Measuring PPM Oxygen for Welding Applications
Not all welding applications require inert shielding gas. However when it does, use of an accurate and reliable trace oxygen analyzer is an essential tool. TIG (Tungsten Inert Gas) welding of titanium requires the use of inert shielding gas, typically either high purity argon or a mix of argon/helium containing under 100 parts per million (PPM) of oxygen. Air contains 209,000 PPM of oxygen, so in order to create an acceptable atmosphere within the weld box (avoiding leakage of air into the box), a constant purge of inert shielding gas is normally applied. To help ensure oxygen levels within the weld box are at acceptable levels, a trace oxygen analyzer becomes a critical tool. Excessive levels of oxygen often lead to poor quality welds. The following video helps to describe the necessity of measuring trace oxygen in inert shielding gas.
Caution should be exercised when selecting an oxygen analyzer for welding applications. When PPM oxygen measurements are required, avoid analyzers that only measure percent oxygen levels. Most of these types of analyzers use electrochemical sensors designed specifically for percent oxygen measurements, not parts per million. In such cases, welders often interpret a reading of “0” oxygen as acceptable when in fact it may not be so. Keeping in mind that the percent equivalent of 100 PPM of oxygen is 0.01%, oxygen readings from percent analyzers of 0.2%, 0.1% or even “0”% often indicate the analyzer has exceeded its low measurement limit. Essentially, it may represent a “false low oxygen” reading, the worst kind for critical welding. This problem can be eliminated by choosing the correct type of welding purge monitor, specifically one designed to measure PPM oxygen concentrations.
OXYGEN ANALYZERS FOR WELDING
Alpha Omega Instruments offers two oxygen analyzers that are ideal for welding requirements, the Series 3000 Trace Oxygen Analyzer and Series 3520 Portable Trace Oxygen Analyzer. When equipped with an on‐board sample pump, the inert shielding gas is drawn from the weld box to the analyzer where trace oxygen concentrations are measured continuously. With the high cost of manufactured gases, Alpha Omega Instruments’ trace oxygen analyzers are also used to help ensure that argon isn’t being wasted. If the weld box environment requires oxygen levels of approximately 100 PPM, excessive purging of inert shielding gas well below 100 PPM will result in a significant waste of argon and render no additional value to the welding process itself. Contact Alpha Omega Instruments for additional information on this subject.