Pipeline safety has been a perennial concern for industries and technicians. Most pipeline damages result from issues like corrosion, incorrect handling, material, and weld failure. With large diameter pipes—especially as the large diameters pipes are used for critical oil or water transportation over a long distance—these damages are more likely.
Fortunately, techniques are available to improve the weld quality and increase weld integrity for large diameter pipes. In this article, we will examine advantageous large diameter pipe welding processes like narrow groove welding and v-bevel.
Processes for Large Diameter Pipe Welding
Pipes are considered “large diameter” if their bore size is larger than 16” (for elastic resistance welded pipes) or 20” (for longitudinal submerged arc welding pipes). Primarily used in offshore projects, LNG transmission, or water transportation, large diameter pipes can handle the high flow rates of such applications. However, damage in such pipes can be hazardous, and defects can occur as a result of:
- Incompatible material use.
- Corrosive environment.
- Stress due to external loads.
- Mishandling during installation.
Large diameter pipes often feature thicker walls to provide more chemical, thermal, and structural resilience. Damages to these pipes (of wide-ranging diameters and thicknesses) can be minimized to some extent during welding by utilizing proper preparation and weld techniques. Effective techniques include beveling and narrow groove welding when GTAW welding such pipes.
Beveling
The beveling process enables access to the entire pipe thickness. This facilitates the welding process while improving the quality of the result. Most manual processes use V-bevel instead of J-bevel for orbital welding.
For thicknesses of 3 to 26mm, the single v-bevel angle is between 40 and 60 degrees. For a thickness between 12 and 60mm, the compound v-bevel is ideal. For a large diameter pipe, a v-bevel is advantageous because:
- Distortion or shrinkage of the weld metal can be reduced.
- The bevel angles keep the weld joint from becoming too narrow while providing easy access to the roots and the entire pipe thickness.
- The double v-groove can help reduce the use of filler metal as well as the welding time.
Narrow Groove Welding
Welding relatively thick sections of large diameter pipes can be an expensive process. Additionally, challenges like lack of adequate penetration and inadequate joint strength are common. By using the narrow groove welding process, thick materials can be joined faster and with fewer consumables.
Usually, a J-bevel is machined at each face to form a U-profile. This profile has a narrow gap compared to the V-bevel. As a result:
- Less filler material is required to form a weld.
- The uniform deposition through the entire thickness of the pipe improves the strength and quality of the weld.
- Controlled heat input reduces thermal stress, minimizing the chance of shrinkage and cracking.
By using a specialized weld head such as the AMI Model 52 for orbital welding, welders can reach the narrow gaps when performing precision welding.
Choosing the Best Solution for Large Diameter Pipe Welding
With specialized preparation methods and the elimination of risk factors such as human fatigue, large diameter pipe welding can be performed safely, efficiently, and with expert precision. To do so, though, a process like orbital welding is required for increased speed, accuracy, repeatability, and productivity when welding large diameters or lengths of pipes.
The correct orbital welding solution is critical if manufacturers want to combine optimal productivity and unparalleled quality. AMI Model 15 orbital weld heads can weld pipes from 3” and greater, providing customization options to accommodate many configurations. Across industries, AMI provides cost savings while ensuring quality for a wide range of large diameter pipe welding applications.
Arc Machines, Inc. is an industry leader in producing high-quality orbital welding solutions, including a range of orbital welding machines and weld heads that can assist in large diameter pipe welding for your critical industry applications. For inquiries regarding products, contact sales@arcmachines.com. For service inquiries, contact service@arcmachines.com. Arc Machines welcomes the opportunity to discuss your specific needs. Contact us to arrange a meeting.
