Orbital welding is Automatic Tunguston inert gas welding. It eliminates chances of manual errors in welding. It produces identical welds for hundred of times hence accuracy in welding. Orbital welding was first used in
1960's when aerospace industry recognized need for a superior joining technique for aerospace hydraulic lines. A mechanism was developed in which arc from a tungsten electrode was rotated around tubing weld joint. The arc welding current was regulated with a control system thus automating entire process. The result was a more precision and reliable method than manual welding method it replaced. Orbital welding became practical for many industries in early 1980's when combination power supply / control systems were developed that operated from 110 V AC and were physically small enough to be carried from place to place on a construction site for multiple in-place welds. Modern day orbital welding systems offer computer control where welding parameters for a variety of applications can be stored in memory and called up when needed for a specific application. The skills of a certified welder are thus built into welding system, producing enormous numbers of identical welds and leaving significantly less room for error or defects.
Orbital Welding Equipment
In orbital welding process, tubes / pipes are clamped in place and an orbital weld head rotates an electrode and electric arc around weld joint to make required weld. An orbital welding system consists of a power supply and an orbital weld head.
Power Supply: The power supply / control system supplies and controls welding parameters according to specific weld program created or recalled from memory. The power supply provides control parameters, arc welding current, power to drive motor in weld head and switches shield gas (es) on / off as necessary.
Weld Head: Orbital weld heads are normally of enclosed type and provide an inert atmosphere chamber that surrounds weld joint. Standard enclosed orbital weld heads are practical in welding tube sizes from 1/16 inch (1.6mm) to 6 inches (152mm) with wall thickness' of up to 0.154 inches (3.9mm) Larger diameters and wall thickness' can be accommodated with open style weld heads.
The Physics of GTAW Process
The orbital welding process uses Gas Tungsten Arc Welding process (GTAW) as source of electric arc that melts base material and forms weld. In GTAW process (also referred to as Tungsten Inert Gas process - TIG) an electric arc is established between a Tungsten electrode and part to be welded. To start arc, an RF or high voltage signal (usually 3.5 to 7 KV) is used to break down (ionize) insulating properties of shield gas and make it electrically conductive in order to pass through a tiny amount of current. A capacitor dumps current into this electrical path, which reduces arc voltage to a level where power supply can then supply current for arc. The power supply responds to demand and provides weld current to keep arc established. The metal to be welded is melted by intense heat of arc and fuses together.
Reasons for Using Orbital Welding Equipment
There are many reasons for using orbital welding equipment. The ability to make high quality, consistent welds repeatedly at a speed close to maximum weld speed offer many benefits to user:
Productivity. An orbital welding system will drastically outperform manual welders, many times paying for cost of orbital equipment in a single job.
Quality. The quality of a weld created by an orbital welding system with correct weld program will be superior to that of manual welding. In applications such as semiconductor or pharmaceutical tube welding, orbital welding is only means to reach weld quality requirements.
Consistency. Once a weld program has been established an orbital welding system can repeatedly perform same weld hundreds of times, eliminating normal variability, inconsistencies, errors and defects of manual welding.
