Automating automatic orbital welding

Finding skilled welders is becoming difficult and will only become more difficult in the near future. According to the Welding Technology Institute of Australia, "the need for professionally qualified welding personnel has been widely recognised on a global basis."

One means of addressing the shortage is through automated systems, which produce more work with fewer people. Since its introduction to the aerospace industry in the 1960s, automatic orbital Gas Tungsten Arc Welding (GTAW) has gained favour in a variety of industries in which maximum leak integrity, high performance, or ultra-cleanliness are of paramount importance.

Automatic orbital welding provides enhanced precision and reliability compared to manual techniques. Small, portable inverter power supplies, advanced control systems and other advancements have made orbital welding systems practical for a range of applications.

The advent of new technology has led to further improvements in these systems. Power supplies designed with open platforms provide welders of various skill levels with even more welding options and an ease of use not previously available. Enhanced programs and controls help improve the consistency and reliability of welds as well as operator efficiencies. This article will review several of these advancements.

Orbital welding power supplies have been incorporating more skills of the welder into the welding system itself, enabling efficiencies in automation, programming, and documentation. To achieve these efficiencies, a power supply must be designed with an open platform that allows an interface with standard devices and the ability to expand as technology evolves. The result is a welding system that meets the expanding needs of various industries.

Maintaining proper shielding gas control at the weld head is critical to protecting the weld from atmospheric contamination. Newer orbital welder designs feature automatic shield gas control in the weld head.

Automation

Aspects of the welding process that historically would be undertaken manually, such as travel speed, arc gap, current control, and gas flow are controlled through electronic and mechanical means. This minimises many of the variables in the welding process that can lead to errors or defects and enables welders to focus most of their attention on overseeing the process and completing actual welds.

Programming

Every orbital weld – regardless of the application – requires the creation of a program, which controls the output characteristics of the system. User-friendly systems simplify programming by providing step-by-step procedures to create programs for a variety of tube diameters, wall thicknesses and base materials. Rather than build programs manually using charts or tables, assessing past weld parameter data, or relying on memory, the operator can create a program by selecting pertinent data from "pick lists" or dropdown menus.

The system then creates the initial program for the operation, which can significantly reduce the chance for human error and reduce start-up time. This is also very helpful when welding materials that are unfamiliar to the user. If additional assistance is needed, a quality orbital welder supplier will also offer assistance in developing welding programs.

Newer orbital welding systems offer numerous preset programs and enhanced user interfaces for programming ease. Models are available with integral USB ports that enable operators to plug in a keyboard, mouse, and/or a number keypad for easier data entry. Operators may also download welding programs via a USB flash drive or update operating system software to add features or functionality. Durable, integrated colour touchscreens also help with programming ease.

Documentation

Traditionally, the documentation process is costly and time consuming. Today’s orbital welding technology enables data to be stored within the system for retrieval and transfer to databases for analysis and reporting. High-speed thermal printers built into newer orbital welders also help with documentation.

The automated orbital welding process aids in achieving weld repeatability and consistency over extended periods of time. With manual welding human fatigue can become a factor.

Although the operator may be highly skilled and experienced, he may produce inconsistent results because he literally is completing each weld by hand.

With orbital welding, the electrode is accurately rotated in an orbit around a joint on a rotor. The rotor and electrode are housed in the weld head, which rotates around the tube.

The process is highly controlled, ensuring high-quality welds that can be produced on a consistent and repeatable basis.

Orbital welding systems perform a set of operations in a controlled manner where variables are maintained at preset levels.

The system automatically starts and completes the weld, stepping from one variable setting to the next at a specific location along the joint or at a predetermined time during the process.

Gas Control

Automated orbital welding generally uses the GTAW process, which operates by establishing an arc between a nonconsumable tungsten electrode and the base material that is being welded, creating a weld puddle. The electrode is positioned in the weld head.

The electrode and weld puddle are both surrounded by a shielding gas, which is fed through the weld head to protect the electrode, molten weld puddle, and solidifying weld metal from atmospheric contamination. The heat produced by the arc melts the base material. The electrode moves along the joint and progressively melts and joins the adjoining surfaces. Newer orbital power supply designs feature automatic shield gas control to the weld head.

Systems with automatic shield gas control eliminate this inefficiency or the possibility of negatively affecting the weld quality due to an incorrect setting.

Blast Purge

Further gas control advancements enable operators to improve their efficiency when welding at locations where long distances exist between the power supply and weld head. A sufficient gas volume must be present at the weld location before starting a weld. Newer welding systems utilise a blast purge feature to rapidly fill the lines and then automatically return gas flow to normal levels, allowing operators to start a weld sooner.

Power considerations are key

When choosing an orbital welding power supply, operators should look for systems that enable them to perform welds for a wide range of applications. They should also look for systems that limit electrical interference.

Higher Amp Outputs

Power supplies with higher power outputs are capable of welding larger diameter and heavier walled tubing and/or piping while maintaining consistent welds. Newer welding systems offer the power output needed to weld the heavier walled components found in general industrial applications like oil and gas while still having the ability to weld smaller diameter thin walled tubing for R&D or semiconductor applications.

Electromagnetic Interference

Initialising the welding process requires a high-frequency, high-voltage arc start, which could result in electromagnetic interference (EMI).

Frequent EMI resulting from a welding project could prove to be a nuisance or worse in the case of computers shutting down and causing work to be lost. Technology in arc starting has improved, and welding systems with low EMI arc start technology allow the arc start to occur without affecting the operation of equipment in close proximity.

Small, lightweight orbital welding systems are a practical option. Remote controls and detachable weld heads and fixtures allow joints to be pre-positioned and enable orbital welding to be conducted in hard-to-reach places.

[John Glessman is manager, welding system products, for Swagelok Company.]