Practical tips for welding: How to weld correctly with fume extraction torches

Posted by Jörg Reips on Feb 5, 2021 9:12:36 AM

When welding metals, there are a number of emissions which, on the one hand, cause the legally prescribed MAK values (“maximale Arbeitsplatz-Konzentration”: maximum workplace concentration) to rise above the permissible threshold value and, due to toxic and / or disease-causing ingredients, represent a health risk for the personnel in the processing area. This fact obliges companies in the welding industry in particular to ensure effective air filtering and ventilation in the areas concerned. Because not only the welder himself is affected by the harmful emissions, but also the rest of the staff in the production hall, who are exposed to the welding fumes.

In addition to a large number of stationary fume extraction systems, the torch-integrated fume extraction (fume extraction torches) is one of the most effective and mobile methods that can be used. Welding with fume extraction torches is definitely a challenge when it comes to the handling.

So how can you weld correctly with fume extraction torches? What do you need to pay attention to?

Basically, the additional work involved in installations (extraction device and extraction hose) means that the device and the extraction hose (corrugated hose) must be in a safe location. Loops and constrictions should be avoided as these can noticeably reduce the extraction efficiency.

We have put together three practical application tips for better fume extraction, weld seam quality and handling of the welding torch:

1. Choose the right suction nozzle for better accessibility to the component.

Regardless of whether you have been working with fume extraction torches for a long time or are just thinking about converting to extraction torches, the first question that arises is: Is the access to the component guaranteed with my torch?

RAB_GRIP_HE_501

There are different fume extraction torches available in air cooled and liquid cooled versions and in different ampere ranges. First, look for an extraction torch that comes closest to the performance requirements of your standard torch for your welding task.

Due to the way the fume extraction torch works, it usually has a larger outer contour, i.e. the torch has a larger diameter, is thicker on the torch neck due to the integrated suction tube and an additional suction nozzle is attached to the gas nozzle. All of this is necessary to remove welding fumes whilst working.

With certain component geometries, this can lead to poor accessibility and make welding more difficult.

The solution here are fume extraction torches with different wear part designs, such as an adapted suction nozzle geometry.

Ausruestvarianten_mit_Nummern

(1) standard extraction nozzle (2) better accessibility; slightly reduced fume extraction due to the greater distance to the point of origin of the welding fumes (3) increased extraction performance due to the smaller distance of the extraction nozzle to the point of origin of the welding fumes and good accessibility to the component due to slim standard gas nozzle

The rule is always: Try what suits the welding task best!

For example, you can switch to a version with a screwed gas nozzle, which, thanks to its slim shape, ensures better accessibility to the component. However, this slightly reduces the suction power.

If a particularly high suction power is required because, for example, a lot of residues and welding fumes are generated, e.g. when welding over paint or welding galvanized metal sheet, you can fall back on torches with a particularly strong suction power, such as our RAB GRIP HE fume extraction torch. It has a special suction nozzle geometry and enlarged flow diameters, which reliably capture the welding fumes even in difficult working positions and still ensure good accessibility to the component in the front area.

It is best to always test the torch on your component directly on site and ask for advice in order to make the best possible decision that allows good accessibility, high extraction performance and consistent welding seam quality.

2. Check the position of the welding torch and the workpiece to ensure efficient extraction at the arc.

Welding does not always take place in the optimum welding position. Welding often takes place in forced positions, i.e. physically unfavorable positions for the welder, such as overhead welding. In this case, the welder does not have the ideal position in relation to his workpiece. This is not just more physically demanding. It also results in a problem with welding fume extraction, since the column of fumes - the welding emissions - always rises upward during welding and fans out there.

This is because welding creates heat and warm air always rises to the top.

If you want to weld properly with your extraction torch, produce good welding seams and capture the welding smoke efficiently, the torch should always be held into the column of smoke, i.e. into the rising air. In the case of a flat position (welding position PA) and slightly piercing welding, this is ideal, as the torch is moved along the seam in front of you and thus pushed directly into the column of smoke. In this way, 95% of the fumes and even beyond can be captured. It looks just as good in the torch positions neutral and slightly dragging in PA.

Depending on the welding position, the welding fumes can also be drawn directly away from the torch and only part of the harmful welding fumes can be captured.

Therefore, if possible, always change the welding torch position to a position in which the suction nozzle is in the direction of the emissions that are drawn upward, as far as this is possible or permissible for manufacturing reasons, and adjust the position of the welding fixture if necessary.

The figure below shows the influence of different angles of attack of the extraction torch to the workpiece as well as the welding direction on the fume extraction performance:

Rauchgasabsaugung_SW

 

3. Check and regulate the optimum suction power on the welding torch.

During welding, shielding gas is used to displace the atmospheric air and thus protect the welding seam from oxidation by the oxygen and other gases in the ambient air. The shielding gas bell is placed around the welding process and must not be extracted when welding fumes are captured. Extracting the shielding gas can cause pores or oxidation on the welding seams - a quality problem!

Maximum welding fume extraction is therefore often not effective, because the quality of the welding seams must be guaranteed at all times. If the welding fumes are completely removed, but a large part of the shielding gas is also extracted, the welding seams can oxidize and turn black, and pores are formed. It is therefore important to check and regulate the suction power on the welding torch itself.

If the shielding gas bell is affected by the fume extraction during the welding process, reduce the negative pressure with the regulator on the welding torch and/or on the extraction device. Many fume extraction torches have a module in the handle called an „air supply slider“ that can be used to regulate the extraction rate by reducing the negative pressure. In addition, there are also extraction devices where the suction power can be varied directly on the device. However, reacting quickly by regulating the supply air at the extraction torch is the best and most flexible method!

 

RAB_GRIP_HE_Schieberegler

The aim is always a good mixture of effective fume extraction - and thus protection of the welder from damage to his health - and at the same time good welding results due to sufficient shielding gas coverage during the welding process.

Again, if the welding results are not good, the other application tips should also be checked and, if necessary, a change should be made to a different gas nozzle or a different type of torch where the extraction is located further back and thus has less influence on the arc because the process is more visible.

Do you have any further questions on how to weld properly with extraction torches? We will be happy to help you!

You can also find everything about fume extraction in our eBook:

The complete guide to fume extraction - Download free eBook now!

 

Topics: Fume Extraction, MIG Guns & Torches