Welding is the most important joining process for the permanent connection of two or more workpieces. With the help of warmth and pressure a unsolvable connection between materials emerges. Sometimes with the aid of additives.
Welding fumes are not homogeneous emissions, but a heterogeneous mixture of fumes, dusts, gases and vapours that are generated during welding and emitted into the ambient air.
- Fumes are understood to be a mixture of different fine and solid substances. Fumes are produced by the condensation of inorganic substances from the vapour phase, chemical reactions (e.g. oxidation) and incomplete combustion of organic material due to welding consumables, coatings and impurities. For fine dust to be perceived as fumes, it must be present in larger quantities.
- Gaseous emissions and vapours are produced by the thermal conversion process of fuel gases, air, coating materials and impurities.
- Ozone, for example, is created by the electric arc from the oxygen in the air.
- Carbon monoxide is formed by incomplete combustion of fuel gases with inert gases.
- Nitrogen oxides are formed by thermal processes from the nitrogen and oxygen in the air.
- Phosgene, aldehydes and decomposition products are generated by working with coatings, oils or degreasing agents.
Danger to the workforce –
that's why welding fumes are dangerous
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.
- Respiratory and lung-damaging welding fumes
This welding fume is mostly produced during the processing of metallic materials without alloys. For example, when welding iron, steel, magnesium or aluminium. In these processes, the welding fumes released contain metal oxides such as iron oxide or aluminium oxide. The hazard results from the amount of fumes that are released and the size of their fine dust particles. The exposure leads to impairment of the respiratory tract. The consequences are respiratory diseases such as bronchitis, narrowing of the airways, siderosis (iron storage disease) or fibrogenic reactions (connective tissue proliferation).
- Toxic welding fumes
Toxic welding fumes are said to occur when poisoning occurs due to exceeding a certain dose. Gases such as carbon monoxide, nitrogen oxides, ozone, but also oxides of copper, lead or zinc are classified as toxic. The toxic effect depends essentially on the concentration - a low concentration can cause mild poisoning or health disorders, a high concentration can be life-threatening.
- Carcinogenic or cancer-causing welding fumes
For carcinogenic and cancerogenic substances, there is no threshold value above which damage occurs. Even small amounts are thought to pose a serious risk. Special regulations therefore apply to welding fumes in this category. Carcinogenic substances include, for example, chromium(VI) compounds, nickel oxides or cobalt oxide. They arise in particular when welding alloyed steels (e.g. steel containing chromium and nickel).
of the welding
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.
Regulations and legal provisions
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.
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:
Substitution is the replacement of the welding process with another, lower-emission process. If it is possible to use different welding processes, the one that releases the least amount of welding fumes should be selected (see table above on welding processes and welding fumes).
- Ventilation protection measures
This includes technical protection measures such as the extraction and filtration of welding fume emissions by means of extraction and filter systems or the provision of ventilation solutions.
- Organisational protective measures
Organisational protective measures include instruction of workers and general occupational health care.
- Individual protective measures
Individual protective measures include, for example, personal protective equipment such as the wearing of respiratory protection or the use of ventilated welding helmets.
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.
on the Kappa suction arms
Welding tables are work tables on which the workpiece is placed and processed. They ensure the collection of the released welding fumes via integrated table suction. They are equipped with a downward suction device (table suction) as standard. Optionally, the welding tables can also be equipped with a rear wall extraction or a side wall extraction. Usually, extraction tables also have a drawer in which coarse particles are collected. Depending on the requirements, a wide variety of options are available, such as support frames made of wood or plastic, 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. Ideally, the working height of the welding tables can be adapted to the requirements.
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Kappa welding tables
Extraction walls ensure that welding fumes are collected across a wide area. The workpiece is placed in front of the extraction wall - usually on a work stand. The rear wall ensures an even extraction effect over the entire wall surface.
Typical extraction walls have a modular design and cover a working range 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 are collected and removed due to thermal convection. Typically, welding fume suction hoods are equipped with curtains. They serve to screen the welding process and as an envelope for the welding fumes so that the emissions can rise unhindered and are not deflected by cross currents. The optimum design is an edge trim suction unit. Here, suction openings are placed all around the suction hood. They ensure uniform collection over the entire hood surface and protect the collection of foreign bodies and sparks.
Suction hoods are often used in robot welding. Here, the suction hoods are placed either above the robot or directly on the robot. Even solutions with suction hoods that travel with the robot can be implemented.
Typical suction hoods have a modular design and cover a suction area of one to several square metres.
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Kappa suction hoods
Suction cabs are often used for the removal of welding fumes from production halls. Here, the welding processes are carried out in a separate enclosure. The workpieces are transported manually or by means of lifting equipment to the suction cab where the welding work is carried out. In many cases, other activities such as grinding are also carried out in the suction cab in addition to welding. Suction cabs are suitable for separating individual work processes, such as aluminium welding, normal steel welding or the welding of high-alloy steels.
Within the welding suction cabs, welding fume emissions are usually collected via the aforementioned systems, such as suction arms, welding tables and extraction walls. In addition to welding fume extraction, the cabs usually have their own air supply and extraction.
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Kappa suction cabs
WELDING FUME REDUCTION
WITH VENTILATION TECHNOLOGY
IN-HALL AIR CLEANING SYSTEM
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Kappa A.I.R.TM in-hall air cleaning system
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Kappa Mykron® welding fumes filter
"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, Managing Director