Weld Purge Monitor
Catrin Muzquiz
Weld purge monitors are most often used to verify low oxygen levels when welding pipe or a hollow metal design where precise welds are critical. For example, they are used in the construction of food processing equipment, power plants, aircraft submarines, or anywhere a defective weld could have catastrophic or deadly results.
Weld purging is the displacement of oxygen from the backside of a weld. Stainless steel and some other metals are sensitive to the presence oxygen during TIG welding. The oxygen chemically combines with the hot metal as it is being joined and weakens the bond. Purging solves this problem by displacing the oxygen with an inert gas. It is most commonly used when welding pipe or other structural metal objects.
In other cases, when welding a long stretch of stainless steel pipe the welder may start welding before the purge is complete. Depending on the length of the pipe, it may take hours to completely fill a pipe with argon gas. Even if the welder uses weld purge paper or inflatable stoppers to create a purge dam (not always allowed) they still cannot guarantee the oxygen purge was complete.
The issue of improperly back-purged welds becomes compounded when a TIG welding job is sub-contracted. Unless the contractor requires x-ray inspection of every weld, only a trace oxygen analyzer with data logging can verify the complete purging of oxygen before welding is started.
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.
Another factor to keep in mind during welding is the weld plume. The dimension of the plumes are important. The plume needs to be large enough to cover the entire area of the weld, and be at or very near the eutectic point where the metal loses its hardness and becomes receptive to oxidation and other undesirable processes.
The probe nature of the TecWeld allows the dimension of the plume to be measured. Too much flow will be indicated by an oversize plume, which can in turn cause inappropriate cooling at the weld point and cause the weld to become brittle. Brittleness can occur when the heavy element of the filler metal and the base alloy are joined and cooled at different times. This is sometimes referred to as the passivation of the weld, because it does not allow the stratification of the weld component from uncontrolled atmospheric or thermal conditions.
Oxidation is a form of metal corrosion that forms during the welding process. Oxidation prevents a good weld from forming because too much oxygen enters the area where the weld is being created. Electrons move from the metal that is being welded to the oxygen molecules during the process. Too much oxygen in the welding environment leads to corrosion, which then in turns causes a weak and unreliable weld. Corrosion can be dangerous if it affects an integral inner structure such as buildings and bridges, pipes, and ships. A weakened infrastructure can put lives at risk, so reduce oxidation in welding is essential for safety.
An example of oxidation in welding is carbide precipitation, also called sugaring, which occurs on stainless steel. Sugaring is the result of the back side of the weld being exposed to oxygen in the atmosphere during the welding process. Even though the weld looks good from the front, it is weak at the backside and over time can display stress cracks. The best way to avoid sugaring is to purge the back of the weld with a shielding gas such as argon. This is especially important when welding pipe where you cannot view the backside of your weld.
An example of a trace oxygen analyzer for welding is the TecWeld TS-300 Weld Purge Monitor. This oxygen sensor provides accurate measurements down to 0% oxygen for back purging of oxygen during welding. Learn more about the TecWeld Portable Weld Purge Monitor here.
Inert gas welding requires the exclusion of oxygen from the weld zone during the welding process. Prior to the welding process, the residual oxygen concentration must be reduced to a required minimum. The Handy Purge 100 is specifically designed to indicate oxygen concentration up to 0.01% and to exactly measure oxygen concentration up to 0.1%. Within this range, it is absolutely safe to weld and produce an oxygen-free weld seam (exceptions include special metals such as titanium, zirconium, etc.).
The Handy Purge 100 can be used both for continuous monitoring during the welding process and for taking samples. Routine inspections for quality control are extremely simplified using this device. The analyser works with all purge systems and argon welding systems. It is small, easy to handle and has a rugged enclosure.
Internationally renowned for its highly advanced features and low-cost, this oxygen weld monitor with an internal pump accurately measures down to 0.01% (100 ppm) resolution, making it ideal for purging and other welding applications.
The PRO OX-100 comes equipped with many advanced features such as its data logging capabilities, which allow operators to create permanent records of real time data (at 15 second intervals) and export up to 50 data points to Microsoft Excel and plain text format.
The PRO OX-100 also offers a built-in, programmable multi-language feature with on-screen instructions that are available in English, Spanish, German, and Portuguese. Together with different voltage and frequency specifications and compatibilities, the PRO OX-100 is the most universal oxygen weld monitor available on the global market today.
The PRO OX-100 logs data that can be transferred to a computer via USB cable. Conversion software enables easy capture and export of 50 data points to Microsoft Excel and Plain text format. Data is recorded in 15 second intervals in CONTINUOUS mode or as needed in SPOT mode.
Self Calibrating Model:
Calibration can be performed on a weekly basis. There are no other specific recommendations regarding maintenance besides general care of the unit such as cleaning, proper storage, etc.
Point Calibration Model:
1. As the unit undergoes 2 point calibration, it is not necessary to recalibrate unless the SENSOR needs replacement. A CAL ERR will indicate a need for replacement.
2. Replace sensor and follow instructions in section 2.1.7 of the manual pages 19-21.
Self Calibrating Model:
If a unit is used very frequently (daily) it should be calibrated once a week. If it is not used frequently, it should be calibrated once every three weeks.
2 Point Calibration Model:
As the unit undergoes 2 point calibration, it is not necessary to recalibrate unless the SENSOR needs replacement. A CAL ERR will indicate a need for replacement.
The Pro OX-100 is battery operated, but can also be operated through a standalone power supply. For specifications on use, refer to section 2.1.1 of the manual. With a full-charge, the battery can supply continuous power for up to two (2) hours.
When using The Pro OX-100 Oxygen Monitor for MORE than two (2) continuous hours be sure to turn the power switch to the OFF position. If the battery is installed, remove it from the housing. Then connect the standalone power supply/charger cable to the port. After this step, connect the power supply/charger plug into the nearest working outlet (110V for US type/220V for EU type). Then simply turn the power switch to the ON position. The Pro OX-100 is capable of operating indefinitely with a standalone power supply.
CAUTION: ALWAYS REMOVE THE BATTERY IF USING THE MONITOR FOR MORE THAN 2 CONTINUOUS HOURS. FAILURE TO DO SO CAN OVERHEAT THE BATTERY AND SERIOUSLY DAMAGE THE PRODUCT AS WELL AS VOID THE WARRANTY.
If the alarm does not sound or flash, the alarm is either disabled or damaged. In order to fix this, refer to the manual Section 2.1.3. and follow the instructions. If the issue still persists, the unit must be sent to Aquasol Corporation for repair. Contact customer service for an RGA authorization.
If the alarm light does not blink, even though the sound goes off, the light indicator is damaged. To fix this, the unit must be sent to Aquasol Corporation for repair. Contact customer service for an RGA authorization.
The Handy Purge Pro 5 is the ultimate hand-held Oxygen monitor, measuring the level of oxygen in the designated atmosphere down to 5ppm (parts per million)!!! The new Handy Purge Pro 5 Weld Purge Monitor is essential for reading oxygen levels for titanium welding. The interface option enables the Handy Purge Pro 5 to be connected (via a cable or Bluetooth dongle) to a PC and printer to record the readings. A rechargeable battery pack and multi range power plug are standard features of the Handy Purge Pro 5, and its light weight and ergonomic shape make it the ideal portable instrument for all orbital welding applications. The unit incorporates an internal pump and is designed for measuring rest oxygen in inert gases such as argon. This unit can be used up to 4 hours before recharging is necessary.
Details: You don't need to break the bank for a quality 0.01% (100 ppm) resolution oxygen detector for O2 depletion analysis for TIG or MIG welding. The FORENSICS oxygen analyzer is an excellent option for those that would like to confirm low oxygen content in inert environments. The device accurately monitors oxygen levels while using inert gas to purge stainless steel, titanium, and other reactive metals.
The oxygen gas analyzer measures the oxygen content in the weld chamber down to 0.01% (100 ppm). Based on our industrial analyzer platform, the built-in pump is easy to use, light, and very portable. Simply insert the probe into the tubing with the filter and onto the analyzer barb. The user has full pump control, withdrawing small or large quantities of air with the built-in pump. The analyzer has a color screen, large digits, and on-screen real-time graphing. The detector is built using an advanced electrochemical oxygen sensor. The internal 32-bit microprocessor allows for user calibration, ON/OFF flow, and test control.
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