How can you make sure that your welding fume extraction equipment is truly effective, and that the welder is safe from fume exposure? A lot of it comes down to the positioning of the extraction hood. Here are some of the most important things to keep in mind when using and positioning a welding fume extraction hood in your workshop.
1. Improper Extraction Hood Positioning Can Leave Welders Exposed to Hazardous Fumes
Welding fumes are hazardous to human health, and must be captured before they reach the welder’s breathing zone. Therefore, the extraction hood always needs to be placed to draw the fumes away from the welder. Whether the hood is positioned in front, to the left, or to the right of the welder, it should ideally be facing him/her.
2. The Extraction Hood Should Not Restrict the Welder’s Working Space, but Must also Not Allow Fumes to Escape
The extraction hood’s proximity to the fume source must not interfere with the welder’s work. That said, the hood must also not be positioned too far from the fume extraction point, as crosswinds may blow the fumes out of the effective capture zone and off to other areas of the workshop. So, what is the ideal distance between the fume source and the extraction hood? The general rule is to have a distance that is equal to the diameter of the extraction arm. For example, a hood with an eight inch extraction arm should be placed about eight inches away from the extraction source. This is generally used with standard cone-shaped hoods.
3. Smart Extraction Hood Design Increases Welding Fume Extraction Efficiency
Many fume extraction hoods are completely round – either circular or oval. Simply put, this design allows more air to be drawn from behind the hood, resulting in a lower extraction volume in front of it. The hoods of Nederman’s NEX MD and NEX HD fume extraction arms both have flat edges at the bottom of the hood rim. This allows the extraction hood to rest steadily on the welding table, which extends (in fact almost doubles) the hood’s extraction range. Moreover, the flat edge helps focus the airflow into the hood by cutting off the air path underneath it. This results in greater welding fume extraction efficiency. Without this design, the hood would draw in air from all around it, just as it does when it is suspended in air.
4. Fume Extraction Hoods Are Often Misused as General Ventilation Hoods
Welding fume extraction used to be done via a general ventilation hood above the welding workstation. This is an obsolete technique, as it does not prevent the fumes from reaching the welder’s breathing zone. Extraction hoods should not be used as general ventilation, nor should they ever be positioned above the welder.
5. When Can Extraction Arms Be Used for Dust Collection?
Fume extraction arms and their hoods are not vacuum cleaners. They are low vacuum extraction tools, which simply do not have the suction power to extract the heavy particulates that can settle on a surface. However, they can be used in some dust collection applications, such as those involving pouring from one container to another. Processes that eject dust into the air – cutting or grinding, for example – generally require other extraction solutions, such as downdraft dust extraction tables or high vacuum on tool extraction kits.
6. Fume Extraction Hoods Do Not Extract or Remove Shielding Gas
In order for shielding gas to be pulled from the welding torch, the suction power of the hood would have to equal that of a vacuum cleaner. Extraction hoods draw air at high volumes but with a much lower vacuum pressure than a vacuum cleaner or on-torch extraction system. Therefore, they cannot affect shielding gas.
7. Fume Extraction Arm Dimensions Are Important to Consider Prior to Installation
Fume extraction arms need 3-4 feet of clearance, in addition to the mounting height, and can be anywhere between 3 and 16 feet in length. In order for the hood positioning to work smoothly, make sure that you choose extraction arms of a size and length that fit your workshop or welding station.
8. Bending a Fume Extraction Arm Too Much May Reduce its Airflow
If an extraction arm is nearly completely folded onto itself, its airflow will likely become restricted. This will likely add more resistance to the airflow in the system, reducing the hood’s capture ability. This underscores the importance of choosing fume extraction arms of the right size and length.
Nederman is a Clean Air Company, and we are proud to contribute to workplace safety and cleanliness, and a cleaner environment. We design our products to make them easy to use, since we know that is what will make them widely used and appreciated. If you have any questions about our fume extraction products, you are welcome to contact me at firstname.lastname@example.org. You can also find plenty of other articles on the work that we do, here at the Nederman Knowledge Center.