Aircraft repair is a huge business! In 2018, the worldwide economic impact for global aircraft maintenance, repair, and overhaul (MRO) was over $75 billion (USD), with an estimated compounded annual growth rate of 4.7% through 2025. The commercial air travel industry’s near-term growth outlook is 6.5%, with 20-year traffic growth projected at 4.0%. Welding is a standard maintenance practice in aircraft repair as described in the FAA Advisory Circular 43.13-1B. As welding processes and procedures have improved over the years, some parts that were once non-repairable can now be repaired by welding.
TIG Welder Methods and Materials
Welding is the most prominent form of joining metals in aircraft without the use of fasteners. The five types of metals welded in aircraft are 4130 steel, stainless steel, aluminum, magnesium, and titanium, each used in different areas of the aircraft. For example, 4130 was a prevalent building material in tube-and-fabric construction but is now limited to mainly aircraft used in agricultural applications.
TIG Welding is revolutionizing aircraft maintenance for repairs that fall outside of the original equipment manufacturer’s scope. Magnesium alloy is common in constructing transmission cases in helicopters because it is very strong and light; weight is everything in aircraft (particularly helicopters). Yet transmission cases were never made to be a repairable item. The original intention was to simply scrap damaged cases and replace them. However, a new transmission case can easily cost more than $50,000. Companies specializing in aero repairs have pioneered proprietary repairs on transmission cases and gearboxes that pass the FAA’s rigorous muster. These repairs can save upward of 90% off the bill of a new case or gearbox.
The approved method for magnesium cases is predominantly tungsten inert welding (TIG) for the extreme heat necessary to join the metal. Oxyacetylene can be used for this method of joining metals but it is not the best method due to base metal oxidation, distortion, and the loss of elasticity.
Benefits of TIG Welding in Aircraft Repair
Tungsten inert welding (TIG, also known as Gas Tungsten Arc Welding) is an incredibly versatile welding method and can meet most of the demands of aircraft maintenance. Because of its relative simplicity and accessibility, oxyacetylene welding was the standard process for many, many years. Still, TIG welding has dethroned it as the go-to method in recent years, particularly as TIG equipment has become commonplace and come down in price.
Changing Technologies in TIG Welding
In the early years of TIG welding, the inert gas most commonly used was helium, which gave rise to the early trade names of Heliarc and Heliweld. In time, carbon electrodes made way for the modern tungsten rod. We now find a highly versatile technique that is further enhanced by the ability to run either alternating current or direct current.
A TIG welder set for DC current, straight polarity, is suitable for all mild steels, stainless steel, and titanium typically welded during aircraft maintenance. 4130 is a low-carbon, chromium-molybdenum alloy and is very common in the composition of aircraft structures. The signature standard alloy is used in a tubular form for aircraft fuselages that employ a truss-type of construction. In commercial aviation, agricultural application aircraft (“crop dusters”) use this construction method exclusively because it provides a strong, rigid airframe.
Low Carbon Steel
Low-carbon steel is also widely used in the industry in the production of engine mounts for piston engines. For these parts, welding is the only method of repair available to help operators avoid purchasing new replacement parts. Considering a used engine mount from an aircraft salvage yard runs in the ballpark of $1,000 for a simple Cessna 172, fixing a cracked weld whenever practical is a much more cost-efficient solution.
Historically, aviation has been a hobby for the wealthy, and this is not just talk. If you have ever wondered why airplane owners speak openly about rebuilding their engines rather than replacing them with new engines, the figures will make it clear. Consider that a brand-new four-cylinder piston engine easily runs in the $40,000–$50,000 range. That’s not a misprint. A rebuilt zero-time engine for a Cessna 172 is still more than $20,000, and these are engines without turbochargers or superchargers.
Engine cases on aircraft piston engines are also often made out of magnesium alloys, for the same reason that gearboxes and transmission cases are: excellent strength-to-weight ratio. Unlike an automobile engine, which routinely only runs around 10%–15% of maximum output, aircraft engines operate at about 75% output during the cruise. Accordingly, their crankcases are subject to high stress and are prone to cracking. Also, since the engines are often repeatedly overhauled, the cases may have several thousand hours of use as opposed to the pistons and cylinder jugs, which are replaced at overhaul intervals. A new engine crankcase is predictably quite expensive, so the option to repair a crack by welding is far less costly.
The more complex the aircraft, the higher the cost of replacement parts. Turboprop turbine engine rebuilds (Pratt & Whitney PT-6A, Honeywell TPE331, etc.) often exceed hundreds of thousands of dollars. Fixing cracks and building up casting defects and damage is a cornerstone of cost-effective repair strategies.
Other Weldable Materials Commonly Used in Aircrafts
Aircraft are exciting machines. They are flown through turbulent air at hundreds of knots, blasted with rain and wind, only to just about drop out of the sky and slam onto a hard runway. They are strong, yet they have to be light. Corrosion is a silent killer, and weight is the constant nemesis. Stainless steel and titanium are used in aircraft construction in critical areas where low weight and temperature tolerance are paramount.
Titanium is widely used in turbine engine compressors and stator blades, subject to constant high vibration, extreme heat, and foreign object debris (FOD) that routinely includes pebbles and rocks, rivet stems, screws, loose hardware, ice, and birds. It is a harsh environment where titanium components are easily damaged. TIG welding these damaged components to fill in and blend the damaged areas saves thousands of dollars and considerable time in commission spent waiting on parts. Instead, repairs can be performed often on-site, and the engine reinstalled quickly.
Stainless steel is ubiquitous on aircraft, often used in ducting and baffling throughout the aircraft, exhaust ducts or pipes, and a slew of other areas. When, for example, an exhaust duct on a turboprop crack (not uncommon), it can easily be removed and repaired, again saving a lot of money and a whole lot of time.
Aviation is one of the most heavily regulated industries in the world. The threshold of entry to new designs is so burdensome that old technology prevails. Also, old aircraft are commonplace. Many airliners, particularly cargo aircraft, are 20 to 30 years old, which takes a toll on metals prone to fatigue. Rather than replacing parts, it is fiscally advantageous to repair whenever possible, and most repairs boil down to a weld to fix the metal. Welded repairs continue to keep operators in the black and safety compliant in a transportation market where controlling costs and maintaining safety standards are essential considerations.
The construction industry is responsible for the creation of all kinds of structures with varying sizes, levels of complexity, and uses. From simple, small structures such as family homes to large, complex ones like bridges, dams, and manufacturing plants. Structural integrity and durability are the most important considerations in this industry. This is why the construction industry employs a very large quantity of metals. In the United States alone, more than 40 million tons of steel are used annually in the construction industry. The majority of this quantity is used to create structural frameworks. This is where welding plays an indispensable role in construction.
Welding technologies are widely used in the construction industry, mainly for the fabrication of structurally sound metal frameworks by fusing various metals components. It is also used to create and maintain non-structural components. Some of the welding used for construction is pre-fabricated in a shop environment while other parts of the welding process are done on-site.
Applications of Welding in Construction
Construction comprises numerous industries, including transportation, oil, andgas, telecommunication, power, manufacturing, many others. The construction industry is very broad & diverse and is divided into three major sectors which differ by the type of structures they create. These sectors are Building, Infrastructure, and Industrial.
The application of welding is crucial to all three sectors.
As the name suggests, the building construction sector involves the creation of structures in which people can dwell and carry out their activities. This sector is further divided into residential and non-residential. Building construction mainly employs welding in the creation of structural frameworks from metal components. Welding is used for connecting steel I-beams, trusses, columns, and footers, to support the walls, roof, and floors of a building. These components are cut to shape and size, lifted into position, and welded together.
Structural welding is not employed as extensively in small buildings, as it is in high-rise buildings that require thousands of metal joints. Welding in building construction is also used for the fabrication of non-structural building components such as firewalls, stairs, handrails, and floor joists. Furthermore, welders work with other professionals in setting up various systems in a building. These include:
Electrical systems – creating electrical conduits Construction for laying wires.
Plumbing systems – installing water supply and wastewater drainage pipes.
Ventilation systems – installation of vents and ventilation pipes.
Fuel systems – installation of gas supply pipes.
This sector is responsible for the creation of infrastructures such as bridges, dams, railways, stadia, water supply systems, highways, and wastewater management systems. The application of welding in infrastructure construction is mainly structural. This is because most of the structures created in this sector are megastructures that completely depend on structural reliable metal frameworks created via welding. Certain infrastructure such as bridges can be made almost entirely of metal. Others such as dams and water systems require a lot of pipe welding.
Industrial construction covers all structures that are utilized industrially. Structures created by this sector hardly stand alone but are usually part of a large system of numerous components and structures that work together for specific purposes. Such systems include manufacturing plants, refineries, mills, power generation stations, and many more. Industrial construction is considered the most diverse sector within the field as it cuts across numerous industries. The applications of welding in this sector are as diverse as the sector itself. TIG welders are used for the fabrication and maintenance of structural frameworks, pipelines, industrial equipment, and support structures for large components.
Welding Technologies Employed in the Construction Industry
The construction industry has a wide range of welding needs. Most existing welding technologies have one use or the other in the industry. Some of these and their uses are as follows:
SMAW: Also known as arc welding, submerged metal arc welding (SMAW) is mainly used for welding steel structures.
FCAW: Flux-cored arc welding is considered more convenient than its submerged arc counterpart. This technology is widely employed in fabrication using structural steel as well as heavy equipment repair
GTAW: Gas tungsten arc welding (GTAW), also known as TIG welding, is crucial for its compatibility with various metals including stainless steel, aluminum, bronze, and copper.
GMAW: Gas metal arc welding (GMAW), popularly known as MIG welding, is employed for both structural and non-structural purposes.
Application-specific welding systems employed in the construction industry include stud welders such as ProWeld Arc and pipe welders such as the PipeWorx welding system.
Benefits of Welding in the Construction Industry
The importance of structural integrity and durability in construction can hardly be overemphasized as structural failure can lead to a devastating loss of life and resources. Structures created weigh thousands of tons and are expected to last for hundreds of years. With the high strength and durability of weld joints, stakeholders in construction can rest assured that there’s nothing to worry about from the point of the framework.
Productivity is crucial to saving costs, resources, and time on any construction project. Productivity in a project is dependent on the efficiency of the processes involved. In terms of advancing construction efficiency, welding is at the forefront. While welding itself is a highly efficient process when using the right equipment, several other technologies have been incorporated into the process to make it even more efficient. Some of the technologies used in welding that are particularly beneficial to the construction industry are as follows:
This technology saves builders thousands of dollars and increases speed and productivity by eliminating the need for a welder to move to and from a power source to make necessary adjustments during welding. This is particularly helpful in high altitude welding where the actual welding may be 100s of meters above the ground where the power source is located. Some of the solutions that make up ArcReach include Cable Length Compensation (CLC™) which automatically adjusts the delivered voltage based on the cable length to ensure that the set voltage is always supplied; and Adjust While Welding (AWW™), which allows the operator to remotely adjust weld settings right from where they are working.
Weld Automation Equipment
Types of automation equipment that increase efficiency and accuracy include automatic wire feeders, welding manipulators, turning rolls, and welding positioners which are used to hold and rotate the pipe or other weldment.
Multiprocess TIG Welders
Some welding projects require more than one welding technology at a spot. It is stressful enough to switch equipment not to imagine doing this at heights where you would need to ascend and descend repeatedly. Multi-process welders eliminate this problem by combining various welding technologies into a single compact unit. In addition to all these, another factor that boosts productivity is the portability of welding equipment. This is appreciated when work has to be carried out over rugged terrain, at height, or in relatively small spaces.
The construction industry has a wide range of fabrication requirements. One of the numerous reasons why welding is indispensable in construction is its flexibility. For any size, work environment, or material, there is a suitable welding technique. For example, 5 cm diameter pipes can be welded as good as 50 m long beams and columns. Also, the various metal grades used in construction are all compatible with one welding technology or another.
Compared to many other manufacturing processes, welding is relatively cost-effective. To save even more, contractors and other industry stakeholders can simply rent high-quality TIG welders equipment, saving thousands of dollars on capital spending. If you are considering long-term continuous use, leasing your welding equipment might be an option to consider. Speak to one of our sales associates to learn more about our leasing programs and national accounts.
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