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Weld Purge Monitors for TIG and MIG Welding

weld purge monitor

 

A weld purge monitor verifies no oxygen during argon back purge for TIG welding or argon CO2 blend for MIG welding.

Why is Weld Purging Important?

Weld purging removes oxygen, water vapor and any other gases that might be harmful to a welding joint as it is being welded. The oxygen, water vapor or other gases are replaced with inert purge gases like argon or carbon dioxide from a welding joint as it is being welded. Stainless steel, titanium, nickel and zirconium alloys are sensitive to the presence oxygen and water vapor and will combine with the hot metal as it is being joined. This results in a sub-standard weld.

Weld Purging

During welding, inert argon or CO2 gas flows from a tank to the tip of the welding rod. This shielding gas is concentrated in a small cup that surrounds the tip of the rod. Because of the gas pressure from the tank, no oxygen is present at the welding tip.

Purging is the process used to surround the backside of the weld inside the pipe with the same inert gas. Welders use inflatable plugs, stoppers or purge dams to seal both ends of the pipe, then fill the pipe with the shield gas. This displaces the oxygen inside the pipe. While it is common to turn on the gas and “wait a while” before welding, best practices are to verify the shield gas has completely displaced the oxygen before starting the weld.

Verified back purging of welds is critical to insure there are no leaks or weak points in the weld. In cases like welding in nuclear plants, submarines or when welding food-grade pipes, weld purge gas levels must be verified and recorded as part of the welding quality control process.

See examples of proper and improper weld purging.

Weld purging is most often used in Metal Inert Gas (MIG) welding and Tungsten Inert Gas (TIG) welding, also known as Gas Tungsten Arc welding (GTAW).

While both MIG and TIG welding use an electric arc to create the weld, MIG is more common because it can be used on steel, stainless steel and aluminum of almost any thickness. TIG welding can be used on more kinds of metals or can be used to weld 2 dissimilar metals. However, both MIG and TIG depend on shield gases to create good welds.

Weld Purging Benefits

  • Saves time. No need to rely on a rough estimation of time to purge pipe. Welding can begin the moment purging is complete.
  • Saves money. Verifying when purging is complete reduces purge gas consumption to only the amount needed.
  • Saves product. Welding is never started before purging is complete. This reduces scrap by producing a top-quality weld every time.

TIG Argon Gas Weld Purge Monitor

argon weld purge monitor

To verify there is no oxygen at the weld point the TecPen Weld Purge Monitor provides accurate measurements down to 0% oxygen for back purging of argon during welding.

As a trace oxygen analyzer, the TecPen Weld Purge Monitor is most commonly used to verify argon flooding during welding of stainless steel or titanium pipe in the aerospace, automotive, nuclear, medical and food-grade industries where x-ray verification of welds is required or the backside of welds cannot be inspected. 

The TecPen features measurements in less than three seconds to ensure you can get measurements while working quickly, which is imperative in TIG welding. The large display is easy to read during the welding process, and the TecWeld comes pre-calibrated from the factory. As an added benefit, the TecPen records oxygen levels in its build-in memory which is important when needing to form a paper trail for inspection or verification.

The TecPen Weld Purge Monitor also features a built-in 10,000-hour gas sampling micro-pump and is an ideal choice for TIG welding of stainless steel or titanium.

MIG Argon Carbon Dioxide Weld Purge Monitor

oxygen co2 weld purge monitor

The TecPen Oxygen and CO2 Weld Purge Monitor combines all the features of the TecPen Weld purge monitor with a carbon dioxide sensor for MIG welding. It provides accurate measurements down to 0% oxygen and up to 100% carbon dioxide when back purging with an argon and CO2 gas mix during welding. It is most commonly used for verifying C25 or C100 shielding gas during MIG welding.

Like the TecPen Oxygen Weld Purge Monitor, this monitor uses needle purge testing of oxygen and carbon dioxide levels in the back purge gas. In the case of C100 shielding gas, the TecPen can verify up to 100% CO2 levels before welding. If C25 shielding gas is used, the TecPen can also verify 0% oxygen and 25% CO2 if a C25 combination Argon and CO2 shielding gas is used.

Inside the TecPen, a micro pump continuously samples oxygen and carbon dioxide until the optimum gas level is achieved. Then welding can begin. Pressing the Save Data button records the O2 and CO2 levels to the TecPen’s built-in memory. The logged data can later be downloaded to a PC as a spreadsheet for inspection and quality control documentation.

Learn more about TIG, MIG welding and weld purge monitors.


References:

https://www.thebalance.com/what-is-the-definition-of-oxidized-metal-2340018

https://www.polymersolutions.com/blog/why-do-weld-joints-fail/

https://www.praxairdirect.com/Industrial-Gas-and-Welding-Information-Center/Welding-Tips-Tricks-and-Information/TIG-Welding.html

https://www.americantorchtip.com/blog/tig-vs-mig


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