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AWS F3.2:2018 pdf free download
AWS F3.2:2018 pdf free download.Ventilation Guide for Weld Fume.
Most filter systems operate cleaning cycles on- and off-line. The on-line cleaning function takes place when the ventilation system is in operation. The air cleaning system works against the vacuum of the ventilation system. As the compressed air is forced out against the filter, the vacuum is drawing the particulate back to the surface of the filter pleats while the heavy particulate drops into the collection bin. This results in a low cleaning efficiency. The other cleaning state is off-line cleaning. The off-line cleaning function takes place when the ventilation system is idle, or suction is not present. The air cleaning system pulses compressed air out from the clean side of the filter. As the compressed air is forced out through the filter cartridge, the particulate is blown loose and falls into the collection bin. Off-line cleaning is the most efficient cleaning process.
The use of filter cartridges can result in significant energy consumption due to the fan energy required to overcome filter media pressure drop as well as the power required for using compressed air.
6.3 Electrostatic Precipitators. Electrostatic precipitators operate by electrically charging dust and fume particles and collecting the charged particles on oppositely charged collector plates (see Figure 12). Although this type of filtration is no longer commonly used for welding fume, it is effective for small, submicron-sized particles (typically <0.01 microns). Also, the pressure drop through this type of collector is usually the lowest of the available options. In moist and oily environments, electrostatic precipitators will outperform most other types of collectors.
Electrostatic precipitators require routine maintenance based on the ambient air quality, particulate type, and amount and design of equipment and installation. The collection plates must be part of a routine maintenance program to maintain Filtration efficiency and remove collected contaminant. The plates can he cleaned manually, by ultrasonic vibration, or with a water/solution wash. If used to recirculate air, these units are not well suited for collecting high concentrations of dust and fume. Any charged particle that is not captured will be airborne and will be attracted to any object with an opposite charge, such as walls, machines. duct, etc. Electrostatic prccipitators are not recommended for use when metal grinding fines are present. Metal grinding particles may cause a short circuit across the collector plates.
As particulate is collected, filter efficiency is reduced. Filtration efficiency varies from 90%—99.9% on submicron sized particles. Multi-pass systems can also he used to increase the efficiencies and extend maintenance intervals.
6.4 Fabric Collectors. Fabric collectors use harrier-type filters, typically in the form of bags or pockets (see Figure 13). This means the t’ihric and dust collected on it serve as a barrier to trap dust. AWS F3.2:2018 pdf free download.
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