.