What is Orbital welding?
Orbital welding is a specialized area of welding whereby the arc is rotated mechanically through 360° (180 degrees in double up welding) around a static workpiece, an object such as a pipe, in a continuous process.
This method and technology was developed to address the issue of operator error in manual gas tungsten arc welding (GTAW) applications requiring precision tube and pipe welding. To ensure high-quality repeatable welds a more stringent weld criteria was set by the ASME.
In orbital welding, an automated computer-controlled process runs with little intervention from the operator.
The orbital welding process can create high quality repeatable welds with the use of a computer, meaning that there is little need for intervention from a welding operator.
The process is used for two main applications; tube-to-tube / pipe-to-pipe joining and tube-to-tube sheet joining.
The process was originally developed by the aerospace industry in 1960 by Roderick Rohrberg of North American Aviation to address fuel and hydraulic fluid leakages in the X-15 rocket research plane.
In the 1980s, improvements in control systems, portability and power supplies meant that orbital welding machines could be transported between construction sites.
Equipment Needed for Orbital Welding
Orbital welding relies on specialized equipment to achieve its remarkable results. This section explores the essential components of an orbital welding system, their functions, and the variations available for different applications.
The main parts of an orbital welding system are the power supply (including an integrated computer control), the welding head and, as required, a wire feed system.
In addition, certain sized parts or materials will also require the use of a water/coolant system. Here we will look at each in turn:
- Programmable Power Supply: The programmable power supply allows you to set a range of different parameters, including the current intensity, pulse rate, flow of shielding gas, the welding head travel speed, and wire feed options. Ideally, the power supply should be light enough for one person to carry, be capable of controlling at least four axes, and should be compact
- Orbital Welding Heads: You may require different sized heads for different applications, but in all cases, your weld head should hold the electrode in place, manage the flow of the welding current, maintain an optimal temperature, and apply pressure on the workpieces being welded
- Wire Feeder: The wire feeder, when required, can be welded into the head of the device or part of a separate system
- Water/Air Coolant System: Using either air or water, the coolant system prevents the welding equipment from overheating, while also protecting the welding operator from the process’ heat input
How Does Orbital Welding Work?
Orbital welding uses a specialised machine that clamps the tube or pipe to be welded while the welding arc rotates around the workpiece (in an ‘orbit’).
Because the welding parameters are set by a microprocessor, the settings can be stored and reused, making this a highly repeatable process.
Before you start an arc, there are several important steps to make sure the piece is ready for the weld.
Step 1. Cut
Before aligning tube or pipe ends, they first need to be cut. Orbital saws rotate evenly around the piece, creating a clean and even cut. This is commonly used on sanitary tubing and small thin-walled pipe.
For larger applications, use a clamshell to cut (and even bevel) through large pipe. A sturdy blade will part even the toughest pipe to get it ready for welds.
If you do not have a clamshell, a band saw can be used.
Step 2. Face or Bevel
Tube and thin-walled pipe: After cutting, use a tube facing tool to get rid of burrs and other imperfections.
Though it is often overlooked, creating a perfect alignment is an important part of creating a good weld, in both orbital and hand welding. Burrs in welds can create a space for bacteria to build and contaminate in the future.
Pipe: Use a portable pipe beveling tool before orbital pipe welding. A bevel is needed to create full penetration on heavy walled pipe. Though there are several types of bevels, a “J-prep” is one of the most common for this type of automated welding. Filler wire is later added during the weld to make up for the missing material.
Step 3. Clean
This step is extremely important, especially in sanitary welding stainless steel. Cleaning the tube or pipe gets rid of potential contaminants and puts you in the best position for a successful weld.
Step 4. Tungsten
To strike an arc, you’ll need an electrode. In this case, it will be ceriated tungsten. The size and length depend on your application – O.D. sizes and wall thickness are a few of the factors to consider. The number of welds per piece of tungsten depends on the quality of the tungsten as well as the material and O.D. of the workpiece.
Once you have the appropriate piece, place it within the weld head in the tungsten holder.
Step 5. Align
In orbital fusion welding, the fit-up is extremely important when it comes to the penetration of the weld. Place the two ends together inside the weld head, ensuring they are lined up with the tungsten electrode. Then, simply clamp both sides down.
If you are welding with filler wire, you will need to tack the two pieces together or use a clamping device to put the two ends together. Then, the weld head will need to be aligned with the joint. The tungsten, wire angle, and wire distance can be adjusted as needed with the remote pendant.
Step 6. Purge
After aligning, purge oxygen from the inside of the tube or pipe, using argon or mixed shielding gas. If you try to perform a weld without purging, the oxygen present will cause discoloration and imperfections greatly impacting the integrity of the weld.
Purging also helps keep the weld from sinking in during wire-add applications by maintaining pressure on the inside of the pipe.
Use purge plugs, back purge wands, or purge trees to diffuse the chosen inert gas evenly into the tube or pipe.
Basic purging can be done with heat-resistant tape, but you sacrifice the consistency provided by purge plugs. With your workpiece purged of all traces of oxygen, you are ready to start an arc.
STEP 7. Program
Today’s power supplies feature auto-programming technology. It is as simple as entering the weld head being used, material being welded, O.D. size, and wall thickness into the power supply.
The power supply will then generate a pre-developed program. Often very little adjustment will need to produce an accurate weld program. Otherwise, the operator will need to program the following to develop a program:
- 4 or more welding levels (must include enough time for tie-in before the downslope)
- Control welding speed
- Adjust amperage to get uniform, fully penetrated welds
To fully understand programming needs, schedule orbital welding training. You will get in-depth details and hands-on experience while learning from an orbital welding expert.
Step 8. Weld
With all these steps completed, you are ready to strike an arc. The tungsten will then rotate 360 degrees around the workpiece to create a uniform weld.
We recommend testing an initial weld and making adjustments to the welding parameters as needed for your application.
Orbital Welding Parameters
Orbital welding, like any welding process, requires careful selection and control of various parameters to achieve optimal results. These parameters directly influence the quality, strength, and appearance of the weld. This section delves into the essential orbital welding parameters and their impact on the outcome.
Welding Current and Voltage
Current (Amperage): Determines the amount of heat generated in the arc, which directly affects the weld penetration and deposition rate. Higher current leads to deeper penetration and faster welding speeds, but it can also increase the risk of distortion or burn-through, especially in thin materials.
Voltage (Arc Voltage): Influences the arc length and stability. Higher voltage results in a longer arc and wider weld bead, while lower voltage creates a shorter arc and narrower bead. The optimal voltage depends on the welding process, material thickness, and desired welding characteristics.
Welding Speed
Travel Speed: The speed at which the weld head orbits around the workpiece. It must be carefully balanced with the heat input (current and voltage) to ensure proper fusion and prevent defects like lack of penetration or undercut. Thinner materials generally require faster welding speeds, while thicker materials need slower speeds to allow for adequate heat input.
Arc Length
Arc Length Control: Maintaining a consistent arc length is crucial for welding quality and consistency. Variations in arc length can lead to inconsistent penetration, porosity, or other defects. Orbital welding systems often use automatic voltage control (AVC) or arc voltage control (AVC) to maintain a stable arc length.
Shielding Gas Selection and Flow Rate
Shielding Gas: The choice of shielding gas (argon, helium, or mixtures) depends on the material being welded and the desired weld properties. Inert gases like argon and helium provide excellent protection against atmospheric contamination, while active gases like carbon dioxide can be used for specific applications.
Flow Rate: The flow rate of the shielding gas is critical for ensuring adequate coverage of the weld pool and preventing oxidation. Too low a flow rate can lead to porosity, while too high a flow rate can cause turbulence and disrupt the arc.
Wire Feed Speed (for GMAW/MIG and FCAW)
Wire Feed Speed: In GMAW/MIG and FCAW processes, the wire feed speed determines the amount of filler metal added to the weld. It must be balanced with the welding speed and current to achieve the desired weld bead size and profile.
Additional Considerations
Pre- and Post-Flow of Shielding Gas: Purging the weld area with shielding gas before and after welding helps to prevent contamination and improve weld quality.
Pulse Parameters (for Pulsed Current Welding): Pulse frequency, peak current, and background current must be carefully adjusted to achieve the desired weld characteristics.
Oscillation (for Weaving): In some cases, the weld head may oscillate or weave to create a wider weld bead. The amplitude and frequency of oscillation need to be controlled to avoid defects.
By understanding and optimizing these parameters, welders can achieve consistent, high-quality orbital welds that meet the stringent requirements of various industries.
Proper parameter selection is key to unlocking the full potential of orbital welding technology and ensuring the success of critical applications.
Types of Orbital Welding Processes
1. Gas Metal Arc Welding (GMAW).
This wire feed welding process utilizes an inert shielding gas such as carbon dioxide, argon, or helium to prevent weld contamination; the consumable electrode is fed wire continuously as it travels.
Also known as Metal Inert Gas (MIG) welding, it is the most common form of wire feed pipe welding and is the fastest common welding practice.
However, with unreliable and unpredictable sidewall fusion and penetration, GMAW is a gamble for high-specification projects and often requires reworking.
2. Flux Core Arc Welding (FCAW).
Utilizing wire with a core of flux as an electrode, the FCAW welding process is forgiving and offers welders more options to approach the weld. The flux core shields the weld from contaminants and is less easily disrupted by environmental factors.
FCAW can be used in remote locations with little or no shelter from the outside environment. However, the flux core requires more amperage to start the arc than a gas shielded process like GMAW or GTAW, making it difficult to utilize FCAW for welding thin-walled materials.
Excess heat can increase the chances of heat distortion, even in thick-walled stainless steels. And increased heat distortion during welding can make meeting specifications more challenging.
3. Gas Tungsten Arc Welding (GTAW).
GTAW welding utilizes a tungsten electrode that creates a narrow arc directed at the workpiece with an inert shielding gas preventing oxidation and other contamination during welding.
The high degree of control in the welding process yields precise and consistent welds. Carefully controlled gas promotes weld purity that makes stronger welds.
The process is also deployable in a variety of environments. With enough wind screening and forethought, operators can set up GTAW in an outdoor environment; this, however, is rare.
However, compared to other welding processes, GTAW is complex and is difficult to learn. Mastering GTAW requires a great deal of practice.
4. Plasma Arc Welding (PAW).
Considered a more advanced type of GTAW welding, PAW uses two kinds of gas, one for shielding the weld and the other for generating plasma.
Like the TIG welding process, plasma arc welding utilizes a tungsten electrode to create a plasma arc, generating heat.
The benefit of plasma arc welding is the arc control that produces superior quality welds regardless of material thickness.
However, the larger heat-affected area created by PAW (compared to TIG welding) can cause heat distortion or metal stresses that can weaken or ruin the workpiece. Also, the welding process utilizes large weldheads, limiting PAW’s range of environments.
5. Submerged Arc Welding (SAW).
As one of the older welding processes, SAW utilizes a continuously fed wire as an electrode, with the flux falling out of the hopper and burying the weld as it progresses.
Although the process yields high-quality welds and is very fast, it is limited to welding in a fixed and, generally, flat position. Process immobility and increased material consumption mark the main disadvantages of SAW.
6. Laser Beam Arc Welding.
This fusion welding process utilizes laser beams to join metal pieces. It is widely performed in high-volume applications using automation, such as the automotive industry.
Because of its energy density, the laser beam arc welding process enables operators to melt the area located at the edges of the joint without affecting a large area.
The high aspect ratio welds produced with a relatively low heat input compared to other arc-welding processes is one of the major advantages of deploying this welding process.
However, laser beam arc welding is expensive, and the equipment size limits its usage to purpose-built environments.
When to use Orbital Welding
It can be difficult to achieve high levels of safety and quality when using manual welding in certain positions, such as down-hand and overhead.
The restricted access afforded to the user can lead to faulty welds as the welder struggles to maintain control over the weld pool with a balance between surface tension and gravitational force in different torch positions.
Orbital welding can solve this issue by automating the process, although a welder will still be required to monitor and adjust the process.
It is more common to use orbital welding on tubing than on pipes, since tubing production creates consistent outside diameters that are better for a proper fit up in the weld head.
Orbital welding has become a standard joining method for high integrity liquid and gas systems for the semiconductor and pharmaceutical industries, requiring high purity and leak-proof integrity.
Orbital welding should be used when manual welding would be difficult or dangerous and also when large quantities of welds are required because it is fully automated and highly repeatable.
Advantages of Orbital Welding
1. Consistent Weld Bead Results.
Since the weld head moves smoothly and automatically around the pipe, there is no need to stop and restart the weld during the course of normal operation. This improves weld quality by ensuring consistent penetration and fusion.
2. Consistent Weld Quality Results.
Besides not needing to stop and restart, another significant impact on quality is the consistency of the output of the automated orbital welding equipment, which closely monitors and very precisely controls all the process parameters.
As long as the joint preparation and the base material properties are consistent, the orbital solution will precisely execute the pre programmed welding procedure which will lead to consistent results.
3. Greater Efficiency.
A weld head only needs to be set up one time per weld joint, unlike a manual weld, which requires a change in “setup” on every quadrant for each and every pass.
Variations in travel speed, weld current, arc voltage, and the feed rate of fill material are accounted for in the weld schedule entered into the machine.
Only minor adjustments to electrode angle may have to be made from pass to pass. This speeds up the welding process, and removes fatigue and discomfort as a factor that can lead to inconsistent welds.
4. Ease of Use.
Orbital welding machines require the trained operator to understand and be familiar with the machine and know how to set it up.
Manual welding, in contrast, requires the operator to be practiced in the particular welding process being used, have experience with the properties of the metals and alloys being welded, and be able to maintain efforts for ten- to 12-hour shifts.
It is much easier to obtain a consistent and reliable weld from an orbital system with a properly trained operator.
Limitations of Orbital Welding
1. Equipment Costs and Service.
The power supplies and weld heads required for an orbital welding setup aren’t common. They are built in limited numbers and often for specific purposes, and are therefore more expensive than typical manual welding setups.
Specific orbital welding equipment also isn’t available at local building and hardware stores like manual welding equipment is. If a weld head becomes damaged or a controller becomes unusable, it can be more difficult to replace or fix in a timely manner.
2. Training.
Countless welding programs and vocational schools teach manual welding processes and industry standards. However, few intensive training programs for orbital welding exist, so training on specific equipment is generally offered only by vendors in certain locations.
3. Setup Time.
Due to the precise nature of orbital welding, setup time is required. In some applications, this setup time may be more than that required for manual welding.
4. Consistent and High-Quality Joint Preparation.
On most piping welding applications, consistent weld joint preparation is required. Thus, joint preparation equipment and consumables have to be considered and included in the cost of the solution.
Application of Orbital Welding
Orbital welding is commonly used in industries where clean, precise welds are critical, such as in the manufacturing of stainless-steel tubing for pharmaceutical processes, aerospace components, and high-purity systems.
Orbital welding, with its exceptional precision, repeatability, and high-quality results, has found a home in diverse industries where critical welds are paramount. Let’s dig deeper into how this technology is transforming various sectors.
1. Aerospace Industry.
Critical Components: Orbital welding ensures the integrity of fuel lines, hydraulic systems, and other critical components in aircraft and spacecraft, where failure is not an option.
High-Purity Requirements: The process guarantees clean welds, free of contamination, essential for maintaining the safety and reliability of aerospace systems.
2. Semiconductor Manufacturing.
Clean Room Environments: Orbital welding’s ability to produce contamination-free welds makes it ideal for assembling high-purity gas and fluid delivery systems in cleanroom environments, where even the smallest impurities can compromise semiconductor production.
3. Pharmaceutical and Biotechnology.
Hygienic Welding: Orbital welding creates smooth, crevice-free welds in stainless steel piping systems, preventing the growth of bacteria and ensuring sterile conditions in pharmaceutical and biotechnological processes.
Process Piping: It’s used to weld bioreactors, fermenters, and other process piping, maintaining product purity and preventing cross-contamination.
4. Food and Beverage Processing.
Sanitary Standards: Orbital welding ensures hygienic welds in stainless steel equipment and piping used in food and beverage processing, adhering to strict sanitary standards and preventing contamination.
Dairy Industry: Widely used for welding dairy processing equipment to prevent bacterial growth and maintain product quality.
5. Power Generation.
Boiler Tubes: Orbital welding ensures the integrity of boiler tubes in power plants, where high pressure and temperature demand reliable welds.
Nuclear Power Plants: Used for welding components in nuclear reactors, where safety and leak-tightness are of utmost importance.
6. Petrochemical Industry.
Process Piping: Orbital welding is used to join pipelines carrying hazardous chemicals and gases, ensuring leak-proof joints and preventing environmental disasters.
Refineries: It’s employed for welding pipes and vessels in refineries, where high temperatures and pressures require strong and durable welds.
7. Other Industries.
- Automotive: Welding exhaust systems, fuel lines, and air conditioning components
- Medical: Manufacturing of medical devices and implants
- Oil and Gas: Welding offshore platforms and subsea pipelines
- Construction: Welding of water pipes and structural components.
Orbital welding’s versatility has allowed it to permeate various industries, ensuring the integrity of critical components and systems.
Its ability to produce high-quality welds in demanding environments has made it an indispensable tool in modern manufacturing and engineering.