Welding is the most important joining process for the permanent connection of two or more workpieces. No matter which welding method is used, one thing cannot be avoided: welding fumes, fine dust and emissions. But the negative effects of welding fume emissions on employees, equipment and buildings can be prevented. After all, welding fumes are harmful to health and dangerous to humans because they can get into the lungs. This does not only affect the welder himself, but also the neighbouring machine operator on the automated welding machine. In addition, the welding fumes are distributed as so-called diffuse emissions in all work areas. This affects all professionals who are working in the hall.
This summary presents a comprehensive and compact overview of the hazards caused by welding fume emissions. But also how it is possible to ensure safe and legally compliant welding operations.
Our recommendations are based on our decades of activity in the extraction and filtration of welding fumes and the in-hall air cleaning of welding halls.
Some of our recommendations require some lead time. Others can be implemented immediately and directly. All in all, however, all these adjusting elements ensure one thing: more protection for the welding workplace, a potential improvement in welding quality and, last but not least a considerable reduction in energy costs.
CONTENT
The hazards of welding fumes result on the one hand from the different ingredients of the emission mixture, and on the other hand from the fineness of the emission.
Generally speaking, welding fumes are a hazardous substance. Therefore, there is a legal obligation to evaluate and take appropriate measures to protect workers from the hazardous substance.
Depending on the welding process, the welding material and the welding consumables, different types of welding fumes are produced. They differ greatly in their characteristics. That is why we categorise welding fumes according to their effect on humans: we distinguish between respiratory, toxic and carcinogenic welding fumes.
The welding process and the materials used, in addition to the additives, have a direct influence on the type of welding fumes that are produced.
The following list provides an overview of the most common welding processes and the associated composition of welding fumes.
| Welding process | Welding fume quantitiy | Emission rate [mg/s] |
|---|---|---|
| Gas welding, friction stir welding, TIG, submerged arc welding, resistance spot welding | low | < 1 |
| Laser welding without filler met | low | 1 to 2 |
| MIG/MAG (energy-optimised inert gas welding) | medium | 1 to 4 |
| MIG (general) | medium | 2 to 8 |
| Manual arc welding | high | 2 to 22 |
| MAG (solid wire), lux-cored welding with inert gas, laser welding with filler material | high | 6 to 25 |
| MAG (flux cord wire), flux cored welding without inert gas, oxyacetylene flame cutting, arc sprayingn | very high | > 25 |
Source: DGUV
Over the years, numerous limit values have been imposed for welding. Depending on the country and the type of underlying pollutant, the limit values vary greatly. In particular, the legislator addresses the health risk and differentiates between occupational exposure limits (OEL), technical reference concentrations (TRC) and acceptance or tolerance concentrations.
The following table gives an overview of the most common welding-relevant limit values.
| Limit value | Category | Germany | Austria |
|---|---|---|---|
| General dust limit value | AGW | 1,25 mg/m³(A) | 5 mg/m³ (A) |
| Welding fume | AGW | 1,25 mg/m³ (A) | 5 mg/m³ (A) |
| Chromium(VI) compounds | TRK, Akz., Tol. | 0,001 mg/m³ (R) | 0,01 mg/m³ (R) |
| Cobalt and carcinogenic cobalt compounds (cobalt(II) oxide (CoO)) | TRK, Akz., Tol. | 0,0005 mg/m³ (A) | 0,1 mg/m³ (R) |
| Carcinogenic nickel compounds (nickel(II) oxide (NiO)) | TRK, Akz., Tol. | 0,006 mg/m³ (A) | 0,05 mg/m³ (R) |
| Manganese and its inorganic compounds (for example MnO, Mn3O4) | AGW | 0,02 mg/m³ (A) | 0,05 mg/m³ (A) |
| Nitrogen(II) oxide (NO) | AGW | 0,5 ppm 0,95 mg/m³ |
0,5 ppm 0,96 mg/m³ |
| Fluorides (sodium fluoride (NaF), calcium fluoride (CaF2), sodium calcium fluoride (NaCaF3)) | AGW | 1 mg/m³ (R) | 2,5 mg/m³ (R) |
| Carbon monoxide | AGW | 30 ppm 35 mg/m³ |
20 ppm 23 mg/m³ |
R ... respiratory fraction
A... alveolar fraction
For welding work on metallic materials, the employer is obliged to prepare a risk assessment. It must be carried out before the welding work is started. The results of the analysis must be assessed and documented. This also includes suitable protective measures to avoid or reduce the risk from the welding fumes.
The following order of priority must be used in the assessment:
Ventilation measures are usually unavoidable during welding. They ensure that welding fumes and fine dust are captured, removed and filtered. In order for this to be done as efficiently as possible, a large number of influencing factors need to be assessed. These include the welding process, the materials welded, the type of workplace, the size of the workpiece and the manufacturing infrastructure. As a result, the solutions are as individual as the requirements themselves.
One way of classifying the available solutions is to group them according to their proximity to the emission source, i.e. the welding itself:
With torch extraction or gun extraction, the welding fume emissions are captured and extracted directly at the welding torch. Extraction nozzles are installed on the welding torch for this purpose, to which an extraction hose is connected. It is combined with the hose assembly of the welding machine. Either a filter unit is installed at the end of the extraction hose or the extraction hose leads to a central filter unit via high vacuum piping. Manufacturers of welding torches often offer integrated extraction solutions for their products. Existing units can be retrofitted with collection kits.
With welding shield extraction, the welding fume emissions are collected directly with a shield and extracted. An extraction hose is once again connected to the welding shield. Either a filter unit is installed at the end of the extraction hose or the extraction hose leads to a central filter unit via high vacuum piping. The importance of welding shield extraction has decreased significantly in recent years.
This is mainly due to the new types of welding shield, which are no longer hand-held but worn directly on the head and actively adapt to the welding process and the prevailing brightness.
Welding suction arms are still widely used for collection and extraction during welding. The welding fume emissions are collected by positioning a suction arm as close as possible to the emission source.
A suction arm normally consists of suction pipes or suction hoses, articulated or swivel joints for correct positioning and a suction funnel. The suction funnel ensures an even distribution of the suction effect and ideally protects against the penetration of foreign bodies. Optional integrated lighting or various switches provide improved comfort.
Typical suction arms cover a working area with a radius of one to four metres. With a corresponding extension, working radii of up to eight metres are possible. The diameter of the suction arms for welding applications is usually 160 millimetres.
Welding tables are work tables on which the workpiece is placed and processed. They capture the welding fumes released via integrated table extraction systems. As standard, they are equipped with a downward extraction device (table extraction); as an option, the welding tables can also be equipped with a rear wall extraction system or a side wall extraction system.
As a rule, extraction tables also have a drawer in which coarse particles are collected. Depending on requirements, a wide range of options are available, such as wooden or plastic support grids, height adjustability or lighting.
Typical welding tables cover a working range of one to three metres and have a working depth of around 0.7 metres. The working height of the welding tables can be optimally adapted to the requirements..
Suction walls ensure that welding fumes are captured over a wide area.
For this purpose, the workpiece is placed in front of the extraction wall - usually on a work stand. The rear wall ensures a uniform extraction effect over the entire wall surface.
Typical suction walls have a modular design and cover a working area of one to several metres and a height of 0.5 to two metres.
Suction hoods are placed above the welding process. They ensure that the welding fumes and fine dust rising above the welding process due to its thermal properties are captured and extracted. Welding fume suction hoods are usually fitted with curtains. They serve to shield the welding process and encapsulate the welding fumes so that the emissions can rise unhindered and are not diverted by cross air flows. The optimum design is an edge strip extraction system. Extraction openings are positioned all round the extraction bonnet. They ensure uniform capture over the entire bonnet surface and prevent foreign objects and sparks from being sucked in.
Suction hoods are often used for robot welding. The hoods are placed either above the robot or directly on the robot. Even solutions with suction hoods travelling with the robot can be implemented.
Typical extraction bonnets have a modular design and cover an extraction area of 1 to several square metres.
Extraction booths are often used to remove welding fumes from production halls. The welding processes are carried out in a separate enclosure. Workpieces are transported manually or using lifting equipment into the extraction booth, where the welding work is carried out. In many cases, other activities such as grinding work are also carried out in the extraction booths in addition to welding. Extraction booths are suitable for separating individual work processes such as aluminium welding, mild steel welding or welding of high-alloy steels.
Inside the welding fume extraction booths, welding fume emissions are usually captured using the aforementioned systems such as extraction arms, welding tables and extraction walls. In addition to welding fume extraction, the booths usually have their own ventilation and extraction system.
A modern in-hall air cleaning system in the welding hall
The extraction, filter and ventilation technology and the air performance required for this are individually adapted to the respective requirements.
Central welding fume filters are stationary filter units. They cover several welding workstations and are designed for continuous operation. Today, filtering separators that work according to the surface filtration principle are used almost exclusively for the filtration of welding fumes. Here, the fumes and fine dust emissions are retained on the filter surface without penetrating the filter material. The surface of the filter elements is continuously cleaned. To do so, the emissions are trussed off the surface by means of compressed air and collected in a dust collection container.
Due to the extreme fineness - the majority of welding fume particles are smaller than 1 micrometre - the cleaning effect of such welding fume filters is low. The fineness of the particles and the process heat mean that welding fumes are airborne dusts. They do not fall to the ground, but remain in the air. This leads to the welding fumes occupying more and more of the filter surface. The result is a higher air resistance and a falling suction performance of the filters.
Kappa has therefore developed the so-called Sequence Dedusting®. This is a cleaning technology that ensures that the individual filter areas are cleaned sequentially. This creates a downward flow in the filter, which captures the suspended dust and transports it to the dust collection container. This results in a consistently high suction performance and a constantly low air resistance. The result is 30% improved filter performance and a reduction in energy consumption of up to 35% . The Kappa Sequence Dedusting® cleaning technology is used in the Kappa Mykron® fine dust filter and energy-saving filter. It therefore represents one of the most modern and future-proof welding fume filter systems.
Welding fumes are - as described above - not homogeneous emissions, but a heterogeneous mixture of fumes, dusts, gases, and vapours that are generated during welding and emitted into the ambient air. This is something to consider when we talk about welding fume filters. They represent filter systems for the filtration of fumes and fine dust. Gaseous emissions are not filtered. This is another reason why modern in-hall air cleaning systems with fresh air supply to the work area are the right choice. They ensure optimum air exchange and thus clean fresh air at the welding workplaces.
"Thanks to our new in-hall air cleaning system, the air quality in the welding shop is now very good. Despite the low outside temperatures in winter, we hardly had to heat up. Before, we lost the waste heat via the roof, now we can use it."
Johann Struc, head of work organization
"Wasserbauer is a company where the closeness to nature already results from the product. That's why we are happy to integrate another building block into our production with our air concept, which not only counteracts the rising energy prices, but also makes a contribution to the environmental protection."
Franz Wasserbauer, Managing Director
"The air quality in the steel construction is very good. This is also confirmed by our employees. Last winter we hardly had to heat up because we were able to cover our heat requirements from heat recovery."
Thomas Heenen, safety officer
"With the new extension to our production hall, we are already gearing up our company to meet the requirements of the future. Just as we rely on the most advanced technology for our machinery, we also do so consistently for structural measures, such as the air concept. A welding technician told me some days ago during an inspection, that this is the clean and bright working-environment, which makes the difference at welding. In this place he would like to work."
Johann Kasper, CEO
Filter towers are filter units that freely draw in hall air, filter it and release it back into the hall. Authorities assess filter towers very differently. Thus, filter towers are not classified by the authorities as a ventilation measure. Since they freely draw in the hall air, they are also not an air filtration system. Therefore, for regulatory purposes, filter towers do not constitute a permissible protective measure. However, it may very well be accepted by the competent authority in individual cases in the course of an individual assessment.
Do you have questions about the effect of individual protective measures? We are happy to assist you.
The current manganese limit value (A-dust) is very low, especially in Germany. This often leads to the permissible workplace limits being exceeded. Individual measures are often not sufficient here. In these cases, a mix of measures consisting of organisational and technical protective measures must be defined.
We are happy to support you in this and develop a solution concept together with you that is tailored to your needs.
Welding fumes are often a fire hazard. Also because partially oiled or coated components are welded. This leads to a combustible mixture in the extraction system. If sparks also get into the extraction system during welding, a fire can develop. It often starts as a flash fire in the pipework and spreads to the filter. Therefore, the possibility of a fire hazard must be taken into account as early as the system planning stage and, based on this, a fire protection concept with appropriate protective measures must be implemented. They range from organisational measures to technical measures such as the installation of pre-separators or fire extinguishing systems.
We are happy to support you in this and develop a solution concept together with you that is tailored to your needs.
As a rule, the welding fumes are not explosive and can therefore be removed with traditional extraction technology. In certain cases, welding fumes can still be explosive. An investigation of the safety parameters for the respective application is therefore strongly recommended.
We are happy to support you in this and develop a solution concept together with you that is tailored to your needs.
Recirculated air-operation means that air that has already been filtered is returned to the work area. In order to avoid additional hazards for the employees, legislators regulate the possibilities for air recirculation. The corresponding standards vary from country to country. In general, the possibility of recirculated air-operation depends on the separation efficiency. In many cases, air recirculation is permitted if the purified air falls below 1/3 of the permissible workplace limit value. The situation is different for air recirculation when handling carcinogenic substances..
We are happy to support you in this and develop a solution concept together with you that is tailored to your needs.
