Think You Don’t Need Fume Collection for Resistance Welding? Think Again.

Resistance welding (RW) may not generate the volume of fumes created by gas metal arc or shielded metal arc welding, but capturing what’s produced during this process must still take place.

AWS Publications | February 24, 2022 | Processes
Welding Digest ►  Think You Don’t Need Fume Collection for Resistance Welding? Think Again.

Resistance welding (RW) may not generate the volume of fumes created by gas metal arc or shielded metal arc welding, but capturing what’s produced during this process must still take place.

There are two basic approaches to handling RW emissions. The correct approach depends on the volume of weld fumes produced, the hazards associated with the chemical makeup of the fume, and the proximity of people to fume-creating processes.

Source capture options collect weld fumes close to where they are created so they don’t propagate through the ambient air. Ambient options continually refresh all of the air in a facility to dilute harmful airborne contaminants to a safe level. The options may consist of simple exhaust ventilation and makeup air systems or air filtration options that return clean, filtered air to the facility.

An ambient ventilation system may be adequate for occasional, light spot welding. For high-volume RW, however, it is better to use either a source capture or ambient air filtration system. Air filtration systems offer many benefits. They save energy by returning clean, filtered air to the facility, keeping heated or cooled air inside and reducing pressure on the HVAC system. Plus, they keep welding emissions out of the atmosphere for a more environmentally-friendly solution.

 

Ambient or Source Capture?

For high-production facilities, source capture is usually the best option for resistance welding fume control. A source capture system reduces the energy requirements for weld fume collection by minimizing the volume of air that must be moved to capture the fumes and does a better job of keeping weld fumes out of the breathing zone.

For robotic RW, keeping processes under a hood will facilitate weld fume capture. The hood should be designed to minimize the volume of air that must be collected and enable efficient capture of contaminants. For manual resistance welding of smaller components, use a fume arm, hood, or backdraft table that pulls fumes up and away from the welder’s breathing zone.

For robotic applications that cannot be easily hooded or manual RW of very large weldments, ambient collection of fumes may be the only option. In designing an ambient solution, modeling the airflow through the facility using computational fluid dynamics can help engineers optimize the solution to minimize exposure risks and avoid over- or under-engineering the system.RoboVent 1

When choosing an air quality solution for RW, facilities must decide between source capture and ambient options and whether to use filtration or simply exhaust contaminated air.

 

Other Considerations

Both source capture and ambient filtration solutions require a dust collector. A cartridge-style dust collector is usually used for weld fume collection.

Some things to keep in mind when designing a fume collection system:

-Understand your emissions. Oily particulate created when welding lubricated materials may require special media or continuously pre-coated filters in extreme cases. If emissions contain gases, vapors, or highly toxic metals, after-filters such as an activated carbon after-filter or HEPA may be required.

-Zinc oxide from galvanized metals may be in a gas phase when hot. A longer duct run will allow it to transition back into a solid-state for collection.

-Your dust stream may be combustible. We recommend that all users understand the characteristics of the dust streams. According to NFPA guidelines, it is the user’s responsibility to perform a dust hazard analysis including testing dust streams for explosibility.

-Spark arrestance for your resistance welding extraction system should be included. Sparks generated from resistance welding systems can be large, burn long, and can be thrown far from the point of generation.

RoboVent 2

An industrial dust collector filters contaminated air and collects particulate for safe disposal.

 

Ending Thoughts

If you are concerned about RW fumes in your facility, talk to a qualified air quality engineer about options. An effective ventilation or air filtration system will protect employees and keep your system in compliance with all regulations concerning weld fume emissions.

 

This article was written by Rick Kreczmer (president of RoboVent®, Sterling Heights, Mich.) for the American Welding Society.