Filter bags made of polyester needle felt with antistatic characteristics are used in filtration processes where the filtered medium might be explosive.
The mixture of air and dust in the cycle: attack of the dust on the bag - regeneration of the bag, may create a potentially explosive environment. Particularly vulnerable to this phenomenon are pulse-jet regenerated filters.
After opening an electromagnetic valve, a selected section of filter bags is attacked with a strong air blow to free the filtration surface from excessive accumulation of dust upon it (dust cake).
Explosion-laden dusts can produce an electrical charge (a spark) which can lead to an explosion within the suction chamber during this process.
While detaching, particles having explosive properties can produce an electric charge (spark) which in turn may initiate an explosion inside the filter.
If the bags are made of an antistatic filter media, these charges are safely dissipated to the earthed filter housing.
Dedusting systems in antistatic design should be equipped with antistatic bags and meet the ATEX requirements.