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Frequently asked questions

clientQuestion:
What is orbital GTAW fusion tube welding?

 

Answer: It is a process whereby two tubes, or a tube and a fitting, or two fittings, are clamped in place within a chamber of a mechanism commonly referred to as a "weld head". The tungsten electrode is mounted in a U-shaped rotor, which can be driven around the tube. Once the arc is initiated, the electrode proceeds to rotate around the weld joint, fusing the two ends together. Optional wire feed, for weld joint reinforcement, is available with certain model weld heads. The arc welding current and electrode rotation speed is regulated by a power source/control system, thus automating the entire process. The end result is a clean, repeatable and consistent quality weld.


clientQuestion:
What is orbital GTAW pipe welding?

 

Answer: A system for multipass GTAW welding of pipe rotates the torch around the fixed pipe, and has the capability of manipulating the torch in a similar fashion to a manual welder. Motorized drives mounted on the rotation device automatically maintain a desired arc length, and an oscillation mechanism provides a weaving motion, where the width, speed, and point dwell time of the weave stroke are programmable. A wire feeder and spool mount are located on the Head. A programmable controller/power source integrates weld head operation with control of weld power output.

Magnatech's Pipemaster systems are usually programmed by position, and a 5-pass weld can be made without stopping.


clientQuestion:
Can I use mechanized FCAW on materials other than carbon steel?

 

Answer: Mechanized FCAW is used on a wide variety of materials. The only limitation is whether an all-position filler wire is available to match the base metal of the pipe. FCAW consumables are available to meet most requirements.


clientQuestion:
How difficult is it to learn to program a weld?

 

Answer: All Magnatech GTAW power sources are equipped with Auto Program. The welder enters tube/pipe OD, wall thickness, material and head model used. A program is automatically generated.


Magnatech is the only manufacturer to provide this convenient capability for multipass welds.


clientQuestion:
What is the range of pipe sizes on which Magnatech's Pipeliner can be used?

Answer: "Guide Rings" are available for 168mm (6") pipe and larger. The Head mounts on these Guide Rings. These hinge open and are clamped around the pipe in less than a minute. Above 1829mm (72") OD, Guide Rings are still available, but Flx-Track is more commonly used. This flat flexible track is available in standard 2.3m (7.5') sections which bolt together for longer lengths. Magnet and vacuum attachment allows both ID and OD welding.


clientQuestion:
What tube end preparation is required to generate quality orbital tube welds?

Answer: Good, "square" tube ends are required for orbital welding. Tube ends can be prepared via the use of field portable, OD mounted, tube end preparation tools. Both ID and OD of the tubing should be burr free, without chamfer. When two tubes or a tube to fitting are butted together for orbital welding, two of the main considerations are mismatch and gaps. Some general rules include:

  • Preferably, no gap between the tubes or fittings is optimum. If there is gap, it should be less than 5% of the wall thickness.
  • Wall thickness variation at the weld zone should be no more than +/- 5% of the nominal wall thickness.
  • High-Low mismatch should be minimized by using stands or external clamps to align the two tubes to be welded. Tack welding may be required for larger OD's.

clientQuestion:
What type of shielding gas is recommended or required to generate quality, orbital tube welds?

 

Answer: An inert gas is required on the tube OD and ID (if welding stainless steel and other nickel based alloys) during welding to prevent the molten material from oxidizing in the ambient atmosphere. The objective is to create a weld that has zero oxidization color - "tint" on the weld ID, and minimal tint in the weld bead OD and the Heat Affected Zone (HAZ).

Argon is the most commonly used shield gas (for the OD of the tube) and the purge gas (for the ID of the tube). Mixed gases, such as Argon with from 2-10% Hydrogen added, increase penetration capability, while reducing heat input. 75% Helium/25% Argon is often used when the wall thickness to be welded is heavy, 2.5mm (0.1") and greater and for welding copper alloys. Hydrogen gas mixtures are incompatible with carbon steels and certain alloys, due to possible hydrogen embrittlement of the resultant weld. Gas purity is dictated by the application. For high purity situations where the concern for micro-contamination is paramount, such as semiconductor and pharmaceutical applications, the shield and purge gases must minimize the heat tint that could otherwise be undesirable. In these applications, ultra high purity gas or gases with a local purifier are employed. For non-critical applications, high purity or commercial grade argon gas may be used.


clientQuestion:
What type of tungsten can and should I use with Magnatech orbital, tube welding equipment?

Answer: The tungsten electrode, the source of the welding arc, is one of the most important elements of the welding system. Repeatable weld quality is directly related to the quality of the tungsten chosen for the orbital welding process. The objective of the choice of a good tungsten it to balance the benefits of a clean arc start, reduced arc wander, with good weld penetration and extended electrode life.

Magnatech recommends the use of 2% ceriated tungsten with its complete line of GTAW weld heads. Ceriated electrodes offer an advance in electrode safety and improved arc starting ability.


client

Question:
What range of tube OD sizes and wall thicknesses can Magnatech orbital, closed arc, tube welding systems weld?

 

Answer: With our five (5), different model tube weld heads, Magnatech 800 series of heads can weld from 3mm (.125") OD to 150mm (6") OD tubing. As a general rule, wall thicknesses up to 3mm (.125") can be welded using a fusion GTAW process.


clientQuestion:
What pipe end preparation do I need for GTAW pipe welding?

Answer: A "J" bevel is commonly used, with the pipe ends butt tightly together. This bevel can be quickly machined on pipe ends using readily available portable pipe beveling machines. A precise bevel and good fit-up guarantees repeatable code welds.


client

Question:
Can code-quality mechanized FCAW welds be made with the pipe in a fixed position?

Answer: Advances in inverter power supply technology and consumables have made FCAW a reliable and increasingly common method for making x-ray-quality welds.


client

Question:
Is mechanized FCAW welding faster than manual SMAW (stick) welding?

Answer: A conservative estimate is that mechanized FCAW is 5X faster than manual stick electrode welding, with higher productivity seen by some customers. The deposition rate for SMAW welding is only 0.5kg/hour (1 lb/hr). This results from the 15-20% "arc on" time of a manual welder and the need to carefully grind each pass to remove slag. The Pipeliner can conservatively deposit 2.5kg/hr (5.5 lb/hr) FCAW consumables today are "self-slagging" – the slag falls off the weld as it cools, and a simple wire brushing is all that is needed between passes.


client

Question:
What is the pipe size capability of Magnatech's GTAW welding systems?

Answer: "Guide Rings" are available for 48mm (1-1/2") pipe and larger. The D and T Head models mount on these Guide Rings. For smaller pipes, inserts can be used to practically weld down to 27mm (3/4") pipe. These hinge open and are clamped around the pipe in less than a minute. Above 1829mm (72") OD, Guide Rings are still available, but Flx-Track is more commonly used. This flat flexible track is available in standard 2.3m (7.5') sections which bolt together for longer lengths. Magnet and vacuum attachment allows both ID and OD welding. The two Quickclamp models cover the size range of 25 – 168mm (1" – 6.625"). These directly attach to the pipe with an adjustable clamp.


client

Question:
What is mechanized FCAW welding?

 

Answer: A system for GMAW or FCAW welding of pipe rotates the torch around the fixed pipe, and has the capability of manipulating the torch in a similar fashion to a manual welder. Motorized drives mounted on the rotation device control contact tip to weld puddle distance, and an oscillation mechanism provides a weaving motion, where the width, speed, and point dwell time of the weave stroke are programmable. A wire feeder and spool mount may be located on the Head, on the floor, or consist of a push-pull system with a floor-mounted feeder and a pull feeder mounted on the Head. A programmable controller/power source integrates weld head operation with control of weld power output.

"Orbital" welding is a misleading terms when it comes to FCAW of pipe. Mechanized pipe welding is always done double-up, just as in manual welding. The only time that welding is done in a 360 degree uninterrupted fashion is when the pipe is vertical (2G).


clientQuestion:
What pipe end preparation do I need with mechanized FCAW?

Answer: A a standard 30 or 37.5 degree bevel can be used.