Pipe welding is particularly challenging because it requires welders to continuously transition through flat, horizontal, vertical, and overhead positions. To address the difficulties that vertical and overhead positions pose, welders employ specialized techniques. Below, we discuss some of these different welding techniques and how orbital welding can improve the efficacy of these techniques in high-specification projects.
Different Welding Techniques Used in Arc Welding Processes
Discussed below are some of the commonly used welding techniques for various arc welding processes—
Oscillation
The side-to-side manipulation of a weld in progress, better known as oscillation, is measured in terms of amplitude, frequency, and dwell time. The oscillation amplitude is critical in determining the geometry of weld joints and their width at different welding speeds. An increase in welding speed results in decreased oscillation amplitude and vice-versa. Oscillation can ensure proper fusion across the width of the weld. There are several ways to oscillate a weld, including:
- Ensures Worker Safety: Mechanized welding process removes the welder from the fall line of the molten metal in the overhead welding position. By operating a weld head through a remote pendant, a welder has far more flexibility to efficiently weld pipes located in difficult or previously inaccessible positions.
- ‘Walking the Cup’ technique: In the Gas Tungsten Arc Welding (GTAW) process, welders deploy the ‘walking-the-cup’ technique by placing the cup of the torch against the workpiece to increase bead width and improve tie-in at the weld’s toe. Compared to conventional GTAW welding, this technique helps minimize the welder’s fatigue when welding pipes or tee joints.
Uphill Welding
One of the two options for vertical welding is to go against the pull of gravity by welding uphill. Piping used in petroleum refineries is thick and requires a greater level of penetration that uphill vertical welding can provide. While implementing this technique, a welder needs to go slowly to fight gravity’s pull on molten metal and keep the molten metal in place by creating special patterns for each pass and pausing long at each point in the pattern. This results in improving penetration of the fill material into the metal and yields greater sidewall fusion. However, the time needed to push the molten material uphill, the patterns used, and the dwell time transfers a significant amount of heat into the metal that can cause the workpiece to distort.
Downhill Welding
Downhill pipe welding is primarily used to join longer pipeline sections in crude oil refineries. Compared to uphill welding, downhill welding is easier and faster. Additionally, it lets the welder produce an acceptable weld by using Flux Core Arc Welding (FCAW), Gas Metal Arc Welding (GMAW), or Shielded Metal Arc Welding (SMAW). One major challenge of downhill pipe welding is to keep the molten pool from outrunning the arc. As a result, the arc dwell time on any point of the weld is significantly reduced, along with fusion and material deposition. There are risks of weld contamination and inclusions if the molten metal overruns the electrode. This is why downhill pipe welding is recommended exclusively for thin materials with a material thickness of 12.5 millimeters, where the speed of movement is less susceptible to creating weld defects such as lack of fusion.
The specific challenges of different welding positions and the associated techniques used in arc welding processes can be easily addressed through automated welding processes such as orbital welding.
Deploying Orbital Welding for Different Welding Techniques
Orbital welding automates the process for bonding pipes and tubes by letting the electrodes that create the work area, including weld puddle and coverage, rotate continuously around the outer surface of the workpiece. Under the guidance of a programmed welding controller, automated orbital welding can be especially helpful for maneuvering vertical and overhead welding positions and improving the different welding techniques.
Deploying orbital welding for overhead pipe welding, uphill welding, or downhill welding offers the following advantages:
- Ensures Worker Safety: Mechanized welding process removes the welder from the fall line of the molten metal in the overhead welding position. By operating a weld head through a remote pendant, a welder has far more flexibility to efficiently weld pipes located in difficult or previously inaccessible positions.
- Enhances weld purity: In manual pipe welding that requires multiple passes, a welder can make a mistake while striking an arc that disrupts the shielding gas and contaminates the weld. Orbital welding eliminates such risks of weld contamination by making each pass in a continuous circuit around the circumference of the pipe. By minimizing welder fatigue in pipe welding uphill or downhill manually, orbital welding enables operators to weld large sections of pipeline at an exceptional speed and yield high-quality welds.
- Promotes weld consistency: In orbital welding, the consistent travel speed of the torch is maintained through weld heads that are either clamped around a pipe or mounted to it. And by maintaining a consistent distance from the weld around the entire pipe, orbital welding helps ensure weld consistency.
Automated orbital welding can help accomplish flawless, high-quality pipe welds through the optimization of different welding techniques. The benefits of orbital welding in high-specification and low-tolerance environments are best realized with state-of-art equipment, materials, and support.
Achieve High-Quality Nuclear Welding Results
For narrow-gap welding, tube-to-tube sheet welding, or other nuclear welding needs, orbital welding produces unparalleled output. The control and precision offered with automated processes such as orbital welding can reduce weld defects while enhancing weld strength. When thinking of fusion vs fission power, either reactor must ensure safe and effective operation. Safety, monitoring, and reliability offered by orbital welding allow manufacturers to meet strict nuclear welding standards for nuclear reactors and their ancillary equipment.
Arc Machines, Inc. is an industry leader in developing advanced and high-quality welding equipment. For inquiries on how we can help you apply orbital welding to different welding techniques, contact sales@arcmachines.com. For service inquiries, contact service@arcmachines.com. Contact us to learn more about custom orbital welding solutions.
