Best Oxygen Analyzers for Welding (Expert Analysis)

Oxygen Analyzer, Oxygen Purge Monitor, Weld Purge Monitor, Welding Analyzer -

Best Oxygen Analyzers for Welding (Expert Analysis)

Oxygen (O2) analyzers are used to confirm an inert environment for the best welding results. These detectors continuously operate to confirm low levels (less than 100 ppm) of oxygen. O2 analyzers typically include a probe, pump, oxygen sensor, and display. Oxygen analyzers for welding have reduced in price over the past few years, now retailing for less than $500.

Pros

Cons

  • O2 analyzer prices have dropped as low as $500.
  • Reducing oxygen improves weld joints.
  • Simple, fast, and small units.
  • Oxygen becomes dangerous to life when displaced to less than 19.5%. Care must always be taken to prevent low levels of O2.
  • Oxygen analyzers can get very expensive.
  • Electrochemical oxygen sensors have a limited life from 2 to 3 years.

Why Is Reduced Oxygen So Important for Welding?

While welding, the objective is to remove as much oxygen as possible. The best welding results occur when there is no oxidation, hence the need for minimal oxygen levels. Since O2 naturally exists in the air at 20.9%, it is difficult to eliminate oxygen in small spaces. 

Weld oxidation degrades the mechanical properties of a pipe and reduces its resistance to corrosion. To reduce this oxidation, the oxygen content must be dramatically lowered.

For welding, inert gases are used to displace and remove the oxygen. This is where confidence in accurate O2 detection is important. An oxygen analyzer for welding does exactly that. It reliably confirms the exact oxygen level while welding. 

Benefits of Using an Oxygen Purge Analyzer?

The most important benefit of using an oxygen purge analyzer is to ensure that O2 levels remain low. This reduces oxidation and oxide thickness while welding.

Many academic studies show the relationship of welding oxygen content and resulting oxide thickness (oxidation). For example:

  • One study shows an oxide thickness of about 0.7 μm with oxygen at 30 ppm compared to about 1.5 μm with oxygen at 280 ppm.
  • Oxidation was responsible for the cracked specimens welded under high oxygen content.
  • This results in decreasing corrosion resistance of the welding samples.

These studies show the importance of sensitive oxygen detection down to 100 ppm while welding.

The image below visually shows the correlation between oxygen content and oxidization. The darker the weld, the more oxidization. See more here.

purge monitor oxygen

Other benefits of using a portable trace oxygen analyzer include:
    • Reduced time as there is no need to depend on time for purge estimates.
    • Reduced gas consumption when purging. It is also easier to control the amount required.
    • Ensured quality as welding can begin when oxygen depletion is complete, so no need to worry about welding too early.

What Does an Oxygen Analyzer for Welding Do?

Oxygen analyzers are sometimes called:

    1. Inert shielding gas monitors
    2. Weld purge monitors
    3. Oxygen analyzers for welding
    4. Trace oxygen analyzers
    5. Oxygen purge monitors

They all refer to measuring instruments that detect oxygen and provide a quantitative measurement of the O2 levels for welding applications.

An oxygen analyzer tracks the O2 concentration and displays results in % or parts per million (ppm).

For welding, O2 analyzers also present the user with a % or ppm concentration. 

Does the TIG Electromagnetic Emissions Interfere with the Oxygen Analyzers?

The welding process such as TIG, switches high current and voltage that produces a large dose of electromagnetic interference (EMI) and radiation that interferes with electronics, including the oxygen analyzer itself. Ensure you have a welding oxygen analyzer that has been designed to take this extra EMI into consideration in its design, like the Forensics Detectors that does not have this problem.

How Is Oxygen Gas Detected?

Oxygen is detected using an O2 sensor. Within the oxygen analyzer, a specific sensor measures the oxygen molecules. The reaction produces an electronic signal that represents the O2 concentration. A small electrochemical oxygen sensor is shown below.

oxygen sensor

How Does an Oxygen Analyzer Work?

An oxygen analyzer for welding works by using a specialized sensor cell to detect O2 concentrations. For electrochemical sensors, the oxygen gas reacts with a working electrode and triggers an electrochemical redox reaction. A current is generated proportional to oxygen levels that is converted to a quantitative concentration (related via a calibration curve). For more extensive information, see here.

What Is the Difference Between Electrochemical and Zirconia Oxygen Sensors?

O2 Sensor Technology

Working Principle

Pros

Cons

Electrochemical 

Cells (100 ppm)

The gas reacts with a working electrode, triggering an electrochemical redox reaction. A current is generated proportional to oxygen levels.
  • Small & cheap
  • Easy to integrate with electronics
  • Immediate ON
  • Limited life from 24 to 36 months
  • Influenced by temperature and humidity
  • Limited to 100 ppm.

Zirconia 

Sensors (< 100 ppm)

Zirconia allows  oxygen ions to travel, generating an electrochemical voltage when exposed to gases at different concentrations.
  • Very accurate (sensitive down to 1 ppm)
  • Large detection range
  • Expensive
  • Requires heating and power

What Are Safe Oxygen Levels?

When welding, low oxygen levels are desired in the confined workspace, such as a tube or gas chamber. With that being said, it is important to know that inert gas leaks and depleted O2 levels in your breathing environment can be dangerous.

Various government agencies have recommended oxygen gas limits. Some examples are shown in the table below.

Agency

Recommendation / Requirement

Occupational Safety and Health (OSHA)

Air is considered oxygen-deficient below 19.5%

National Institute for Occupational Safety and Health (NIOSH)

Air is considered oxygen-deficient below 19.5%

American Conference of Governmental Industrial Hygienists (ACGIH)
<18% is minimum partial pressure without the need for respiratory protection at normal atmospheric pressure

    How Can I Test My Oxygen Analyzer?

    The best way to test your oxygen detector is to expose it to an inert gas, such as argon or nitrogen. Since air has 20.9% O2, bump testing it to pure nitrogen or reduced oxygen levels is a good check. 

    What Will Happen If I Breathe onto My Oxygen Analyzer?

    If you breathe onto your oxygen analyzer, the O2 reading will quickly decrease as breath exhalation has depleted oxygen levels of about 17%. 

    What Is the Best Oxygen Analyzer for Welding?

    There are many oxygen analyzers for welding on the market. The reputable brands include the following:


      How Do I Choose an Oxygen Analyzer for Welding?

      To select the best oxygen analyzer for welding, make sure to ask these questions: 

      • Does the oxygen analyzer have a pump? Avoid using handheld aspirators because they create variable pressure (pulses) and affect sensor readings. Continuous, electronic micro pumps are much more desirable in an analyzer.
      • How low do you need to detect O2? Depending on your weld application and the metals being used, 100 ppm may suffice. In this case, an oxygen analyzer with 0.01% (100 ppm) resolution and electrochemical sensors will work fine. If your welding application requires very low O2 levels (down to 10 ppm or even 1 ppm), you will need a 1 ppm oxygen analyzer. For these extremely low concentration readings, you will need an analyzer with zirconia sensors.
      • What accessories do I need? Typically, an oxygen analyzer comes with tubing, filters, carry case, and stainless steel probes.
      • Budget? Oxygen analyzers for welding range from $500 to $5000. Typically, electrochemical sensors sensitive to 100 ppm can be purchased for less than $500. Zirconia based sensors (1 ppm) are sold for over $3000.
      • Calibration certificate? Ensure the unit is calibrated with National Institute of Standards and Technology (NIST) traceable sources to ensure the highest level of accuracy. Ensure the calibration certificate mentions calibration location, standard, and all technical details, including calibration date.

          How Long Do Oxygen Analyzers Last?

          O2 analyzers with electrochemical sensor cells last from 24 to 36 months. Zirconia oxygen sensors last much longer but are more expensive.

            What Is Oxygen Analyzer Bump Testing?

            • Bump testing is a procedure when one exposes the oxygen analyzer to a small amount of “blast” target gas to ensure the detector operates as expected. 
            • The function of this test is to verify proper operation and build user confidence, particularly in hazardous applications.
            • It is recommended to bump test when first purchased, followed by weekly tests. This is especially important in LIFE-THREATENING and / or DANGEROUS applications to verify detector operation. See video explanation here
            • For oxygen analyzers, we recommend bump testing with pure argon or nitrogen gas.

            How Do I Take Care of My Oxygen Analyzer?

            • Store your oxygen analyzer at normal room temperature.
            • Store it away from electromagnetic or magnetic sources, such as phones or electronic equipment.
            • Store it in a clean environment with no dust or particles. If it comes with a case, use it for ensured protection.
            • Store it away from any exhaust gas, concentrated vapors, or harsh chemicals that may poison the sensor.
            • Store it in a stable place where there are no vibrations or continuous shaking. 

            How Do I Properly Use an Oxygen Analyzer?

            When operating your oxygen analyzer for welding, there are some essential tips to consider. Be smart and start by reading your product manual.

            Before starting, set up your weld purge system. This is typically an inert purge chamber (glove box) or a pipe purge system arrangement. There are other hardware setups that create a bubble of inert gas around the welding area.

            1. Ensure the oxygen analyzer has been bump tested and validated as operational.
            2. Turn ON and allow the analyzer at least 60 seconds to come to a stable reading (this may take longer for zirconia-based oxygen sensors).
            3. Check all tube connections via the filter and barbs. It is extremely important to ensure there are no vacuum leaks, which will introduce oxygen and elevate the readings.
            4. Place the probe at your sample location.
            5. Ensure the pump is running. You will soon see the O2 values decreasing once the inert gas starts to displace the oxygen. 
            6. Make the necessary flow adjustments to your inert gas to prevent waste while maintaining low oxygen levels.
            7. Once finished, allow the analyzer to draw fresh air.
            8. Allow the analyzer to return to 20.90.
            9. Turn OFF and store the analyzer.

            What Is the Difference Between ppm and % Oxygen?

            The typical scale of concentration for oxygen is %. For low levels, less than 1%, the parts per million scale is used (ppm).

            For welding, the ppm scale is more commonly used since we are most interested in low values to ensure an inert environment. Conversion between ppm and % is easy. Here is a quick oxygen concentration conversion:

            10 ppm = 0.001%

            100 ppm = 0.01%

            1,000 ppm = 0.1%

            Final Words

            Oxygen analyzers are used in welding to confirm an inert environment for best results - just a few 100 ppm difference can dramatically change the weld oxide thickness. An O2 analyzer is a valuable tool for welding, as it continuously operates to confirm low oxygen levels. Oxygen analyzers for welding have decreased in price over the past few years, now retailing for less than $500.

            About The Author

            Dr. Koz is the President of FORENSICS DETECTORS where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters, and gas analyzers. He has been designing, building, manufacturing, and testing toxic gas detection systems for over 20 years.

            gas detector expert

            Every day is a blessing for Dr. Koz. He loves to help customers solve their unique problems. Dr. Koz also loves spending time with his wife and his three children going to the beach, grilling burgers, and having a cold beer. 

            Read more about Forensics Detectors here.

            Email:  drkoz@forensicsdetectors.com
            Phone: +1 424-341-3886


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