The Narrow Gap Welding Process: Advantages of Choosing Narrow Groove Welding

AMI’s orbital welding solution for nuclear application

Welding thick metal workpieces is a challenging process, mechanically and economically. A conventional welding procedure is generally not effective for the metal thickness equal to or more than 12.5 mm (1/2 inch). Narrow gap welding (also known as narrow groove welding) can weld thicker base metals in a cost and time-efficient manner.

During welding preparation, the workpieces are beveled at an angle, commonly 30 to 37.5 degrees, for V-groove welding. The gap created is then closed by introducing filler metals during the welding process. This is the standard method used to join thick plates and pipe walls. 

A narrow gap weld, on the other hand, uses a J-groove at each face of the metal to be welded. If the V-groove were applied on thick workpieces, the bevel angle would create a large gap. Instead, a narrow gap weld forms a U-shaped profile, which creates a small gap and can be welded with less filler material in a shorter time.

This efficiency makes narrow gap welding a popular choice among many industries for applications that include the fabrication of thick wall pipes, pressure vessels, and rotor shafts for steam turbines.

Advantages of the Narrow Gap Welding Process

Industries that include power generation, nuclear, oil and gas, and industrial fabrication use the narrow gap welding process. Discussed below are some of its advantages: 


The narrow gap welding process is desired for its cost-effectiveness. The reduced weld time and less filler material make it an economical option.

  • With a reduced angle, there is less gap to fill and less material required.
  • The smaller gap can be filled in less time and provide faster weld completion.
  • An increased production results in faster and more economical weld completion.

Reduced Residual Stress and Distortion

Narrow gap welding has a low weld volume and uses low heat input to perform the weld. Controlled heat input during the welding process reduces thermal stress and the chances of fracture, corrosion, and weld distortion. Additionally, reduced thermal stress lessens residual stress and increases the durability and longevity of the weld.

High Weld Quality

Due to less material thickness on the root, the V-groove joint can have a weaker root weld joint. Narrow gap welding provides a nearly parallel groove joint that improves the strength and quality of the weld. Weld strength is also increased by the stress reduction on the root weld.

Selecting the correct welding process can further enhance the benefits of narrow gap welding. For a high-quality result, the orbital gas tungsten arc welding method (GTAW) can be the best option.

Automated Orbital GTAW for Narrow Groove Welding

Orbital welding is an automated welding process where the movement of the welding electrode is computer-controlled. The electrode is attached to the weld head that rotates mechanically along the static workpiece to perform a uniform and high-quality weld. This process eliminates the human limitations of fatigue and flexibility in gas tungsten arc welding (GTAW). For heavy-duty industrial applications, specially-designed orbital weld heads such as AMI’s Model 52 provide precision and help maintain strict quality requirements.

Orbital GTAW enhances the welding process by providing the consistency and control required to develop a high-quality result. This process reduces weld time and cost while ensuring the precision required by the narrow gap welding process to ensure strong and durable welds.


Arc Machines, Inc. is the recognized leader in narrow gap orbital welding. For more information on how AMI machines perform the narrow groove welding process, contact For service inquiries, contact Contact us to learn more about custom orbital welding solutions.