During welding, a large amount of harmful components enters the atmosphere. A special hood for welding can completely eliminate them. Ventilation of this type is a complex system, despite the design features, it can be done with your own hands, following the step-by-step instructions. You should first study the available varieties of such systems and the rules for their installation.
The need for ventilation in the room with welding
Welding is classified as harmful due to the release of many hazardous substances, including iron, chromium and manganese oxides, fluorine compounds and silicon dioxide. They are dangerous to human health and harm the environment, so every room where welding is carried out on an ongoing basis, supplemented by hoods.
Ventilation of the welding workshop solves several basic problems:
- elimination of chemical components that pose a threat;
- creation and maintenance of an optimal indoor microclimate taking into account its temperature, humidity and in accordance with the standards of GOST and SNiPa;
- continuous supply of oxygen.
Air exchange in workshops, welding sections and posts should be carried out offline. If the industrial welding room is located in the same building as the others, they do not have combined ventilation. It is also not recommended to design systems with cyclic and reuse of air masses. In the process of work do not use a natural system, since there is no significant heat in this case. Before being fed into the space, the air is brought to the required temperature, taking into account the weather conditions on the street.
In addition to installing hoods, various means are used to protect welders from radiation, including thermal insulation of heating surfaces and shielding. Thermal insulation works are considered the most effective way to reduce the intensity of the rays and prevent possible burns. Special materials and structures, for example, concrete, brick, asbestos and felt, are used to equip workplaces in combination with screens or separately from them.
Types of ventilation systems and arrangement rules
A hood for a welding station, installed according to the rules, can significantly reduce the concentration of hazardous substances in the atmosphere and minimize harm to the environment. The type and capacity of fans, as well as the routing of the ducts, are selected taking into account the number and location of places for welders. Exhaust structures can be placed on the roofs of workshops or near them, while the air intake should not be on the site for the release of gassed medium.
Local
When creating a local type hood, the ventilation of the posts is selected taking into account the size of the elements to be welded and the intensity of work. The amount and composition of the gases formed depends on these nuances. Thanks to a simple scheme and device, the performance of such a system reaches 5.5 thousand m3/hour. During welding and surfacing of large products on tables that are not supplemented with devices, welding aerosols are removed by suction of mobile units with filtration ventilation. For some types of work, it is advisable to use hoods of a lifting-turning type. Their design includes a flexible hose with a diameter of up to 200 mm, mounted on the console and directed to the desired zone.The receiving pipe is placed at a distance of 7-8 meters from the employee.
An exhaust hood required for welding is not installed directly above workstations. In such systems, it is better to mount tables with air suction through the grate.
General exchange
The general-exchange type system includes a blower and an exhaust fan, as well as air ducts equipped with filters and adjustable inlet structures. Such ventilation is designed to provide fresh air to all premises of the workshop and to reduce the content of harmful impurities in the atmosphere. It is worth choosing if more than 200 g / h of electrodes per 1 m3 of the total volume of the room are used in the process of work. Otherwise, the inflows of air masses will be provided naturally.
In winter, outdoor air is supplied to the workshop at a temperature not lower than +18 degrees. General ventilation for the welding station should be supplemented by filtration elements that clean the air before being released into space. The performance of the devices is selected so as to provide 10-fold air exchange. The vertical velocity of the air masses is maintained at a level not lower than 0.1 m / s. This value is sufficient for mixing media and eliminating welding aerosols from areas outside the posts.
Inside enclosed and semi-enclosed spaces
To organize a ventilation system inside a closed or semi-enclosed space, several available schemes are provided. In the workshop, you can create organized air exchange in one tank, where clean air will be supplied from the outside. Further, the air masses are removed mechanically due to the combined action of the inflow and exhaust. The second method involves the removal of contaminated masses near electric welding arcs, there is also a third option, which involves ventilating only the worker’s breathing zone by supplying clean air under the shield.
The most common type of system is the ventilation circuit of the tank using the supply jet, which provides for the installation of flexible hoses and high-pressure fans. The main advantage of this method is the supply of clean and heated air in the cold season from the street. Tanks in such a scheme are located in specially designated places. To determine the volume of air supplied, its speed at the working section should not exceed 0.7-2.0 m / s for manual welding. It is possible to avoid contaminated air entering the workshop by setting the mass supply from the opposite side.
The supplied stream of purified air should go in the direction from the welder to the arc so that harmful substances do not enter the respiratory zone. The volume of air for supply must dissolve the gases and the solid aerosol phase, which are formed during the work of the first worker in the direction of travel.
Welding hoods
Hoods for welding in production are divided into several available varieties. The most popular are devices with a lifting and rotary design. They consist of an air receiver that can be fixed in any position using hinges, as well as a hose connecting the air receiver and the central exhaust system. This design makes it possible to eliminate 85% of substances hazardous to health, since it can be placed close to any welding machine. Hoods help to completely clean the air at a distance of up to 8 meters from the installation site. Users mark such models as “Doe” and “Octopus”.
In second place in demand are local suction pumps, which must be installed at a height of up to 1.5 meters from the welder's place.
The hood above the working welding table can be external or internal, in the second case it is connected to the general ventilation system using special hoses. To ensure proper air circulation, it is better to give preference to the supply and exhaust ventilation, which ensures the flow of air masses at a speed of over 40 m3/hour.
DIY hood installation
According to the rules and requirements for safety standards in large welding rooms with several posts, the ventilation system must be installed by qualified specialists who are able to make accurate calculations. In small workshops, an air exchange system can be created independently according to the drawings, following standard instructions. In this case, the work is divided into two stages. First of all, they put a supply-type exhaust hood using a mixed type of air supply and exhaust in horizontal and vertical mode, the second option is more preferable:
- Near the wall with access to the street, a ventilation chamber is equipped in which a fan is installed, equipped with the functions of filtering, cooling and heating the air.
- A hole is made in the wall through which the fan will draw in fresh air.
- A channel is laid from the ventilation chamber to the ceiling for air supply.
- An additional fan is installed in the attic, equipped with air purifying filters. From it to the roof spend a special pipe that displays the exhaust air masses.
- Two or three holes are made in the ceiling, which lead to the attic fan using ventilation ducts.
When the general air exchange system is ready, you can proceed with the installation of a local line. Ventilation for a welding post of this type is a suction structure from which a channel is laid towards the roof. It is selected taking into account the configuration of the production enterprise for a particular workshop.
A local exhaust hood is able to remove most of the contaminants offline, preventing them from spreading throughout the room. If necessary, mount a mobile suction that moves the hood together with the welding machine.
