By definition, orbital welding is a kind of highly specialized welding method where the welding head rotates 360-degrees around the weld pieces. It’s primarily used for joining rounded metal parts such as tubes and pipes that need a consistent, contaminant-free weld.
The process can be extremely difficult to materialize manually. Therefore, orbital welding is almost always done using a semi or fully automatic orbital welding machine. These high-end machines boasting a flawless mechanism result in high-purity, rock-solid, corrosion-resistant weld joints.
Next up, let’s talk in detail about the different variations of orbital welding used for different sets of applications.
- Types of Orbital Welding: An Overview
- Applications of Orbital Welding
Types of Orbital Welding: An Overview
Fundamentally, orbital welding is a technique of moving the arc around the workpieces in 360 degrees. However, there are slight variations, depending on the kind of material and specific results you are looking to achieve.
Automatic Orbital Welding
Orbital welding using the automatic Gas Tungsten Arc Welding (GTAW) technique is the most common method for joining thin metal tubings and piping systems.
The process requires the use of:
- Non-consumable tungsten electrodes.
- Inert gas.
- Enclosed orbital tube to tube sheet welding head.
- Thorium-Tungsten is the most preferred electrode for this type of welding for its excellent current density that helps to reduce weld contamination.
Remember that the primary goal of orbital welding is to produce high purity, ultra-strong welds. The inclusion of tungsten in the filler wire is very helpful in controlling the temperature of the electrode, which consequently helps to minimize air contamination.
On the downside, the welder cannot alter welding variables such as travel speed, oscillation, heat input, welding direction, and angle once the machine begins to weld.
Semi-automatic Orbital Welding
Both flux-cored electrodes and bare electrodes are used as consumable electrodes for welding unprocessed weld pieces, thick-walled pipe, and fittings.
In this case, you will be required to mount a three-axis wire feeder to the welding head to control wire placement. The biggest advantage of orbital welding with consumable electrodes is that this process is semi-automated, meaning the welder can alter certain variables during the welding process.
If you are dealing with host materials that aren’t processed with special material composition for orbital welding, you will be able to create stronger bonds with this semi-automated orbital welding.
Equipment Required for Orbital Welding
Owing to the large-scale industrial applications of orbital welding, you will need access to high-tech equipment to maintain high welding standards. General orbital welding equipment include:
- A programmable power source with 4-6 axes of settings including weld head travel speed, current pulse rate, wire feed options, AVC, and oscillation.
- A welding head that can hold the filler material in place, maintain consistent welding temperature and current flow.
- A wire feeder system that can be either mounted onto the weld head or be used as an external device.
- A coolant system to protect the equipment and host materials from overheating.
Types of Gases Required for Orbital Welding
Shielding gases are an essential requirement for orbital TIG welding. It not only protects the weld pool from atmospheric contamination but also helps to maintain arc quality.
99.995% pure argon (purity of 4.5) is the most widely used inert gas for the process. However, for thin and delicate metals like titanium, titanium alloys, and zirconium, the argon gas should have a purity of 4.8 for best results.
For welding thicker tubing systems and sanitary pipe fittings that are used in semiconductors and medicine manufacturing units, we usually add 2% to 5% hydrogen to argon.
Now, hydrogen is a reductive gas. The main purpose of adding it to argon is to crank up the weld energy for deeper penetration of metals thicker than 0.1 inches.
Helium has a great heat conductor, which is why it is mixed with argon when the welder needs a tremendous amount of weld energy. Being lighter than argon also gives it the added advantage of a broader coverage.
75% helium and 25% argon is a common shielding gas mix for metals with high thermal conductivity e.g aluminum, copper, tungsten, graphite, and zinc. Gas mixture with 50-70% helium is ideal for welding tungsten.
For duplex and super duplex steel, you can use an argon-based shielding gas mixture with a small percentage of carbon dioxide or oxygen for enhanced arc stabilization.
Alternatively, mixing 30% helium, 2% carbon dioxide to an argon-based mixture can greatly improve the weld speed and fluidity of the weld pool, leading to deeper penetration.
Backing Gas for Orbital Welding
Purging the inner surface of the tubes and pipes with a backing gas is an important step in UHP (Ultra High Purity) welding. Purging removes all the oxygen from the surface which helps to prevent oxidation of welds.
5.0 argon or 100% pure argon is the most commonly used gas for purging. Depending on the welding conditions, we can also add a small percentage of hydrogen and nitrogen to ensure protection against oxidation.
Applications of Orbital Welding
Orbital welding is most useful for tube to tube, tube to tubesheet, and pipe to pipe joining.
It’s ideal for producing welds that require a combination of high purity and excellent strength.
By definition, high purity welds are tube systems and fittings with less than 10 PPM (parts per million) of oxygen, carbon, and hydrogen.
The purpose of high purity welding is to prevent contaminants from entering the weld area. That’s why the process is exclusively performed in a closed clean room and a precisely controlled environment.
The scope of orbital welding is huge. It’s a staple welding method in industries that demand the highest purity welds. Examples would be medical and semiconductor industries.
The purpose of orbital welding in a clean room setting is simple. It prevents impurities from contaminating the contents inside the tubing systems. Orbital welding is a staple in the following industries:
Pharmaceutical and Biotechnology Industry
In these industries, orbital TIG welding is used for connecting steam lines to supply panels. Purging the weld pieces with 5.0 purity argon gas drastically improves corrosion resistance of the tubing metals.
The main purpose of welding in a controlled environment is to maintain superior hygiene of the fluid delivery systems in the bio-pharma industry.
Orbital welding yields sturdy, crevice-free welds that effectively control the growth of harmful microorganisms inside the tubings.
Food and Beverage Industry
Food and beverage manufacturers have to meet government-mandated strict hygiene and safety standards. Preventing the growth of germs and bacteria inside the supply lines and containers is the one of the most critical aspects of food processing.
The use of pure gas for purging the systems reduces oxidation of the piping lines which ensures adequate safety and sanitation of the manufactured items.
Other industries where orbital welding is applied for the aforementioned reasons include:
- Thermal power station.
- Nuclear power plant.
- Chemical manufacturing industry.
- Aerospace engineering.
Benefits of Orbital Welding
The advantages of orbital welding are plenty. For instance-
It Improves Productivity
Manual welding is a tedious process that requires superior skills. With top-of-the-line orbital welding machines, professional welders and metal fabricators can repeatedly apply the same weld sequences on bulk material to achieve consistently good results.
The only manual effort required here is operating the machine properly. The welder might also have to occasionally adjust the filler material angle.
Since there is no need for complex assembly work or changing the parameters in every few passes, orbital welding can significantly increase productivity and reduce errors.
It Ensures Better Workplace Safety
Minimal human assistance means minimal risk of welding-related injuries such as flash burn and immense eye pain caused by prolonged exposure to ultraviolet rays and infrared radiation.
On-field welding in difficult environmental conditions can be extremely risky. It can affect both the welder and the quality of welds. By automating the entire process, welders can ensure proper quality control by operating from a safe distance.
Preparing the base metal and positioning the weld head is a one-time thing. After that, you can precisely control all the welding parameters such as travel speed, heat input, and arc strength remotely.
Modern orbital welding machines also provide video transmission to help you closely monitor the process.
It Produces High Precision Welds
Since it’s an automatic process, the chance of weld defects is next to nothing. Orbital welding with the right kind of equipment, material, and settings can consistently yield smooth, crevice-free, sound welds.
It Helps with Strict Quality Control
One of the biggest advantages of automatic orbital welding is that you can repeat the same welding cycle as many times as needed to obtain desired results.
High-end orbital welding machines have state-of-the-art data acquisition system. It automatically transmits welding data to quality management systems for accurate tracking and controlling of the welding parameters.
Disadvantages of Orbital Welding
Despite being one of the most mechanically and technically superior welding methods of all time, orbital welding too is guilty of having certain limitations, such as:
- High cost of equipment.
- Requires the welders to go through rigorous training to learn how to operate the equipment and gauge the welding parameters accurately.
- Due to the involvement of a plethora of equipment, the setup time can be huge.
- The application of orbital welding is limited to very specific kinds of objects such as 316L stainless steel tubing and ⅛” pipe fittings.
Orbital welding has been a real gamer changer for several industries. Its ability to produce high-purity welds in bulk is unmatched to date. No wonder it is a staple in the medical, automotive, aerospace industry.
Although orbital welding is primarily done using hot and cold wire TIG welding. The technology is rapidly developing to include MIG and flux-cored arc welding techniques to expand its applications.
This article was aimed to provide you with a working knowledge of orbital welding. If you are considering orbital welding as a potential career option, I sincerely hope I was able to deliver the insights you needed to get started.